DDT Pesticides, PCBs, & Other Organochlorines

What are Organochlorines? Organochlorines are a class of compounds with a similar chemical structure that persist in the environment and in the bodies of humans and other animals long after their use, including Dichlorodiphenyltrichloroethane, or DDT, and Polychlorinated biphenyls, or PCBs, among others.

What is DDT?

  • DDT was widely used as a pesticide in agriculture and insect control from the 1950s to the 1970s in the United States.

What are PCBs?

  • PCBs are oils that do not catch fire under conditions of extreme pressure or temperature, and were widely used in transistors, capacitors, and other electronics equipment during the 1950s to the 1970s in the United States.

Why are we concerned about DDT and PCBs?

  • Both DDT and PCBs are extremely persistent in the environment, lasting for years or even decades in soil and lake sediment, where DDT often breaks down into DDE, a toxic compound that is also extremely persistent.
  • DDT, DDE and PCBs are also are very long lasting in the human body, accumulating in fat (including breast milk), and most Americans have detectable levels of DDE and PBCs in their bodies. Female mammals, in general, have lower body burdens of these chemicals than males, due to the transfer to their offspring through breast feeding.
  • DDT, DDE, and PCBs have been associated with increased risk of cancer, developmental delays, and disruption of endocrine function, including thyroid hormones which have a similar structure to PCBs, and which are essential in fetal and child neurodevelopment.
  • The main source of human exposure to DDT, DDE and PCBs is through diet, particularly meat, dairy products and fish. High concentrations of these compounds can be found in fatty, long-lived fish such as lake trout and catfish because, although they may be present in the water at extremely low concentrations, they bioaccumulate in aquatic organisms. The compounds become concentrated as they move up through the food chain, and have been detected in polar bears, marine mammals and humans in regions where neither compound has been used due to their powerful resistance to degradation.

What is being done?

  • DDT was banned for use in the United States in 1973 and production of PCBs halted in 1977 due to growing concern about their increasingly-evident negative impacts on wildlife, human health and the environment.
  • The landmark 1962 book, Silent Spring by Rachel Carson, centered on DDT and other persistent pollutants as a source of environmental and public health concern. This book is credited with spurring the U.S. ban of DDT, as well as initiating the modern environmental movement.
  • DDT and PCB use and production were banned by the 2001 Stockholm Convention on Persistent Organic Pollutants, with 170 signatory countries as of 2008. This ban constitutes an international environmental treaty that aims to eliminate or restrict the production and use of persistent organic pollutants.
  • An exception was made for DDT under the Stockholm Convention ban for the public health interest use of DDT to control the mosquitoes that carry malaria. DDT is exceptionally effective tool for the prevention of malaria, which infects 250 million and kills 880,000 people annually. In this capacity, DDT use is currently increasing in some countries where malaria is prevalent.

Findings from CERCH Research on Organochlorine Compounds:

From the CHAMACOS Birth Cohort Study –


  • Higher levels of DDT in mother’s blood during pregnancy were associated with:
    • Poorer mental development in their children at age 2. (Go to publication)
    • But not with neonatal neurodevelopment.  (Go to Publication)
    • But not with fetal growth. (Go to publication)


  • Prenatal exposure to PCBs (organochlorine compounds) is associated with:
    • Altered thyroid hormone levels in mothers. (Go to publication)
    • For certain PCBs, prenatal exposure was associated with neonatal thyroid hormone levels. (Go to publication)

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