Geneva, Oct. 5 (Reuters): The World Health Organisation said on Thursday that drastically reducing air pollution in cities could prevent 120,000 deaths a year from respiratory infections, heart disease and lung cancer.

An estimated 800,000 people die prematurely each year from outdoor air pollution and a switch to cleaner fossil fuels could cut this toll by 15 percent, the United Nations agency said.

It issued its first global Air Quality Guidelines, based on consultations with more than 80 leading scientists over three years, which set voluntary targets for particulate matter pollution — which can be inhaled into the lungs and cause tissue damage — sulphur dioxide, nitrogen dioxide and ozone.

“We know that this will represent a major challenge for some cities around the world because it is not so easy to implement those targets,” Maria Neira, WHO’s director for public health and the environment, told a news briefing.

“If we reduce the level of pollutants to the standards we are recommending, the mortality caused by the outdoor pollution will be reduced by 15 percent,” the Spanish doctor said.

Indoor pollution — caused by solid fuels burned for heating and cooking — kills another 1.2 million, bringing the total number of premature deaths from air pollution to 2 million.

The worst-polluted cities for which data was available included Karachi, New Delhi, Kathmandu, Beijing, Lima and Cairo.

They had around 200 micrograms of particulate matter or PM 10 per cubic metre — 10 times the new standard, according to Michal Krzyzanowski, a WHO air quality expert who was tech-nical coordinator for the project.

The WHO’s projection for fewer deaths is based mainly on reducing PM 10, caused by burning fossil and other fuels, from a reference point of 70 micrograms per cubic metre down to 20.

London, which has made tremendous progress against pollution over the past decades, is roughly in the recommended range of 20 micrograms, according to Krzyzanowski.

“It should be stressed that health concerns are not limited to the most polluted cities. Substantial health effects are seen even in the relatively cleaner cities of Europe or North America where PM levels are three times lower,” he said.