FILE - In this July 27, 2018, file photo, the Dave Johnson coal-fired power plant is silhouetted against the morning sun in Glenrock, Wyo. The Trump administration on Friday targeted an Obama-era regulation credited with helping dramatically reduce toxic mercury pollution from coal-fired power plants, saying the benefits to human health and the environment may not be worth the cost of the regulation. The 2011 Obama administration rule, called the Mercury and Air Toxics Standards, led to what electric utilities say was an $18 billion clean-up of mercury and other toxins from the smokestacks of coal-fired power plants. (AP Photo/J. David Ake, File) (Source: J. David Ake)