Common Questions on Health Alerts

If the health advisories for contaminants are most important for women and children, why in some cases women can eat more fish in a month than men?

Our advisories are calculated based on average body weight and typical meal sizes for men and for women -- the two most important factors in determining intake of contaminants by eating seafood. Women weigh less on average than men (144 pounds versus 172 pounds), and we assume they eat smaller portions as well (6 ounces versus 8 ounces).

The difference in portion size has a greater effect on the calculation than the difference in body weight; therefore in several instances women can safely eat slightly more portions of a particular fish in a month than men (such as wild salmon from California, Oregon and Washington).

In the case of mercury, our methodology – taken from EPA – is designed to protect women of childbearing age and children (more on methodology).

What about natural toxins in seafood?

Besides industrial pollutants and other human-made contaminants, seafood may contain natural toxins that pose health risks. These cases are rare, but important to be aware of nonetheless:

  • Large, predatory fish in warm tropical waters may contain high levels of a toxin called ciguatera. Cooking does not destroy the toxin, and consumption of ciguatoxic fish can cause intense flulike symptoms.
  • If not stored properly soon after capture, tuna, mackerel, bluefish and mahimahi develop a histamine called scombrotoxin. Eating fish (even cooked fish) with high concentrations of scombrotoxin can cause an allergylike reaction, which is treatable with an antihistamine.
  • Uncooked shellfish may contain disease-causing bacteria, viruses or parasites, which they inadvertently strain from the surrounding seawater. The Norwalk virus, which causes intestinal illness in humans, is often associated with eating raw oysters and clams.

Bottom line: Make sure you get your seafood from a reliable source, and ensure that your shellfish is cooked thoroughly.

How can I cook fish to reduce toxins?

Unfortunately, there are no cooking methods that will reduce mercury levels in seafood since it binds to proteins in fish tissue (including muscle). However, levels of PCBs can be reduced by the following cooking methods, since these toxins build up in fatty tissue.

  • Before cooking, remove the skin, fat (found along the back, sides and belly), internal organs, tomalley of lobster and the mustard of crabs, where toxins are likely to accumulate.
  • When cooking, be sure to let the fat drain away, and avoid or reduce fish drippings.
  • Frying seals in chemical pollutants that might be in the fish's fat, while grilling, broiling or poaching allows fat to drain away.
  • For smoked fish, it is best to fillet the fish and remove the skin before the fish is smoked.

How can I avoid getting sick from eating seafood?

  • Check fish carefully before buying. Bruises, brown spots and cloudy or sunken eyes all indicate decomposition, and possibly bacteria. Buy fish that was frozen or refrigerated immediately after capture.
  • Cook fish and shellfish thoroughly. Handle raw fish as you would handle other raw meat products. Take care not to cross-contaminate cooked food or vegetables with the utensils used to prepare raw fish, and wash utensils and hands thoroughly in-between handling.
  • Avoid shellfish from untraceable sources, particularly if eaten raw.

How can I reduce the risks of both industrial contaminants and natural toxins?

Fish consumption is the primary route of exposure to contaminants like mercury and PCBs. Since these substances can damage developing nervous systems and impair learning, seafood contamination is a particular concern for young children and women of childbearing age. The best ways to reduce exposure are:

  • Reduce consumption of fish known to be high in contaminants.
  • Prepare your fish in a way that cuts down on toxins.
  • If you eat sport fish, consult local advisories first. If none are available, limit your intake to once a week.

What is the government doing about these problems?

Two government agencies are responsible for determining the safety of fish caught or eaten in the U.S. National standards and recommendations concerning commercial seafood (what you would find in a restaurant, grocery store or fish market) originate from the Food and Drug Administration (FDA). For recommendations concerning sport fish caught in local waters, individual states work in conjunction with the Environmental Protection Agency (EPA) to test fish and issue fish consumption advisories. EPA's guidance is generally regarded as more protective of consumers than that of the FDA, especially regarding acceptable levels of mercury and PCBs. In addition, many states now also offer their own health advice for commercial fish.

What fish should I avoid?

Low-contaminant fish are an important part of a healthy diet, and Environmental Defense encourages people to include such fish in their diets, especially if they are caught or farmed in an environmentally responsible manner. However, there are certain species that people (especially women of childbearing age and children) should eat in moderation or avoid altogether (view ourHealth Alerts chart)