Study of Health Effects of DDT in Mexico

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Recent data continue to indicate that use of the insecticide DDT may have adverse effects on human health, but essentially no findings on this topic have been replicated, so the question is still open. Whether DDT has adverse effects is important because DDT is still used for malaria control in about 12 countries, and current recommendations by the World Health Organization that support DDT use are based on the assumption that it has basically no adverse health consequences for humans. DDE is the major metabolite of DDT. Experiments in animals indicate that DDE blocks androgen action and that exposure before birth can have adverse effects on male reproduction. In addition, two previous human studies suggest that higher exposure to DDE is associated with a shortended duration of lactation. Breast feeding prevents infant death. Therefore, DDT use may have the effect of increasing infant death. Furthermore, recent data suggest that DDT/DDE may cause pregnancy loss in humans. Additional information about these potential adverse effect are needed. Mexico used the insecticide DDT for malaria control until 1999; many people there in tropical areas have elevated blood levels of the DDT metabolite, DDE. My project in Mexico has two phases; both are based on the same group of subjects. I conducted phase 1 of this study: 1) To examine the relation between maternal serum levels of DDE in relation to evidence of decreased androgen action in 781 newborn males in Tapachula, Mexico. All phase 1 subjects were enrolled in 2002-2003; the response rate was 95%. Phase 2 of this study began in FY 2004. This study followed 757 women and children enrolled in Phase 1, to determine if DDT exposure is related to reduced length of lactation among mothers. In addition, the offspring were followed to examine early-life DDT exposure in relation to infection and growth. Follow-up was completed last year. Last years progress: For phase 1, two papers were published. Anthropometric measures on infant males were unrelated to DDE levels in the mothers; in the second paper the anthropometric measures were shown to be reliably ascertained. For phase 2, the report on DDE and length of lactation was submitted to a journal, received favorable reviews, and is now being revised for that journal. DDE levels were not related to length of lactation. A manuscript on the reliability of reporting length of lactation has been completed and will be submitted for publication soon. The pre-doctoral student who wrote these two papers will be joining NIEHS as a postdoc in September of 2007, and will continue work on the phase 2 manuscripts and projects.