Rationalizing that I was just .08 over the limit, so it wasn't really that big a deal, I called Maas, of the Environmental Quality Institute, which did the testing. But he told me: "If you have a level above 1, it's definitely a cause for concern."

He explained that it's statistically probable that my contamination came from fish, although there are other possible, if less likely, sources, such as the silver amalgam filling I have in one tooth, or the traces of mercury used as a preservative in some medical shots, such as flu shots. But the most probable source is fish, and therefore the easiest way to try to lower my level is to change the fish I eat.

Here's how the toxin gets into fish: When coal burns, it releases mercury that gets turned into gas, Maas says. As it cools, the mercury turns into aerosol droplets, which can travel hundreds of miles before settling onto the ground or water. In water, it settles into the sediment at the bottom of rivers and lakes.

"The bacteria in the sediment methylate this mercury and turn it into methyl mercury to make it less toxic to themselves," Maas says. "That's a problem, because methyl mercury is fat soluble." That makes it harder for creatures that consume it to excrete it, according to Maas, since the mercury gets stored in lipid and muscle tissue.

What happens next is the process that makes methyl mercury more concentrated in a shark than, say, a worm. "When burrowing worms or insect larvae consume sediments, they get that methyl mercury in them, and then it gets biomagnified up the food chain. Then, maybe a crawfish eats that insect larva, and a small fish eats that crawfish, and a larger fish eats the small fish," Maas says. "Each time all the methyl mercury is passed up the food chain. Each trophic level will then have a methyl mercury level 10 times higher than the one below it. That's why by the time you get to the sports fish and large fish that we actually consume, those levels are quite high."

The state of California requires grocery stores to post warnings about mercury contamination in the fish they sell, although they don't always comply.

But all the estimates, recommendations and warnings are based on averages and approximation. You never know exactly what level is in the sample on the end of your fork. I may not think that I eat a lot of fish, but the fish that I happened to eat during the months represented by the hair sample could have been especially contaminated, leading to my high reading:

"There's a bit of a Russian-roulette element here. You may go to a sushi bar, and get a fairly decent slab of tuna, and you may get a hot mercury-rich piece," says Kert Davies, a spokesperson for Greenpeace.

Mercury pollution from power plants is not regulated at the federal level, although some states like Massachusetts, New Jersey and Wisconsin have imposed their own measures. But federal regulations are now being formed. The National Wildlife Federation and the Public Interest Research Group argue that under the Clean Air Act, 90 percent of the mercury pollution from those plants should be cleaned up by 2008. Under the same law, the government is already successfully implementing cuts on mercury pollution from waste incinerators. Environmentalists say only corporate self-interest is preventing the same thing from happening with power plants

Under the legislation the Bush administration calls Clear Skies, only 70 percent of that mercury would be cleaned up, and it might take as long as until 2025.

"We're expecting them to reintroduce Clear Skies as soon as the new Congress comes in, in January, because of the election results," says Olivia Campbell, national campaign coordinator for the National Wildlife Federation. Sen. James M. Inhofe, R-Okla., known for calling "manmade global warming" "the greatest hoax ever perpetrated on the American people" on the floor of the Senate, plans to reintroduce the bill. With a friendlier Senate, it has a better chance of passing, and the EPA is expected to release its mercury regulations by March. Although mercury does occur naturally from geological formations, like volcanos, some 70 percent of the emissions in the United States, according to the Ocean Conservancy, come from burning coal.

To be fair, the methyl mercury that apparently was speared by my fork or chopsticks can't all be pinned on Bush, given the global nature of the fish supply. We might have to clean up the whole world to make it safe for future mothers to eat swordfish and shark again. But the Bush administration has opposed attempts by European delegates to the United Nations to create a global protocol to control mercury.

So, instead of trying to regulate methyl mercury out of the food supply, we're stuck with trying to avoid the pollution at an individual level. The Environmental Protection Agency offers these guidelines for what women of reproductive age should and shouldn't eat. (They offer no guidelines for men, the traditional logic being that if you protect the hypothetical unborn fetus, which can tolerate only the lowest levels, it's likely that everyone else in a given family is getting safe levels, too.)

The EPA guidelines suggest that if you're concerned about mercury, you leave big predatory fish, like shark, swordfish and tilefish, out of your diet completely. You're also supposed to limit your intake of other fish and shellfish to those that eat lower on the food chain and are therefore lower in mercury, such as salmon and shrimp, to about 12 ounces -- about two average meals -- a week.

Albacore tuna is typically higher in mercury than light canned tuna, so limiting albacore to once a week is also advised. But environmental watchdog groups challenge those guidelines as not aggressive enough, suggesting that they subject women and their fetuses and young children to too much risk, while pandering to the tuna industry. Environmental groups offer their own, more conservative, recommendations.

The gross irony of all this wrangling over which fish has more or less mercury is that government scientists are fearful that consumers, grossed out by mercury pollution, may just shun fish in general. Why are they alarmed? Because, when fish is not subtly poisoning you, it's very good for you.

"If your level is higher than you consider desirable, reduce the amount of mercury you're taking in your diet by changing the types of fish that you're eating," Mahaffey from the EPA told me, diplomatically. "We do think that fish is good for you overall, so we really recommend that people select fish that are lower in mercury." But she admits that it's a hard message for consumers to understand: "It's a complicated risk message because for years we've been telling people that fish are good for you. They're recommended to help in the prevention of coronary heart diseases, and also a lot of weight-reduction diets have recommended these. Yet, as we learn more about the levels of contamination it's pretty clear that we have to be selective in the types of fish you eat."

Some studies even suggest that the well-known heart-health benefits of the omega-3 fatty acids in fish can be canceled out by mercury. "If you're eating fish every day, you're not really getting much benefit from the fatty acids," says the National Wildlife Federation's Murray. "The effects of the contaminants seem to really overtake the benefits that you're getting at those higher levels."

Mahaffey recommends salmon, anchovies and shrimp, which all have "decent amounts" of omega-3 fatty acids and relatively low mercury levels. And she tells consumers to eat less "steaklike" fish. In other words, eating fish that themselves eat lower on the food chain is your best bet.

The good news, from my perspective, is that subjects who cut their fish intake in some studies, like Hightower's, have seen drops in their measurable mercury levels in just a few months. I'll get back to you with my next set of test results. Let's hope I can report I'm out of the toxic zone and still have some hair left by the end of this.

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