By Kirk R. Smith, Special to CNN
Kirk R. Smith is a professor at the University of California-Berkeley and chair of the expert group evaluating household air pollution risks for the Global Burden of Disease, and the 2012 Tyler Laureate for Environmental Achievement. The views expressed are his own.
About the worst thing you can do is stick burning stuff in your mouth. Every year, tobacco kills more than six million people, according to the World health Organization. Including secondhand tobacco smoke affecting non-smokers, it is the chief cause of ill-health (measured as lost years of healthy life) among men globally and for everyone in North America and Western Europe.
The terrible disease burden imposed by tobacco is recognized by most people, but the risk of another form of smoke is also highlighted in the new "Global Burden of Disease" report released last Month in The Lancet -- smoke from cooking fires. About 40 percent of the world still cooks with solid fuels, like wood and coal, in simple stoves that release substantial amounts of the same kinds of hazardous chemicals found in tobacco smoke directly into the household environment. Indeed, a typical wood cookfire emits 400 cigarettes worth of smoke an hour.
This "household air pollution" is responsible for about 3.5 million premature deaths each year. Perhaps it is not surprising that the impact on health is so high when one considers that this smoke particularly affects a very vulnerable group -- poor women in developing countries.
Babies do not smoke, but do spend time in kitchens with their mothers. Thus, in addition household air pollution has a major impact on young children. The death toll includes half a million child pneumonia deaths.
Remarkably, although the new assessment did not address all possible risks to health, among the 60 major ones examined, household air pollution is second most important for women and girls, right between high blood pressure and obesity, two causes of disease impacting all countries. In the poorer regions, such as South Asia and most of Sub-Saharan Africa, where cooking with solid fuels is common, household air pollution is the most important single risk factor for women and girls.
Outdoor air pollution is also largely due to smoke from fuel burning. Some 3.3 million premature deaths annually are attributed to outdoor pollution across the globe. We now know that a good portion of this pollution actually comes from household cooking fuels -- more than a quarter in India, for example, and more than a sixth in China.
This pollution may start indoors in the kitchen of a poor family in a rural community, but after exiting the house, it spreads downwind to form part of the local and national outdoor pollution that affects millions more people.
This "secondhand cookfire smoke" adds nearly half a million to the death toll. Along with its primary impact, this brings the total impact of household air pollution to nearly 4 million premature deaths, by far the single most important environmental health risk in the world.