Radon exposure

Daryl Dixon of the Heath Protection Agency outlines the dangers of radon gas, and what it means for procedure in the work place

Nobody who moves to a new house would expect to have to think about an unseen hazard to their health in the new property, yet levels of the natural radioactive gas radon can sometimes be a significant source of risk to occupants. Radon is present in all buildings because it is drawn in from the ground through gaps in the floor. Although levels are low in many areas, including the main UK population centres, there are an estimated 100,000 homes with high radon across many parts of the country.

Radon is the largest source of radiation exposure for most people - accounting for half the total annual radiation dose for most UK residents, but as it has no taste, smell or colour, people will not know of its presence. Inhalation of radon is associated with increased risk of lung cancer, causing more than 1,000 deaths per year in the UK, and the Health Protection Agency has an active programme to identify and reduce this source of exposure.

In a project with the British Geological Survey (BGS), HPA has jointly developed and published information that shows the areas of England and Wales where high radon levels are most likely to occur. This article explains how information about radon is relevant to professionals involved with property ownership and how it can be accessed and used.

Radon affected areas of England and Wales
Sources and standards
Factors that contribute to high radon include:
The type of underlying ground
The nature of floor and connection to the ground
Environmental conditions in the building.

Because air pressure inside a building is generally slightly lower than outside, mainly as a result of heating, radon is drawn up through joints, cracks and shrinkage gaps in the floor, as well as through service entries such as water and sewage pipes or electricity cables. Once inside a structure, the radon level is affected by ventilation, which is determined by factors such as draught proofing and occupancy patterns.

International studies of the health of people exposed to radon over many years provide a firm basis on which to set standards. For the UK, a level of 200 Bq m-3 has been adopted as the national standard for dwellings in the UK – this is known as the action level. The unit is Becquerel (Bq) which is a measure of the amount of radioactivity. In order to direct resources to areas with the greatest risk from radon, the Health Protection Agency designates as affected areas any location in the UK where the proportion of houses with radon above the action level is expected to exceed one percent.

Despite generalisations about levels of radon in properties, however, It is not possible to make a reliable estimate of the level from a visual inspection of a building, so a measurement is needed to determine the level of risk to occupants. Consequently, HPA advises occupants of all premises in affected areas to arrange a measurement, as described below.

National and regional programmes for protection of people from radon in buildings are usually implemented by reference to affected areas. The first step, therefore, is to find out whether a property is in an affected area. An important element of the HPA work programme in recent years has been to increase ease of access and understanding of this information for the many stakeholders concerned.

The procedure used to identify the affected areas designated in the most recent reports has developed significantly from that in previous analyses. affected areas as currently defined integrate data from the very large number of measurement results held by HPA with information on the underlying geology. This provides much greater accuracy and resolution than was previously achievable. Individual properties can now be checked to show the chance that they will have a radon level exceeding the action level, in bands from less than 1 percent - a non affected area - 1-3 percent, 3-5 percent, 5-10 percent, 10-30 percent and greater than 30 percent.

Whereas previous data was published in map form, the greatly increased level of information and detail now provided makes it impracticable to show the full detail in map form. Affected areas for Scotland and Northern Ireland are also being identified by the same procedures and are to be updated in due course.

Finding affected areas
A prospective occupier is likely to have the greatest interest in whether action might be required to reduce radon. In addition, however, professionals such as solicitors, surveyors and estate agents who act in property transactions will also wish to ensure that their advice reflects the most accurate and reliable information available. To meet the needs of the various potential users, Affected Area data are presented in alternative formats with very important differences:
As a dedicated website for those who require precise and detailed information about one or more specific properties, and as an indicative atlas, that provides an overview of the extent of affected areas across the country but must not be used for individual properties.

The new website, www.ukradon.org is designed to provide simple and easy access to the definitive data. This is the source that must be used for all formal enquiries relating to specific, identified properties
Log on to www.ukradon.org
Enter postcode
Select one address form those shown for the post code
Pay a fee of £3 + VAT by credit card
View and print off report

The website provides a one page report that provides the formal response on two important issues that arise during property conveyance.
1 A declaration whether an existing property is in an affected area as required by the CON29 form that has to be completed by solicitors, and
2 For proposed extensions and some new properties, a conclusion as to whether building regulations require the structure to be built with radon preventative measures.

The website also provides a facility for users who require multiple searches to pre-purchase and hold credits in an account to avoid re-entering their details.

Many professional users already obtain search data from commercial search providers (also known as Value Added Resellers, VAR), and under a commercial agreement with BGS, these companies now use the same definitive data that underpin the website. Affected Area data are also available from BGS under a specific user license for those who require moderate numbers of searches for a particular area, such as district councils.
In addition to providing the information required by individuals and their agents prior to purchase, there will be interest about Affected Area status of sites from site developers and planners. At present such enquiries will often require a more detailed response and are referred to BGS which is able to conduct the full range of geological investigation with specialist interpretation if required.

Indicative atlas
This atlas can provide only a general guide to the extent of radon affected areas in different regions of England and Wales. It is intended to assist in the development of strategic health protection policy by local authorities and the identification of regional priorities and resource development. Experience has shown that data presented as maps is popular with many users, both for general planning purposes and also for judging risks in individual properties.
The atlas shows the affected area designation for each one km sq of the ordnance survey for the whole of England and Wales with summary geographical detail such as major roads, water bodies and district council boundaries. Users should note, however that the probability banding shown is the worst case, corresponding to that of the geological unit with the highest potential anywhere in the square. The indicated probability is not, therefore, representative for every property within the square. This approach ensures that no significant areas of high radon potential are missed, but means that using the Indicative atlas to judge the affected area status of a property will often be misleading. Only in the squares that are shown as below 1 percent can it reliably be concluded that no home in that square is on an Affected geological unit.

Users
Copies of the radon atlas were distributed to all district council offices in England and Wales and came into effect on 12th November 2007. The data is being used by various departments, and other groups, as shown in the table below.
Means of access to Affected Area data are being improved to make them as useful and accessible to as many people as possible. Improvements are underway to improve the clarity and functionality of the website and to develop a responses for searches on buildings that are very large, such as workplaces, and brand new premises or development sites for which no full postcode address is available.

Measuring radon
For any property in a radon affected area, a simple measurement provides the information required by an occupier to decide on the need for further action. The procedure recommended by HPA uses two small passive detectors that are cheap and sufficiently robust to be sent to the user by post. The natural variability of radon levels in buildings, however, means that a long measurement period is required to get a reliable estimate of the long term average level - advice from HPA, therefore, is to measure over three months.

Users and uses of Radon Affected Area data

Purpose
Data type/source
District councils
Environmental Health
To identify areas at risk and advise local residents
Atlas
Building Control -
Assess Building Regulations requirement for preventative measures against radon
www.ukradon.org Website or license
Housing -
Housing policy and fitness
Atlas
Land charges
Answer CON29 question
www.ukradon.org Website or license
Health and Safety enforcement
to identify workplaces at risk and advise local employers
Atlas, for general guidance
Others
Individual householders
Assess potential hazard and need for measurement
www.ukradon.org Website or VAR
Individual employer
Assess potential hazard and need for risk assessment
www.ukradon.org Website, or VAR. Atlas if prioritising amongst many properties
Corporate landlords
As employer
Professional agents
Advise on specific property e g CON29 question
www.ukradon.org Website or VAR
Site developers
Assess need for prevention
BGS Website
Policy makers
Develop national standards
Atlas

Employers in affected areas or other circumstances where high levels of radon are known to be more likely, should measure radon as part of their normal risk assessment procedure. The number of monitors required in a workplace building depends on its size and use, but it is not usually necessary to measure above the ground floor or in normally unoccupied places such as cupboards or stores. Advice from HPA about numbers of monitors and selection of measurement locations for workplaces is at www.hpa.org.uk/radiation/services/radon/work.htm.
It should be noted that even in affected areas, this measurement will show radon in the large majority of cases to be below the action level and will reassure occupants. For the small proportion with high levels, radon levels can almost always be reduced with simple building works, allowing occupiers to reduce their risk of disease.

Conclusions
A new atlas and website, developed jointly by the Health Protection Agency and British Geological Survey, show areas of England and Wales where high levels of radon gas are most likely to occur and provide an important resource for professionals who need to advise clients about radon.