Presence of dangerous substances in the atmosphere
"Bad air quality" and "Air quality" redirect here. For the obsolete medical theory, seeMiasma theory. For the measurement of air pollution, seeAir quality index. For the qualities of air, seeAtmosphere of Earth.
Deaths in 2021 from air pollution per 100,000 inhabitants (IHME)
The World Bank has estimated that welfare losses (premature deaths) andproductivity losses (lost labour) caused by air pollution cost theworld economy over $8 trillion per year. Air quality is closely related to theEarth's climate andecosystems globally. Many of the contributors of local air pollution are also sources ofgreenhouse emission i.e., burning offossil fuel.[1]
Many different technologies and strategies are available for reducing air pollution.[10] National air quality laws have often been highly effective, notably the 1956Clean Air Act in Britain and theUS Clean Air Act, introduced in 1963.[11][12] Some of these efforts have been successful at the international level, such as theMontreal Protocol,[13] which reduced the release of harmfulozone-depleting chemicals, while others, such asinternational action on climate change, have been less successful.[14]
There are many different sources of air pollution. Some air pollutants (such as nitrogen oxides) originate mainly from human activities,[15] while some (notablyradon gas) come mostly from natural sources.[16] However, many air pollutants (including dust andsulfur dioxide) come from a mixture of natural and human sources.[17]
Most of the world's air pollution is from burning fossil fuels for industry, construction, transportation, and heating, although humans make air pollution in many other ways.[18] For instance,nuclear weapons, toxic gases,germ warfare, and rocketry can cause air pollution.[19]
Demolition of the cooling towers of a power station, Athlone, Cape Town, South Africa, 2010Controlled burning of a field outside ofStatesboro, Georgia, US, in preparation for spring plantingSmoking of fish over an open fire in Ghana, 2018Joss paper ash. With wind and dispersion, the size ofparticulates decreases, while the number of particles increases
Other industries cause air pollution too.[25] A 2014 study found that in China, manufacturing and construction sectors contributed more than 50% of air pollution. This was due to highemission intensity and highemission factors in its industrial structure.[26] Polluting industries have been pushed out of richer nations, and China has also started to push its most polluting industries out of the country.[27]
Construction,renovation and demolition produces dust, but also other pollutants.[28][29][30] Though its use has been banned in many countries, the extensive use ofasbestos in construction in the past has left asbestos in many places, where it can cause various lung diseases when disturbed.[31]
Road vehicles produce a significant amount of all air pollution (typically, for example, around a third to a half of all nitrogen dioxide emissions)[32][33] and are a major driver ofclimate change.[34] Vehicles with petrol and diesel engines produce about half of their emissions from theirexhaust gas, and the other half fromnon-exhaust emissions (tyre and brake wear and erosion or disturbance of the road surface);electric vehicles produce no tailpipe emissions, but still produce the other emissions.[35]Diesel trains, ships andplanes also cause air pollution.[36]
Open dumps of waste are a common source of air pollution in low-income countries. The waste eitherself-ignites or is burned on purpose, releasing soot, methane and other pollutants.[42] Globally, a quarter ofsolid waste is not collected. Another quarter is not disposed of properly.[43] The waste in landfills itself also produces methane.[44]
In developing and poor countries, traditional biomass burning (wood, crop waste and dung) is the major source of air pollutants.[45][46] It is also the main source of particulate pollution in urban areas of some developed countries including, the UK and Sydney, Australia.[47][48]
Gas stoves for cooking also cause air pollution, in the form ofNO2,benzene and carbon monoxide,[49] just asfurnaces and other types of fuel-burning heating devices.[50] Fumes from paint,hair spray,varnish,aerosol sprays can be substantial; emissions from these sources was estimated to account for almost half of pollution fromvolatile organic compounds in the Los Angeles basin in the 2010s.[51]
Dust from desert can cause poor air quality far from its source. For instance, dust from theGobi Desert in China and Mongolia can reachHawaii, and dust from theSahara reaches the Mediterennean.[52]Wildfires release smoke andcarbon monoxide. During periods of active wildfires, its smoke can make up almost 75% of all air pollution by concentration.[53]
Radon is a radioactive gas that can build up in buildings from thesoil. It can causelung cancer, especially insmokers. Levels are generally low, but can be elevated in buildings with "leaky" foundations or areas with soils rich inuranium.[54]
Vegetation, in some regions, emits environmentally significant amounts ofvolatile organic compounds (VOCs) on warmer days. These VOCs react with human pollution sources – specifically, NOx, SO2, and organic carbon – to produce a seasonal haze of secondary pollutants.[55]Black gum, poplar, oak andwillow are some examples of vegetation that can produce abundant VOCs. The VOC production from these species result in ozone levels up to eight times higher than the low-impact tree species.[56]
Volcanic eruptions produce mostly steam (about 79 percent), but also carbon dioxide (12 per cent),sulfur dioxide (6.5 percent), and small amounts of other pollutants, such aschlorine andash particulates.[57]
E-waste processing inAgbogbloshie, Ghana, using open-burning of electronics to access valuable metals like copper. Open burning of plastics is common in many parts of the world without the capacity for processing. Especially without proper protections, heavy metals and other contaminates canseep into the soil, and createwater pollution and air pollution.Schematic drawing, causes and effects of air pollution: (1)greenhouse effect, (2)particulate contamination, (3) increasedUV radiation, (4)acid rain, (5) increasedground-level ozone concentration, (6) increased levels ofnitrogen oxides
An air pollutant is a material in the air that can have many effects on humans and the ecosystem.[58] The substance can be solid particles, liquid droplets, or gases, and often takes the form of anaerosol (solid particles or liquid droplets dispersed and carried by a gas).[59] A pollutant can be of human or natural origin.
Pollutants are classified as primary or secondary. Primary pollutants are produced directly by a source and remain in the same chemical form after they have been emitted into the atmosphere. Examples include ash from a volcanic eruption, carbon monoxide gas from motor vehicle exhausts, and sulfur dioxide released from factories. Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants react or interact.Ground-level ozone is a prominent example of a secondary pollutant. Some pollutants may be both primary and secondary: they are both emitted directly and formed from other primary pollutants.[60]
Ammonia (NH3) is emitted mainly by agricultural waste. It is normally encountered as a gas with a characteristic pungent odor. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to foodstuffs and fertilizers. Although in wide use, ammonia is both caustic and hazardous.[61] In the atmosphere, ammonia reacts withoxides of nitrogen and sulfur to form secondary particles.[62]
Carbon dioxide (CO2) is mainly emitted by the burning of fossil fuels.[63] It is potentially lethal at very high concentrations (typically 100 times "normal" atmospheric levels).[64][65] Although theWorld Health Organization recognizes CO2 as a climate pollutant, it does not include the gas in itsAir Quality Guidelines or set recommended targets for it.[66] Workplace exposure limits exist in places like UK (5,000 ppm for long-term exposure and 15,000 ppm for short-term exposure).[65] Natural disasters like thelimnic eruption atLake Nyos can result in a large sudden release as well.[67]
CO2 is sometimes called an air pollutant, because it is the maingreenhouse gas responsible forclimate change.[68][69] This question of terminology has practical consequences, for example, in determining whether the U.S.Clean Air Act (which is designed to improve air quality) is deemed to regulate CO2 emissions. TheInflation Reduction Act of 2022 amended the Clean Air Act to define CO2 from fossil fuel burning explicitly as an air pollutant.[70]
Carbon monoxide (CO) is a colorless, odorless, toxic gas.[71] It is a product ofcombustion of fuel such as natural gas, coal or wood. In the past, emissions from vehicles were the main source of CO, but modern vehicles do not emit much CO. Now, wildfires andbonfires are the main source of outdoors CO.[72] Indoors, CO is a larger problem and mainly comes from cooking and heating.[73]
Nitrogen dioxide concentrations as measured from satellite 2002–2004
Nitrogen oxides (NOx), particularly nitrous oxide (NO), are mostly created by the burning of fossil fuels, and in lesser amounts bylightning.Nitrogen dioxide (NO2) is formed from NO in a reaction with other atmospheric gases.[74][75] NO and NO2 can form acid rain, can form into ahaze, and can causenutrient pollution in water.[76] NO2 is a reddish-brown toxic gas with a strong odor, whereas NO is odorless and does not have a color.[77]
Particulate matter (PM), also known as particle pollution, is a mix of microscopic solid particles or droplets suspended in a gas.[78] Volcanoes,dust storms, forest and grassland fires, living plants, and sea spray are all sources of particles. Aerosols are produced by human activities such as the combustion of fossil fuels in cars, power plants, and industrial processes.[citation needed] Increased levels of fine particles in the air are linked to health hazards such as heart disease,[79] altered lung function and lung cancer;[80] a definitive link between fine particulate pollution and higher death rates in urban areas was established by theHarvard Six Cities study, published in 1993.[81]
Efforts to reduce particulate matter in the air may result in better health.[82]
Sulfur dioxide (SO2) is produced by volcanoes and in various industrial processes. Coal and petroleum often contain sulfur compounds, and their combustion generates sulfur dioxide. High concentrations of SO2 in the air upon emissions generally also lead to the formation of other sulfur oxides (SOx). SOx can react with other compounds in the atmosphere to form small particles and contribute to particulate matter (PM) pollution [...] At high concentrations, gaseous SOx can harm plants by damaging foliage and decreasing growth. SO2 and other sulfur oxides can contribute to acid rain.[83] Further oxidation of SO2, usually in the presence of a catalyst such as NO2, forms H2SO4, and thusacid rain is formed.
Ground-level ozone (O3): Ozone is created when NOx and VOCs mix.[84] Photochemical and chemical reactions involving it fuel many of the chemical activities that occur in the atmosphere during the day and night. It is a pollutant and a component ofsmog that is produced in large quantities as a result of human activities (mostly the combustion of fossil fuels).[85] O3 is largely produced by chemical reactions involving NOx gases (nitrogen oxides, especially from combustion) and volatile organic compounds in the presence of sunlight. Due to the influence of temperature and sunlight on this reaction, high ozone levels are most common on hot summer afternoons.[86]
Volatile organic compounds (VOC): VOCs are both indoor and outdoor air pollutants.[87] They are categorized as either methane (CH4) or non-methane (NMVOCs). Methane is an extremely efficient greenhouse gas which contributes to enhancedglobal warming. Other hydrocarbon VOCs are also significant greenhouse gases because of their role in creating ozone and prolonging the life ofmethane in the atmosphere. This effect varies depending on local air quality. The aromatic NMVOCs benzene, toluene and xylene are suspected carcinogens and may lead to leukemia with prolonged exposure. 1,3-butadiene is another dangerous compound often associated with industrial use.
Chlorofluorocarbons (CFCs): Emitted from goods that are now prohibited from use; harmful to the ozone layer. These are gases emitted by air conditioners, freezers, aerosol sprays, and other similar devices. CFCs reach the stratosphere after being released into the atmosphere.[88] They interact with other gases here, causing harm to the ozone layer. UV rays are able to reach the Earth's surface as a result of this. This can result in skin cancer, eye problems, and even plant damage.[89]
Persistent organic pollutants, which can attach to particulates. Persistent organic pollutants (POPs) are organic compounds that are resistant toenvironmental degradation due to chemical, biological, orphotolytic processes. As a result, they've been discovered to survive in the environment, be capable of long-range transmission,bioaccumulate in human and animal tissue, biomagnify in food chains, and pose a major threat to human health and theecosystem.[90] TheStockholm Convention on Persistent Organic Pollutants identified pesticides and other persistent organic pollutants of concern. These includedioxins andfurans which are unintentionally created by combustion of organics, like open burning of plastics, and areendocrine disruptors andmutagens.
Polycyclic aromatic hydrocarbons (PAHs): a group of aromatic compounds formed from the incomplete combustion of organic compounds including coal and oil and tobacco.[93] Wood burning is another significant source of PAHs.[94]
Photochemical smog: particles are formed from gaseous primary contaminants and chemicals.[95] Smog is a type of pollution that occurs in the atmosphere. Smog is caused by a huge volume of coal being burned in a certain region, resulting in a mixture of smoke and sulfur dioxide.[96] Modern smog is usually caused by automotive and industrial emissions, which are acted on in the atmosphere by UV light from the sun to produce secondary pollutants, which then combine with the primary emissions to generate photochemical smog.
Microplastics from construction,[97] cosmetics, clothing, and many other sources.[98]
There are many other chemicals classed as hazardous air pollutants. Some of these are regulated in the USA under theClean Air Act and in Europe under numerousdirectives (including the Air "Framework" Directive, 96/62/EC, on ambient air quality assessment and management, Directive 98/24/EC, on risks related to chemical agents at work, and Directive 2004/107/EC covering heavy metals and polycyclic aromatic hydrocarbons in ambient air).[99][100]
There is an difference between air pollutionemissions andexposure.[101] Emissions are the quantity of pollutants released from a particular source; exposure is the quantity of a pollutant breathed in by people or other living things. Where air pollution laws may seek to limit the emissions of a particular pollutant, or the concentration in a particular environment, the health impacts depend on people's exposure to that pollutant.[102]
The risk of air pollution is determined by the pollutant'shazard and the amount of exposure to that pollutant. Air pollution exposure can be measured for a person, a group, or an entire population. For example, one would want to determine a geographic area's exposure to a dangerous air pollution, taking into account the various environments, activities and age groups. A little child'sinhaling rate, for example, will be lower than that of an adult. A young person engaging in strenuous exercise will have a faster rate of breathing than a child who is sitting.[103]
Share of the population exposed to air pollution levels above WHO guidelines, 2017
Exposure to air pollution is worst in lower-middle income countries in line with theenvironmental Kuznets curve.[104] Based on the 2021 WHO air quality standards, 99% of the world population is exposed to harmful air pollution.[9]
For some pollutants such asblack carbon, traffic related exposures may dominate total exposure despite short exposure times since high concentrations coincide with proximity to major roads or participation in (motorized) traffic.[105] A large portion of total daily exposure occurs as short peaks of high concentrations.[106]
In 2021, the WHO halved its recommended guideline limit for tiny particles from burning fossil fuels. The new limit fornitrogen dioxide (NO2) is 75% lower.[107] Growing evidence that air pollution—even when experienced at very low levels—hurts human health, led the WHO to revise its guideline (from 10 μg/m3 to 5 μg/m3) for what it considers a safe level of exposure of particulate pollution, bringing most of the world—97.3 percent of the global population—into the unsafe zone.[108]
A lack of ventilation indoors concentrates air pollution where people often spend the majority of their time. Indoor air pollution can pose a significant health risk. According to EPA reports, the concentrations of many air pollutants can be two to five times higher in indoor air than in outdoor air. Indoor air pollutants can be up to 100 times higher in some cases than they are inside.[109]
Indoor contaminants that can cause pollution include asbestos, biologic agents, building materials, radon, tobacco smoke, and wood stoves, gas ranges, or other heating systems.[109]
Radon (Rn) gas, acarcinogen, is exuded from the Earth in certain locations and trapped inside houses. Building materials including carpeting andplywood emitformaldehyde (H-CHO) gas. Paint and solvents give off volatile organic compounds (VOCs) as they dry.Lead paint can degenerate intodust and be inhaled.[114]
Intentional air pollution is introduced with the use ofair fresheners,incense, and other scented items. Controlled wood fires in cook stoves and fireplaces can add significant amounts of harmful smoke particulates into the air, inside and out.[114][115] Indoor pollution fatalities may be caused by usingpesticides and other chemical sprays indoors without proper ventilation. Also the kitchen in a modern produce harmful particles and gases, with equipment like toasters being one of the worst sources.[116]
Carbon monoxide poisoning and fatalities are often caused by faulty vents and chimneys, or by the burning of charcoal indoors or in a confined space, such as a tent.[117] Chroniccarbon monoxide poisoning can result even from poorly-adjustedpilot lights. Traps are built into all domesticplumbing to keep sewer gas andhydrogen sulfide, out of interiors. Clothing emitstetrachloroethylene, or other dry cleaning fluids, for days after dry cleaning.
Biological sources of air pollution are also found indoors, as gases and airborne particulates. Pets produce dander, people produce dust from minute skin flakes and decomposed hair,dust mites in bedding, carpeting and furniture produce enzymes and micrometre-sized fecal droppings, inhabitants emit methane, mold forms on walls and generatesmycotoxins and spores,air conditioning systems can incubateLegionnaires' disease and mold, and houseplants, soil and surrounding gardens can producepollen, dust, and mold. Indoors, the lack of air circulation allows these airborne pollutants to accumulate more than they would otherwise occur in nature.
Air pollution is an important risk factor for various diseases, such asCOPD (a common lung disease),stroke,heart disease,lung cancer andpneumonia. Indoor air pollution is also associated withcataract.[118] Air pollution has further been linked to brain disorders, such asdementia, depression, anxiety and psychosis.[119] Diseases that develop from persistent exposure to air pollution areenvironmental health diseases, which develop when a health environment is not maintained.[120]
Pollutants strongly linked to negative health effects include particulate matter, carbon monoxide, nitrogen dioxide (NO2), ozone (O3), and sulphur dioxide (SO2). Fine particulates are especially damaging, as they can enter thebloodstream via the lungs and reach other organs. Air pollution causes disease by drivinginflammation andoxidative stress, suppressing the immune system and by damaging DNA.[118]
Even at very low levels (under the WHO recommended levels), fine particulates can continue to cause harm.[121]Children are highly vulnerable to air pollution as they breathe at a higher rate than adults. Because they are shorter, they breathe in air closer to the ground, which usually has higher pollution levels (for instance, from vehicle exhaust or dust).[122] People living inpoverty, babies andolder people are also disproportionately affected by air pollution; pregnancy is also more risky when exposed to air pollution.[123]
Estimates of the death toll from air pollution vary across publications.
Estimates of deaths due to air pollution vary.[124] The 2024Global Burden of Disease Study estimates that air pollution contributed to 8.1 million deaths in 2021, which is more than 1 in 8 deaths. Outdoor particulate pollution (PM2.5) was the largest cause of death (4.7 million), followed byindoor air pollution (3.1 million) and ozone (0.5 million).[5]
The WHO estimates that 6.7 million people die from air pollution each year, 4.2 million due to outdoor air pollution.[125] Roughly 68% of outdoor air pollution-related premature deaths were due to ischaemic heart disease and stroke, 14% due to COPD and 14% due to lung infections (lower respiratory tract infections).[125]
A study published in 2019 estimated that, for 2015, the number was around 8.8 million, with 5.5 million of these premature deaths due to air pollution from human sources.[126][127] The global meanloss of life expectancy from air pollution in 2015 was 2.9 years, substantially more than, for example, 0.3 years from all forms of direct violence.[128]
Air pollution deaths by nation due to fossil fuels
India and China have the higher number of deaths from air pollution. In India, it contributed to 2.1 million deaths in 2021, whereas China saw 2.4 million deaths.[129] In some countries, more than 20% of deaths were attributed to air pollution, for instance in Nepal, Bangladesh, Laos and North Korea. Air pollution deaths are high in middle-income countries due to industry and in low-income countries due to the use of solid fuels for cooking.[130]
Annual premature European deaths from air pollution are estimated at 416,000[131] to 800,000.[127] The UK saw some 17,000 deaths in 2021 due to air pollution. Nigeria, Indonesia and Pakistan each saw over 200,000 deaths resulting from air pollution.[132]
Eliminating energy-related emissions in the United States would prevent 46,900–59,400 premature deaths each year and provide $537–$678 billion in benefits from avoided PM2.5-related illness and death.[133] A 2023 study onsulfur dioxide emissions by coal power plants (coal PM2.5) concluded that "exposure to coal PM2.5 was associated with 2.1 times greater mortality risk than exposure to PM2.5 from all sources."[134] From 1999 to 2020, a total of 460,000 deaths in the US were attributed to coal PM2.5.[134]
Deaths caused by accidents and air pollution from fossil fuel use in power plants exceed those caused by production ofrenewable energy.[135]
The largest cause of air pollution isfossil fuel combustion[136] – mostly the production and use ofcars, electricity production, and heating.[137] There are estimated 4.5 million annual premature deaths worldwide due to pollutants released by high-emission power stations and vehicle exhausts.[138]
A study concluded that PM2.5 air pollutioninduced by the contemporary free trade and consumption by the19 G20 nations causes two million premature deaths annually, suggesting that the average lifetime consumption of about ~28 people in these countries causes at least one premature death (average age ~67) while developing countries "cannot be expected" to implement or be able to implement countermeasures without external support or internationally coordinated efforts.[139][140]
Air pollution is a leading risk factor for stroke, particularly in developing countries where pollutant levels are highest.[142] A systematic analysis of 17 different risk factors in 188 countries found air pollution is associated with nearly one in three strokes (29%) worldwide (34% of strokes in developing countries versus 10% in developed countries).[143][144] The mechanisms linking air pollution to increased cardiovascular mortality are not fully understood, but likelysystemic inflammation andoxidative stress.[145]
Air pollution has been associated with increased hospitalization and mortality andCOPD (chronic obstructive pulmonary disease).[146] COPD is a common disease which causes breathing difficulties and is the fourth-largest cause of death globally.[147] Almost half of COPD deaths are due to air pollution.[142] Fine particles (PM2.5) or NO2 were associated with increased risk of developing COPD.[148]
Air pollution is further associated with increased risk of asthma and worsening of symptoms, and this effect seems stronger in children.[149] For adults, fine particles (PM2.5) or NO2 seem linked toasthma onset too.[150] Short-term exposure to ozone makes asthma worse in children.[151] There is limited evidence on (almost) fatal asthma attacks in children: ground-level ozone and PM2.5 seem to increase its risk.[152]
The risk of lung disease from air pollution is greatest for infants and young children, whose normal breathing is faster than that of older children and adults; the elderly; those who work outside or spend a lot of time outside; and those who have heart or lung diseasecomorbidities.[153]
Dark factory-emitted clouds obscuring the Clark Avenue Bridge in Cleveland, Ohio in July 1973
Around 265,000 lung cancer deaths were attributed globally in 2019 to exposure tofine particulate matter, PM2.5, suspended in the air.[154] Exposure to indoor air pollution, includingradon, caused another 170,000 lung cancer deaths.[154] Lung cancer was also more common among people exposed to NO2 and black carbon.[155]
Outdoor air pollution may increase risk of other types ofcancer too, but the evidence is not as clear as for lung cancer.[156] For instance, there may be a relationship betweenkidney cancer and PM2.5 and NO2 levels.[157] Household air pollution, for instance from cooking with solid fuels, but also from radon in building material, has been associated withcervical,oral, andesophageal cancer.[156]
Stillbirths,miscarriages andbirth defects are all more likely when the mother is exposed to air pollution during pregnancy. Exposure to air pollution also raises the chance a baby has alow birth weight. The impacts might be due to pollutants directly impacting theplacenta orfetus, or indirectly as via the mother's health (as air pollution can cause systemic inflammation and oxidative stress).[122]
Over a third of preterm births were associated with air pollution in 2021 globally. It causes more than half a million newborn deaths, a quarter of overall deaths.[122] The source of PM2.5 differs greatly by region. In South and East Asia, pregnant women are frequently exposed to indoor air pollution because of wood and otherbiomass fuels being used for cooking, which are responsible for more than 80% of regional pollution. In the Middle East, North Africa and West sub-Saharan Africa, fine PM comes from natural sources, such asdust storms.[158]
Including older children, polluted air leads resulted in the death of over 700,000 children in 2021 (709,000 under 5 years of age and 16,600 aged 5–14 years).[122] Children in low or middle income countries are exposed to higher levels of fine particulate matter than those in high income countries.[159] Further health effects of air pollution on children include asthma, pneumonia and lower respiratory tract infections.[160] There is possibly a link between exposure to air pollution during pregnancy and after birth andautism in children.[161][162]
Air pollution is linked to various diseases of thebrain.[119] Indoor air pollution exposure during childhood may negatively affect cognitive function and neurodevelopment.[163][164]Prenatal exposure may also affect neurodevelopment.[165][166] It may also contribute toneurodegenerative diseases such as Alzheimer's disease and Parkinson's disease.[164] There are various routes by which air pollution could cause brain damage: it can cause neuroinflammation, or secondary effects from lung inflammation. At the same time, it can cause cardiovascular disease which in itself raises the risk of brain diseases.[119]
Exposure to air pollution may also drivemental health issues, such asdepression andanxiety.[167] In particular, air pollution from the use of solid fuels was associated with a higher depression risk.[168] Depression risk andsuicide was more strongly linked to finer particulate matter (PM2.5), compared to coarser particles (PM10). The association was strongest for people over the age of 65.[169]
Problems with thinking (cognitive issues) are also associated with air pollution. In people over the age of 40, both NOx and PM2.5 have been linked to general cognitive problems. PM2.5 was also associated with reducedverbal fluency (for instance, number of animals one can list in a minute) and worseexecutive functions (likeattention andworking memory). Similarly, children tended to fare worse in tests involving working memory when there was NOx, PM2.5, or PM10 pollution.[170]
PM2.5 Levels Across the World's 5 Most Populated Nations in 2019
Various studies have estimated the impacts of air pollution on agriculture, especially ozone. A 2020 study showed that ozone pollution in California may reduce yields of certain perennial crops such as table grapes by as much as 22% per year, translating into economic damages of more than $1 billion per year.[171] After air pollutants enter the agricultural environment, they not only directly affect agricultural production and quality, but also enter agricultural waters and soil.[172] The COVID-19 induced lockdown served as a natural experiment to expose the close links between air quality and surface greenness. In India, the lockdown induced improvement in air quality, enhanced surface greenness and photosynthetic activity, with the positive response of vegetation to reduce air pollution was dominant in croplands.[173] On the other hand, agriculture in its traditional form is one of the primary contributors to the emission of trace gases like atmospheric ammonia.[174]
AWorld Bank study found that PM2.5 pollution in 2019 cost theworld economy over $8 trillion, which was over 6% of globalGDP. They suggested prioritising reducing pollution from diesel fuelled vehicles and coal-fired power plants.[175]: ix
The problem is most acute in thedeveloping world. "Children under age 5 in lower-income countries are more than 60 times as likely to die from exposure to air pollution as children in high-income countries."[176][177] Choosing an appropriateConcentration Response Function andValue of a Statistical Life can be difficult for researchers in low and middle income countries.[178]
A study published in 2022 found "a strong and significant connection between air pollution and construction site accidents" and that "a 10-ppb increase in NO2 levels increases the likelihood of an accident by as much as 25%".[179]
The world's worst short-term civilian pollution crisis was the 1984Bhopal Disaster in India.[180] Leaked industrial vapours from the Union Carbide factory, belonging to Union Carbide, Inc., U.S.A. (later bought byDow Chemical Company), killed at least 3787 people and injured from 150,000 to 600,000.[citation needed]
The United Kingdom suffered its worst air pollution event when the 4 DecemberGreat Smog of 1952 formed over London. In six days more than 4,000 died and more recent estimates put the figure at nearer 12,000.[181] The worst single incident of air pollution to occur in the US occurred inDonora, Pennsylvania, in late October 1948, when 20 people died and over 7,000 were injured.[182]
Air pollution can be monitored using different techniques. For instance,satellites andremote sensing is used to track PM, NO2 and ozone.[184] Many regions have a network of monitoring stations, with good coverage in India, China, Europe and the US. Poor coverage exist however for a number of highly-polluted countries, such as Chad and Iran. The density of measurements is improving as there are more low-cost techniques to measure air pollution.[185] Low-cost monitors can also be used for indoor air quality monitoring.[186] Finally, air quality sensors can be incorporated intodrones to measure air pollution higher up in the air.[187] Some websites attempt to map air pollution levels using available data.[188][189]
Air quality indexes (AQIs) offer a simple way for governments to communicate changes in air quality and associated health risks, especially during short-term pollution episodes, such as wildfires.[190] An AQI is essentially a health protection tool people can use to help reduce their short-term exposure to air pollution by adjusting activity levels during increased levels of air pollution. Examples include Canada'sAir Quality Health Index (AQHI),[191] Malaysia'sAir Pollution Index, and Singapore'sPollutant Standards Index.
Air pollutant emission factors are reported representative values that aim to link the quantity of a pollutant released into the ambient air to an activity connected with that pollutant's release.[3][192][193][194] The weight of the pollutant divided by a unit weight, volume, distance, or time of the activity generating the pollutant is how these factors are commonly stated (e.g., kilograms of particulate emitted per tonne of coal burned). These criteria make estimating emissions from diverse sources of pollution easier. Most of the time, these components are just averages of all available data of acceptable quality, and they are thought to be typical of long-term averages.
Burning of items polluting Jamestown environment inAccra, Ghana
Various pollution control technologies and strategies are available to reduce air pollution. For instance, industrial plants can installscrubbers, such asflue gas desulfurization orcatalysts to remove NOx.[204] Stringent environmental regulations, effective control technologies and shift towards the renewable source of energy also helping countries like China and India to reduce their sulfur dioxide pollution.[205]
In thepower sector, a very effective means to reduce air pollution is thetransition torenewable energy ornuclear power.[204] According to 2015 study 2015 the switch to100% renewable energy in the United States would eliminate about 62,000 premature deaths per year and about 42,000 in 2050, if no biomass were used. This would save about $600 billion in health costs a year due to reduced air pollution in 2050, or about 3.6% of the 2014 U.S. gross domestic product.[206]
Support for a ban on high-emission vehicles in city centres in Europe, China and the US from respondents to the European Investment Bank Climate Survey
Theavoid-shift-improve framework groups efforts to cut pollution from vehicles into reducing travel, shifting to sustainable transport, and improving vehicle technology.[207] Reducing motor vehicle travel can curb pollution. One strategy is to buildcompact cities, so that amenities are close by and cars are not needed.[208] Motor traffic can be reduced by creating morewalkable cities and by investing incycling infrastructure.[209]Working from home is another way of avoiding motorised traffic.[207] After Stockholm reduced motor vehicle traffic in the central city with acongestion tax, nitrogen dioxide and PM10 pollution declined, as did acute asthma attacks in children.[210]
Air pollution from a car
Traffic can be shifted to cleanermodes of transport, for instance by increased use ofpublic transport.[211][212] The9-Euro-Ticket scheme in Germany which allowed people to buy a monthly pass allowing use on all local and regional transport (trains, trams and busses) for 9 euro (€) for one month of unlimited travel saved 1.8 million tons of CO2 emissions during its three-month implementation from June to August 2022.[213]
Support, use and infrastructure-expansion of forms ofpublic transport that do not cause air pollution may be a critical key alternative to pollution.
Areas downwind (over 20 miles) of major airports have more than doubletotal particulate emissions in air than other areas, even when factoring in areas with frequent ship calls, and heavy freeway and city traffic like Los Angeles.[216]Aviation biofuel mixed in with jetfuel at a 50/50 ratio can reduce jet derived cruise altitude particulate emissions by 50–70%, according to aNASA led 2017 study (however, this should imply ground level benefits to urban air pollution as well).[217]
Heating and home stoves, which contribute significantly to regional air pollution, can be replaced with a much cleaner fossil fuel, such as natural gas, or, preferably, renewables, in poor countries.[218][219]Biodigesters can be used in poor nations whereslash and burn is prevalent, turning a useless commodity into a source of income. The plants can be gathered and sold to a central authority that will break them down in a large modern biodigester, producing much needed energy to use.[220]
Induced humidity and ventilation both can greatly dampen air pollution in enclosed spaces, which was found to be relatively high inside subway lines due to braking and friction and relatively less ironically inside transit buses than lower sitting passenger automobiles or subways.[223]
Tarps and netting are often used to reduce the amount of dust released fromconstruction sites.
Numerical models either on a global scale using tools such as GCMs (general circulation models coupled with a pollution module) or CTMs (Chemical transport model) can be used to simulate the levels of different pollutants in the atmosphere. These tools can have several types (Atmospheric model) and different uses. These models can be used in forecast mode which can help policy makers to decide on appropriate actions when an air pollution episode is detected. They can also be used for climate modeling including evolution of air quality in the future, for example the IPCC (Intergovernmental Panel on Climate Change) provides climate simulations including air quality assessments in their reports (latest report accessible through theirsite).
In 2022, the UN General Assembly passed a resolution recognizing the right to a clean, healthy, and sustainable environment as a human right.[224]
In the United Kingdom, air pollution campaigning currently involves a mixture of grassroots activism (by groups such asMums for Lungs and individual campaigners such asRosamund Kissi-Debrah[225]), public health awareness (through events such asClean Air Day), legal work (advanced by activist lawyers such asClientEarth), and more traditional campaigning (by environmental groups such asGreenpeace andFriends of the Earth, public health advocacy groups such asBritish Lung Foundation andAsthma UK, and organizations that raise health and safety issues, such as theBritish Safety Council).[226]Citizen science projects combine scientific research with public health awareness raising and grassroots environmental campaigning.[227]
In 2019, theCourt of Justice of the EU, found thatFrance did not comply with the limit values of the EU air quality standards applicable to the concentrations of nitrogen dioxide (NO2) in 12 air quality zones.[228]
Although a majority of countries have air pollution laws, 43% of countries lack a legal definition of air pollution, 34% lack outdoor air quality standards, and just 31% have laws for tackling pollution originating from outside their borders. Few countries have limits that are as strict as the World Health Organisation's recommendations.[229]
Some air pollution laws include specific air quality standards, such as the U.S.National Ambient Air Quality Standards and E.U. Air Quality Directive,[230] which specify maximum atmospheric concentrations for specific pollutants. Other examples of air quality laws around the world include theClean Air Act in Britain, theUS Clean Air Act, andTA Luft in Germany.[231] Some air pollution laws put limits on emissions (e.g. from vehicles), as well as air standards.[232]
The World Health Organization'sGlobal Air Quality Guidelines encourage improvements in a similar way to national standards, but are "recommendations" and "good practice" rather than mandatory targets that countries must achieve.[233]
Cities and towns often work together, both nationally and internationally, to share best practices for improving air quality. Initiatives of this kind include the BreatheLife Network of 79 cities (a campaign launched in 2016 by theClimate and Clean Air Coalition, World Health Organization, United Nations Environment Programme, and World Bank),[234]World Cities Day and theInternational Day of Clean Air for Blue Skies (two UN initiatives), and the Partnership for Healthy Cities (sponsored by the World Health Organization and health organization Vital Strategies).[235]
Other networks include theC40 Cities Climate Leadership Group, a public 'non-state' network of the world's leading cities that aims to curb their greenhouse emissions.[236] The C40 has been identified as 'governance from the middle' and is an alternative to intergovernmental policy.[237] It has the potential to improve urban air quality as participating cities "exchange information, learn from best practices and consequently mitigate carbon dioxide emissions independently from national government decisions".[236] A criticism of the C40 network is that its exclusive nature limits influence to participating cities and risks drawing resources away from less powerful city and regional actors.
Because Indigenous people[238] frequently experience a disproportionate share of the effects of environmental degradation and climate change, even while they have made very little contribution to the processes causing these changes, environmental justice is especially important to them. Indigenous peoples have been marginalized and their lands and resources have been exploited as a result of historical and continuing colonization, institutional injustices, and inequality.
Indigenous groups frequently lack the political and financial clout to influence policy decisions that impact their lands and means of subsistence or to lessen the effects of climate change. This makes the already-existing inequalities in these communities' social, economic, and health conditions worse. Furthermore, traditional ecological knowledge and Indigenous knowledge systems provide insightful information about sustainable resource management and climate change adaptation techniques. To promote persistence and environmental justice, Indigenous viewpoints must be acknowledged and integrated into efforts to mitigate the effects of climate change and adapt to them.
Combating climate change necessitates an all-encompassing strategy that recognizes the interdependence of social, economic, and environmental elements. This entails defending treaty rights, advancing Indigenous sovereignty and self-determination, and aiding Indigenous-led projects for sustainable development and environmental preservation.
Air pollution hotspots are areas where air pollution emissions expose individuals to increased negative health effects.[239] They are particularly common in highly populated, urban areas, where there may be a combination of stationary sources (e.g. industrial facilities) and mobile sources (e.g. cars and trucks) of pollution. Fine particulate matter such asdiesel soot, which contributes to more than 3.2 million premature deaths around the world each year, is a significant problem. It is very small and can lodge itself within the lungs and enter the bloodstream. Diesel soot is concentrated in densely populated areas, and one in six people in the U.S. live near a diesel pollution hot spot, such asCancer Alley along theMississippi River.[240]
While air pollution hotspots affect a variety of populations, some groups are more likely to be located in hotspots. Previous studies have shown disparities in exposure to pollution by race and/or income.Hazardous land uses (toxic storage and disposal facilities, manufacturing facilities, major roadways) tend to be located where property values and income levels are low. Lowsocioeconomic status can be a proxy for other kinds ofsocial vulnerability, including race, a lack of ability to influence regulation and a lack of ability to move to neighborhoods with less environmental pollution. These communities bear a disproportionate burden of environmental pollution and are more likely to face health risks such ascancer orasthma.[242]
Studies show that patterns in race and income disparities not only indicate a higher exposure to pollution but also higher risk of adverse health outcomes.[243] Communities characterized by lowsocioeconomic status and racial minorities can be more vulnerable to cumulative adverse health impacts resulting from elevated exposure to pollutants than more privileged communities.[243] Blacks and Latinos generally face more pollution than Whites and Asians, and low-income communities bear a higher burden of risk than affluent ones.[242] Racial discrepancies are particularly distinct in suburban areas of the Southern United States and metropolitan areas of the Midwestern and Western United States.[244] Residents in public housing, who are generally low-income and cannot move to healthier neighborhoods, are highly affected by nearbyrefineries and chemical plants.[245]
Air pollution is usually concentrated in densely populatedmetropolitan areas, especially in developing countries where cities are experiencing rapid growth and environmental regulations are relatively lax or nonexistent. Urbanization leads to a rapid rise in prematuremortality due to air pollution in fast-growing tropical cities.[246] However, even populated areas in developed countries have unhealthy levels of pollution, with Los Angeles and Rome being two examples.[247] Between 2002 and 2011 the incidence of lung cancer in Beijing near doubled. While smoking remains the leading cause of lung cancer in China, the number of smokers is falling while lung cancer rates are rising .[248]
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