DDT molecule. Computer model of a molecule of the pesticide DDT (dichlorodiphenyltrichloroethane, C14. H9. Cl5). Atoms (spheres) are colour-coded: carbon (red), hydrogen (white), chlorine (blue). DDT attacks the central nervous system of insects. A synthetic pesticide, used since 1939, DDT and its products pollute the environment, taking decades to be broken down. It has been found to accumulate in animal fatty tissues, and so reach dangerous levels in the food chain. Although DDT use was banned in many countries in the 1970s, it is cheap to make and is still used in developing countries.