Levels of highly toxic mercury contamination in Atlantic bluefin tuna are rapidly declining, a trend that has been linked to reduced mercury emissions in North America, according to a new study published in Environmental Science & Technology. Average mercury concentrations dropped by more than 2 percent per year, for a total decline of 19 percent between 2004 and 2012.

Scientists believe that most of that reduction has occurred because of a shift away from coal, the major source of mercury emissions, to natural gas and renewable fuels. Pollution control requirements imposed by the federal government have also cut mercury emissions, but these have been rolled back or eliminated by President Trump’s commitment to “bring back coal.”