January 2017

This week, the ATS filed an amicus curiae – or friend of the court – with the DC District Court of Appeals urging the court to affirm the EPA's rule, known as the Mercury and Air Toxics rule (MATS) to reduce mercury and other air toxic emissions from power plants.

This case has a long history with the courts. The legal issue before the court centers on addressing costs in developing air toxic regulations. The courts first addressed the question of cost in 2013 when the DC District Court ruled that the EPA does not have to consider costs when issuing the MATS rule, only to be overruled by the US Supreme Court. In response to the Supreme Court decision, the EPA revised the rule to address costs and reissued a final MATS rule.

Now that the courts have determined that the EPA must address costs, the legal question is how the EPA should consider costs. Mercury, acid gases and heavy metals are explicitly regulated under the MATS rule. However, reducing these pollutants also has the co-benefit effect of reducing other pollutants – namely particulate matter – that are not covered under the MAT rule but are instead regulated under separate authority of the Clean Air Act. The majority of health benefits under the MATS rule are achieved by reductions in particulate matter.

In doing the cost benefit analysis of the revised MATS rule, the EPA included the benefits of all the pollutants reduced by the MATS rule, including particulate matter. Industry is challenging the EPA's calculation saying that because particulate matter is not explicitly regulated under the MATS rule, the benefits of particulate matter cannot be used to justify the MATS rule.

The purpose of the ATS amicus curiae is to share with the court information about the significant health benefits that would be achieved by the pollution reductions in the MATS rule.