title: Variations in trihalomethane levels in three French water distribution systems and the development of a predictive model.
abstract: Epidemiological studies have demonstrated that chlorination by-products in drinking water may cause some types of cancer in humans. However, due to differences in methodology between the various studies, it is not possible to establish a dose-response relationship. This shortcoming is due primarily to uncertainties about how exposure is measured-made difficult by the great number of compounds present-the exposure routes involved and the variation in concentrations in water distribution systems. This is especially true for trihalomethanes for which concentrations can double between the water treatment plant and the consumer tap. The aim of this study is to describe the behaviour of trihalomethanes in three French water distribution systems and develop a mathematical model to predict concentrations in the water distribution system using data collected from treated water at the plant (i.e. the entrance of the distribution system). In 2006 and 2007, samples were taken successively from treated water at the plant and at several points in the water distribution system in three French cities. In addition to the concentrations of the four trihalomethanes (chloroform, dichlorobromomethane, chlorodibromomethane, bromoform), many other parameters involved in their formation that affect their concentration were also measured. The average trihalomethane concentration in the three water distribution systems ranged from 21.6 μg/L to 59.9 μg/L. The increase in trihalomethanes between the treated water at the plant and a given point in the water distribution system varied by a factor of 1.1-5.7 over all of the samples. A log-log linear regression model was constructed to predict THM concentrations in the water distribution system. The five variables used were trihalomethane concentration and free residual chlorine for treated water at the plant, two variables that characterize the reactivity of organic matter (specific UV absorbance (SUVA), an indicator developed for the free chlorine consumption in the treatment plant before distribution δ) and water residence time in the distribution system. French regulations impose a minimum trihalomethane level for drinking water and most tests are performed on treated water at the plant. Applied in this context, the model developed here helps better to understand trihalomethane exposure in the French population, particularly useful for epidemiological studies.
authors.affiliation: French Institute for Public Health Surveillance (InVS), 14 rue de Val d'Osne, 94415 Saint-Maurice cedex, France. damien.mouly@ars.sante.gouv.fr
authors.forename: Damien
authors.initials: D
authors.lastname: Mouly
authors.forename: Eric
authors.initials: E
authors.lastname: Joulin
authors.forename: Christophe
authors.initials: C
authors.lastname: Rosin
authors.forename: Pascal
authors.initials: P
authors.lastname: Beaudeau
authors.forename: Abdelkrim
authors.initials: A
authors.lastname: Zeghnoun
authors.forename: Agnès
authors.initials: A
authors.lastname: Olszewski-Ortar
authors.forename: Jean François
authors.initials: JF
authors.lastname: Munoz
authors.forename: Bénédicte
authors.initials: B
authors.lastname: Welté
authors.forename: Michel
authors.initials: M
authors.lastname: Joyeux
authors.forename: René
authors.initials: R
authors.lastname: Seux
authors.forename: Antoine
authors.initials: A
authors.lastname: Montiel
authors.forename: M J
authors.initials: MJ
authors.lastname: Rodriguez
mesh_terms: D005602:France; D008956:Models, Chemical; D015999:Multivariate Analysis; D012044:Regression Analysis; D013997:Time Factors; D022882:Trihalomethanes / Q000032:analysis*; D035501:Uncertainty; D018508:Water Purification; D014881:Water Supply / Q000032:analysis*
chemical_list: D022882:Trihalomethanes