CLAUDIA REED, TWN, SEPTEMBER 9, 2006
Those planning a fishing trip to Lake Mendocino or Lake Sonoma might want to consider calling it off.
In both lakes, mercury contamination in fish species at the top of the food chain now exceeds recommended safety levels, particularly for young people, nursing mothers, and pregnant women, according to the California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment (OEHHA).
Consumption of mercury, particularly of the exceedingly toxic methylmercury form found in fish, can cause neurological damage. It’s particularly dangerous to a developing fetus and to growing children. Among the Innuit of Alaska, for example, mercury contamination in whales, a part of the traditional diet, has recently been associated with mild mental retardation in children.
Closer to home, OEHHA has issued a draft health advisory urging the public to severely limit consumption of fish caught in Lake Mendocino and Lake Sonoma. Since fish also offer nutritional benefits, such as low-calorie protein and Omega-3 oil, associated with reduced risk of heart disease, the agency declined to issue a total ban.
The advisory recommends women who are pregnant, breastfeeding, or of childbearing age; and children age 17 or younger, eat no more than:
* One meal a week of sunfish or crappie, and
* One meal a month of largemouth or smallmouth bass.
For men and women past childbearing age, the recommendation is no more than:
* Two meals a week of sunfish or crappie: and
* One meal a week for largemouth or smallmouth bass.
The advisory also recommends consumption of smaller fish (of legal size), rather than older and larger ones which have collected more mercury in their bodies. Food preparation techniques that remove the fat and organs, where mercury concentrates, can help. So can cooking by baking, grilling, or steaming, techniques that allow the juices (which contain fat) to drain away. Roe (fish eggs) should not be eaten.
The OEHHA website also offers advisories on other California lakes and rivers, and points out not all have been tested. Even fish from restaurants and stores can be contaminated.
The U.S. Food and Drug Administration (FDA) advises women who are pregnant or could become pregnant, nursing mothers, and young children not to eat shark, swordfish, king mackerel, or tilefish at all.
It’s reportedly okay for these people to eat up to one meal a week of the fish lowest in contamination, which include shrimp, canned light tuna (half that if it’s albacore), salmon (wild, not fish farmed), pollock, and farmed catfish.
Men and women beyond child-bearing age can safely eat up to two meals a week of the fish lowest in contamination. In general, the FDA says, ocean or river-run salmon is the safest fish and all others should be eaten with extreme caution.
Putting it all together, it would appear that no one should be eating fish more than twice a week, regardless of source.
The OEHHA site explains the mechanism of contamination:
Mercury released from mining and fossil fuels circulates in the environment and settles in water. In water, it’s transformed by bacteria and fungi into the highly toxic methylmercury form. Methylmercury, in turn, “biomagnifies” in the aquatic food chain reaching highest levels in fish at top. In other words, predator fish like shark absorb the mercury accumulated in the organs and fat of the smaller fish it consumes. The older and larger the predator, the more mercury it contains.
For people of all ages and conditions, direct contact with the water, even in lakes with mercury-contaminated fish, is generally considered safe.
So far, mercury contamination in fish in the United States has not reached the lethal levels experienced through industrial contamination in places like Minamata Japan in the 1950s and 1960s. There, those exposed in the womb often emerged as children with cerebral palsy or severe mental retardation. Many exposed adults suffered from loss of sensation in the hands and feet, loss of coordination in walking, slurred speech, and negative mental effects. Several hundred people died.
Similar devastation was caused in Iraq in the 1970s after seed grain was treated with methylmercury fungicide.