Point Reyes Light - October 7, 2004
State reports mercury levels in different fish
By Jacob Resneck
State environmental officials on Tuesday announced the final health-advisory guidelines for eating fish caught in Tomales Bay.
The safety issue is that certain fish in the bay have elevated levels of mercury. The guidelines, published Tuesday by the California Environmental Protection Agency, are unchanged from the draft recommendations discussed in May during a public workshop.
During that workshop, however, there was agreement that mercury levels in Tomales Bay fish may be no different from those elsewhere along the coast.
While the California EPA continues to cite tailings from a mercury mine as "a principal source" of mercury in Tomales Bay, a state environmental official conceded that there is no hard data as to how much mercury found in Tomales Bay can be attributed to the mine on the Marshall-Petaluma Road.
"We don’t really have any way of knowing" how much of the mercury in Tomales Bay is natural and how much is from human activity, Allan Hirsch, spokesman for California EPA’s Environmental Health Hazard Assessment Office, told The Light.
Gambonini mercury mine
"The mine appears to have contributed to the mercury in Tomales Bay, but then again the California coastal [mountain] ranges are [naturally] very rich in mercury."
The Marshall-Petaluma Road ranch from 1968 to 1972 was leased by the Gambonini family to Buttes Gas & Oil which mined a significant amount of mercury there. The mine on the Gambonini Ranch was only one of four neighboring ranches where mercury was mined.
When Buttes Gas and Oil closed the mine in 1972, they sealed the mine well enough to receive praise from the Marin Conservation League. When the Storm of 1982, which devastated West Marin and other parts of the Bay Area, struck, it was powerful enough to wash away the seal. Hundreds of pounds of mine tailings are believed to have been washed into Walker Creek, which drains into Tomales Bay.
Despite government efforts to contain it, mercury continued to seep into the creek until it received a $3 million seal in 1998, with the San Francisco Bay Regional Water Quality Control Board and the Point Reyes Station-based Resource Conservation District overseeing the work.
Some people dubious
Some West Marin residents at the May workshop in the Dance Palace were dubious that mercury levels in Tomales Bay are different from mercury levels elsewhere in California.
Among the fish that the state says should be eaten on a limited basis to avoid consuming too much mercury is halibut. Stick to one serving of halibut per week, says the Health Hazard Assessment Office. Tom Baty of Marshall during the workshop responded, "We’re given the Gambonini mine storyline, but halibut everywhere have the same [mercury] levels." Baty argued that a discussion of historic mining in West Marin "has virtually no bearing on [current] health concerns."
Surprisingly, a toxicologist from the state EPA agreed with him. "Has the Gambonini mine truly added much more mercury here than exists in San Francisco Bay fish or [in fish on] other parts of the coast?" he asked rhetorically. Then answering his own question, the EPA toxicologist said, "It really may not be that much more."
Mercury in Soulajule
Nor is Tomales Bay the only West Marin body of water where some fish have noticeable amounts of mercury. In March, the Regional Water Quality Control Board found that largemouth bass in Marin Municipal Water District’s Soulajule Reservoir – upstream from the Gambonini mine – also have elevated levels of mercury.
On the other hand, the mercury levels in crappie and channel catfish were not unduly high. Nor was mercury showing up in the drinking water.
How mercury gets into fish
As explained by Bob Castle, a water-quality specialist with Marin Municipal, here’s what typically happens. Naturally occurring mercury in sediment is taken up by tiny plants and animals like plankton. The plankton etc. is food for small aquatic creatures, which are eaten by larger aquatic creatures.
The most-active predators accumulate more of the mercury, and fish on top of the food chain can contain 100,000 times the level of mercury as the smallest aquatic creatures, Castle said.
Whatever the source of mercury in fish around here, the state recommends that children under 18 and women of childbearing age should beware that:
• Sharks are unsafe for consumption. As predators on the top of the food chain, all species of shark contain elevated levels of mercury and are not considered safe.
• Bat rays should be eaten no more than once a month whereas halibut, redtail, pile, perch, and crab should be eaten no more than once a week.
• Jacksmelt fish should be eaten no more than three times a week.
The advisory for men as well as women "beyond childbearing age" is:
• Brown smoothhound sharks and leopard sharks should not be eaten more than once a month.
• Bat rays and angel sharks should not be eaten more than once a week.
• Halibut, redtail, pike, surf perch, and crab should be eaten no more than three times a week.
• Oysters and other Tomales Bay aquaculture are considered safe for children and adults alike.
The findings and complete advisory for Tomales Bay is available from the Office of Environmental Health Hazard at <www.oehha.ca.gov>.