Background: Pyrethroids are the most widely used insecticides globally for domestic, agricultural, and malaria vector control. In 10 countries, dichlorodiphenyl trichloroethane (DDT) is also used for the latter. Thus, high exposure to pyrethroids and DDT have been reported among women and children from rural and/or malaria-endemic areas. Experimental studies suggest that fetal exposure to pyrethroids, particularly cypermethrin, and DDT may have sex-specific growth effects. However, epidemiologic investigations are scarce and inconsistent and have not considered postnatal environment or susceptibility factors.
Methods: In 665 mother-child dyads participating in the Venda Health Examination of Mothers, Babies, and their Environment (VHEMBE), a rural South African birth cohort with high insecticide exposure, we examined associations of maternal peripartum uri-nary pyrethroid metabolites and serum DDT concentrations with child anthropometrics at 3.5 years using multivariable linear regression. We investigated effect modification by child sex, maternal nutrition and HIV status, and household poverty.
Results: Pyrethroid metabolites cis-3-(2,2-dibromovinyl)-2,2-dimethyl-cyclopropane carboxylic acid (cis-DBCA), cis-3-(2,2,-dicholorvinyl)-2,2-dimethyl-cyclopropane carboxylic acid (cis-DCCA), trans-DCCA, and 3-phenoxybenzoic acid (3-PBA) were quantified in nearly all mothers. A 10-fold increase in cis-DCCA concentration was associated with 0.21 kg/m2 lower body mass index (95% confidence interval = -0.41, -0.01), with similar estimates for other cypermethrin or permethrin metabolites (trans-DCCA and 3-phenoxybenzoic acid). In stratified analyses, stronger associations were observed with lower weight, body mass index, arm circumference, and weight-for-height among boys relative to girls. Associations with cis-3-(2,2-dibromovinyl)-2,2-dimethyl-cyclopropane carboxylic acid, a metabolite specific to deltamethrin, were weaker or absent. No substantial associations were observed with DDT.
Discussion: In a population with ubiquitous pyrethroid exposure, maternal concentrations of metabolites of cypermethrin and permethrin were associated with thinness at 3.5 years.
Keywords: Child growth; Cypermethrin; DDT/E; Pyrethroid.