Most significant pathway [1]

After DDT is taken up by an oranism, one of four things can happen to it.

• It can be metabolized to a less toxic substance, such as DDE:

This process occurs at different rates in different organisms, depending on the amount and quality of the enzyme DDT dehydrochlorinase, which is responsible for this reaction. Insect resistance to DDT has been blamed on the selection of insects with higher levels of this enzymer or mutant versions of it, which are able to process DDT faster.

• It can be excreted
• It can be stored in fatty tissues. In this case, it is not very toxic until the fat is metabolized for energy.
• It can reach nerve cells harm them - see Methods of Action in Insects

Other Pathways [1]

These other metabolites of DDT are produced to a lesser extent than DDE. TDE is also an insecticide, although a weaker one than DDT.

In the Environment

DDT has a half-life of 26 days in river water and 15 years in soils. In soils, it is broken down by both aerobic anaerobic bacteria to DDE and DDD [2]. Because of its stability in animal tissue and in soils, DDT bioaccumulates in the environment. DDT is found in higher and higher concentrations as you move up the food chain. This has led to problems of toxic levels of DDT in top-of-the-chain predators, such as eagles and falcons (see Methods of Action in Birds). Below is an illustration of DDT bioaccumulation.

[1] Mellanby, K. 1992. "The DDT Story." Surrey, UK: Unwin Brothers Limited.

[2] Wikipedia online; www.en.wikipedia.org

[3] "Biomagnification: how DDT becomes concentrated as it passes through a food chain." http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/D/DDTandTrophicLevels.html.