Malaria vector control and occurrence, levels and dynamics of DDT in breast milk in certain rural areas of KwaZulu
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The WHO considers DDT as safe to man and environment when applied intra-domiciliary for malaria control. Research into the possible health effects under prevailing conditions, taking social customs into account, have, however, been lacking. This project was undertaken to determine the levels and possible risk of DDT to the health of lactating mothers and their infants. The aims of the study were: To determine the levels of DDT and its metabolites (DDD and DDE) in the breast milk of mothers from a sprayed and a non-sprayed area, as well as determining changes caused by indoor application of DDT. To determine the uptake of DDT and its metabolites by the infant via breast milk, and to develop a statistical model that describes the dynamics. To determine the risk to the health of the mother and infant that can be ascribed to exposure to DDT and its metabolites. The experimental design and methods were approved by the Ethics Committee of the Research Institute for Diseases in a Tropical Environment. Lactating mothers visiting the Mseleni (test group) and Murchison Hospitals (control group) were asked to donate milk on several occasions throughout 1986/7. Blood was also taken from 23 infants from the test group. These samples were extracted according to procedures developed for this study and analyzed using gas-chromatography. DDT was found in all samples from the test group and most of the control group. The mean level of DDT (total DDT) in the breast milk of the test group was 15.83 mg 1 -1 (milk fat), significantly higher (p < 0.05) than the 0,69 mg 1-1 PDDT (milk fat) for the control group. This was also the case for DDE, DDD and percentage DDT. Serial changes in levels of DDT were found in the breast milk of the exposed group, but was not considered as clinically significant. No significant changes were observed for the control group. The levels in breast milk were not considered as posing a risk to the health of the mothers. The ZDDT level in the milk of the exposed group exceeded the ADI for the infants. The blood levels of the infants was successfully modelled and it was found that parity of the mother and the age of the infant were major factors. Percentage DDT increased significantly (p < 0,05) with an increase in parity. Evidence exists in the literature indicating that immunologic, neurologic and other systems of the infant exposed to high levels via breast milk, may be affected. It was especially a report that correlated an increasing percentage of infants with hypo-reflexia with an increase in levels of DDE in breast milk (Rogan et al., 1986b: lower than the mean ZDDT determined in the present study), that presented evidence of possible neurological involvement. Determining these sub-lethal effects in infants was identified as a priority for further research.