| Estimated Effects of Disinfection By-products on Preterm Birth in a Population Served by a Single Water Utility Chad Lewis,1 Irwin H. Suffet,1 Katherine Hoggatt,2 and Beate Ritz3,4 1Environmental Science and Engineering Program, Department of Environmental Health Sciences, School of Public Health, University of California, Los Angeles, California, USA; 2Department of Epidemiology, School of Public Health, University of Michigan, Michigan, USA; 3Department of Epidemiology, and 4Department of Environmental Health Sciences, School of Public Health, University of California, Los Angeles, California, USA Abstract
Objectives: We 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. Methods: During 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. Results: For 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. Conclusions: This 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. Key words: disinfection by-products, environmental exposure, pregnancy second trimester, preterm birth, selective fetal loss, trihalomethanes, water. Environ Health Perspect 115:290–295 (2007) . doi:10.1289/ehp.9394 available via http://dx.doi.org/ [Online 4 October 2006]
Address correspondence to C. Lewis, 8 Pinewood Ave., Natick, MA 01760 USA. Telephone: (617) 835-9789. Fax: (617) 386-8504. E-mail: myta_3@yahoo.com. Thanks to R. Rosofsky of Health Information Systems Consulting for providing SAS programming support and to the memory of R. Roemer. The authors declare they have no competing financial interests. Received 2 June 2006 ; accepted 4 October 2006.
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