Between 1978 and 2001, life expectancy in the United States rose by about three years—a trend that has a complex set of causes. But a big chunk of this life-expectancy increase—about five months—was the direct result of lower levels of fine-particulate pollution in the air, according to a study just published in the New England Journal of Medicine. In a few cities with especially dirty air, the reduction in particulates extended life expectancies nearly ten months. Why such staggering health improvements? Chronic exposure to particulates has been linked to a litany of health problems, from the predictable (lung cancer and chronic pulmonary disease) to the less obviously connected (heart disease and deep vein thrombosis).

What's more, particulates are only one of several classes of health-damaging pollutants released by coal, gasoline, and diesel when they're burned. When all of those pollutants are taken into account, cleaning up air pollution ranks among the most successful U.S. public health measures of the last few decades. It's enough to make you wonder why nobody's trying to frame the move away from fossil fuels as a public health issue, rather than just something indirectly connected to health through the slow-moving apparatus of climate change. Part of the explanation lies in the success of existing clean-air regulations, which have caused U.S. fossil-fuel consumption to pose less of a (direct) health problem than it once did. But developing countries don't regulate vehicle or power plant emissions as strictly as we do. Reducing fossil-fuel consumption in those countries with lax air-quality standards would be a huge boon to their citizens' health.

Back in 2007, the Intergovernmental Panel on Climate Change reported that between 30 and 50 percent of the global cost of mitigating greenhouse gas emissions would be made up for by the health benefits of reduced local and regional air pollution. The IPCC report cited studies showing that India could cut its emissions by 23 percent and China by 15 to 20 percent by taking measures that would pay for themselves in terms of public-health benefits. These studies, and others like them that help frame the question of emissions reductions in terms of immediate (and national) rather than eventual (and global) benefits, are precisely what American climate negotiators ought to be citing at this year's climate talks in Copenhagen as they try to persuade China and India to start reducing their own emissions.

--Rob Inglis