| Relation between Stillbirth and Specific Chlorination By-Products in Public Water Supplies Will D. King,1 Linda Dodds,2,3 and Alexander C. Allen2,3 1Department of Community Health and Epidemiology, Queen's University, Kingston, Canada
2Perinatal Epidemiology Research Unit, IWK Grace Health Centre, Halifax, Nova Scotia, Canada
3Departments of Obstetrics and Gynecology and Pediatrics, Dalhousie University, Halifax, Nova Scotia, Canada Abstract
During water treatment, chlorine reacts with naturally occurring organic matter in surface water to produce a number of by-products. Of the by-products formed, trihalomethanes (THMs) are among the highest in concentration. We conducted a retrospective cohort study to evaluate the relationship between the level of total THM and specific THMs in public water supplies and risk for stillbirth. The cohort was assembled from a population-based perinatal database in the Canadian province of Nova Scotia and consisted of almost 50,000 singleton deliveries between 1988 and 1995. Individual exposures were assigned by linking mother's residence at the time of delivery to the levels of specific THMs monitored in public water supplies. Analysis was conducted for all stillbirths and for cause-of-death categories based on the physiologic process responsible for the fetal death. Total THMs and the specific THMs were each associated with increased stillbirth risk. The strongest association was observed for bromodichloromethane exposure, where risk doubled for those exposed to a level of  20 µg/L compared to those exposed to a level < 5 µg/L (relative risk = 1.98, 95% confidence interval, 1.23-3.49) . Relative risk estimates associated with THM exposures were larger for asphyxia-related deaths than for unexplained deaths or for stillbirths overall. These findings suggest a need to consider specific chlorination by-products in relation to stillbirth risk, in particular bromodichloromethane and other by-product correlates. The finding of a stronger effect for asphyxia deaths requires confirmation and research into possible mechanisms. Key words: chlorination by-products, epidemiology, public water supplies, stillbirth, trihalomethanes. Environ Health Perspect 108:883-886 (2000) . [Online 2 August 2000] http://ehpnet1.niehs.nih.gov/docs/2000/108p883-886king/ abstract.html Address correspondence to W.D. King, Department of Community Health and Epidemiology, Abramsky Hall, Queen's University, Kingston, Ontario K7L 3N6 Canada. Telephone: (613) 533-6000, ext. 74735. Fax: (613) 533 6686. E-mail: kingw@post.queensu.ca We thank C. Woolcott and J. Pole for computing support and J. Scott and D. Briggins for their helpful discussions. This research was supported by the Prince Edward Island Reproductive Care Program through Health Canada Green Plan funds. The perinatal data were provided by the Nova Scotia Reproductive Care Program, and the chlorination by-product data were provided by the Nova Scotia Department of the Environment. Received 21 January 2000 ; accepted 17 May 2000.
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