Officials issue warning about mercury in fish

TRUCKEE - Recent analysis by the California health department concludes various species of fish in Donner Lake are not safe for humans to eat regularly due to increased levels of mercury and other compounds.

Sam Delson, deputy director at the Office of Environmental Health Hazard Assessment, said the warning was released after tests for mercury and polychlorinated biphenyls (PCBs) were conducted on edible fish species in the Truckee lake.

While the advisory is cause for an adjustment in diet, Delson said residents shouldn't be alarmed.

"It's OK to eat any of them as long as you limit your consumption," Delson said.

The report said kokanee shouldn't be eaten more than twice weekly, and rainbow trout should be eaten in limited quantities by children younger than 18 and women of childbearing age. Anglers, the report added, shouldn't eat more than one serving of Donner Lake brown trout per week.

"Our main message that may be getting lost is that actually Donner Lake is pretty clean compared to other lakes in the area," he said.

Exposure to high amounts of mercury can affect the nervous system in children and harm learning ability, language skills and memory, the report said.

According to the report, the harmful chemicals are both manmade and natural.

Mercury is a trace metal that occurs naturally in the environment and can be redistributed by activities such as mining and the burning of fossil fuels. In aquatic systems such as Donner Lake, it undergoes chemical transformation to its more toxic organic form, methylmercury, which accumulates in fish and other organisms.

Side effects of methylmercury are especially toxic to developing fetuses and young children and could damage the nervous system.

PCBs are man-made chemicals used mainly in electrical equipment and plastics. The chemicals were banned in the 1970s; they still remain because they do not break down easily and can accumulate in fish tissues. PCBs can cause cancer or other health effects in humans.

The report said that the risk linked with eating fish containing PCBs depends on the toxicity of the chemicals and the exposure level.