NOVEMBER 2007

Radon gas comes from the radioactive decay of uranium which occurs naturally in all rocks and soils. Radon is soluble in water and thus may accumulate in water as it passes over rocks and through soil. As radon is a gas it is easily lost from water when it is agitated for example when river or lake water flows over rocks or is moved by wind. This is very like what happens when a bottle of fizzy mineral water is shaken; the bubbles released represent the loss of dissolved gas. In this way surface water (lake and river water), which currently accounts for approximately 75% of drinking water supplies in Ireland, normally shows very low levels of radon.

Ground water (from wells and bore holes) on the other hand, does not tend to be agitated before reaching the domestic tap, so if there is radon present it tends to remain in the water. When the domestic tap is turned on some of the radon will be released into the air due to the agitation of the water as it is dispensed from the tap, but some will remain dissolved in the water and may be consumed.

Health implications of radon in drinking water
Ingestion of dissolved radon will result in a radiation dose to the lining of the stomach. However, a definitive link between consumption of radon-bearing water and cancer has not been established. Inhalation of radon gas that has been released from tap water will contribute to the radon content of indoor air and, if inhaled, will result in a radiation dose to the lung. Long-term exposure to high concentrations of radon in indoor air increases the risk of lung cancer.

Globally, the radiation dose from radon in drinking water is low compared with that from the inhalation of radon gas. However it is prudent to regard both of these sources of radon with similar concern and reasonable measures should be taken to minimise exposure to radon in drinking water. For this reason the Institute advises that domestic water supplies of groundwater or partial groundwater origin should be tested for radon, and if the recommended standards are exceeded the supply should be remediated.

It should be noted that while the Institute estimates that approximately 91,000 houses or 7% of the national housing stock have levels of radon in air that exceed the National Reference Level, less than 3% of the groundwater supplies tested to date contain radon levels that exceed the recommended standards.

Recommended Standards
Guidance on levels of radon and its decay products in drinking water is covered in EC Recommendation (2001/928/Euratom) on the protection of the public against exposure to radon in drinking water supplies. The Recommendation proposes 1000 becquerels per litre (Bq/l) as an action level for both public and private water supplies and can be summarised as follows:

For public water supplies, if the radon concentration exceeds 1000 Bq/l, remediation is considered justified. Where the radon level is above 100 Bq/l but below 1000 Bq/l, the local authority must consider whether this poses a risk to human health. If it is concluded that such a risk exists, then remedial action should be considered.

For private water supplies, where water is found to have levels of radon in excess of 1000 Bq/l remediation of the supply should be considered.

The Institute advises that where the radon level in public water supplies is above 500 Bq/l remediation is considered justified for the protection of human health

The definition of “public water supplies” includes:

• drinking water supplied as part of a public or commercial activity (including private water supplies to public facilities, such as schools and hospitals)
  
• group water schemes

What areas of Ireland are at risk?
There is no direct relationship between the amount of uranium in the underlying rocks and soil and the concentration of radon in the water supply, nor has any direct relationship been established between radon in indoor air and radon in water. Therefore it is not possible to predict if any areas of Ireland are more at risk than others. For this reason the Institute recommends that all domestic water supplies of groundwater or partial groundwater origin are tested for radon.

Information on radon testing
To have your water tested for radon download an application form. The application form should be printed out, completed and returned to the Institute with the appropriate payment. Alternatively, phone the Institute’s FREEPHONE RADON 1800 300 600. The Institute charge for radon analysis is €62 per water sample.

Remediation of water supplies
In many cases domestic water will be boiled before being consumed. Boiling effectively removes almost all of the radon dissolved in the water. However, the radon released during boiling will enter the air of the house and the occupants will then be exposed to the risk of inhaling radon gas. For this reason boiling of water should be carried out in a well-ventilated space, and for practical reasons, it is not recommended as a long-term remediation strategy.

Because radon is a gas that is readily lost from water over time or due to agitation of the water, the installation of a holding tank, an aeration unit or an agitation system, between the source and the domestic tap will significantly reduce the level of radon in the tap water. Proven radon in drinking water remediation products are available and information on radon remediation in Ireland can be obtained by contacting the Institute on envirolab@rpii.ie or by phoning the Institute’s radon freephone 1-800-300-600.


Irish readers google http://www.rpii.ie/images/maps/iremap.jpg if instructions do not work

Technical Note: Version 4.0 (or higher) of Microsoft Internet Explorer is required to view the radon maps

Leinster Carlow Dublin Kildare Kilkenny Laois Louth Longford Meath Offaly Westmeath Wexford Wicklow Munster Clare Cork Kerry Limerick Tipperary Waterford

Connaught Galway Leitrim Mayo Roscommon Sligo Ulster Cavan Donegal Monaghan A radon map for Northern Ireland can be found on the UK HPA (Health Protection Agency) website.

Radon is a naturally occurring radioactive gas which originates from the decay of uranium in rocks and soils. It is colourless, odourless and tasteless and can only be measured using special equipment. When radon surfaces in the open air, it is quickly diluted to harmless concentrations, but when it enters an enclosed space, such as a house or other building, it can sometimes accumulate to unacceptably high concentrations.

Apply for a Radon measurement

Radon decays to form tiny radioactive particles, some of which remain suspended in the air. When inhaled into the lungs these particles give a radiation dose which may damage cells in the lung and eventually lead to lung cancer.

Radon concentration is measured in becquerels per cubic metre of air (Bq/m³). The becquerel is a unit of radioactivity and corresponds to one radioactive disintegration per second.

The Reference Level for long-term exposure to radon in a house, above which the need for remedial action should be considered, is 200 Bq/m³ (determined in accordance with RPII's standard protocol). Based on current knowledge it is estimated that in Ireland, for the population as a whole, a lifetime exposure (ie 70 yrs) to radon in the home at the Reference Level of 200 Bq/m³ carries a risk of about 1 in 50 of contracting fatal lung cancer. This is approximately twice the risk of death in a road accident.

Since July 1998, every new house is required to incorporate some degree of radon preventive measures at the time of construction in accordance with the revised Building Regulations. The degree of protection required is dependent upon whether or not the site is located within a High Radon Area.

Monitoring incase of International Accidents at Nuclear Facilities for Electricity

Constant Monitoring The RPII with support from Met Éireann, local authorities and the Defence Forces operates a national network of permanent radiation-monitoring stations which are operational around the clock. These stations include air samplers and gamma dose monitors. Data from the gamma monitors is continuously fed back to a central computer at RPII. While the initial warning of an accident abroad would come from the international notification systems, this network would provide the first measurements in the event of a radioactive 'cloud' reaching Ireland. If elevated radiation levels are detected, an alarm system is automatically triggered. Gamma Dose Rate Stations The location of our stations are shown on the map. Click on a station to get the latest monitoring data Gamma Dose Rate Measurements The gamma dose rate provides a measure of the amount of energy a body receives from the surrounding gamma radiation. This radiation is always present and occurs naturally. Gamma dose rate is measured in units of microsieverts per hour (µSv/h). The normal gamma dose rates vary with local geology and typically range from 0.05 to 0.12 µSv/h. These dose rates include a component of 0.03 µSv/h due to cosmic radiation. A typical gamma dose rate graph is shown below: If a radioactive 'cloud' reaches Ireland, these gamma detectors will detect the associated elevated radiation levels and an alarm will be triggered. Radon Washout A phenomenon known as radon washout can cause short-term increases in gamma radiation levels. An explanation of radon washout and the effect on the measured gamma dose rate can be found here. Additional Monitoring In the case of an accident, additional gamma dose rate measurements will be provided by the Reserve Defence Forces. Particulate matter in the air is continuously sampled at 10 stations using filters that are changed on a weekly basis and sent for analysis to the Institute’s Environmental Laboratory. In the event of an accident the filters would be changed and analysed more frequently. In addition charcoal filters will be used to test for any radioactive iodine present in gaseous form. The analysis provides information on the concentration of radionuclides present in the air and this can be used to estimate the radiation doses to individuals following inhalation of radioactivity. Foodstuffs and environmental samples will be collected and analysed for contamination (see the RPII Role). The Civil Defence and local authorities will assist the RPII in this role by collecting the neccessary samples.

Radiological Protection Institute of Ireland (RPII)
3 Clonskeagh Square, Clonskeagh Road, Dublin 14, Ireland.
Tel: +353 1 269 77 66. Fax: +353 1 269 74 37. Email:rpii@rpii.ie