Helena Joyce
Air pollution is a pressing health and environmental issue worldwide, contributing to one in ten global deaths and disproportionately affecting low-income countries. While air quality has improved in recent decades due to regulatory measures and technological advancements, new challenges, such as climate change and rising temperatures, threaten to undermine this progress. This is particularly evident in the US, where air pollution levels have risen since 2016, reversing previous positive trends. This complex issue demands attention and action from policymakers and society as a whole to safeguard public health and the environment. This article will explore the extent to which pollution has increased in the last 20 years and the factors driving these changes.
| Characteristics | Values |
|---|---|
| Annual rate of increase in atmospheric carbon dioxide over the past 60 years | 100-200 times faster than previous natural increases |
| Ocean acidity increase | 30% |
| Annual emissions of carbon dioxide from burning fossil fuels | 11 billion tons in the 1960s, 37.4 billion tons in 2024 |
| Air pollution contribution to global deaths | 1 in 10 |
| Air pollution death rate in low-income countries | Often the leading risk factor |
| US air pollution | 66 million tons of pollution emitted into the atmosphere in 2023 |
| US air quality | About 140 million people lived in counties with pollution levels above the primary NAAQS in 2023 |
| US air quality improvement | Total emissions of the six principal air pollutants dropped by 78% between 1970 and 2023 |
| US air quality trends | National concentrations of air pollutants have dropped significantly since 1990 |
| US air toxics emissions | Decreased by 74% from 1990 to 2017 |
| US air pollution trends | Ambient monitoring data shows that some toxic air pollutants, such as benzene, 1,3-butadiene and several metals, are declining at most sites |
| US air pollution | Nearly half the population lives where air quality earned an F in "State of the Air" 2025 |
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What You'll Learn
Air pollution's impact on health
Air pollution is defined as the presence of one or more contaminants in the atmosphere, such as dust, fumes, gas, mist, odour, smoke or vapour, in quantities and durations that can be harmful to human health. The impact of air pollution on human health depends on the type of pollutant, the level and length of exposure, and other factors, including individual health risks and the cumulative impacts of multiple pollutants.
The main pathway of exposure to air pollution is through the respiratory tract. Pollutants such as fine particulate matter (PM), carbon monoxide (CO), ozone (O3), nitrogen dioxide (NO2), and sulphur dioxide (SO2) can penetrate deep into the lungs, enter the bloodstream, and travel to organs, causing systemic damage to tissues and cells. This can lead to inflammation, oxidative stress, immunosuppression, and mutagenicity in cells throughout the body, impacting the lungs, heart, and brain, among other organs, and ultimately leading to disease.
Short-term exposure to high levels of particulate matter can lead to reduced lung function, respiratory infections, and aggravated asthma. Long-term or chronic exposure increases the risk of non-communicable diseases, including stroke, heart disease, chronic obstructive pulmonary disease, and cancer. Maternal exposure to air pollution has also been linked to adverse birth outcomes, such as low birth weight, pre-term birth, and small gestational age births.
In addition to the health impacts, air pollution can have economic consequences, including missed workdays and higher medical costs for individuals, as well as societal costs related to healthcare expenditures and lost productivity.
While there has been progress in reducing air pollution in recent decades, with a decrease in emissions of air toxics and improvements in air quality in some regions, the changing climate is making it harder to sustain these gains. Climate change increases the risk of wildfires, which contribute to dangerous particle pollution, and extreme weather events can further degrade air quality.
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The rise of atmospheric carbon dioxide
The rise in atmospheric carbon dioxide over the last 20 years has been driven by human activities, specifically the burning of fossil fuels. Carbon dioxide (CO2) is a heat-trapping gas, also known as a greenhouse gas, that is released into the atmosphere when fossil fuels like coal, oil, and natural gas are extracted and burned.
Before the Industrial Revolution, CO2 levels in the atmosphere were consistently around 280 parts per million (ppm) for thousands of years. However, since the start of the Industrial Revolution in the 18th century, human activities have raised atmospheric CO2 levels by more than 50%. This means that the amount of CO2 in the atmosphere today is around 150% of its pre-industrial levels.
The increase in atmospheric carbon dioxide has not been linear but has accelerated over time. In the 1960s, atmospheric CO2 increased by about 0.8 ppm per year. This rate of increase doubled to 1.6 ppm per year in the 1980s and remained at 1.5 ppm per year in the 1990s. However, in the last decade (2015-2024), the annual increase has accelerated to 2.6 ppm per year. As a result, the annual rate of increase in atmospheric carbon dioxide over the past 60 years is about 100 times faster than previous natural increases, such as those that occurred at the end of the last ice age.
Global carbon dioxide emissions from fossil fuels and industry have also been increasing. In 1950, global CO2 emissions were 6 billion tonnes. By 1990, this had almost quadrupled to more than 20 billion tonnes. The latest data shows that global CO2 emissions totaled 37.01 billion metric tons in 2023 and are projected to have risen to a record high of 37.41 billion metric tons in 2024. This represents a more than 60% increase in global CO2 emissions since 1990.
The COVID-19 pandemic caused a temporary annual drop in CO2 emissions in 2020 as a result of lockdowns and restrictions. However, emissions quickly bounced back as countries resumed their economic activities, with 2021 surpassing 2019 levels. While absolute emissions continue to rise, global per capita emissions have not increased since 2011, indicating a transition towards renewable energy and clean technologies.
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The Clean Air Act's effectiveness
The Clean Air Act has been highly effective in reducing air pollution and improving air quality in the United States. The Act, first passed in 1970, gave the Environmental Protection Agency (EPA) the authority to regulate air pollutants and polluting industries, with subsequent amendments in 1977, 1990, and 2025.
The Clean Air Act has successfully targeted the reduction of six major pollutants: ozone (O3), particulate matter (PM), carbon monoxide (CO), sulfur dioxide (SO2), nitrogen dioxide (NO2), and lead (Pb). The EPA has set emissions standards for various sources, including passenger vehicles, heavy-duty trucks, buses, construction and farm equipment, and marine engines. These standards have led to significant improvements in vehicle pollution control, with new passenger vehicles being 98-99% cleaner for most tailpipe pollutants compared to the 1960s. The Act has also facilitated the phase-out of leaded gasoline, resulting in a 98% decrease in airborne lead concentrations between 1980 and 2005.
The Clean Air Act Amendments of 1990 were particularly significant, introducing provisions for a national permits program, implementing the Montreal Protocol to address ozone depletion, and establishing a market-based cap-and-trade program to control acid rain. This program has led to substantial reductions in sulfur dioxide and nitrogen dioxide emissions. The amendments also required the EPA to identify categories of industrial sources for nearly 190 toxic air pollutants, enabling the agency to mandate the installation of pollution controls or changes in production processes.
The Clean Air Act has had a positive impact on public health and the environment. For every dollar spent on emission reduction programs, the American people receive nine dollars worth of benefits in improved health and environmental protection. The Act has contributed to reduced mortality rates and improved longevity and quality of life for Americans.
Despite these successes, challenges remain. In 2023, about 66 million tons of pollution were emitted into the United States' atmosphere, and approximately 140 million people lived in counties with pollution levels above the acceptable standards. The transportation sector remains a significant source of carbon pollution, and the EPA is working to develop standards for aircraft emissions. Additionally, the Clean Air Act faces threats from legislative and executive branches of the government.
Overall, the Clean Air Act has been instrumental in reducing air pollution, improving air quality, and protecting public health in the United States. While progress has been made, continued efforts and the full implementation of the Act's regulations are necessary to address remaining challenges and ensure sustained improvements in air quality.
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The role of wildfires in air pollution
While there has been a reduction in some air pollutants since 1980, wildfires continue to play a significant role in air pollution. Wildfires release a range of pollutants into the atmosphere, including black carbon, carbon monoxide, nitrogen oxides, and particulate matter. These emissions can vary depending on the amount and type of fuel, meteorology, and burning conditions.
Burning trees release carbon and particulate matter, causing a decline in air quality. Wildfires are closely linked to climate change and air pollution, with human activities such as burning fossil fuels, transportation, and industrial processes releasing greenhouse gases and black carbon emissions. These pollutants trap heat in the atmosphere, leading to a rise in global temperatures and more erratic weather patterns, increasing the likelihood of wildfires.
The relationship between wildfires, climate change, and air pollution forms a vicious cycle that poses a severe threat to people, animals, and the planet. For instance, the Australian wildfires during 2019-20 produced carbon emissions estimated to be 1.6 times greater than the country's total emissions for that year. Similarly, fires near the Canadian Arctic blanketed the US eastern seaboard in toxic smoke for weeks.
Large and extended wildfires can have significant respiratory health impacts and contribute to premature mortality. Smoke plumes from wildfires can elevate PM2.5 and O3 levels above health standards, affecting regions directly or mixing with other urban pollutants. In the United States, wildland fire emissions represented approximately 32% of total primary PM2.5 emissions, with fires in eleven western states emitting twice as much primary PM2.5 compared to annual emissions from all industrial sources in the region.
To address the issue of wildfires and their impact on air pollution, governments should adopt a joined-up approach that recognizes the interconnectedness between climate change, air pollution, and wildfires. Measures to reduce black carbon emissions, such as community engagement in forest management, can help prevent wildfires while also improving public health and mitigating climate change.
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How air pollution affects low-income countries
Air pollution is a significant health and environmental issue worldwide, but its impact is more severe in low-income countries. While air pollution has decreased in many countries over the last 20 years, it continues to be a pressing issue in low-income regions, where industrialization, energy consumption, and population growth drive emission levels upward.
In low-income countries, the burden of air pollution falls disproportionately on vulnerable populations. People in low-income groups are more likely to work outdoors or in physical labor, exposing them to higher levels of pollutants. They are also more likely to depend on polluting, low-cost fuels like charcoal, kerosene, or firewood for cooking and lighting, leading to high indoor pollution rates.
The health risks associated with air pollution are more acute for low-income households due to limited access to quality healthcare. Studies show that low-income communities suffer from higher rates of pollution-related diseases, including heart disease, stroke, respiratory infections, and lung cancer. In India, for example, air pollution-related mortality risks are two to three times higher than in high-income countries.
Additionally, low-income countries tend to have less developed healthcare systems, exacerbating the impact of air pollution on vulnerable populations. Weak laws, less stringent vehicle emission standards, and prevalent coal power stations in developing countries further contribute to poor air quality.
The interplay between pollution, exposure, and poverty highlights the vulnerability of those living in low-income countries. Approximately 716 million people living on less than $1.90 per day are exposed to unsafe levels of air pollution, with a significant number residing in Sub-Saharan Africa.
Addressing air pollution in low-income countries requires collective action from governments, industries, and citizens. Initiatives like the Breathe Life campaign, which encourages reducing emissions and adopting clean technologies, are essential steps toward improving air quality and mitigating the disproportionate impact of air pollution on low-income communities.
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Frequently asked questions
It depends on the type of pollution and the region in question. For instance, in the US, emissions of key air pollutants have declined since 1990, with a 74% decrease in air toxics between 1990 and 2017. However, there was a 5.5% increase in fine particulate pollution across the country between 2016 and 2018, reversing a decades-long trend of improving air quality.
The six common pollutants are PM2.5, PM10, SO2, NOx, VOCs, CO, and Pb.
PM2.5 refers to fine particulate pollution, which consists of particles less than 2.5 micrometres in diameter. These particles can cause a range of health problems, including asthma, respiratory inflammation, lung cancer, heart attacks, and strokes.
Climate change has increased the risk of wildfires, which produce smoke that spreads dangerous particle pollution. Additionally, the changing climate has made it more challenging to maintain air quality standards, as extreme heat, drought, and wildfires contribute to increases in ozone and particle pollution.
