A study of radon levels in NHS premises in affected areas around the UK

Radon gas contributes a significant fraction of the natural background radiation dose, and in some areas raised levels are found in buildings. both homes and the workplace. Different UK Action Levels apply to homes and the workplace. because of the diurnal variation of radon. This study reviews the results for a number of hospitals throughout England and Wales. and suggests that the likelihood of finding raised radon levels is similar in the workplace and homes in the same area. Radon measurements and consequent remediation of any raised levels are appropriate in all workplaces in radon Affected Areas with over 5% of houses above the UK domestic Action Level of 200 Bq m(-3).     

Domestic radon remediation of UK dwellings by Sub-Slab Depressurisation: evidence for a baseline contribution from constructional materials

To quantify the effectiveness of Sub-Slab Depressurisation, widely used in the United Kingdom (U.K.) to mitigate indoor radon gas levels in residential properties, a study was made of radon concentration data collected from a set of 170 homes situated in Radon Affected Areas in Northamptonshire and neighbouring counties, remediated using conventional sump/pump technology. A high incidence of satisfactory remediation outcomes was achieved, with 100% of the houses remediated demonstrating post-remediation radon concentrations below the U.K. domestic Action Level of 200 Bq m(-3), while more than 75% of the sample exhibited radon mitigation factors (defined as the ratio of radon concentrations following and prior to remediation) <0.2. Two systematic trends are identified. Firstly, absolute radon concentration reduction following remediation is directly proportional to initial radon concentration, with a mean reduction factor of 0.96 and a residual component of around 75 Bq m(-3). Secondly, houses with lower initial radon concentrations demonstrate poorer (higher) mitigation factors. These observations support a model in which the total indoor radon concentration within a dwelling can be represented by two principal components, one susceptible to mitigation by sub-slab depressurisation, the other remaining essentially unaffected. The first component can be identified with radon emanating from the subsoil and bedrock geologies, percolating through the foundations of the dwelling as a component of the soil-gas, and potentially capable of being attenuated by sub-slab depressurisation or radon-barrier remediation technologies. The second contribution can be identified with radon emanating from materials used in the construction of the dwelling with a further contribution from the natural background level, and is essentially unaffected by ground-level remediation strategies. Modelling of a multi-component radon dependency using ground-radon attenuation factors derived from the experimental data, in conjunction with typical background and structural-radon levels, yields behaviour in good agreement with the observed dependence of mitigation factor on initial radon concentration.     

The costs and benefits of radon remediation programmes in existing homes: case study of action level selection

Radon gas can be present within buildings at sufficiently high levels that it becomes a health risk. Such levels can be reduced, and so radon remediation programmes in the home in UK Affected Areas should result in reduced risks to the population. This paper considers the benefits and costs of the domestic radon remediation programme in Northamptonshire, UK, and considers the implications of the choice of Action Level, in view of the adoption of different levels in many countries. A programme with a higher Action Level will cost less, and target those most at risk, but will be less cost effective. In addition, a higher Action Level leaves a higher residual dose and risk to the remaining population. Such doses are higher than and inconsistent with the radiation dose limits for the general public in the EU Basic Standards Directive.     

The cost effectiveness of radon reduction programmes in domestic housing in England and Wales: The impact of improved radon mapping and housing trends

In the UK, excessive levels of radon gas have been detected in domestic housing. Areas where 1% of existing homes were found to be over the Action Level of 200 Bq · m^− 3 were declared to be Radon Affected Areas. Building Regulations have been introduced which require that, for areas where between 3% and 10% of existing houses are above the Action Level, new homes should be built with basic radon protection using a membrane, and that, where 10% or more of existing homes exceed this level, new homes should be built with full radon protection.Initially these affected areas followed administrative boundaries, known as Counties. However, with increasing numbers of measurements of radon levels in domestic homes recorded in the national database, these areas have been successively refined into smaller units – 5 km grid squares in 1999, down to 1 km grid squares in 2007.One result is the identification of small areas with raised radon levels within regions where previously no problem had been identified. In addition, some parts of areas that were previously considered radon affected are now considered low, or no, risk. Our analysis suggests that the net result of improved mapping is to increase the number of affected houses. Further, the process is more complex for local builders, and inspectors, who need to work out whether radon protection in new homes is appropriate.Our group has assessed the cost-effectiveness of radon remediation programmes, and has applied this analysis to consider the cost-effectiveness of providing radon protection in both new and existing homes. This includes modelling the potential failure rate of membranes, and whether testing radon levels in new homes is appropriate. The analysis concludes that it is more cost effective to provide targeted radon protection in high radon areas, although this introduces more complexity.The paper also considers the trend in housing to a greater proportion of apartments, the regional variations in types of housing and the decreasing average number of occupants in each dwelling, and concludes that data and methods are now available to respond to the health risks of radon at a local level, in keeping with a general initiative to prioritise responses to health and social welfare issues at a more local level.     

Lung-cancer reduction from smoking cessation and radon remediation: a preliminary cost-analysis in Northamptonshire, UK

Domestic radon levels in parts of the United Kingdom are sufficiently high as to increase the risk of lung-cancer among residents. Public health campaigns in the county of Northamptonshire, a designated radon Affected Area with 6.3% of homes having average radon levels in excess of the UK Action Level of 200 Bq m(-3), have encouraged householders to test for radon and then, if indicated to be necessary, to carry out remediation in their homes. These campaigns have been only partially successful, since to date only 40% of Northamptonshire houses have been tested, and only 15% of those householders finding raised levels have proceeded to remediate. Those who remediate have been shown to have smaller families, to be older, and to include fewer smokers than the average population, suggesting that current strategies to reduce domestic radon exposure are not reaching those most at risk. During 2004-2005, the NHS Stop-Smoking Services in Northamptonshire assisted 2847 smokers to quit to the 4-week stage, the 15% (435) of these 4-week quitters remaining quitters at 1year forming the subjects of a retrospective study considering whether smoking cessation campaigns contribute significantly to radon risk reduction. Quantitative assessment of the risk of lung-cancer among the study population, from knowledge of the individuals' age, gender, and smoking habits, together with the radon levels in their homes, demonstrates that smoking cessation programmes have significant added value in reducing the incidence of lung-cancer in radon Affected Areas, and contribute a substantially greater health benefit at a lower cost than the alternative strategy of reducing radon levels in the smokers' homes, while they remain smokers. Both radon remediation and smoking cessation programmes are very cost effective in Northamptonshire, with smoking cessation being significantly more cost effective, and these are potentially valuable programmes to drive health improvements through promotion of the uptake or environmental management for radon in the home.     

Analysis of the individual health benefits accruing from a domestic radon remediation programme

Although radon can be present within buildings at sufficient levels to pose a health risk, levels can be reduced relatively easily. Recent studies on a group of radon-remediated homes, based on assessment of collective population-average risk coefficients, have estimated the benefits and cost effectiveness accruing from remediation and have confirmed that domestic remediation in UK radon Affected Areas would result in significantly reduced cancer risks to the population in those areas. Although the population-average approach used hitherto has applied occupancy and lung-cancer risk factors, these are potentially misleading in assessing discrete populations. The study reported here uses the recently developed European Community Radon Software (ECRS) to quantify individual risks in a sample of householders who remediated their homes following indications that radon levels exceeded the action level. The study proceeds from population-averaged to 'individual risk' evaluation, successfully comparing individual and collective risk assessments, and demonstrates that those who remediate are not representative of the general population. Health benefits accruing from remediation are three times lower than expected, largely because remediators are older, live in smaller households, and smoke less than the population average, leading to the conclusion that the current strategy employed in the UK is failing to target those most at risk.     

A critical comparison of the cost-effectiveness of domestic radon remediation programmes in three counties of England

Radon remediation programmes in domestic dwellings were carried out in five areas, from three counties of England, and the total costs obtained. A single company, which abided by the Code of Practice of the Radon Council of Great Britain, carried out the remediation. The dose savings from the programmes were calculated and used to estimate the number of lung cancers averted. The data obtained allowed the cost-effectiveness of the remediation programmes in each area to be calculated. The remediation programmes in three areas (Northants 2, 3 and North Oxfordshire) were cost-effective whereas those in two areas (Northants 1 and North Somerset) were not. To be cost-effective, the Northants I and North Somerset areas would need to increase the number of householders that carried out remediation, if they were over the UK Action Level. Health policy makers should concentrate their resources on communities in areas where there is a significant proportion of dwellings above the UK Action Level and where the number of properties being remediated is low.     

Radon remediation of a two-storey UK dwelling by active sub-slab depressurisation: effects and health implications of radon concentration distributions

Radon concentration levels in a two-storey detached single-family dwelling in Northamptonshire, UK, were monitored continuously throughout a 5-week period during which active sub-slab depressurisation remediation measures were installed. Remediation of the property was accomplished successfully, with both the mean radon levels and the diurnal variability greatly reduced both upstairs and downstairs. Following remediation, upstairs and downstairs radon concentrations were 33% and 18% of their pre-remediation values respectively: the mean downstairs radon concentration was lower than that upstairs, with pre- and post-remediation values of the upstairs/downstairs concentration ratio, R(U/D), of 0.81 and 1.51 respectively. Cross-correlation between upstairs and downstairs radon concentration time-series indicates a time-lag of the order of 1 h or less, suggesting that diffusion of soil-derived radon from downstairs to upstairs either occurs within that time frame or forms a relatively insignificant contribution to the upstairs radon level. Cross-correlation between radon concentration time-series and the corresponding time-series for local atmospheric parameters demonstrated correlation between radon concentrations and internal/external pressure difference prior to remediation; this correlation disappears following remediation. Overall, these observations provide further evidence that radon concentration levels within a dwelling are not necessarily wholly determined by the effects of soil-gas advection, and further support the suggestion that, depending on the precise content of the building materials, upstairs radon levels, in particular, may be dominated by radon exhalation from the walls of the dwelling, especially in areas of low soil-gas radon.     

Two error components model for measurement error: application to radon in homes

In this paper, a simple model for analysing variability in radon concentrations in homes is tested. The approach used here involves two error components, representing additive and multiplicative errors, together with variation between-houses. We use a Bayesian approach for our analysis and apply this model to two datasets of repeat radon measurements in homes; one based on 3-month long measurements for which the original measurements were close to the current UK Radon Action Level (200 Bq m⁻³), and the other based on 6-month measurement data (from regional and national surveys), for which the original measurements cover a wide range of radon concentrations, down to very low levels. The model with two error components provides a better fit to these datasets than does a model based on solely multiplicative errors.     

Resolving the radon problem in Clinton, New Jersey, houses

Significantly elevated radon concentrations were found in several adjacent houses in Clinton, New Jersey. The United States Environmental Protection Agency screened 56 of the houses and selected 10 for demonstration of radon-reduction techniques. Each of the 10 houses received an intensive radon diagnostic evaluation before a house-specific radon reduction plan was developed. Depressurization effects caused by temperature differentials and the operation of mechanical equipment were quantified. Before and after radon reduction plans were implemented, radon concentrations were determined by charcoal canisters and continuous radon monitors. A variety of sealing and subslab depressurization techniques were applied to the 10 houses. Radon concentrations were reduced by over 95% in all 10 houses. The cost of applying radon reduction techniques ranged from $1500 to $8500 per house. House construction characteristics were described which contributed to the high cost of radon reduction. In summary, the 10-house radon reduction demonstration in Clinton, New Jersey was successful in showing homeowners with similar house types some effective ways of reducing radon concentrations.     

A cost-effectiveness analysis of radon protection methods in domestic properties: a comparative case study in Brixworth, Northamptonshire, UK

Building regulations in the UK have since 1992 required that radon-proof membranes be installed in new domestic properties to protect residents against the adverse effects of radon. This study compares the cost-effectiveness of the current regulatory regime with an alternative that would entail new properties being tested for radon after construction, and being remediated if necessary. The alternative regime is found to be more cost-effective for a sample of properties in Brixworth, Northamptonshire, UK. For this regime, the central estimate of cost per quality-adjusted life-year gained, the measure of cost-effectiveness used, is 2869 pounds compared to 6182 pounds for installing membranes, results suggesting a case for re-examining the current regulations on radon protection in new properties. Pilot studies will, however, be needed to consider how different means of protecting residents of new properties against radon might operate in practice and to provide improved evidence on their relative cost-effectiveness.     

Radon in the creswell crags Permian limestone caves

An investigation of radon levels in the caves of Creswell Crags, Derbyshire, an important Site of Special Scientific Interest (SSSI) shows that the Lower Magnesian Limestone (Permian) caves have moderate to raised radon gas levels (27-7800 Bq m(-3)) which generally increase with increasing distance into the caves from the entrance regions. This feature is partly explained in terms of cave ventilation and topography. While these levels are generally below the Action Level in the workplace (400 Bq m(-3) in the UK), they are above the Action Level for domestic properties (200 Bq m(-3)). Creswell Crags has approximately 40,000 visitors per year and therefore a quantification of effective dose is important for both visitors and guides to the Robin Hood show cave. Due to short exposure times the dose received by visitors is low (0.0016 mSv/visit) and regulations concerning exposure are not contravened. Similarly, the dose received by guides is fairly low (0.4 mSv/annum) due in part to current working practice. However, the risk to researchers entering the more inaccessible areas of the cave system is higher (0.06 mSv/visit). This survey also investigated the effect of seasonal variations on recorded radon concentration. From this work summer to winter ratios of between 1.1 and 9.51 were determined for different locations within the largest cave system.     

Regional geology and radon variability in buildings

Radon concentrations in dwellings vary by more than two orders of magnitude. Predicting where and when concentrations are likely to be high requires studying the variability of the contributors to radon in buildings. Among common sources, geological factors (water supply and substrate) are the most variable, whereas building materials are much less variable. Ventillation variation among houses is generally responsible for radon variations comparable to those introduced by building materials, but it is more significant at lower ventilation rates. In some regions with relatively high proportions of houses with elevated radon concentrations, mappable geological factors are associated with most cases of high radon concentrations. However, a priori identification of rock types likely to be implicated is likely to be successful in only a few cases.     

The value of Seasonal Correction Factors in assessing the health risk from domestic radon: a case study in Northamptonshire, UK

Following an intensive survey of domestic radon levels in the United Kingdom (UK), the former National Radiological Protection Board (NRPB), now the Radiation Protection Division of the Health Protection Agency (HPA-RPD), established a measurement protocol and promulgated Seasonal Correction Factors applicable to the country as a whole. Radon levels in the domestic built environment are assumed to vary systematically and repeatably during the year, being generally higher in winter. The Seasonal Correction Factors therefore comprise a series of numerical multipliers, which convert a 1-month or 3-month radon concentration measurement, commencing in any month of the year, to an effective annual mean radon concentration. In a recent project undertaken to assess the utility of short-term exposures in quantifying domestic radon levels, a comparative assessment of a number of integrating detector types was undertaken, with radon levels in 34 houses on common geology monitored over a 12-month period using dose-integrating track-etch detectors exposed in pairs (one upstairs, one downstairs) at 1-month and 3-month resolution. Seasonal variability of radon concentrations departed significantly from that expected on the basis of the HPA-RPD Seasonal Correction Factor set, with year-end discontinuities at both 1-month and 3-month measurement resolutions. Following this study, monitoring with electrets was continued in four properties, with weekly radon concentration data now available for a total duration in excess of three and a half years. Analysis of this data has permitted the derivation of reliable local Seasonal Correction Factors. Overall, these are significantly lower than those recommended by HPA-RPD, but are comparable with other results from the UK and from abroad, particularly those that recognise geological diversity and are consequently prepared on a regional rather than a national basis. This finding calls into question the validity of using nationally aggregated Seasonal Correction Factors, especially for shorter exposures, and the universal applicability of these corrections is discussed in detail.     

A critical evaluation of the cost-effectiveness of radon protection methods in new homes in a radon Affected Area of England

In the UK, building new homes in areas prone to radon gas is currently subject to regulations that require installation of radon-proof membranes. These membranes are not, however, the only way to protect residents of new homes against radon's potential to cause lung cancer. Alternative regulatory regimes can be constructed that would achieve the same end.The purpose of this paper is to examine the cost-effectiveness of four alternative regimes and so determine if building regulations for new homes could be altered to protect residents from the effects of radon more cost-effectively than at present. In addressing this question, the paper also contributes to the wider debate on how best to reduce the effect on public health of exposure to radon.The measure of cost-effectiveness used, cost per quality-adjusted life-year gained, is determined from radon test results obtained in properties in Brixworth, England, UK, a radon Affected Area. Confidence intervals for the cost-effectiveness estimates are also derived using bootstrap techniques.The central estimates of cost-effectiveness range from £2870 per quality-adjusted life-year gained for the most cost-effective of the alternative regimes to £6182 for the current regime. These results suggest that alternative regimes may be more cost-effective in tackling the radon problem. A definitive assessment of the most suitable to adopt will require extensive negotiation between government departments, the construction industry, and other interested parties to ensure acceptance of any new regime. The paper offers suggestions for future research that should help in the process of identifying the key features of a new regulatory approach.     

Mitigation of a radon-rich Belgian dwelling using active subslab depressurization

In a radon prone area in Belgium, a dwelling with high indoor radon concentrations was identified through a passive measurement. Next, a continuous, active radon monitoring device was installed for one month. A 20-a retrospective radon assessment was also performed. The house was subsequently mitigated through active subslab depressurization with a radial fan. Afterwards the dwelling was actively monitored for several more months to observe the effects of the mitigation and to study the effect of reducing the fan power. Dose evaluations were made to evaluate the health benefit of the mitigation. It was seen that the results of the three measuring techniques before mitigation all yielded between 1700 and 2000 Bq/m3. Clear diurnal radon variations showed up only after mitigation. After mitigation, the average radon concentration fell to less than 200 Bq/m3. The yearly average dose was reduced from potentially 45 mSv/y to less than 4.5 mSv/y through mitigation. Reducing fan power to 50% did not clearly influence the amount of radon entering into the dwelling.     

Health implications of radon distribution in living rooms and bedrooms in U.K. dwellings--a case study in Northamptonshire

Environmental radon exposure of residents of domestic premises in the United Kingdom (UK) and elsewhere in Europe is estimated on the basis of the measured radon concentrations in, and the relative occupancies of, the principal living room and bedroom. While studies on radon concentration variability in the individual units in apartment blocks in various countries have been described, little data has been reported on variability in two-storey single-family dwellings, and the majority of extant studies consolidate living room and bedroom data early in the analysis. To investigate this further, detailed analysis was made of radon concentration data from a set of thirty-four homes situated in areas of Northamptonshire known to exhibit high radon levels. All homes were of typical UK construction of brick/block/stone walls under a pitched tile/slate roof. Approximately 50% of the sample were detached houses, the remainder being semi-detached (duplex) or terraced (row-house). Around 25% of the sample possessed cellars, while 12% were single-storey dwellings (bungalows), reflecting the typical incidence of this type of dwelling in England. In the two-storey homes, all monitored bedrooms were on the upper floor. Distribution of the ratios of bedroom/living room radon concentrations (BR/LR ratio) in individual properties was left-skewed (mean 0.67, median 0.73, range 0.05-1.05) with a tail extending to just above 1.0. The mean is consistent with the outcome of earlier extensive studies in England, while the variability depends principally on the characteristics of the property, and not on seasonal factors. In a small set of homes, the BR/LR ratio was anomalously low, (mean 0.3). BR/LR ratios in single-storey homes clustered around a value of 1.0, indicating that house design, rather than lifestyle, is the dominant factor in determining bedroom radon concentrations. Homes with higher mean annual radon concentrations showed lower BR/LR ratios, supporting our proposal that, in some homes, radon emanation from building materials may comprise a significant component of the overall radon level.     

A detailed evaluation of the individual health benefits arising in a domestic property following radon remediation--a case-study in Northamptonshire, U.K

Radon gas occurs naturally in the environment with variable distribution, concentrating sufficiently in the built environment in some areas to pose a public health risk. Radon levels can be successfully reduced in affected buildings, and large-scale remediation programmes have been justified in terms of accrued costs and benefits. We present results from a house where radon levels in the main living-room and master bedroom were monitored on an hourly basis over extended periods before and after radon remediation by sub-slab depressurisation. These results were combined with results from a recent occupancy survey to estimate the health impact on occupants spending varying times in the home. Prior to remediation, mean hourly radon exposure is moderately linearly correlated (R(2)=0.66-0.78) with time spent in the house. Following remediation, correlation is significantly enhanced (R(2)=0.91-0.95), but the exposure reduction of an occupant following remediation is less than that predicted using the NRPB protocol.     

Low-infiltration housing in Rochester, New York: A study of air-exchange rates and indoor air quality

A sample of 58 occupied homes in Rochester, NY, most of which incorporated special builder-designed weatherization components, were studied to assess (1) the effectiveness of construction techniques designed to reduce air leakage; (2) the indoor air quality and air-exchange rates in selected airtight houses, and (3) the impact on indoor air quality of mechanical ventilation systems employing air-to-air heat exchangers. The “specific leakage area” was measured in each house using the fan pressurization technique. Houses built with polyethylene vapor barriers and joint-sealing were as a group 50% tighter than a similar group of houses without such components. Mechanical ventilation systems with air-to-air heat exchangers were installed in nine relatively airtight houses, some of which had gas stoves and/or tobacco smoking occupants. Air-exchange rates and indoor concentrations of radon (Rn), formaldehyde (HCHO), nitrogen dioxide (NO₂), and humidity were measured in each house for 1-week periods with and without mechanical ventilation. More detailed measurements, including concentrations of carbon monoxide and inhalable particulates, were made in two of these houses by a mobile laboratory. In all nine houses, air-exchange rates were relatively low (0.2–0.5 ach) without mechanical ventilation, and yet indoor concentrations of Rn, HCHO, and NO₂ were below existing guidelines. Mechanical ventilation systems were effective in further reducing indoor contaminant concentrations. We conclude that when contaminant source strengths are low, acceptable indoor air quality can be compatible with low air-exchange rates.     

An approach to improve the Austrian Radon Potential Map by Bayesian statistics

A Radon Potential Map as well as a mean indoor Radon Concentration Map is available from the Austrian National Radon Project (1992-2002). These maps are based on the average Radon Potential/Concentration within every municipality and they sort municipalities into three radon ‘risk’ classes. This is a convenient way for the administration, but it does not describe the real radon risk distribution within a municipality because of the often inhomogeneous geological situation. Therefore, a combination of indoor radon data with all relevant parameters such as house type, storey and ventilation rates along with geological information should be used to improve the existing radon maps. The method, described here, uses Bayes' theory to combine the Radon Potential derived from indoor radon measurements with information from geology. The existing Radon Potential Map was improved by using available soil gas radon data at certain geological units and extrapolated transfer factors. The modifications of the map are shown and several problems arising with the application of this technique are discussed.