https://arstechnica.com/tech-policy/2018/12/epa-to-keep-obama-era-mercury-rules-but-make-it-harder-to-tighten-them/

According to a report from Bloomberg, the Trump administration's Environmental Protection Agency (EPA) is not considering a roll back of Obama-era rules regulating industrial emissions of mercury. When the rules were codified in 2015, they required coal plants to add expensive technology to minimize the amount of mercury spewed into the air. Despite this change of course for the regulation-averse EPA, the agency is reportedly considering a rewrite of the legal justification for the mercury rules that would make it harder for those rules to be tightened in the future.