Pesticides in Fish and Shellfish

Posted: 29-Aug-2004; Updated: 19-Aug-2005

Overview

RELATED ARTICLES Dioxins in Fish and Shellfish Mercury in Fish and Shellfish PCBs in Fish and Shellfish LEARN MORE Scorecard.org Chemical Profile - Aldrin/Dieldrin Scorecard.org Chemical Profile - Chlordane Scorecard.org Chemical Profile - DDT/ DDD/ DDE Scorecard.org Chemical Profile - Mirex Scorecard.org Chemical Profile - Toxaphene EPA Chemical Fact Sheet - Toxaphene Agency for Toxic Substances and Disease Registry: Aldrin/Dieldrin Fact Sheet Agency for Toxic Substances and Disease Registry: Chlordane Fact Sheet Agency for Toxic Substances and Disease Registry: DDT/DDE/DDD Fact Sheet Agency for Toxic Substances and Disease Registry: Mirex Fact Sheet Agency for Toxic Substances and Disease Registry: Toxaphene Fact Sheet Office of Environmental Health Hazard Assessment, State of California New York State Department of Health. "2003-2004 Health Advisories: Chemicals in Sportfish and Game" Texas Department of Health. Fish Consumption Advisories & Bans

Certain pesticides pose particular problems when they contaminate seafood, since the properties that make these chemicals effective pest control agents also make them slow to break down in the environment. These pesticides accumulate in the bottom sediments of streams, rivers, lakes and coastal areas, and are most commonly found in the fatty tissues of fish. Since many of these man-made chemicals have been banned for years, their levels are generally decreasing over time. However based on the available data on pesticide concentrations in fish, Environmental Defense recommends limiting consumption of certain fish. (View our Health Alert charts.)

Which Pesticides Should I Worry About and How Do They Get Into Fish?

Chlordane
Chlordane is a man-made chlorinated pesticide that was banned from use in the late 1980s. It was used as a general agricultural and home and garden pesticide until the late 1970s, when its use was restricted to termite control only.

Laboratory animals exposed to chlordane have increased tumor rates, and exposure in the womb can harm a fetus's developing nervous and immune systems. Several studies associate prenatal and early childhood exposure to chlordane with brain tumors and leukemia, while adult exposure is linked to liver and nervous system damage. EPA designates chlordane as a probable human carcinogen. Since chlordane builds up in human tissues, children and women of childbearing age should be especially careful to minimize their exposure to this pesticide.

The good news is that a number of advisories for chlordane have been rescinded in recent years as the chemical slowly decreases in the environment, according to EPA's National Listing of Fish and Wildlife Advisories.

The DDT Family (DDT, DDD, and DDE)
DDT was banned from use in the early 1970s, thanks in part to litigation by Environmental Defense. Once widely used, DDT was sprayed to control agricultural pests and biting insects like mosquitoes. DDE and DDD are chemical breakdown products of DDT, and all three are slow to degrade and can persist in the environment for long periods of time.

Although human exposure to DDT has declined since it was banned, people who eat fish containing elevated levels of DDT and its breakdown products can still be harmed. In humans, prolonged or repeated exposure to small amounts of DDT can result in premature birth and low birth weight, shortened duration of lactation, spontaneous abortion and nervous system damage. EPA classifies DDT and DDE as "probable human carcinogens."

According to EPA's National Listing of Fish and Wildlife Advisories, California, Texas and Delaware had the greatest number of DDT advisories active in 2003 (14, 5 and 5, respectively).

Dieldrin/Aldrin
Dieldrin, like chlordane and DDT, is a chlorinated organic pesticide. Dieldrin is also a breakdown product of aldrin, another banned pesticide. Dieldrin was used to control corn and citrus pests until it was phased out in the 1970s and 1980s. Excessive dieldrin exposure in humans can cause tremors, convulsions, and liver and nervous system damage. Animals given very low doses have offspring with fetal defects. EPA considers dieldrin a "probable human carcinogen."

Mirex
Mirex is a man-made pesticide used to control fire ants until it was banned in the United States in the late 1970s. Mirex was also used as a flame retardant in plastics, rubber, paint, paper and electrical goods until the early 1970s. EPA classifies Mirex as a "probable human carcinogen," since long-term exposure causes cancer in laboratory animals. Other symptoms in animals from exposure include damage to the liver, thyroid, kidneys, and nervous and reproductive systems.

Toxaphene
Toxaphene was used primarily as an insecticide on cotton until EPA banned it in 1982. Toxaphene is classified as a "probable human carcinogen" and causes liver tumors in mice. Long-term, low-level exposure can cause degenerative changes in the liver, kidney, and nervous system of animals.

How Can I Reduce the Risks of Eating Seafood Contaminated With Pesticides?

Many pesticides -- including chlordane, DDT, dieldrin and mirex -- persist in animal tissues and are stored in fat. Proper cooking methods can help reduce your exposure to these chemicals:

• 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 pesticide levels.

View full chart.