Fishing for some clarity
One debate about the modern seafood industry focuses on heavy metals and other toxins in the fish we eat, especially large predators such as tuna. The press's alarmist coverage suggests that we should all stop eating tuna salad sandwiches and toro sushi.
After much hue and cry, the public has been left with a murky understanding of the key facts in this discussion. Environmental toxins such as mercury and polychlorinated biphenyls (PCBs) are mainly relevant to women in their childbearing years, pregnant women, breastfeeding women, babies, and young children. Why? Because these compounds affect fertility, gestation, embryogenesis, and early childhood development.
In these at-risk groups, exposure to high concentrations of mercury or methylmercury (MeHg), both potent neurotoxins, can result in mental retardation, cerebral palsy, and seizures.
But outside of the demographic I mention above, these compounds do not significantly affect our population.
In the end, it's about running the calculus of risk assessment. Pregnant women should avoid tuna and other fish from the top of the food chain. They should avoid wild fish native to the polluted fresh waters of the US and other countries. They should eat fish that are harvested at a young age, such as salmon. Fish such as tuna and swordfish are taken from the sea after years of exposure to and accumulation of toxins from the fish they eat.
Even following these guidelines (more can be found at the links below), pregnant women should eat these fish in measured doses, eat a wide variety of protein and omega-3 containing foods, and pay close attention to the source of their food.
If you want "cleaner" seafood, farmed fish can be a healthy option if you find a fishery that buys certified toxin-free fish feed, which is very expensive. Farmed fish that eat ground-up and toxin-rich fish-based feed, the majority of farmed fish aquaculture, become toxin sponges. Wild fish might potentially have fewer heavy metals but there is never a 100% guarantee that your particular fish didn’t grow up on the wrong side of the tracks. Fish-by-fish testing is just not available to the retail-level consumer.
If you are not a female of childbearing age, pregnant, or breastfeeding, eat that tuna without much guilt, but don't feed tuna, swordfish, tilefish, shark, and other large fish to your kids. (See this link for a listing of fish and their mercury content)
Please wait until their little brains have had a good chance to develop properly. While it is not clear when neural development is no longer susceptible to injury due to mercury exposure, it is clear that critical development continues well into the teen years.
Do what you can to help young women, pregnant mommas, and children in your life move away from these food sources.
Resources for Learning:
FDA: Mercury Levels in Commercial Fish and Shellfish Updated February 2006
FDA: What You Need to Know About Mercury in Fish and Shellfish - 2004 EPA and FDA Advice For: Women Who Might Become Pregnant, Women Who are Pregnant, Nursing Mothers, Young Children
EPA: Fish Advisories
EPA: Mercury information site
Without getting too political about the effect that the current administration has had on the integrity of certain government agencies, remember to never rely on a single source of information.
Note that organic definitions don't exist for fish. The USDA has not advocated for organic standards in the past, but policy makers have co-opted the term to ease the way for non-organic food producers to capitalize on this market niche.
A source for Organically fed Farm Fish:
Black Pearl Natural Choice brand (at some Whole Foods Markets)