Dichlorodiphenyldichloroethylene

Dichlorodiphenyldichloroethylene (1,1-bis-(4-chlorophenyl)-2,2-dichloroethene) is the full name of DDE. This compound is formed by the loss of hydrogen chloride (dehydrohalogenation) of DDT (1,1-bis-(4-chlorophenyl)-2,2,2-trichloroethane), of which it is one of the more common breakdown products. DDE is fat soluble which tends to build up in the fat of animals. Due to its stability in fat, DDE is rarely excreted from the body, and body levels tend to increase throughout life. The major exception is the excretion of DDE in breast milk, which delivers a substantial portion of the mother's DDE burden to the young animal.

DDE is reputed to be particularly dangerous, and to have caused massive disruption and decrease in eagle populations, notably in North America. It is believed that DDE prevents efficient calcium fixation in eggshells. As such, the birds would crush their eggs instead of incubating them, due to the latters' lack of resistance.

Despite downward trends in DDE, eggshell thicknesses have not rebounded to pre-DDT levels. Some experts dispute the relationship between DDE and eggshell thickness and point to studies showing that the thinnest eggshells in the years sampled by the studies were lain by the control group. Other studies have pointed out potential dangers in measuring eggshell thicknesses due to the thickness varying depending on egg topography and are unable to draw firm conclusions.

Some studies have indicated that DDE is an endocrine disruptor and contributes to breast cancer, but more recent studies provide strong evidence that there is no relationship between DDE exposure and breast cancer. What is more clear is that DDE is a weak antiandrogen.

While widely publicized, DDE's effects on eggshell thinning represent the tip of the iceberg for DDE's toxicity. There is substantial and growing evidence showing that DDE is a potent endocrine disruptor and xenoestrogen. Our Stolen Future, the watershed book on endocrine disruptors, chronicles Theo Colborn's development of the hypothesis as she waded through thousands of studies on toxins, many on DDE.