Only seven countries met the World Health Organisation’s (WHO) air quality standards in 2024, according to data released on March 11, as researchers warn that the fight against smog faces mounting challenges following the closure of the US global air quality monitoring initiative.
Chad and Bangladesh topped the list as the most polluted countries, with average smog levels exceeding WHO guidelines by more than 15 times, based on figures from Swiss air quality monitoring firm IQAir. The only nations to meet WHO’s stringent air quality standards were Australia, New Zealand, the Bahamas, Barbados, Grenada, Estonia, and Iceland.
The US State Department recently terminated its air quality monitoring program due to budget constraints, removing more than 17 years of global data from its official platform, airnow.gov. This decision significantly impacts air quality monitoring in developing regions, particularly in Africa and Asia, where the US sensors were often the sole source of real-time data.
Chad, which had been excluded from IQAir’s 2023 list due to data concerns, reclaimed its position as the most polluted country in 2024. Contributing factors include Sahara dust and crop burning, with PM2.5 concentrations reaching 91.8 micrograms per cubic meter—far surpassing the WHO’s recommended level of 5 mcg per cu m.
India, ranked fifth behind Chad, Bangladesh, Pakistan, and the Democratic Republic of Congo, accounted for 12 of the top 20 most polluted cities. Byrnihat, in northeastern India, recorded the highest PM2.5 concentration at 128 mcg per cu m.
Experts warn that climate change is exacerbating pollution levels, with rising temperatures intensifying wildfires in regions such as Southeast Asia and South America. Researchers also emphasized the significant setback caused by the US program’s closure, which previously boosted air quality and life expectancy in monitored cities.
“This is a giant blow to air quality efforts worldwide,” said Ms. Christa Hasenkopf, director of the Clean Air Programme at the University of Chicago. The loss of reliable pollution data leaves at least 34 countries without critical resources needed to combat rising air pollution levels.