April 11, 2022 – The Emmett Environmental Law & Policy Clinic submitted comments today on behalf of a group of leading scientists supporting the Environmental Protection Agency’s (EPA) proposal to reaffirm earlier findings underlying the agency’s regulation of mercury and other toxic air pollutant emissions from coal-fired power plants.

The Clinic filed the comments on behalf of Elsie Sunderland, Charles Driscoll, Jr., Joel Blum, and Celia Chen—leading experts in the atmospheric transport, aquatic fate, bioaccumulation, human exposures, and health outcomes associated with mercury contamination of the environment.  Emmett Clinic Acting Director Shaun Goho wrote the comments in collaboration with Clinical Fellow Tommy Landers.

EPA regulates emissions of toxic air pollutants such as mercury under section 112 of the Clean Air Act.  When Congress amended the Act in 1990, it directed EPA to set emissions standards for all major sources of 189 toxic air pollutants under a strict timeline.  The one exception was emissions from coal-fired power plants.  In those same 1990 amendments, Congress had created the acid rain cap-and-trade program—which applied only to coal-fired power plants—and Congress anticipated that the controls installed by power plants to reduce sulfur dioxide emissions might also reduce emissions of mercury and other air toxics.  Therefore, Congress instructed EPA to determine whether it was “appropriate and necessary” to regulate power plant emissions under section 112 after taking into account the effect of the acid rain program.

In the end, power plants largely complied with the acid rain program by switching to low-sulfur coal, and coal-fired power plants remained the leading source of mercury emissions in the United States.  EPA therefore determined in 2000 that it was appropriate and necessary to regulate toxic air pollutant emissions from power plants.  It confirmed this finding in 2012 and imposed emissions standards at that time.  All coal-fired power plants have been in compliance with those standards since 2019.

Nevertheless, in 2019, EPA proposed to reverse its prior findings and conclude that it was not “appropriate” to regulate these emissions.  On behalf of several scientists (including the signatories of the comments filed today), the Clinic filed comments opposing the 2019 proposal for several reasons.  Overall, the Clinic argued that EPA based its proposal on (i) outdated and very incomplete data on benefits and (ii) an over-emphasis on previously predicted compliance costs, even though the actual costs were about one tenth of the predicted costs.  In 2020, EPA finalized its finding that the mercury and air toxics standards were no longer “appropriate.”

Earlier this year, EPA proposed to revoke that 2020 decision and reaffirm that regulating mercury and air toxics is “appropriate and necessary.”  The Clinic’s comments filed today stated strong support for the latest proposal.  While the comments also identify areas for improvement in the scientific analysis and benefits quantification – including using a state-of-the-science assessment of mercury deposition attributable to power plants, and considering how power plants’ emissions affect individuals’ cumulative exposure to mercury – any such improvements would only strengthen the “appropriate and necessary” finding.

The Clinic’s comments are available here: Comments on Proposed Revocation of the 2020 Reconsideration, and Affirmation of the Appropriate and Necessary Supplemental Finding, 87 Fed. Reg. 7624 (Docket ID No. EPA-HQ-OAR-2018-0794)