Up to 460,000 people, or about 10% of the population, are at risk of exposure to radon, a radioactive gas that causes lung cancer.
That’s according to a new risk map based on not just indoor radon data, but also geological data, giving a more detailed breakdown of the radon risk facing the public.
Traditionally such maps, produced by the Environmental Protection Agency (EPA), are solely based on indoor radon measurements.
The map, the outcome of research led by geologists at Trinity College Dublin (TCD), divides the country into three risk categories: high (HR), medium (MR), and low (LR).
The probability of living in a home with a concentration level above the referenced safe level of 200 becquerels per cubic metre (Bq/m3) is calculated to be 19% in HR areas, 8% in MR areas, and 3% in LR areas. This equates to around 265,000 people, 160,000 people, and 35,000 people respectively.
The researchers, who also included the EPA and Geological Survey Ireland, said their results provide a high spatial resolution map which “will permit customised radon-awareness information to be targeted at specific geographic areas”. The research has just been published in the journal Science of the Total Environment.
Quentin Crowley, assistant professor in isotopes and the environment from the School of Natural Sciences at Trinity College Dublin, said the geological factors looked at in producing the map included bedrock composition, glacial sediment, soil permeability and type of aquifer.
The researchers said geology is “known to be the main factor controlling indoor radon concentrations”.
The new radon risk map illustrates the same general categories as the EPA map but does so at a different spatial scale, which makes it easier to identify regional or local variations in radon risk. For example, the South-East and West of Ireland feature as regionally prominent HR areas but the map indicates homes with high radon could potentially be found in any county. Current building regulations to protect against radon are framed around the EPA map.
Barbara Rafferty of the EPA said: “No model, no matter how sophisticated, can substitute for having indoor radon levels tested”.
“For this reason, we advise all householders to test their homes for radon and, if high levels are found, to have their houses fixed,” she said.
Radon is an odourless, naturally occurring radioactive gas which can only be detected using specialised equipment. It emanates from the ground where it may either escape to the atmosphere and be diluted, or accumulate to higher concentrations in enclosed spaces.
Radon levels vary from house to house depending on the building location, construction type and usage. The average indoor radon level in houses in Ireland is 77 becquerels per cubic metre (Bq/m3), although levels up to 550 times this value have been measured. Ireland is also among the countries with the highest average indoor radon concentrations in the world.
Globally, radon is the second highest cause of lung cancer after smoking.
Further information is available on radon.ie.
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