Girona was in 2025 the Catalan capital with the highest annual average of PM2.5 particles, with 9.9 micrograms per cubic meter, according to the latest world report on air quality prepared by the Swiss company IQAir. The city leads the ranking among the four Catalan capitals, although the differences with Tarragona and Barcelona are small.
After Girona is Tarragona, with 9.6 µg/m³, followed by Barcelona, with 9.2, and Lleida, with 7.9. The study highlights that the four cities are within the same range of the ranking, which groups values between 5.1 and 10 µg/m³.
Girona almost reaches double the threshold recommended by the WHO
The World Health Organization sets the recommended annual value for PM2.5 at 5 µg/m³. In the case of Girona, the annual average is almost double that threshold, although the city remains in the second least polluted range of the scale used by IQAir.
The report focuses on PM2.5 particles, one of the most used indicators to measure air pollution, although it reminds that air quality is also evaluated with other parameters, such as nitrogen dioxide.
A global analysis with 9.446 cities
The study corresponding to 2025 analyzes the presence of PM2.5 in 9,446 cities in 143 countries, regions, and territories. Its general conclusion is that only a minority of the cities studied strictly complies with the annual WHO guideline.
Globally, only 13 countries, regions, and territories recorded average annual concentrations within the recommended limit of 5 µg/m³. These include Andorra, Australia, Barbados, Bermuda, Estonia, French Polynesia, Grenada, New Caledonia, Panama, Puerto Rico, Réunion, and the U.S. Virgin Islands.
The Spanish city with the worst data is in Galicia
Within Spain, the highest concentration of PM2.5 was not registered in Catalonia, but in Ourense, with 18.5 µg/m³. It is, furthermore, the only city in the State included in the category that exceeds between three and five times the amount recommended by the WHO.
The report also warns that pollution episodes, forest fires, and meteorological conditions can alter the levels of these particles even in territories that usually present low records. In the Catalan case, the data place the four capitals above the recommended annual threshold, although still within a moderate pollution range in the scale used for this analysis.