On December 7, 2020, EPA completed its five-year review of the National Ambient Air Quality Standards (“NAAQS”) for Particulate Matter (“PM”), a criteria air pollutant under the Clean Air Act. In a final action set to be published in the Federal Register in the coming days, EPA decided to retain the current NAAQS for PM, which have been in place since 2012.
PM is measured in two categories:
- Fine particles, or PM2.5, which are particles with a diameter of 2.5 micrometers and smaller; and
- Coarse particles, or PM10, which are particles with a diameters between 2.5 and 10 micrometers.
PM2.5, emitted from numerous sources including power plants, vehicle exhaust, and fires, is generally the more significant health concern, as it has been linked to serious respiratory disease, increased mortality rates, and recent studies have even linked a history of PM2.5 exposure to increased COVID-19 mortality rates.
The Clean Air Act requires EPA to set both primary and secondary NAAQS for PM2.5 and PM10. Primary NAAQS must be set at levels that will protect public health and secondary NAAQS must be set at levels that will protect public welfare. All NAAQS must be reviewed by EPA every five years. EPA has regulated PM emissions through the NAAQS since 1971, and revised the PM NAAQS four times since then—in 1987,1997, 2006 and 2012.
The current primary and secondary NAAQS for PM are as follows:
According to EPA data, there are currently 16 counties in the U.S. currently in nonattainment of the primary PM2.5 NAAQS and 23 counties currently in nonattainment of the primary PM10 NAAQS.
EPA’s decision to keep the existing PM NAAQS comes despite warnings from its own scientists. Notably, in the Policy Assessment for the Review of the National Ambient Air Quality Standards for Particulate Matter, one of the technical documents used by EPA in support of its final decision, EPA scientists concluded that:
“When taken together, we reach the conclusion that the available scientific evidence, air quality analyses, and the risk assessment…can reasonably be viewed as calling into question the adequacy of the public health protection afforded by the combination of the current annual and 24-hour primary PM2.5 standards.”
This Policy Assessment also states that under the current PM2.5 standards, long-term PM2.5 exposures are estimated to be associated with as many as 45,000 total deaths per year. However, the Policy Assessment also noted certain uncertainties and limitations in the evidence and risk assessments that could lead the agency to decide to keep the existing standards.
EPA received over 60,000 public comments on the PM NAAQS proposal, which was closely watched by environmentalists and industry alike. Because of this close public interest, this may be an issue that will be reviewed sooner than the normal five-year review once the Biden Administration begins in 2021.