PCBs  (polychlorinated biphenyls) are chemicals that have been used as coolants and lubricants in electrical equipment.

Since PCBs are found throughout the environment, it is likely that everyone has been exposed to them. PCBs can enter the body by eating or drinking contaminated food, through the air we breathe, or by skin contact. PCBs are easily absorbed by the body and are stored in fatty tissue. PCBs are not eliminated well, so they can accumulate in the body.

Most people are exposed to PCBs by eating contaminated fish, meat, and dairy products. The highest PCB levels in fish are seen in:

• Catfish
• Buffalo fish
• Carp
• Walleye
• Tuna, bluefin
• American eel
• Croaker
• Flounder
• Wild sturgeon
• Blue crab
• Wild Alaska salmon

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.

Read more in this list of seafood health alert.

Plants take up only small amounts of PCBs from the soil, so amounts in grazing animals and dairy products are generally lower than in fish. Dust contaminated with very small levels of PCBs may be found on the outer surfaces of fruits and vegetables.

They are part of a category of chemicals known as persistent organochlorine pollutants and include industrial chemicals and chemical byproducts as well as pesticides. In many cases, the compounds are present in soil, water, and in the food chain. The compounds are resistant to decay, and may persist in the environment for decades. Some, known as persistent lipophilic organochlorine pollutants, accumulate in fatty tissues. Another type, called perfluorochemicals , are used in clothing, furniture, adhesives, food packaging, heat-resistant non-stick cooking surfaces, and the insulation of electrical wire.