A new study says lakes in urban areas absorb as much as four-times as much mercury as lakes in remote areas.
Mercury has long been regarded as a global problem, because it can travel long distances in the air. But the study, by the U.S. Geological Survey, found higher mercury deposition in urban lakes.
Study author Peter VanMetre, a research hydrologist based in Austin, Texas, said the mercury is probably coming from several sources including historically contaminated soils and other types of air pollution that encourages mercury deposition.
"Because of that, there could be more mercury contamination of fish and more concern for aquatic life and human health that's not evenly distributed either," VanMetre said. "There is local signal or effect from our own releases of mercury."
Van Metre said the study suggests fish in urban waters could be more heavily laden with the organic form of mercury that can cause nerve damage.
The Minnesota Department of Health has fish consumption guidelines for many lakes in the state.