Mercury Rising?
Fish eaters are singing the toxic-chemical blues.


My wife sent me to the supermarket the other day to get some fish for dinner. Approaching the seafood counter, I noticed a gray sign on the Plexiglas. Instead of announcing a sale, it was a cautionary warning from the FDA, advising pregnant and nursing mothers and young children not to eat any swordfish, kingfish, tilefish, and shark because of high methylmercury levels.

The label is in response to a suit filed on January 17 by California attorney general Bill Lockyear. The suit names several grocery stores who, Lockyear says, have failed to post consumer warnings about excessive methlymercury in some of the fish they sell. Until such warnings are posted, Lockyear wants them to stop selling the fish.

As if the threat of bioterrorism wasn’t bad enough, the media and some ecogroups scream of a new toxic disaster every day, be it pesticides, smog, hydrocarbons, MTBE, PCB, DDT, EDB, mercury, acid rain, or selenium.

My toxic-disaster yoda is Dr. Richard Wade, a friend for three decades who has served as the head of public-health agencies in Minnesota and California. He is now a member of the National Academy of Sciences and the Naval Studies Board, and is working on chemical and biological terrorism defense strategies. He is also an environmental-health consultant. I caught up with Dick on a break from his latest mission — to stop the pandemic of Norwalk virus on cruise lines. I said that I had heard less about Norwalk in recent days, so we must be winning. Dick chuckled. He said that thankfully the virus seems short-lived, and might be taking itself out of commission.

Dick understands the present mercury advisory only too well. When he was the director of environmental health for Minnesota, he announced a similar warning about eating perch and pike, based on elevated levels of mercury in samples of fish. All hell broke out. Fish are big business in Minnesota.

Wade explained that while mercury can arise from industrial sources, it is a naturally occurring substance, usually present in very small amounts. When ingested in such small amounts, our body can rid itself of mercury. What seems to have happened in pristine northern Minnesota was that acid rain changed the pH of the water, thus reducing the natural processes for breaking down metallic mercury. Little critters fed on the mercury-enriched sediments, transforming metallic mercury into methylmercury. The big fish ate the little guys, accumulating most of the mercury in their flesh. People found themselves at the top of a mercury-tainted food chain. It was not an enormous amount of mercury, but it did exceed public-health standards for young kids and the unborn, those who are more susceptible to damage from toxic exposures.

Wade said that mercury, most likely, has always been present in large oceanic predator fish. The warnings come about because “in the last twenty years we have made quantum jumps in detection,” both in the environment, and in humans. Poisoning can be both acute and dramatic, or slow, gradual, and accumulative, and modern technology makes us better able to study chronic poisonings. I understand that one. Growing up on an island in Lake Erie, I ate a lot of fish, which we later learned were laced with mercury. Baldness is a symptom of chronic mercury poisoning, and I have scant few hairs on my head. Is my being follicularly challenged an inheritance, or is it due to eating too many Lake Erie perch?

Dilemmas like this can drive you nuts. Most of us skip the mercury warnings and turn to the sports section of the newspaper. Some, however, become obsessed with the fear of poisons. There has to be some middle ground. So, how do we survive in a world seemingly laced with toxics?

Wade suggests that people develop their own filtering systems. Here are some ways to better evaluate toxic warnings:

1) Each person’s tolerance for toxics is different. Some people are more susceptible than others, especially young children.

2) “Poison is a function of dose.” Acute poisonings like the gas release in Bhopal are rarer these days, but with more sophisticated monitoring, we become more aware of chronic poisoning.

3) Always question the source of a warning. Some media thrive on the disaster of the day. A number of environmental groups are dependent on crises for funding, so they may be crying “Pollution!” when they really mean “Save my salary!”

4) Some quantities of some substances — parts per million or even parts per billion — can cause delayed reactions, especially if the toxics do not rapidly biodegrade. Remember that DDT did not kill predator birds, but caused thinning of their eggshells, which meant that incubating birds crushed the shells of their young.

I asked Wade if he ate fish. “Not large pelagic ones like shark or swordfish,” he said. “Small ones, like rock cod and salmon, sure. In moderation.”

Sportsmen should be more aware of toxic chemicals than most. Fish and game regulations usually include several pages of public-health warnings. California duck hunters are warned about elevated selenium in ducks in Merced County and diving ducks in San Francisco Bay. Michigan’s Department of Natural Resources has produced a special fish-consumption advisory. It urges people to “choose fish that don’t eat other fish,” like small panfish and trout, and avoid eating walleyes, northern pike, muskellunge, bass, and lake trout, which “tend to have more chemicals.” If you really want to worry, the EPA has a list of fish advisories for the nation.

Wade quoted the late humanitarian microbiologist Rene DuBos: “Health is the ability to adapt to a changing environment.” Make your choices about what you eat wisely and get on with it. The fear of what you may eat might be worse than what you do eat.

— James Swan is a contributing editor of