Contamination of the environment with DDT is connected with its use as a pesticide and/or used to control vectorborne diseases, DDE and DDD enters the environment as contaminant and/or breakdown product of DDT.
DDT is very adhesive to soil, where most of it is broken down slowly to DDE and DDD by microorganisms. DDT is a persistent organic pollutant and depending on the type of soil, its half life is between 215 years. The length of time that DDT will last in soil also depends on temperature and the soil moisture. DDT lasts for a much shorter time in the tropics where the chemical evaporates faster and where microorganisms degrade it faster. DDT disappears faster when the soil is flooded or wet than when it is dry. It disappears faster when initially enters the soil. Later on, evaporation slows down and some of DDT moves into soil microspaces where microorganisms cannot reach the DDT to break it down efficiently.
Taking into account theoretical value of half life as a 15 years time, and 100 kg of DDT used in an area, after 100 years, there will still be almost 1 kg of DDT left in the environment and it will break down as follows:
|Amount Remaining [kg]||100||50||25||12.5||6.25||3.13||1.56||0.78||0.39|
With regard to the adhesive properties of DDT, only a small amount of it will go through the soil into groundwater. Some soil particles with attached DDT and DDT derivatives may get into rivers and lakes in runoff. In lake water DDTs half life is 56 days and approximately 28 days in river water. The half life of DDT and its metabolites in the atmosphere as vapors has been calculated to be approximately 1,53 days.
The most possible way of being exposed to DDT and its metabolites is by eating contaminated foods often imported from countries that still allow the use of DDT to control pests, breathing contaminated air or drinking contaminated water near waste sites and landfills that may contain higher levels of these chemicals, breathing or swallowing soil particles near waste sites or landfills that contain these chemicals. Infants fed on breast milk from mothers who have been exposed.