| ||
Wednesday, Apr. 27, 2005 | ||
Salmon has less mercury than tunaBy RICHARD HARKNESS Q: I read your column discussing mercury in tuna fish. Does salmon also contain mercury? Ive been eating 4 ounces of canned salmon five days a week at lunch, and often an additional 4 ounces of fresh salmon at dinner. A: Mercury, a neurotoxin, is present in fish as methylmercury. According to EPA surveys, mercury levels in canned salmon are too low for detection. Fresh or frozen salmon has an average mercury level of 1.7 mcg per 6-ounce serving, at the low end of detection. Thats 12 times less than light tuna. Q: How much mercury is in albacore tuna, the kind most people prefer? A: Canned albacore tuna contains an average mercury level of 60 mcg per 6-ounce serving (three times more than light tuna). The EPA recommends no more than 6 ounces of albacore tuna a week for those at highest risk (women who may become pregnant, pregnant women, nursing mothers and young children). While were on the subject, alert readers pointed out what seemed to be an oversight in my column comparing the amount of mercury in light tuna with that in the flu shot. The purpose of the comparison was to gain some perspective on the mercury content of the flu shot. Since the essential concern with mercury is its accumulation in the body over time, I calculated that eating one 6-ounce can of light tuna a week would expose you to over 40 times more mercury per year than youd get from an annual flu shot. As one reader put it, The methylmercury in ingested tuna is unlikely to be 100 percent absorbed from the digestive tract, suggesting I may have overstated this exposure. The way the EPA presents data on the absorption issue is a bit confusing, so I e-mailed the agency for clarification and promptly found myself in a bureaucratic shuffle. Eventually I got to a knowledgeable scientist willing to confirm what the data intended to say: Almost all (95 percent) of ingested methylmercury makes it from the digestive tract into the general circulation. (For you medical types, this indicates negligible gut or liver first-pass metabolism.) For all practical purposes, then, my initial calculation holds up. On a related issue, I received a bundle of mail from readers who believed that autism, a neurodevelopmental disorder, could be traced to the use of childhood vaccines containing the ethylmercury-based preservative thimerosal. As it turns out, a riveting new book that examines this controversial but biologically plausible link recently crossed my desk. Titled Evidence of Harm by David Kirby (St. Martins Press), it lines up the known evidence while telling the stories of a handful of determined parents forced to become their own detectives. Youll get eye-opening glimpses into the trenches where once normally developing kids slip into the shuttered world of autism and where their parents refuse to be bounced off the walls of seemingly impenetrable bureaucracies. Highly recommended. | ||
Copyright 2004-Fayette Publishing, Inc. |