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Is maternal employment site a source of exposure misclassification in studies of environmental exposures and birth outcomes? A simulation-based bias analysis of haloacetic acids in tap water and hypospadias.

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Background:  In population research, exposure to environmental contaminants is often indirectly assessed by linking residence to geocoded databases of environmental exposures. We explored the potential for misclassification of residence-based environmental exposure as a result of not accounting for the workplace environments of employed pregnant women using data from a National Birth Defects Prevention Study (NBDPS) analysis of drinking water haloacetic acids and hypospadias.  Methods: The original analysis used NBDPS data from women with haloacetic acid exposure information in eight states who delivered an infant with second- or third-degree hypospadias (cases) or a male infant without a birth defect (controls) between 2000 and 2005. In this bias analysis, we used a uniform distribution to randomly select 11%–14% of employed women that were assumed to change municipal water systems between home and work and imputed new contaminant exposures for tap water beverages consumed at work among the selected women using resampled values from the control population. Multivariable logistic regression was used to estimate the association between hypospadias and haloacetic acid ingestion with the same covariates and exposure cut-points as the original study. We repeated this process across 10,000 iterations and then completed a sensitivity analysis of an additional 10,000 iterations where we expanded the uniform distribution (i.e., 0%, 28%).  Results: In both simulations, the average results of the 10,000 iterations were nearly identical to those of the initial study.  Conclusions: Our results suggest that household estimates may be sufficient proxies for worksite exposures to haloacetic acids in tap water.

Impact/Purpose

While employed women may spend a considerable portion of the day at their workplace, where exposure levels may be different than those at home, maternal residence is commonly used exclusively to estimate exposure to potential geospatial hazards in epidemiologic studies of perinatal outcomes and environmental exposures. Although we do not know if our results would be consistent under different scenarios (e.g., different environmental contaminants, exposure window, reproductive outcome, etc.), our quantitative bias analysis results suggested that household estimates may be sufficient proxies for worksite exposures to DBPs in tap water. 

Citation

Zaganjor, I., A. Keil, Tom Luben, T. Desrosiers, L. Engel, J. Reefhuis, A. Michalski, P. Langlois, A. Olshan, AND National Birth Defects Prevention Study. Is maternal employment site a source of exposure misclassification in studies of environmental exposures and birth outcomes? A simulation-based bias analysis of haloacetic acids in tap water and hypospadias. Wolters Kluwer, Alphen aan den Rijn, NETHERLANDS, 6(2):e207, (2022). [DOI: 10.1097/EE9.0000000000000207]

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DOI: Is maternal employment site a source of exposure misclassification in studies of environmental exposures and birth outcomes? A simulation-based bias analysis of haloacetic acids in tap water and hypospadias.
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Last updated on February 13, 2025
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