DDT and DDE: Second Generation Time to Pregnancy Effects

Barbara A. Cohn, Ph.D., MPH, MCP
Public Health Institute, Berkeley, California
R01ES08345

Background:DDT was originally prepared in 1873, but it was not until 1939 that Paul Muller discovered the effectiveness of DDT as an insecticide. He was awarded the Nobel Prize in medicine and physiology in 1948 for this discovery.

The use of DDT increased enormously worldwide after World War II, primarily because of its effectiveness against the mosquito and lice. The World Health Organization estimates that during the period of its use approximately 25 million lives were saved predominantly from malaria and typhus. However, many species of insects developed resistance to DDT; it proved to have a high toxicity toward fish; and it was responsible for the near extinction of several bird species because of its interference with the formation of egg shells. For these reasons and because of its environmental persistence, the use of DDT was banned in the United States in 1972. However, It is still in use in some other parts of the world.

In mammals, DDT is of relatively low toxicity, but it does have troubling effects. DDT and its major metabolite, known as DDE, are persistent and are stored in fat tissue. DDT is know to have weak estrogenic activity and DDE has considerable anti-androgenic activity. They cross the placenta potentially interfering with fetal development. To further investigate possible effects on the human reproductive system, this team of investigators measured DDT and DDE levels in maternal serum samples collected from 1960-1963 in the Child Health and Development Studies. They compared these levels to the time to pregnancy in 289 daughters around 30 years later.

Advance: This is the first report to link DDT exposure in early life to human reproductive problems 30 years later. There was a clear association between increased DDT concentrations in maternal blood with a decreased chance of pregnancy in the daughters. For every 10 mg/L of DDT in maternal serum, the probability of pregnancy dropped 32%. However, quite unexpectedly, the chance of pregnancy increased 16% with each increase of 10 mg/L of DDE. The opposing effects of DDT and DDE may explain why large changes in reproductive performance have not been noticed in humans since the introduction of DDT.

Implication: Although the decreased fertility associated with in utero exposure to DDT remains unexplained, the authors speculate that the "antiandrogenic effects of DDE may mitigate harmful androgenic effects on the ovary during gestation and early life." This study demonstrates the long delay from exposure to noticeable effect. The findings support both the establishment of new long-term human studies that can monitor effects of environmental exposures on reproduction as well as continued support of existing studies where multigenerational follow-up is in progress.

Citation: Cohn BA, Cirillo PM, Wolff MS, Schwingl PJ, Cohen RD, Sholtz RI, Ferrara A, Christianson RE, van den Berg BJ, Siiteri PK. DDT and DDE exposure in mothers and time to pregnancy in daughters. Lancet. 2003 Jun 28;361(9376):2205-6.