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. 2017 Dec 1;14(12):1490.
doi: 10.3390/ijerph14121490.

Hazard Ranking Method for Populations Exposed to Arsenic in Private Water Supplies: Relation to Bedrock Geology

Helen Crabbe  1 , Tony Fletcher  2   3 , Rebecca Close  4 , Michael J Watts  5 , E Louise Ander  6 , Pauline L Smedley  7 , Neville Q Verlander  8 , Martin Gregory  9 , Daniel R S Middleton  10   11   12 , David A Polya  13 , Mike Studden  14 , Giovanni S Leonardi  15   16
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Hazard Ranking Method for Populations Exposed to Arsenic in Private Water Supplies: Relation to Bedrock Geology

Helen Crabbe et al. Int J Environ Res Public Health. .

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.

Keywords: arsenic; environmental public health tracking; geology; hazard and exposure assessment; private water supplies; public health risk.

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Conflict of interest statement

The authors declare no conflict of interest. PHE as the funding sponsors designed the study; funded the collection, analyses and interpretation of data; PHE funded the writing of the manuscript, and made the decision to publish the results.

Figures

Figure 1
Figure 1
Map of Cornwall showing Simplified Bedrock Geological Classifications (SBGC), location and levels of arsenic measured in Private Water Supplies (PWS) tested. Geological data reproduced with the permission of the British Geological Survey © Natural Environment Research Council (NERC).
See this image and copyright information in PMC

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