Introduction: DDT has been widely used in agriculture and to control disease-bearing vectors since the 1940s. Recognition of DDT's negative impact on wildlife led many countries to ban its use starting in the 1970s, including the US in 1972 and Mexico in 2000. DDT is one of 12 persistent organic pollutants targeted by the Stockholm Convention on Persistent Organic Pollutants. Despite these restrictions on use, human exposure to DDT continues due to its environmental persistence, bio-accumulation in plants and animal fat, and continued use in malaria-endemic areas. The Center for Children's Environmental Health Research is investigating population-level correlates of exposure to DDT and DDE in 426 pregnant women from low-income Latino families living in the Salinas Valley, an agricultural area in Monterey County, California. These women are participants of the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) study, a longitudinal birth cohort study of environmental exposures and children's health. Methods: We measured DDT and DDE in serum collected from 394 pregnant women at 26 weeks gestation and from 34 women at time of delivery. Data on socio-demographic characteristics, occupation, length of time in the US, and reproductive and breast feeding history were collected through questionnaire. Levels of DDT and DDT metabolites were quantified in serum by gas chromatography high-resolution mass spectrometry. Results: All results are lipid-adjusted and expressed as nanograms/gram of lipid. p'p-DDT and p'p-DDE were detected in 426 samples (100%) and o'p-DDT in 424 samples (99.5%). The geometric means (95% CI) of p'p-DDE; p'p-DDT, and o'p-DDT were 1,052 (1,233-1,572); 21 (18-25), and 2 (1-2), respectively. These levels are approximately 3 times US national reference levels, reported by CDC. Women born in the US had lower geometric mean (GM) levels of p'p-DDE (573) than women born in Mexico or Latin America (1,573) (ANOVA p-value <0.001). In women who were not born in the US, levels of p'p-DDE were inversely associated with length of residence in the US: gm=1,643 for 0-1 years; 1,651 for 2-5 years; 1,447 for 6-10 years; and 1,242 for 11-35 years (p-value <0.001). Lastly, levels of p'p-DDE were associated with malaria risk in the state in Mexico where a participant was born. The GM of p'p-DDE was 936 among women born in a state with no malaria risk, 1,504 among women born in a state with some malaria risk, and 2,632 among women born in a state with high malaria risk (p-value <0.001). Trends for p'p-DDT and o'p-DDT were similar. Conclusion: The high body burdens of DDT and DDT metabolites in the CHAMACOS population can be explained by birth in a malaria-endemic area of Mexico and length of time in the US.
Pesticides; Pregnancy; Children; Prenatal-exposure; Risk-factors; Risk-analysis; Exposure-levels; Exposure-assessment; Pesticides-and-agricultural-chemicals; Biological-monitoring; Pregnancy; Health-hazards; Health-surveys; Blood-analysis; Blood-sampling; Urine-chemistry; Statistical-analysis; Epidemiology; Demographic-characteristics; Reproductive-effects; Teratology