How and Why the U.S. EPA Is Changing its Policy on Mercury

The U.S. EPA has proposed a change in how it calculates the benefits of the Mercury and Air Toxics Standards (MATS) for coal- and oil-fired power plants. By excluding 'co-benefits'—reductions in pollutants not directly targeted by the rule, such as particulate matter (PM2.5)—the EPA argues that the regulation is no longer 'appropriate and necessary' under the Clean Air Act. While the MATS originally prevented 11,000 premature deaths and 130,000 asthma attacks annually, removing co-benefits, which account for over 90% of monetized benefits, dramatically lowers the perceived value of the regulation relative to its compliance costs. Although the MATS remain in place for now, this methodological shift opens the door for the EPA to potentially rescind the standards or delist power plants as affected sources. Electric utilities have expressed concern over this shift, noting they have already invested over USD 18 billion in pollution-control upgrades. The report also notes that increased mercury emissions in the U.S. could adversely affect Canada due to transboundary transport.

• The U.S. EPA proposes to exclude 'co-benefits'—reductions in pollutants not directly regulated by the MATS, such as particulate matter (PM2.5)—from the cost-benefit analysis used to determine if the regulation is 'appropriate and necessary' under the Clean Air Act.
• Co-benefits are the primary driver of the MATS's economic justification, representing more than 90 per cent of the total monetized benefits.
• The original MATS regulation provided substantial public health improvements, including the prevention of 11,000 premature deaths, 4,700 heart attacks, and 130,000 asthma attacks annually.
• While the proposed change does not immediately remove coal- and oil-fired electric generating units from the Clean Air Act's list of affected sources, it provides a potential pathway for the EPA to rescind the MATS in the future.
• Electric utilities have already invested more than USD 18 billion in pollution-control upgrades to comply with MATS and are seeking regulatory stability to recover these costs.
• Mercury emissions from U.S. power plants have a transboundary impact on Canada, with 17 per cent of mercury deposited in Canada originating from the United States.
• Between 2006 and 2016, mercury air emissions in the U.S. declined by 86 per cent, or 36 tonnes, though this was partially offset by increased mercury disposal on land.

APA

Puzyreva, M. (2019). How and Why the U.S. EPA Is Changing its Policy on Mercury. International Institute for Sustainable Development. https://www.iisd.org/system/files/publications/us-epa-mercury-policy.pdf

Chicago

Puzyreva, Marina. How and Why the U.S. EPA Is Changing its Policy on Mercury. International Institute for Sustainable Development, 2019. https://www.iisd.org/system/files/publications/us-epa-mercury-policy.pdf.

Wikipedia

{{cite report |last1=Puzyreva |first1=Marina |title=How and Why the U.S. EPA Is Changing its Policy on Mercury |publisher=International Institute for Sustainable Development |date=April 2019 |url=https://www.iisd.org/system/files/publications/us-epa-mercury-policy.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{puzyreva2019how, author = {Puzyreva, Marina}, title = {{How and Why the U.S. EPA Is Changing its Policy on Mercury}}, institution = {International Institute for Sustainable Development}, year = {2019}, month = apr, url = {https://www.iisd.org/system/files/publications/us-epa-mercury-policy.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }