DDT

DDT (dichlorodiphenyltrichloroethane) is a toxic and persistent organochlorine used as an insecticide. It is a white, crystalline solid with no odor or taste. DDT was banned in the U.S. in 1972, but - contrary to oft-repeated misinformation - it is still used in some countries.

In the Environment
DDT still enters the environment when it is used in countries outside of the United States. Once in the environment, DDT in the air is rapidly broken down by sunlight. Half of the DDT in the air breaks down within two days. DDT sticks to the soil, and there it is broken down slowly into DDE and DDD by microorganisms. It takes 2-15 years for half of the DDT in the soil to break down, depending on the type of soil. DDT and its breakdown products DDD and DDE do not dissolve eaisly in water, so very little goes through the soil into groundwater. DDT (and especially DDE) builds up in plants and in the fatty tissues of fish, birds, and other animals.

In Sewage Sludge
A study in Australia found several banned organochlorine pesticides (aldrin, chlordane, dieldrin, heptachlor, hexachlorbenzene, and DDT) in sewage sludge. Researchers found that in some cases, it takes as long as 15 years after the pesticides were banned for their levels in sewage sludge to drop below detectable levels.

Human Exposure
Humans are exposed to DDT and its breakdown products DDD and DDE by eating contaminated foods, including root and leafy vegetables, fatty meat, fish, and poultry. This is particularly true of contaminated food imported from countries that still allow the use of DDT. Humans may also be exposed by breathing contaminated air, drinking contaminated water, or breathing or swallowing soil particles near waste sites and landfills that contain these chemicals. Infants may be exposed by drinking breast milk from mothers who have been exposed to DDT and its breakdown products.

Human Health Effects
According to the CDC's Agency for Toxic Substances & Disease Registry:

"DDT affects the nervous system. People who 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 as long 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, DDE, and DDD are probably human carcinogens. Studies in rats also show that DDT and DDE appear to be endocrine disruptors.

Federal Regulations
Workplace Air: OSHA sets a limit of 1 milligram of DDT per cubic meter of air (1 mg/m3) in the workplace for an 8-hour shift, 40 hour work week.

Food: The FDA sets limits for the amounts of DDT, DDE, and DDD in food.

Books

 * David Kinkela, DDT and the American Century: Global Health, Environmental Politics, and the Pesticide That Changed the World (Chapel Hill: University of North Carolina Press, 2011). Review

Related SourceWatch articles

 * Biosolids
 * Sewage sludge
 * Food Rights Network
 * Malaria and DDT

External resources
Pesticide Action Network Pesticide Database: DDT