The study, conducted by the National Center for Atmospheric Research, found fires in Alaska, California, Oregon, Louisiana and Florida emit particularly large quantities, with fires in the southeastern states emitting more mercury than any other region.

Mercury released by forest fires originally comes from industrial and natural sources.

Scientists estimate fires in the continental United States and Alaska release about 44 metric tons of mercury into the atmosphere every year.

The study is the first to estimate mercury emissions for each state, based on a new computer model developed at NCAR.

The authors caution that their estimates for the nation and for each state are preliminary and are subject to a 50 percent or greater margin of error.

The research appears online in the journal Environmental Science and Technology.