High radon levels found in Wicklow ground water supplies

Date released: Mar 11 2003

A survey of drinking water supplies in 166 houses in County Wicklow has identified four supplies (representing 2.4% of the total) with radon concentrations above the European Commission (EC) recommended action level of 1000 becquerels per litre (Bq/l).

This is one of the key findings of a pilot study on radon in drinking water published today by the Radiological Protection Institute of Ireland (RPII).

The study was initiated following a EC recommendation that surveys should be undertaken in Member States to determine the scale and nature of exposures due to radon in domestic drinking water supplies. The principal objective of the study was to assess the distribution of radon levels in private water supplies in an area of Ireland where some high levels would be expected. County Wicklow was selected for the study on the basis that the underlying geology is predominantly granite which contains high levels of uranium from which radon is derived; also, many parts of the county had previously been identified as High Radon Areas. Ground water supplies were targeted as studies from other countries had shown that high radon levels are often found in drinking water supplies derived from ground water. Samples were collected by Wicklow County Council as part of its routine sampling scheme and forwarded to the Institute’s laboratory in Clonskeagh for analysis.

Radon activity concentrations were measured between August 2001 and May 2002 in tap water collected from 166 houses in Co. Wicklow. In all cases, a private ground water supply was the principal source of drinking water for the house occupants. Four supplies had activity concentrations in excess of the recommended EC action level of 1000 Bq/l, fifteen had activity concentrations between 500 and 1000 Bq/l, 51 were between 100 and 500 Bq/l and 96 had activity concentrations below 100 Bq/l. The highest concentration found was 5985 Bq/l. All of the householders where the high readings were measured were contacted by the RPII to inform them of the results and to recommend that remedial action be taken.

The results from the study demonstrate that radon in drinking water may pose a significant additional health risk, in the longer term, to a small percentage of consumers who depend on private ground water supplies as their primary source of drinking water. The Institute advises that all householders using private ground water supplies as their primary source of water should have their supply tested for radon. Where the EC recommended value of 1000 Bq/l is exceeded remedial action should be taken to reduce the radon concentration.

Additional information on radon is available on the website.

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Notes to Editors

Radon gas is produced directly from the radioactive decay of uranium. Radon is soluble in water and groundwater supplies provide a means by which radon can enter homes. Normally the concentration of radon in surface water supplies is very low.

While radon is produced by uranium, high levels of radon in drinking water do not necessarily mean that the levels of uranium will also be high. As part of this study, 16 drinking water samples were measured for both radon and uranium and no correlation could be established.

The Institute, in cooperation with the local authorities, implements a programme for monitoring radioactivity levels in drinking water. The current programme entails the sampling of a selection of public water supplies serving populations in excess of 10,000. Samples are tested for both naturally and artificially occurring radionuclides and the results are published by the RPII in its environmental surveillance reports. There is currently no routine radioactivity monitoring of ground water supplies.

The Institute has issued advice to all Local Authorities concerning the monitoring of public drinking water supplies for radioactivity. This advice includes information on the identification of supplies most likely to be at risk and guidance in relation to recommended levels.

Proven radon in drinking water remediation products are available and in use in other countries, although the authors of the report are unaware of any similar commercial products currently available on the Irish market. It is established, however, that where there is immediate concern, as an interim measure boiling the water in a well-ventilated area prior to consumption can reduce the radon level to negligible concentrations.

This report deals exclusively with radon in drinking water. The Institute has published previous studies on radon levels in air in Irish homes. Maps showing High Radon Areas (i.e. areas in which more than 10% of houses are predicted to have radon in air concentrations above the Reference Level of 200 Bq/m3) are available on the Institute website. Exposure to radon in air in the home remains the principal contributor to radiation dose for the majority of the Irish population.