Estimated Effects of Disinfection By-products on Preterm Birth in a Population Served by a Single Water Utility

Abstract

ObjectivesWe evaluated the association between drinking-water disinfection by-products and preterm births using improved exposure assessment and more appropriate analysis methods than used in prior studies.MethodsDuring 1999–2001, vital record data were obtained for a large, racially diverse population residing in 27 Massachusetts communities that received drinking water from a single public utility. This water system was monitored weekly for total trihalomethanes (TTHM), and it maintained geographically stable total TTHM levels system-wide during the study period. We employed proportional hazards regression to examine the effects of trimester-specific and shorter-term peak exposures to TTHM in drinking water late in pregnancy on preterm births in 37,498 singletons.ResultsFor all women, our data suggested no more than a small increase, if any, in risk for delivering a preterm baby when exposed to ≥ 60 μg/L TTHM during the 4 weeks before birth [hazard ratio (HR) = 1.13; 95% confidence interval (CI), 0.95–1.35]. However, women who depended on a governmental source of payment for prenatal care were at increased risk when exposed at such levels late in gestation (HR = 1.39; 95% CI, 1.06–1.81). In contrast, exposure to high levels of TTHM during the second trimester and high exposure throughout pregnancy resulted in a 15–18% reduction in risk for preterm delivery in our population.ConclusionsThis finding confirms previous reports of a negative association during the second trimester. Our data also suggested a possible positive association with shorter-term third-trimester TTHM exposure in mothers of lower socioeconomic status.

Environmental Exposures, Genetic Susceptibility and Preterm Birth

“…Consistent with other recent studies (Källén & Robert;2000;Lewis et al, 2007;Nieuwenhuijsen et al, 2009) our findings suggest that THM exposures might increase the risk of preterm birth. The epidemiological evidence for an association between exposure to THM and preterm birth is relatively inconsistent.…”

“…Some authors find small increases in gestation age with increased TTHM exposure and with both chloroform and BDCM (Wright et al, 2003;2004). A negative association during the second trimester were reported, however, women who depended on a governmental source of payment for prenatal care were at increased risk when exposed at high levels TTHM late in gestation (OR 1.39; 95% CI, 1.06-1.81) (Lewis et al, 2007). Lack of a consistent effect of the epidemiologic studies may be result of a study design, be a result of exposure misclassification or inadequate control for confounding variables, or a lack of power in studies sample, or actual lack of an effect of DBP on reproductive effects.…”

Association of Brominated Trihalomethane and Haloacetic Acid Exposure With Fetal Growth and Preterm Delivery in Massachusetts

“…19,35 We detected some variation in the mean BWT and THM4 relationship by income quintiles in the unadjusted THM4 model (see the Supplementary Digital Content Table 5, http://links.lww.com/JOM/A132), but this was not evident in the multivariate regression models. Our analysis of effect-measure modification by income is limited by the potential misclassification of the group-level income data (ie, Census data).…”

“…[39][40][41] In addition, attenuation of effect estimates may occur if the reference group includes a combination of moderately and highly exposed individuals as observed in previous DBP studies. 13,18,19,35,42,43 Another strength of this study was the ability to examine low or unexposed reference groups for our categorical analyses given the large exposure contrasts for most DBP metrics. As part of our sensitivity analyses, we examined an unexposed population (THM4 = 0 μg/L) as the reference group (see the Supplementary Digital Content Table 6, http://links.lww.com/JOM/A132).…”

The epidemiology and possible mechanisms of disinfection by-products in drinking water

“…Studies on pre-term delivery have generally shown no statistically significant associations with DBPs (Kramer et al 1992;Bove et al 1995;Savitz et al 1995;Gallagher et al 1998;Wright et al 2003;Aggazzotti et al 2004;Hinckley et al 2005;Lewis et al 2007;Yang et al 2007), with the exception of the study by Yang et al (2000a) and Yang (2004), who found a statistically significant increased risk. Wright et al (2004) and Jaakkola et al (2001) found a statistically significant decreased risk of pre-term delivery.…”