Exposure to disinfection by-products during pregnancy

Publication authors

Smith R.B.; Nieuwenhuijsen M.J.; Bennett J.E.; Toledano M.B.; Wright J.; Raynor P.


Background/Aims: Many studies of disinfection by-products (DBPs) in drinking water and adverse birth outcomes have been limited by a lack of individual-level data on water use for exposure assessment, and by potential residual confounding. Uncertainty remains as to the most important factors driving exposure to DBPs, and which factors may be potential confounders. We have investigated these issues whilst performing exposure assessment for a new birth cohort.

Methods: Patterns of water consumption, showering, bathing, and swimming were analyzed for women in the Born in Bradford cohort (n = 4045). These individual-level water use data were collected by questionnaire and validated in a nested study (n = 39), using a 7-day exposure diary. Semi-individual metrics of exposure to trihalomethanes (THMs) during pregnancy were calculated for 2710 women combining individual-level water use data and modeled area-level THM concentrations. Semi-individual exposure metrics were analyzed using ANOVA to assess the contribution of spatial, temporal, and individual components of variability.

Results: Preliminary results show that water consumption, showering, bathing, and swimming differ according to demographic and lifestyle variables (eg, combined showering/bathing per week decreases across increasing age groups, with a difference of almost 2 hours between youngest and oldest age groups), and suggest accuracy of self-reported water use data differs according to employment status. Whilst underlying patterns of spatial and temporal variation in THM concentrations at the tap can be observed in semiindividual THM exposure metrics their contributions to total variability are very small, and it appears the majority (83%-96%) of variability in THM exposure is explained by individual variation in water use behavior.

Conclusion: This study provides important insights into the accuracy of self-reported exposure data and the factors driving DBP exposure amongst pregnant women. The findings are valuable to inform exposure assessment and epidemiological analysis in studies assessing the relationship between DBPs and adverse birth outcomes.