Concerned about the Safety of Eating Fish from the Great Lakes?

Eating fish is healthy

Fish offers many health benefits. It is a good source of protein and other nutrients. In addition, it's lower in saturated fat than beef or poultry and may protect against heart disease. (See "Low in Calories, High in Nutrition" for more information about the health benefits of eating fish. See the calorie table for specific nutrient information.)

Fish is loaded with a type of fatty acid that seems to lower blood cholesterol levels, and its oils may be linked to lowering blood pressure.

Health benefits aside, catching your own fish is both fun and economical!

But some sport-caught fish can be harmful

Certain fish are likely to be contaiminated by two different toxic chemicals: mercury and polychlorinated biphenyls (PCBs). These are the two major contaminants in sport fish found in Wisconsin. Mercury is a naturally occurring metal and is also emitted from coal-burning power plants. It will persist in the environment for generations. PCBs are synthetic oils, once widely used in industrial processes and products.

Other known fish contaminants such as toxaphene, dieldrin, DDT, and dioxin are not as commonly found in Wisconsin fish as PCBs and mercury.

What are PCBs?

PCBs are colorless and odorless chemicals that were widely used in electrical equipment and other industrial applications before they were banned in 1976. These man-made chemicals are considered toxic because exposure to small doses is suspected of contributing to a variety of health problems. PCBs do not quickly decompose into less harmful chemicals, so they are extremely persistent in the environment.

How do these contaminants get into fish?

Water runoff and rain carry PCBs and mercury into lakes and streams. These chemicals can build up on the bottom of rivers and lakes. Numerous bottom-dwelling animals eat these contaminated sediment particles. These animals, in turn, serve as food for fish.

Since PCBs and mercury don't degrade, they become increasingly concentrated in the bigger fish higher up the food chain. PCBs accumulate in the fat of these fish, and mercury spreads throughout their bodies. This means that the bigger, older fish have higher amounts of these toxins than smaller, younger fish.

Contaminants pose the greatest risk to certain groups of people

PCBs build up in a person's body fat too. When you eat unsafe fish, PCBs stay with you throughout your lifetime. Mercury is also a problem because the body eliminates it only very slowly. You can build up harmful levels of these chemicals and not even know it.

Medical studies indicate the risks of developmental or health problems are highest for the developing fetus and nursing infant. A woman who has accumulated high levels of PCBs in her body can transfer large doses of PCBs directly to her fetus while pregnant, and later her infant can receive additional PCBs through her milk. Because they are smaller, children can receive a higher body-dose of PCBs than adults eating the same size fish. Therefore, if they eat any sport fish, young children (especially girls) and women of child-bearing age should eat only those fish with the lowest levels of contaminants.

Scientists suggest that the unborn child exposed to PCBs during pregnancy may weigh less at birth and have a smaller head. These babies can develop problems that are hard to detect until years later; such as learning disorders and memory difficulties. Children's developing bodies may be especially sensitive to the effects of these chemicals. Exposure to PCBs may also cause cancer.

Mercury can damage the nervous system. Eating fish with even moderately high levels of mercury during pregnancy might lead to a delay in children's ability to walk, talk, or learn.

What kinds of fish are most contaminated?

It is the larger older fish, which have eaten more food, that have the highest levels of PCBs. Lake trout can live in Lake Michigan for 10 years, so they generally contain more PCBs than chinook salmon, which only live in the lake for 3 to 4 years. Coho salmon, which are in the lake only two or three years, contain even lower amounts than chinook salmon. However, the amount of PCBs in two similar sized fish of the same species, caught in the same area of the lake, can vary greatly.

Can cleaning reduce PCB levels?

Yes, but not always enough. It is important to remember that Great Lakes fish advisories are based on fish prepared in the following way:

-Remove all skin.
-Cut away all fat along the backbone.
-Slice off the belly fat along the bottom.
-Cut away a V-shaped wedge along the lateral line on each side of a whole fish or on the skin side of each fillet.

Note that these preparations will not reduce the amount of mercury in a fish meal. Mercury is distributed in a fish's muscle tissue, not the fat and skin. The only way to reduce mercury intake is to reduce the amount of contaminated fish you eat.

Can cooking fish reduce PCB levels?

Yes. While cooking does not destroy PCBs, the heat from cooking melts the fat in the fish, thus removing some of these contaminants. It is best to broil or bake trimmed, skinned fish on an elevated rack so any additional fat melted out of the fish drops off. Do not use the drippings for sauces: Dump the drippings in the garbage. If you boil or poach your fish, discard the fish broth. Studies on smoked fish have shown that while some oil leaves the fillets, a signficant amount of moisture also leaves, so smoking does not substantially reduce PCB levels.

How can I find out which fish are safe to eat and which are not?

The Wisconsin Divison of Health of Health and Wisconsin Department of Natural Resources release a set of guidelines every year that categorize different fish from Wisconsin rivers and lakes (including Lake Superior and Lake Michigan) into the acceptable number of meals per week, month, or year. You can obtain the Fish Advisory by calling or writing the Wisconsin DNR Bureau of Fisheries Management and Habitat Protection, P.O. Box 7921, Madison, WI 53707, (608) 266-1877. The information is also available on their web site.

Be aware that each state has its own set of guidelines and advisories.

This page is Bobby Approved.