PCBs in fish and shellfish
PCBs, or polychlorinated biphenyls, are highly toxic industrial compounds. They pose serious health risks to fetuses, babies and children, who may suffer developmental and neurological problems from prolonged or repeated exposure to small amounts of PCBs. These chemicals are harmful to adults as well. Although they were banned from manufacture in the United States in 1977, PCBs are slow to break down and can persist in the environment at dangerous levels.
PCBs accumulate in the sediments at the bottoms of streams, rivers, lakes and coastal areas. These chemicals can build up in the fatty tissues of fish and other animals, and in high concentrations pose serious health risks to people who frequently eat contaminated fish. Based on available data on PCB concentrations in fish, Environmental Defense recommends limiting consumption of certain fish (see Health Alerts).
What are PCBs and where do they come from?
PCBs are man-made chlorinated industrial chemicals also known by the trade name of Aroclor. There are 209 different PCB compounds (called congeners), which can be mixed in different combinations to yield different Aroclor compounds. These mixtures tend to be chemically stable and nonflammable, with high boiling points and electrical insulating properties.
This combination of useful chemical properties made PCBs popular for a variety of industrial applications, including use in electrical transformers, hydraulic fluids, lubricants and carbonless paper. More than 1.5 billion pounds of PCBs were manufactured in the United States before they were banned, and some electrical equipment in use today still contains PCBs.
Unfortunately, the same properties that made PCBs ideal for industrial use make them slow to break down in the environment. Most PCBs do not mix with water and settle into riverbeds, lake bottoms and coastal sediments. Here they can enter the food chain and bioaccumulate in invertebrates, fish, birds and mammals -- including people.
Although these chemicals have been banned for many years, increased testing has recently shown that the problem of PCB-contaminated fish is widespread. According to the Environmental Protection Agency's National Listing of Fish and Wildlife Advisories, advisories for PCBs increased 177% between 1993 and 2003 (from 319 to 884). Thirty-nine states issued PCB advisories in 2003, up from 31 states in 1993. As of 2003, more than two million lake acres and 130,000 river miles were covered by some type of PCB advisory. Three states (Indiana, Maryland and New York) and the District of Columbia have issued statewide freshwater advisories, and seven states (Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York and Rhode Island) have issued statewide coastal advisories for PCBs.Statewide advisories urge people to limit their consumption of all fish and shellfish from freshwater or coastal areas.
What are the health risks associated with consuming PCB-contaminated fish?
According to EPA, contaminated fish are a persistent source of PCBs in the human diet. PCBs are not highly toxic with a single dose (as in a single meal), but continued low levels of exposure (for example, eating contaminated fish over an extended period of time) may be harmful. EPA rates PCBs as "probable human carcinogens," since they cause cancer in laboratory animals. Other tests on laboratory animals show damage from PCBs to their circulatory, nervous, immune, endocrine and digestive systems.
A number of studies indicate that PCBs harm people, with fetuses and young children especially susceptible to the effects of PCBs on their developing nervous systems. For example, some recent studies found that:
- Children of mothers who ate fish with large amounts of PCBs from the Great Lakes had smaller head size, reduced visual recognition and delayed muscle development.
- A mother's exposure to PCBs and other chemicals was linked to slight effects on her child's birth weight, short-term memory, and learning.
- Older adults (49 to 86 years old) who ate fish containing PCBs and other contaminants had lower scores on several measures of memory and learning.
How can I reduce the risks of eating seafood contaminated with PCBs?
PCBs build up in fish and animal fat, and therefore proper cooking methods can help reduce your exposure:
- 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.
- Serve less fried fish; frying seals in chemical pollutants that might be in the fish's fat, while grilling or broiling allows fat to drain away.
- For smoked fish, it is best to fillet the fish and remove the skin before the fish is smoked.
What fish should I avoid?
Fish low in contaminants are an important part of a healthy diet. That's why Environmental Defense recommends limiting consumption of certain fish due to elevated PCB levels (see Health Alerts).