title: Trihalomethanes in public drinking water and stillbirth and low birth weight rates: an intervention study.
abstract: During 2003-2004, United Utilities water company in North West England introduced enhanced coagulation (EC) to four treatment works to mitigate disinfection by-product (DBP) formation. This enabled examination of the relation between DBPs and birth outcomes whilst reducing socioeconomic confounding. We compared stillbirth, and low and very low birth weight rates three years before (2000-2002) with three years after (2005-2007) the intervention, and in relation to categories of THM change. We created exposure metrics for EC and trihalomethane (THM) concentration change (n=258 water zones). We linked 429,599 live births and 2279 stillbirths from national birth registers to the water zone at birth. We used Poisson regression to model the differences in birth outcome rates with an interaction between before/after the intervention and EC or THM change. EC treatment reduced chloroform concentrations more than non-treatment (mean -29.7 µg/l vs. -14.5 µg/l), but not brominated THM concentrations. Only 6% of EC water zones received 100% EC water, creating exposure misclassification concerns. EC intervention was not associated with a statistically significant reduction in birth outcome rates. Areas with the highest chloroform decrease (30 - 65 μg/l) had the greatest percentage decrease in low -9 % (-12, -5) and very low birth weight -16% (-24, -8) rates. The interaction between before/after intervention and chloroform change was statistically significant only for very low birth weight, p=0.02. There were no significant decreases in stillbirth rates. In a novel approach for studying DBPs and adverse reproductive outcomes, the EC intervention to reduce DBPs did not affect birth outcome rates. However, a measured large decrease in chloroform concentrations was associated with statistically significant reductions in very low birth weight rates.
authors.affiliation: Small Area Health Statistics Unit, MRC-PHE Centre for Environment and Health, School of Public Health, Imperial College London, London, UK; Department of Genes and the Environment, Division of Epidemiology, Norwegian Institute of Public Health, Oslo, Norway.
authors.forename: Nina
authors.initials: N
authors.lastname: Iszatt
authors.affiliation: Small Area Health Statistics Unit, MRC-PHE Centre for Environment and Health, School of Public Health, Imperial College London, London, UK; Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Spain; Municipal Institute of Medical Research Foundation (IMIM), Barcelona, Spain; Centre for Biomedical Investigation Network of Epidemiology and Public Health (CIBERESP), Barcelona, Spain.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Nieuwenhuijsen
authors.affiliation: Small Area Health Statistics Unit, MRC-PHE Centre for Environment and Health, School of Public Health, Imperial College London, London, UK.
authors.forename: James E
authors.initials: JE
authors.lastname: Bennett
authors.affiliation: Small Area Health Statistics Unit, MRC-PHE Centre for Environment and Health, School of Public Health, Imperial College London, London, UK. Electronic address: m.toledano@imperial.ac.uk.
authors.forename: Mireille B
authors.initials: MB
authors.lastname: Toledano
mesh_terms: D002725:Chloroform / Q000032:analysis; D004203:Disinfection; D060766:Drinking Water / Q000737:chemistry*; D005260:Female; D006801:Humans; D007230:Infant, Low Birth Weight; D008297:Male; D050497:Stillbirth / Q000453:epidemiology*; D022882:Trihalomethanes / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D060766:Drinking Water; D022882:Trihalomethanes; D014874:Water Pollutants, Chemical; D002725:Chloroform
keywords: Chloroform; Disinfection by-products; Drinking-water; Low birth weight; Stillbirth; Trihalomethanes