Abstract
Approximately one million people in the UK are served by private water supplies (PWS) where main municipal water supply system connection is not practical or where PWS is the preferred option. Chronic exposure to contaminants in PWS may have adverse effects on health. South West England is an area with elevated arsenic concentrations in groundwater and over 9000 domestic dwellings here are supplied by PWS. There remains uncertainty as to the extent of the population exposed to arsenic (As), and the factors predicting such exposure. We describe a hazard assessment model based on simplified geology with the potential to predict exposure to As in PWS. Households with a recorded PWS in Cornwall were recruited to take part in a water sampling programme from 2011 to 2013. Bedrock geologies were aggregated and classified into nine Simplified Bedrock Geological Categories (SBGC), plus a cross-cutting “mineralized” area. PWS were sampled by random selection within SBGCs and some 508 households volunteered for the study. Transformations of the data were explored to estimate the distribution of As concentrations for PWS by SBGC. Using the distribution per SBGC, we predict the proportion of dwellings that would be affected by high concentrations and rank the geologies according to hazard. Within most SBGCs, As concentrations were found to have log-normal distributions. Across these areas, the proportion of dwellings predicted to have drinking water over the prescribed concentration value (PCV) for As ranged from 0% to 20%. From these results, a pilot predictive model was developed calculating the proportion of PWS above the PCV for As and hazard ranking supports local decision making and prioritization. With further development and testing, this can help local authorities predict the number of dwellings that might fail the PCV for As, based on bedrock geology. The model presented here for Cornwall could be applied in areas with similar geologies. Application of the method requires independent validation and further groundwater-derived PWS sampling on other geological formations.
Highlights
Domestic Private Water Supplies (PWS) provide water used for drinking and cooking to a proportion of the population varying according to the availability of alternative sources and distribution networks and householder attitudes
The aim of this paper is to develop a methodology for a population-based hazard assessment and ranking of hazard for As in PWS used for drinking, based on geological bedrock classification
Private well records used for access to users of PWS for domestic use were obtained by Public Health England (PHE) in the form of a database compiled by the local authority, according to the provision of the PWS Regulations [28,33]
Summary
Domestic Private Water Supplies (PWS) provide water used for drinking and cooking to a proportion of the population varying according to the availability of alternative sources and distribution networks and householder attitudes. Environmental Public Health Tracking (EPHT) can be defined as “the ongoing collection, integration, analysis and interpretation of data about environmental hazards, exposure to environmental hazards, and human health effects potentially related to exposure to environmental hazards. It includes dissemination of information learned from these data and implementation of strategies and actions to improve and protect public health” [14]. The EPHT approach could be applied to PWS in other geographical areas [20]
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