New findings from a study of contaminants in fish caught off the California coast detected high levels of the toxin methylmercury in more than a third of the locations that researchers sampled. The report, released by the State Water Resources Control Board, is the first comprehensive statewide study testing mercury and providing warnings for anglers and consumers on which large species of fish accumulate the substance.
Seven species popular with recreational fishermen had high concentrations of methylmercury: leopard sharks, brown smoothhound sharks, spiny dogfish, copper rockfish, rosy rockfish, china rockfish and striped bass.
Methylmercury is converted from mercury pollution into the toxic organic from by bacteria in lakes, rivers and the ocean. Sources include gold mines but also fall out from coal-burning power plants from hundreds or even thousands of miles away.
Since there are not significant sources of mercury pollution in the north, the findings indicate that distant airborne sources affect local fish.
The report indicates that older, predatory fish like sharks have higher levels of methylmercury independent of where they’re caught.
The study comes on top of a study by the health and environmental advocacy group Got Mercury testing commonly consumed California caught and commercially purchased fish in the Bay Area.
“Species like shark, swordfish and tuna all concentrate mercury biologically,”said study author David McGuire of Got Mercury. “We know local sharks are high in mercury. But many species of local fish, including California caught fish in the markets and restaurants have levels of concern. Our swordfish tested several times over the limit set by the EPA as safe. Consumers, especially pregnant or nursing women and children should avoid eating high mercury fish.”
Mercury is a potent neurotoxin and can cause developmental disorders in fetuses and newborns who consume breast milk. It has been associated with lower IQ and a number of other symptoms ranging from chronic fatigue to nerve damage in adults. Fish is the largest source of mercury exposure in Californians. The state Office of Environmental Health Hazard Assessment recommends stronger limitations on eating certain species of fish for children and women of childbearing age. Got Mercury has been pressing for increased public education and more protective standards for mercury in seafood.
According to the Got Mercury Fish calculator, a woman who weighs 140 pounds and eats a six-ounce portion of fresh tuna this week will be exposed to a mercury level that is 144 percent above government exposure guidelines. GotMercury.org has been seeking legislative action with the FDA to increase health advisories and lower the action level for commercially caught fish to meet that of the EPA.