Chronic adverse effects of long-term exposure of children to dichlorodiphenyltrichloroethane (DDT) through indoor residual spraying: a systematic review

摘要

Introduction:Malaria remains a significant public health problem in endemic regions of the world, most especially in sub-Saharan Africa. As part of the global efforts to control malaria, dichlorodiphenyltrichloroethane (DDT), a cheap and effective chemical, was endorsed by the World Health Organization for use in indoor residual spraying (IRS). However, in the light of evidence on the acute toxicity of DDT, concerns have grown about the safety or the possible chronic health effects from the continued use of this persistent chemical, generating much debate and research efforts over the years. The purpose of this study was to identify, appraise and synthesise evidence about the chronic adverse effects of long-term exposure to DDT in children, 0-18?years, in zones where IRS is practised, in order to contribute to informing policy decisions.Methods:Twenty-seven electronic databases were systematically searched using pre-defined inclusion/exclusion criteria. Two were trial registers while 25?others indexed studies of various designs. Other complementary methods were also employed in searching for both published and grey literature. Eligible studies were critically appraised using amended versions of available validated guidelines (and in a case, an improvised guideline) and a narrative synthesis was undertaken.Results:Only nine studies met the inclusion/exclusion criteria out of 3281?hits generated. Five of the studies are of high quality while four are of moderate quality. For the three studies on neurodevelopment, evidence suggestive of negative impact of DDT was found. For the three studies on endocrine/congenital disorders, ambivalent evidence existed. In the case of the immunity-related outcome, there was growing but insufficient evidence of negative effect. The only study on survival outcome was inconclusive.Conclusions:Empirically, insufficient evidence exists with regard to the chronic adverse effects of long-term exposure of children to DDT through IRS. Considering the dearth of studies and the fact that many adverse effects might take much longer time to manifest, inferences drawn are weak. It would therefore require a series of well-coordinated observational studies done in the context of IRS to adequately address this evidence gap in the future.