Of these countries, seven had annual averages within the WHO’s guidelines of 5 micrograms per cubic meter in 2023: Australia, Estonia, Finland, Grenada, Iceland, Mauritius and New Zealand. French Polynesia, Bermuda and Puerto Rico also met the guidelines.
The United States ranked as the 33rd least polluted country, according to the report, with an average annual PM2.5 concentration of 9.1 micrograms per cubic meter. Columbus, Ohio, was the most polluted major U.S. city and Las Vegas was the least.
Last month, the U.S. Environmental Protection Agency finalized stricter standards for fine particulate matter, lowering the annual standard from 12 micrograms per cubic meter to 9 micrograms, a move it said reflects “new science on harms caused by particle pollution.”
Long- and short-term exposure to PM 2.5 is associated with heart attacks, strokes, asthma attacks and premature death, the EPA said, noting that communities of color and populations with lower socioeconomic statuses were at elevated risk. Air pollution has also been linked to signs of Alzheimer’s disease found in brain tissue, as well as several eye-related ailments, such as cataracts, glaucoma, conjunctivitis and age-related macular degeneration.
“PM 2.5 penetrates every cell of our bodies, from the cells in our skin to the cells deep in our lung, and even in our brain,” IQAir Global CEO Frank Hammes said at a recorded news conference. “Air pollution is the greatest environmental threat to human health,” he added.
The new EPA standard is set to be fully implemented in 2032, and the stricter limit could prevent up to 4,500 premature deaths and 290,000 lost workdays per year, the agency said. Its threshold for PM 2.5 pollution is still higher than the guidelines set by the World Health Organization.
According to IQAir report, Bangladesh, Pakistan and India had the highest annual averages for fine particulate matter pollution, with Bangladesh’s PM 2.5 levels averaging more than 15 times higher in 2023 than the WHO’s recommended threshold. Tajikistan, Burkina Faso, Iraq, the United Arab Emirates, Nepal, Egypt and the Democratic Republic of Congo were also among the top 10 most polluted countries last year.
Large portions of Africa, the Middle East and South America did not appear to have air quality measurements in an interactive map on the IQAir website because the data was not available, the company said.
A 2022 study published in the Lancet Planetary Health journal estimated that pollution was responsible for about 9 million premature deaths annually between 2015 and 2019, or 1 in 6 deaths worldwide. More than 90 percent of those deaths occurred in low- and middle-income countries, it said.
The study also estimated that deaths caused by “modern pollution risks factors” — the unintended consequences of industrialization and urbanization — rose more than 66 percent since 2000.
