New York: Outdoor air pollution contributed to 3.3 million deaths worldwide in 2010, with wood-burning stoves in China and India and ammonia-belching farms in the West among the biggest culprits, according to a new study.

And if nothing is done, the annual toll from dirty air may double to 6.6 million premature deaths by 2050, with the biggest rise coming in Asia, researchers said on Wednesday in the journal Nature. The study used new atmospheric models and emissions data to offer a more comprehensive view of pollution sources and how the effects vary across the globe.

“If the projected increase in mortality attributable to air pollution is to be avoided, intensive air quality control measures will be needed, particularly in South and East Asia," wrote the researchers, led by Jos Lelieveld of Germany’s Max Plank Institute for Chemistry.

About a third of the deaths were caused by pollution from burning wood, diesel and other sooty fuels at homes and businesses, predominantly in Asia, according to the study. Agricultural operations were the second-biggest cause and a major pollution source in the eastern US, Europe, Russia and Japan, accounting for a fifth of deaths. More than 70% of the deaths were in Southeast Asia and the Western Pacific, the scientists said.

Ammonia from fertilizers and animals drifts into cities and is a key ingredient in producing ozone and microscopic pollutants known as fine particulates that damage the heart and lungs, Lelieveld said in an conference call with reporters.

Emissions from power plants, factories, vehicles and burning biomass accounted for almost a third of the deaths, the researchers found.

The impact of agriculture was “quite surprising" and shows how pollution needs to be viewed as a regional problem, Lelieveld said. “Much of the agricultural emissions that are being inhaled in a city like London are actually originating from outside the city." Bloomberg