Mercury in Seafood: How Do You Know How Much Fish You Can Safely Eat?


Wondering how much fish is safe to eat? I recommend following the government recommendations; not the bogus calculations from The Center for Consumer Freedom. I was first clued into the Center for Consumer Freedom’s fish and mercury calculator by Food & Water Watch’s Blog.

The Center for Consumer Freedom bills itself as an organization promoting personal responsibility and free choice in consumption habits, but it is best known for opposing government smoking bans in public places and was, in fact, started with seed money from Phillip Morris. More recently, the center has fought nutrition labeling requirements on restaurant menus. I’m all for free choice, but to make a fully-informed free choice, consumers need information and transparency.

Users of the calculator have only to enter their weight and usual portion size of different kinds of fish they consume and the calculator spits out the amount of fish the user can safely eat per week, in pounds, before being in danger from mercury poisoning. According to Food & Water Watch, the calculations are bogus. The calculator in question ignores the Environmental Protection Agency’s (EPA) uncertainty factor that accounts for variations in sensitivity to mercury in the population.

This is a real concern. Safety margins are a good thing. You see, I actually know someone who was diagnosed with mercury poisoning from eating fish. In general, she ate a tuna sandwich several days of the week and sushi fairly often. She certainly didn’t eat the pounds and pounds of fish that the How Much Fish Calculator says a person of her size can eat without becoming sick. (Here’s an article from Mother Jones about a woman who became sick from eating canned tuna, which many people think should carry a warning label.)

Maybe these two people were more sensitive to mercury than others and that’s why they became sick, but that’s precisely why the EPA uses the reference dose it does – to take into account sensitive populations. The EPA explains it thus: “In general, the RfD is an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime.”

Far worse, I think, is the Center for Consumer Freedom’s lack of warning for pregnant women. Children are particularly susceptible to nervous system damage while their brains and nervous systems are still developing. According to the EPA in its studies on mercury, “the nervous system is considered to be the most sensitive target organ.” Naturally lower weight individuals (and fetuses) are in greater danger of accumulating dangerous levels of mercury.

According to the EPA, “Investigators have found that the placenta is not a barrier to the transfer of methylmercury from the mother to the developing fetus. Typically, a strong correlation exists between maternal-blood mercury concentrations and fetal-blood mercury concentrations, as shown by cord-blood. Overall, data from these studies indicate that cord-blood mercury is higher than maternal blood mercury.” Not only does the calculator not account for pregnant mothers, but The Center for Consumer Freedom encourages pregnant women to eat lots of fish for smarter children!

With recent news on NPR of a Federal study showing widespread mercury contamination throughout the nation’s streams, it behooves consumers to err on the side of caution when eating fish.

Not sure if you’re getting too much mercury with your Omega-3’s? See the actual government recommendations on fish consumption. Personally, I’d add tuna to that list, both canned and fresh, unless you know that it came from a small, young species of tuna. All large, longer-lived species at the top of the food chain tend to bio-accumulate toxins in their flesh as they age.

Image: rubberslippersinitaly

This is the latest installment in Vanessa Barrington’s weekly column, The Green Plate, on the environmental, social, and political issues related to what and how we eat.

Vanessa Barrington

Vanessa Barrington is a San Francisco based writer and communications consultant specializing in environmental, social, and political issues in the food system.