Nitrogen dioxide pollution kills thousands every year. Here's how to prevent it

Tens of thousands of European city dwellers die prematurely each year due to air pollution, researchers said on Wednesday in a study ranking more than 800 cities according to the risk of early death from two leading pollutants.

The study, published in "The Lancet Planetary Health", analysed the risk in each place from exposure to nitrogen dioxide - a poisonous gas contained in car exhaust, and to fine particulate matter, which can include smoke, dust and ash.

Researchers then created an online tool allowing residents to see where their city places on the ratings tables, together with data comparing their air quality with that of other urban hubs.

"Cities are hotspots of air pollution," said lead author Mark Nieuwenhuijsen from the Barcelona Institute for Global Health, adding that he hoped the comparison site would help raise awareness of a "silent killer".

"It's a very good tool for people to see what's happening in their city ... and they really should use that information to push for action," he said.

Researchers in the new study used city-specific data on air quality to calculate what percentage of deaths were attributable to exposure to nitrogen dioxide pollution and fine particulate matter.

Some 51,000 premature deaths from fine particulate matter and 900 from nitrogen dioxide pollution could be prevented each year if cities reduced the pollutants to levels recommended by the World Health Organization, they calculated.

Madrid topped the nitrogen dioxide pollution ranking, where researchers calculated up to 7% of all natural deaths were caused by the pollutant, followed by Antwerp, Turin, Paris and Milan.

Cities in Italy's Po Valley, southern Poland and the eastern Czech Republic were seen at highest risk of death from fine particulate matter, which comes from a wider range of activities including industry, household heating and coal fires.

Northern European countries such as Iceland, Norway and Sweden dominated the list of cities with the lowest rates of deaths attributable to both pollutants.

Air pollution is responsible for about seven million premature deaths worldwide each year, according to the United Nations, which has called for the risk to be treated as a human rights issue. Nitrogen dioxide pollution in particular has been the primary reason for these deaths.

The study underlines the largely hidden impact of air pollution in cities, said Matt Whitney from The Clean Air Fund.

"Very few people are aware of the massive impact that it has on health," he told the Thomson Reuters Foundation.

He called for city authorities to take action including reducing dirty fossil fuels, encouraging sustainable transport and investing in green spaces to tackle nitrogen dioxide pollution.