Mercury levels down 20% in Great Lakes but still too high

Mercury levels have dropped about 20 percent in the Great Lakes in recent decades but remain dangerously high and are getting worse in some places, scientists said in a report released Tuesday.

Concentrations of mercury exceed the risk threshold for people and wildlife at many spots across the region and are particularly high in inland waterways, said the report issued by the Great Lakes Commission, an agency that represents the eight states and two Canadian provinces surrounding the lakes. It said scientists had found that mercury is toxic to fish and wildlife at surprisingly low levels.

The report was issued the day after 25 states asked a federal court to block limits on mercury and other air pollution from power plants that the Environmental Protection Agency plans to set next month. Michigan Attorney General Bill Schuette, who led the effort, said the regulations would hurt the economy and cause electric rates to jump. The Republican-controlled U.S. House last week voted to delay rules to cut emissions from cement plants, solid waste incinerators and industrial boilers.

Authors of the Great Lakes report said lower emissions from incinerators were largely responsible for the mercury drop-off.

“Logic would suggest if we controlled them further, we would be even more successful,” said Charles Driscoll, a Syracuse University environmental engineer.

The report was based on what Tim Eder, the commission’s executive director, said was the most thorough evaluation of mercury pollution trends ever conducted in the region. It involved 170 researchers who produced 35 peer-reviewed papers after taking more than 300,000 measurements, including samples from birds, fish and sediment.

The decline in mercury contamination since its peak in the 1980s is “very welcome news,” said study co-author James Weiner of the University of Wisconsin at La Crosse.

But reasons for concern remain, he said. Six commonly eaten game fish had average mercury concentrations above the Environmental Protection Agency’s designated safe level in more than 60 percent of the area studied. An uptick in concentrations of some fish and wildlife such as loons in Wisconsin, eagles in Minnesota and walleye in Ontario lakes is worrisome — largely because scientists don’t know why it’s happening, Weiner said.

“The more we look, the more samples that are taken, the more evidence of mercury we find,” Eder said.