Background: Dichlorodiphenyldichloroethylene (DDE) and other organochlorines suppress immunity biomarkers in animals and humans. Our aim was to study the association between prenatal levels of DDE and lower respiratory tract infection in infants independently from polychlorinated biphenyls (PCBs) and other organochlorines.
Methods: Maternal levels of p'p'-DDE, dichlorodiphenyltrichloroethane (p'p-DDT), PCB congeners 28, 118, 138, 153, and 180, hexachlorobenzene, and beta-hexachlorocyclohexane were measured in first trimester serum of 584 pregnant women from a general population-based cohort in Sabadell (Catalonia, Spain). Mothers reported lower respiratory tract infection in interviewer-led questionnaires administered at infant age 6 and 14 months.
Results: Thirteen percent of babies had recurrent lower respiratory tract infection during the first 14 months of life. Among the organochlorines, DDE showed the highest levels (median = 112 ng/g lipid); dichlorodiphenyltrichloroethane was not detectable. The median total PCB level was 85 ng/g. DDE was the only organochlorine that showed an association with recurrent lower respiratory tract infection (at levels >83 ng/g, the first tertile, relative risk = 2.40 [95% confidence interval = 1.19-4.83]), lower respiratory tract infection at 6 months (1.68 [1.06-2.66]), and lower respiratory tract infection at 14 months (1.52 [1.05-2.21]). Adjusting for PCBs, hexachlorobenzene or beta-hexachlorocyclohexane did not confound the association.
Conclusions: Immunologic suppression by DDE as observed in experimental studies could explain the relation between DDE and lower respiratory tract infection, independently of PCBs. Exposure to DDE during prenatal life could be critical for the development of the immune and respiratory systems.