Mercury CA’s top fish contaminant, according to new Water Board study

According to a new study from the CA State Water Resources Control Board, mercury is the number one contaminant of fish in the state’s lakes.  The second highest contaminant is PCBs. 

These findings reiterate the need for more actions to address mercury in California’s environment.  Methylmercury, which contaminates fish tissue, is known to cause birth defects, nerve damage, and developmental disorders.  Pregnant women, children under 18, and women who may become pregnant should be careful about how much of certain kinds of fish they are eating. 

The Sierra Fund has been working to increase public awareness of and state funding for legacy mining toxins.  All mercury contamination in Sierra Nevada lakes is a result of gold mining activities. 

Recently, The Sierra Fund CEO Izzy Martin spoke to the Senate Budget Subcommittee 2 on the need for the state to take more steps to pro-actively address mercury in its waters. 

The entire Water Board study is available at:

The Stockton Record’s analysis of the report follows:

Study: Just 15% of Lakes Clean

Stockton Record – 5/6/09
By Alex Breitler

SACRAMENTO – It’s no secret that the Delta is contaminated with mercury, PCBs and pesticides.

A new study sampling fish from a fraction of California’s 9,000 lakes suggests most upstream water bodies are also tainted, from small Central Valley ponds to sprawling Lake Tahoe.

Just 15 percent of the lakes sampled were considered “clean” – that is, the average amount of contamination in fish caught from those lakes was below all human health thresholds, the State Water Resources Control Board reported.

The California Sportfishing Protection Alliance called this a “damning assessment of the state of California’s lakes.”

State officials, however, said more sampling is needed. “There is no reason to stop eating all fish from all lakes in California,” officials said in a written statement.
Jay Davis, senior scientist with the Oakland-based San Francisco Estuary Institute, which is conducting the ongoing study for the state, said the analysis is the largest of its kind to date.

“The take-home message is that contamination is widespread in California sport fish,” he said. “People need to be smart about the fish they do catch and eat, especially mothers and women who could become pregnant.” Mercury has been linked to birth defects.

The biggest culprit is mercury, a poisonous metal that lingers from the Gold Rush era in streams draining from the Sierra Nevada. In the environment, mercury converts to a more toxic form and accumulates in tiny organisms that are eaten by fish.

That contamination spreads up the food chain to humans, attacking the nervous system. Seventy-four percent of the lakes in the study contained fish with mercury concentrations above one threshold for public consumption.

PCBs, chemicals used by electric utilities and industry, are also a problem. Pesticides at high levels were a less frequent occurrence.
Not surprisingly, fish from upper-elevation lakes were less likely to be contaminated, although even some of those water bodies – famously clear Lake Tahoe, Caples Lake off Highway 88 and Hetch Hetchy Reservoir, for example – fell short of standards.

The closest to home for Stockton residents was little Yosemite Lake, at the head of Smith Canal, fed by stormwater from the central area of the city. PCBs were the most significant problem there.

The study targeted popular lakes for fishing and randomly sampled a few others as well. In all, 6,000 fish from 152 lakes and reservoirs were checked; a second wave of tests was conducted, but those results have not been released.

Mother Lode fisherman and author William Heinselman said he believes the risk from eating fish is relatively low. “You should not be scared of the lakes,” he said. “If you’re going to consume 4 pounds of fish a day, yeah, you may damage something. But not if you’re only eating one meal a week.”