The global picture is mixed, but the short answer is that air pollution improved in many places over the past decade, then stalled. Global concentrations of fine particulate matter (PM2.5) were 1.5 percent higher in 2023 than in 2022, and the worldwide average remains nearly five times the World Health Organization’s recommended safe level of 5 µg/m³. Roughly 99 percent of people on Earth breathe air that exceeds that guideline. In 2021 alone, air pollution was linked to 8.1 million deaths globally, about 22,000 per day.
Whether pollution is getting better or worse depends heavily on where you live and which pollutant you’re tracking. Some regions have made dramatic progress. Others are heading in the wrong direction. And a few wild cards, especially wildfires, are threatening to undo years of gains.
The Global Trend: Slow Progress, Now Stalling
Between 2000 and 2019, global PM2.5 exposure in cities declined at a modest rate of about 0.2 percent per year. That sounds small, and it is. It also masks enormous regional differences: 65 percent of the world’s cities actually saw PM2.5 levels rise during that period. The cities pulling the global average down were concentrated in the eastern United States, Europe, Southeast China, and Japan.
Nitrogen dioxide, a pollutant generated mainly by vehicles and power plants, moved in the opposite direction. It increased in 71 percent of cities worldwide at an average rate of 0.4 percent per year. Sub-Saharan Africa, the Middle East, and South Asia saw the steepest climbs, driven largely by rapid industrialization and growing vehicle fleets.
Ground-Level Ozone Is Quietly Getting Worse
While particulate pollution gets most of the headlines, ground-level ozone has been rising steadily and more broadly. Urban ozone exposure increased at 89 percent of monitoring stations worldwide, averaging about 0.8 percent per year. Summer ozone peaks rose at 74 percent of cities. The largest increases, above 3 percent per year, occurred in equatorial Africa, South Korea, and India.
Ozone is unusual because it’s not emitted directly. It forms when sunlight reacts with other pollutants like nitrogen oxides and volatile organic compounds. Paradoxically, reducing nitrogen dioxide in some areas can temporarily increase local ozone, because nitrogen dioxide also helps break ozone down. This chemical quirk means that even cities making progress on tailpipe emissions can see ozone climb. North America, Northern Europe, and Southeast China are among the few regions where summer ozone has actually declined, thanks to deep cuts in the precursor chemicals that fuel its formation.
Where Pollution Is Falling Fast
China is the clearest success story. After launching its “War on Pollution” in 2014, the country cut particulate pollution by 40.8 percent over the following nine years. That’s one of the fastest sustained improvements any nation has achieved. The gains came from closing coal-fired boilers, tightening vehicle emissions standards, and shifting heavy industry away from urban centers. However, 2023 brought a 2.8 percent uptick over the previous year, a reminder that progress isn’t automatic.
Europe and North America have seen steady, long-term improvements in PM2.5 and nitrogen dioxide. These regions benefited from decades of clean air regulation, the retirement of coal plants, and catalytic converters on vehicles. Their air still isn’t pristine by WHO standards, but the trajectory has been clearly downward for most pollutants.
Where Pollution Is Getting Worse
South Asia, sub-Saharan Africa, and the Middle East are moving in the wrong direction. These regions are industrializing rapidly, adding vehicles and factories faster than regulations can keep up. South Asia in particular faces some of the highest PM2.5 concentrations on the planet, driven by a combination of coal burning, crop residue fires, brick kilns, and vehicle exhaust.
Sub-Saharan Africa faces a compounding problem: population growth is outpacing efforts to reduce exposure. Even as the percentage of people cooking with solid fuels (wood, charcoal, dung) has dropped, the absolute number of people exposed to household air pollution has barely budged, falling by only about 10 percent since 1990 despite a 57 percent exposure rate dropping significantly in proportional terms. Indoor cooking smoke remains one of the leading health risks in these regions.
Wildfires Are Erasing Years of Progress
In the United States, wildfire smoke has emerged as a major threat to air quality gains. Since at least 2016, smoke has influenced average annual PM2.5 trends in nearly three-quarters of U.S. states. Nationally, wildfires have eroded about 25 percent of the progress made over previous decades in reducing particulate pollution. In many western states, that figure exceeds 50 percent.
The problem extends beyond annual averages. The number of days with extreme PM2.5 spikes, the kind that trigger air quality alerts, has been climbing since around 2011, particularly in western and midwestern states. Current U.S. clean air law doesn’t regulate wildfire-driven pollution the way it regulates industrial or vehicle emissions, leaving a significant gap. As the climate continues to warm and fire seasons lengthen, this contribution to air pollution is expected to grow.
Indoor Air Pollution Is Declining but Still Deadly
Globally, the health burden from household air pollution dropped by nearly 64 percent between 1990 and 2021, measured in disability-adjusted life years. That improvement reflects a massive shift away from cooking with wood, coal, and animal dung, particularly in East and Southeast Asia. But the problem is far from solved. About 2.7 billion people still cook with solid fuels, and the health toll remains substantial, contributing to lung disease, heart disease, stroke, and cataracts.
In sub-Saharan Africa specifically, population growth has largely offset reductions in solid fuel use, keeping the absolute number of exposed people stubbornly high. Indoor and outdoor pollution also compound each other: the fine particles from a cooking fire add to whatever ambient pollution is already in the air outside.
What the Numbers Mean for Health
The WHO’s recommended annual limit for PM2.5 is 5 µg/m³. Only about 1 percent of the global population lives in areas that meet it. The WHO also sets a series of less stringent interim targets, and 83 percent of countries (170 nations) meet the least ambitious of these, which allows up to 35 µg/m³. That gap between the interim target and the actual guideline illustrates how far most of the world still has to go.
Air pollution’s effect on life expectancy is significant. The University of Chicago’s Air Quality Life Index estimates that particulate pollution reduces average global life expectancy by almost two years. The burden falls disproportionately on people in South Asia and sub-Saharan Africa, where concentrations are highest and access to healthcare is most limited.
The Bottom Line on Trends
Particulate pollution has improved in wealthy nations with strong regulatory frameworks but worsened in fast-growing economies across Asia and Africa. Ground-level ozone is increasing almost everywhere. Wildfires are injecting a growing, largely uncontrolled source of pollution into regions that had been getting cleaner. And while indoor air pollution is declining as a proportion of global exposure, population growth in the most affected regions is blunting that progress. The global average hasn’t meaningfully improved in years, and 2023 saw a slight step backward.