SEATTLE — Some bad news for backcountry in the West: Some of the fish in the region's wild alpine lakes contain unsafe levels of mercury, according to a new study by the U.S. Geological Survey.
In the broadest study of its kind to date, the USGS tested various kinds of trout and other fish at 86 sites in national parks in 10 western states from 2008 to 2012. The average concentration of mercury in sport fish from two sites in Alaskan parks exceeded federal health standards, as did individual fish caught in California, Colorado, Washington and Wyoming.
But perhaps more importantly, mercury was detected in all of the fish sampled, even from the more pristine areas of the parks.
The study, conducted jointly by the National Park Service and the USGS, found that mercury levels varied greatly from park to park and even among sites within each park. Overall, 96 percent of the sport fish sampled were within safe levels of mercury for human consumption.
"It’s good news that across this entire study area most of the fish were low," said Collin Eagles-Smith, a research ecologist with USGS and the lead author of the study. "The concern is that there were some areas, and some fish, that did have concentrations that might pose a threat to either wildlife or humans."
The researchers were surprised to find some of the highest levels of mercury in a small fish called the speckled dace, which were sampled in Capitol Reef and Zion national parks in Utah.
There was some bad news in the study for birds: In more than half the sites tested, fish had mercury levels that exceeded the most sensitive health benchmark for fish-eating birds, Eagles-Smith said.
"People can regulate their intake of fish and wild fish-eating birds can’t. So, they’re going to take in more fish and more mercury as a result, and it can impact their behavior, ability to reproduce and ability to find food."
The Centers for Disease Control and Prevention warns that exposure to high levels of mercury in humans may cause damage to the brain, kidneys and the developing fetus. Pregnant women and young children are particularly sensitive to the effects of mercury.
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