The list from the European Union (EU) agency includes 761 cities, 23 of which are Portuguese, ordered into 10 levels from the cleanest to the most polluted or with the lowest to the highest “total mortality risk values”.

The risk is associated with prolonged exposure to fine particles (PM2.5), nitrogen dioxide (NO2) and tropospheric ozone (O3) in the last two years.

The cities with the cleanest air are Oulu and Jyvaskyla, both in Finland, followed by Umea (Sweden), Kuopio (Finland) and Uppsala (Sweden), in fifth place.

Faro appears in 28th position, Viana do Castelo in 53rd and Viseu in 58th, all with the lowest risk (up to 10%), while Setúbal (101), Póvoa do Varzim (109), Sintra (128), Coimbra (138), Vila Franca de Xira (140) and Almada (150) are classified in the second level (from 10% to 20%).

At level 4 (30% to 40%) are Seixal (172), Guimarães (182), Paredes (191), Amadora (193), Aveiro (195), Barreiro (200), Odivelas (241), Braga (257) and Vila Nova de Gaia (266), with the next level (40% to 50%) being Gondomar (315), Valongo (327), Matosinhos (345), Lisbon (348) and Porto (372).

The last cities on the list are Vicenza (Italy), in the 760th position, and Slavonski Brod (Croatia), in the 761st, with an estimated risk of 90% to 100%.

The air quality viewer for European cities has been published since 2019 and allows users to see how their city is performing, has been updated in terms of methodology regarding how the ratings are calculated.

The EEA has also updated its European Air Quality Index, launched in 2017, which “helps users better understand local air pollution and its impact on health.”

The service now provides “hourly updates of data on concentrations of key air pollutants from more than 3,500 monitoring stations across Europe.”

The index is determined using a combination of up-to-date data reported by ERA member countries and air quality forecasts provided by the EU’s Copernicus Atmospheric Monitoring Service (CAMS).