Hung Chung Chih /

Cars are dangerous, but not only because they’re made of several tons of glass and steel, and move at high speeds through densely populated areas. A recent study found that tailpipe emissions are responsible for millions of premature deaths in rapidly expanding countries like China and India. Cars in these countries aren’t subject to the same air quality restrictions they are in Europe and the U.S., and that has led researchers to call vehicle exhaust the fastest-growing cause of death in the world.

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The study, published recently in the Lancet, assessed risk factors for disease, injury, and death in 21 regions of the world between 1990 and 2010. Over this twenty-year period, the researcher found that the contribution of different risk factors to disease burden has changed substantially, with a shift away from risks for communicable diseases in children towards those for non-communicable diseases in adults. “These changes are related to the aging population, decreased mortality among children younger than 5 years, changes in cause-of-death composition, and changes in risk factor exposures,” explain the authors. “New evidence has led to changes in the magnitude of key risks including unimproved water and sanitation, vitamin A and zinc deficiencies, and ambient particulate matter pollution.

What this means in lay terms is that increased exposure to air pollution, particularly the sooty kind that spews from the exhaust pipes of cars and trucks, is contributing directly to the premature deaths of more people than ever before in the history of our species. These deaths tend to be concentrated in regions where there has been a massive shift toward personal vehicle ownership in the last decade or so. In 2010, more than 2.1 million people in Asia died prematurely from air pollution, mostly from the minute particles of diesel soot and gasses emitted from cars and lorries. Of these deaths 1.2 million were in east Asia and China, and 712,000 in south Asia, including India. Poorly constructed infrastructure in these countries often leads to massive traffic jams where people spend hours idling their engines but going no where.

But don’t think for a minute that this problem is limited to developing nations. Worldwide, a record 3.2 million people a year died from air pollution in 2010, compared with 800,000 in 2000. It now ranks for the first time in the world’s top 10 list of killer diseases, according to the Global Burden of Disease study. If the figures for outdoor air pollution are combined with those of indoor air pollution, caused largely by people cooking indoors with wood, dirty air would now rank as the second highest killer in the world, behind only blood pressure, reports the Guardian.

+Global Burden of Disease Study