A National, Longitudinal Study of the Effects of Concentrated Hog Production on Ambient Air Pollution

The Environmental Protection Agency is considering regulation of large-scale hog producers under the federal Clean Air Act, but little is understood about livestock's effects on ambient air quality at the national level. I use the geographic changes in swine industry concentration between 1980 and 2002 to identify ambient air pollution attributable to this industry, controlling for numerous other factors. Doubling the number of hogs per square mile yields a 6.6% increase in sulfur-based ambient air pollution. Externality costs are estimated to be greater than possible regulatory requirements, suggesting societal gains from regulation. Copyright 2010, Oxford University Press.