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Comments to EPA on Reconsideration of Mercury and Air Toxics Standards

The Environmental Protection Agency (EPA) is proposing to withdraw a prior finding that it is “appropriate and necessary” to regulate power-sector emissions of mercury and other “air toxics” under the Clean Air Act. We submitted comments arguing that EPA has failed to provide a reasoned explanation for this change of course.

In 2016, EPA found that it was appropriate and necessary to regulate mercury and other toxic emissions from coal- and oil-fired power plants, even after taking the costs of such regulation into account. In making this finding, the agency relied in part on a regulatory impact analysis showing that health benefits of its Mercury and Air Toxics Standards (“MATS”) would “exceed the costs by 3 to 9 times.” EPA now claims that reliance on this cost-benefit analysis was improper because the analysis included “co-benefits” from particulate matter reductions that would occur as a necessary consequence of the steps plants took to reduce their mercury and air-toxic emissions.

Our comments explain that the Clean Air Act does not require EPA to ignore co-benefits when making an appropriate-and-necessary determination. Furthermore, ignoring such benefits is an unreasonable exercise of agency discretion, because it is inconsistent with relevant case law, longstanding executive guidance, decades of administrative practice, and sound economic principles.

We also critique the unsupported conclusions of EPA’s residual risk and technology review for MATS.