Point Reyes Light - May 13, 2004
Pt. Reyes confab set on mercury in bay
By Ivan Gale
State Environmental Protection Agency staff will hold a public workshop at 6:30 p.m. Monday, May 17, in the Dance Palace to discuss the dangers in eating Tomales Bay fish containing mercury. The meeting is being put on by the Office of Environmental Health Hazard Assessment, a division of the state EPA.
"Mercury levels in the fish at Tomales Bay are a reflection of the rich mineral ores in California’s Coast Range and the mining activity that has taken place over the years," said agency director Dr. Joan Denton. "The public should still enjoy fishing at Tomales Bay, but we recommend that people – especially women of childbearing age and children – carefully monitor how much fish they eat."
The agency’s proposed guidelines and list of potential health threats from eating fish and shellfish from Tomales Bay is a follow-up on the county’s Health and Human Services Department in December 2000.
Mercury in big fish
Mercury builds up in the fatty tissue of fish in a process called bio-accumulation. Bacteria first take up the naturally occurring mercury in the sediment and convert mercury into the more toxic form methymercury. The bacteria in turn is eaten by bigger organisms and then small fish.
As the mercury is passed up the food chain, it can accumulate in fish in concentrations many thousands of times greater than mercury levels in the surrounding water. Even thoroughly cooking fish does not eliminate the mercury.
Such is the case with the Soulajule Reservoir along the Marshall-Petaluma Road. Recent testing revealed mercury in largemouth bass exceeded the recommended consumption levels, while testing shows the water contains no mercury and is safe for drinking.
Much of the Bay’s mercury is thought be from the old Gambonini mine, just downstream of Soulajule Reservoir. Mercury was mined there from 1968 to 1972. Although the mine was capped and met EPA standards, the flood of 1982 exposed the mine’s tailing pipe and mercury leaked into Walker Creek, which feeds into Tomales Bay. It wasn’t until 1998 that the Marin Resource Conservation District completed a second and more thorough project to cap the mine.
EPA recommendations
The state EPA’s draft advisory recommends that women of childbearing age and children age 17 and younger avoid eating all sharks, while limiting consumption to one meal a month of bay rays; or one meal per weak of California halibut, redtail surfperch, pile surfperch, shiner surfperch or red rock crab; or three meals per week of jacksmelt.
For women beyond childbearing years and adult men, the advisory lists the same fish, but generally allows for eating them three times as often.
Eating commercially grown oysters, clams, and mussels is considered safe, as no mercury has been found in these shellfish.
A draft copy is available for viewing and downloading at <www.oehha.ca.gov>. The deadline to send in written comments is June 9.