DDT contamination from indoor residual spraying for malaria control

Abstract

The insecticide DDT is still used in specific areas of South Africa for indoor residual spray (IRS) to control malaria vectors. Local residents could be exposed to residues of DDT through various pathways including indoor air, dust, soil, food and water. The aims of this study were to determine the levels of DDT contamination, as a result of IRS, in representative homesteads, and to evaluate the possible routes of human exposure. Two villages, exposed (DV) and reference (TV) were selected. Sampling was done two months after the IRS process was completed. Twelve homesteads were selected in DV and nine in TV. Human serum, indoor air, floor dust, outside soil, potable water, leafy vegetables, and chicken samples (muscle, fat and liver) were collected and analyzed for both the o,p′- and p,p′-isomers of DDT, DDD and DDE. DDT was detected in all the media analyzed indicating a combination of potential dietary and non-dietary pathways of uptake. DV had the most samples with detectable levels of DDT and its metabolites, and with the exception of chicken muscle samples, DV also had higher mean levels for all the components analyzed compared to TV. Seventy-nine percent of participants from DV had serum levels of DDT (meanΣDDT 7.3 μg g−1 lipid). These residues constituted mainly of p,p′-DDD and p,p′-DDE. ΣDDT levels were detected in all indoor air (mean ΣDDT 3900.0 ng m−3) and floor dust (meanΣDDT 1200.0 μg m−2) samples. Levels were also detected in outside soil (mean ΣDDT 25.0 μg kg−1) and potable water (mean ΣDDT 2.0 μg L−1). Vegetable sample composition (meanΣDDT 43.0 μg kg−1) constituted mainly p,p′-DDT and p,p′-DDD. Chicken samples were highly contaminated with DDT (muscle mean ΣDDT 700.0 μg kg−1, fat mean ΣDDT 240,000.0 μg kg−1, liver mean ΣDDT 1600.0 μg kg−1). The results of the current study raise concerns regarding the potential health effects in residents living in the immediate environment following DDT IRS.