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Arsenic in private drinking water supplies

Sampling water for arsenic, courtesy BGS

Little is known about the arsenic levels of the underground aquifers which provide the only source of drinking water to many of the scattered communities beyond the areas served by public mains water supplies. In this project we aim to examine the hazard and potential public health risks from exposure.

Isolated agricultural and rural dwellings have to rely on borehole or well water for human consumption and whilst these supplies are regulated by UK legislation, very few are tested for the presence of metals, relying on microbiological parameters as a measure of potability. Based on a risk assessment conducted by the International Agency for Research on Cancer, arsenic exposure via ingestion has a recognised risk of several cancers and other chronic diseases.

Environmental public health tracking (EPHT) will relate arsenic exposure events with known hazards at population level such as sources of private drinking water supplies and interventions available to address these problems. This will be an example of 'hazard tracking'.

In order to achieve this, the following 10 steps were identified in the study:

  1. design of arsenic tracking programme
  2. collection of routine environmental data
  3. measurement in the field of arsenic in private water supplies
  4. population routine data surveillance
  5. population survey in sampling area
  6. biomonitoring of survey population
  7. environmental evaluation
  8. public health evaluation
  9. risk communication
  10. risk management

Hazard tracking flow diagram

Hazard tracking flow diagram

The sampling of arsenic from private water supplies: 2011 and 2013

Between 2011 and 2013; Public Health England (PHE) and the British Geological Survey (BGS), worked together on a two-phase sampling programme of private water supplies (PWS) in East followed by West Cornwall.

Approval from the Department of Health was received in mid-February 2011, following this our efforts and attention was focused on preparing for and carrying out the sampling procedure. This involved four weeks of intensive logistical planning for each field sampling campaign.

Initially letters were sent to all residents identified as having a private water supply; this data was provided by Cornwall council. The letter informed individuals that we would be contacting them shortly; it also provided residents with our contact details if they were interested in having their water supply tested and wanted to contact us directly.

We were overwhelmed with the number of calls and e-mails that we received by individuals wanting their private drinking water supply tested.

Routes around Cornwall had to be carefully planned in order to make best use of the time and resources available as well as taking the geology into consideration. Following planning we telephoned the individuals who had initially contacted us to arrange specific appointments, we also contacted other individuals who were sent letters but had not contacted us, to further extend their invitation to have their water tested.


The delivery involved a 17 day sampling programme whereby the British Geological Survey (BGS) visited 256 properties and took a total of 329 water samples from kitchen taps and direct from water sources across East Cornwall. Next BGS analysed the samples for about 60 specific metals and minerals, the outcomes were then reviewed.

Sampling water from private supplies for arsenic, courtesy BGS


In March 2013, the process was repeated for the second phase of sampling in West Cornwall. This involved an 18 day sampling programme with BGS visiting 256 properties and taking around 368 water samples from kitchen taps and water sources.


The results collected for over 500 households and showed that, in the case of arsenic (As) alone; 5.5% of drinking-water samples exceeded the 10 µg/L (micrograms per litre) prescribed concentration or value (PCV). These findings, in addition to the well documented high environmental arsenic concentrations in the region, warranted further investigation into the potential uptake of the element by the local population.

The next step in the ‘hazard tracking’ programme is to examine exposure levels of arsenic by taking biological samples in a biomonitoring study.

For more information please contact the environmental public health tracking team.

  • Biomonitoring study
    A cross-sectional study of the association between arsenic consumption from private drinking water supplies and measured biological levels in the population of Cornwall, UK.
    Added/updated: 26 June 2014