Late Pregnancy Exposures to Disinfection By-products and Growth-Related Birth Outcomes

Abstract

Toxicologic studies have demonstrated associations between growth-related birth outcomes and exposure to high concentrations of disinfection by-products (DBPs), including specific tri-halomethane (THM) and haloacetic acid (HAA) chemical subspecies. Few prior investigations of DBPs have evaluated exposure during the third trimester of pregnancy, the time period of gestation when fetal growth may be most sensitive to environmental influences. We conducted a retrospective cohort study to examine the effects of exposure to THMs and HAAs during the third trimester and during individual weeks and months of late gestation on the risks for term low birth weight, intrauterine growth retardation, and very preterm and preterm births. The study population (n = 48,119) included all live births and fetal deaths occurring from January 1998 through March 2003 to women whose residence was served by one of three community water treatment facilities. We found evidence of associations between exposure to specific HAAs and term low birth weight as well as intrauterine growth retardation and for exposure to the five regulated HAAs (HAA5) and term low birth weight. Our findings suggest a critical window of exposure with respect to fetal development during weeks 33–40 for the effects of dibromoacetic acid and during weeks 37–40 for the effects of dichloroacetic acid. Adjustment for potential confounders did not affect the conclusions.

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

“…Hinckley et al (2005) found no association with THMs, but did for some specific HAAs. Studies on small for gestational age (SGA) and/or intrauterine growth retardation (IUGR) showed some more consistent results, and a good proportion of them have found statistically significant associations (Kramer et al 1992;Bove et al 1995;Wright et al 2003Wright et al , 2004, while some did not (Dodds et al 1999;Porter et al 2005;Yang et al 2007;Hoffman et al 2008b) (table 3).…”

“…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.…”

“…For example, studies on SGA/IUGR by Dodds et al (1999), Wright et al (2003Wright et al ( , 2004 and Hinckley et al (2005), on congenital anomalies by Hwang et al (2002Hwang et al ( , 2008 and Nieuwenhuijsen et al (2008) and on stillbirth by Toledano et al (2005) provide sufficiently large numbers of cases to create various exposure categories with more robust risk estimates, which could improve the overall assessment of risk.…”

“…In addition, some studies have investigated other DBPs such as HAAs and/or MX (e.g. Klotz & Pyrch 1999;Wright et al 2004;Hinckley et al 2005;Porter et al 2005;Savitz et al 2006;Luben et al 2007Luben et al , 2008Hoffman et al 2008;MacLehose et al 2008) and/or total organic halides (TOX) (e.g. Savitz et al 2006;Hoffman et al 2008).…”

Evaluation of two methods of interpolating quarterly trihalomethane levels between sampling dates

“…A simple weighted average assumes, incorrectly of course, a linear change in DBP levels between sampling dates. Hinckley et al (2005) used a cubic spline fitted to the available sampling data to produce estimates of the DBP levels between sample dates and used these estimates to derive exposure values. A spline fit makes no causal assumptions about changes in DBP levels between sampling dates but simply creates a best fit, smooth curve between multiple samples.…”