Maternal Exposure to Disinfection By-Products and Risk of Hypospadias in the National Birth Defects Prevention Study (2000-2005).

Ibrahim Zaganjor,Lawrence Engel,Paul Romitti,Tania Desrosiers,Adrian Michalski,Andrew Olshan,Wendy Nembhard,Thomas Luben,Marcia Feldkamp,Peter Langlois,Mahsa Yazdy,Suzan Carmichael,Alexander Keil,Jennita Reefhuis,Gary Shaw

doi:10.3390/ijerph17249564

Abstract

The purpose of this study was to estimate the association between 2nd and 3rd degree hypospadias and maternal exposure to disinfection by-products (DBPs) using data from a large case-control study in the United States. Concentration estimates for total trihalomethanes (TTHMs), the sum of the five most prevalent haloacetic acids (HAA5), and individual species of each were integrated with data on maternal behaviors related to water-use from the National Birth Defects Prevention Study (NBDPS) to create three different exposure metrics: (1) household DBP concentrations; (2) estimates of DBP ingestion; (3) predicted uptake (i.e., internal dose) of trihalomethanes (THMs) via ingestion, showering, and bathing. The distribution of DBP exposure was categorized as follows: (Q1/referent) < 50%; (Q2) ≥ 50% to < 75%; and (Q3) ≥ 75%. Logistic regression was used to estimate adjusted odds ratios (aORs) and 95% confidence intervals (CIs). Generally, null associations were observed with increasing TTHM or HAA5 exposure. An increased risk was observed among women with household bromodichloromethane levels in the second quantile (aOR: 1.8; 95% CI: 1.2, 2.7); however, this association did not persist after the inclusion of individual-level water-use data. Findings from the present study do not support the hypothesis that maternal DBP exposures are related to the occurrence of hypospadias.

Highlights

Hypospadias is a structural birth defect of the male urethra that occurs when the urethra is located below its normal location
After excluding women who drank well water (n = 253) and women missing disinfection by-products (DBPs) concentrations (n = 1399), a total of 1247 women (330 cases; 917 controls) remained in our primary analytic sample to evaluate the association between household DBP concentrations and hypospadias (Figure 1)
By combining data from public water systems (PWSs) and maternal water-use information from the National Birth Defects Prevention Study (NBDPS) maternal interview, we were able to estimate the association between DBPs and hypospadias using various metrics

Summary

Introduction

Hypospadias is a structural birth defect of the male urethra that occurs when the urethra is located below its normal location (i.e., tip of the penis). It is a common birth defect in the United States with an estimated prevalence of 64.7 cases per 10,000 male live births [1]. This birth defect has a genetic component [2], the majority of hypospadias cases are still considered to be idiopathic [3]. Two of the most common DBPs in chlorinated water sources, trihalomethanes (THMs) and haloacetic acids (HAAs), are currently regulated by the United States Environmental Protection Agency (USEPA). The epidemiologic literature remains equivocal [11,12,13,14]

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