Bioaccumulation of DDT Residues in Human Serum: an Historical Use of DDT Indoor Residual Spraying in Malaria Endemic Regions of Thailand

Abstract

In Thailand, DDT indoor residual spraying (IRS) was used to interrupt malaria transmission until it was phased out between 1995 and 1999. However, contamination by DDT and its primary metabolite, p,p'-DDE remains a serious environmental and human health concern. We investigated serum concentrations of p,p'-DDE and p,p'-DDT in Southern Thai residents living in malaria-endemic areas where IRS with DDT was applied. Levels of p,p-DDE and p,p'-DDT were measured in plasma serum of 346 participants (205 females, 141 males) from Southern provinces of Thailand and from Bangkok. Serum concentrations of measured compounds were significantly higher in Southern Thai residents than general population (in Bangkok) (P < 0.001). The highest geometric mean value of p,p'-DDE was 6,531 (95% CI=4,083-8,979) and 5,053 (95% CI=2,909-7,197) ng/g lipids in female and male subjects, respectively. Even though, DDT ultimately is banned for all uses, the concentration of the daughter compound p,p'-DDE was much higher in Southern subjects than in the general population. A high ratio of p,p'-DDE/p,p'-DDT indicates that the exposure is due to past rather than recent use of DDT