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United Nations: 19 Frequently Asked Questions About Air Pollution

Time：

2022-09-27

01 Why is air pollution a priority?

Air pollution is everywhere.

Most people in the world live in areas with high levels of air pollution. Air pollution harms human health and well-being, reduces quality of life, and can negatively impact the economy. These impacts also disproportionately harm the most vulnerable populations and communities.

Air pollution is the biggest environmental risk to public health worldwide. People all over the world are exposed to air pollution, whether at work, during travel or at home. According to the World Health Organization (WHO), exposure to household and environmental (outdoor) fine particulate air pollution is responsible for approximately 7 million premature deaths each year, as well as severe disability in those who fall ill from air pollution.

Air pollution is a solvable problem, and rich countries have greatly improved air quality in recent decades. But air pollution is now disproportionately affecting people in low- and middle-income countries. In many developing countries, people's reliance on wood and other solid fuels, such as the use of raw coal for cooking and heating, and the use of kerosene for lighting, increases air pollution in homes and harms the health of those living in such environments. It is estimated that more than 2.7 billion people depend on this type of fuel. The impacts are being felt the most in parts of Asia and sub-Saharan Africa, where biomass burning for cooking is particularly prevalent.

Air pollution, while the most pressing impact on human health, also has significant impacts on many different types of ecosystems, reducing crop yields and harming forest health. It also reduces atmospheric visibility, accelerates corrosion of materials, buildings, monuments and cultural sites, and causes acidification of sensitive lake ecosystems.

Air pollution is also implicated in the current COVID-19 outbreak. Research conducted in the early months of the pandemic showed that higher levels of air pollution were associated with greater susceptibility to COVID-19 infection. The study also suggests that particulate pollution in the air may have contributed to the spread of COVID-19. While these studies require further investigation, they also provide another reason to take action against air pollution.

02 What is air pollution?

Air pollution is caused by various human activities.

Air pollution is caused by gases and particles emitted into the atmosphere by various human activities, such as the inefficient burning of fuels, agriculture and farming. There are also natural factors that contribute to air pollution, including soil dust particles and salt from ocean waves.

Air pollutants can be emitted directly from the source (i.e. primary pollutants) or formed from chemical reactions in the atmosphere (i.e. secondary pollutants). When these substances reach critical levels in the air, they can harm humans, animals, plants and ecosystems, reduce visibility, and corrode materials, buildings and cultural sites.

03 Is air pollution a new problem?

Air pollution has existed for thousands of years.

Air pollution is closely related to humans and has existed for thousands of years, starting with the use of fire for cooking and heating. Dangerously high levels of outdoor air pollution became a problem during the Industrial Revolution, and the massive use of coal caused many severe urban air pollution incidents.

The London smog of 1952 is an extreme case. That year, pollution blanketed London and killed more than 12,000 people in a matter of days as residential coal burning, coal for power generation, dirty fuel for transport and industrial pollution interacted with weather phenomena. After a public outcry, the UK passed the Clean Air Act (1956). Other deadly air pollution incidents, such as the Donora smog in the United States (1948) and the Maas Valley smog in Belgium (1930), prompted other countries to take similar actions to tackle air pollution.

In the 20th century, countries around the world continued to rely on fossil fuels, and air pollution intensified with the deepening of countries' industrialization. In newly industrialized countries such as China and India, this has led to extreme air pollution episodes, similar to those experienced in the United States and Europe in the past. However, with the advent of new clean and renewable energy sources, air quality regulations and management processes, local reliance on certain polluting fuels and practices is being reduced. Beijing used to be notorious for its air pollution problems, but over the past 20 years, Beijing has taken increasingly aggressive steps to reduce air pollution and air quality has improved significantly.

04 Where does air pollution come from?

Most are caused by human activities.

Air pollution comes from a wide range of sources, both natural and man-made. Natural sources include volcanic eruptions, ocean waves, soil dust, natural vegetation fires, and lightning. Some of the most common anthropogenic sources include power generation, transportation, industry, residential heating and cooking, agriculture, solvent use, oil and gas production, waste combustion, and building construction. Some sources, such as forest and savanna fires and wind-blown mineral dust, occur naturally but are exacerbated by human activity.

For most of the world's population, most of the air pollution they are exposed to is caused by human activity.

Different pollutants have different sources. In cities, air pollution comes from inside and outside the city, some from far away. Major sources of pollution in cities include vehicles, burning of natural gas, coal and charcoal, wood for cooking and heating, and industrial sources still located within cities. Many large industrial sources, such as cement plants, steel mills and power plants, are far from cities but still contribute to urban air pollution because pollutants can travel great distances with the air. Pollutants emitted by the oil and gas industry and the maritime sector can also spread over great distances.

Agricultural sources, including burning forests for arable land and forest fires, contribute to urban and rural air pollution. In very dry regions, near deserts and eroded land, wind-blown dust makes up a large portion of PM2.5. Most ammonia is emitted from agricultural and human waste disposal.

In rural and peri-urban areas in low-income countries, one of the most common sources of air pollution is household burning of biomass, other solid fuels such as coal, or kerosene for cooking, heating and lighting. Household air pollution can also contribute to outdoor air pollution.

05 Will air pollution spread?

Air pollution can spread.

Air pollution has a significant impact on places near its source, but because it can travel great distances in the atmosphere, air pollution produced in one place can also affect great distances. For example, pollutants that form fine particulate matter (PM2.5) and ozone (O3) can travel hundreds or thousands of kilometers, affecting entire regions and continents. This transboundary air pollution presents legislative and enforcement challenges, as different countries have little regulatory control over air pollution from outside their borders (see also Question 14).

Although long-range air pollutants are one of the causes of local air pollution, nearby pollution sources are still a very important determinant of local air quality. Concentration levels of pollutants like nitrogen dioxide (NO2) and sulfur dioxide (SO2) are highest near their sources (transportation, energy production and industry). Within a city, the areas closest to large pollution sources can have extremely high concentrations of pollutants, while other areas in the same city can be much cleaner.

Atmospheric conditions, such as wind, affect the spread of pollutants and can vary widely. Strong winds enable long-distance travel, while a windless environment can lead to a buildup of pollutants. Large cities in subtropical and tropical regions have severe pollution events due to very little wind and a lot of sunshine hours. Local weather conditions, such as mountains around cities, land-sea winds, etc., can affect the diffusion of pollutants and the formation of secondary pollutants.

06 How does air pollution affect human health?

Fine particles have the greatest impact.

The air pollutant with the greatest impact on human health is fine particulate matter. Fine particles have a diameter of less than or equal to 2.5 microns, also known as PM2.5. These tiny particles are 40 times smaller than a human hair and cannot be seen by the naked eye. But they can do a lot of damage to the human body. These particles are small enough to penetrate deep into our lungs, cause inflammation in sensitive lung tissue, and can enter the bloodstream, affecting organs such as the heart and brain. The World Health Organization estimates that 7 million people die prematurely each year from exposure to PM2.5.

Air pollution can cause acute and chronic illnesses. There is strong evidence that chronic exposure to air pollution increases the risk of: ischemic heart disease, stroke, chronic obstructive pulmonary disease (COPD), lung and upper aerodigestive tract cancers, adverse pregnancy outcomes [ Namely low birth rate, preterm birth, birth weight loss (infants weighing less than 5 pounds)], diabetes and cataracts. The World Health Organization's International Agency for Research on Cancer (IRCA) has classified air pollution as a carcinogen.

Some of the direct health effects of exposure to air pollution include irritation of the eyes, nose and throat; shortness of breath; coughing; exacerbating pre-existing conditions such as asthma attacks and chest pain. Age, pre-existing disease, other risk factors for disease, and susceptibility to pollutants can all affect a person's response to pollutants.

Air pollutant gases can also be very dangerous. Carbon monoxide (CO) limits the transfer of oxygen to tissues and can be lethal in very high concentrations. Sulfur dioxide (SO2) is a potent lung irritant that affects the health of those who already have respiratory conditions (asthma and chronic obstructive pulmonary disease), especially those who live and work near sources of SO2 . Nitrogen oxides (NOx) cause a variety of effects, from respiratory irritation to the development of asthma and increased mortality. According to the Global Burden of Disease, exposure to ozone (O3) causes respiratory disease and is associated with 472,000 premature deaths (IHME) in 2017.

07 Are there generally accepted safe levels of air pollution?

There is no completely safe level of air pollution.

While everyone's health is affected to varying degrees by air pollution, both in large cities and in rural areas, there is no evidence that air pollution levels are completely safe, especially when it comes to particulate matter. However, to help guide countries towards improving healthful air cleanliness, WHO has set normative guidance values for all major air pollutants above which air pollutants have the potential to negatively impact population health. For example, WHO estimates that reducing the annual average fine particulate matter (PM2.5) concentration from a level of 35 micrograms per cubic meter (μg/m3), the interim air quality guide value commonly used in many developing country cities, to WHO An organization-guided level of 10 μg/m3 can reduce air pollution-related deaths by about 15%.

This does not mean that there are no health impacts below these guidelines, but they represent health-based targets that help track the burden of disease from air pollution and inform the setting of national-level targets and standards , and monitoring the effectiveness of air quality management efforts aimed at improving health.

Many countries have established national air quality standards. National standards may vary from country to country and may be higher or lower than the corresponding WHO guidance values. It is a matter of policy to decide which specific risk groups should be protected by the standard and what level of risk is considered acceptable. However, many countries are struggling to meet WHO air quality standards and their interim targets.

The UNECE Convention on Long-Range Transboundary Air Pollution also defines a threshold (critical) level of ozone (O3) above which effects on crops and other vegetation may occur.

08 How does air pollution affect food, crops and biodiversity?

The role of ozone, sulfur and nitrogen.

Ozone (O3) is currently the main air pollutant affecting plant growth. It often reduces crop yields, affects forest health and reduces biodiversity. Different plant species have different sensitivity to O3. Species that are more sensitive to O3 will have less competitive advantage in the ecosystem, while more resistant species will gain the upper hand. Some crops are very sensitive to O3, especially beans. For example, soybean yields could be reduced by 15% or more. In addition, there is a knock-on effect on the climate as O3 pollution causes forest trees to grow slower, reducing the ability of forests to absorb carbon dioxide and their potential to help regulate climate change.

Other pollutants, such as sulfur and nitrogen, also damage forest and lake ecosystems through acidification of soil and surface water, which can affect forest growth and kill fish and other organisms. Nitrogen deposition also leads to eutrophication (over-fertilization) in low-nutrient ecosystems, such as wasteland, leading to large changes in biodiversity.

09 Does air pollution cause other environmental degradation?

Acid rain and smog are typical cases.

Some air pollutants cause "acid rain," which received particular attention in Europe and North America in the 1980s and 1990s. Sulfur dioxide (SO2) and nitrogen oxides (NOx) react with water in the atmosphere to produce sulfuric and nitric acids, which return to Earth as "acid rain."

Acid rain affects the environment by destroying the leaves of plants, reducing their productivity and depriving the soil of the nutrients that plants depend on to survive. Acidification of soil and river water kills fish and insects and affects other species that feed on them. Acid rain can also cause damage to buildings and monuments.

Acid rain has been significantly reduced in Europe and North America due to enhanced controls on sulfur dioxide and nitrogen oxide emissions, such as the U.S. Clean Air Act of 1970, the Canada-U.S. Air Quality Agreement of 1991, and similar measures in Europe. While acid rain has decreased in Europe and North America, acid rain in Asia remains a concern.

Aerosols and photochemical oxidants such as ozone also produce smog, reducing visibility and shrouding cities in dense smog. Concentrations of pollutants fell in North America and Europe, and smog decreased significantly, but in other parts of the world, especially Asia, smog is very common. Air pollution levels have fallen due to lockdowns and reduced emissions due to the COVID-19 crisis, and people in parts of northern India have seen the Himalayas for the first time in their lives, illustrating the close link between visibility and pollution.

10 How polluted is my location?

Many cities have implemented networks to continuously monitor air pollutants, incorporating them into their air quality management systems. Many of these cities regularly publish an Air Quality Index (AQI), which is easy to interpret and often color-coded to warn of dangerous levels of air pollution. This information is available through websites, newspapers and apps. Countries develop their own indices based on their own air quality standards. Therefore, the AQI cannot be compared between countries and is only used for public information purposes.

In many places, private companies are developing low-cost air quality monitors that people can install in their homes. This has spawned a network of citizen scientists reporting air quality, as well as a citizen-led online database of air quality.

Many international and civil society organizations and private companies also often use a combination of monitoring and satellite data to collect and report air quality information. If local information is not available, this information can be a useful resource for understanding air pollution issues in your city or country.

11 Where has air pollution been addressed?

No area is resolved.

Air pollution has not been addressed in any region, but emissions and pollutant concentrations have declined significantly in many European countries, as well as in the United States, Canada and Japan, as these countries have implemented strong policies, regulations, established regular monitoring system.

The most famous example is London, one of the most polluted cities, and pollution predates other cities, possibly peaking in 1900. Air quality in the UK has improved significantly since then. From 1900 to 2016, levels of particulate pollution in the air dropped by more than 97%. Other cities and regions have seen significant reductions in pollution levels as a result of similar policies. However, this does not mean that the air pollution problem has been solved. London's PM2.5 levels are still above the World Health Organization's air quality standards.

Mexico City is another example of a city where air pollution levels have dropped significantly. In the 1980s, Mexico City had a very serious ozone (O₃) pollution problem. O₃ levels, which peaked in 1989, had fallen by two-thirds by 2015 and were still high enough to have serious health impacts, yet pollution levels have decreased significantly.

12 How can the government improve air quality?

Act through investment and law.

Governments need to invest in capacity building to measure and monitor air pollution by establishing monitoring networks, and ensuring that such networks are functioning, properly maintained, and that procedures are followed to ensure the quality and reliability of air quality measurements.

The first step in responsible management of air pollution is to ensure that the necessary regulations, policies and enforcement mechanisms are in place and adequately supported. Governments should ensure that relevant agencies have sufficient capacity to monitor and assess air pollution emissions. This will ensure that policymakers know where air pollution is coming from, how large the different emission sources are, the levels of air pollution in different parts of the country, the impact on health, and what high-impact steps can be taken to reduce pollution levels and harms caused by pollution .

With limited capacity or no local data to carry out such activities, there are still resources available to help countries understand their air pollution problems and identify priority actions that can be taken. These include emissions sources estimated from global programmes (eg: Emissions Database for Global Atmospheric Research (EDGAR) emissions estimates), or pollution concentrations and health impacts estimated by satellite and global modelling combined with ground truth from monitoring stations (WHO, Health Institute for Metrics and Evaluation, State of the Global Air). These datasets have limitations and uncertainties and should be used when local data are not available or monitoring capabilities are limited.

13 Why is regional cooperation important?

Because some air pollutants travel across long distances across borders, a multi-country/multi-regional approach is critical to managing air pollution across borders. International cooperation facilitates knowledge sharing of experiences and good practices, and increases the prestige and resources needed to address the air pollution crisis on a scale commensurate with the magnitude of the problem.

A good example of the positive results of a multi-country intergovernmental approach to reducing air pollution is the ECE Convention on Long-Range Transboundary Air Pollution, the first coordinated national approach to addressing a common air pollution problem. Scientific cooperation has also begun in Asia, and the East Asian Acid Deposition Monitoring Network (EANET) has been building monitoring capacity and partnerships in East and South-East Asia. The ASEAN (ASEAN) Transboundary Haze Pollution Agreement was developed to limit air pollution from forest fires in Southeast Asia. Latin America and the Caribbean is implementing a regional plan to tackle air pollution.

14 What is the role of quality monitoring in air quality management?

The cost of air quality monitoring is much lower than the cost of reducing air pollution.

Countries face several challenges in addressing air quality issues. The cost of certified monitoring equipment and regular calibration and maintenance can be a heavy burden for many local authorities and national governments. It must be noted that the cost of air quality monitoring is much lower than the cost of reducing air pollution, the former being a public investment and the latter a private investment. Therefore, governments and cities in developing countries should prioritize and invest in establishing, operating, and maintaining surface-level air quality monitoring networks to generate reliable air quality data.

Many countries simply do not have government-run surveillance networks using regulatory standard equipment. In countries with limited resources, monitoring sites are often located only in the largest and most populous cities in the country. Many cities in developing countries can only have one monitoring point, or at most several monitoring points. This problem needs to be solved urgently.

15 What actions can businesses and industries take?

Businesses and industries have a key role to play in reducing air pollution, as many of their activities are the source of various air pollutants.

The private sector can contribute to air pollution through its cross-sectoral operations and supply chains. The private sector has a wide variety of sources of pollution, from burning fuel to distribution and delivery vehicles.

To reduce air pollution, the private sector can take several actions:

Integrate air quality into corporate social responsibility activities and commit to regular reporting and monitoring;
Identify and quantify air pollution emissions from different facilities, manufacturing processes and supply chains;
Develop air pollution reduction programmes for each sector and conduct advocacy campaigns to transparently communicate the level of emissions from their business activities and explain what they will do to reduce emissions.

16 How can I improve local air quality?

Most sources of air pollution are structural and embedded in the economic processes that underpin modern societies. Therefore, it is difficult for individuals to stop air pollution on their own. Tackling air pollution requires a collective effort.

The most important thing people can do is to understand the level of air pollution where they live and how it affects them and put pressure on politicians, leaders and policy makers to reduce the air pollution in their city/region/country Pollution.

Some of the steps individuals can take to reduce air pollution levels include:

Choose clean transportation whenever possible (e.g. public transportation, bicycles or walking rather than driving a car or motorcycle)
If you're considering buying a car, check the model's nitrogen dioxide emissions and actual emissions. Avoid buying diesel cars. Buying a hybrid or electric car will also help reduce your emissions
If you already have a car, make sure to maintain it regularly to minimise its contribution to air pollution
Use clean fuels and technology for cooking, lighting and heating
Stop burning household and agricultural waste, no longer use fireplaces and wood stoves
Monitor energy demand and waste in the home and install energy efficient appliances, light bulbs, insulation and storm windows

17 What is the link between air pollution and climate change?

Major air pollutants all have an impact on the climate.

Air pollution and climate change are intrinsically linked. All major air pollutants contribute to the climate, and most share sources with greenhouse gases (GHGs), especially those associated with the burning of fossil fuels. They also exacerbate each other's influence in a number of ways. Greenhouse gases such as methane, for example, contribute to the formation of ground-level ozone, and levels of ground-level ozone increase with temperature. Rising temperatures have increased the frequency of wildfires, which in turn have further increased levels of particulate air pollution.

Pollutants of "Short Term Climate Pollutants" (SLCPs) such as black carbon, ozone, methane and hydrofluorocarbons (HFCs) are powerful climate forcers and (in the case of ozone and black carbon) dangerous air pollutants . Many measures to reduce short-lived climate pollutants also reduce other air pollutants, such as nitrogen oxides. For example, measures to reduce black carbon affect regional climate change and slow the rate of near-term global warming. They also greatly reduce emissions of pollutants that cause PM2.5, thereby benefiting human health. Methane is a potent greenhouse gas that forms ozone in the atmosphere. Actions to reduce methane go a long way toward preventing climate change, protecting human health and crop yields. Therefore, comprehensive actions targeting short-lived climate pollutants can achieve a win-win situation by delivering real multiple benefits in terms of human health, agriculture and climate.

Air pollution and climate change are interconnected, providing us with an opportunity to amplify the benefits of our actions and drive greater emissions reductions.

18 The link between air pollution and sustainable development?

Air pollution is caused by various human activities.

Air pollution poses a threat to sustainable development as it simultaneously affects various social, environmental and economic criteria related to equitable human development, such as health, food security, gender equality, climate stability and poverty reduction.

The link between air pollution and development, the economy and the environment means that reducing air pollution is closely linked to the achievement of the Sustainable Development Goals (SDGs) and directly affects the achievement of the following goals and indirectly affects many other SDGs.

SDG 3: Good health and well-being
SDG 7: Affordable and clean energy
SDG 11: Sustainable cities and communities
SDG 13: Climate Change
Air pollution is also at the heart of social justice and global inequality. According to the World Health Organization (WHO), in low- and middle-income countries, 97% of cities with a population of more than 100,000 do not meet air quality standards. In high-income countries, the share fell to 49 percent.

19 Is clean air a human right?

The right to environmental health is a fundamental human right.

At least 155 countries recognize a healthy environment as a constitutional right. A number of international human rights instruments, including the Universal Declaration of Human Rights and the International Covenant on Economic, Social and Cultural Rights, have implied obligations related to clean air.

In 2019, at the 40th session of the Human Rights Council, the Special Rapporteur on human rights and the environment highlighted the right to breathe clean air in a report. The report highlights seven steps countries must take to realize the right to breathe clean air.