Most countries share one common issue: polluted air

Most countries share one common issue: polluted air

Only 10 countries and territories out of 134 met the standards of the World Health Organization for a widespread form of air pollution, according to air quality data compiled by IQAir, a Swiss company. The contamination studied is called fine particles, or PM2.5, because it refers to solid particles less than 2.5 micrometers in size: small enough to enter the bloodstream. PM2.5 is the deadliest form of air pollution and causes millions of premature deaths each year.

“Air pollution and climate change have the same culprit, which is fossil fuels,” said Glory Dolphin Hammes, CEO of IQAir’s North American division. The World Health Organization establishes a guideline that people should not breathe more than 5 micrograms of fine particles per cubic meter of air, on average, for a year. The U.S. Environmental Protection Agency recently proposed tightening its standard from 12 to 9 micrograms per cubic meter.

The few clean air oases that meet World Health Organization guidelines are mostly islands, as well as Australia and the northern European countries, Finland and Estonia. Of the countries that did not achieve results, where the vast majority of the human population lives, the countries with the worst air quality were mainly in Asia and Africa. The four most polluted countries in IQAir’s ranking for 2023 (Bangladesh, Pakistan, India, and Tajikistan) are found in southern and central Asia.

Air quality sensors in nearly a third of the region’s cities reported fine particle concentrations that were more than 10 times higher than WHO guidelines. This was a proportion that “far exceeded any other region,” the report’s authors wrote. Researchers pointed to vehicle traffic, coal and industrial emissions, particularly from brick kilns, as the region’s main sources of pollution. Farmers who seasonally burn their crop waste contribute to the problem, as do households that burn firewood and dung for heat and cooking.

One notable change in 2023 was a 6.3% increase in air pollution in China compared to 2022, after at least five years of improvement. Beijing saw a 14% increase in PM2.5 pollution last year. The national government announced a “war on pollution” in 2014 and has been moving forward ever since. But the steepest decline in PM2.5 pollution in China occurred in 2020, when the coronavirus pandemic forced a slowdown or closure of a large part of the country’s economic activity. Dolphin Hammes attributed last year’s rebound to the reopening of the economy. And the challenges remain: 11 cities in China last year reported air pollution levels that exceeded WHO guidelines by 10 times or more, with Hotan, Xinjiang being the worst.

IQAir researchers analyze data from more than 30,000 air quality monitoring stations and sensors in 134 countries, territories, and regions. Some of these monitoring stations are managed by government agencies, while others are overseen by nonprofit organizations, schools, private companies, and citizen scientists. There exist large lagoons in ground-level air quality monitoring in Africa and the Middle East, including in regions where satellite data shows some of the highest levels of air pollution on Earth. As IQAir works to add data from more cities and countries in the coming years, the worst could be yet to come in terms of what we’re measuring.

Although North America is one of the cleanest regions in the world, in 2023 wildfires burned 4% of the forests in Canada, an area approximately half the size of Germany, and significantly affected air quality. Typically, the list of most polluted cities in North America is dominated by the United States. But last year, the top 13 spots went to Canadian cities, many of them in Alberta. In the United States, cities in the Upper Midwest and mid-Atlantic states also suffered significant amounts of PM2.5 pollution due to smoke from wildfires that crossed the border.

It’s not just chronic exposure to air pollution that harms people’s health. For vulnerable people, such as the very young and old, or those with underlying health conditions, breathing large amounts of fine particles over a few hours or days can sometimes be fatal. Around 1 million premature deaths per year can be attributed to short-term exposure to PM2.5, according to a recent global study published in The Lancet Planetary Health. The problem is worse in East and South Asia, as well as West Africa. Without taking short-term exposures into account, “we might be underestimating the mortality burden from air pollution,” said Yuming Guo, a professor at Monash University in Melbourne, Australia, and one of the study’s authors.

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