Comments on TG 81 Radiological Protection Against Radon Exposure
The following comments on the draft report of ICRP TG 81 Radiological Protection Against Radon Exposure (“Report”) are respectfully submitted for consideration.
The ICRP’s draft report describes a generally reasonable outline of an approach to manage the complex problems associated with radiological protection against radon. However, despite the obvious effort involved in developing the draft report, we suggest that the Report would benefit from further work and clarification of a number of issues. It should be noted that the following comments are not intended to be exhaustive but rather illustrative of areas that we feel would bemnefit from further consideration.
General Remarks.
The following broad issues are noted
This Report The report is almost completely about the existing (member-of-the-public) exposures and this leads to a radon (222?) reference level to control the population dose. There is relatively little concerning planned (occupational) exposures where it appear the concern is based on the individual dose. When considering individual dose, the dose should be based on the detriment which is highly dependent on smoking history. The planned exposure section could be expanded or it might be cleaner to have two separate sections; one for existing exposure and the other for occupational.
An important focus of the Report is on individual risk from residential/occupational concentration guidelines. In our view, the particular dose reference levels (then derived concentration levels) provided in the Report are not well developed because there is no clear reason for the reference dose level adopted by the Committee. This should be spelled out.
An upfront statement that dose is mainly from progeny should be made along with the consideration that radon, in existing sources (buildings) is a useful surrogate.
The discussions of control of occupational exposure and of uranium mining are currenetly separate. Uranium mining is an occupation as, for example is coal mining or some gold mining and many activities involving naturally occurring radioactive materials (NORM) where workers are also exposed to radon at work. We would suggest that there would be benefit to discussing all occupational exposures in one section as while the degree of protection may vary from one industry to another, the principles should be transferrable argue that
With respect to the issue of risk to smokers and those who have not smoked, we suggest exposure constraints (DCC) should be based on smoking history where individual doses are of concern. The second question, admittedly challenging, is how much of the synergistic risk between smoking and radon should be applied to radon. Smoking is by far the leading cause of lung cancer and most of the risk from exposure to radon accrues to smokers. Some further consideration of the role of smoking in radon lung cancer would be useful.
We understand the ICRPs desire to move to dosimetric model based conversion factors for radon; however, we suggest that this transition may be premature as for example, dosimetric models require numerous assumptions regarding the behaviour of radon daughters in the lungs and since current models require further development to address smoking. Such issues raise challenges in defining the “right” reference dose (or family of reference doses). In addition, We also suggest that more data on aerosol characteristics of homes and mines is needed to understand the impact of moving to a fully dosimetric approach.
The Report is inconsistent throughout in radionuclide identification: with and without hyphen (e.g. Radon 222 and Radon-222)
Radon-220 and Radon-222: the ICRP raises the issue about Radon-220 but treat it minimally throughout. For example, the reference levels are based on Rn-222, what is the role of Rn-220.
All UNSCEAR 2009 should be UNSCEAR 2006
Specific Comments
Executive Summary
p.6 Line 176-177 radon 220 and radon 222 will come from all building materials. A “significant’ amount may come from some building materials but that requires definition of significant amounts
p. 6 Line 179-181 “Because radon is inert, nearly all of the gas inhaled is subsequently exhaled. However, when inhaled, (some fraction of) the short-lived radon progeny can deposit within the respiratory tract”.
This sounds as if radon in the tubes generate the decay products. An wwkward sentence. Most of the dose is from radon progeny and not radon. Radon is only a partial surrogate for the dose. Perhaps consider that the protection is for “radon and radon progeny”.
p.6 Line 188 Drop the “now”: there has been compelling evidence for a long time.
p. 6 Line 191,192, 193 Detriment adjusted risk of 8x10-10 per Bq h m-3. Risk coefficient for what? Should state the specific health effect – lung cancer.
p.6 Line 202,204 One would think that the ICRP could say that a mine was a “planned exposure” rather than using the “may”.
p.6 Line 205 to 2011. Is ICRP recommending that emergency exposure situation be managed (ICRP 103) or not?
p.7 Line 207 was “raising” meant to be “rising”?
p. 7 Line 229, 243, 284 suggest define “ambition”, as is, it seems meant to be vague.
p.7 line 248 second “largest” cause
p7 Line 251,252 not clear whether individual smoking status should be used or population (e.g. together).
p. 8 line 266,267 add “approximately to phrase “middle of the range”: the “middle” is 10.5 mSv.
p.8 line 269 is “mesurable” spelt correctly?
p.8 Line 270 A serious issue re reference levels.
States “Reference levels for radon are typically set in terms of the measurable quantity, Bq m-3. The Commission therefore recommends an upper value of the reference level for radon gas in dwellings of 300 Bq m-3 .
Following “therefore”—there is no supporting evidence except prior use in ICRP 115. The reference level dose of 10 mSv/yr does not agree with this concentration.
(300Bq m-3/ 37 X 0.4 =EEC /100 X 50 = 1.6 WLM/y
The new dose conversion convention 5 x 10-4 /WLM / (0.05/Sv A bomb) = 10 mSv/WLM
1.6WLM/y X 10 mSv/WLM =16 mSv/y
This hardly complies with “therefore” etc.
If the equilibrium factor is larger than 0.4 as it may be in some homes, the annual dose can be >20 mSv/y.
p. 8 Line 306-307 The upper value of tolerable risk for occupational exposure to (on the order of) 20 mSv/y …should not be exceeded. This reduces the mine occupational limit t 2 WLM from the existing 4 WLM/y. The value of 4 WLM/y is accepted as a de facto international standard. Achange must be reconsidered.
p.8 line 273,275 difficult to “simply” understand this phrase
p. 8 Line 278-282. “self help”. This places initial responsibility on individuals. Continues with unspecified “integrated and graded approach”. The procedure should be spelled out for clarity.
p. 8 Line 307 What is meant by “on the order of 20 mSv/y” and “possibly” averaged over 5 years. Some clarification is needed.
p. 8 Line 306 States “The upper value of tolerable risk for occupational exposure… of 20 mSv/year…”.
If the dose coefficient is 10 mSv/WLM this would changed the existing international limit of 4 WLM/y to 2 WLM/y. Is this the intent?
p. 9 Line 340,346 The “action” plans should consider both preventive and mitigation sections. This should be clarified or a new section added as currently these are only in the mitigation text.
p.10 Line what is meant by “Only indoor radon is at stake”. Dropping or clarification is needed.. What about mine exposures? What about outdoors near sources?
P. 10 Line 353-355 Drop the “now” (it has been present for a long time) and second “leading” cause
P. 10 line 359-361 very confusing and does not include planned expsoures.
P.10 Line 372 “ is (a) decision “
p.10 Line 373 “realistic” rather than “realist”
p.10 Line 377 “population” rather than “global”?
p10 line 279 “mitigative” rather than “corrective”
p. 10 line 385 . No “.” in “300 Bq.m-3 “
p.11 line 394 “national positive list”?
Glossary
Exposure Pathway. It is not correct to define the term using the term , some clarification needed
Potential alpha energy concentration (PAEC). Need better definition.
p. 14 line 488,489 Shouldn’t this be included in Radon 220 progeny definition as well.
Working level (WL). 1.300 x 108 Mev m-3. Too many significant figures.
1. Introduction
p. 18 line 588 and page 17 line 575. Not clear why ICRP has a figure for U-235 when they suggest it is not nsignificant on line 579 of page 17. There is no need to add extra clutter to this document.
p.8 Line 270 One of the serious issues.
States “Reference levels for radon are typically set in terms of the measurable quantity, Bq m-3. The Commission therefore recommends an upper value of the reference level for radon gas in dwellings of 300 Bq m-3 .
Following “therefore”—there is no supporting evidence except prior use in ICRP 115. The reference level dose of 10 mSv/yr does not agree with this concentration.
(300Bq m-3/ 37 X 0.4 =EEC /100 X 50 = 1.6 WLM/y
Their New dose conversion convention 5 x 10-4 /WLM / (0.05/Sv Abomb) = 10 mSv/WLM
1.6WLM/y X 10 mSv/WLM =16 mSv/y
This hardly complies with “therefore” etc. If the equilibrium factor is larger than 0.4 as it may appear, this annual dose can be >20 mSv/y.
They must fix this and that is almost impossible without readjusting reference levels.
p. 8 Line 306-307 The upper value of tolerable risk for occupational exposure to (on the order of) 20 mSv/y …should not be exceeded. This reduces the mine occupational limit t 2 WLM from the existing 4 WLM/y. The value of 4 WLM/y is accepted as a de facto international standard. Achange must be reconsidered.
2. Characteristics of Radon Exposure
In general this is a superficial and poorly summarized section.
p.21 Section 19 and p.22 Section 20. Radon should be replaced by “Radon-222” because that is the subject of discussion here.
P. 21 Line 680-687 needs to be modified to better reflect factors affecting release of radon to pore space and then movement through pores. (Well described by the work of Alan tanner did who did much of the original research on diffusion from soil. Possible cites can be provided)
p. 22 Line 696-704 discussion of radon 220 needs to be reviewed
p. 22 Line 689 “The quantity of radon emanating from the soil is typically small and the radon is strongly diluted in the air..”. What is meant by this is not clear as this is the source of all radon.
p. 22 Line 713-715 States “Flow is more important than transfer by diffusion”.
This is not correct. Diffusion is a major transfer process.
p.22 Line 707 “radon gas is less diluted” would be better than “radon gas can concentrate as “
p. 23 Line 727 “radon in the soil (gas)” and maybe preceded by radium concentration in the soil?
p. 23 Section (25). It would be useful to have the contribution to indoor air concentration from building in materials and groundwater. Distinction on whether concentrations are for sources of for the contribution to indoor radon concentration would be important.
p. 23 line 746 (m3.h) -1 Units are incorrectly presented..
p. 24 line 749 Is the concentration within the concrete or is this an indoor air concentration
p. 24 Line 750 etc. This section must include radon release in residences from ground water use. Covered extensively in NAS 1999 report and should be cited. NAS (1999). National Academy of Sciences/National Research Council. Risk Assessment of Radon in Drinking Water (National Academy Press, Washington).
p. 24 Line 782 Not correct concerning biological clearance. Clearance is a large factor.
p. 25 Line 807 “(typically) corresponds”
3. Recommendations
P 33 Line 1126- 1129 States “Planned exposure situations are situations involving the deliberate introduction and operation of sources. Planned exposure situations may give rise both to exposures that are anticipated to occur (normal exposures) and to exposures that are not anticipated to occur (potential exposures)”.
This definition should be reworded. Implies the source is (always) brought to the individual in planned exposure.
Line 1134-1135 States “Existing exposure situations are exposure situations that already exist when a decision on control has to be taken…”
Existing and planned can be switched for mines.
p.33 Line 1146 States “Exposure to workers involved in uranium mining is often managed in the same way as a planned exposure situation “
When aren’t they planned? The ore was there so not planned? Existing and planned must be better defined.
p. 33 Line 1137-1139 States “radon exposure situations have the character of existing exposure …the source is unmodified concentrations of ubiquitous natural activity”.
This statement adds to the ambiguity.
Line 1150-1151 States “ It is for national authorities to decide which workplace situations are to be regarded from the outset as planned exposure situations “.
This seems unusual for ICRP.
p.34 Line 1210 -1214 Surprising the ICRP considers exposure to radon would have some benefits
p.35 Line 1239 through 1240. Not clear how a radon policy affects anti-smoking if existing exposures are considered on a population basis rather than individual basis.
p.36 line 1310 “outdoor(s)”; I
p.37 line 1380 10 mSv is not the “middle of the band”
p.39 line 1405 “significantly reduc(ing)”
p. 40 Line 1429-1431 States “National authorities establish their own reference levels.”
They can establish reference levels and whether planned (p. 33)or not. This is a first for ICRP
p.42 Line 1532-1536 states “However, the relationship between measured radon concentration and effective dose depends upon factors including attached fraction, that can vary between different locations. Therefore if the reference level is exceeded in a workplace, this does not mean that the dose reference level of 10 mSv per year is also exceeded”.
This is a mistake. The reference dose can be exceeded depending on dosimtric assumptions.
An increase/decrease in the attached fraction would have a trivial change in dose. A larger change in dose can occur with change in equilibrium fraction. A change from home Feq 0.4 to Feq 0.1 to 0.3 can reduce the dose by a factor of 2 for the same reference level. Perhaps reference should be to “unattached” fraction?
4. Implementation of Protection Strategies
p. 47 Figure 8 is useless without some explanation of the types of energy saving was performed in the various dwellings and should include the effects of subfloor ventilation both in planning and mitigative concerns.
p. 48 Line 1735-1736 states “As far as radon-220 is concerned the main source of radioactive gas in buildings is the thorium concentration in building materials (concrete, bricks, etc.).
This is not correct. The latest research shows diffusion from the ground is a main source.
p.48 line 1768 through 1770. Not clear here whether ICRP is saying forget about measuring Rn-220.
p. 49 Line 1783 There should be specific mention of recognized traceable calibration and QC in the national survey measurements.
p. 51 line 1902 there is a comma and period together in the centre.
p.53 line 1971 what is intended by a health surveillance system? Sputum or chest X-rays, anti-smoking initiatives?
p. 54 Line 2023-2027 The use of dose conversion factor here is not correct. The ICRP 1993 terminology is dose conversion convention. This is not a dose factor but a risk ratio with units of dose.