A Comparative Study of Public Perception of Risks from a Variety of Radiation and Societal Risks A.R. Denman, S. Parkinson, C.J. Groves-Kirkby Medical Physics Department, Northampton General Hospital, Cliftonville, Northampton, NN1 5BD, UK E-Mail: [email protected]T Abstract. Anecdotal evidence suggests that public perception of radiation risks does not match current scientific opinion. For example, while there is considerable opposition to mobile phone transmitters, patients attending hospitals expect and demand X-Rays as part of their diagnosis and treatment. As another example, only a limited proportion of householders follow National Radiological Protection Board (NRPB) advice to protect their houses from radon. To judge whether public perception matches current scientific opinion, a sample of the general public were asked to fill in a written questionnaire to rank twenty different risks. These included the risks associated with medical X-rays, radon, nuclear discharges, mobile phones, smoking, recreational activities, travel, accidents at home and hazardous occupations. Sufficient replies were received to differentiate between results from schoolchildren, undergraduate and post-graduate students, the adult public and health workers. Although there was a wide variation in perception of risk within each group, it was possible to identify average trends. There was a clear trend with age in the perceived risk from driving, the average ranking being lowest for children and highest for adults. On average, all groups underestimated the risks associated with medical exposures, and in particular, did not rank CT scans as significantly more risky than other X-rays. Hospital workers ranked medical X-Ray risks higher but still underrated the CT risk. Respondents from Northamptonshire rated radon as a significant risk suggesting that they were aware of the risk. Therefore, there must be other barriers to taking action to reduce radon risk. In general, radon was considered to be more of a risk at work than at home – the reverse of the actual relative risk. Despite the lack of evidence of the risks of mobile phones, respondents' perception was that there was a moderate risk, with transmitters considered riskier than handsets. 1. Introduction Patients attending UK hospitals expect and demand X-Rays, themselves potentially harmful, as part of their diagnosis and treatment. In contrast, there is ongoing public concern and debate about the siting of mobile phone transmitters on school premises, and on many occasions our Department has been contacted by the public and by hospital workers about the health risks associated with mobile phone transmitters. Northamptonshire, UK, is a radon Affected Area, but to date only around 37 % of residents have tested their homes for radon levels and only 10 % of those who have discovered raised radon levels have taken remediatory action. Duckworth et al. [1] suggest that those who do not take action to reduce radon levels (the majority) have a lesser of perception of radon risk. The foregoing, and other, anecdotal evidence suggests that public perception of radiation risks does not match current scientific opinion. To judge whether these observations correctly reflect the general perception of various health risks, a written questionnaire was devised, asking people to rank twenty different risks relating to radiation and to potentially hazardous activities. These included the risks associated with medical X-rays and Computerised Tomography (CT) scans, radon at work and in the home, nuclear discharges, mobile phones, smoking, recreational activities such as skiing, football and hang-gliding, travel, accidents at home and the risks of occupations such as deep-sea fishing and mining. There is an increasing use of medical X-Rays, in particular CT scans, for diagnosis. Although the average dose to the general public in the UK from medical X-Rays rose only slightly over the 10 years to 1997, from 0.29 mSv per individual to 0.33 mSv per individual, the contribution to this dose from CT examinations more than doubled, to 40% of the total, over the same period [2]. Use of medical X- Rays is significantly higher in certain other developed countries, such as Japan and the USA. Medical X-Ray examinations deliver a wide range of doses to patients; the four examples chosen for the risk questionnaire reflect this range, the estimated average effective doses to patients being shown in Table I. However, while there have been many studies on the magnitude and variation of resultant doses to the patients, few studies have investigated patients' knowledge of associated risks, despite moves to ensure that patients give informed consent for such procedures. 1
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A Comparative Study of Public Perception of Risks from a Variety of Radiation and Societal Risks
A.R. Denman, S. Parkinson, C.J. Groves-Kirkby
Medical Physics Department, Northampton General Hospital, Cliftonville, Northampton, NN1 5BD, UK
Abstract. Anecdotal evidence suggests that public perception of radiation risks does not match current scientific opinion. For example, while there is considerable opposition to mobile phone transmitters, patients attending hospitals expect and demand X-Rays as part of their diagnosis and treatment. As another example, only a limited proportion of householders follow National Radiological Protection Board (NRPB) advice to protect their houses from radon. To judge whether public perception matches current scientific opinion, a sample of the general public were asked to fill in a written questionnaire to rank twenty different risks. These included the risks associated with medical X-rays, radon, nuclear discharges, mobile phones, smoking, recreational activities, travel, accidents at home and hazardous occupations. Sufficient replies were received to differentiate between results from schoolchildren, undergraduate and post-graduate students, the adult public and health workers. Although there was a wide variation in perception of risk within each group, it was possible to identify average trends. There was a clear trend with age in the perceived risk from driving, the average ranking being lowest for children and highest for adults. On average, all groups underestimated the risks associated with medical exposures, and in particular, did not rank CT scans as significantly more risky than other X-rays. Hospital workers ranked medical X-Ray risks higher but still underrated the CT risk. Respondents from Northamptonshire rated radon as a significant risk suggesting that they were aware of the risk. Therefore, there must be other barriers to taking action to reduce radon risk. In general, radon was considered to be more of a risk at work than at home – the reverse of the actual relative risk. Despite the lack of evidence of the risks of mobile phones, respondents' perception was that there was a moderate risk, with transmitters considered riskier than handsets.
1. Introduction
Patients attending UK hospitals expect and demand X-Rays, themselves potentially harmful, as part of their diagnosis and treatment. In contrast, there is ongoing public concern and debate about the siting of mobile phone transmitters on school premises, and on many occasions our Department has been contacted by the public and by hospital workers about the health risks associated with mobile phone transmitters. Northamptonshire, UK, is a radon Affected Area, but to date only around 37 % of residents have tested their homes for radon levels and only 10 % of those who have discovered raised radon levels have taken remediatory action. Duckworth et al. [1] suggest that those who do not take action to reduce radon levels (the majority) have a lesser of perception of radon risk. The foregoing, and other, anecdotal evidence suggests that public perception of radiation risks does not match current scientific opinion.
To judge whether these observations correctly reflect the general perception of various health risks, a written questionnaire was devised, asking people to rank twenty different risks relating to radiation and to potentially hazardous activities. These included the risks associated with medical X-rays and Computerised Tomography (CT) scans, radon at work and in the home, nuclear discharges, mobile phones, smoking, recreational activities such as skiing, football and hang-gliding, travel, accidents at home and the risks of occupations such as deep-sea fishing and mining.
There is an increasing use of medical X-Rays, in particular CT scans, for diagnosis. Although the average dose to the general public in the UK from medical X-Rays rose only slightly over the 10 years to 1997, from 0.29 mSv per individual to 0.33 mSv per individual, the contribution to this dose from CT examinations more than doubled, to 40% of the total, over the same period [2]. Use of medical X-Rays is significantly higher in certain other developed countries, such as Japan and the USA. Medical X-Ray examinations deliver a wide range of doses to patients; the four examples chosen for the risk questionnaire reflect this range, the estimated average effective doses to patients being shown in Table I. However, while there have been many studies on the magnitude and variation of resultant doses to the patients, few studies have investigated patients' knowledge of associated risks, despite moves to ensure that patients give informed consent for such procedures.
Table I. Estimated Average Effective Doses from X-Ray Examinations at Northampton General Hospital, UK
Examination Effective Dose in mSv Dental Intra-Oral 0.002
Chest 0.02 Lumbar Spine 1 Abdomen CT 8
A further concern about the increased use of medical X-Rays was whether the professionals, i.e. doctors and radiographers, providing advice on the risks and making judgements on the value of the proposed examinations, were themselves aware of the risks involved, and in particular whether they appreciated the much higher doses delivered in CT examinations. To investigate this, staff in the X-Ray Department were asked to complete the questionnaire.
Radon gas contributes approximately 50 % of the background radiation dose received by UK residents. Northamptonshire was declared a radon Affected Area in 1992 [3], and the dose from radon to the local population could therefore be significantly higher than average. Even in a radon Affected Area, the radon levels in groups of houses follow a lognormal distribution, so that most houses have normal levels, while a modest fraction (around 6.3 % in Northamptonshire) will have significantly raised levels. There have been a number of campaigns to raise awareness and to encourage householders both to test their homes for radon and, where necessary, to carry out remedial work to reduce levels. This can be done at moderate cost, and a programme to find and remediate all homes in Northamptonshire can be justified in terms of both health benefit and cost-effectiveness [4]. However, at the time of our questionnaire, only 37 % of houses in Northamptonshire had been tested [5] and only 10 % of householders in the county discovering raised levels had remediated their homes [6]. A question about the relative risk of radon was therefore included, and the questionnaire was distributed both within Northamptonshire, where radon had been given local publicity, and in other parts of the UK (Surrey and Newcastle upon Tyne) where there is no radon problem.
Further, in testing National Health Service premises for radon, it was clear to one of the authors that, while staff were anxious that the workplace should be checked for radon, they were generally reluctant to worry about radon at home. The questionnaire was therefore designed to include questions regarding radon both at home and work.
There have been a number of Risk Perception Studies addressing environmental issues, for example, radon at home, but most of these have considered a single risk and the perception of that risk. This study aimed to compare risks, partly to see how the public compared radiation risks to other more well-known risks, and partly to see if the risk-ranking influenced public decision-making about risk avoidance.
2. Method
A set of 20 risks were identified, 10 related to radiation and 10 associated with other, non-radiation based, lifestyle activities etc., as shown in Table II. The selected risks were either those encountered in everyday life or were at least familiar to respondents, and were risks for which scientific evaluations of the risk magnitude were available. A number of risks, such as climbing Mt. Everest and Hang Gliding, as well as working as Coal-Miners or Deep-Sea Fishermen were chosen because such activities are known to be risky, rather than in the expectation that any of the respondents had experienced them.
Questionnaires were distributed in paper form during late 2002 and early 2003 to a number of respondent groups. These groups, dentified in Table III, were chosen to provide a set of respondents exhibiting a range of ages and educational status (school-children, undergraduates, postgraduates) and occupations (including staff from the Hospital X-Ray Department) as well as the general public living
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in, and outside, radon Affected Areas. Respondents were asked to rank the 20 risks in order, with 1 as the highest and 20 as the lowest and were also asked to provide limited personal, but anonymous, information, including age, gender, location of residence (by UK postcode) and occupation.
Table II. Fatality Risks evaluated in Questionnaire
Radiation Risks Other Risks Annual Risk from Radon at home at UK Action Level of 200 Bq·m-3
Annual Risk from working as a Coal Miner
Annual Risk from Radon at work at UK Action Level of 400 Bq·m-3
Annual Risk from working as a Deep-Sea Fisherman
One Abdomen CT Scan One Vaccination One Lumbar Spine X-Ray Annual Risk from Hang Gliding One Chest X-Ray A Single Ascent of Mt. Everest One Dental X-Ray Annual Risk from Recreational Skiing Annual Risk to People Living near Sellafield Annual Risk from Accident at home Using a Mobile Phone for calls, 2 hours a day Annual Risk from Driving Annual Risk from Mobile Phone Transmitter at the end of the garden Annual Risk of Playing Football at School
Annual Risk from working as a Airline Pilot Smoking 10 cigarettes a day
Table III. Groups completing the Questionnaire
From Northamptonshire Other Areas (not Affected by Radon) Year 9 Secondary School Children General Public Undergraduates Office Workers, Newcastle Postgraduates Undergraduates Hospital Staff Postgraduates General Public
The results were entered into a spreadsheet for analysis. The average rank given to each risk was obtained for both the various respondent groups and for the whole sample, and the group averages were then ranked from 1 to 20. The differences between groups were tested by comparing the distribution of scores in each group using the paired t-test, and using the 95 % confidence interval.
The scientific estimation of risks was obtained from a number of sources – general risks from the Royal Society [7] and elsewhere [8]; and ionising radiation risks from the National Radiological Protection Board (NRPB) [9]. The risk estimates for medical exposures were modified to match the average exposures used at Northampton General Hospital, while the risk estimation for radon at work was taken from previous research by Denman et al. [10].
General scientific opinion is that the risks associated with mobile phones have not yet been proven. This is in contrast to the other risks listed. As a result the mobile phone risks were rated at the bottom of the order of scientific opinion, with the phone above the transmitter, as it delivers a higher power direct to the head, so that, if there were a risk, the effect would be expected to be greater. The scientific ranking of risks considered in the study is shown in Table IV.
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Table IV. Scientific Ranking of Risks
Rank Risk of Death Chance of Death Per Million
1 Single Ascent of Mt. Everest 130,0002 Annual Risk from Smoking 10 cigarettes a day 5,0003 Annual Risk for Deep Sea Fisherman 840 4 Annual Risk from Radon gas exposure at home at Action Level of 200 Bq·m-3 415 5 Risk from one Abdomen CT 400 6 Annual Risk from Radon Gas exposure at work at Action Level of 400 Bq·m-3 300 7 Annual Risk from Hang Gliding 260 8 Annual Risk for Coal Miner 145 9 Annual Risk to an Airline Pilot doing 50 hours flying a month at 30,000 ft 143
10 Annual Risk from Recreational Skiing 120 11 Annual Risk from Accident at Home 67 12 Annual Risk from Driving 67 13 One Lumbar Spine X-Ray 50 14 Annual Risk from playing football at School 12 15 Annual Risk to people living near Sellafield from radioactive discharges 7 16 Risk from one Vaccination 1.0 17 Risk from one Chest X-Ray 1.0 18 Risk from one Dental X-Ray 0.1 19 Using a Mobile Phone for calls, 2 hours a day Not Proven20 Annual Risk from Mobile Phone Transmitter at end of garden Not Proven
3. Results
3.1. General Observations
172 Questionnaires were returned and used in the analysis. A further 3 (1.7 %) were rejected because they were inadequately filled in. The returns included 58 'Year 9' Northamptonshire school-children (age 13); 45 University students; and 82 adults. Of the latter, 52 adults lived in Northamptonshire, and 30 came from other parts of the UK; primarily Newcastle and Surrey. The student sample consisted of 30 undergraduates and 15 undergraduates. Of the 52 adults living in Northamptonshire, 25 worked in the hospital.
A considerable range in ranking by individuals was observed within each group, a typical score distribution for children's perception of the relative risk from two sources, coal-mining and having a vaccination, being shown in FIG. 1. Although there is considerable variation, conclusions can still be drawn, this example clearly showing that, in general, children rank coal mining as presenting a far higher risk than having a vaccination.
Consideration of the average ranking of the different risks showed that all groups over-estimated the risks from living near Sellafield, mobile phones and transmitters, working as a coal miner, and driving. All groups under-estimated the risks from playing football at school, climbing Mt. Everest and from most medical X-Rays. Accidents at home, hang gliding and skiing, and vaccination were correctly ranked.
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FIG. 1. Example of range of individual risk perception for two different risks: results from school-children
All groups rate the risk of smoking high. Children rank smoking somewhat lower, as the 5th highest risk, and difference between the perceptions of children and of the other groups is statistically significant at the 95 % level.
3.3. Driving
The average perception of risk from driving is displayed in FIG. 2, where the perceived risk is plotted against the actual risk. There is an interesting trend with age and experience, but only the difference between children and adult responses is statistically significant at the 95 % level.
FIG. 2. Perception of risk of driving
0 5 10 15 20
Average Rating from Questionnaire Returns (1 highest; 20 lowest)
0
5
10
15
20
Expe
rt R
atin
g
Children Undergraduates Postgraduates Adults
Risk Underestimated
Risk Overestimated
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3.4. Mobile Phones
As already indicated, respondents perceived a non-zero risk from mobile phones and transmitters, in contrast to expert scientific opinion which suggests that there is no known mechanism for the radiation to cause adverse effects. Scientifically, mobile phone radiation is currently ranked only as a 'Possible Carcinogen', since the results of clinical studies are variable - most say that there is no risk. If there is a risk, albeit small, then the phone next to the user's ear is much more hazardous than the transmitter at the end of the garden or in school premises. However, respondents ranked the mobile phone risk at 14, lower than the risk from transmitters at 13.
3.5. Medical X-Rays
The X-Ray examinations chosen for the questionnaire represent a wide range of doses to the patient. The lowest, a dental intra-oral, is equivalent to a few hours of natural background radiation, while the highest, the abdomen CT, delivers a dose equivalent to around 4 years of the natural background. This wide variation was not recognised by the respondents, who ranked all four examinations as having similar risks, as can be seen in FIG. 3.
FIG. 3. Perception of risks from medical X-rays
0 5 10 15 20
Average Rating from Questionnaire Returns (1 highest; 20 lowest)
The risk from the abdomen CT examination was significantly underestimated, being ranked 15 to 17 by each group, compared to the actual ranking of 4. 25 Hospital staff with radiation safety training, including Radiologists, Radiotherapists, Radiographers and Physicists, also answered the questionnaire. They rated CT risk higher and ranked it as 12, (statistically significantly different from other group responses at the 95 % confidence level). However, this ranking was still well below the actual ranking.
3.6. Radon
FIG. 4 summarises radon risk perception, with rankings for both home and workplace. Most groups ranked radon as a moderate risk, except the schoolchildren, who rated radon as a high risk. This difference was statistically significant. All groups outside the Hospital rated the risk from radon in the workplace as being higher than the risk in the home, when the reverse is in fact the case. Hospital staff, on the other hand, rated the risk in the home higher than the risk in the workplace. This was no doubt as a result of attending talks, and participating in research conducted in both home and workplace by our research group. There was no statistical difference in the ranking of radon risk between the non-Hospital adult group living in Northamptonshire and those living elsewhere in the UK where radon is not a problem. Moreover, there was a broad spread of risk perception in both groups, with rankings from 2 to 18.
This study has shown that children rank a number of risks differently from other groups. Besides driving, children rate the risks of smoking, accidents at home and climbing Mt. Everest lower than do adults. A pilot study of 13-year-old children in a rural comprehensive school in Oxfordshire found that children have a concept of risk as danger, but lack the concepts of chance and risk [11]. However, apart from smoking, our study showed no difference between adults and children in the perception of risks involving chance, such as radiation risks. Does this suggest the people in general do not understand the concept of chance?
4.2. Gender-Based Perceptions
Park et al. [12] noted the women had higher levels of societal concern than men across the four health issues they studied: radon, AIDS, heart disease and water contamination. The present study was not designed to give an estimate of the perception of absolute risk, but there are some differences between the risk perceptions of males and females. Females rated the risks from vaccination, from accidents at home, and from smoking higher than did males, while males rated the risks from radon at home and at work, and from climbing Mt. Everest, higher than did females.
4.3. Driving
The high rating given to the risks of driving contrasts with the increasing use of the car in the UK. Joshi et al. [13] suggest that road users in Oxford were paying more attention to near misses with less vulnerable road users (i.e. those who could harm them), than they do to near misses with more vulnerable road users (i.e. those whom they could harm.). This study suggests that the perception of risk from driving increases with age. Females also rate the risk from driving higher than males in this study.
4.4. Mobile Phones
It is clear that the general public do not share current scientific opinion that mobile phones are safe, but paradoxically the public are more concerned about transmitters than the phones themselves, This may be because transmitters are so visible. The questionnaire was circulated after the Stewart report [14] recommended the adoption of the Precautionary Principle when approaching mobile phone
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radiation safety. It is hoped that parallel research will identify whether the adoption of the Precautionary Principle has increased public concern or not.
4.5. Medical X-Rays
Our study showed that Health Service staff involved in radiation treatment or diagnosis had a better idea of the range of risks of medical diagnostic exposures than did the general public. This contrasts with the concerns expressed by Shiralkar et al. [15], who studied the perceptions of Senior House Officers, Registrars and Consultants, i.e. staff who request X-Rays. In contrast, the present study looked at Radiology staff, whose responsibility lies in justifying and agreeing to such requests, and who therefore should have a higher level of knowledge. The appropriate UK Regulations [16] expect Requesters (known as Referrers in the Regulations) to have some knowledge, but the Practitioners, who justify and agree to conducting the X-Rays, to have a higher level of knowledge. Not withstanding this, it is of concern that Radiology responders in our study underestimate the risks from CT, albeit to a lesser extent. Do Practitioners with a lower perception of risk approve more requests for CT examinations? While CT examinations are used on more seriously ill patients, this may not be a concern, but as CT is rolled-out to more patients, because modern 16-slice CT machines are faster and more precise, there is a concern that it may be used inappropriately.
Vehmas [17] studied Radiologists in Finland and found a range of perception of the risks of Barium Enema examinations, and of the benefits of radiation protection. Surprisingly, those with a higher perception of risk conducted examinations that gave higher dose to their patients. Female Radiologists had an increased average perception of risks than their male counterparts. Although our study had a limited numbers of respondents, it showed a wide range of risk perception for CT examinations (from 2 to 19), and also a modestly higher, but not statistically significant, average risk perception by female staff than by their male colleagues.
There is a movement to give patients more information about medical examinations and treatment, so that they can give informed consent to the proposed interventions. Guidance to patients and the general public has suggested that it would be best to explain risk in terms of the time exposed to natural background radiation – a matter of minutes for a dental X-Ray, and 4 years for the abdomen CT. Corbett [18] has also studied patient perception of the risk from medical X-rays, using a questionnaire answered by patients undergoing barium enema and lumbar spine examinations. His work showed that patients do not understand the concept of background radiation and some think that Ultrasound and Magnetic Resonance Imaging involve ionising radiation, and the CT does not.
4.6. Radon
The perceptions of radon risks in the home found in the present study confirm the work of Duckworth et al. [1] in their study of rural USA, that the perception of risk from radon is generally underestimated. In addition, our work shows a higher perception of risk from radon in the workplace. As noted above this does not match reality, as radon levels are generally lower during the day when most people are at work, and people spend more time at home than at work. The reason for this difference is beyond the scope of this study, but may be due to the fact that if the risk is at work then it is someone else's responsibility to do something about it, or because an Englishman's home is his castle, or it may be because the higher Action Level applied in the workplace looks, at first glance, as if lower standards are being applied.
The lack of any difference between the perceptions of adults within and outside radon Affected Areas is a concern. It implies that efforts to raise the profile of the risks of radon in the home in the UK to date have had no significant effect on perception, and therefore, presumably, on the likelihood of householders taking action. Recently, the Department for Environment, Food and Rural Affairs (DEFRA) have launched a programme targeting local communities aimed at increasing the public response to radon. This has yet to be implemented in Northamptonshire. The one group with an increased perception of the risk of radon are schoolchildren, which may bode well for the future.
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Bradley surveyed people in the South West of England who had measured radon levels but had not remediated their homes [6], noting that 50 % gave the perception that radon was not a risk as a reason for not taking action. Cost of remediation was also a major factor. The findings in our study, showing a very broad range of perception, are compatible with Bradley’s work. The wide spread of perception is compatible with the hypothesis that only those who conceive of radon as a significant risk take action. Further, recent work from our group has shown that those who have remediated to date are among those who are least at risk, because they are older, have fewer children, and do not smoke [19]. The crucial problem, then, in reducing the risks to the general public from radon in their homes, is how to raise risk perception in that part of the population who have not yet taken action.
5. Conclusions
The study showed that patients underestimated the risks from medical X-Ray examinations. In particular, patients had no concept of the wide range of doses that such examinations could deliver, or that the doses from CT scanners were significantly higher. The perception of hospital staff trained in radiation safety was closer to expert scientific opinion, but they too underestimated the risk from CT. There was also a wide range of perceptions in this group. As such staff often counsel patients about the value and risks of the use of X-Rays, they may well be underpaying such risks. This has implications for training radiology and Radiography staff, particularly as the use of CT is continuing to increase.
The study of risk perception of domestic radon suggests that the public, on average, modestly underestimate of the risks, but there is a very wide range of perceptions. This is likely to be a reason why only a limited number of people organise the testing and remediation of their homes. Despite the UK programme to advertise the risks of radon in Affected Areas, there was no difference in the perception of risks between those living in radon Affected Areas, and those elsewhere. This, and the low percentage of people remediating their homes, have significant implications for future public health policy in this area, particularly as recent work has shown that those who have remediated to date are among those who are least at risk [19].
Overall, this study has confirmed the contentions of previous researchers, such as Kletz [20] and Sjöberg [21], who have suggested that the public and scientists look at risks differently, and have different priorities.
6. Acknowledgements
The authors gratefully acknowledge the work of several colleagues and friends, including Alex Pearce, Professor Paul Phillips, Dr. Carole Phillips, Dr Donald Peach, Cath Chisholm and Anne Richardson, for their efforts in distributing and collecting the questionnaires.
7. References
1. Duckworth, L.T., Frank-Stromberg, M., Oleckno, W.A., Duffy, R., Burns, K., Relationship of perception of radon as a health risk and willingness to engage in radon testing and mitigation. Oncology Nursing Forum, 29:1099-1107, (2002).
2 . Hart, D., Wall, B.F., Radiation exposure of the UK population from medical and dental X-ray examinations. National Radiological Protection Board Report NRPB-W4. NPRB, Chilton, Oxon, UK. (2002)
4. Denman, A.R., Phillips, P.S., A review of the cost-effectiveness of radon mitigation in domestic properties in Northamptonshire. J. Radiol. Prot. 18:119-124 (1998).
5. Green, B.M.R., Miles, J.C.H., Bradley, E.J., Rees, D.M., Radon Atlas of England and Wales. National Radiological Protection Board Report NRPB-W26. NPRB, Chilton, Oxon, UK (2002).
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6. Bradley, E.J., Responses to radon remediation advice. Proc. 9th Int. Congress International Radiation Protection Association, 4:798-800 (1996).
7. The Royal Society Study Group, Risk : Analysis, Perception and Management. The Royal Society, London, UK ISBN 0 85403 467 6, (1992)
8. Wilson, R., Crouch, E.A.C., Risk-Benefit Analysis (2nd edition). Harvard University Press, Harvard, USA. ISBN 0 674 00529 5 (2001).
9. National Radiological Protection Board, Living with Radiation (5th edition). NRPB, Chilton, Oxon, UK. ISBN 0 85951 419 6 (1998).
10. Denman, A.R., Barker, S.P., Parkinson, S., Marley, F., Phillips, P.S., Do the UK workplace radon action levels reflect the radiation dose received by the occupants? Journal of Radiological Protection, 19:37-43 (1999).
11. McConnell, E., How do young people assess risk? Results of a pilot project. 1st Health Protection Agency Conference, University of Warwick; 16 September 2003.
12. Park, E., Scherer, C.W., Glynn, C.J. Community involvement and risk perception at personal and societal levels. Health, Risk and Society, 3:281-292, (2001).
13. Joshi, M.S., Senior, V., Smith,G.P., A diary study of the risk perceptions of road users. Health, Risk and Society, 3:261-279, (2001).
14. Independent Expert Group on Mobile Phones Sir William Stewart (Chairman), Mobile Phones and Health: A report from the Independent Expert Group on Mobile Phones, Chilton, IEGMP Secretariat, (May 2000).
15. Shiralkar, S., Rennie, A., Snow, M., Galland, R.B., Lewis, M.H., Gower-Thomas, K., 2003 Doctors' knowledge of radiation exposure : questionnaire study. Brit. Med. J., 327:371-2, (2003).
16. Dept. of Health. The Ionising Radiation (Medical Exposure) Regulations 2000. Statutory Instrument 1059. ISBN 0-11-099131-1, HMSO, London (2000).
17. Vehmas, T., Do radiologists' radiation-related opinions predict their fluoroscopy doses. Bri. J. Radiology, 76:653-655, (2003).
18. Corbett, R.H., What do patients really know or want to know about X-rays? Proceedings of 10th International Congress of the International Radiation Protection Association, Hiroshima, Japan, 14-19 May, 2000.
19. Denman, A.R., Groves-Kirkby, C.J., Phillips, P.S., Tornberg, R., Using the European Community Radon Software to estimate the individual health benefits of a domestic radon remediation programme. Submitted to J. Radiol. Protect., (2003).
20. Kletz, T.A., Risk – two views : the public's and the expert's. Disaster Prevention and Management, 5:41-46, (1996).
21. Sjöberg, L., 2002 The allegedly simple structure of experts' risk perception : an urban legend in risk research. Science, Technology and Human Values, 27:443-459, (2002).
