Academic journal article Environmental Health Perspectives

Chlorination Disinfection By-Products and Risk of Congenital Anomalies in England and Wales

Academic journal article Environmental Health Perspectives

Chlorination Disinfection By-Products and Risk of Congenital Anomalies in England and Wales

Article excerpt

BACKGROUND: Increased risk of various congenital anomalies has been reported to be associated with trihalomethane (THM) exposure in the water supply.

OBJECTIVES: We conducted a registry-based study to determine the relationship between THM concentrations and the risk of congenital anomalies in England and Wales.

METHODS: We obtained congenital anomaly data from the National Congenital Anomalies System, regional registries, and the national terminations registry; THM data were obtained from water companies. Total THM (< 30, 30 to < 60, [greater than or equal to] 60 [micro]g/L), total brominated exposure (< 10, 10 to < 20, [greater than or equal to] 20 [micro]g/L), and bromoform exposure (< 2, 2 to < 4, [greater than or equal to] 4 [micro]g/L) were modeled at the place of residence for the first trimester of pregnancy. We included 2,605,226 live births, stillbirths, and terminations with 22,828 cases of congenital anomalies. Analyses using fixed-and random-effects models were performed for broadly defined groups of anomalies (cleft palate/lip, abdominal wall, major cardiac, neural tube, urinary and respiratory defects), a more restricted set of anomalies with better ascertainment, and for isolated and multiple anomalies. Data were adjusted for sex, maternal age, and socioeconomic status.

RESULTS: We found no statistically significant trends across exposure categories for either the broadly defined or more restricted sets of anomalies. For the restricted set of anomalies with isolated defects, there were significant (p < 0.05) excess risks in the high-exposure categories of total THMs for ventricular septal defects [odds ratio (OR) = 1.43; 95% confidence interval (CI), 1.00-2.04] and of bromoform for major cardiovascular defects and gastroschisis (OR = 1.18; 95% CI, 1.00-1.39; and OR = 1.38; 95% CI, 1.00-1.92, respectively).

CONCLUSION: In this large national study we found little evidence for a relationship between THM concentrations in drinking water and risk of congenital anomalies.

KEY WORDS: chlorination, congenital anomalies, disinfection by-products, trihalomethanes. Environ Health Perspect 116:216-222 (2008). doi:10.1289/ehp. 10636 available via [Online 6 November 2007]


Since chlorination disinfection by-products (DBPs) were first reported in drinking water (Rook 1974), there have been concerns about potential adverse reproductive health effects, including low birth weight, spontaneous abortion, stillbirth, and congenital anomalies (Nieuwenhuijsen et al. 2000a), but findings of the studies to date have been inconsistent. Statistically significant positive associations have been reported between trihalomethane (THM) exposure and neural tube defects (NTDs) (Bove et al. 1995; Dodds and King 2001; Klotz and Pyrch 1999), major cardiac defects (Cedergren et al. 2002; Hwang et al. 2002), urinary tract defects (Aschengrau et al. 1993; Hwang et al. 2002; Magnus et al. 1999), and respiratory defects (Aschengrau et al. 1993; Hwang et al. 2002), whereas other studies did not find such associations (Dodds et al. 1999; Kallen and Robert 2000; Shaw et al. 2003). Studies on oral cleft or cleft palate have largely been negative, except for the study by Bove et al. (1995). Only Dodds and King (2001) and Shaw et al. (2003) studied the effect of specific THMs. Dodds and King (2001) found a statistically significant association between bromodichloromethane (BDCM) and NTDs, whereas Shaw et al. (2003) found a few statistically significant negative associations with NTDs and cleft lip and palate. One of the main limitations in most of these studies has been small sample size, resulting in low power to explore exposure--response relationships.

In the present study, the largest study of its kind so far, we report the relationships between THM levels in the public water supply and risk of congenital anomalies across England and Wales. …

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