Class Notes: Shopping for Seafood
When you are standing at the seafood counter pondering your choices for dinner, you’re probably not thinking about coal-burning power plants or synthetic pesticides in agricultural run-off water. But you should be. Conventional farming and coal-burning power plants are the two largest industries responsible for contaminants in our lakes, rivers and oceans.
Seafood is a terrific protein source. It is much lower in fats than other animal proteins and most of the fat from seafood is the healthy kind, unsaturated fats. But it seems like you can’t talk about seafood these days without talking about PCBs and methylmercury. In some stores you’ll even find warning labels posted in the seafood departments. Which leaves many of us asking “which fish are safest?” The answer is slightly different for methylmercury than it is for PCBs, so I’ll deal with them separately.
Mercury
Mercury contamination in seafood is unfortunately nothing new. As early as the 1930s, mercury contamination in seafood was identified as the cause of children being born with severe brain damage. It happened in a small fishing community: Minamata, Japan. Thousands of children were affected by industrial waste being dumped into the bay by Chisso, a plastics and pesticide manufacturer. So while the scientific community was well aware of the hazards of mercury, the world public remained ignorant. The US government did not issue its first advisory about mercury in seafood until 1994. It took another 5 years for congress to call for research on the subject to find out what constitutes a safe level and which fish should be avoided. The resulting report that was published a year later was vague and confusing, leaving a lot of guesswork to the consumer.
Let’s just get the bad news out of the way: All seafood contains methylmercury. We’ve been burning coal for power for quite some time now. Mercury is spewed into the atmosphere by the power plants, but it is heavy so it readily falls back to earth landing in lakes, rivers, soil, oceans…everywhere. Once in the water supply, microorganisms turn it into methylmercury. Then the little fish each the microscopic organisms and the bigger fish eat the little fish — and so on. Methylmercury accumulates in muscle tissue and big predatory fish eat lots of smaller fish, so they accumulate higher concentrations of methylmercury.
So here’s the skinny on methylmercury: Filter feeders and smaller fish have less; Big predatory fish have more.
Filter feeders and smaller fish include: sardines, herring, bay scallops, clams, mussels, Pacific cod, Dungeness crab, trout, striped bass
Avoid these: shark, swordfish, tilefish, king mackerel, albacore tuna, Chilean seabass, Groupers
There are many other fish that fall in the “eat only occasionally” category. Refer to the fish lists at the end of this article for a more comprehensive listing.
PCBs
PCB, polychlorinated biphenyls, is a category of chemicals that includes some particularly nasty synthetic agricultural pesticides such as chlordane, dieldrin, and DDT. Many of these pesticides have been banned for years, but guess what – they’re still lingering in the environment. Just like methylmercury, the higher you go on the food chain, the higher the concentrations of PCBs. PCBs accumulate in fatty tissue, so the fattier the fish, the higher the concentration of PCBs. In general, farm-raised fish have higher levels of PCBs because they are fed fish meal made from larger fish that have been ground up. This reverses the order of the big fish eating the little fish.
General guidelines for minimizing PCB consumption: Choose Wild over farm-raised, select fish lower on the food chain(non-predatory fish), and choose leaner, less fatty fish.
Fatty Fish include: Orange roughy, swordfish, carp, fresh tuna, eel, so use caution with these.
So asking “which fish are the safest to eat?” is a really good question. But a better question to ask is “Why are PCBs and methymercury in our oceans and why is the problem getting worse?” You can attempt to follow the Fish Lists that advise which fish to enjoy and which to avoid, but if we don’t address the problems of coal-burning and conventional farming, eventually all fish will be on the “Avoid” list.
If you want clean fish, GET INVOLVED!
- Offset some or all your households energy usage with windpower.
- Speak with your dollar – Buy organic fruits and vegetables.
- Use the seafood guides to avoid fish that are high in contaminants or are not sustainably farmed
- Write to your senators and congressional representatives and tell them you want tougher emissions standards for coal-burning power plants.
- Write to your senators and congressional representatives and tell them you want stiffer penalties and stronger enforcement for industrial polluters.
For More Information:
www.mbayaq.org access printable pocket seafood guides
www.seafoodchoices.com this site does not offer any lists directly. It acts as a clearing house for numerous organizations.
www.epa.gov find out about advisory on lakes and rivers in your state
If you’re on your mobile phone, you can go to fishphone.org to find out about the dish you’re considering for dinner tonight
Check out Marion Nestle’s book What to Eat
For more information on wind energy and other alternative energy sources, visit these web sites: