Frightening Mercury Levels in Minnesota: Is the Historic Fur Trade to Blame?

Another factor is a bit more natural. The monument's forest happens to consist primarily of needle trees, called conifers. These types of trees are known to "scour" mercury from the air itself, trapping emissions and keeping them in the soil. If mercury levels were elevated even centuries ago, they've really had no place to go since then.

So what does this mean for the area? According to the study, bait fish found in the region had adequately low mercury concentration levels, but the large fish that eat them were found to be approaching dangerous levels. Specifically, 61 percent of the fish from Grand Portage Creek, 97 percent from Poplar Creek, and 84 percent from Snow Creek had mercury levels higher than what is considered safe to eat for kingfisher birds, which are highly sensitive to mercury. And 23 percent of those same fish had levels that could cripple newborn minks.

Humans, too, may be seeing these impacts. The study authors bring up past work that highlights how residents of Minnesota's North Shore area, right by the monument, have seen heightened mercury exposure. A 2013 survey even found that among 1,400 newborn babies in the region, about 10 percent had potentially detrimental levels of mercury in their bodies.

Pat McCann, a research scientist with the state's Department of Health, who led the research, said that it remains unclear if these levels are higher, compared to levels in newborns elsewhere in the state.

However, she did add that "people definitely seem to be eating a lot of fish" in the North Shore area. And while recent research has made the argument that the benefits of eating fish during pregnancy outweigh the risks, it may be best that mothers in risky areas like near the GPNM stick to safer meals or fish-oil supplements.

Produced with material from Environmental Health News (CC0) - B. Bienkowski.

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