Sized-based Regulation and Environmental Quality: Evidence from the US Livestock Industry

Chen-Ti Chen, Gabriel E. Lade, John M. Crespi, David A. Keiser
January 2024  [24-WP 657]

Download Full Text

Suggested citation:

Chen, C.T., G.E. Lade, J.M. Crespi, and D.A. Keiser. 2024. "Sized-based Regulation and Environmental Quality: Evidence from the US Livestock Industry." Working paper 24-WP 657. Center for Agricultural and Rural Development, Iowa State University.


The growing prevalence of animal feeding operations (AFOs) in the United States raises concerns among the public and regulators about their impact on local environmental quality. This paper studies the effects of Clean Water Act regulations that targeted water pollution from the largest hog AFOs. We compile a novel dataset linking historical regulatory records of AFOs in Iowa to downstream surface water pollution monitors. The regulation decreased ammonia concentrations downstream of large AFOs by 6 to 9 percentage points and modestly improved dissolved oxygen concentrations, but did not reduce phosphorus concentrations. Pollution reductions are largest during heavy precipitation months, consistent with the regulations reducing on-site spills and nutrient runoff from local fields. However, we find that pollution increased downstream from mid-sized AFOs, which were exempt from the regulations. Given the growth in the number of mid-sized facilities relative to large AFOs, we estimate that the regulation had little discernible impact on overall water quality.