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Tlaxcalancingo was the most polluted city in Mexico in 2025 in terms of fine particulate matter (PM2.5). Throughout the year, the city recorded an average concentration of 32.6 micrograms per cubic meter. By comparison, the national capital Mexico City reported an average level of 19.4 micrograms per cubic meter.

How severe is fine air pollution in Mexico?

Fine particulate matter (PM2.5) consists of particles smaller than 2.5 micrometers in diameter. Due to their small size, these particles can penetrate deep into the lungs and enter the bloodstream, contributing to respiratory conditions such as asthma and allergies, as well as increasing the risk of cardiovascular and respiratory diseases.

The World Health Organization recommends an annual average limit of 10 µg/m³. However, Mexico's average PM2.5 concentration exceeded 17 µg/m³ in 2025, placing the country 50th place globally in terms of air pollution levels.

Where are the world’s most polluted cities?

Although pollution levels in Mexico exceed WHO recommendations, Mexico City didn’t even make it to the top 25 most polluted capital cities in 2025. That year, Loni in India topped the global ranking, with an average PM2.5 concentration of nearly 112.5 µg/m³. Overall, the majority of the most air polluted cities worldwide in 2025 were located in India and Pakistan.