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Only seven countries met World Health Organization (WHO) air quality standards last year, Reuters reported citing data compiled by Swiss air quality monitoring firm IQAir, as researchers warned that the war on smog would only get harder after the United States shut down its global monitoring efforts.
Chad and Bangladesh were the world's most polluted countries in 2024, with average smog levels more than 15 times higher than WHO guidelines, according to the report.
Only Australia, New Zealand, the Bahamas, Barbados, Grenada, Estonia and Iceland made the grade, IQAir said.
Significant data gaps, especially in Asia and Africa, cloud the worldwide picture, and many developing countries have relied on air quality sensors mounted on U.S. embassy and consulate buildings to track their smog levels, according to Reuters.
However, the US State Department has recently ended the scheme, citing budget constraints, with more than 17 years of data removed last week from the U.S. government's official air quality monitoring site.
The WHO recommends levels of no more than 5 mg/cu m, a standard met by only 17% of cities last year.
India, fifth in the smog rankings behind Chad, Bangladesh, Pakistan and the Democratic Republic of Congo, saw average PM2.5 fall 7% on the year to 50.6 mg/cu m.
But it accounted for 12 of the top 20 most polluted cities, with Byrnihat, in a heavily industrialised part of the country's northeast, in first place, registering an average PM2.5 level of 128 mg/cu m.