A new interactive map has made it possible to find out the quality of air in real-time in cities and regions across Europe, where air pollution is the single biggest environmental health risk.

Air pollution is an invisible killer, so the air quality index is needed to inform European citizens on the state of the air they breathe. Karmenu Vella EU Environment Commissioner

The map, dubbed the European Air Quality Index, allows users to find out whether the air they’re breathing is safe, based on hourly data from more than 2,000 air quality monitoring stations across Europe.

Launched by the European Environment Agency (EEA) and the European Commission this week, the map assesses air quality based on five key pollutants that harm people’s health and the environment: particulate matter (PM2.5 and PM10), ground-level ozone (O3), nitrogen dioxide (NO2) and sulphur dioxide (SO2).

The five pollutants have been linked to diseases including lung cancer, Type 2 diabetes and heart disease.

The most dangerous of all, PM2.5, which is found in vehicle and industrial emissions, caused the premature death of an estimated 400,000 Europeans in 2014.

In the UK, London, Norwich and Leicester are among the cities to have fallen into the “moderate” category in the past 24 hours because of high levels of PM 2.5 and NO2, while most places ranked as “good” or “fair”.

Elsewhere in the continent, cities in Poland, the Czech Republic and Spain were among those to fall into the “very poor” category for high levels of PM2.5 and PM10.

Meanwhile, Sweden, Norway and Finland had some of the cleanest air.

“Air pollution is an invisible killer, so the air quality index is needed to inform European citizens on the state of the air they breathe,” EU Environment Commissioner Karmenu Vella said in a statement.

The launch of the map comes just weeks after the EEA released its annual Air Quality in Europe report, which showed that most people living in Europe’s cities are still exposed to levels of air pollution deemed harmful by the World Health Organization.

As he launched the index at the Clean Air Forum in Paris on Thursday (November 16), EEA Executive Director Hans Bruyninckx said the information in the map is “an important basis for a dialogue and decisions that are needed to safeguard people’s health”.