Magazine article Regulation

Air Pollution

Magazine article Regulation

Air Pollution

Article excerpt

"As the Wind Blows: The Effects of Long-Term Exposure to Air Pollution on Mortality," by Michael L. Anderson. September 2015. NBER #21578.

What are the health consequences of exposure to conventional fossil fuel emissions? The U.S. Environmental Protection Agency sets ambient air quality standards using research on mortality rates in different metropolitan areas that have different ambient pollution levels. Such observational studies infer causality between air quality and mortality through statistical controls, and thus are subject to all the doubts that accompany statistical inference.

Just as medicine increasingly has relied on clinical trials rather than observational studies to understand the effects of drugs, diet, and behavior on human health, economists have increasingly published the results of natural experiments in which people are exposed to pollutants in a manner that is plausibly random and health effects are observed. In my Working Papers column in the Winter 2012-2013 issue, I described a paper that examined the summer cap-and-trade system for nitrogen oxide (NOx) emissions in the Eastern and Midwestern United States and its effects on ozone levels and asthma drug expenditures.

This paper compares the mortality rates of people who live upwind and downwind of interstate highways in the Los Angeles metropolitan area where the winds often blow in the same direction. Many studies have measured air quality near major highways. Ultra Fine Particles (UFP) and NOx plumes don't decay to background levels until they get 600 meters downwind, while upwind levels decay to background levels within 100 meters. During "carmegeddon" in Los Angeles in July 2011, when Interstate 405 was shut down over a weekend and car emissions fell accordingly, UFP levels were 83 percent lower downwind but there was no change upwind. …

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