Drinking-water exposure to a mixture of nitrate and low-dose atrazine metabolites and small-for-gestational age (SGA) babies: A historic cohort study

BackgroundGroundwater, surface water and drinking water are contaminated by nitrates and atrazine, an herbicide. They are present as a mixture in drinking water and with their endocrine-disrupting activity, they may alter fetal growth.ObjectivesTo study an association between drinking-water atrazine metabolites/nitrate mixture exposure and small-for-gestational-age (SGA).MethodsA historic cohort study based on birth records and drinking-water nitrate and pesticide measurements in Deux-Sèvres (France) between 2005 and 2009 was carried out. Exposure to drinking-water atrazine metabolites/nitrate mixture was divided into 6 classes according to the presence or absence of atrazine metabolites and to terciles of nitrate concentrations in each trimester of pregnancy. Regression analysis of SGA by mixture exposure at second trimester was subsequently conducted.ResultsWe included 11,446 woman-neonate couples of whom 37.0% were exposed to pesticides, while 99.9% of the women were exposed to nitrates. Average nitrate concentration was from 0 to 63.30 mg/L. In the second trimester of pregnancy, the risk of SGA was different with mixture exposure when drinking-water atrazine metabolites, mainly 2hydroxyatrazine and desethylatrazine, were present and nitrate dose exposure increased: compared to single first tercile of nitrate concentration exposure, single second tercile exposure OR was 1.74 CI 95% [1.10; 2.75] and atrazine metabolites presence in the third tercile of nitrate concentration exposure OR was 0.87 CI 95% [0.45; 1.67].ConclusionsIt is possible that the association found at the second trimester of exposure with regard to birth weight may likewise be observed before birth, with regard to the estimated fetal weight, and that it might change in the event that the atrazine metabolites dose were higher or the nitrate dose lower. It would appear necessary to further explore the variability of effects.

► Risk of SGA differed when water atrazine metabolites/nitrate mixture exposure increased.
► Dose exposure modify the SGA and atrazine metabolites/nitrate mixture association.
► Window time exposure modify the SGA and atrazine metabolites/nitrate mixture association.
► Drinking-water atrazine metabolites/nitrate mixture exposure: a synergistic effect on SGA?.