research on environmental pollution

Air Pollution

Our overview of indoor and outdoor air pollution.

By Hannah Ritchie and Max Roser

This article was first published in October 2017 and last revised in February 2024.

Air pollution is one of the world's largest health and environmental problems. It develops in two contexts: indoor (household) air pollution and outdoor air pollution.

In this topic page, we look at the aggregate picture of air pollution – both indoor and outdoor. We also have dedicated topic pages that look in more depth at these subjects:

Indoor Air Pollution

Look in detail at the data and research on the health impacts of Indoor Air Pollution, attributed deaths, and its causes across the world

Outdoor Air Pollution

Look in detail at the data and research on exposure to Outdoor Air Pollution, its health impacts, and attributed deaths across the world

Look in detail at the data and research on energy consumption, its impacts around the world today, and how this has changed over time

See all interactive charts on Air Pollution ↓

Other research and writing on air pollution on Our World in Data:

• Air pollution: does it get worse before it gets better?
• Data Review: How many people die from air pollution?
• Energy poverty and indoor air pollution: a problem as old as humanity that we can end within our lifetime
• How many people do not have access to clean fuels for cooking?
• What are the safest and cleanest sources of energy?
• What the history of London’s air pollution can tell us about the future of today’s growing megacities
• When will countries phase out coal power?

Air pollution is one of the world's leading risk factors for death

Air pollution is responsible for millions of deaths each year.

Air pollution – the combination of outdoor and indoor particulate matter and ozone – is a risk factor for many of the leading causes of death, including heart disease, stroke, lower respiratory infections, lung cancer, diabetes, and chronic obstructive pulmonary disease (COPD).

The Institute for Health Metrics and Evaluation (IHME), in its Global Burden of Disease study, provides estimates of the number of deaths attributed to the range of risk factors for disease. 1

In the visualization, we see the number of deaths per year attributed to each risk factor. This chart shows the global total but can be explored for any country or region using the "change country" toggle.

Air pollution is one of the leading risk factors for death. In low-income countries, it is often very near the top of the list (or is the leading risk factor).

Air pollution contributes to one in ten deaths globally

In recent years, air pollution has contributed to one in ten deaths globally. 2

In the map shown here, we see the share of deaths attributed to air pollution across the world.

Air pollution is one of the leading risk factors for disease burden

Air pollution is one of the leading risk factors for death. But its impacts go even further; it is also one of the main contributors to the global disease burden.

Global disease burden takes into account not only years of life lost to early death but also the number of years lived in poor health.

In the visualization, we see risk factors ranked in order of DALYs – disability-adjusted life years – the metric used to assess disease burden. Again, air pollution is near the top of the list, making it one of the leading risk factors for poor health across the world.

Air pollution not only takes years from people's lives but also has a large effect on the quality of life while they're still living.

Who is most affected by air pollution?

Death rates from air pollution are highest in low-to-middle-income countries.

Air pollution is a health and environmental issue across all countries of the world but with large differences in severity.

In the interactive map, we show death rates from air pollution across the world, measured as the number of deaths per 100,000 people in a given country or region.

The burden of air pollution tends to be greater across both low and middle-income countries for two reasons: indoor pollution rates tend to be high in low-income countries due to a reliance on solid fuels for cooking, and outdoor air pollution tends to increase as countries industrialize and shift from low to middle incomes.

A map of the number of deaths from air pollution by country can be found here .

How are death rates from air pollution changing?

Death rates from air pollution are falling – mainly due to improvements in indoor pollution.

In the visualization, we show global death rates from air pollution over time – shown as the total air pollution – in addition to the individual contributions from outdoor and indoor pollution.

Globally, we see that in recent decades, the death rates from total air pollution have declined: since 1990, death rates have nearly halved. But, as we see from the breakdown, this decline has been primarily driven by improvements in indoor air pollution.

Death rates from indoor air pollution have seen an impressive decline, while improvements in outdoor pollution have been much more modest.

You can explore this data for any country or region using the "change country" toggle on the interactive chart.

Interactive charts on air pollution

Murray, C. J., Aravkin, A. Y., Zheng, P., Abbafati, C., Abbas, K. M., Abbasi-Kangevari, M., ... & Borzouei, S. (2020). Global burden of 87 risk factors in 204 countries and territories, 1990–2019: a systematic analysis for the Global Burden of Disease Study 2019 .  The Lancet ,  396 (10258), 1223-1249.

Here, we use the term 'contributes,' meaning it was one of the attributed risk factors for a given disease or cause of death. There can be multiple risk factors for a given disease that can amplify one another. This means that in some cases, air pollution was not the only risk factor but one of several.

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REVIEW article

Environmental and health impacts of air pollution: a review.

• 1 Delphis S.A., Kifisia, Greece
• 2 Laboratory of Hygiene and Environmental Protection, Faculty of Medicine, Democritus University of Thrace, Alexandroupolis, Greece
• 3 Centre Hospitalier Universitaire Vaudois (CHUV), Service de Médicine Interne, Lausanne, Switzerland
• 4 School of Social and Political Sciences, University of Glasgow, Glasgow, United Kingdom

One of our era's greatest scourges is air pollution, on account not only of its impact on climate change but also its impact on public and individual health due to increasing morbidity and mortality. There are many pollutants that are major factors in disease in humans. Among them, Particulate Matter (PM), particles of variable but very small diameter, penetrate the respiratory system via inhalation, causing respiratory and cardiovascular diseases, reproductive and central nervous system dysfunctions, and cancer. Despite the fact that ozone in the stratosphere plays a protective role against ultraviolet irradiation, it is harmful when in high concentration at ground level, also affecting the respiratory and cardiovascular system. Furthermore, nitrogen oxide, sulfur dioxide, Volatile Organic Compounds (VOCs), dioxins, and polycyclic aromatic hydrocarbons (PAHs) are all considered air pollutants that are harmful to humans. Carbon monoxide can even provoke direct poisoning when breathed in at high levels. Heavy metals such as lead, when absorbed into the human body, can lead to direct poisoning or chronic intoxication, depending on exposure. Diseases occurring from the aforementioned substances include principally respiratory problems such as Chronic Obstructive Pulmonary Disease (COPD), asthma, bronchiolitis, and also lung cancer, cardiovascular events, central nervous system dysfunctions, and cutaneous diseases. Last but not least, climate change resulting from environmental pollution affects the geographical distribution of many infectious diseases, as do natural disasters. The only way to tackle this problem is through public awareness coupled with a multidisciplinary approach by scientific experts; national and international organizations must address the emergence of this threat and propose sustainable solutions.

Approach to the Problem

The interactions between humans and their physical surroundings have been extensively studied, as multiple human activities influence the environment. The environment is a coupling of the biotic (living organisms and microorganisms) and the abiotic (hydrosphere, lithosphere, and atmosphere).

Pollution is defined as the introduction into the environment of substances harmful to humans and other living organisms. Pollutants are harmful solids, liquids, or gases produced in higher than usual concentrations that reduce the quality of our environment.

Human activities have an adverse effect on the environment by polluting the water we drink, the air we breathe, and the soil in which plants grow. Although the industrial revolution was a great success in terms of technology, society, and the provision of multiple services, it also introduced the production of huge quantities of pollutants emitted into the air that are harmful to human health. Without any doubt, the global environmental pollution is considered an international public health issue with multiple facets. Social, economic, and legislative concerns and lifestyle habits are related to this major problem. Clearly, urbanization and industrialization are reaching unprecedented and upsetting proportions worldwide in our era. Anthropogenic air pollution is one of the biggest public health hazards worldwide, given that it accounts for about 9 million deaths per year ( 1 ).

Without a doubt, all of the aforementioned are closely associated with climate change, and in the event of danger, the consequences can be severe for mankind ( 2 ). Climate changes and the effects of global planetary warming seriously affect multiple ecosystems, causing problems such as food safety issues, ice and iceberg melting, animal extinction, and damage to plants ( 3 , 4 ).

Air pollution has various health effects. The health of susceptible and sensitive individuals can be impacted even on low air pollution days. Short-term exposure to air pollutants is closely related to COPD (Chronic Obstructive Pulmonary Disease), cough, shortness of breath, wheezing, asthma, respiratory disease, and high rates of hospitalization (a measurement of morbidity).

The long-term effects associated with air pollution are chronic asthma, pulmonary insufficiency, cardiovascular diseases, and cardiovascular mortality. According to a Swedish cohort study, diabetes seems to be induced after long-term air pollution exposure ( 5 ). Moreover, air pollution seems to have various malign health effects in early human life, such as respiratory, cardiovascular, mental, and perinatal disorders ( 3 ), leading to infant mortality or chronic disease in adult age ( 6 ).

National reports have mentioned the increased risk of morbidity and mortality ( 1 ). These studies were conducted in many places around the world and show a correlation between daily ranges of particulate matter (PM) concentration and daily mortality. Climate shifts and global planetary warming ( 3 ) could aggravate the situation. Besides, increased hospitalization (an index of morbidity) has been registered among the elderly and susceptible individuals for specific reasons. Fine and ultrafine particulate matter seems to be associated with more serious illnesses ( 6 ), as it can invade the deepest parts of the airways and more easily reach the bloodstream.

Air pollution mainly affects those living in large urban areas, where road emissions contribute the most to the degradation of air quality. There is also a danger of industrial accidents, where the spread of a toxic fog can be fatal to the populations of the surrounding areas. The dispersion of pollutants is determined by many parameters, most notably atmospheric stability and wind ( 6 ).

In developing countries ( 7 ), the problem is more serious due to overpopulation and uncontrolled urbanization along with the development of industrialization. This leads to poor air quality, especially in countries with social disparities and a lack of information on sustainable management of the environment. The use of fuels such as wood fuel or solid fuel for domestic needs due to low incomes exposes people to bad-quality, polluted air at home. It is of note that three billion people around the world are using the above sources of energy for their daily heating and cooking needs ( 8 ). In developing countries, the women of the household seem to carry the highest risk for disease development due to their longer duration exposure to the indoor air pollution ( 8 , 9 ). Due to its fast industrial development and overpopulation, China is one of the Asian countries confronting serious air pollution problems ( 10 , 11 ). The lung cancer mortality observed in China is associated with fine particles ( 12 ). As stated already, long-term exposure is associated with deleterious effects on the cardiovascular system ( 3 , 5 ). However, it is interesting to note that cardiovascular diseases have mostly been observed in developed and high-income countries rather than in the developing low-income countries exposed highly to air pollution ( 13 ). Extreme air pollution is recorded in India, where the air quality reaches hazardous levels. New Delhi is one of the more polluted cities in India. Flights in and out of New Delhi International Airport are often canceled due to the reduced visibility associated with air pollution. Pollution is occurring both in urban and rural areas in India due to the fast industrialization, urbanization, and rise in use of motorcycle transportation. Nevertheless, biomass combustion associated with heating and cooking needs and practices is a major source of household air pollution in India and in Nepal ( 14 , 15 ). There is spatial heterogeneity in India, as areas with diverse climatological conditions and population and education levels generate different indoor air qualities, with higher PM 2.5 observed in North Indian states (557–601 μg/m 3 ) compared to the Southern States (183–214 μg/m 3 ) ( 16 , 17 ). The cold climate of the North Indian areas may be the main reason for this, as longer periods at home and more heating are necessary compared to in the tropical climate of Southern India. Household air pollution in India is associated with major health effects, especially in women and young children, who stay indoors for longer periods. Chronic obstructive respiratory disease (CORD) and lung cancer are mostly observed in women, while acute lower respiratory disease is seen in young children under 5 years of age ( 18 ).

Accumulation of air pollution, especially sulfur dioxide and smoke, reaching 1,500 mg/m3, resulted in an increase in the number of deaths (4,000 deaths) in December 1952 in London and in 1963 in New York City (400 deaths) ( 19 ). An association of pollution with mortality was reported on the basis of monitoring of outdoor pollution in six US metropolitan cities ( 20 ). In every case, it seems that mortality was closely related to the levels of fine, inhalable, and sulfate particles more than with the levels of total particulate pollution, aerosol acidity, sulfur dioxide, or nitrogen dioxide ( 20 ).

Furthermore, extremely high levels of pollution are reported in Mexico City and Rio de Janeiro, followed by Milan, Ankara, Melbourne, Tokyo, and Moscow ( 19 ).

Based on the magnitude of the public health impact, it is certain that different kinds of interventions should be taken into account. Success and effectiveness in controlling air pollution, specifically at the local level, have been reported. Adequate technological means are applied considering the source and the nature of the emission as well as its impact on health and the environment. The importance of point sources and non-point sources of air pollution control is reported by Schwela and Köth-Jahr ( 21 ). Without a doubt, a detailed emission inventory must record all sources in a given area. Beyond considering the above sources and their nature, topography and meteorology should also be considered, as stated previously. Assessment of the control policies and methods is often extrapolated from the local to the regional and then to the global scale. Air pollution may be dispersed and transported from one region to another area located far away. Air pollution management means the reduction to acceptable levels or possible elimination of air pollutants whose presence in the air affects our health or the environmental ecosystem. Private and governmental entities and authorities implement actions to ensure the air quality ( 22 ). Air quality standards and guidelines were adopted for the different pollutants by the WHO and EPA as a tool for the management of air quality ( 1 , 23 ). These standards have to be compared to the emissions inventory standards by causal analysis and dispersion modeling in order to reveal the problematic areas ( 24 ). Inventories are generally based on a combination of direct measurements and emissions modeling ( 24 ).

As an example, we state here the control measures at the source through the use of catalytic converters in cars. These are devices that turn the pollutants and toxic gases produced from combustion engines into less-toxic pollutants by catalysis through redox reactions ( 25 ). In Greece, the use of private cars was restricted by tracking their license plates in order to reduce traffic congestion during rush hour ( 25 ).

Concerning industrial emissions, collectors and closed systems can keep the air pollution to the minimal standards imposed by legislation ( 26 ).

Current strategies to improve air quality require an estimation of the economic value of the benefits gained from proposed programs. These proposed programs by public authorities, and directives are issued with guidelines to be respected.

In Europe, air quality limit values AQLVs (Air Quality Limit Values) are issued for setting off planning claims ( 27 ). In the USA, the NAAQS (National Ambient Air Quality Standards) establish the national air quality limit values ( 27 ). While both standards and directives are based on different mechanisms, significant success has been achieved in the reduction of overall emissions and associated health and environmental effects ( 27 ). The European Directive identifies geographical areas of risk exposure as monitoring/assessment zones to record the emission sources and levels of air pollution ( 27 ), whereas the USA establishes global geographical air quality criteria according to the severity of their air quality problem and records all sources of the pollutants and their precursors ( 27 ).

In this vein, funds have been financing, directly or indirectly, projects related to air quality along with the technical infrastructure to maintain good air quality. These plans focus on an inventory of databases from air quality environmental planning awareness campaigns. Moreover, pollution measures of air emissions may be taken for vehicles, machines, and industries in urban areas.

Technological innovation can only be successful if it is able to meet the needs of society. In this sense, technology must reflect the decision-making practices and procedures of those involved in risk assessment and evaluation and act as a facilitator in providing information and assessments to enable decision makers to make the best decisions possible. Summarizing the aforementioned in order to design an effective air quality control strategy, several aspects must be considered: environmental factors and ambient air quality conditions, engineering factors and air pollutant characteristics, and finally, economic operating costs for technological improvement and administrative and legal costs. Considering the economic factor, competitiveness through neoliberal concepts is offering a solution to environmental problems ( 22 ).

The development of environmental governance, along with technological progress, has initiated the deployment of a dialogue. Environmental politics has created objections and points of opposition between different political parties, scientists, media, and governmental and non-governmental organizations ( 22 ). Radical environmental activism actions and movements have been created ( 22 ). The rise of the new information and communication technologies (ICTs) are many times examined as to whether and in which way they have influenced means of communication and social movements such as activism ( 28 ). Since the 1990s, the term “digital activism” has been used increasingly and in many different disciplines ( 29 ). Nowadays, multiple digital technologies can be used to produce a digital activism outcome on environmental issues. More specifically, devices with online capabilities such as computers or mobile phones are being used as a way to pursue change in political and social affairs ( 30 ).

In the present paper, we focus on the sources of environmental pollution in relation to public health and propose some solutions and interventions that may be of interest to environmental legislators and decision makers.

Sources of Exposure

It is known that the majority of environmental pollutants are emitted through large-scale human activities such as the use of industrial machinery, power-producing stations, combustion engines, and cars. Because these activities are performed at such a large scale, they are by far the major contributors to air pollution, with cars estimated to be responsible for approximately 80% of today's pollution ( 31 ). Some other human activities are also influencing our environment to a lesser extent, such as field cultivation techniques, gas stations, fuel tanks heaters, and cleaning procedures ( 32 ), as well as several natural sources, such as volcanic and soil eruptions and forest fires.

The classification of air pollutants is based mainly on the sources producing pollution. Therefore, it is worth mentioning the four main sources, following the classification system: Major sources, Area sources, Mobile sources, and Natural sources.

Major sources include the emission of pollutants from power stations, refineries, and petrochemicals, the chemical and fertilizer industries, metallurgical and other industrial plants, and, finally, municipal incineration.

Indoor area sources include domestic cleaning activities, dry cleaners, printing shops, and petrol stations.

Mobile sources include automobiles, cars, railways, airways, and other types of vehicles.

Finally, natural sources include, as stated previously, physical disasters ( 33 ) such as forest fire, volcanic erosion, dust storms, and agricultural burning.

However, many classification systems have been proposed. Another type of classification is a grouping according to the recipient of the pollution, as follows:

Air pollution is determined as the presence of pollutants in the air in large quantities for long periods. Air pollutants are dispersed particles, hydrocarbons, CO, CO 2 , NO, NO 2 , SO 3 , etc.

Water pollution is organic and inorganic charge and biological charge ( 10 ) at high levels that affect the water quality ( 34 , 35 ).

Soil pollution occurs through the release of chemicals or the disposal of wastes, such as heavy metals, hydrocarbons, and pesticides.

Air pollution can influence the quality of soil and water bodies by polluting precipitation, falling into water and soil environments ( 34 , 36 ). Notably, the chemistry of the soil can be amended due to acid precipitation by affecting plants, cultures, and water quality ( 37 ). Moreover, movement of heavy metals is favored by soil acidity, and metals are so then moving into the watery environment. It is known that heavy metals such as aluminum are noxious to wildlife and fishes. Soil quality seems to be of importance, as soils with low calcium carbonate levels are at increased jeopardy from acid rain. Over and above rain, snow and particulate matter drip into watery ' bodies ( 36 , 38 ).

Lastly, pollution is classified following type of origin:

Radioactive and nuclear pollution , releasing radioactive and nuclear pollutants into water, air, and soil during nuclear explosions and accidents, from nuclear weapons, and through handling or disposal of radioactive sewage.

Radioactive materials can contaminate surface water bodies and, being noxious to the environment, plants, animals, and humans. It is known that several radioactive substances such as radium and uranium concentrate in the bones and can cause cancers ( 38 , 39 ).

Noise pollution is produced by machines, vehicles, traffic noises, and musical installations that are harmful to our hearing.

The World Health Organization introduced the term DALYs. The DALYs for a disease or health condition is defined as the sum of the Years of Life Lost (YLL) due to premature mortality in the population and the Years Lost due to Disability (YLD) for people living with the health condition or its consequences ( 39 ). In Europe, air pollution is the main cause of disability-adjusted life years lost (DALYs), followed by noise pollution. The potential relationships of noise and air pollution with health have been studied ( 40 ). The study found that DALYs related to noise were more important than those related to air pollution, as the effects of environmental noise on cardiovascular disease were independent of air pollution ( 40 ). Environmental noise should be counted as an independent public health risk ( 40 ).

Environmental pollution occurs when changes in the physical, chemical, or biological constituents of the environment (air masses, temperature, climate, etc.) are produced.

Pollutants harm our environment either by increasing levels above normal or by introducing harmful toxic substances. Primary pollutants are directly produced from the above sources, and secondary pollutants are emitted as by-products of the primary ones. Pollutants can be biodegradable or non-biodegradable and of natural origin or anthropogenic, as stated previously. Moreover, their origin can be a unique source (point-source) or dispersed sources.

Pollutants have differences in physical and chemical properties, explaining the discrepancy in their capacity for producing toxic effects. As an example, we state here that aerosol compounds ( 41 – 43 ) have a greater toxicity than gaseous compounds due to their tiny size (solid or liquid) in the atmosphere; they have a greater penetration capacity. Gaseous compounds are eliminated more easily by our respiratory system ( 41 ). These particles are able to damage lungs and can even enter the bloodstream ( 41 ), leading to the premature deaths of millions of people yearly. Moreover, the aerosol acidity ([H+]) seems to considerably enhance the production of secondary organic aerosols (SOA), but this last aspect is not supported by other scientific teams ( 38 ).

Climate and Pollution

Air pollution and climate change are closely related. Climate is the other side of the same coin that reduces the quality of our Earth ( 44 ). Pollutants such as black carbon, methane, tropospheric ozone, and aerosols affect the amount of incoming sunlight. As a result, the temperature of the Earth is increasing, resulting in the melting of ice, icebergs, and glaciers.

In this vein, climatic changes will affect the incidence and prevalence of both residual and imported infections in Europe. Climate and weather affect the duration, timing, and intensity of outbreaks strongly and change the map of infectious diseases in the globe ( 45 ). Mosquito-transmitted parasitic or viral diseases are extremely climate-sensitive, as warming firstly shortens the pathogen incubation period and secondly shifts the geographic map of the vector. Similarly, water-warming following climate changes leads to a high incidence of waterborne infections. Recently, in Europe, eradicated diseases seem to be emerging due to the migration of population, for example, cholera, poliomyelitis, tick-borne encephalitis, and malaria ( 46 ).

The spread of epidemics is associated with natural climate disasters and storms, which seem to occur more frequently nowadays ( 47 ). Malnutrition and disequilibration of the immune system are also associated with the emerging infections affecting public health ( 48 ).

The Chikungunya virus “took the airplane” from the Indian Ocean to Europe, as outbreaks of the disease were registered in Italy ( 49 ) as well as autochthonous cases in France ( 50 ).

An increase in cryptosporidiosis in the United Kingdom and in the Czech Republic seems to have occurred following flooding ( 36 , 51 ).

As stated previously, aerosols compounds are tiny in size and considerably affect the climate. They are able to dissipate sunlight (the albedo phenomenon) by dispersing a quarter of the sun's rays back to space and have cooled the global temperature over the last 30 years ( 52 ).

Air Pollutants

The World Health Organization (WHO) reports on six major air pollutants, namely particle pollution, ground-level ozone, carbon monoxide, sulfur oxides, nitrogen oxides, and lead. Air pollution can have a disastrous effect on all components of the environment, including groundwater, soil, and air. Additionally, it poses a serious threat to living organisms. In this vein, our interest is mainly to focus on these pollutants, as they are related to more extensive and severe problems in human health and environmental impact. Acid rain, global warming, the greenhouse effect, and climate changes have an important ecological impact on air pollution ( 53 ).

Particulate Matter (PM) and Health

Studies have shown a relationship between particulate matter (PM) and adverse health effects, focusing on either short-term (acute) or long-term (chronic) PM exposure.

Particulate matter (PM) is usually formed in the atmosphere as a result of chemical reactions between the different pollutants. The penetration of particles is closely dependent on their size ( 53 ). Particulate Matter (PM) was defined as a term for particles by the United States Environmental Protection Agency ( 54 ). Particulate matter (PM) pollution includes particles with diameters of 10 micrometers (μm) or smaller, called PM 10 , and extremely fine particles with diameters that are generally 2.5 micrometers (μm) and smaller.

Particulate matter contains tiny liquid or solid droplets that can be inhaled and cause serious health effects ( 55 ). Particles <10 μm in diameter (PM 10 ) after inhalation can invade the lungs and even reach the bloodstream. Fine particles, PM 2.5 , pose a greater risk to health ( 6 , 56 ) ( Table 1 ).

Table 1 . Penetrability according to particle size.

Multiple epidemiological studies have been performed on the health effects of PM. A positive relation was shown between both short-term and long-term exposures of PM 2.5 and acute nasopharyngitis ( 56 ). In addition, long-term exposure to PM for years was found to be related to cardiovascular diseases and infant mortality.

Those studies depend on PM 2.5 monitors and are restricted in terms of study area or city area due to a lack of spatially resolved daily PM 2.5 concentration data and, in this way, are not representative of the entire population. Following a recent epidemiological study by the Department of Environmental Health at Harvard School of Public Health (Boston, MA) ( 57 ), it was reported that, as PM 2.5 concentrations vary spatially, an exposure error (Berkson error) seems to be produced, and the relative magnitudes of the short- and long-term effects are not yet completely elucidated. The team developed a PM 2.5 exposure model based on remote sensing data for assessing short- and long-term human exposures ( 57 ). This model permits spatial resolution in short-term effects plus the assessment of long-term effects in the whole population.

Moreover, respiratory diseases and affection of the immune system are registered as long-term chronic effects ( 58 ). It is worth noting that people with asthma, pneumonia, diabetes, and respiratory and cardiovascular diseases are especially susceptible and vulnerable to the effects of PM. PM 2.5 , followed by PM 10 , are strongly associated with diverse respiratory system diseases ( 59 ), as their size permits them to pierce interior spaces ( 60 ). The particles produce toxic effects according to their chemical and physical properties. The components of PM 10 and PM 2.5 can be organic (polycyclic aromatic hydrocarbons, dioxins, benzene, 1-3 butadiene) or inorganic (carbon, chlorides, nitrates, sulfates, metals) in nature ( 55 ).

Particulate Matter (PM) is divided into four main categories according to type and size ( 61 ) ( Table 2 ).

Table 2 . Types and sizes of particulate Matter (PM).

Gas contaminants include PM in aerial masses.

Particulate contaminants include contaminants such as smog, soot, tobacco smoke, oil smoke, fly ash, and cement dust.

Biological Contaminants are microorganisms (bacteria, viruses, fungi, mold, and bacterial spores), cat allergens, house dust and allergens, and pollen.

Types of Dust include suspended atmospheric dust, settling dust, and heavy dust.

Finally, another fact is that the half-lives of PM 10 and PM 2.5 particles in the atmosphere is extended due to their tiny dimensions; this permits their long-lasting suspension in the atmosphere and even their transfer and spread to distant destinations where people and the environment may be exposed to the same magnitude of pollution ( 53 ). They are able to change the nutrient balance in watery ecosystems, damage forests and crops, and acidify water bodies.

As stated, PM 2.5 , due to their tiny size, are causing more serious health effects. These aforementioned fine particles are the main cause of the “haze” formation in different metropolitan areas ( 12 , 13 , 61 ).

Ozone Impact in the Atmosphere

Ozone (O 3 ) is a gas formed from oxygen under high voltage electric discharge ( 62 ). It is a strong oxidant, 52% stronger than chlorine. It arises in the stratosphere, but it could also arise following chain reactions of photochemical smog in the troposphere ( 63 ).

Ozone can travel to distant areas from its initial source, moving with air masses ( 64 ). It is surprising that ozone levels over cities are low in contrast to the increased amounts occuring in urban areas, which could become harmful for cultures, forests, and vegetation ( 65 ) as it is reducing carbon assimilation ( 66 ). Ozone reduces growth and yield ( 47 , 48 ) and affects the plant microflora due to its antimicrobial capacity ( 67 , 68 ). In this regard, ozone acts upon other natural ecosystems, with microflora ( 69 , 70 ) and animal species changing their species composition ( 71 ). Ozone increases DNA damage in epidermal keratinocytes and leads to impaired cellular function ( 72 ).

Ground-level ozone (GLO) is generated through a chemical reaction between oxides of nitrogen and VOCs emitted from natural sources and/or following anthropogenic activities.

Ozone uptake usually occurs by inhalation. Ozone affects the upper layers of the skin and the tear ducts ( 73 ). A study of short-term exposure of mice to high levels of ozone showed malondialdehyde formation in the upper skin (epidermis) but also depletion in vitamins C and E. It is likely that ozone levels are not interfering with the skin barrier function and integrity to predispose to skin disease ( 74 ).

Due to the low water-solubility of ozone, inhaled ozone has the capacity to penetrate deeply into the lungs ( 75 ).

Toxic effects induced by ozone are registered in urban areas all over the world, causing biochemical, morphologic, functional, and immunological disorders ( 76 ).

The European project (APHEA2) focuses on the acute effects of ambient ozone concentrations on mortality ( 77 ). Daily ozone concentrations compared to the daily number of deaths were reported from different European cities for a 3-year period. During the warm period of the year, an observed increase in ozone concentration was associated with an increase in the daily number of deaths (0.33%), in the number of respiratory deaths (1.13%), and in the number of cardiovascular deaths (0.45%). No effect was observed during wintertime.

Carbon Monoxide (CO)

Carbon monoxide is produced by fossil fuel when combustion is incomplete. The symptoms of poisoning due to inhaling carbon monoxide include headache, dizziness, weakness, nausea, vomiting, and, finally, loss of consciousness.

The affinity of carbon monoxide to hemoglobin is much greater than that of oxygen. In this vein, serious poisoning may occur in people exposed to high levels of carbon monoxide for a long period of time. Due to the loss of oxygen as a result of the competitive binding of carbon monoxide, hypoxia, ischemia, and cardiovascular disease are observed.

Carbon monoxide affects the greenhouses gases that are tightly connected to global warming and climate. This should lead to an increase in soil and water temperatures, and extreme weather conditions or storms may occur ( 68 ).

However, in laboratory and field experiments, it has been seen to produce increased plant growth ( 78 ).

Nitrogen Oxide (NO 2 )

Nitrogen oxide is a traffic-related pollutant, as it is emitted from automobile motor engines ( 79 , 80 ). It is an irritant of the respiratory system as it penetrates deep in the lung, inducing respiratory diseases, coughing, wheezing, dyspnea, bronchospasm, and even pulmonary edema when inhaled at high levels. It seems that concentrations over 0.2 ppm produce these adverse effects in humans, while concentrations higher than 2.0 ppm affect T-lymphocytes, particularly the CD8+ cells and NK cells that produce our immune response ( 81 ).It is reported that long-term exposure to high levels of nitrogen dioxide can be responsible for chronic lung disease. Long-term exposure to NO 2 can impair the sense of smell ( 81 ).

However, systems other than respiratory ones can be involved, as symptoms such as eye, throat, and nose irritation have been registered ( 81 ).

High levels of nitrogen dioxide are deleterious to crops and vegetation, as they have been observed to reduce crop yield and plant growth efficiency. Moreover, NO 2 can reduce visibility and discolor fabrics ( 81 ).

Sulfur Dioxide (SO 2 )

Sulfur dioxide is a harmful gas that is emitted mainly from fossil fuel consumption or industrial activities. The annual standard for SO 2 is 0.03 ppm ( 82 ). It affects human, animal, and plant life. Susceptible people as those with lung disease, old people, and children, who present a higher risk of damage. The major health problems associated with sulfur dioxide emissions in industrialized areas are respiratory irritation, bronchitis, mucus production, and bronchospasm, as it is a sensory irritant and penetrates deep into the lung converted into bisulfite and interacting with sensory receptors, causing bronchoconstriction. Moreover, skin redness, damage to the eyes (lacrimation and corneal opacity) and mucous membranes, and worsening of pre-existing cardiovascular disease have been observed ( 81 ).

Environmental adverse effects, such as acidification of soil and acid rain, seem to be associated with sulfur dioxide emissions ( 83 ).

Lead is a heavy metal used in different industrial plants and emitted from some petrol motor engines, batteries, radiators, waste incinerators, and waste waters ( 84 ).

Moreover, major sources of lead pollution in the air are metals, ore, and piston-engine aircraft. Lead poisoning is a threat to public health due to its deleterious effects upon humans, animals, and the environment, especially in the developing countries.

Exposure to lead can occur through inhalation, ingestion, and dermal absorption. Trans- placental transport of lead was also reported, as lead passes through the placenta unencumbered ( 85 ). The younger the fetus is, the more harmful the toxic effects. Lead toxicity affects the fetal nervous system; edema or swelling of the brain is observed ( 86 ). Lead, when inhaled, accumulates in the blood, soft tissue, liver, lung, bones, and cardiovascular, nervous, and reproductive systems. Moreover, loss of concentration and memory, as well as muscle and joint pain, were observed in adults ( 85 , 86 ).

Children and newborns ( 87 ) are extremely susceptible even to minimal doses of lead, as it is a neurotoxicant and causes learning disabilities, impairment of memory, hyperactivity, and even mental retardation.

Elevated amounts of lead in the environment are harmful to plants and crop growth. Neurological effects are observed in vertebrates and animals in association with high lead levels ( 88 ).

Polycyclic Aromatic Hydrocarbons(PAHs)

The distribution of PAHs is ubiquitous in the environment, as the atmosphere is the most important means of their dispersal. They are found in coal and in tar sediments. Moreover, they are generated through incomplete combustion of organic matter as in the cases of forest fires, incineration, and engines ( 89 ). PAH compounds, such as benzopyrene, acenaphthylene, anthracene, and fluoranthene are recognized as toxic, mutagenic, and carcinogenic substances. They are an important risk factor for lung cancer ( 89 ).

Volatile Organic Compounds(VOCs)

Volatile organic compounds (VOCs), such as toluene, benzene, ethylbenzene, and xylene ( 90 ), have been found to be associated with cancer in humans ( 91 ). The use of new products and materials has actually resulted in increased concentrations of VOCs. VOCs pollute indoor air ( 90 ) and may have adverse effects on human health ( 91 ). Short-term and long-term adverse effects on human health are observed. VOCs are responsible for indoor air smells. Short-term exposure is found to cause irritation of eyes, nose, throat, and mucosal membranes, while those of long duration exposure include toxic reactions ( 92 ). Predictable assessment of the toxic effects of complex VOC mixtures is difficult to estimate, as these pollutants can have synergic, antagonistic, or indifferent effects ( 91 , 93 ).

Dioxins originate from industrial processes but also come from natural processes, such as forest fires and volcanic eruptions. They accumulate in foods such as meat and dairy products, fish and shellfish, and especially in the fatty tissue of animals ( 94 ).

Short-period exhibition to high dioxin concentrations may result in dark spots and lesions on the skin ( 94 ). Long-term exposure to dioxins can cause developmental problems, impairment of the immune, endocrine and nervous systems, reproductive infertility, and cancer ( 94 ).

Without any doubt, fossil fuel consumption is responsible for a sizeable part of air contamination. This contamination may be anthropogenic, as in agricultural and industrial processes or transportation, while contamination from natural sources is also possible. Interestingly, it is of note that the air quality standards established through the European Air Quality Directive are somewhat looser than the WHO guidelines, which are stricter ( 95 ).

Effect of Air Pollution on Health

The most common air pollutants are ground-level ozone and Particulates Matter (PM). Air pollution is distinguished into two main types:

Outdoor pollution is the ambient air pollution.

Indoor pollution is the pollution generated by household combustion of fuels.

People exposed to high concentrations of air pollutants experience disease symptoms and states of greater and lesser seriousness. These effects are grouped into short- and long-term effects affecting health.

Susceptible populations that need to be aware of health protection measures include old people, children, and people with diabetes and predisposing heart or lung disease, especially asthma.

As extensively stated previously, according to a recent epidemiological study from Harvard School of Public Health, the relative magnitudes of the short- and long-term effects have not been completely clarified ( 57 ) due to the different epidemiological methodologies and to the exposure errors. New models are proposed for assessing short- and long-term human exposure data more successfully ( 57 ). Thus, in the present section, we report the more common short- and long-term health effects but also general concerns for both types of effects, as these effects are often dependent on environmental conditions, dose, and individual susceptibility.

Short-term effects are temporary and range from simple discomfort, such as irritation of the eyes, nose, skin, throat, wheezing, coughing and chest tightness, and breathing difficulties, to more serious states, such as asthma, pneumonia, bronchitis, and lung and heart problems. Short-term exposure to air pollution can also cause headaches, nausea, and dizziness.

These problems can be aggravated by extended long-term exposure to the pollutants, which is harmful to the neurological, reproductive, and respiratory systems and causes cancer and even, rarely, deaths.

The long-term effects are chronic, lasting for years or the whole life and can even lead to death. Furthermore, the toxicity of several air pollutants may also induce a variety of cancers in the long term ( 96 ).

As stated already, respiratory disorders are closely associated with the inhalation of air pollutants. These pollutants will invade through the airways and will accumulate at the cells. Damage to target cells should be related to the pollutant component involved and its source and dose. Health effects are also closely dependent on country, area, season, and time. An extended exposure duration to the pollutant should incline to long-term health effects in relation also to the above factors.

Particulate Matter (PMs), dust, benzene, and O 3 cause serious damage to the respiratory system ( 97 ). Moreover, there is a supplementary risk in case of existing respiratory disease such as asthma ( 98 ). Long-term effects are more frequent in people with a predisposing disease state. When the trachea is contaminated by pollutants, voice alterations may be remarked after acute exposure. Chronic obstructive pulmonary disease (COPD) may be induced following air pollution, increasing morbidity and mortality ( 99 ). Long-term effects from traffic, industrial air pollution, and combustion of fuels are the major factors for COPD risk ( 99 ).

Multiple cardiovascular effects have been observed after exposure to air pollutants ( 100 ). Changes occurred in blood cells after long-term exposure may affect cardiac functionality. Coronary arteriosclerosis was reported following long-term exposure to traffic emissions ( 101 ), while short-term exposure is related to hypertension, stroke, myocardial infracts, and heart insufficiency. Ventricle hypertrophy is reported to occur in humans after long-time exposure to nitrogen oxide (NO 2 ) ( 102 , 103 ).

Neurological effects have been observed in adults and children after extended-term exposure to air pollutants.

Psychological complications, autism, retinopathy, fetal growth, and low birth weight seem to be related to long-term air pollution ( 83 ). The etiologic agent of the neurodegenerative diseases (Alzheimer's and Parkinson's) is not yet known, although it is believed that extended exposure to air pollution seems to be a factor. Specifically, pesticides and metals are cited as etiological factors, together with diet. The mechanisms in the development of neurodegenerative disease include oxidative stress, protein aggregation, inflammation, and mitochondrial impairment in neurons ( 104 ) ( Figure 1 ).

Figure 1 . Impact of air pollutants on the brain.

Brain inflammation was observed in dogs living in a highly polluted area in Mexico for a long period ( 105 ). In human adults, markers of systemic inflammation (IL-6 and fibrinogen) were found to be increased as an immediate response to PNC on the IL-6 level, possibly leading to the production of acute-phase proteins ( 106 ). The progression of atherosclerosis and oxidative stress seem to be the mechanisms involved in the neurological disturbances caused by long-term air pollution. Inflammation comes secondary to the oxidative stress and seems to be involved in the impairment of developmental maturation, affecting multiple organs ( 105 , 107 ). Similarly, other factors seem to be involved in the developmental maturation, which define the vulnerability to long-term air pollution. These include birthweight, maternal smoking, genetic background and socioeconomic environment, as well as education level.

However, diet, starting from breast-feeding, is another determinant factor. Diet is the main source of antioxidants, which play a key role in our protection against air pollutants ( 108 ). Antioxidants are free radical scavengers and limit the interaction of free radicals in the brain ( 108 ). Similarly, genetic background may result in a differential susceptibility toward the oxidative stress pathway ( 60 ). For example, antioxidant supplementation with vitamins C and E appears to modulate the effect of ozone in asthmatic children homozygous for the GSTM1 null allele ( 61 ). Inflammatory cytokines released in the periphery (e.g., respiratory epithelia) upregulate the innate immune Toll-like receptor 2. Such activation and the subsequent events leading to neurodegeneration have recently been observed in lung lavage in mice exposed to ambient Los Angeles (CA, USA) particulate matter ( 61 ). In children, neurodevelopmental morbidities were observed after lead exposure. These children developed aggressive and delinquent behavior, reduced intelligence, learning difficulties, and hyperactivity ( 109 ). No level of lead exposure seems to be “safe,” and the scientific community has asked the Centers for Disease Control and Prevention (CDC) to reduce the current screening guideline of 10 μg/dl ( 109 ).

It is important to state that impact on the immune system, causing dysfunction and neuroinflammation ( 104 ), is related to poor air quality. Yet, increases in serum levels of immunoglobulins (IgA, IgM) and the complement component C3 are observed ( 106 ). Another issue is that antigen presentation is affected by air pollutants, as there is an upregulation of costimulatory molecules such as CD80 and CD86 on macrophages ( 110 ).

As is known, skin is our shield against ultraviolet radiation (UVR) and other pollutants, as it is the most exterior layer of our body. Traffic-related pollutants, such as PAHs, VOCs, oxides, and PM, may cause pigmented spots on our skin ( 111 ). On the one hand, as already stated, when pollutants penetrate through the skin or are inhaled, damage to the organs is observed, as some of these pollutants are mutagenic and carcinogenic, and, specifically, they affect the liver and lung. On the other hand, air pollutants (and those in the troposphere) reduce the adverse effects of ultraviolet radiation UVR in polluted urban areas ( 111 ). Air pollutants absorbed by the human skin may contribute to skin aging, psoriasis, acne, urticaria, eczema, and atopic dermatitis ( 111 ), usually caused by exposure to oxides and photochemical smoke ( 111 ). Exposure to PM and cigarette smoking act as skin-aging agents, causing spots, dyschromia, and wrinkles. Lastly, pollutants have been associated with skin cancer ( 111 ).

Higher morbidity is reported to fetuses and children when exposed to the above dangers. Impairment in fetal growth, low birth weight, and autism have been reported ( 112 ).

Another exterior organ that may be affected is the eye. Contamination usually comes from suspended pollutants and may result in asymptomatic eye outcomes, irritation ( 112 ), retinopathy, or dry eye syndrome ( 113 , 114 ).

Environmental Impact of Air Pollution

Air pollution is harming not only human health but also the environment ( 115 ) in which we live. The most important environmental effects are as follows.

Acid rain is wet (rain, fog, snow) or dry (particulates and gas) precipitation containing toxic amounts of nitric and sulfuric acids. They are able to acidify the water and soil environments, damage trees and plantations, and even damage buildings and outdoor sculptures, constructions, and statues.

Haze is produced when fine particles are dispersed in the air and reduce the transparency of the atmosphere. It is caused by gas emissions in the air coming from industrial facilities, power plants, automobiles, and trucks.

Ozone , as discussed previously, occurs both at ground level and in the upper level (stratosphere) of the Earth's atmosphere. Stratospheric ozone is protecting us from the Sun's harmful ultraviolet (UV) rays. In contrast, ground-level ozone is harmful to human health and is a pollutant. Unfortunately, stratospheric ozone is gradually damaged by ozone-depleting substances (i.e., chemicals, pesticides, and aerosols). If this protecting stratospheric ozone layer is thinned, then UV radiation can reach our Earth, with harmful effects for human life (skin cancer) ( 116 ) and crops ( 117 ). In plants, ozone penetrates through the stomata, inducing them to close, which blocks CO 2 transfer and induces a reduction in photosynthesis ( 118 ).

Global climate change is an important issue that concerns mankind. As is known, the “greenhouse effect” keeps the Earth's temperature stable. Unhappily, anthropogenic activities have destroyed this protecting temperature effect by producing large amounts of greenhouse gases, and global warming is mounting, with harmful effects on human health, animals, forests, wildlife, agriculture, and the water environment. A report states that global warming is adding to the health risks of poor people ( 119 ).

People living in poorly constructed buildings in warm-climate countries are at high risk for heat-related health problems as temperatures mount ( 119 ).

Wildlife is burdened by toxic pollutants coming from the air, soil, or the water ecosystem and, in this way, animals can develop health problems when exposed to high levels of pollutants. Reproductive failure and birth effects have been reported.

Eutrophication is occurring when elevated concentrations of nutrients (especially nitrogen) stimulate the blooming of aquatic algae, which can cause a disequilibration in the diversity of fish and their deaths.

Without a doubt, there is a critical concentration of pollution that an ecosystem can tolerate without being destroyed, which is associated with the ecosystem's capacity to neutralize acidity. The Canada Acid Rain Program established this load at 20 kg/ha/yr ( 120 ).

Hence, air pollution has deleterious effects on both soil and water ( 121 ). Concerning PM as an air pollutant, its impact on crop yield and food productivity has been reported. Its impact on watery bodies is associated with the survival of living organisms and fishes and their productivity potential ( 121 ).

An impairment in photosynthetic rhythm and metabolism is observed in plants exposed to the effects of ozone ( 121 ).

Sulfur and nitrogen oxides are involved in the formation of acid rain and are harmful to plants and marine organisms.

Last but not least, as mentioned above, the toxicity associated with lead and other metals is the main threat to our ecosystems (air, water, and soil) and living creatures ( 121 ).

In 2018, during the first WHO Global Conference on Air Pollution and Health, the WHO's General Director, Dr. Tedros Adhanom Ghebreyesus, called air pollution a “silent public health emergency” and “the new tobacco” ( 122 ).

Undoubtedly, children are particularly vulnerable to air pollution, especially during their development. Air pollution has adverse effects on our lives in many different respects.

Diseases associated with air pollution have not only an important economic impact but also a societal impact due to absences from productive work and school.

Despite the difficulty of eradicating the problem of anthropogenic environmental pollution, a successful solution could be envisaged as a tight collaboration of authorities, bodies, and doctors to regularize the situation. Governments should spread sufficient information and educate people and should involve professionals in these issues so as to control the emergence of the problem successfully.

Technologies to reduce air pollution at the source must be established and should be used in all industries and power plants. The Kyoto Protocol of 1997 set as a major target the reduction of GHG emissions to below 5% by 2012 ( 123 ). This was followed by the Copenhagen summit, 2009 ( 124 ), and then the Durban summit of 2011 ( 125 ), where it was decided to keep to the same line of action. The Kyoto protocol and the subsequent ones were ratified by many countries. Among the pioneers who adopted this important protocol for the world's environmental and climate “health” was China ( 3 ). As is known, China is a fast-developing economy and its GDP (Gross Domestic Product) is expected to be very high by 2050, which is defined as the year of dissolution of the protocol for the decrease in gas emissions.

A more recent international agreement of crucial importance for climate change is the Paris Agreement of 2015, issued by the UNFCCC (United Nations Climate Change Committee). This latest agreement was ratified by a plethora of UN (United Nations) countries as well as the countries of the European Union ( 126 ). In this vein, parties should promote actions and measures to enhance numerous aspects around the subject. Boosting education, training, public awareness, and public participation are some of the relevant actions for maximizing the opportunities to achieve the targets and goals on the crucial matter of climate change and environmental pollution ( 126 ). Without any doubt, technological improvements makes our world easier and it seems difficult to reduce the harmful impact caused by gas emissions, we could limit its use by seeking reliable approaches.

Synopsizing, a global prevention policy should be designed in order to combat anthropogenic air pollution as a complement to the correct handling of the adverse health effects associated with air pollution. Sustainable development practices should be applied, together with information coming from research in order to handle the problem effectively.

At this point, international cooperation in terms of research, development, administration policy, monitoring, and politics is vital for effective pollution control. Legislation concerning air pollution must be aligned and updated, and policy makers should propose the design of a powerful tool of environmental and health protection. As a result, the main proposal of this essay is that we should focus on fostering local structures to promote experience and practice and extrapolate these to the international level through developing effective policies for sustainable management of ecosystems.

Author Contributions

All authors listed have made a substantial, direct and intellectual contribution to the work, and approved it for publication.

Conflict of Interest

IM is employed by the company Delphis S.A.

The remaining authors declare that the present review paper was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Keywords: air pollution, environment, health, public health, gas emission, policy

Citation: Manisalidis I, Stavropoulou E, Stavropoulos A and Bezirtzoglou E (2020) Environmental and Health Impacts of Air Pollution: A Review. Front. Public Health 8:14. doi: 10.3389/fpubh.2020.00014

Received: 17 October 2019; Accepted: 17 January 2020; Published: 20 February 2020.

Reviewed by:

Copyright © 2020 Manisalidis, Stavropoulou, Stavropoulos and Bezirtzoglou. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Ioannis Manisalidis, giannismanisal@gmail.com ; Elisavet Stavropoulou, elisabeth.stavropoulou@gmail.com

† These authors have contributed equally to this work

Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

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Open Access

Confronting plastic pollution to protect environmental and public health

* E-mail: [email protected] (LG); [email protected] (JE)

Affiliation Public Library of Science, San Francisco, California, United States of America

Affiliation Center for the Advancement of Public Action, Bennington College; Beyond Plastics, Bennington, Vermont, United States of America

• Liza Gross, 
• Judith Enck

Published: March 30, 2021

• https://doi.org/10.1371/journal.pbio.3001131
• Reader Comments

A new collection of evidence-based commentaries explores critical challenges facing scientists and policymakers working to address the potential environmental and health harms of microplastics. The commentaries reveal a pressing need to develop robust methods to detect, evaluate, and mitigate the impacts of this emerging contaminant, most recently found in human placentas.

Citation: Gross L, Enck J (2021) Confronting plastic pollution to protect environmental and public health. PLoS Biol 19(3): e3001131. https://doi.org/10.1371/journal.pbio.3001131

Copyright: © 2021 Gross, Enck. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: The authors received no specific funding for this work.

Competing interests: Liza Gross is a current paid employee of the Public Library of Science.

The explosive production of affordable plastic goods during the 1950s ushered in an era of disposable living, fueled by an addiction to convenience and consumerism, that has created one of the world’s most vexing pollution problems. Plastic, for all its uses, has left a trail of debris from the deepest ocean trenches to the remotest polar reaches. Plastic pollutes throughout its life cycle, from its beginnings as a by-product of greenhouse gas-emitting oil and natural gas refining to its degradation-resistant end as increasingly fragmented shards of micro-and nanoplastics in atmospheric currents, alpine snow, estuaries, lakes, oceans, and soils. Researchers are finding microplastics in the gut or tissue of nearly every living thing they examine, including the placentas of unborn children.

The first sign of this burgeoning crisis came nearly half a century ago, when marine biologists first spotted tiny plastic pellets stuck to tiny marine organisms and seaweed in the North Atlantic’s Sargasso Sea. Describing their discovery in 1972, the scientists predicted, presciently, that “increasing production of plastics, combined with present waste disposal practices, will probably lead to greater concentrations on the sea surface” [ 1 ].

Researchers have struggled to keep tabs on plastic production and waste ever since. The first global assessment of mass-produced plastics, reported in 2017, estimated that manufacturers had produced 8,300 million metric tons of virgin plastics, creating 6,300 million metric tons of plastic waste—with only 9% recycled, 12% incinerated, and the rest either piling up in landfills or entering the environment [ 2 ].

Some 15 million metric tons of plastic enters the oceans every year [ 3 ], choking marine mammals, invading the guts of fish and seabirds, and posing unknown risks to the animals, and people, who eat them. Plastics release toxic chemicals added during manufacturing as they splinter into smaller and smaller fragments, with half-lives ranging from 58 to 1,200 years [ 4 ]. Persistent organic pollutants have a high affinity for plastic particles, which glom on to these contaminants as do pathogens in the ocean, presenting additional risks to marine life and the food web. Scientists once viewed freshwater lakes and rivers as primarily conduits for plastic, delivering trash from land to the sea, but now realize they’re also repositories.

Plastic production increased from 2 million metric tons a year in 1950 to 380 million metric tons by 2015 and is expected to double by 2050 [ 2 ]. Petrochemical companies’ embrace of fracking has exacerbated the crisis by producing large amounts of ethane, a building block for plastic.

Recognizing the scope and urgency of addressing the plastic pollution crisis, PLOS Biology is publishing a special collection of commentaries called “Confronting plastic pollution to protect environmental and public health.”

In commissioning the collection, we aimed to illuminate critical questions about microplastics’ effects on environmental and human health and explore current challenges in addressing those questions. The collection features three evidence-based commentaries that address gaps in understanding while flagging research priorities for improving methods to detect, evaluate, and mitigate threats associated with this emerging contaminant.

Environmental ecotoxicologist Scott Coffin and colleagues address recent government efforts to assess and reduce deleterious effects of microplastics, which challenge traditional risk-based regulatory frameworks due to their particle properties, diverse composition, and persistence. In their Essay, “Addressing the environmental and health impacts of microplastics requires open collaboration between diverse sectors” [ 5 ], the authors use California as a case study to suggest strategies to deal with these uncertainties in designing research, policy, and regulation, drawing on parallels with a similar class of emerging contaminants (per- and polyfluoroalkyl substances).

In “Tackling the toxics in plastics packaging” [ 6 ], environmental toxicologist Jane Muncke focuses on a major driver of the global plastic pollution crisis: single-use food packaging. Our throwaway culture has led to the widespread use of plastic packaging for storing, transporting, preparing, and serving food, along with efforts to reduce plastic waste by giving it new life as recycled material. But these efforts ignore evidence that chemicals in plastic migrate from plastic, making harmful chemicals an unintentional part of the human diet. Addressing contamination from food packaging is an urgent public health need that requires integrating all existing knowledge, she argues.

Much early research on microplastics focused on ocean pollution. But the ubiquitous particles appear to be interfering with the very fabric of the soil environment itself, by influencing soil bulk density and the stability of the building blocks of soil structure, argue Matthias Rillig and colleagues in their Essay. Microplastics can affect the carbon cycle in numerous ways, for example, by being carbon themselves and by influencing soil microbial processes, plant growth, or litter decomposition, the authors argue in “Microplastic effects on carbon cycling processes in soils” [ 7 ]. They call for “a major concerted effort” to understand the pervasive effects of microplastics on the function of soils and terrestrial ecosystems, a monumental feat given the immense diversity of the particles’ chemistry, aging, size, and shape.

The scope and effects of plastic pollution are too vast to be captured in a few commentaries. Microplastics are everywhere and researchers are just starting to get a handle on how to study the influence of this emerging contaminant on diverse environments and organisms. But as the contributors to this collection make clear, the pervasiveness of microplastics makes them nearly impossible to avoid. And the uncertainty surrounding their potential to harm people, wildlife, and the environment, they show, underscores the urgency of developing robust tools and methods to understand how a material designed to make life easier may be making it increasingly unsustainable.

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Pollution is the introduction of harmful materials into the environment. These harmful materials are called pollutants.

Biology, Ecology, Health, Earth Science, Geography

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Pollution is the introduction of harmful materials into the environment . These harmful materials are called pollutants . Pollutants can be natural, such as volcanic ash . They can also be created by human activity, such as trash or runoff produced by factories. Pollutants damage the quality of air, water, and land. Many things that are useful to people produce pollution. Cars spew pollutants from their exhaust pipes. Burning coal to create electricity pollutes the air. Industries and homes generate garbage and sewage that can pollute the land and water. Pesticides —chemical poisons used to kill weeds and insects— seep into waterways and harm wildlife . All living things—from one-celled microbes to blue whales—depend on Earth ’s supply of air and water. When these resources are polluted, all forms of life are threatened. Pollution is a global problem. Although urban areas are usually more polluted than the countryside, pollution can spread to remote places where no people live. For example, pesticides and other chemicals have been found in the Antarctic ice sheet . In the middle of the northern Pacific Ocean, a huge collection of microscopic plastic particles forms what is known as the Great Pacific Garbage Patch . Air and water currents carry pollution. Ocean currents and migrating fish carry marine pollutants far and wide. Winds can pick up radioactive material accidentally released from a nuclear reactor and scatter it around the world. Smoke from a factory in one country drifts into another country. In the past, visitors to Big Bend National Park in the U.S. state of Texas could see 290 kilometers (180 miles) across the vast landscape . Now, coal-burning power plants in Texas and the neighboring state of Chihuahua, Mexico have spewed so much pollution into the air that visitors to Big Bend can sometimes see only 50 kilometers (30 miles). The three major types of pollution are air pollution , water pollution , and land pollution . Air Pollution Sometimes, air pollution is visible . A person can see dark smoke pour from the exhaust pipes of large trucks or factories, for example. More often, however, air pollution is invisible . Polluted air can be dangerous, even if the pollutants are invisible. It can make people’s eyes burn and make them have difficulty breathing. It can also increase the risk of lung cancer . Sometimes, air pollution kills quickly. In 1984, an accident at a pesticide plant in Bhopal, India, released a deadly gas into the air. At least 8,000 people died within days. Hundreds of thou sands more were permanently injured. Natural disasters can also cause air pollution to increase quickly. When volcanoes erupt , they eject volcanic ash and gases into the atmosphere . Volcanic ash can discolor the sky for months. After the eruption of the Indonesian volcano of Krakatoa in 1883, ash darkened the sky around the world. The dimmer sky caused fewer crops to be harvested as far away as Europe and North America. For years, meteorologists tracked what was known as the “equatorial smoke stream .” In fact, this smoke stream was a jet stream , a wind high in Earth’s atmosphere that Krakatoa’s air pollution made visible. Volcanic gases , such as sulfur dioxide , can kill nearby residents and make the soil infertile for years. Mount Vesuvius, a volcano in Italy, famously erupted in 79, killing hundreds of residents of the nearby towns of Pompeii and Herculaneum. Most victims of Vesuvius were not killed by lava or landslides caused by the eruption. They were choked, or asphyxiated , by deadly volcanic gases. In 1986, a toxic cloud developed over Lake Nyos, Cameroon. Lake Nyos sits in the crater of a volcano. Though the volcano did not erupt, it did eject volcanic gases into the lake. The heated gases passed through the water of the lake and collected as a cloud that descended the slopes of the volcano and into nearby valleys . As the toxic cloud moved across the landscape, it killed birds and other organisms in their natural habitat . This air pollution also killed thousands of cattle and as many as 1,700 people. Most air pollution is not natural, however. It comes from burning fossil fuels —coal, oil , and natural gas . When gasoline is burned to power cars and trucks, it produces carbon monoxide , a colorless, odorless gas. The gas is harmful in high concentrations , or amounts. City traffic produces highly concentrated carbon monoxide. Cars and factories produce other common pollutants, including nitrogen oxide , sulfur dioxide, and hydrocarbons . These chemicals react with sunlight to produce smog , a thick fog or haze of air pollution. The smog is so thick in Linfen, China, that people can seldom see the sun. Smog can be brown or grayish blue, depending on which pollutants are in it. Smog makes breathing difficult, especially for children and older adults. Some cities that suffer from extreme smog issue air pollution warnings. The government of Hong Kong, for example, will warn people not to go outside or engage in strenuous physical activity (such as running or swimming) when smog is very thick.

When air pollutants such as nitrogen oxide and sulfur dioxide mix with moisture, they change into acids . They then fall back to earth as acid rain . Wind often carries acid rain far from the pollution source. Pollutants produced by factories and power plants in Spain can fall as acid rain in Norway. Acid rain can kill all the trees in a forest . It can also devastate lakes, streams, and other waterways. When lakes become acidic, fish can’t survive . In Sweden, acid rain created thousands of “ dead lakes ,” where fish no longer live. Acid rain also wears away marble and other kinds of stone . It has erased the words on gravestones and damaged many historic buildings and monuments . The Taj Mahal , in Agra, India, was once gleaming white. Years of exposure to acid rain has left it pale. Governments have tried to prevent acid rain by limiting the amount of pollutants released into the air. In Europe and North America, they have had some success, but acid rain remains a major problem in the developing world , especially Asia. Greenhouse gases are another source of air pollution. Greenhouse gases such as carbon dioxide and methane occur naturally in the atmosphere. In fact, they are necessary for life on Earth. They absorb sunlight reflected from Earth, preventing it from escaping into space. By trapping heat in the atmosphere, they keep Earth warm enough for people to live. This is called the greenhouse effect . But human activities such as burning fossil fuels and destroying forests have increased the amount of greenhouse gases in the atmosphere. This has increased the greenhouse effect, and average temperatures across the globe are rising. The decade that began in the year 2000 was the warmest on record. This increase in worldwide average temperatures, caused in part by human activity, is called global warming . Global warming is causing ice sheets and glaciers to melt. The melting ice is causing sea levels to rise at a rate of two millimeters (0.09 inches) per year. The rising seas will eventually flood low-lying coastal regions . Entire nations, such as the islands of Maldives, are threatened by this climate change . Global warming also contributes to the phenomenon of ocean acidification . Ocean acidification is the process of ocean waters absorbing more carbon dioxide from the atmosphere. Fewer organisms can survive in warmer, less salty waters. The ocean food web is threatened as plants and animals such as coral fail to adapt to more acidic oceans. Scientists have predicted that global warming will cause an increase in severe storms . It will also cause more droughts in some regions and more flooding in others. The change in average temperatures is already shrinking some habitats, the regions where plants and animals naturally live. Polar bears hunt seals from sea ice in the Arctic. The melting ice is forcing polar bears to travel farther to find food , and their numbers are shrinking. People and governments can respond quickly and effectively to reduce air pollution. Chemicals called chlorofluorocarbons (CFCs) are a dangerous form of air pollution that governments worked to reduce in the 1980s and 1990s. CFCs are found in gases that cool refrigerators, in foam products, and in aerosol cans . CFCs damage the ozone layer , a region in Earth’s upper atmosphere. The ozone layer protects Earth by absorbing much of the sun’s harmful ultraviolet radiation . When people are exposed to more ultraviolet radiation, they are more likely to develop skin cancer, eye diseases, and other illnesses. In the 1980s, scientists noticed that the ozone layer over Antarctica was thinning. This is often called the “ ozone hole .” No one lives permanently in Antarctica. But Australia, the home of more than 22 million people, lies at the edge of the hole. In the 1990s, the Australian government began an effort to warn people of the dangers of too much sun. Many countries, including the United States, now severely limit the production of CFCs. Water Pollution Some polluted water looks muddy, smells bad, and has garbage floating in it. Some polluted water looks clean, but is filled with harmful chemicals you can’t see or smell. Polluted water is unsafe for drinking and swimming. Some people who drink polluted water are exposed to hazardous chemicals that may make them sick years later. Others consume bacteria and other tiny aquatic organisms that cause disease. The United Nations estimates that 4,000 children die every day from drinking dirty water. Sometimes, polluted water harms people indirectly. They get sick because the fish that live in polluted water are unsafe to eat. They have too many pollutants in their flesh. There are some natural sources of water pollution. Oil and natural gas, for example, can leak into oceans and lakes from natural underground sources. These sites are called petroleum seeps . The world’s largest petroleum seep is the Coal Oil Point Seep, off the coast of the U.S. state of California. The Coal Oil Point Seep releases so much oil that tar balls wash up on nearby beaches . Tar balls are small, sticky pieces of pollution that eventually decompose in the ocean.

Human activity also contributes to water pollution. Chemicals and oils from factories are sometimes dumped or seep into waterways. These chemicals are called runoff. Chemicals in runoff can create a toxic environment for aquatic life. Runoff can also help create a fertile environment for cyanobacteria , also called blue-green algae . Cyanobacteria reproduce rapidly, creating a harmful algal bloom (HAB) . Harmful algal blooms prevent organisms such as plants and fish from living in the ocean. They are associated with “ dead zones ” in the world’s lakes and rivers, places where little life exists below surface water. Mining and drilling can also contribute to water pollution. Acid mine drainage (AMD) is a major contributor to pollution of rivers and streams near coal mines . Acid helps miners remove coal from the surrounding rocks . The acid is washed into streams and rivers, where it reacts with rocks and sand. It releases chemical sulfur from the rocks and sand, creating a river rich in sulfuric acid . Sulfuric acid is toxic to plants, fish, and other aquatic organisms. Sulfuric acid is also toxic to people, making rivers polluted by AMD dangerous sources of water for drinking and hygiene . Oil spills are another source of water pollution. In April 2010, the Deepwater Horizon oil rig exploded in the Gulf of Mexico, causing oil to gush from the ocean floor. In the following months, hundreds of millions of gallons of oil spewed into the gulf waters. The spill produced large plumes of oil under the sea and an oil slick on the surface as large as 24,000 square kilometers (9,100 square miles). The oil slick coated wetlands in the U.S. states of Louisiana and Mississippi, killing marsh plants and aquatic organisms such as crabs and fish. Birds, such as pelicans , became coated in oil and were unable to fly or access food. More than two million animals died as a result of the Deepwater Horizon oil spill. Buried chemical waste can also pollute water supplies. For many years, people disposed of chemical wastes carelessly, not realizing its dangers. In the 1970s, people living in the Love Canal area in Niagara Falls, New York, suffered from extremely high rates of cancer and birth defects . It was discovered that a chemical waste dump had poisoned the area’s water. In 1978, 800 families living in Love Canal had to a bandon their homes. If not disposed of properly, radioactive waste from nuclear power plants can escape into the environment. Radioactive waste can harm living things and pollute the water. Sewage that has not been properly treated is a common source of water pollution. Many cities around the world have poor sewage systems and sewage treatment plants. Delhi, the capital of India, is home to more than 21 million people. More than half the sewage and other waste produced in the city are dumped into the Yamuna River. This pollution makes the river dangerous to use as a source of water for drinking or hygiene. It also reduces the river’s fishery , resulting in less food for the local community. A major source of water pollution is fertilizer used in agriculture . Fertilizer is material added to soil to make plants grow larger and faster. Fertilizers usually contain large amounts of the elements nitrogen and phosphorus , which help plants grow. Rainwater washes fertilizer into streams and lakes. There, the nitrogen and phosphorus cause cyanobacteria to form harmful algal blooms. Rain washes other pollutants into streams and lakes. It picks up animal waste from cattle ranches. Cars drip oil onto the street, and rain carries it into storm drains , which lead to waterways such as rivers and seas. Rain sometimes washes chemical pesticides off of plants and into streams. Pesticides can also seep into groundwater , the water beneath the surface of the Earth. Heat can pollute water. Power plants, for example, produce a huge amount of heat. Power plants are often located on rivers so they can use the water as a coolant . Cool water circulates through the plant, absorbing heat. The heated water is then returned to the river. Aquatic creatures are sensitive to changes in temperature. Some fish, for example, can only live in cold water. Warmer river temperatures prevent fish eggs from hatching. Warmer river water also contributes to harmful algal blooms. Another type of water pollution is simple garbage. The Citarum River in Indonesia, for example, has so much garbage floating in it that you cannot see the water. Floating trash makes the river difficult to fish in. Aquatic animals such as fish and turtles mistake trash, such as plastic bags, for food. Plastic bags and twine can kill many ocean creatures. Chemical pollutants in trash can also pollute the water, making it toxic for fish and people who use the river as a source of drinking water. The fish that are caught in a polluted river often have high levels of chemical toxins in their flesh. People absorb these toxins as they eat the fish. Garbage also fouls the ocean. Many plastic bottles and other pieces of trash are thrown overboard from boats. The wind blows trash out to sea. Ocean currents carry plastics and other floating trash to certain places on the globe, where it cannot escape. The largest of these areas, called the Great Pacific Garbage Patch, is in a remote part of the Pacific Ocean. According to some estimates, this garbage patch is the size of Texas. The trash is a threat to fish and seabirds, which mistake the plastic for food. Many of the plastics are covered with chemical pollutants. Land Pollution Many of the same pollutants that foul the water also harm the land. Mining sometimes leaves the soil contaminated with dangerous chemicals. Pesticides and fertilizers from agricultural fields are blown by the wind. They can harm plants, animals, and sometimes people. Some fruits and vegetables absorb the pesticides that help them grow. When people consume the fruits and vegetables, the pesticides enter their bodies. Some pesticides can cause cancer and other diseases. A pesticide called DDT (dichlorodiphenyltrichloroethane) was once commonly used to kill insects, especially mosquitoes. In many parts of the world, mosquitoes carry a disease called malaria , which kills a million people every year. Swiss chemist Paul Hermann Muller was awarded the Nobel Prize for his understanding of how DDT can control insects and other pests. DDT is responsible for reducing malaria in places such as Taiwan and Sri Lanka. In 1962, American biologist Rachel Carson wrote a book called Silent Spring , which discussed the dangers of DDT. She argued that it could contribute to cancer in humans. She also explained how it was destroying bird eggs, which caused the number of bald eagles, brown pelicans, and ospreys to drop. In 1972, the United States banned the use of DDT. Many other countries also banned it. But DDT didn’t disappear entirely. Today, many governments support the use of DDT because it remains the most effective way to combat malaria. Trash is another form of land pollution. Around the world, paper, cans, glass jars, plastic products, and junked cars and appliances mar the landscape. Litter makes it difficult for plants and other producers in the food web to create nutrients . Animals can die if they mistakenly eat plastic. Garbage often contains dangerous pollutants such as oils, chemicals, and ink. These pollutants can leech into the soil and harm plants, animals, and people. Inefficient garbage collection systems contribute to land pollution. Often, the garbage is picked up and brought to a dump, or landfill . Garbage is buried in landfills. Sometimes, communities produce so much garbage that their landfills are filling up. They are running out of places to dump their trash. A massive landfill near Quezon City, Philippines, was the site of a land pollution tragedy in 2000. Hundreds of people lived on the slopes of the Quezon City landfill. These people made their living from recycling and selling items found in the landfill. However, the landfill was not secure. Heavy rains caused a trash landslide, killing 218 people. Sometimes, landfills are not completely sealed off from the land around them. Pollutants from the landfill leak into the earth in which they are buried. Plants that grow in the earth may be contaminated, and the herbivores that eat the plants also become contaminated. So do the predators that consume the herbivores. This process, where a chemical builds up in each level of the food web, is called bioaccumulation . Pollutants leaked from landfills also leak into local groundwater supplies. There, the aquatic food web (from microscopic algae to fish to predators such as sharks or eagles) can suffer from bioaccumulation of toxic chemicals. Some communities do not have adequate garbage collection systems, and trash lines the side of roads. In other places, garbage washes up on beaches. Kamilo Beach, in the U.S. state of Hawai'i, is littered with plastic bags and bottles carried in by the tide . The trash is dangerous to ocean life and reduces economic activity in the area. Tourism is Hawai'i’s largest industry . Polluted beaches discourage tourists from investing in the area’s hotels, restaurants, and recreational activities. Some cities incinerate , or burn, their garbage. Incinerating trash gets rid of it, but it can release dangerous heavy metals and chemicals into the air. So while trash incinerators can help with the problem of land pollution, they sometimes add to the problem of air pollution. Reducing Pollution Around the world, people and governments are making efforts to combat pollution. Recycling, for instance, is becoming more common. In recycling, trash is processed so its useful materials can be used again. Glass, aluminum cans, and many types of plastic can be melted and reused . Paper can be broken down and turned into new paper. Recycling reduces the amount of garbage that ends up in landfills, incinerators, and waterways. Austria and Switzerland have the highest recycling rates. These nations recycle between 50 and 60 percent of their garbage. The United States recycles about 30 percent of its garbage. Governments can combat pollution by passing laws that limit the amount and types of chemicals factories and agribusinesses are allowed to use. The smoke from coal-burning power plants can be filtered. People and businesses that illegally dump pollutants into the land, water, and air can be fined for millions of dollars. Some government programs, such as the Superfund program in the United States, can force polluters to clean up the sites they polluted. International agreements can also reduce pollution. The Kyoto Protocol , a United Nations agreement to limit the emission of greenhouse gases, has been signed by 191 countries. The United States, the world’s second-largest producer of greenhouse gases, did not sign the agreement. Other countries, such as China, the world’s largest producer of greenhouse gases, have not met their goals. Still, many gains have been made. In 1969, the Cuyahoga River, in the U.S. state of Ohio, was so clogged with oil and trash that it caught on fire. The fire helped spur the Clean Water Act of 1972. This law limited what pollutants could be released into water and set standards for how clean water should be. Today, the Cuyahoga River is much cleaner. Fish have returned to regions of the river where they once could not survive. But even as some rivers are becoming cleaner, others are becoming more polluted. As countries around the world become wealthier, some forms of pollution increase. Countries with growing economies usually need more power plants, which produce more pollutants. Reducing pollution requires environmental, political, and economic leadership. Developed nations must work to reduce and recycle their materials, while developing nations must work to strengthen their economies without destroying the environment. Developed and developing countries must work together toward the common goal of protecting the environment for future use.

How Long Does It Last? Different materials decompose at different rates. How long does it take for these common types of trash to break down?

• Paper: 2-4 weeks
• Orange peel: 6 months
• Milk carton: 5 years
• Plastic bag: 15 years
• Tin can: 100 years
• Plastic bottle: 450 years
• Glass bottle: 500 years
• Styrofoam: Never

Indoor Air Pollution The air inside your house can be polluted. Air and carpet cleaners, insect sprays, and cigarettes are all sources of indoor air pollution.

Light Pollution Light pollution is the excess amount of light in the night sky. Light pollution, also called photopollution, is almost always found in urban areas. Light pollution can disrupt ecosystems by confusing the distinction between night and day. Nocturnal animals, those that are active at night, may venture out during the day, while diurnal animals, which are active during daylight hours, may remain active well into the night. Feeding and sleep patterns may be confused. Light pollution also indicates an excess use of energy. The dark-sky movement is a campaign by people to reduce light pollution. This would reduce energy use, allow ecosystems to function more normally, and allow scientists and stargazers to observe the atmosphere.

Noise Pollution Noise pollution is the constant presence of loud, disruptive noises in an area. Usually, noise pollution is caused by construction or nearby transportation facilities, such as airports. Noise pollution is unpleasant, and can be dangerous. Some songbirds, such as robins, are unable to communicate or find food in the presence of heavy noise pollution. The sound waves produced by some noise pollutants can disrupt the sonar used by marine animals to communicate or locate food.

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EPA Research: Environmental Justice and Air Pollution

Clean air is important for everyone’s health. Yet, studies show that many people are disproportionately impacted by air pollution, including those who live in communities of color and low-income communities. Exposure to poor air quality has been found to cause short and long-term health effects, especially for older adults, children and pregnant women. The health burden of air pollution is higher for those living in areas of poor air quality. Residents of low-income neighborhoods and communities may be more vulnerable to air pollution because of proximity to air pollution sources such as factories, major roadways and ports with diesel truck operations. They also may be more susceptible to air pollution because of social and economic factors.

Research at EPA is contributing to a better understanding of the relationship between poor air quality and health disparities and investigating who is most vulnerable. The findings can help to mitigate pollution and assist with developing strategies to reduce the impacts of poor air quality on health. In addition, this work seeks to empower communities with the tools and information to measure and monitor their own air quality. This includes evaluating commercial, low-cost air sensors for public use, and developing online toolkits and mobile applications to empower citizen and community science projects.

EPA’s research linking environmental justice and air pollution includes:

Disproportionate Health Effects of Air Pollutants

Research has shown that certain populations are more susceptible than others to air pollutants. Residents of low-income communities may experience increased health impacts from air pollution due to many environmental, social, and economic factors. Researchers are working to better understand the factors that contribute to air pollution health disparities, such as sociodemographic factors, how diet modifies responses to air pollution, and the effect of chronic disease on respiratory and cardiovascular responses to air pollution.

• Research on Health Effects of Air Pollution

Near-source Air Pollution

Living near sources of air pollution including major roadways, ports, rail yards, and industrial facilities can lead to health effects like asthma, reduced lung function, cardiovascular disease, and premature death. Children, older adults, people with pre-existing cardiopulmonary disease, and people living in low-income communities are especially at risk for health impacts associated with near-source air pollution. Researchers are conducting studies and modeling to:

• Assess near-source impacts for single source and complex multi-source environments.
• Understand factors influencing adverse health effects attributed to near-source impacts.
• Develop models and tools to quantify near-source emissions and exposures to guide community planning.
• Develop mitigation strategies to reduce emissions, exposures, and health effects.

Near Source Air Pollution Research

Air Quality Monitoring Tools for Communities

Researchers are working to provide air quality monitoring tools and resources for citizen science and community air monitoring projects. These efforts include evaluating commercial, low-cost air sensors for accuracy and quality; providing guidance for understanding air sensor data; bringing air sensor technology to communities through sensor loan programs; and developing a mobile application for reporting odors related to air pollutant emissions.

• Air Sensor Toolbox
• Odor Explore

Public Health Intervention and Communication Strategies

Researchers are studying intervention strategies to reduce health impacts from exposure to air pollutants from vehicle and industrial emissions, as well as wildfire smoke. EPA is collaborating with other federal agencies, state and local agencies, and tribes to translate the science for public health communication and community empowerment. This work includes studies to evaluate the behavioral, social, and economic factors that may influence health outcomes in order to inform effective health risk messaging.

• Smoke Sense Project and App
• Healthy Heart Initiative and Research

Reducing Wildfire Smoke Exposure

As climate change drives more frequent and larger wildfires, more people are being exposed to dangerous smoke from fires. Researchers are studying ways communities can be smoke-ready and prepare for wildfire smoke. Research underway includes testing commercial and more accessible, do-it-yourself air filtering devices to remove smoke from indoor areas. In addition, partnerships with outside experts are resulting in guidance to reduce smoke in commercial buildings and schools by preparing HVAC systems for smoke. Researchers are also working to improve health risk communication to various groups about smoke exposure before and during wildfires, reducing the public health burden of smoke episodes.

• Wildland Fire Research
• Smoke-Ready Toolbox for Wildfires
• Helping Environmental Justice Take Root
• Health Disparities and Risks
• Environmental Justice and Air Pollution
• Environmental Justice and Contaminated Sites
• Developing Decision Support Tools

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Environmental Changes Are Fueling Human, Animal and Plant Diseases, Study Finds

Biodiversity loss, global warming, pollution and the spread of invasive species are making infectious diseases more dangerous to organisms around the world.

By Emily Anthes

Several large-scale, human-driven changes to the planet — including climate change, the loss of biodiversity and the spread of invasive species — are making infectious diseases more dangerous to people, animals and plants, according to a new study.

Scientists have documented these effects before in more targeted studies that have focused on specific diseases and ecosystems. For instance, they have found that a warming climate may be helping malaria expand in Africa and that a decline in wildlife diversity may be boosting Lyme disease cases in North America.

But the new research, a meta-analysis of nearly 1,000 previous studies, suggests that these patterns are relatively consistent around the globe and across the tree of life.

“It’s a big step forward in the science,” said Colin Carlson, a biologist at Georgetown University, who was not an author of the new analysis. “This paper is one of the strongest pieces of evidence that I think has been published that shows how important it is health systems start getting ready to exist in a world with climate change, with biodiversity loss.”

In what is likely to come as a more surprising finding, the researchers also found that urbanization decreased the risk of infectious disease.

The new analysis, which was published in Nature on Wednesday, focused on five “global change drivers” that are altering ecosystems across the planet: biodiversity change, climate change, chemical pollution, the introduction of nonnative species and habitat loss or change.

The researchers compiled data from scientific papers that examined how at least one of these factors affected various infectious-disease outcomes, such as severity or prevalence. The final data set included nearly 3,000 observations on disease risks for humans, animals and plants on every continent except for Antarctica.

The researchers found that, across the board, four of the five trends they studied — biodiversity change, the introduction of new species, climate change and chemical pollution — tended to increase disease risk.

“It means that we’re likely picking up general biological patterns,” said Jason Rohr, an infectious disease ecologist at the University of Notre Dame and senior author of the study. “It suggests that there are similar sorts of mechanisms and processes that are likely occurring in plants, animals and humans.”

The loss of biodiversity played an especially large role in driving up disease risk, the researchers found. Many scientists have posited that biodiversity can protect against disease through a phenomenon known as the dilution effect.

The theory holds that parasites and pathogens, which rely on having abundant hosts in order to survive, will evolve to favor species that are common, rather than those that are rare, Dr. Rohr said. And as biodiversity declines, rare species tend to disappear first. “That means that the species that remain are the competent ones, the ones that are really good at transmitting disease,” he said.

Lyme disease is one oft-cited example. White-footed mice, which are the primary reservoir for the disease, have become more dominant on the landscape, as other rarer mammals have disappeared, Dr. Rohr said. That shift may partly explain why Lyme disease rates have risen in the United States. (The extent to which the dilution effect contributes to Lyme disease risk has been the subject of debate, and other factors, including climate change, are likely to be at play as well.)

Other environmental changes could amplify disease risks in a wide variety of ways. For instance, introduced species can bring new pathogens with them, and chemical pollution can stress organisms’ immune systems. Climate change can alter animal movements and habitats, bringing new species into contact and allowing them to swap pathogens .

Notably, the fifth global environmental change that the researchers studied — habitat loss or change — appeared to reduce disease risk. At first glance, the findings might appear to be at odds with previous studies, which have shown that deforestation can increase the risk of diseases ranging from malaria to Ebola. But the overall trend toward reduced risk was driven by one specific type of habitat change: increasing urbanization.

The reason may be that urban areas often have better sanitation and public health infrastructure than rural ones — or simply because there are fewer plants and animals to serve as disease hosts in urban areas. The lack of plant and animal life is “not a good thing,” Dr. Carlson said. “And it also doesn’t mean that the animals that are in the cities are healthier.”

And the new study does not negate the idea that forest loss can fuel disease; instead, deforestation increases risk in some circumstances and reduces it in others, Dr. Rohr said.

Indeed, although this kind of meta-analysis is valuable for revealing broad patterns, it can obscure some of the nuances and exceptions that are important for managing specific diseases and ecosystems, Dr. Carlson noted.

Moreover, most of the studies included in the analysis examined just a single global change drive. But, in the real world, organisms are contending with many of these stressors simultaneously. “The next step is to better understand the connections among them,” Dr. Rohr said.

Emily Anthes is a science reporter, writing primarily about animal health and science. She also covered the coronavirus pandemic. More about Emily Anthes

Explore the Animal Kingdom

A selection of quirky, intriguing and surprising discoveries about animal life..

Indigenous rangers in Australia’s Western Desert got a rare close-up with the northern marsupial mole , which is tiny, light-colored and blind, and almost never comes to the surface.

For the first time, scientists observed an orangutan, a primate, in the wild treating a wound  with a plant that has medicinal properties.

A new study resets the timing for the emergence of bioluminescence back to millions  of years earlier than previously thought.

Scientists are making computer models to better understand how cicadas  emerge collectively after more than a decade underground .

New research questions the long-held theory that reintroduction of Yellowstone’s wolves caused a trophic cascade , spawning renewal of vegetation and spurring biodiversity.

To protect Australia’s iconic animals, scientists are experimenting with vaccine implants , probiotics, tree-planting drones and solar-powered tracking tags.

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Plastic pollution

• Over 460 million metric tons of plastic are produced every year for use in a wide variety of applications. 
• An estimated 20 million metric tons of plastic litter end up in the environment every year. That amount is expected to increase significantly by 2040.
• Plastic pollution affects all land, freshwater, and marine ecosystems . It is a major driver of biodiversity loss and ecosystem degradation and contributes to climate change.
• As plastic pollution is a transboundary issue, a global plastics treaty is needed to ambitiously reduce plastic production, phase out harmful subsidies, eliminate products and chemicals of concern, and adopt strong national plans and rigorous reporting and compliance mechanisms.

All land, freshwater, and marine ecosystems are affected by plastic pollution.

What is the issue? 

Plastic is a synthetic, organic polymer made from fossil fuels, such as gas and petroleum. Over 460 million metric tons of plastic are produced every year , according to the United Nations Environment Programme . Plastic is used in almost all consumer and industrial activities, from construction and vehicles to electronics and agriculture. 

Discarded improperly, plastic waste pollutes and harms the environment , becoming a widespread driver of biodiversity loss and ecosystem degradation. It threatens human health, affects food and water safety, burdens economic activities, and contributes to climate change.

Macro-plastics (pieces larger than 0.5 mm) made up 88% of global plastic leakage to the environment in 2019, around 20 million metric tons, polluting all ecosystems. Much of the world’s plastic pollution is generated by single-use products such as bottles, caps, cigarettes, shopping bags, cups, and straws.

Pollution sources are mainly land-based , coming from urban and stormwater runoff, littering, industrial activities, tyre abrasion, construction, and agriculture. In the marine environment, plastic pollution originates primarily from land runoff, but includes paint shed from shipping, discarded fishing gear, and more.

Due to solar radiation, wind, currents and other natural factors, plastic breaks down into microplastic (smaller than 5 mm) and nanoplastic (smaller than 100 nm) particles . ‘Primary’ microplastic particles are also shed by products such as synthetic textiles and tyres, through abrasion. Nanoplastics are able to cross cell membrane walls and enter living organisms. 

Many nations lack the capacities and facilities to properly manage plastic products and waste , and the burden often falls on the local level. That impact is disproportionately felt by islands, developing countries, Indigenous peoples, local communities, women, and children. This problem is deepened by the global trade of plastic products and waste to locations where infrastructure is not sufficient for safe and environmentally sound management.  

Why is it important?

Impacts on human health Microplastics have been found in human blood and placentas and in food and drinks , including tap water, beer, and salt. Several chemicals used in the production of plastic materials are known to be carcinogenic and can cause developmental, reproductive, neurological, and immune disorders. 

Impacts on economies The build-up of plastic litter can have a negative impact on aspects of a country’s economy and trade systems , with income declines in sectors such as small- and medium-enterprises, the informal sector, tourism, fisheries, agriculture, and water safety. IUCN’s research on these economic impacts demonstrates examples and possible solutions.

Impacts on species and ecosystems All land, freshwater, and marine ecosystems are affected by plastic pollution. Natural ecosystems provide a broad range of services that are not only fundamental for conservation, but also key for economies and human well-being. For example, healthy mangroves provide coastal protection services, whereas wetlands are important for freshwater provision.

The most visible impacts of plastic debris are the ingestion, suffocation, and entanglement of species. Wildlife such as birds, whales, fish, and turtles mistake indigestible plastic waste for food and die of starvation as their stomachs become filled with it. It also causes internal and external injuries that reduce the ability to swim and fly. Domesticated farm animals are also affected by plastic pollution. Floating plastics transport invasive alien species , one of the leading causes of biodiversity loss and species extinction.

Plastic pollution can also seep carcinogenic chemicals (such as those contained in certain plastic products or fireproofing coatings) into the soil. These can run into groundwater or rivers, affecting exposed people and ecosystems.

Impacts on climate Climate impacts begin with oil and gas extraction, the refining of these products into plastics, and then plastic pollution itself. Incinerated plastic waste releases greenhouse gases and other pollutants into the atmosphere, including carbon dioxide, dioxins, and methane.  

What can be done?

The removal of legacy plastics and prevention of pollution requires that fewer plastic products be made, that the circularity of supply and value chains be increased, and that consumer behaviour be changed. It also involves public and private investment and the development of infrastructure along the full lifecycle of plastics, including circular economy solutions like reuse, refill, etc.

Despite positive efforts from countries to tackle plastic pollution, such as bans on certain forms of single-use plastics, a global plastics treaty is essential because plastic pollution is transboundary and a main driver of biodiversity loss.

To best address the triple planetary crisis and ensure the proper implementation of the Global Biodiversity Framework (GBF); the Paris Agreement; the Sustainable Development Goals (SDGs); and initiatives under the broader chemicals, waste, and pollution agenda; a future plastics treaty needs a common approach and requires collective action on a global scale.

Biodiversity has come to play a prominent role in international law, including in multilateral environmental agreements. A focus on the connections between plastic pollution, biodiversity loss, and the degradation of ecosystems at the global, regional, and national levels is important for effective action. The protection and restoration of biodiversity, and nature per se , must be incorporated in the legally binding control measures and enforcement terms of a future treaty.

To address plastic pollution globally, IUCN supports:

• Ambitious reductions in plastic production, phasing out harmful subsidies, eliminating products and chemicals of concern, and agreeing on the adoption of strong national plans, reporting requirements, and compliance mechanisms.
• Measurable and ecologically sustainable objectives, targets, and actions.
• An inclusive, just, and gender-responsive process and effective and science-based nature-positive frameworks, including a global treaty.
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Development of an environmentally foamed concrete incorporating red mud

• Research Article
• Published: 10 May 2024

Cite this article

• Dongyu Chen 1 ,
• Meizhu Chen 1 ,
• Xinkui Yang 1 ,
• Yuechao Zhao 1 ,
• Yunlong Zhang 1 &
• Jianwei Zhang 1  

In this work, an efficient utilization method for red mud (RM) is provided through recycling RM as a mineral admixture for the preparation of foamed concrete (FC). Specifically, FC with different RM contents was prepared and investigated in terms of workability, mechanical properties, and hydration products. Results show that adding RM can significantly shorten the setting time, while it inevitably weakens the mechanical properties and fluidity of FC. However, the compressive strength of FC can still meet the strength predicted by the specification requirements when the RM replaces cement with 60% content (3d > 1.6 MPa). Most importantly, the heavy metals leaching from RM-based FC under the action of rain is still unclear, so a device for simulating stormwater runoff was designed to test the heavy metal leaching risk of RM-based FC. The findings indicate that the solidification of cement and the high basicity of the matrix can effectively reduce the leaching risk of heavy metals from RM in FC. Although the pore structure analysis demonstrates that the porosity and connected pores of FC will be deteriorated as RM concentration increases. The results are of great significance for the recycling of waste and the sustainable development of building materials.

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Dongyu Chen, Meizhu Chen, Xinkui Yang, Yuechao Zhao, Yunlong Zhang & Jianwei Zhang

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Chen Dongyu: writing—original draft preparation; writing—reviewing and editing. Chen Meizhu: project administration, visualization and supervision, funding acquisition. Yang Xinkui: investigation. Zhao Yuechao: visualization and supervision. Zhang Yunlong: investigation and experiment. Zhang Jianwei: investigation.

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Chen, D., Chen, M., Yang, X. et al. Development of an environmentally foamed concrete incorporating red mud. Environ Sci Pollut Res (2024). https://doi.org/10.1007/s11356-024-33587-1

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• Published: 07 May 2024

Strong economic incentives of ship scrubbers promoting pollution

• Anna Lunde Hermansson   ORCID: orcid.org/0000-0003-2386-7742 1 ,
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In response to stricter regulations on ship air emissions, many shipowners have installed exhaust gas cleaning systems, known as scrubbers, allowing for use of cheap residual heavy fuel oil. Scrubbers produce large volumes of acidic and polluted water that is discharged to the sea. Due to environmental concerns, the use of scrubbers is being discussed within the International Maritime Organization. Real-world simulations of global scrubber-vessel activity, applying actual fuel costs and expenses related to scrubber operations, show that 51% of the global scrubber-fitted fleet reached economic break even by the end of 2022, with a surplus of €4.7 billion in 2019 euros. Within five years after installation, more than 95% of the ships with the most common scrubber systems reach break even. However, the marine ecotoxicity damage cost, from scrubber water discharge in the Baltic Sea Area 2014–2022, amounts to >€680 million in 2019 euros, showing that private economic interests come at the expense of marine environmental damage.

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Since the mid 1900s, the marine bunker fuel market has been dominated by residual fuels, that is, heavy fuel oils (HFOs), due to their low price and high energy content 1 . HFO is a residual, sulfur-containing product, and during combustion, the sulfur content of the fuel will be proportional to the emissions of sulfur oxides (SO x ) and particulate matter (PM) to the atmosphere. Therefore, as of January 2020, the International Maritime Organization (IMO) implemented stricter global regulations regarding the sulfur content of marine fuels, from a maximum of 3.5% to 0.5%, with the goal to reduce the negative impacts of ship-derived SO x and PM on air quality 2 . Even stricter regulations apply for ships operating in designated sulfur emission control areas (SECAs), where a maximum sulfur content of 0.1% is allowed. To meet sulfur regulations, most ships have switched to the more expensive low-sulfur fuels such as distillate fuels, for example, Marine Gas Oil (MGO), or hybrid fuels, for example, very low-sulfur fuel oils (VLSFOs). Another option is to install exhaust gas cleaning systems (EGCSs), also known as scrubbers, and continue to use the less-expensive HFO with high sulfur content while still being compliant with the IMO regulations. For more than a decade, several studies have shown that more stringent regulations, previously in SECAs and now also globally, have led to a reduction of SO x emissions 3 , 4 , 5 , 6 , that scrubbers efficiently can reduce the sulfur content in the exhaust to the required compliance levels 7 , 8 and that scrubbers are economically feasible, being a lucrative alternative to fuel switch 9 , 10 , 11 , 12 . In parallel, concerns have been raised regarding the impact on the marine environment from scrubber water discharge, for example, adverse effects on marine organisms, including reduced growth and increased mortality potential, eutrophication effects on phytoplankton 13 , 14 , 15 , 16 , 17 and acidification effects on local and regional levels 5 , 18 , 19 . Other concerns related to scrubbers include the difficulty in compliance monitoring 20 , 21 , the PM air emissions that are not reduced in the same way as a switch to low-sulfur fuels 22 and the enabling of continued use of HFO, impeding important development of alternative fuels and other low-carbon options 23 . Globally, scrubbers have been installed on more than 5,000 ships ( https://afi.dnv.com/statistics/ ) and HFO amounts to approximately 25% of the total marine bunker fuel demand and is forecasted to continue to do so in the near future 24 . The market share of fossil fuels, and implicitly scrubbers, may see changes in the medium term with the new ambitions set out by IMO to reduce the greenhouse gas emissions from international shipping to (close to) net zero by 2050 25 . Also, the ‘ Fit for 55 ’ strategy, within the European Green Deal, commits to include shipping in the EU Emission Trading System from 2024 and to implement the FuelEU Maritime initiative to mandate transition to low-carbon fuels 26 .

In the most common scrubber set-up, the open loop, the exhaust gas is led through a fine spray of seawater inside the scrubber. The SO x in the exhaust gas readily dissolves and reacts with the alkaline water forming sulfuric acid. The process implies an hourly production and discharge of hundreds of cubic metres of acidic (pH ≈ 3–4) and polluted (containing, for example, metals, polycyclic aromatic hydrocarbons (PAHs)) scrubber water, which can also have elevated nitrate concentrations due to scavenging of combustion products, that is, nitrogen oxides (NO x ) 27 , 28 , 29 . The process is similar for closed-loop systems (<2% of market share), but the water is recirculated and SO x uptake is ensured by the addition of a strong base (for example, NaOH), resulting in smaller volumes being discharged (on average, 0.45 m 3  MWh −1 ) (refs. 29 , 30 ). Hybrid systems are scrubbers that can operate in both open- and closed-loop mode. An average scrubber water discharge flow rate of approximately 90 m 3  MWh −1 has been reported for open-loop systems, although the highest reported volumes are 140 m 3  MWh −1 (refs. 30 , 31 ). On a global scale, based on pre-pandemic ship traffic patterns and scrubber installations at the end of 2020, the estimated total discharge volume from open-loop scrubbers is approximately 10 billion m 3 per year (ref. 32 ). The emissions of metals and PAHs from ships running on HFO, with or without a scrubber, are substantially higher than ships using MGO as fuel 33 . In addition, a recent study showed ships equipped with scrubbers to account for up to 8.5% of the total input of certain PAHs to the Baltic Sea 34 and that the discharge of scrubber water substantially increases the environmental risk associated with the release of metals and PAHs in port environments 35 .

The necessity of guidelines for environmental risk and impact assessment of scrubber discharge water was acknowledged already in 1998 at the 41st meeting of the Marine Environment Protection Committee (MEPC), a senior technical body of marine pollution issues within the IMO. Since then, many member states have commissioned research and literature reviews of the potential impact of scrubbers on the marine environment. During the 78th MEPC meeting (2022), new guidelines on how to assess risk and impact from scrubber water discharge were approved 36 . The guidelines provide recommendations that member states can use as support when considering stricter discharge regulations. The impact assessment, in section 7.4 of the guidelines, stipulates that the adoption of restrictions or a ban on discharge water from scrubbers should be considered in areas where any of four indicative criteria are fulfilled. The first criterion (paragraph 7.4.1 in the guidelines 36 ) reads ‘environmental objectives in the areas are not met, for example good chemical status, good ecological status or good environmental status are not achieved under applicable legislation’. The three additional criteria are defined with respect to general deterioration of the environment and increased environmental risk, conflicts with conventions and regulations for marine environmental protection and the cost of management of dredged materials in ports 36 .

In Europe, marine environmental objectives, mentioned in indicative criteria 7.4.1, are defined by the Marine Strategy Framework Directive (MSFD), which aims to achieve Good Environmental Status in all of the European marine waters 37 . The first assessment was reported by EU member states in 2018 and when all indicators, reported for each MSFD descriptor (11 in total), are aggregated utilizing the one out all out principle, all but six sea basins fail to achieve Good Environmental Status (Fig. 1 and Supplementary Information A ). As global maritime traffic is forecasted to increase somewhere between 240 and 1,200% by 2050 as compared to 2014 levels 38 , the pressure on the marine environment is likely to increase. At the same time, most of the marine ecosystems are facing increased cumulative impacts where shipping is identified as one of the main stressors 39 .

Aggregated environmental status, considering all descriptors and included indicators, of European sea basins reported to the European Environment Agency Marine Water Information System for Europe database. The result is based on EU member states’ 2018 reporting under the MSFD (2008/56/EC) applying the one out all out principle. More details in Supplementary Information A . Map data from EEA WISE-Marine.

Restrictions or bans on open-loop scrubber water discharge are already adopted in individual ports, inland waters or in territorial waters (for example, Port of Antwerp, Germany inland water, Singapore 40 ) and during the 79th MEPC meeting (2022), the use of scrubbers as an appropriate means of compliance was questioned 41 , 42 . Whereas support for restricting the use of scrubbers exists, there are concerns regarding the (economic) ‘uncertainty for the industry, which has in good faith invested in EGCS technology in accordance with the provisions of MARPOL Annex VI’ 42 . The wide-scale use of scrubbers also imply costs related to the degradation of the marine environment, and the cost of not restricting scrubbers should be factored in the decision-making process 43 .

The overall aim of this study was therefore to investigate several aspects connected to the potential restriction of scrubber water discharge and more specifically (1) to estimate to what extent the global scrubber fleet has reached economic break even on their scrubber installations and the potential monetary gain of using HFO as compared with the more expensive MGO or VLSFO and (2) to assess external costs of not restricting scrubber water discharge by estimating societal damage costs limited to marine ecotoxicity in the Baltic Sea area resulting from nine metals and ten PAHs discharged with scrubber water.

The analyses are based on nine years of real-world simulations of global vessel activity (2014–2022) from the Ship Traffic Emissions Assessment Model (STEAM), version 4.3.0 (ref. 44 ) and references therein. STEAM combines ship location data from automatic identification systems (AIS), fleet technical description and ship-specific modelling of energy consumption and computes emissions to the atmosphere and direct discharges to the marine environment. The output from STEAM is combined with high-resolution fuel price differences from Ship & Bunker ( https://shipandbunker.com/ ) to calculate the ship-specific annual balance from the time the scrubber was installed until the end of 2022 (exemplified in Extended Data Fig. 1 ). A selection of the scrubber fleet, operating within the Baltic Sea area, is further assessed with respect to societal damage cost as an example of the cost of not restricting scrubber water discharge. The societal damage cost associated to marine ecotoxicity from scrubber water discharge is estimated by combining results from a previous willingness-to-pay (WTP) study 45 , 46 with the calculated toxicity potentials of nine metals and ten PAHs (from characterization factors collected from the life cycle impact assessment tool ReCiPe 47 ) that are commonly found in open- and closed-loop scrubber water.

A total of 3,818 unique ships are included in the study (Supplementary Fig. 2 ), of which 3,283 ships (86%) are equipped with open loop, 502 ships (13%) with hybrid and 28 ships (1%) with closed-loop scrubber systems. Most of the scrubber installations (onboard over 2,000 ships) are registered between December 2019 and December 2020. The main ship categories are bulk carriers (36%), container vessels (22%), crude oil and product tankers (26%) and cruise ships (4%) and >90% of the studied scrubber fleet belong to the medium (6,000–15,000 kW installed engine power) and large (>15,000 kW installed engine power) categories.

Economic break-even assessment of the global scrubber fleet

By the end of 2022, the global scrubber fleet that installed scrubbers between 2014 and 2022 has a surplus of €4.7 billion in 2019 euros (€ 2019 ), from installing scrubbers and using HFO instead of MGO (in SECA) or VLSFO (outside SECA since 2020) (median balance scenario in Table 1 ). For the median balance scenario, 51% of the scrubber fleet (1,981 ships) has reached break even with a summarized positive balance of € 2019 7.6 billion by the end of 2022. The ships that have not reached break even by the end of 2022 (1,869 ships, corresponding to 49%) have a summarized negative balance of € 2019 2.9 billion. The total monetary savings from using HFO instead of a more expensive fuel amounts to € 2019 18 billion. The min balance scenario (high costs and low fuel price difference) and the max balance scenario (low costs and high fuel price difference) represent the extremes of realistic favourable (max) and unfavourable (min) conditions from the shipowner perspective.

Within five years from the time of installation, more than 95% of the open-loop systems have reached break even, after which the monetary gain from fuel savings will contribute to the surplus (Fig. 2 ). Thirteen out of the 302 ships that have had their scrubbers installed <1 year (not included in Fig. 2 ) reach break even within the first year of operation (Supplementary Table 5 ). The payback time differs between and within the three scrubber systems and can partly be attributed to the year of installation (Supplementary Figs. 4 – 6 ) and annual fuel consumption, where higher fuel consumption and higher fuel price difference will result in faster payback times. On the contrary, the longer payback times of hybrid and closed-loop scrubbers can be explained by higher investment and operational costs and, for some vessels, lower annual fuel consumption due to smaller engines. The number of ships ( n ) included in the stacked bars in Fig. 2 vary depending on the scrubber type and the number of years since installation, for example, very few ships have had their scrubbers installed for nine years or more (Supplementary Table 5 and Supplementary Figs. 4 – 6 ).

Distribution of vessels that have (orange, bottom part of bar)/have not (red, top part of bar) reached break even within 1–9 years after the installation of scrubber system. The ships included have had their scrubbers installed >1 year. The three panels show the distribution for ships with open loop (upper panel), hybrid (middle panel) and closed-loop (lower panel) scrubbers. n  = the number of ships that are included in the calculation for each year and scrubber type.

Grouping and averaging the annual balance of the vessels that installed their open-loop scrubbers between December 2019 and December 2020 (2020 group, n  = 1,835), it can be expected that 50% reach their point of break even 2.5 years after the investment (Fig. 3 ). The initial balance, that is, the cost of investment, varies between € 2019 2.1 million and 5.1 million, with an average of € 2019 3.1 million, showing good agreement between the 2020 group and the entire open-loop scrubber fleet (Fig. 4b and Supplementary Table 3 ). The small balance change between the start of 2020 and the start of 2021 can be attributed to the relatively small price difference between HFO and low-sulfur fuels during this period (Fig. 4a–c ), where the fuel price, especially for MGO, drops substantially at the beginning of 2020 and remains relatively low until late 2021. During 2022, the fuel prices fluctuate a lot, reaching record-high levels (Fig. 4a ) during 2022, explaining the large spread in balance of the 2020 group of the scrubber fleet (from −€ 2019 1.8 million to 6.4 million; Fig. 3 ), where ships with high fuel consumption would increase their balance substantially. In the median balance scenario for the 2020 group, 953 (52%) ships surpassed their break-even point by the end of 2022 and the surplus amounted to almost € 2019 1.5 billion. The positive balance of the fleet that reach break even before the end of 2022 (€ 2019 2.2 billion) is almost three times higher than the corresponding negative balance of the 878 ships that did not reach break even (−€ 2019 0.8 billion). In the max balance scenario with the 2020 group, all but 47 ships reached break even by the end of 2022 (nearly 50% did so within the first year), and the average surplus amounts to € 2019 9 billion. For the min balance scenario, the higher installation costs (€ 2019 4.1 million–9.2 million) and the low fuel price difference results in a slow increase of the balance, and only 89 ships reach break even by the end of 2022.

Selection of fleet that installed open-loop scrubbers in 2020 or December 2019 ( n tot  = 1,835 ships where 17% were installed in December 2019). The three different scenarios represent max balance (square, dotted-dashed line, red shaded interval), median balance (circle, dashed line, grey shaded interval) and min balance (triangle, dotted line, yellow shaded interval) scenarios. The lines show the average balance of the ships included, and the shaded intervals show the corresponding confidence interval (5th and 95th percentiles). Note the overlap of intervals: as an example, vertical bars on the right show the range of scenarios in 2022.

a , Marine fuel prices (€ 2019 per tonne fuel) from 2014 until 2023 (left y axis, data from Ship & Bunker) and number of scrubbers installed each year (right y axis). b , Investment cost per kW of open- and closed- (hybrid) loop scrubbers based on total installed engine power as ship size categories (small < 6,000 kW; 6,000 kW < medium < 15,000 kW; large > 15,000 kW). c , Annual fuel price difference of MGO − HFO (black, left) and VLSFO − HFO (yellow, right) from 2014 (2020) to 2022 (based on a ). Boxplot shows median (mid line), the box itself represents the 25th–75th percentiles, the whiskers mark the 5th and 95th percentiles and outliers are marked as plus signs.

The cost of not restricting scrubbers in the Baltic Sea

The number of ships equipped with scrubbers in the Baltic Sea area has increased over the years (2014–2022) with a peak of 957 ships in 2020 (Fig. 5a ). In 2022, there were 804 unique vessels that operated with scrubbers in the area. The growing scrubber fleet has paradoxically resulted in an increased HFO consumption in this designated SECA, and since 2015, 9.6 million tonnes of HFO have been used and 3.2 billion m 3 of open-loop scrubber water plus 0.4 million m 3 of closed-loop scrubber water have been discharged within the Baltic Sea area. Most of the contribution (80%) has happened since 2019.

a , Number of vessels with scrubbers installed operating within the Baltic Sea Area 2014–2022. b , Cumulative average damage cost due to environmental deterioration of the marine environment as calculated for marine ecotoxicity based on a WTP study and toxicity potential of open- and closed-loop scrubber water. The error bars indicate the lower and higher estimate of cost where the low (high) WTP estimates are multiplied with the lower (higher) concentration levels of metal ( n  = 9) and PAH ( n  = 10) concentrations in scrubber water (Supplementary Table 7 ).

By combining cost estimates from a WTP study 45 , 46 with toxicity potentials and characterization factors calculated from ReCiPe 47 , the average societal damage cost, limited to marine ecotoxicity, amounts to 0.21 ± 0.07 € 2019 per m 3 of open-loop scrubber water discharge. The average cumulative societal damage cost, by not restricting scrubbers in the Baltic Sea Area since the implementation of SECA in 2015, can thus be estimated to € 2019 680 million (Fig. 5b ). The error bars in Fig. 5b represent the range of low and high cumulative cost, where the low (high) range is based on the lower (higher) level of WTP 45 , 46 combined with the low (high) range of the 95% confidence interval of the metal and PAH concentrations in the scrubber water 33 (Supplementary Tables 4 , 6 and 7 ). From the private perspective, the shipowners have saved more than € 2019 1.7 billion by not switching to the more expensive but less polluting MGO when operating in the Baltic Sea area.

Our assessment, comprising over 3,000 individual ships equipped with scrubbers operating in 2014–2022, shows the strong economic incentives of installing scrubbers. Although the number of ships that have not reached break even constitute almost 50% of the scrubber fleet, the balance calculations show that the positive balance is more than twice as high as the corresponding negative balance, resulting in a scrubber fleet surplus of € 2019 4.7 billion by the end of 2022.

The fuel price difference between MGO and HFO remained relatively stable between 2014 and 2019 although the absolute fuel prices varied over the years (Fig. 4a ). Before the SECA implementation in 2015, due to the fear of increased freight rates, the maritime industry anticipated a modal shift from shipping to land-based transport alternatives 11 . The modal shift was, however, not realized, partly due to the decreasing bunker fuel prices 11 . Analogously, before the global sulfur cap in 2020, the maritime industry was faced with similar concerns resulting in thousands of scrubbers on order with a backlog of up to five months 11 , coinciding with the large peak in scrubber installations in 2020 and the unproportionally large drop in MGO price (Fig. 4a ), possibly connected to the increasing demand of low-sulfur fuels. In addition, the global impact of the COVID-19 pandemic on the demand was the main driver for the 2020 record low fuel prices 11 . Since the mid-2020, the fuel prices and the fuel price differences increased, and the huge variability of 2022 could be explained by the current geopolitical landscape, with Russia’s invasion of Ukraine as a major disruptive event. The large fluctuations in fuel price difference will naturally have major effects on the calculations presented in this work, accentuating the strength of using real-world ship-specific simulations together with high-resolution bunker fuel prices.

During 2023, the fuel price difference has fluctuated but remained high as compared with the annual distributions from 2014 to 2022 (Fig. 4a–c ). For MGO − HFO, the fuel price difference between January and August 2023 range between US$280 and US$600 per tonne fuel, whereas the VLSFO − HFO fuel price difference is lower and ranges between US$70 and US$240 per tonne fuel ( https://shipandbunker.com/ ). This suggests that for the investigated scrubber fleet, more ships will have reached their point of break even by the end of 2023 and the surplus will be even higher. Assuming that each vessel’s fuel consumption for 2023 is equal to the 2022 fuel consumption and that the fuel price difference is € 2019 100 per tonne fuel (for VLSFO − HFO) and € 2019 400 per tonne fuel (for MGO − HFO), an additional 500–1,400 ships in the investigated scrubber fleet would have reached break even by the end of 2023, resulting in a total of 63–86% having reached break even. The assumed fuel price differences in 2023 are lower than in 2022, but the ships that have already installed scrubbers will still reach their point of break even by the end of 2023 due to their relatively small remaining negative balance and the relatively high fuel price difference.

Although the results from the balance calculations might not be absolute for each vessel, this study presents realistic conservative cost estimates of the scrubber fleet on a global level. The three scenarios represent different economic conditions and can capture some of the market variability where the max and min balance scenarios are representing best- and worst-case scenarios from the shipowner perspective. Given the economic incentives of installing scrubbers and the competitiveness of the maritime sector, it is reasonable to assume that the max balance scenario is more likely than the min balance scenario for most ships. If so, the time to reach break even would be shorter than estimated in the median balance scenario, and the 2022 surplus would be higher than € 2019 4.7 billion. Our results show that the majority of the fleet (>51%) already had reached break even by the end of 2022 and are now having an economic advantage due to the lower fuel costs as compared with running their ships on the more expensive low-sulfur fuels.

Due to the lack of integrated global marine status assessments that incorporate economic and social aspects 48 , the cost of not restricting scrubber water discharge was limited to the Baltic Sea area and includes only the aspect of marine ecotoxicity damage cost based on a WTP study 30 , 45 , 46 . The use of scrubbers, that is, a continued use of HFO, will allow ships to run on fuels with higher metal and PAH content 33 than was allowed before the global sulfur cap, resulting in a higher net load of metals and PAHs entering the marine environment 34 . The discharge of scrubber water has been shown to result in adverse effects in marine organisms 13 , 14 , 15 , 16 , 17 and is in direct conflict with the sustainable development goal 14 and especially target 14.1 stating that we shall ‘…prevent and significantly reduce marine pollution of all kinds…’ 49 . Although the external costs in the Baltic Sea case study only include marine ecotoxicity, limited to a few selected pollutants, the cumulative damage cost from 2015 to 2022 is substantial (≈ € 2019 700 million).

The estimated societal damage cost of this study is meant to show an added cost due to scrubber water discharge and should not be interpreted as a full damage cost analysis. The estimation of damage cost is based on characterization factors 47 and a WTP study 46 that presents static values to represent a highly dynamic environment, which should be considered when interpreting the results (Fig. 5b ). However, quantifying all the uncertainties is beyond the scope of this study. Nonetheless, ReCiPe 47 provides a state-of-the-art life-cycle impact assessment approach that enables a conversion from increased pollution load to ecological toxicity potential and characterization factors that can, with the WTP output 45 , 46 , provide an estimated damage cost on marine ecotoxicity. In a previous Baltic Sea case study focusing on external costs for 2018 30 , when the scrubber fleet did not exceed 200 ships (Fig. 5 ), the damage cost of marine ecotoxicity due to scrubber water discharge constituted approximately 1% of the total damage cost of the impact categories marine ecotoxicity, marine eutrophication, reduced air quality and climate change. Applying the highest annual damage cost due to marine ecotoxicity derived from this study ( = € 2019 210 million in 2020), keeping all the other damage costs from Ytreberg et al. (2021) 30 unchanged, the scrubber water discharge contribution would increase to 6% of the summarized damage cost (€ 2010 2.9 billion = € 2019 3.3 billion).

The Baltic Sea case study shows that the cost of not restricting scrubber water discharge can be substantial. The installation of scrubbers has resulted in increased HFO consumption in this fragile sea area, classified as particularly sensitive by IMO 50 , where it has been determined that pollution loads must be reduced 51 . Similarly, with the implementation of a Mediterranean SECA in 2025, if low-sulfur options remain much more expensive than HFO, there is a risk that a larger fraction of the scrubber fleet will be operating within the Mediterranean Sea. Learning from the Baltic Sea case study, this could imply higher HFO consumption within the Mediterranean and an overall increased pressure on the marine environment with added societal damage cost. The emerging incentives within IMO and EU 25 , 26 to reduce the greenhouse gas emissions substantially until net zero by 2050 will presumably limit the use of fossil fuels in the medium- and long-term timeframe, but as shown in this study, the short payback times of scrubbers can make them lucrative in the short-term transition time before the stricter regulations and limitations are implemented. This will also entail a risk of increased HFO usage in areas where it is possible and, more importantly, economically profitable.

Scrubbers do enable a continued use of fossil fuels, hampering the transition to a sustainable transport system. In addition, the water needed for the scrubbing process requires more energy for pumps and so on, resulting in higher fuel consumption, that is, higher CO 2 emissions, per travelled distance 52 , 53 . A previous study also suggested that shipowners are economically encouraged to increase the operating speed on a ship with a scrubber as compared to one without 54 . The increased speed will further raise the CO 2 emissions due to the cubic dependence of speed and engine power. Higher CO 2 emissions are both in conflict with sustainable development goal 13 (ref. 49 ) and directly oppose the ambitions and commitments set by IMO 25 and the European Union 26 . Another aspect of scrubber water discharge includes strong acid addition to the sea 18 , 19 . Although the full effects on acidification remain unresolved 18 , 19 , 29 , model results show that scrubber water discharge can have notable effects in areas of high shipping intensity, reducing the seawater buffer capacity, that is, reducing the uptake of CO 2 and affecting marine life 18 , 19 .

To conclude, our results show a strong economic incentive to install scrubbers, which in combination with an increasing number of scientific studies demonstrating adverse effects on marine organisms 13 , 14 , 15 , 16 , 17 , contradicts the argument that shipowners have been acting in good faith and risk being penalized if stricter regulations on scrubbers are implemented 42 , 55 .

To assess the use of scrubbers, two different perspectives were analysed with respect to costs and environmental damage:

The investor, that is, the shipowner, perspective: calculating the break-even time of ship-specific scrubber installations of the global scrubber fleet based on installation cost, annual operational costs and monetary gain by using HFO instead of MGO (inside SECA) or VLSFO (outside of SECA).

The socio-economical perspective: as a Baltic Sea area case study, assessing the cost of not restricting scrubber water discharge by estimating the damage costs due to marine ecotoxicity of nine metals and ten PAHs from scrubber water discharge.

For comparison, all costs (€) have been indexed to 2019 (€ 2019 ) according to the Organisation for Economic Co-operation and Development (OECD) complete database of consumer price indices for comparison ( https://stats.oecd.org/ ). MATLAB (R2020a) was used for all calculations and plotting of data 56 .

Economic break-even calculations of the scrubber fleet

The Ship Traffic Emissions Assessment Model STEAM (ref. 44 and references therein), version 4.3.0, was used to estimate ship-specific annual energy and main engine load, fuel consumption, amount of discharged scrubber water, amount of energy consumed for scrubber use and kilometres travelled in different sea areas. The data were provided for each individual ship using Automatic Identification System (AIS), mandatory for ships >300 GT (ref. 57 ), between 2014 and 2022. These data were provided by Orbcomm Ltd. and included position reports from both terrestrial and satellite AIS networks. Technical description of the global fleet, which enables STEAM modelling at the vessel level, were obtained from SP Global. From all data, those ships that had registered a certificate of approval of scrubber installation within the timeframe (2014–2022) were selected for further analysis (maximum of 3,922 ships in 2022). STEAM identifies ships based on IMO numbers, registry numbers that remain with the vessel from construction to scrapping, and MMSI codes, which is the Maritime Mobile Service Identity number of the ship’s radio system, but the output data were anonymized by creating an artificial but unique identification number for each ship.

Annual balance was calculated for each unique ship by accounting for investment cost as starting conditions and annual operational costs and monetary savings on fuels from the use of HFO instead of MGO or VLSFO. Each ship was modelled from the date of installation until the end of 2022 (see example of ship with open-loop scrubber in Extended Data Fig. 1 ). The date of installation was given as year and month in STEAM, based on the ship-specific class certificate letter stating the date of approval to operate the scrubber.

The investment cost per kilowatt (€ 2019  kW −1 ; Fig. 4b ) for scrubber systems was collected from literature (for example, refs. 52 , 58 , 59 , 60 , 61 , 62 , 63 , and detailed description in Supplementary Table 1 ) where the median (50th), 5th and 95th percentiles were used in the different scenarios (Table 1 and Supplementary Table 1 ). Due to limited data availability, the hybrid systems were assigned the same investment cost as closed-loop systems (Fig. 4b ). Due to the variability in price connected to installed engine power, the ships and the cost were divided into three size categories based on total installed main engine power (Fig. 4b ). The total installed main engine power of the specific ships in the scrubber fleet were determined from SP Global ship database where power-regression equations based on a selection of 110,000 ships (65,000 excluding fishing vessels, tugs and service vessels) in different ship categories were used to calculate the engine power from the ship category and gross tonnage (derivations found in Supplementary Information C ). Due to poor data fit, statistical data binning was used instead of power regression for container ships and roll on–roll off (RoRo) vessels. The total investment cost per ship is summarized in Supplementary Fig. 1 and Supplementary Table 3 .

The operational costs were estimated from literature (for example, refs. 8 , 52 , 64 , 65 , 66 , and detailed description in Supplementary Table 1 ) and calculated for each ship based on annual main engine power output associated to the scrubber use. For the hybrid systems, the fraction of power used in open- (frac OL ) versus closed- (frac CL  = 1 − frac OL ) loop mode was calculated from the annual discharges of open- and closed-loop water according to equation ( 1 ).

where Q OL/CL is the discharge flow rate of open- (90 m 3  MWh −1 ) and closed- (0.45 m 3  MWh −1 ) loop systems 30 and V OL/CL are the annual volumes (m 3 ) of open- and closed-loop water discharged from the specific ships. The annual operational cost of the different scrubber systems was then calculated from the annual engine power usage (MW yr −1 ) during the time when the scrubber was operated ( P scrubber on ) and the power-based operational costs (€ 2019  MW −1 ) for open- and closed-loop scrubbers (cost operation OL/CL ) (equation ( 2 )).

For the open-loop scrubbers, frac OL  = 1 and for the closed-loop scrubbers, frac CL  = 1.

The daily resolution of fuel price (between 2014 and 2022) of HFO, MGO and VLSFO (starting 2019) was received from Ship & Bunker (Fig. 4a ). The Global 20 Ports Average bunker prices were used, which cover the 20 major global bunker ports and represent approximately 60–65% of the absolute global bunker volumes. In the different scenarios (Table 1 ), the annual median (50th) and the 5th and 95th percentiles of the fuel price difference between HFO/MGO and HFO/VLSFO were used when calculating annual balance (Fig. 4a–c ). VLSFO was introduced to the market in late 2019, and from 2020, it was assumed that the alternative fuel to HFO and scrubbers are MGO in SECA and VLSFO outside SECA (equation ( 3 )). Before the introduction of VLSFO, it is assumed that distillates were the only alternative to the use of scrubbers, and the fuel price difference between MGO and HFO is applied. The annual monetary gain (Δcost fuel,yr in € 2019  yr −1 ) attributed to the use of HFO instead of low-sulfur fuels are calculated from the fuel consumption (cons. HFO,yr in tonnes fuel yr −1 ) and fuel price difference (Δprice in € 2019 per tonnes fuel) for the individual years (equation ( 3 )).

Where D nonSECA/SECA,yr represents the distance travelled in SECA/non-SECA areas and D tot,yr is the total annual distance sailed according to STEAM data output for each vessel and year (Supplementary Table 2 ). Fuel penalties of 2–3% from scrubber operations are the most common estimates 52 , 53 , and an additional factor of 0.94 (VLSFO) and 0.92 (MGO) is applied due to the fuel penalty of using a scrubber (2%) and the higher energy content, that is, lower fuel consumption, of the low-sulfur fuels 67 .

The annual balance for each ship was calculated by summarizing the costs (negative signs) and the monetary gain from using HFO instead of low-sulfur fuels (positive sign) (equations ( 4 ) and ( 5 )). For the first year, that is same year as installation, the balance was calculated from the investment cost (cost inv. ), the cost of operation (cost operation,yr ) and the fuel cost savings (that is monetary gain from using HFO instead of low-sulfur fuels (Δcost fuel,yr )) where the two latter were adjusted to the number of months when the scrubber had been in service (equation ( 4 )). For the remaining years, until the end of 2022, the annual balance was calculated by summarizing the balance from the previous year with the operational cost and the monetary gain on fuel by not switching to low-sulfur fuels from the current year (equation ( 5 )).

To assess the variability of market fluctuations, the balance was estimated from three different calculation scenarios:

Median balance scenario: using the median for all costs, that is, fuel price difference, investment cost and operational cost;

Min balance scenario: using the 5th percentile in fuel price difference and the 95th percentile of investment and operational cost;

Max balance scenario: using the 95th percentile in fuel price difference and the 5th percentile of investment and operational cost.

The net surplus of the global fleet was calculated by summarizing the balance for every vessel at the end of 2022 (equation ( 6 )).

The calculations for the individual ships were further assessed to estimate payback times for the fleet (Fig. 2 ) and selecting a group of the open-loop fleet that had their scrubbers installed between December 2019 and December 2020 ( n  = 1,835) to illustrate the variation within the fleet and the outcome of applying the different calculation scenarios.

Cost of not restricting as damage on the marine environment

To assess the societal cost of not restricting scrubber water discharge, the dataset was limited to a Baltic Sea case study. The selection of ships was based on their operating area, that is, distance sailed in the Baltic Sea, the Gulf of Bothnia, Gulf of Finland, Gulf of Riga, Kattegat and Skagerrak (Supplementary Table 2 ) since the time of their scrubber installation. The HFO consumption and the volumes of scrubber water discharged within the Baltic Sea area for each ship was estimated from the total annual HFO consumption and the fraction sailed within Baltic Sea, calculated from the distance sailed in the Baltic Sea area divided by the total distance sailed for the given year.

The damage cost calculations were limited to marine ecotoxicity from the discharge of scrubber water, that is, based on the concentration of nine metals and ten PAHs in the scrubber water 33 . First, the cumulative toxicity potential of open- and closed-loop scrubber water was calculated using characterization factors from ReCiPe 47 (Supplementary Table 4 ). ReCiPe offers a harmonized indicator approach where characterization factors for organic substances and metals for different environmental compartments, including marine waters, have been produced 47 . With ReCiPe, each metal and PAH were assigned a characterization factor based on their fate and effect factor in relation to 1,4-dichlorobenzene (as 1,4 DCB equivalents (eq)). The cumulative toxicity potentials of open- and closed-loop scrubber water (kg 1,4 DCB eq. m −3 ) were obtained by summarizing the products of the metal and PAH characterization factor (as 1,4 DCB eq) and their corresponding concentrations in scrubber water (µg l −1 ) (Supplementary Table 4 ).

Second, the cumulative toxicity potential had to be related to a cost. Previous work have valuated the ecotoxicological impacts from the organotin compound tributyltin (TBT) in Sweden by conducting an extensive WTP study of Swedish households, where the damage cost (€ 2019  kg −1 1,4 DCB eq) amounted to € 2019 1.07 kg −1 1,4 DCB eq (€ 2019 0.73–1.29 kg −1 1,4 DCB eq) (refs. 45 , 46 ).

Finally, the annual damage cost for marine ecotoxicity (€ 2019  yr −1 ) resulting from scrubber discharge water (that is, the nine metals and ten PAHs commonly detected in scrubber water) in the Baltic Sea area (including Skagerrak) was calculated by multiplying the total volume scrubber water discharged in the area (m 3  yr −1 ) with the marine toxicity of open- and closed-loop scrubber water (as kg 1,4 DCB eq. m −3 ) and the damage cost of marine ecotoxicity (€ 2019  kg −1 1,4 DCB eq). A lower (higher) estimate was calculated by applying the lower (higher) concentrations of metals and PAHs, that is, lower (higher) toxicity potential of scrubber water and the lower (higher) WTP estimates (Supplementary Tables 6 and 7 ).

Reporting summary

Further information on research design is available in the Nature Portfolio Reporting Summary linked to this article.

Data availability

Data are provided within the paper and the Supplementary Information . Bunker fuel prices are commercially available with Ship & Bunker ([email protected]). The ship activity datasets (STEAM) were obtained from J.-P. Jalkanen ([email protected]). The AIS data and technical description of the world fleet used as input to STEAM are governed by contracts with third parties and cannot be shared. Ship size and installed power (Supplementary Information C ) was collected from Sea-web’s database of ships in the global fleet (S&P Global, previously IHS Markit Maritime & Trade: www.maritime.ihs.com/ ). The national assessments of environmental status according to the Marine Strategy Framework Directive (MSFD) were collected from the European Environment Agency Water Information System for Europe database https://water.europa.eu/marine/data-maps-and-tools/msfd-reporting-information-products/ges-assessment-dashboards/country-thematic-dashboards . In QGIS (version 3.16.11 Hannover), the open-access data layer ‘ESRI Ocean’ was used to visualize the regions in Fig. 1 . Characterization factors were collected from ReCiPe (v.1.1) available at https://www.rivm.nl/en/life-cycle-assessment-lca/downloads . The OECD complete database of consumer price indices was downloaded from https://stats.oecd.org/# .

Code availability

STEAM and its source code are property of the Finnish Meteorological Institute and are not available (controlled access). The custom MATLAB scripts for calculations and plotting of figures are available via Zenodo at https://doi.org/10.5281/zenodo.10944805 (ref. 56 ).

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Acknowledgements

The project has received funding from the Swedish Agency for Marine and Water management (grant agreement number 2911-22) (A.L.H., E.Y., I.-M.H., J.H.), the Swedish Transport Administration (grant agreement TRV 2021/12071) (A.L.H., E.Y., I.-M.H., R.P., E.F.) and by the European Union’s Horizon 2020 research and innovation programme Evaluation, control and Mitigation of the EnviRonmental impacts of shippinG Emissions (EMERGE) (grant agreement number 874990) (A.L.H., E.Y., I.-M.H., J.-P.J., T.G., R.P., E.F.).This work reflects only the authors’ view, and CINEA is not responsible for any use that may be made of the information it contains. We thank M. Lasek at Ship & Bunker for generously providing us with high-resolution fuel price data and J. Näsström at Chalmers University of Technology for her contribution in compiling the environmental status assessment. We would also like to express our gratitude to D. Turner at the University of Gothenburg for proofreading and providing valuable input.

Open access funding provided by Chalmers University of Technology.

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Anna Lunde Hermansson, Ida-Maja Hassellöv, Erik Fridell, Rasmus Parsmo, Jesper Hassellöv & Erik Ytreberg

Atmospheric Composition Research, Finnish Meteorological Institute, Helsinki, Finland

Tiia Grönholm & Jukka-Pekka Jalkanen

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Contributions

A.L.H.: methodology, investigation, writing–original draft, writing–review and editing, visualization, formal analysis. I.-M.H.: conceptualization, writing–review and editing, supervision, funding acquisition. T.G.: writing–review and editing, data curation, resources. J.-P.J.: writing–review and editing, resources, funding acquisition. E.F.: writing–review and editing, resources, funding acquisition. R.P.: writing–review and editing, resources, data curation. J.H.: writing–review and editing, data curation. E.Y.: conceptualization, investigation, writing–review and editing, supervision, funding acquisition.

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Correspondence to Anna Lunde Hermansson .

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Extended data

Extended data fig. 1 example of balance calculation of a ship with an open loop system installed in september 2015..

The upper level of the balance range corresponds to calculation with the Max Balance scenario and the lower range correspond to the Min Balance scenario. The full line represents the outcome of the Median Balance scenario. At the Date of Installation, the balance equals the investment cost (cost inv ) and the balance at the end of each year is calculated according to Eqs. ( 4 ) and ( 5 ). The payback time is defined as the time between date of installation and the point of break-even, that is the time when Balance=0.

Supplementary information

Supplementary information.

Supplementary Information A: description of assessment of marine environmental status (Supplementary Fig 1); B: complementary information to manuscript (Supplementary Tables 1–7 and Figs. 2–8); C: relationship between engine power and gross tonnage of ships (Supplementary Table 8 and Figs. 9–23).

Reporting Summary

Supplementary code 1.

MATLAB file with the script used for calculations of global fleet.

Supplementary Code 2

MATLAB file with the script used for calculations of Baltic Sea case study.

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Lunde Hermansson, A., Hassellöv, IM., Grönholm, T. et al. Strong economic incentives of ship scrubbers promoting pollution. Nat Sustain (2024). https://doi.org/10.1038/s41893-024-01347-1

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Received : 01 November 2023

Accepted : 11 April 2024

Published : 07 May 2024

DOI : https://doi.org/10.1038/s41893-024-01347-1

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