The indicative maps produced by the Health Protection Agency & British Geological Survey aim to provide guidance as to the areas of the country most likely to be affected by high levels of radon gas, however are they really helping cut radon exposure amongst the British public or just adding to confusion?
In 1990 the National Radiological Protection Board (now part of the Health Protection Agency, HPA) published the first map of radon ‘Affected Areas’ in the UK, then focusing only on Cornwall. Data from radon monitoring carried out in homes was combined with geological data from the British Geological Survey (BGS) to predict the areas that were most likely to be affected by elevated levels of radon.
Since then the maps have been extended to cover the whole of the UK and have been superseded a number of times as more test data becomes available. The latest set of maps was published in 2007 and a significant proportion of the country is now designated as potentially affected by radon.
The maps are colour-coded from white through various shades of yellow and brown, with the darkest colour representing the areas where it has been estimated that the greatest number of properties with high levels of radon will be found. Areas of the country where it has been estimated that less than 1% of properties will contain radon levels over the ‘Action Level’ of 200 Bq/m3 are left white.
Although HPA have recently been phasing in the terms “lower risk”, “intermediate risk” and “higher risk” areas relating to white, yellow and brown colour-coding on the maps, many people still mistakenly believe that the white areas of the map are “not-affected” and as such are “safe”. This is not necessarily the case, and no building can be considered to be safe from radon unless it has been tested. A white area on the map simply means that the data available does not indicate that there is a strong likelihood of radon being found there.
Testing has historically been carried out in the locations where people expected to find radon, such as in granite or limestone areas or former mining regions. As testing has become more commonplace, individuals have carried out tests in other parts of the country and the results have shown that radon can be found almost anywhere in the country. Subsequently, each time the radon maps are updated the areas shaded in yellow or brown have increased in size and location.
A building control officer at a private practice in London at a seminar on the subject of radon said in his introduction to his colleagues, “As you know from the latest set of maps, radon has now spread into London.” Unfortunately this is a common misconception amongst the public and even professionals: a floodgate has not been opened and released the gas into other parts of the country; the gas has always been there but unfortunately not enough people thought to look for it there sooner!
Another misconception is that the maps indicate the concentration of radon in a given area. The maps are based on the probability of the number of properties containing an annual average radon concentration of 200 Bq/m3 or more (the domestic ‘action level). They therefore address the (estimated) frequency of the problem, not the scale of it. The frequency with which radon may be found in buildings is not the same as an indication that higher concentrations of radon will be found in those
A final point of confusion is that the maps should only be used in relation to above-ground properties and should be disregarded if the property in question has a basement. HPA advises that “high radon levels can be found in basements anywhere in the country, regardless of Affected Area status”. If a property has a basement, the owners / occupiers should proceed as if it was located in a higher-risk band on the maps, regardless of the designation of the actual geographic area.
Whilst the maps are of use in prioritising areas where central Government resource might best be spent on carrying out awareness drives or offering reduced-price testing for instance, the majority of people in the UK will be interested in their own property alone rather than a statistical estimate for their neighbourhood.
Most people want to establish if there is radon in a particular building, not its prevalence in an area. The questionis most commonly asked when they are concerned about their or their family’s health, if they have a workplace or are buying/selling a house. In those cases, the only way to answer the question they are really asking is to test the building they are concerned about. Maps indicating general areas of possibility merely serve to confuse when people require precise answers.
Radon testing is an inexpensive process (see our Test Kits page for more details). Unfortunately the maps are often misunderstood and can lull those people who are unfamiliar with radon into a false sense of security, potentially putting them and their families at risk from radon exposure without them knowing until it is too late.