Abstract
BackgroundHypospadias is a relatively common birth defect affecting the male urinary tract. It has been suggested that exposure to endocrine disrupting chemicals might increase the risk of hypospadias by interrupting normal urethral development.MethodsUsing data from the National Birth Defects Prevention Study, a population-based case-control study, we considered the role of maternal exposure to atrazine, a widely used herbicide and potential endocrine disruptor, via drinking water in the etiology of 2nd and 3rd degree hypospadias. We used data on 343 hypospadias cases and 1,422 male controls in North Carolina, Arkansas, Iowa, and Texas from 1998–2005. Using catchment level stream and groundwater contaminant models from the US Geological Survey, we estimated atrazine concentrations in public water supplies and in private wells. We assigned case and control mothers to public water supplies based on geocoded maternal address during the critical window of exposure for hypospadias (i.e., gestational weeks 6–16). Using maternal questionnaire data about water consumption and drinking water, we estimated a surrogate for total maternal consumption of atrazine via drinking water. We then included additional maternal covariates, including age, race/ethnicity, parity, and plurality, in logistic regression analyses to consider an association between atrazine and hypospadias.ResultsWhen controlling for maternal characteristics, any association between hypospadias and daily maternal atrazine exposure during the critical window of genitourinary development was found to be weak or null (odds ratio for atrazine in drinking water = 1. 00, 95 % CI = 0.97 to 1.03 per 0.04 μg/day increase; odds ratio for maternal consumption = 1.02, 95 % CI = 0.99 to 1.05; per 0.05 μg/day increase).ConclusionsWhile the association that we observed was weak, our results suggest that additional research into a possible association between atrazine and hypospadias occurrence, using a more sensitive exposure metric, would be useful.Electronic supplementary materialThe online version of this article (doi:10.1186/s12940-016-0161-9) contains supplementary material, which is available to authorized users.
Highlights
Hypospadias is a relatively common birth defect affecting the male urinary tract
It has been suggested that atrazine may affect aromatase levels, and by extension alter testosterone metabolism and sexual differentiation in frogs [4, 5], and there is experimental evidence to support a link between atrazine and genitourinary malformations in both rats [6] and amphibians [4, 5, 7, 8]
They found some evidence of an increased risk of second or third degree hypospadias for mothers in the 25th–75th percentiles of exposure and for the 75th–90th percentiles of exposure, but suggested that further research was needed to confirm the mechanism for an association between hypospadias and county level atrazine use [12]
Summary
Hypospadias is a relatively common birth defect affecting the male urinary tract. It has been suggested that exposure to endocrine disrupting chemicals might increase the risk of hypospadias by interrupting normal urethral development. It has been suggested that atrazine may affect aromatase levels, and by extension alter testosterone metabolism and sexual differentiation in frogs [4, 5], and there is experimental evidence to support a link between atrazine and genitourinary malformations in both rats [6] and amphibians [4, 5, 7, 8] These effects in animals may be analogous to some of the key events that could lead to hypospadias in a developing fetus, providing biological plausibility for an association between exposure to atrazine and hypospadias.
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