Air pollution is causing more than three million premature deaths around the world every year, and the figure could be double that by the year 2050, a study suggests.
Pollutants including ozone and fine particulate matter — particles so small they're invisible to the naked eye — contribute to lung disease, heart disease and other serious health problems around the globe, researchers say.
Around three-quarters of the annual 3.3 million deaths occur in Asian, they note, with outdoor air pollution killing 1.4 million people annually in China and 650,000 in India.
"Strokes and heart attacks are responsible for nearly 75 percent of air pollution-related mortality," says Jos Lelieveld, an atmospheric scientist at the Max Planck Institute for Chemistry in Germany and lead author of the study published in the journal Nature.
"[A] little over 25 percent is related to respiratory disease and lung cancer," he adds.
Fine particulate matter, which is created during the burning of fossil fuels or organic matter, as well as from other sources, is of great concern because the small size of such particles makes them dangerous, experts say.
"They're so small that they can actually get deep into the lungs, into the alveoli, and get into your bloodstream," says New York University professor of population health and environmental medicine George Thurston, who was not involved in the study.
"These tiny chemical particles we breathe can get past the body's immune system and penetrate deep into the lungs and bloodstream, and they are not naturally removed from the body's airways," he says.
For the study, the researchers combined an atmospheric chemistry model with data on global health and population to look at the effects of pollution from seven sources: industry, commercial and residential energy use, power generation, agriculture, biomass burning, transport traffic and natural sources including dust storms.
Of those, emissions from residential energy usage involving fuels used in heating and cooking, mostly in China and India, were the leading cause of death globally, the researchers said.
"When most people think of outdoor air pollution, they tend to think of traffic and industry having the largest impact on global premature mortality, not residential energy emissions and agriculture," Lelieveld notes.
Knowing what air pollution sources are the most prevalent in any world region can help policy makers and legislators target them to help improve public health, researchers said.
"Everybody breathes the ambient air, so it affects everyone, so even small risks can translate into major burdens of disease," says Michael Jerrett from the Department of Environmental Health Sciences at the University of California, Los Angeles, in a commentary accompanying the published study.
