PCBs and DDT
PCBs and DDT are chemicals that were banned more than 30 years ago, but our air, water, land, and bodies are so contaminated that decades of cleanup efforts have yet to eliminate their threats to our health. Today, food is one of the most likely exposure routes to PCBs.
PCBs – polychlorinated biphenyls – are synthetic (human-made) chemicals first produced in the late 1920s. They were used as cooling fluids in electrical equipment and machinery because of their durability and resistance to fire.
- Monsanto stopped producing them in 1977. The EPA mandated phase out of most uses shortly thereafter.
- PCBs have a similar chemical structure to PBDEs, which are currently used as flame retardants in electronics, furniture, and other consumer goods.
DDT – dichloro-diphenyl-trichloroethane – was developed as an insecticide in the 1940s, and was widely used during World War II to combat insect-borne diseases.
- DDT’s effectiveness, persistence, and low cost made it popular for agricultural and commercial uses. More than a billion pounds were used in the U.S. over a 30-year period.
- EPA banned nearly all domestic uses of DDT in 1972, after the publication of Silent Spring and broad public outcry about DDT’s impacts on wildlife and people.
- Today, use of DDT is limited to malaria control programs in some developing countries.
We are still exposed to PCBs and DDT through our food.
- Animal and fatty foods contain the highest levels of DDT and PCBs because they are stored in fat and increase in concentration as they move up the food chain.
- Even though it was banned in 1972, vegetables, meat, fish, and dairy products contain DDT.
- PCBs and DDT build up in sediment in rivers, lakes, and coastal areas, then accumulate in fish.
- Women who consume PCBs in their diet pass them to their children in breast milk: infants may get 6 to 12% of their lifetime exposure to PCBs from breastfeeding.
- PCBs are a major contaminant in Puget Sound where they are found at very high levels in salmon and in endangered orca whales, among the most contaminated marine mammals in the world.
- PCBs can have profound effects on intellectual development. Children with greater exposure to PCBs have lower birth weights, slowed growth, and poorer performance on tests of brain development.
- PCBs cause tumors in laboratory animals. EPA lists PCBs as probable human carcinogens.
- Studies suggest that PCBs are also toxic to the immune system, reproductive organs, and thyroid.
- Exposure to DDT is harmful to the nervous system. People exposed to high levels exhibit dizziness, tremor, irritability, and convulsions. Workers with longer term exposure have lasting neurological and cognitive problems.
- Pregnant women exposed to DDT are more likely to have premature or small-for-gestational-age babies. DDT is considered a hormone disrupting chemical due to its estrogen-like properties.
- DDT causes cancer in laboratory animals. EPA lists DDT as a probable human carcinogen.
The histories of DDT and PCBs are both success stories and cautionary tales. Since these chemicals were banned 30 years ago, levels in our bodies have declined. And yet, we still face levels that could be causing harm—decades after regulatory action.
PCBs are a major contaminant in Puget Sound, and evidence is accumulating that they are a serious threat to the Sound’s wildlife, too.
- Puget Sound’s endangered orca whales have accumulated PCBs to the point that they rank among the most contaminated marine mammals in the world.
- Levels in orcas already exceed those needed to cause health effects such as immune system depression.
- To this day, runoff from agricultural lands transports DDT-containing sediment to rivers and streams, where it is taken up by fish.
Washington state should restore the health of Puget Sound by: fully cleaning up PCB contamination; preventing recontamination; and phasing out other persistent toxic chemicals such as PBDEs and perfluorinated compounds.
Unless you live near an industrial or agricultural site contaminated with PCBs or DDT, your greatest source of exposure to these chemicals is likely to be food. While you cannot completely avoid these chemicals in your diet, you can make some choices that will help reduce your exposure to them.
The most important actions you can take to reduce the PCBs and DDT in your diet are to cut back on animal fats and watch the type of fish you eat.
Choose fish wisely. Check with state advisories before eating sport-caught fish or shellfish, which are often high in PCBs and DDT. Commercial fish that are high in PCBs include Atlantic or farmed salmon, bluefish, wild striped bass, white and Atlantic croaker, blackback or winter flounder, summer flounder, and blue crab. Commercial fish that contain higher levels of pesticides, including DDT, are bluefish, wild striped bass, American eel, and Atlantic salmon.
When preparing fish, remove the skin, trim the fat, and broil, bake, or grill the fish so that the fat drips away; this will reduce your exposure to PCBs and other toxic chemicals that have accumulated in fatty tissue. Fish are an excellent source of nutrients including protein, omega-3 fatty acids, and vitamin D, so don’t remove fish from your diet—but do be selective about the fish you eat.
Make your meat lean. When it comes to meat, choose lean meat cuts, and buy organic meats if possible. Cut off visible fat before cooking meat and choose lower-fat cooking methods: broiling, grilling, roasting or pressure-cooking. Avoid frying meat in lard, bacon grease, or butter.
Limit dairy fat. Opt for low-fat, organic options when it comes to dairy products, too.
For more information on pollutants in fish, meats, and dairy, see: