protect new buildings in Radon Affected Areas ... Remediation of domestic properties will reduce dose from radon, and costs are such that domestic remediation.
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An Evaluation of the Effectiveness of the UK Programme to protect new buildings in Radon Affected Areas A.R.Denman 1, 4, J.Fraser 2, and P.S.Phillips 3 1
Medical Physics Department, Northampton General Hospital, Cliftonville, Northampton, NN1 5BD, UK. 2 Environmental Health Department, East Northamptonshire District Council. 3 School of Environmental Science, University College Northampton 4 Visiting Fellow in Medical Physics, University College Northampton
INTRODUCTION 222
Radon is a naturally occurring radioactive gas which has a variable geographical distribution, and has been shown to cause lung cancer in miners exposed to elevated levels (1). Recent epidemiological studies have shown that there is also significant risk from radon even at levels found in some domestic dwellings (2)(3). Remediation of domestic properties will reduce dose from radon, and costs are such that domestic remediation programmes for existing homes in many countries can be justified theoretically (4)(5)(6)(7), and shown to be so in practise in Northamptonshire (8). The discovery of areas in the UK with significant indoor radon levels prompted the National Radiological Protection Board (NRPB) to establish an Action Level of 200 Bq m-3 for domestic properties, and declare a number of radon Affected Areas where 1 % or more of homes are above the Action Level (9). Northamptonshire is such an area, with 6.3 % of homes above the Action Level (10). In 1992, the Building Research Establishment (BRE) published guidance for new homes built in Affected Areas (11) specifying measures designed to protect against radon. These measures are a legal requirement enforceable under the Building Regulations (12) in all houses built after January 1993. In high risk areas, with over 10 % of existing houses above the 200 Bq m-3 Action Level, primary protection in the form of a radon-proof membrane is required, as well as secondary protection in the form of a sump capable of being fitted with a low cost fan. In lower risk areas with 3 to 10 % of houses above the Action Level only secondary protection is specified. This latter requirement reduces the cost to the householder of providing radon remediation to around £150 for the fan, rather than an average of £750 for providing a sump and fitting a fan, but requires measurement of the radon level to judge whether remediation is required. In the guidance, the BRE specified the high risk and lower risk areas using the boundaries of local administrative areas, known as parishes, which correspond to villages or sections of larger towns. The data used to classify each parish was obtained from the NRPB records of radon level in domestic properties assessed up to 1992 (10). Northamptonshire has areas of both high and lower risk, as well as some areas where less than 3 % of houses are above the Action Level, and where no protection measures are required in new homes. Since 1992, NRPB has continued to record domestic radon levels and published regular updates (13), but this has not been incorporated into the BRE guidance. There has been a considerable influx of population into Northamptonshire in recent years, with 12,200 new houses built since 1993, which is around 5 % of the current housing stock of 256,900. Thus the efficacy of the protection of new homes is likely to have a significant health effect in Northamptonshire. This paper reports two studies, one of which assessed the cost-effectiveness and health benefits of theoretical primary protection in new homes in high risk areas. The other study was designed to test whether the use of secondary protection in lower risk areas achieved its aim, assessing radon levels and public awareness in two large housing estates in lower risk areas in East Northamptonshire.
METHODS A study of remediation of existing domestic properties in Northamptonshire has been reported by Denman and Phillips (14). This now extends to 65 homes of which 35 are in high risk areas. In these areas, the NRPB predict that 7.4 % of homes will have radon levels over the Action Level (13).The cost effectiveness of protection of new houses was calculated by assuming that the initial distribution of radon levels and the reduction achieved would be similar to that in existing houses, and that there was no failure rate in the membranes. An average occupancy of 72 % was assumed, as established by recent local surveys (15). For the study of lower risk areas, two new housing estates which were built in such areas were chosen. Each house was visited with an introductory letter, and offered a free radon test, and invited to fill in a questionnaire. TASTRAK detectors using CR-39 were chosen as these could be evaluated after a 6-day exposure. This maximised the number of detectors and questionnaires which were collected at the end of the test. The NRPB protocol was followed with one detector in the living room, and one in the main bedroom. A single seasonally corrected weighted 1
P-1b-29 average result was determined using the NRPB formula of 0.55 of the bedroom value and 0.45 of the living room value. The questionnaire was a mixture of open and closed non-biassed questions together with a number of openended questions designed to judge the householders’ knowledge of radon, and any advice they had received. Tests and questionnaires were completed by 99 houses from one estate (43 % response), and 34 from the second (34 % response).
RESULTS The initial radon levels of homes in high risk areas are shown in Figure 1. A collective dose reduction of 1.99 man-sieverts for the 86 occupants of the 35 homes was calculated. The current average cost of a good quality membrane is £310, although the actual cost will vary with the floor area. The total number of houses built to yield 35 houses over the Action Level would be 731, so that the cost of installing membranes in all would be £226,610. This gives a total cost of £113,800 per man-sievert saved annually.
10 Number of Homes
8 6 4 2
0 5 1 to 5 1 0 to 0 1 10 t 15 o 0 1 15 2 0 to 0 1 20 2 5 to 0 1 25 3 0 to 0 1 30 3 5 to 0 1 35 4 0 to 0 1 40 4 5 to 0 1 45 5 0 to 0 1 50 5 5 to 0 1 55 6 0 to 0 1 60 6 5 to 0 1 65 7 0 to 0 1 70 7 5 to 0 1 75 8 0 to 0 1 80 8 5 to 0 1 85 9 0 to 0 9 9 5 1 to 0 0 1 9 to 5 0 ov 10 er 00 10 00
0
Average Radon Level in Bq m -3.
Figure 1 - Initial Radon Levels in homes in high risk areas
7,900 homes have been built in high risk areas throughout Northamptonshire since 1993 so that the collective dose reduction of primary protection has now reached 23 man-sieverts per year. Using current NRPB risk estimates this is equivalent to 0.8 lung cancers avoided each year. This is similar to that achieved by the remediation programme in existing housing in Northamptonshire, although the potential saving in existing housing is much greater if more householders can be encouraged to carry out remediation (14). The radon levels measured in two estates in the lower risk areas are shown in Figure 2. The results for the estate A show 5 % over the Action Level as might be expected, but the estate B had 35 % of houses over the Action Level. The houses over the Action Level were predominantly in one street, suggesting a local outcrop of high radon emitting rock. 50 Estate B
30 20 10
45 0 to
40 0 40 1
to
35 0 35 1
to
30 0 30 1
to
25 0 25 1
to
20 1
to
20 0
15 0 15 1
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10 0 10 1
to 51
to
50
0 0
Number of Homes
Estate A 40
Average Radon Level in Bq m-3.
Figure 2 - Radon Levels in two housing estates in lower risk areas
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P-1b-29 Of the 134 households returning questionnaires, only 9 % had tested their homes for radon. As shown in Figure 3, 4.6 % had not tested, but had inquired about a test, while 86.4 % had neither tested nor inquired about the test.
Not tested, but inquired about test 4.6% House Tested 9.0%
86.4% Not tested, nor inquired about test Figure 3 - Percentage of Householders testing radon levels
Householder responses to questions about their previous knowledge of radon were similar, as shown in Figures 4 and 5, with an overwhelming majority claiming no knowledge of the risk of radon at all.
Informed 13.0%
Developer 10.8% Surveyor 15.1%
Mortgage Provider 6.5%
Not Informed 87.0%
No Advice 67.7% Estate Agents, Local Authority and Local Doctors were specified in the questionnaire, but scored zero
Figure 4 Householders informed about radon by developer
Figure 5 - Sources of general advice on radon
DISCUSSION There is sufficient building of new homes to justify provision of protective measures when the homes are built. The policy of requiring the installation of radon-proof membranes in all new homes in high risk radon areas has been shown to be cost effective and similar to other radon remediation initiatives in existing homes and workplaces, as demonstrated in Figure 6 (from Denman, Phillips and Tornberg, (16)). The analysis, however, ignores any possible failure rate of the membranes, and whether additional protection in the form of a fan is required. This latter, however, requires action by the householder to assess the level of radon, which the work in lower risk areas suggests does not happen. Investigation of these two aspects is on-going. New Homes in High Risk Current Domestic Completed Domestic Schools - total Schools - pupils only Schools - staff only NHS Workplace NRPB Dental 0
50
100
150
200
250
300
350
Total Cost per Man-Sv in Thousands of Pounds
Figure 6 - Comparison of Radon Mitigation Programmes in Northamptonshire
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P-1b-29 However, this work has shown that the UK policy in lower risk areas in Northamptonshire is ineffective as it relies on the knowledge and action of householders to test radon levels, and install a sump if a raised radon level is found. In addition, the knowledge base used in the 1992 guidance to define the lower risk areas was inaccurate, at least as far as one of the two estates we studied was concerned. If secondary protection is specified in lower risk affected areas, then significantly increased public awareness is required. In Northamptonshire, lack of awareness may be due in part to people moving into the new homes from outside the area, but low householder response to the risks of radon is a universal problem and Suess (17) notes that ‘the common apathy of the general public with regard to the indoor radon issue adds a special challenge to the effort to communicate risk information to the public.’. Alternatively, the installation of a radon membrane in all new homes, which does not rely on public awareness and action, could be adopted. During preparation of this paper, BRE published a revised version of their guidance, which was legally adopted on 14th January, 2000 (18).The guidance changes the protection specified in lower risk areas to installation of a membrane, rather than provision of sump. This eliminates any need for householder action to be effective, and so is a considerable improvement. However, it should be noted that provision of membranes will be less cost effective than in high risk areas, and may be up to twice as costly as our assessment for high risk areas. The installation of membranes in all homes in lower risk areas will also resolve the other finding of our work, that is, the mis-classification of high risk areas as lower risk areas. The new guidance has also thoroughly revised and updated the areas considered to be at risk, and the means of identifying them. The Guidance now uses the 1997 NRPB records and data from the British Geological Society on underlying rock types, both displayed in 1 km grid squares. For many of the squares, the Guidance indicates that the exact risk can only be determined by spending £30 +VAT for a BGS geological assessment report of the expected risk due to the underlying geology at the map reference of the property. Both estates we have studied are classified as low risk by the NRPB data, and the BGS data indicated that a BGS report was required. It remains to be seen if this more complicated mechanism eliminates the need to install membranes unnecessarily, thus improving cost-effectiveness; or increases costs by requiring most new homes to have an assessment, and then a membrane. In the case of the two estates, interpretation of geological maps show that Estate A is on a small outcrop of Northampton Sand, less than 0.5 km wide and 1 km long, while Estate B is on Cornbrash Clay. Northampton Sand is associated with the highest risk of raised radon levels in Northamptonshire, and clays with the lowest (19). This corresponds to the radon levels measured in this paper.
CONCLUSIONS There is sufficient new domestic building in the UK to achieve significant health gains by specifying protective measures. However, until recently the measures in lower risk areas, with 3 to 10 % of homes above the Action Level, relied on the householder being aware of the radon hazard and testing the level. In two estates in Northamptonshire it has been shown that house holder knowledge was minimal, and so the secondary protective provisions were totally ineffective and the effort in providing this protection was wasted. The recent revision to the BRE Guidance is therefore a major advance in ensuring public risk from radon is reduced. The guidance also provides up-to-date knowledge of location of Affected Areas with improved precision, but the mechanism for finding the risks of a specific location in a mixed geology area is complicated, and may discourage builders from using it.
ACKNOWLEDGEMENTS The authors are grateful to Roger Tornberg of Radon Centres for his advice on the type of remediation carried out in new and existing house, and his guidance on the implications of the revisions to the BRE guidance.
REFERENCES 1.
International Commission of Radiological Protection. The Health Effects of Inhaled Radon and its Progeny In Protection Against Radon-222 at Home and Work, Annuls of the ICRP, 23, 7-13 (1994).
2.
J.H.Lubin and J.D.Boice. Lung Cancer Risk from Residential Radon : Meta-analysis of eight Epidemiological Studies. Journal of the National Cancer Institute, 89(1), 49-57 (1997).
3.
S.Darby, E.Whitley, P.Silcocks, B.Thakrar, M.Green, P.Lomas, J.C.H.Miles, G.Reeves, T.Fearn and R.Doll. Risk of Lung Cancer associated with Residential Radon Exposure in South-West England : a case-control study. British Journal of Cancer, 78(3), 394-408 (1998).
4
P-1b-29 4.
P.A.Colgan and J.Guitiérrez. Cost Effectiveness of Reducing Radon Exposure in Spanish Dwellings. Journal of Radiological Protection, 16, 181-190. (1996).
5.
F.Marcinowski and S.Napolitano. Reducing the risks from radon. Air and Waste, 43, 955-962 (1993).
6.
J.O.Snihs. Swedish Radon Programme. Radiation Protection Dosimetry, 42, 177-184 (1992).
7.
E.G.Létourneau, D.Krewski, J.M.Zielinski and R.G.McGregor. Cost effectiveness of radon mitigation in Canada. Radiation Protection Dosimetry, 45, 593-598 (1992)
8.
C.A.Kennedy, A.M.Gray, A.R.Denman and P.S.Phillips. A Cost-effectiveness Analysis of a Residential Radon Remediation Programme in the United Kingdom. British Journal of Cancer 81(7) 1243-1247 (1999).
9.
National Radiological Protection Board. Human Exposure to Radon in Homes. Documents of the NRPB, 1(1). Chilton, NRPB (1990).
10.
National Radiological Protection Board. Radon Affected Areas, Derbyshire, Northamptonshire and Somerset. Documents of the NRPB, 3(4), Chilton, NRPB (1992).
11.
Building Research Establishment. Radon : Guidance on Protective Measures for New Dwellings. BRE Report BR211, BRE Publications, ISBN 1 86081 229 5 (1992).
12.
The Building Regulations. HMSO, London, UK (1991).
13.
E.J.Bradley, P.R.Lomas, B.M.R.Green, and J.Smithard. Radon in Dwellings in England : 1997 Review. National Radiological Protection Board Report R293, NRPB, Chilton, UK (1997)
14.
A.R.Denman and P.S.Phillips. A Review of the Cost Effectiveness of Radon Mitigation in Domestic Properties in Northamptonshire. J. Radiol. Prot.; 18(2), 119-124 (1998).
15.
A.R.Denman, J.Gulliver, C.A.Kennedy, D.Briggs and P.S.Phillips. The Impact of Occupancy Patterns on the Assessment of the Value of Domestic Radon Remediation Programmes in the UK. Proceedings of the 10th International Congress of the International Radiation Protection Association, May 14-19, 2000, Hiroshima. (2000).
16.
A.R.Denman, P.S.Phillips, and R.Tornberg. A Comparative Review of the Effectiveness of Radon Remediation Programmes in Hospitals, Schools, and Homes in Northamptonshire, UK. Proceedings of the 10th International Congress of the International Radiation Protection Association, May 14-19, 2000, Hiroshima.
17.
M.J.Suess. Health Criteria for Radon Indoors. Environmental Management and Health 6(2), 34-36 (1995).
18.
Building Research Establishment. Radon : Guidance on Protective Measures for New Dwellings 1999 Edition. BRE Report BR211, BRE Publications, ISBN 1 860813283 (1999)
19.
D.Sutherland and G.Sharman. Radon - in Northamptonshire ? Geology Today, 12(2), 63-67 (1996).
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