Association between exposure to p,p′-DDT and its metabolite p,p′-DDE with obesity: Integrated systematic review and meta-analysis

BACKGROUND: The prevalence of obesity is increasing in all countries, becoming a substantial public health concern worldwide. Increasing evidence has associated obesity with persistent pollutants such as the pesticide DDT and its metabolite p,p′ -DDE. OBJECTIVES: Our objective was to systematically review the literature on the association between exposure to the pesticide DDT and its metabolites and obesity to develop hazard identification conclusions. METHODS: We applied a systematic review-based strategy to identify and integrate evidence from epidemiological, in vivo, and in vitro studies. The evidence from prospective epidemiological studies was quantitatively synthesized by meta-analysis. We rated the body of evidence and integrated the streams of evidence to systematically develop hazard identification conclusions. RESULTS: We identified seven epidemiological studies reporting prospective associations between exposure to p,p′ -DDE and adiposity assessed by body mass index (BMI) z-score. The results from the meta-analysis revealed positive associations between exposure to p,p′ -DDE and BMI z-score (β =0:13 BMI z-score (95% CI: 0.01, 0.25) per log increase of p,p′ -DDE). Two studies constituted the primary in vivo evidence. Both studies reported positive associations between exposure to p,p′ -DDT and increased adiposity in rodents. We identified 19 in vivo studies and 7 in vitro studies that supported the biological plausibility of the obesogenic effects of p,p′ -DDT and p,p′ -DDE. CONCLUSIONS: We classified p,p′ -DDT and p,p′ -DDE as “presumed” to be obesogenic for humans, based on a moderate level of primary human evidence, a moderate level of primary in vivo evidence, and a moderate level of supporting evidence from in vivo and in vitro studies.