Air Pollution: Millions Breathing Toxic Air

Air pollution is a significant global health concern, contributing to an estimated 8.1 million deaths worldwide in 2021, making it the second leading risk factor for death. According to the World Health Organization (WHO), 99% of the global population breathes air that exceeds the recommended guideline limits, with low- and middle-income countries experiencing the highest exposure levels. A study by Nature Communications revealed that 7.3 billion people are directly exposed to unsafe annual concentrations of fine particulate matter (PM2.5), with 80% residing in low- and middle-income countries. This issue disproportionately affects lower-income groups, with 716 million of the world's poorest people living in areas with unsafe air pollution levels, particularly in Sub-Saharan Africa. The sources of outdoor air pollution include residential energy use, vehicles, power generation, agriculture, waste incineration, and industry. The health impacts of air pollution are far-reaching, causing strokes, heart diseases, lung cancer, acute and chronic respiratory diseases, and adverse effects on children's health and development.

Air pollution's impact on health

Air pollution is a major threat to health and the environment, impacting people worldwide. According to the World Health Organization (WHO), air pollution kills an estimated seven million people annually. Furthermore, 99% of the global population breathes air that exceeds the recommended limits set by the WHO, with low- and middle-income countries suffering the highest exposures.

The primary pathway of exposure to air pollution is through the respiratory tract. Pollutants such as particulate matter (PM), carbon monoxide (CO), ozone (O3), nitrogen dioxide (NO2), and sulphur dioxide (SO2) have been linked to adverse health effects. Fine particulate matter, such as PM2.5, is of particular concern as it can penetrate deep into the lungs, enter the bloodstream, and cause systemic damage to tissues and cells. These particles can be emitted from various sources, including vehicles, power generation, and industrial processes.

The health impacts of air pollution are wide-ranging and can affect almost every organ in the body. Short-term exposure to high levels of particulate matter can lead to reduced lung function, respiratory infections, and aggravated asthma. Ozone, a powerful lung irritant, can cause chest tightness, coughing, and shortness of breath within hours of exposure. Additionally, air pollution has been linked to increased emergency department visits and hospital admissions.

Long-term or chronic exposure to air pollution increases the risk of various diseases, including stroke, heart disease, chronic obstructive pulmonary disease, and cancer. It is associated with oxidative stress and inflammation in human cells, which can contribute to the development of chronic diseases. Maternal exposure to air pollution during pregnancy can also have adverse birth outcomes, such as low birth weight, pre-term birth, and an increased risk of hypertensive disorders.

The impact of air pollution on health is not limited to physical ailments. Psychosocial stressors, such as poverty and racial/ethnic discrimination, can amplify the harmful effects of air pollution. Additionally, certain populations are more susceptible to the health impacts, including children, the elderly, pregnant women, and individuals with pre-existing chronic conditions. Disadvantaged communities of colour often face disproportionate exposure to air pollution due to discriminatory practices, further exacerbating health disparities.

Air pollution in the US

Despite improvements in air quality across the US, air pollution remains a significant issue, with millions of people exposed to unhealthy levels of pollution. According to the American Lung Association's 2025 "State of the Air" report, approximately 46% of Americans, or 156.1 million people, live in areas with failing grades for ozone or particle pollution. This is an increase of nearly 25 million people compared to the previous year's report, and it marks the highest number in the report's decade-long history.

The report highlights the disproportionate impact of air pollution on communities of colour. Despite making up 41.2% of the US population, people of colour account for 50.2% of those living in counties with failing air quality grades. Hispanic individuals, in particular, are nearly three times as likely as white individuals to reside in communities with failing grades across all three pollutant measures. This disparity underscores the environmental injustices faced by marginalised communities.

Geographically, the distribution of air pollution is shifting. While western states previously bore the brunt of poor air quality, the 2025 report shows a move eastward. Bakersfield, California, continues to top the list for the worst short-term and year-round particle pollution, a position it has held for six consecutive years. Meanwhile, Los Angeles earns the dubious distinction of having the worst ozone pollution in the nation for 25 out of the 26 years of reporting.

The primary sources of air pollution in the US include emissions from transportation, power plants, manufacturing, and residential energy use. Despite overall reductions in emissions, extreme heat, drought, and wildfires have exacerbated air pollution levels, particularly in central states like Minnesota and Texas. These climate-related factors contribute to the formation of ozone and particles, impair visibility, and pose significant health risks to millions of Americans.

The health impacts of air pollution are far-reaching and serious. Both ozone and particle pollution have been linked to premature death, asthma attacks, heart attacks, strokes, preterm births, and impaired cognitive functioning. Particle pollution, which includes fine particulate matter from wildfires, wood-burning stoves, and diesel engines, is especially deadly and has been associated with lung cancer. Addressing air pollution is not just an environmental concern but a critical public health imperative.

Air pollution in low-income countries

Air pollution is a significant issue in low-income countries, with far-reaching impacts on health, the environment, and socioeconomic development. According to the World Health Organization (WHO), 9 out of 10 people worldwide breathe air containing high levels of pollutants, and low- and middle-income countries suffer the highest exposures. This is due to various factors, including indoor pollution from solid fuel use for cooking and outdoor pollution from industrialization and older, more polluting technologies and vehicles.

Indoor air pollution is a significant issue in low-income countries due to the reliance on solid fuels, such as wood, coal, or biomass, for cooking and heating. The combustion of these fuels releases harmful pollutants, such as particulate matter, carbon monoxide, and volatile organic compounds, which can cause respiratory and cardiovascular diseases, among other health issues. Women and children, who typically spend more time indoors, are especially vulnerable to the effects of indoor air pollution.

Outdoor air pollution in low-income countries is often associated with industrialization and economic development. As countries shift from low to middle incomes, outdoor air pollution tends to increase due to factors such as rapid industrialization, outdated technologies, congested transport systems, and the use of polluting fuels. For example, power generation, agriculture, and waste incineration are significant sources of outdoor air pollution. The lack of stringent air quality regulations in some low-income countries can also contribute to higher pollution levels.

Socioeconomic inequalities are closely linked to air pollution exposure in low-income countries. Poorer communities, ethnic minorities, and marginalized groups often face higher exposure to pollutants due to residential segregation, proximity to pollution sources, and limited access to healthcare. As a result, air pollution can reinforce and exacerbate existing socioeconomic disparities, impacting health, well-being, and productivity within these vulnerable communities.

Addressing air pollution in low-income countries requires a range of interventions. Implementing cleaner technologies and fuels, improving energy efficiency, and promoting sustainable land use practices can help reduce pollution levels. Additionally, strengthening air quality regulations, improving healthcare access, and addressing socioeconomic inequalities can mitigate the impacts of air pollution on vulnerable populations. By tackling air pollution, low-income countries can improve public health, reduce environmental degradation, and promote sustainable socioeconomic development.

Air pollution sources

According to the World Health Organization (WHO), 99% of the global population breathes air that exceeds WHO guideline limits on pollutant levels. This equates to 7 million premature deaths per year. In the United States, 46% of the population (approximately 156 million people) live in areas with unhealthy levels of ozone or particle pollution.

Air pollution has multiple sources, which are often context-specific. Major outdoor pollution sources include residential energy for cooking and heating, vehicles, power generation, agriculture/waste incineration, and industry. Mobile sources, such as cars, buses, planes, trucks, and trains, are responsible for more than half of the air pollution in the United States. The primary mobile source of pollution is the automobile. Stationary sources, like power plants, oil refineries, and industrial facilities, emit large amounts of pollution from a single location. Area sources, such as agricultural areas, cities, and wood-burning fireplaces, are made up of smaller pollution sources that can have a significant collective impact. Natural sources, such as wind-blown dust, wildfires, and volcanoes, can also contribute to air pollution, although they typically do not create ongoing pollution problems.

Residential wood burning has been increasing over time, with wood fires being the most common reason for burning wood. In Minnesota, residential wood burning accounted for 55% of the state's direct fine particle emissions. Cars, trucks, trains, construction equipment, and agricultural equipment are also significant sources of air pollution. Older diesel engines, in particular, produce extremely high levels of particulate pollution.

At the local and regional levels, land use and public transit planning can encourage walking, biking, or the use of public transportation, reducing vehicle emissions. Federal regulations have played a significant role in reducing vehicle emissions by implementing standards for car manufacturing and fuel production. For example, the removal of lead from gasoline and the reduction of sulfur in diesel fuel have drastically reduced pollutants in the air.

In addition to transportation and energy, industrial processes such as iron, steel, and rubber product manufacturing, as well as power generation, produce polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs). PAHs are organic compounds containing carbon and hydrogen, while VOCs vaporize at or near room temperature and are released during the combustion of fuels like gasoline and natural gas.

Efforts to reduce air pollution

According to the World Health Organization (WHO), 9 out of 10 people, or about 99% of the global population, breathe air containing high levels of pollutants. This is causing an estimated 4.2 million premature deaths a year, with the number rising to an estimated range of 7.1 to 9.3 million when considering indoor air quality.

Air pollution is a health and environmental issue across all countries, with low- and middle-income countries suffering the highest exposures. The major outdoor pollution sources include residential energy for cooking and heating, vehicles, power generation, agriculture/waste incineration, and industry. As such, policies and investments that support sustainable land use, cleaner household energy and transport, energy-efficient housing, power generation, and better municipal waste management can effectively reduce key sources of ambient air pollution.

• The World Health Organization (WHO) works with countries to monitor air pollution and improve air quality. They have also developed and implemented strategies to raise awareness about the risks of air pollution and possible solutions.
• The European Union (EU) has implemented various directives to reduce air pollution and protect human health and the environment. For example, the National Emission Reduction Commitments (NEC) Directive aims to improve air quality and reduce premature deaths from air pollution. EU Member States are required to report and take action to reduce emissions.
• Finland's Ministry of the Environment plays a crucial role in air pollution control by preparing national objectives, participating in international cooperation, and developing legislation. The Finnish Environment Institute gathers national emissions data and coordinates the monitoring of air pollution impacts.
• Phasing out the use of coal and other fossil fuels for power generation is an effective way to improve air quality. Replacing coal-fired power plants with renewable energy sources can significantly reduce air pollution and benefit health.
• Electrifying public transport is another way to lower both air pollution and carbon emissions.
• The World Economic Forum, in collaboration with partners, has identified practical actions to improve health and reduce air pollution. Their report, "Air Pollution Interventions: Seeking the Intersection between Climate and Health," aims to guide governments and policymakers in implementing effective interventions.

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