Air quality is deteriorating across the world with fewer cities meeting recommended safety levels, according to a new global report.
Data released by IQAir shows that only 14% of cities complied with guidelines set by the World Health Organization in 2025, down from 17% the previous year.
The decline has been linked to factors including wildfire smoke and the growing impact of climate change.
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The report, which analysed nearly 9 500 cities across 143 countries using PM2.5 measurements also highlighted major gaps in air quality monitoring, particularly in Africa and parts of West Asia.
These gaps widened after monitoring systems were disrupted when United States Embassy and Consulate sites stopped sharing public air quality data in March affecting 44 countries and leaving six without any monitoring at all.
According to the findings, Pakistan recorded the highest pollution levels in 2025 followed by Bangladesh, Tajikistan, Chad and the Democratic Republic of the Congo.
South Asia remained the most polluted region overall, although India dropped out of the top five most polluted countries for the first time since the rankings began.
Its average PM2.5 levels fell slightly but remained nearly ten times higher than the WHO's recommended limit.
At city level, pollution remained severe. New Delhi was once again ranked the world's most polluted capital with pollution levels around 20 times higher than recommended standards.
The report noted that worsening air quality in the Indian capital triggered rare public protests in November 2025 as hospitals saw an increase in patients suffering from asthma, heart conditions and breathing difficulties.
Authorities responded with temporary measures including school closures and construction bans but long-term solutions remain limited.
IQAir said increased monitoring can also make pollution appear worse. Its chief executive, Frank Hammes, said: "India is a victim of its success in monitoring... India is now discovering that air pollution is a very widely distributed problem."
Air quality was also affected by conflict, including the Russia-Ukraine War, as well as military activity involving Israel, the United States and Iran, although data from these regions remains incomplete.
In Africa, monitoring improved slightly with new data from countries such as Guinea, Eswatini, Tanzania, Benin and Morocco.
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However, the continent remains significantly underrepresented, raising concerns that many pollution hotspots go undetected.
"Globally, just 13 countries, regions, and territories saw annual average PM2.5 concentrations meeting the WHO annual PM2.5 guideline," the report said.
Despite the overall decline, some areas continue to record relatively clean air. French Polynesia was ranked the cleanest territory while Nieuwoudtville was identified as the least polluted location measured.
However, the report warned that such gains remain fragile.
"The 2025 data serves as a critical reminder that air quality is not a static achievement, but a fragile asset," it said, noting that wildfire activity had affected regions previously considered less polluted.
