DDE, a Degradation Product of DDT, and Duration of Lactation in a Highly Exposed Area of Mexico

BACKGROUND: Higher levels of 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE), the major degradation product of 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT), have been related to shorter duration of breast-feeding in previous studies. If DDE truly shortens lactation, this has public health importance regarding infant mortality and the use of DDT for malaria control. OBJECTIVE: Our aim was to assess the relationship of maternal DDE concentrations with length of subsequent lactation. METHODS: We conducted a relatively large study in a highly exposed area of Mexico. We followed 784 mother–son pairs to determine length of lactation. DDE and DDT were measured in maternal serum obtained within a day of delivery. We fit proportional hazard models with and without stratifying by previous breast-feeding, because an association of DDE with duration of lactation among those who breast-fed previously could be attributed to a noncausal mechanism. RESULTS: Compared with those with DDE concentrations ≤ 3.00 μg/g, the adjusted hazard ratios of weaning according to DDE category were, for concentrations 3.01–6.00 μg/g, 1.27 [95% confidence interval (CI), 1.04–1.55]; for concentrations 6.01–9.00 μg/g, 1.23 (95% CI, 0.92–1.63); and for concentrations > 9.00 μg/g, 1.17 (95% CI, 0.92–1.49). The corresponding ratios for women who previously breast-fed were 1.40 (95% CI, 1.06–1.87); 1.91 (95% CI, 1.24–2.93); and 1.76 (95% CI, 1.22–2.53). Those for women who had not breast-fed previously were 1.14 (95% CI, 0.86–1.52); 0.90 (95% CI, 0.61–1.31); and 0.91 (95% CI, 0.66–1.26). CONCLUSIONS: Data from our relatively large study in a highly exposed area of Mexico did not support the hypothesis that exposure to DDE shortens length of lactation. The association seen in women who previously breast-fed was likely attributed to a noncausal mechanism. Nonetheless, whether DDT has other important adverse effects on humans is still an open question.