Report: Evaluation of the EPA’s Oversight of State and Local Ambient Air Monitoring Operating Schedules

Report # 25-E-0051, September 15, 2025
Why We Did This Report

The U.S. Environmental Protection Agency Office of Inspector General conducted this evaluation to determine whether the EPA’s oversight and implementation of air quality monitoring resulted in underreported air pollution.

Summary of Findings

Our statistical analyses indicate that pollution levels increase when certain air quality monitoring sites are offline. When some ambient air quality monitoring sites were offline, fine particulate matter air pollution increased on average by about 4 percent for daily monitoring sites and 9 percent for 1-in-3 monitoring sites. Further analyses indicated that 35.70 percent of sites that operated intermittently rather than daily had worse air quality on average when they were offline. While the results of our analyses do not indicate malicious behavior at any specific site, they demonstrate that there is a risk of underreported air pollution.

Report Materials

OIG Independence of EPA

The EPA's Office of Inspector General is a part of the EPA, although Congress provides our funding separate from the agency, to ensure our independence. We were created pursuant to the Inspector General Act of 1978, as amended.

Environmental Protection Agency | Office of Inspector General
1200 Pennsylvania Avenue, N.W. (2410T) | Washington, DC 20460 | 202-566-2391
OIG Hotline: 1-888-546-8740.