such as "Introduction", "Conclusion"..etc
DDT was banned from use in the USA three decades ago after its toxic effects on environment, animal and human health (via the food chain) were identified. DDT is still used in some less-developed countries, notably in areas where it effectively reduces the transmission of malaria by its toxic effects on mosquitoes.
Barbara A Cohn from the Public Health Institute, Berkeley, USA, and colleagues measured concentrations of DDT and DDE in the preserved blood of women who gave birth in California in the early 1960s. They compared maternal DDT and DDE blood concentrations with the time to pregnancy in 289 daughters around 30 years later.
The investigators found a clear association between increased DDT concentrations in maternal blood and a decreased chance of pregnancy in their daughters; around one- third reduction in chance of pregnancy for every 10 microgrammes per litre increase in DDT concentrations of maternal blood. Unexpectedly, the chance of a daughter's pregnancy increased by one- sixth per 10 microgrammes per litre increase of DDE concentrations in maternal blood. The investigators comment that the opposite effects of DDE and DDT might explain why large changes in human reproductive performance have not been observed after DDT was introduced worldwide.
Barbara Cohn comments: "While it is reassuring that possible harmful effects of DDT may be reduced by its conversion to DDE, women still experienced delays in becoming pregnant. Our findings could eventually lead to new understanding about the causes and prevention of sub-fertility."
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