DDT contamination from indoor residual spraying for malaria control

Abstract

a b s t r a c t a r t i c l e i n f oThe 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 (mean ∑DDT 7.3 μg g −1 lipid). These residues constituted mainly of p,p′-DDD and p,p′-DDE. ∑DDT levels were detected in all indoor air (mean ∑DDT 3900.0 ng m − 3 ) and floor dust (mean ∑DDT 1200.0 μg m − 2 ) samples. Levels were also detected in outside soil (mean ∑DDT 25.0 μg kg − 1 ) and potable water (mean ∑DDT 2.0 μg L − 1 ). Vegetable sample composition (mean ∑DDT 43.0 μg kg − 1 ) constituted mainly p,p′-DDT and p,p′-DDD. Chicken samples were highly contaminated with DDT (muscle mean ∑DDT 700.0 μg kg − 1 , fat mean ∑DDT 240,000.0 μg kg − 1 , liver mean ∑DDT 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.

Estimation of human body concentrations of DDT from indoor residual spraying for malaria control

“…ΣDDT and ΣDDE concentrations in indoor air were measured after IRS interventions in South Africa van Dyk et al, 2010); total DDT could still be detected after 84 days. During this period the total DDT 5 concentration decreased quickly from 16.5μg/m 3 initially to 3.4μg/m 3 van Dyk et al, 2010).…”

“…Because individuals living in malaria-endemic regions in South Africa have experienced DDT exposure from annually performed IRS for more than 60 years (Bornman et al, 2010), we assumed that different generations experience identical exposure patterns. That is, a first-born mother would show the same DDT concentration profile as her first-born child, assuming that factors such as the mother's age at delivery and the duration of breastfeeding remained the same (Quinn et al, 2011).…”

“…The following age groups were used: 0.5-3 years, 4-6 years, 7-10 years, and >10 years. ΣDDT and ΣDDE concentrations in chicken muscle and leafy vegetables were obtained from van Dyk et al (2010), the concentrations in fish fat from Barnhoorn et al (2009). For concentrations of ΣDDT and ΣDDE in chicken fat, a high variability is present in the data reported by van Dyk et al The concentrations in chicken eggs were taken from recent measurements (Bornman, unpublished data).…”

“…Recent studies from South Africa found reduced retinol-binding protein and thyroid hormone concentration, urogenital malformations in newborn boys, and impaired semen quality, associated with non-occupational exposure to DDT (Aneck-Hahn et al, 2007;Bornman et al, 2010;Delport et al, 2011).…”

Implications for health education and intervention strategies arising from children's caregivers concerns following successful malaria control

“…Formal employment opportunities are few, and many are subsistence farmers. [16][17][18] Based on aerial photographs, random starting points for systematic homestead sampling were identified. Because the villages are informally planned and homesteads are often without clear site boundaries, it was impossible to derive a precise number of homesteads for each village.…”