The US Geological Survey yesterday issued a report on mercury contamination in fish and stream beds across the US. The news is not good — at more than one quarter of the sampled sites, mercury levels in fish exceeded EPA’s acceptable standard, which means that it is unhealthy to eat an average amount of those fish. As Catherine O’Neill points out at CPRBlog, that standard itself
grossly understates the risk to those people whose fish consumption practices differ from those of the “average American,” particularly members of the various fishing tribes, Asian-Americans, and those hailing from the Pacific or Caribbean Islands. Whereas EPA’s criterion is based on the assumption that people eat 17.5 grams per day of fish – about one fish meal every two weeks, on average – people in these groups consume fish at several times this rate.
The USGS report finds that mercury contamination is geographically widespread — every fish sampled had detectable mercury — but worst in fish from eastern and southeastern coastal plain streams, and from western basins with a legacy of gold and mercury mining, including northern California. (As USGS points out, their study design targeted areas thought to be at risk for mercury contamination, so their results cannot necessarily be extrapolated to areas they did not survey.)
USGS has a web page devoted to mercury in streams here.