One of the saddest consequences of our modern way of life is how badly we’re polluting our oceans. It’s gotten so bad, in fact, that it’s virtually impossible to find fish or seafood that isn’t contaminated with mercury. Runoff from agricultural products and waste from other industries have turned the oceans into toxic waste dumps, and the fish we eat end up absorbing these chemicals. As a result, humans end up ingesting this mercury when they consume seafood and other types of fish.
Mercury in restaurant tuna
A recent study by Jacob Lowenstein and his colleagues at Columbia University sampled sushi tuna from 54 restaurants and 15 supermarkets in Colorado, New York, and New Jersey. As anticipated, they found that mercury content tended to increase in step with the size of the fish, from yellowfin to bluefin. Roughly 15 samples from restaurants exceeded the FDA’s 1 part per million level, as did a couple of samples from the supermarkets. (Raloff, 2010)
Mercury levels in canned tuna
Mercury content can vary dramatically between tuna species, depending on the size of the fish. Bigger fish tend to accumulate higher levels of the toxic metal. They eat the littler fish, and this builds the stores of mercury in their system. So what about canned tuna?
A different study by Shawn Gerstenberger and his colleagues published in the February 2010 edition of the journal Environmental Toxicology and Chemistry probed this question. They shopped at stores for canned tuna, buying 155 cans of solid-white, chunk-white and chunk-light tuna from three of the most popular national brands. The results: average mercury concentrations in all three brands exceeded 0.5 ppm. One brand averaged more than 0.7 ppm. Worse yet, depending on the brand, around four to seven percent of the samples surpassed the FDA’s 1 ppm cutoff point for toxicity. (ibid)
Mercury in freshwater fish
It’s not just seafood that is contaminated with mercury. Freshwater fish pulled from rivers, lakes and streams all throughout the U.S. contain it too. A recent government test of fish pulled from nearly 300 different streams in the U.S. found each and every one was tainted with some level of mercury. Twenty-seven percent of the samples had mercury levels that were high enough to exceed the EPA guidelines, meaning it would be dangerous to eat the fish more than twice a week. The highest mercury levels were found in largemouth, smallmouth and spotted bass. The lowest levels were found in brown trout, rainbow-cutthroat trout and channel catfish. Forty-eight states have fish consumption advisories in place for different species in their state. (Weise, 8-20-2009) To see the full list of such warnings, visit www.epa.gov/waterscience/fish/advisories.
Is it safe for children to eat seafood?
So what does this mean for your child? Fish is often said to be brain food, but the mercury found in fish can erase its nutritional advantages for cognition and may even reverse its benefits, doing more harm than good in the long run. At the 0.5 ppm mercury levels, a 55 pound child is only able to safely eat one serving of white tuna every two weeks without exceeding safe levels of mercury exposure, according to Gerstenberger and his team. Considering all three major brands averaged 0.5 ppm, mercury-conscious parents may want to limit the amount of canned tuna their child consumes.
As for types of tuna, light tuna offers the best choice for low-mercury content. It averaged 0.28 ppm mercury, versus 0.5 ppm in chunk-white tunas, a significant difference. White tuna consists of albacore only; light is mostly skipjack.
How much fish can a person safely eat?
Just how much does eating the wrong types of fish increase your mercury exposure? Get our e-book Toxic Childhood to read about the man who decided to test this out on himself, and what this self-experiment revealed.