It’s always been a mystery to me why the fishing industry equates “some fish have mercury, so avoid high-mercury fish” with “don’t eat any fish at all, ever ever ever!!!” Yet it does, arguing that those irresponsible scientists who issue warnings about mercury in fish will make people miss out on the heart and (for fetuses) cognitive benefits of fish.

Rather than join with scientists and government agencies to maximize the benefits of eating fish and minimize the risks by guiding us to low-mercury seafood, the industry has taken the low road: Deny the existence of any risk at all, attack and discredit those who disagree, try to intimidate the press by challenging every report that mentions risk.

A particularly extreme example has been the continuing coverage of actor Jeremy Piven, who in December got sick (exhaustion, memory, loss balance problems) from the high levels of mercury he developed, apparently as a result of eating a lot of tuna sushi, and withdrew from the Broadway play Speed the Plow. His physician said Piven’s blood mercury level was 60 parts per billion (ppb), which is more than 10 times the EPA “reference level,” and his symptoms were similar to those in other people who eat a lot of the wrong kind of fish. His symptoms and his blood mercury level fit the diagnosis. Yet the press was full of credulous interviews with industry-friendly doctor who insisted, “It’s almost impossible to get mercury poisoning from eating fish.”

In fact it’s not hard at all. A 6-ounce swordfish steak contains about 130 µg of mercury, or 16 days’ worth of the Environmental Protection Agency’s reference dose for an adult man. A 5.5-ounce can of albacore tuna contains 55 µg, a full week’s dose for an adult man. Even canned light tuna, touted as a “low-mercury” fish by the industry (and the FDA, after intense industry lobbying), has 18 µg of mercury in a 5.5 ounce can. For someone like Piven, who eats fish twice a day, those µg’s can add up fast, and it’s easy to get a mercury dose far above the reference dose.

As a public service, let me then make the obvious point. If you eat a lot of fish—which in America, means more than twice a week—you should know what fish to choose to minimize your mercury exposure. The more fish you eat, the more often you should choose from the low-mercury list. Here’s a list of fish and seafood, sorted by mercury content, based on data from the U.S. Food and Drug Administration:

Low-Mercury: Contain less than 0.05 part per million (ppm) mercury. Can safely be eaten daily, or more often, without risk of exceeding reference dose: salmon, tilapia, ocean perch, whiting, pollock, hake, flounder, sole, , haddock, sardines, herring, anchovies, catfish, Atlantic mackerel, shrimp, clams, oysters, crayfish, scallops.

Medium-Mercury: Contain between 0.05 and 0.20 ppm mercury. Can be eaten once or twice a week as long as other choices are from the low-mercury group. American shad, cod, whitefish, Atlantic croaker, freshwater trout, Pacific mackerel, canned “light” tuna, skate, freshwater perch, monkfish, mahi-mahi, snapper, blue crab, king crab, snow crab, squid, spiny lobster.

Higher-Mercury: Contain between 0.21 and 0.50 ppm mercury. Should be eaten only in limited amounts (less than once a week) if you eat fish often: Canned albacore tuna, tuna steak, sea bass, Chilean sea bass, halibut, sablefish, sea trout, Pacific croaker, bluefish, Spanish mackerel, grouper, marlin, orange roughy, American lobster.

Very High Mercury: Contain more than 0.50 ppm mercury. Should be avoided by people who eat a lot of fish and by women of childbearing age: swordfish, shark, tilefish, king mackerel.

Devoted as I am to my job, I think I would draw the line at eating one can of albacore tuna day for 20 days, as reporter Sue Kwon of San Francisco’s KPIX did for a report broadcast last week. The idea was to see how high her blood levels of mercury rose, and rise they did: from 4 parts per billion (already well above the U.S. average of 1 ppb, suggesting that Kwon ate a lot of mercury-laden fish even before her experiment) to 8.9 ppb by day 10, and to 17.2 ppb on day 20. That's when, on her doctor’s advice, she stopped her experiment. Eating a can of tuna a day quadrupled her blood mercury level in just three weeks, which raises obvious questions about what happens to people who eat high-mercury fish for years.

But that's not the point of this post, for having her blood levels of a known neurotoxin rise wasn’t the only hit Kwon took. She also heard from the National Fisheries Institute, the industry trade association, which works very hard to keep you from realizing that it’s easy to get too much mercury, if you eat the wrong kind of fish, and that the resulting levels of mercury pose health risks.

The industry did not take kindly to Kwon’s reporting. NFI flack Gavin Gibbons fired off a letter (posted on the media blog part of NFI’s Website) to KPIX, attacking her. You can also get the gist of Gibbons’ letter in a YouTube video they posted.

It’s always interesting to see how a true artist works, and NFI is second-to-none in distorting science to suit its ends. The letter is a clone of attacks the industry has launched at other journalists who’ve dared to report about mercury risks. Just a few highlights:

• Gibbons, arguing that Kwon’s 17 ppb is nothing to worry about, refers to “the recognized EPA Reference Dose (RfD) of 58 micrograms per liter.” That’s false; the reference level, not dose, is 5.8 µg/l (1 µg/l = 1 ppb). It's the level judged to be free of appreciable risk for almost everyone.
• He raises the bar for falsifying facts by asserting (again to make Kwon’s 17 ppb seem insignificant), “The Environmental Protection Agency has deemed 580 micrograms per liter as the level of mercury that approaches risk.” How did they get from 5.8 to 580? Watch carefully. EPA got the 5.8 by starting with a blood mercury level that had adverse effect on brain development in a key human study—a level of 58 ppb. EPA then divided that by an uncertainty factor of 10, to get the reference level of 5.8 ppb.
• The industry likes to say the reference level has a 10-fold “safety factor” built in. No. EPA applied its 10-fold “uncertainty factor” to account for individual variability. Translation: People differ in their sensitivity to the toxic effects of mercury and everything else. If the average blood mercury level at which an effect is observed in a large group of people is 58 ppb, some people were affected only at higher levels, some at lower levels, and a few at much lower levels. The “uncertainty” is how wide the variability is; there are too few data to establish that. By using a factor of 10, EPA hopes its reference level protects even sensitive individuals. No one can prove that it does, or doesn’t; it’s an educated guess, and some experts have argued for applying a larger uncertainty factor. But in no way is it a "safety factor" with the implication that 58 is just fine.
• The fishing industry has long distorted this scientific process. They falsely call the uncertainty factor a “safety margin.” They claim that the actual “safe” level is 58 ppb, a clear falsehood, as I said. The industry assumes that most of us are too dumb or too busy to catch their misrepresentations. But having fooled us once, they now aim to fool us even more egregiously. If 58 ppb is the safe level, and there is a 10-fold “safety cushion” built in, the actual level where harm occurs must be 580 ppb!

A blood mercury level of 580 ppb would probably kill many people. Toxicity symptoms, like those actor Jeremy Piven suffered (according to his physician, who was interviewed on Good Morning America), have been seen at around 50 ppb. The claim that one merely “approaches risk” with a blood mercury level of 580 ppb is blatantly false and recklessly irresponsible.

Give the industry credit for using New Media to get their message out. Go to YouTube and search for “mercury in fish.” Five of the first six videos are NFI postings, rebuttals to media reports they don’t like. Sue Kwon’s report on KPIX is there, with industry responses that repeat the claim that 580 ppb is a safe level of mercury in blood and generally maul the truth.

Of course eating fish has health benefits, and no one should stop eating fish to avoid eating mercury. But people who eat a lot of fish should choose low-mercury fish (see my rundown of the good kinds, here). That’s just common sense. Why does the message, “Eat lots of low-mercury fish,” terrify the fishing industry? If public health officials concerned about mercury in fish think the battle is about science, they're sadly mistaken. NFI knows the battle is about propaganda, and they are kicking science’s butt.