The Open UniversitySkip to content
 

Modelling exposure to disinfection by-products in drinking water for an epidemiological study of adverse birth outcomes

Whitaker, Heather; Best, Nicky; Nieuwenhuijsen, Mark J.; Wakefield, Jon; Fawell, John and Elliott, Paul (2005). Modelling exposure to disinfection by-products in drinking water for an epidemiological study of adverse birth outcomes. Journal of Exposure Analysis and Environmental Epidemiology, 15(2) pp. 138–146.

DOI (Digital Object Identifier) Link: http://dx.doi.org/10.1038/sj.jea.7500380
Google Scholar: Look up in Google Scholar

Abstract

We are conducting an epidemiological study on the association between disinfection by-product concentrations in drinking water and adverse birth outcomes in the UK, using trihalomethane (THM) concentrations over defined water zones as an exposure index. Here we construct statistical models using sparse routinely collected THMs measurements to obtain quarterly estimates of mean THM concentrations for each water zone. We modelled the THM measurements using a Bayesian hierarchical mixture model, taking into account heterogeneity in THM concentrations between water originating from different source types, quarterly variation in THM concentrations and uncertainty in the true value of undetected and rounded measurements. Quarterly estimates of mean THM concentrations plus estimates of the water source type (ground, lowland surface or upland surface) were obtained for each water zone. THM concentration estimates were typically highest from July to September (third quarter), and varied considerably between water sources. Our exposure estimates were categorized into 'low', 'medium' and 'high' THM classes. Our modelled quarterly exposure estimates were compared to a simple alternative: annual means of the raw data for each water zone. In all, 15-25% of exposure estimates were classified differently. The modelled THM estimates led to slightly stronger and more precise estimates of association with risk of still birth and low birth weight than did the raw annual means. We conclude that our modelling approach enabled us to provide robust quarterly estimates of ecological exposure to THMs in a situation where the raw data were too sparse to base exposure assessment on empirical summaries alone.

Item Type: Journal Article
Copyright Holders: 2005 Nature Publishing Group
ISSN: 1053-4245
Keywords: disinfection by-products; trihalomethanes; Bayesian hierarchical models; mixture models; exposure assessment;
Academic Unit/Department: Mathematics, Computing and Technology > Mathematics and Statistics
Item ID: 18262
Depositing User: Colin Smith
Date Deposited: 04 Sep 2009 08:54
Last Modified: 02 Dec 2010 20:37
URI: http://oro.open.ac.uk/id/eprint/18262
Share this page:

Altmetrics

Scopus Citations

Actions (login may be required)

View Item
Report issue / request change

Policies | Disclaimer

© The Open University   + 44 (0)870 333 4340   general-enquiries@open.ac.uk