…Congress passed the…[Clean Air Act] in 1970 and substantially strengthened it in 1990 to safeguard human health from air pollution generated by power plants, vehicles, incinerators and other sources. One of the most toxic of these pollutants is mercury, a heavy metal that accumulates in waterways and the fish Americans eat…In 2012, the [Environmental Protection Agency (EPA)] issued a rule ordering coal-fired power plants, which are far and away the single biggest source of these emissions, to adopt technology to reduce them. The coal industry sued the government…Business owners and other industry backers argue that the law requires the E.P.A. to weigh those costs against any potential health benefits of a regulation…Coal industry backers…view every regulation, whether aimed at protecting human lives or the future of the planet, as nothing more than a “war on coal.” But profits and human health are not mutually exclusive. To the contrary, the technology to meet the E.P.A.’s new mercury standards is already in place at most coal-fired power plants nationwide...The Supreme Court has upheld the E.P.A.’s authority to carry out that law’s purpose with broad discretion. There is no reason to upset that deliberate balance, or unreasonably limit the agency’s authority, now.US Supreme