What is DDT?

DDT (dichlorodiphenyltrichloroethane) is a pesticide once widely used to control insects in agriculture and insects that carry diseases. DDT is a white, crystalline solid with no odor or taste. Its use in the U.S. was banned in 1972 because of damage to wildlife, but is still used in some countries, most notably for malaria control.

DDE (dichlorodiphenyldichloroethylene) and DDD (dichlorodiphenyldichloroethane) are chemicals similar to DDT found in small quantities in most DDT products. DDE has no commercial use. DDD was also used to kill pests, but its use has also been banned. One form of DDD has been used medically to treat cancer of the adrenal gland.

What happens to DDT when it enters the environment?

DDT use to enter the environment when it was used as a pesticide. This still occurs due to current use in other countries. DDE and DDD enter the environment as a contaminant or breakdown product of DDT. Once in the environment:

  • DDT, DDE, and DDD in the air are quickly broken down by sunlight. Half of what's in the air breaks down within 2 days.
  • DDT sticks strongly to soil - most DDT in soil is broken down slowly to DDE and DDD by microorganisms. Half the DDT in soil will break down in 2-15 years, depending on the type of soil.
  • Only a small amount of DDT, or its breakdown products, will go through the soil into groundwater - they don't dissolve easily in water.
  • DDT, and especially DDE, builds up in plants and in fatty tissues of fish, birds, and other animals.

How might I be exposed to DDT?

  • Eating contaminated foods, such as root and leafy vegetables, fatty meat, fish, and poultry, but levels are very low.
  • Eating contaminated imported foods from countries that still allow the use of DDT to control pests.
  • Breathing contaminated air or soil particles, swallowing contaminated soil, or drinking contaminated water near waste sites and landfills that may contain higher levels of these chemicals.
  • Infants fed on breast milk from mothers who have been exposed.

How can DDT affect my health?

DDT affects the nervous system. People who have accidentally swallowed large amounts of DDT became excitable and had tremors and seizures. These effects went away after the exposure stopped. No effects were seen in people who took small daily doses of DDT by capsule for 18 months.

A study in humans showed that women who had high amounts of a form of DDE in their breast milk were unable to breast feed their babies for the same length of time as women who had little DDE in the breast milk. Another study in humans showed that women who had high amounts of DDE in breast milk had an increased chance of having premature babies.

In animals, short-term exposure to large amounts of DDT in food affected the nervous system, while long-term exposure to smaller amounts affected the liver. Also in animals, short-term oral exposure to small amounts of DDT or its breakdown products may also have harmful effects on reproduction.

DDT and Cancer

Studies in animals given DDT with food have shown that DDT can cause liver cancer. Studies in DDT-exposed workers did not show increases in cancer. However, it has been determined to be a probable human carcinogen by the Department of Health and Human Services, the International Agency for Research on Cancer, and the Environmental Protection Agency (EPA). The EPA has determined that DDE and DDD are also probable human carcinogens.

How can I reduce the risk of exposure to DDT?

People can be exposed to DDT by eating food or drinking liquids contaminated with small amounts of DDT. Potential exposures can be reduced by: