Fish Consumption Advisories

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Questions and Answers About Eating Fish

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What pollutants build up in Wisconsin´s fish?

Mercury and polychlorinated biphenyls (PCBs) are the main pollutants that build up, or accumulate, in fish from Wisconsin´s waters. Because these pollutants accumulate in people who eat fish and may adversely affect health, advice is issued by health officials on how much fish may be safely eaten.

Dioxin and perflourooctane sulfonate (PFOS) are a problem in a few waterways in Wisconsin. Other contaminants, like DDT and dieldrin, have declined since earlier years and no longer require consumption advice to be issued.

Why should we be concerned about contaminants in fish?

If you eat fish, then that´s your main source of mercury and PCBs. Infants and children of women who eat a lot of fish may have lower birth weights, delayed development and impaired learning ability. These pollutants can also harm adults by affecting reproductive function and cardiovascular health, immune and nervous systems, and increasing the risk of cancer.

The DNR and Department of Health Services provides information on the number of fish meals that you can safely eat. By following fish consumption advisories, Wisconsin residents and visitors can continue to enjoy the fish they catch and benefit from this low-fat, low-cost source of nutrition, while reducing their exposure to these pollutants.

How can I reduce my intake of PCBs and mercury?

Because PCBs remain in your body for many years, it´s important to reduce your lifetime exposure to PCBs. Avoid fish with high concentrations of PCBs by looking over the list of waters with high PCBs. PCBs are generally stored in the fat of fish, so you can reduce PCB levels in fish you eat by trimming away the fatty areas and using cooking methods that allow the fat to drip away from the fillet.

In humans, the blood carries mercury to the brain and other tissues. Because mercury is stored throughout the fish including the muscle and fillet, trimming and fat removal will not reduce mercury levels, but you can prevent mercury from building up in your body by eating fish with low mercury concentrations and spacing your fish meals out over time. Our fish consumption advice [PDF 1MB] provides a list of waters along with recommended meal frequencies that vary with the species and size of the fish.

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What is mercury? How does it get into fish?

Mercury is a natural element that occurs in rocks and soils. However, it is released into the atmosphere when power plants burn coal, from some chemical manufacturing plants and incinerators, and when mercury containing products are not disposed of properly. Mercury is also released into the air when volcanoes erupt, forests or peat burn, and soils decompose. After it is released, mercury travels with weather systems, changes chemical form, and deposits on land and water.

In surface waters, mercury can again change forms depending on the conditions of the water. The methylated form, methylmercury, accumulates in insects and other organisms. When small fish eat the insects and big fish eat the small fish, mercury levels accumulate up the food chain. Fish that eat other fish (predator fish such as walleye) and older or larger fish contain the highest amounts.

What about PCBs?

PCBs are a group of man-made chemicals. There are no known natural sources of PCBs. PCBs were used in a variety of industries and products including carbonless copy paper, coolants and lubricants in transformers and capacitors, and as cutting oils and hydraulic fluids. Manufacture of PCBs was banned in the US in 1977.

PCBs remain in the environment because they are resistant to breakdown. PCBs attach to sediments and, like mercury, accumulate in the food chain. Fish that are older and have fattier tissues, accumulate higher levels of PCBs. Fish that eat other fish have higher levels of PCBs compared to fish that only eat aquatic bugs.

Where are mercury and PCBs?

Mercury and PCBs can be found throughout the environment. PCBs can reach high concentrations in some fish from industrialized river systems, where industries and manufacturers that used PCBs were located, and from the Great Lakes. Mercury reaches higher concentrations in fish from acidic, darkly stained waters with adjoining wetlands, typical of many lakes of northern Wisconsin.

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Why should I eat fish?

Fish are typically a good source of protein that are lower in harmful saturated fats. Fish can be a good source of beneficial fatty acids. Fish provides health benefits as long you follow advice for the number of meals and species you can safely eat. Studies suggest that regularly (1 to 2 servings per week) including modest amounts of fish and shellfish in your diet can benefit your health. Little additional benefit is obtained by eating more than 1 to 2 servings per week.

If you eat a lot of fish, you can lower your exposure to pollutants by eating small fish such as perch and bluegill or smaller sizes of predator fish. It´s safe to catch and eat fish from most of Wisconsin´s lakes and rivers so long as you follow the safe-eating guidelines.

What will happen to me or my children if I eat a contaminated fish?

In the future, use the fish consumption advisory as a guide for how much fish to consume from lakes and rivers carrying advisories. The health risks from eating a few meals of contaminated fish are still relatively small.

Are the fish I buy in a store or from a restaurant contaminated too?

Most ocean fish you´ll find at the store - species such as pollock, shrimp, and salmon - have very low levels of mercury. However, the U.S. Food and Drug Administration (FDA) [exit DNR] recommends that pregnant women and those planning to get pregnant not eat swordfish, shark, king mackerel and tilefish because these species contain high levels of mercury. Wisconsin fish fry typically is cod, haddock, or perch, which are among the safest species of fish to eat.

You have little cause for concern if you eat or buy a variety of commercial fish or eat less than one meal per week of fish. Regardless of whether the fish you eat is store-bought or caught from Wisconsin waters, monitor the amount and species of fish you are eating and follow the state´s fish consumption advisory to decide which are safest.

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What fish have been tested?

The DNR has tested fish from over 1,600 sites in Wisconsin since the 1970s, focusing efforts on popular lakes and rivers and those near industrial centers. Because of the large amount of data we´ve gathered, we know how much mercury is generally found in different fish species. As a result, most - but not all - inland lakes carry the same statewide advice for how many meals of certain species people can safely eat while reducing their risk of exposure to mercury. Some waters have more restrictive advice due to higher concentrations of mercury or PCBs. There are also separate recommendations for sensitive populations including women of childbearing years, nursing mothers and all children under the age of 15.

Can I swim in waters with an advisory?

The amount of contaminants you would inadvertently ingest as a result of swimming in waters contaminated with environmental toxins is insignificant. However, ingesting surface waters should be avoided unless first properly treated because other pollutants may be present.

What about fishing and eating fish from flooded areas?

No matter where you choose to fish, select healthy fish and healthy tissue for cooking and eating. Keep the fish cool until you fillet it. Wash your hands, utensils, and surfaces after handling surface waters, fish or any raw food. After filleting, rinse the fillet with clean water and refrigerate, freeze, or cook the fillet thoroughly.

When you catch fish from a flooded area and you suspect that there is danger from bacteria, blue-green algae, or other pathogens, wash your hands after handling fish or the polluted water. Also, be careful in areas where flooding has occurred because the shore on these lakes or rivers can be unstable and there may be debris under the water that you cannot see because the water is murky.

What is being done to reduce contamination of Wisconsin´s fish?

Wisconsin has taken many actions to reduce mercury emissions and to clean up PCBs which remain in sediments of some waters of the states. For further information, please see DNR´s mercury or sediment management Web pages.

For more information on contaminants in fish, please contact:
Candy Schrank, Aquatic Toxicologist
(608) 267-7614

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Last Revised: Thursday August 21 2008