Study in China First to Show Air Pollution Shortens Human Lives

Particulate matter air pollution is the greatest current threat to human health globally. Its microscopic particles penetrate deep into the lungs and filter into the bloodstream. From there, they can eventually lead to lung disease, cancer, strokes, or heart attacks. Yet, in spite of these risks, the relationship between particulate matter air pollution levels and human health is not well understood by society at large.

To quantify the link between long-term exposure to air pollution and human health, UChicago scholar Michael Greenstone and his colleagues exploited a unique “natural” experiment in China known as the Huai River Policy. Under this program, first introduced in the 1950s, residents who lived north of China’s Huai River received free, coal-based winter heating. But for residents south of the river, heating was prohibited. Further, the stringent restrictions on migration in this period meant that people’s lifetime exposure could be measured accurately. The research design also allowed Greenstone’s team to isolate the effect of air pollution from other factors that affect health, and to do so at the very high concentrations that prevail in China, India, Thailand, Indonesia, and other countries today.

The research produced two major findings. First, air pollution levels just north of the Huai River were 50 percent higher than those just to the south. Second, residents in Northern China exposed to these pollution levels lived on average 3 years fewer than people in the South—a major finding in health and environmental science and economics.

But China is not the only country with high pollution level. Realizing they had a unique opportunity to leverage this insight to inform people all over the world about the health effects of the air they breathe and to have broad policy impact, Greenstone and the team at EPIC set out to “globalize” the findings of the Huai River research. They did so by combining the relationship between pollution and life-expectancy with satellite-derived, hyper-local particulate matter measurements for the entire world. Together, they resulted in the Air Quality Life Index (AQLI), a first-of-its-kind pollution index that allows users anywhere on Earth to zoom in to their community and understand the effect of the air they breathe on their life expectancy.

“The results greatly strengthen the case that long-term exposure to particulates air pollution causes substantial reductions in life expectancy. They indicate that particulates are the greatest current environmental risk to human health, with the impact on life expectancy in many parts of the world similar to the effects of every man, woman and child smoking cigarettes for several decades. The histories of the United States, parts of Europe, Japan and a handful of other countries teach us that air pollution can be reduced, but it requires robust policy and enforcement.”

Michael Greenstone, Milton Friedman Distinguished Service Professor in Economics