|CNSC Review of ICRP Draft Report for Consultation: Lung cancer risk from radon and progeny
Overall Canadian Nuclear Safety Commission (CNSC) staff has reviewed the draft ICRP document “Lung cancer risk from radon and progeny” and have generally found it to be comprehensive and objective.
However, our major criticism is that we find the scientific evidence for increasing the risk factor is not convincing enough. The Czech and French miners, upon which the estimates are based represent a very small fraction (12%) of the total miner cohort to base such a drastic change to a detriment adjusted nominal risk coefficient of 5 x 10-4 per WLM on.
In light of the above, the decision to double the value calculated in ICRP seems premature.
481 & 500 These lines are redundant. Recommend the following: Table 2.1 summarizes 20 case-control studies published between 1990 and 2006. More extensive details are available elsewhere (UNSCEAR, 2009).
510 Cancer diagnosis
530 Residence with high radon concentrations over 200 Bq/m3 seems odd. Define high radon concentrations since we question that 200 Bq/m3 is “high”; especially since Canadian guideline is 200 Bq/m3
533 Living in relatively high levels of exposure, above 400 Bq/m3. Same issue as in line 530. Need to define high since in line 530 you say 200 Bq/m3 is high and in line 533, you say 400 Bq/m3 is relatively high.
677 Attained age had a significant modifying effect on ERR/100 WLM, with risk decreasing with increasing attained age. Age at exposure was not an important effect modifier. Lubin et al, 1994 found that the ERR/100 WLM declined with increasing age (attained) from age 40 to age 80. The effect was observed in all but one of the 11 cohorts. The risk did not vary consistently with age at first exposure.
686 Prefer to use Lane et al, 2010 reference if possible (Lane RSD, Frost SE, Howe GR, Zablotska LB. Mortality (1950-1999) and cancer incidence (1969-1999) in the cohort of Eldorado uranium workers. Rad Res 2010;Available from: DOI 10.1667/RR2237.1.) since this has been accepted for publication in Radiation Research. The Howe, 2006 was a CNSC Research and Support Program final report. Refinement to our analysis has improved the study since 2006. Also note that the Eldorado study includes about 3,000 Port Hope radium and uranium refining and processing workers.
706 & 709 ERR per 100 WLM
725 See comment regarding age at exposure. Howe, 2006/Lane et al, 2010 use attained age, not age at exposure as an effect modifier.
730 An inverse exposure-rate effect is not seen at low levels of cumulative WLM exposure, or with improved, individual dosimetric data (Howe, 2006/Lane et al., 2010). In our updated Eldorado analysis (Beaverlodge, Port Radium, Port Hope), exposure rate (<0.5, 0.5-1.0, 1.0-3.0, 3.0-5.0, 5.0-15.0, 15.0 + WL) provided a further significant improvement in the fit (p=0.001) again with the ERR showing monotonically decreasing values with increasing exposure (refer to Table 4.5 in Howe, 2006).
Refer to Table 4 in Lane et al, 2010. Adding exposure rate using the 6 exposure rates defined about further significantly improved the fit (p=0.001) with ERR for mortality decreasing monotonically with increasing exposure rate.
753 Note that attained age of 55-64 years was used in NRC, 1998, not age at exposure (also attained age in line 766).
764 Table 3.2. The mean WLM for Beaverlodge based on 279 lung cancer deaths was 85 WLMs (Lane et al, 2010). The reference to 23 WLMs comes from Howe, 2006 which is not correct.
764 Table 3.2. We assume this comes from the original Ontario miners study since this study is in the process of being updated (we just started linking it to mortality/incidence data in September). I recommend using the original reference (Kusiak et al, 1993) not UNSCEAR 2009.
772 Newfoundland fluorspar miners
782 Villeneuve et al, 2007a noted the ERR/100 WLM was 0.42 and 0.48 for never and ever smokers, respectively; however, this difference wasn’t significant (p=0.82). However, that ERR/100 WLM increased with increasing number of cigarettes smoked daily. Specifically the ERR/100 WLM was 0.42 for those who never smoked and was 0.94 for those who smoked at least 30 cigarettes a day (p=0.04).
815 Villeneuve et al, 2007b note that although previous analysis (Villeneuve & Morrison, 1997) of the Newfoundland fluorspar miners cohort found elevated coronary heart disease mortality among those with higher cumulative radon exposure, the recent analysis found no trend or evidence between cumulative radon exposure and relative risk of CHD mortality (p=0.63). These findings were consistent with recent reports of Wismut miners (Kreuzer et al, 2006).
849 What does In outline mean in this sentence?
937 LEAR can vary from about 3 to 7 x 10-4 per WLM depending on the model used. These results illustrate the sensitivity of the estimate to the choice of the model and reinforced ICRPs reference for models derived from pooled analysis. Other LEAR calculations demonstrate the sensitivity of estimates to background rates.
In light of this statement above, the jump to the conclusion in line 937 seems peculiar and quick in which ICRP concludes that a LEAR of 5 x10-4 per WLM should now be used as the nominal probability coefficient for radon and radon progeny induced lung cancer. Table 4.1 range is 2.7 -5.3.
Appendix B In regards to the dosimetry section. Overall this is a comprehensive review of the developments and results in radon and thoron dosimetry. In Appendix B, however, it is not apparent why the ICRP now shifts its approach for radon and thoron dosimetry from an epidemiologic based model to a dosimetric one. More explanation is required
A more specific comment is that some references quoted in Appendix B do not appear in the Appendix B reference list. These are:
- Harley et al. 1996
- Winkler-Heil and Hofmann, 2002
- Winkler-Heil et al. 2007
Also, Marsh and Birchall 2000 (in Table B.1) is not in the Appendix B reference, however, a reference to Marsh and Birchall 1999 is listed.
Paragraph B 12, line 1452 It is noted that there is some diversity worldwide in the determination of radon exposures. For example, residential exposure assessments primarily rely on measurements of radon in Bq/m3. However, in occupational settings, such as uranium mining, it is important to measure the actual health risk, the immediate decay products of radon, conventionally in working levels (WL) but also in potential alpha energy concentration (PAEC).
Paragraph B 12, line 1452 states that the ICRP will provide dose coefficients per unit exposure to radon progeny for different reference conditions of domestic and occupational exposure (i.e. of equilibrium factor and aerosol characteristics). Although likely just unintentional wording, we are concerned that any dose coefficients will be for radon measurements alone.
Since direct measurement of radon progeny (i.e. in working levels) forgoes the need of an equilibrium factor, we recommend, if it is not already planned, that any dose coefficients brought forth by the ICRP for radon include those for assessments of exposures determined from both measurements of radon and for radon progeny. We also suggest that the above referenced text be corrected to reflect this.
1122-1124 Please remove this reference and substitute with: Lane RSD, Frost SE, Howe GR, Zablotska LB. Mortality (1950-1999) and cancer incidence (1969-1999) in the cohort of Eldorado uranium workers. Rad Res 2010;Available from: DOI 10.1667/RR2237.1.
1297 Cumulative WLM=85 WLM, PY=285,846 (Lane et al, 2010)
1297 Not sure why Port Radium isn’t included in this table:
Port Radium/Canada/uranium/1950-1999/n=3,300/180 WLM/111,297 PY/ERR=0.37 per 100 WLM (0.23, 0.59) (Lane et al, 2010).
1472 NRC, 1998 not NAS, 1999
1482 NRC, 1998 not NRC, 1999