A Framework for Estimating the Adverse Health Effects of Contamination Events in Water Distribution Systems and its Application

Abstract

Intentional or accidental releases of contaminants into a water distribution system (WDS) have the potential to cause significant adverse health effects among individuals consuming water from the system. A flexible analysis framework is presented here for estimating the magnitude of such potential effects and is applied using network models for 12 actual WDSs of varying sizes. Upper bounds are developed for the magnitude of adverse effects of contamination events in WDSs and evaluated using results from the 12 systems. These bounds can be applied in cases in which little system-specific information is available. The combination of a detailed, network-specific approach and a bounding approach allows consequence assessments to be performed for systems for which varying amounts of information are available and addresses important needs of individual utilities as well as regional or national assessments. The approach used in the analysis framework allows contaminant injections at any or all network nodes and uses models that (1) account for contaminant transport in the systems, including contaminant decay, and (2) provide estimates of ingested contaminant doses for the exposed population. The approach can be easily modified as better transport or exposure models become available. The methods presented here provide the ability to quantify or bound potential adverse effects of contamination events for a wide variety of possible contaminants and WDSs, including systems without a network model.

Assessing Inhalation Exposures Associated with Contamination Events in Water Distribution Systems

“…We have used Networks E1, E2, and E3, labeled as Networks 2, 4, and 6, respectively [8], and Network E3, labeled as Network N1 [60]. Networks E2 and E3 were used by Watson et al [61] as their Network2 and Network3, respectively; they have made the models for these two networks available.…”

“…Table 1 summarizes the various steps involved in determining inhalation and ingestion doses for a simulated individual. Approaches for estimating water concentration and ingestion doses are available [8]. The focus here is on estimating air concentrations of a contaminant at the point of exposure and accounting for the behavior of simulated individuals that results in exposure to airborne contaminants.…”

“…Finally, determination of system-wide consequences and the analysis of such consequences are discussed. The method used to estimate ingestion doses has been described previously [8] and the details are not repeated here. All simulated individuals are assumed to have the potential to ingest contaminated water.…”

“…The approach has been incorporated into U.S. EPA’s TEVA-SPOT software [40], which allows users to carry out consequence assessments for contamination events and to design contamination warning systems to help determine if such events have occurred. The capabilities provided for addressing potential inhalation exposures complement those already developed for addressing ingestion of contaminated tap water [8]. The framework is useful for applications involving both intentional and inadvertent contamination of a drinking water distribution system.…”

Simulation Model of Contamination Threat Assessment in Water Network Using the Epanet Software

“…The threshold values are characterized by the harmful effect when the body's physiological reserves are depleted and they take into account the ability to regenerate body [28,31].…”