WNA’s comments on the ICRP draft report: “Radiological Protection against Radon Exposure (6 December 2011)
We are pleased to submit the WNA’s comments on the subject ICRP draft document.
We would like to offer a set of general comments on the report (see Attachment 1) and also, a list of specific comments (see Attachment 2) which show examples of where the general comments are particularly relevant in the report.
The WNA believes that this ICRP draft report has important implications for all stakeholders and while the report is a significant initial step, in our opinion, it would benefit from some further development followed by another round of consultation.
Thank you for this opportunity to provide our industry input on this draft document.
We look forward to the outcome of the current consultation process.
With kind regards,
Sylvain Saint-Pierre
Consultant for the WNA Working Group on Uranium Mining Standardization
ATTACHMENT 1- WNA General Comments on:
ICRP draft report “Radiological Protection against Radon Exposure”
(6 December 2011)
1. The overall report puts an emphasis on the coverage of existing exposure situations. As part of this, the coverage of radon in homes seems sufficient but the coverage of occupational exposure and workplaces needs to be further improved. The general approach shown on Figure 7 seems agreeable but the way occupational exposure and workplaces are addressed throughout the text does not seem sufficiently clear (e.g. see para 104-112, para 165-167, para 105 versus 166). In addition, the report would significantly benefit from further clarifications and improved detailed editing.
2. On radon risk and lung cancer based on the epidemiological approach, the “elephant in the room” is definitely smoking which is undoubtedly the major cause of lung cancer, and in fact, also of many other human health diseases. Indeed, Sarah Darby el al. in discussing the risk from radon in home suggest that the risk from exposure to radon in smokers is about 25 times the corresponding risk to non-smokers with the same exposure to radon. Indeed, the ICRP’s report No.115 notes that the risk of lung cancer from radon exposure is on the order of 20 times higher for smokers versus non-smokers. Given the very clear role of smoking in risk from exposure to radon, we suggest that the role of smoking and the interaction of radon and smoking require systematic discussion throughout the report.
A second key point – which is overlooked in the report - is the observation that smoking prevalence is in a clear decreasing trend in most populations across the world. Since smoking is by far the dominant cause of lung cancer, in the future, this trend will no doubt lead to a significant reduction in lung cancer risk.
Other key points include the following:
(a) ICRP has indicated it believes that the latest epidemiological results support an approximate doubling of radon risk in terms of detriment per unit of radon progeny exposure. Industry supports using the most recent epidemiological results, but notes several issues that need to be addressed transparently.
(b) Industry supports the continued use of a nominal approach to estimating risk (based on epidemiology) as a preferred basis for current policy making - provided that smoking prevalence is carefully accounted for. The characteristics of the underlying populations are important as the risk projection models in current use for radon are relative risk models. This importance is amplified for those characteristics – like smoking - which bear significantly on the risk outcomes.
(c) Building on the above, it is important to specify that the notion of ‘detriment adjusted nominal risk coefficient’ is for a mixed population of smokers and non-smokers (e.g. in para 34). We suggest that ideally, the detriment, should consider more explicitly (than through WT) current nominal values for current smoking prevalence. Given the decrease in smoking prevalence, such an assumption would remain conservative (i.e., more likely than not to result in some overestimate of risk as the result of risk actually arising from smoking being attributed to radon exposure).
(d) It is important to clearly differentiate and explain the notion of risk of lung cancer per unit of exposure (e.g. in terms of detriment per WLM) from the notion of dose conversion convention (DCC, in terms of mSv/WLM). It is emphasized that an increase of the former does not necessarily imply a corresponding increase of the latter, as other factors are involved. For example, a sensitivity analysis of DCCs as a function of smoking prevalence for different published epidemiological studies (see Figure 1), resulted in a median DCC of about 6 or 7 mSv/WLM for an underlying reference population with a nominal smoking prevalence of 30%. Based on available information, this value of smoking prevalence can be considered as a reasonable notional mixed population of smokers and non-smokers. In comparison, the current DCC is 5 mSv/WLM for workers.
(e) In consideration of the above, this suggests that a case for a change of DCC is not compelling at present.
Figure 1
Radon Dose Conversion Convention Ranges
[FIGURE SUBMITTED SEPARATELY]
Source: SENES 2011
3. On the shift of risk estimation method (for radon exposure) from the long-established epidemiological approach to a new dosimetric approach that remains to be thoroughly validated/calibrated, industry views the adoption of such a change as premature at this time for the following three reasons:
(i) Further validation/calibration is needed for the dosimetric model,
(ii) It is unclear that the dosimetric model adequately accounts for smoking,
(iii) There is a lack of field data on radon progeny aerosols and no widely accepted measurements protocols.
Overall, industry believes that more work is needed to validate/calibrate dosimetric models and to improve knowledge of radon progeny aerosol conditions in current workplaces – the latter data is needed to support dosimetric calculations. Industry strongly recommends deferring the adoption of the dosimetric approach until the needed work is completed.
Industry therefore views this proposed change of risk estimation method for radon exposure as a long-term goal. The following text amendment is therefore suggested for paragraph (171) with a view to realistically reflect the current situation:
(171)… epidemiological studies. As a long-term goal, the Commission is intending to recommend the use of reference biokinetic and dosimetric models for all other radionuclides (ICRP, 2011). The current dose conversion values may continue to be used until dose coefficients are available. We agree, with this latter statement that there is no urgency to change the current dose coefficients.
Considering the significant disparities in the outputs of the new dosimetric modelling approach relative to the epidemiological results [see the items ‘(a)’ and ‘(b)’ below], the questions of the ability of the dosimetric approach in adequately taking into account of smoking, and the key role of dose (conversion) coefficients in radon policy numerical criteria; we see merit in closer links and support between the ICRP Main Commission and its relevant Task Groups (TG81 and TG64) on the development of new dose coefficients and on their incorporation in the ICRP policies on radon. This should be complemented by sufficient stakeholder engagement for the subsequent adoption, by convention, of new dose coefficients. We understand that TG64 is properly equipped to advance scientific developments on this key issue. However, in due course before their adoption, it is very important that the practical suitability of these coefficients gets thoroughly verified for the purposes of their formal inclusion into the ICRP’s radon policies as well as for implementation by users.
Other key points include the following:
(a) On the validation/calibration of the two approaches and on adequately accounting for smoking using the dosimetric model, the report mentions (para 32) that the significant discrepancies in the output (by a factor of approximately 2 in the past) have been reduced but it is insufficiently clear if this apparent agreement is coincidental or not?
(b) In support of this view, we refer to a recent paper by Baias et al (2010) only shows a factor of two in Dose Conversion Factors (DCFs), an equivalent to DCCs, between non-smoker and smoker using the dosimetric model, whereas epidemiology suggests a larger factor of perhaps 10 or more – thus re-affirming that it is unclear if the dosimetric model adequately accounts for smoking or not. (See the right hand site data on Figure 1.) Baias’ dosimetric model output (DCFs) for non-smoker (NS) also falls approximately mid-range between the outputs corresponding to heavy long term (HLT) smokers and to heavy short term (HST) smoker – raising further concerns about the ability of current dosimetric models to account for smoking. Regarding non-smokers, it is also noted that the dosimetric results are about 7 times greater than the epidemiological results. It is therefore unclear if the discrepancy has been reduced or not (see para. 32). It should also be borne in mind that if the generally declining trend in smoking that is currently observed around the world is continued, the risk of lung cancer should in time also proportionally decline, and somehow, dose conversion coefficients also need to account for such a possible evolution.
(c) It should be borne in mind that disagreement between the two approaches can have key implications both at higher exposure levels for workers (that would receive say an exposure of 10 mSv/y or higher from radon) and at lower exposure levels for the public (that would receive say an exposure of 0.5 mSv/y or higher from radon associated with a planned exposure situation). In these cases, assuming that the dose estimates are first derived using a lower dose conversion factor, using a different factor that is about two times higher would result in new dose estimates equivalent to the worker dose limit (20 mSv/y, or 2 x 10 mSv/y) and the public dose limit (1 mSv/y, or 2 x 0.5 mSv/y), respectively. The difference in dose conversion factors or coefficients can possibly make a significant difference in terms of achieving compliance with regulatory dose limits.
(d) On the lack of relevant field data and measurement protocol, we would like to highlight that little work characterising radon progeny aerosols has been done over the last two decades; many changes to uranium industry and mining have taken place over the last 20 years; in the short term there is limited ability to collect the needed data; and there is currently no standard measurement protocol.
4. On occupational exposure to radon, throughout the document, uranium mining is singled out as one of the few occupational situations for which the more restrictive measures of planned exposure are to be applied – irrespective of the many other situations which can involve comparable (or even higher) exposure levels. This is potentially misleading and could give the impression that radon is only an occupational concern in uranium mining, which would serve to undermine the perceived need to take steps to assess and reduce radon concentrations in non-uranium mining workplaces. Among other, the uranium mining industry and the NORM industries should be considered in a similar manner, and managed as planned exposure situation. The same should apply to other work environments or workplaces considered as part of existing exposure situation but that need to be managed as planned exposure situation. Other key points include the following:
(a) The coverage of ‘occupational exposure’ as part of ‘existing exposure’ is particularly unclear and the rationale for covering it (‘occupational exposure’) differently as part of ‘planned exposure’ is also unclear.
(b) The notion of ‘worker exposures to radon considered as the responsibility of the operating management’ which relates to ‘occupational exposure’ also seems not sufficiently clear throughout the text.
ATTACHMENT 2 - WNA Specific Comments on:
ICRP draft report “Radiological Protection against Radon Exposure”
(6 December 2011)
The following specific comments show examples of where the general comments (GC) are mostly relevant in the report.
Executive Summary (ES)
ES, para (d):
· See GC2 plus GC2 (c) and (d) in particular.
ES, para (e):
· See GC 4.
ES, para (k):
· See GC 3.
ES, para (m), (p), (q), (r)
· See GC4 plus GC4 (a)(b) and (c) in particular.
Main Points
2nd and 3rd bullets:
· See GC2 plus GC2 (a), (b), (c) and (d) in particular.
5th, 9th, 11th and 12th bullets:
· See GC4
Body of the Report
Chapter 2
Chap 2, para. 32:
· See GC3 plus GC3 (a) and (b) in particular.
Chap 2, para 33:
· See GC2 plus GC2 (c) in particular.
Chap 2, para 33 and 35
· See GC2. The way smoking is covered in lines 852-858 differs from lines 884-888.
Chap 3, para 61
· See GC4
Chap 3, para 72
· See GC2
Chap3, para 73
· See GC2 plus GC2 (b) and (c) in particular.
Chap 3, para 105, 106
· See GC4 plus GC4 (b) and (c) in particular. Based on para 105 (…workplaces where radon exposure is ‘adventitious’ and more related to the location than the work activity…), it seems that most situations in workplaces are not considered as occupation exposure.
Chap 3, para 108, 109, 110, 111 and 112, Fig 7 (page 44)
· See GC4 plus GC4 (a)(b) and (c) in particular.
Chap 4, para 162 and 163
· See GC4 plus GC4 (a)(b) and (c) in particular. Unclear what differentiates para 162 from para 105.
Chap 4, para 166 and 167
· See GC4 plus GC4 (a)(b) and (c) in particular. Unclear what differentiates para 166 (…mines, caves, etc.,…) from para 105. Unclear in para 167 why measures that are analogous to those for the occupation exposure of workers under planned exposure situations should be applicable in full or in part ‘depending on the case’.
Chap 4, para 168, 169, 170
· See GC4. Among other, the uranium mining industry and the NORM industries should be considered in a similar manner, and managed as planned exposure situations. The same should apply to other work environments or workplaces considered as part of existing exposure situation but that need to be managed as planned exposure situation.
Chap 4, para 171
· See GC3 plus GC3 (a), (b), (c) and (d) in particular. Industry therefore views this proposed change of risk estimation method for radon exposure as a long-term goal. The following text amendment is therefore suggested for paragraph (171) with a view to realistically reflect the current situation:
(171)… epidemiological studies. As a long-term goal, the Commission is intending to recommend the use of reference biokinetic and dosimetric models for all other radionuclides (ICRP, 2011). The current dose conversion values may continue to be used until dose coefficients are available.
Considering the significant disparities in the output of the new dosimetric modelling approach relative to the epidemiological results [see the items ‘(a)’ and ‘(b)’ below], the questions of the ability of the dosimetric approach in adequately taking into account of smoking, and the key role of dose (conversion) coefficients in radon policy numerical criteria; we see merit in closer links and support between the ICRP Main Commission and its relevant Task Groups (TG81 and TG64) on the development of new dose coefficients and on their incorporation in the ICRP policies on radon. This should be completed by sufficient stakeholder engagement for the subsequent adoption, by convention, of new dose coefficients. We understand that TG64 is properly equipped to advance scientific developments on this key issue. However, in due course before their adoption, it is very important that the practical suitability of these coefficients gets thoroughly verified for the purposes of their formal inclusion into the ICRP radon policies as well as for implementation by users.