Evaluation of the EPA's Oversight of State and Local Ambient Air Monitoring Operating Schedules: U.S. EPA Office of Inspector General Report

The United States Environmental Protection Agency (“EPA”) Office of Inspector General (“OIG”) issued on September 15th a report titled:

Evaluation of the EPA’s Oversight of State and Local Ambient Air Monitoring Operating Schedules (“Report”).

See Report Number 25-E-0051.

The stated objective of the Report was to evaluate whether EPA’s oversight and implementation of air quality monitoring resulted in underreported air pollution. 

The sampling of ambient air conditions is an important part of the process for determining whether an area is or will remain in compliance with the Clean Air Act National Ambient Air Quality Standards (“NAAQS”). EPA uses Clean Air Act authority and requires state and local monitoring agencies to establish a network of air monitoring stations. They use siting and operational criteria established by the federal agency to determine compliance with NAAQS. Further, EPA requires state and local agencies to conduct an assessment of their monitoring network periodically.

Note that the states are primarily responsible for assuring attainment and maintenance of each NAAQS in its air quality control region once EPA has established or revised them. Each state is then required to formulate, subject to EPA approval, an implementation plan (i.e., “SIP”) designed to achieve each NAAQS. The ability to demonstrate that the state has the capacity to adequately sample and monitor for each NAAQS is required to be demonstrated by the state.

EPA uses data from state and local monitors to calculate design values, which describe the air quality status of a given location when compared to the associated NAAQS. The federal agency publishes the calculated design values and undertakes a rulemaking process to determine whether an area’s air quality meets the NAAQS.

The OIG Report notes that some air monitoring sites operate daily. However, others are stated to operate on a predictable, intermittent schedule. The Report states:

…Typically, these intermittent air monitoring sites will operate once every 3, 6, or 12 days… the term “Pollution Gap” refers to the difference om average pollution measurements between an air monitoring site’s online and offline days when measured by alternative non-EPA monitoring methods.

The OIG Report conclusions included:

• Statistical analyses indicate that pollution levels increase when certain air quality monitoring sites are 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.
• 35.70 percent of sites that operated intermittently rather than daily had worse air quality on average when they were offline.
• The results of such analyses are stated to not indicate malicious behavior at any specific site but demonstrate that there is a risk of underreported air pollution.
• Two factors that may contribute to underreported air pollution include:
  • Because EPA publishes its intermittent air monitoring schedule on its website, it could create an opportunity for regulated entities to time peak emissions for when a monitoring site is offline.
  • Although EPA staff review air monitoring data, the EPA does not have the capacity to identify underreported air pollution within such a large volume of air quality data (creating opportunities for state and local air monitoring agencies to strategically turn off monitoring sites on days that they expect high pollution).
• In considering the Pollution Gap, the Report states that 18 percent of the air monitoring sites that had worse air quality when they were offline switch from indicating area attainment to indicating area nonattainment.

The Report makes two recommendations:

1. EPA’s Assistant Administrator for Air and Radiation should restrict the distribution of the intermittent monitoring schedule to state, local, and tribal air monitoring agencies and associated labs, and discourage broader dissemination of and access to the intermittent monitoring schedule.
2. EPA’s Assistant Administrator for Air and Radiation should implement a regular screening process that uses alternative air pollution measurements to detect monitoring sites that may be underreporting air pollution.

A copy of the Report can be downloaded here.