1) General comment
In general terms, I agree with the guidance developed in this report on the radiological protection against radon exposure. I was particularly pleased with the value judgment in favor of a simple approach clearly expressed in paragraph 50:
“Taking into account the ubiquity of radon exposure and the multiplicity and diversity of situations and decision makers, a simple radon policy is more effective, which addresses most situations in the same, integrated approach. It must be supported and implemented on a long term basis (several decades), and involve all the parties concerned appropriately”.
This preference for a simple protection system and in anticipation of the last sentence of paragraph 5 “The publication by the Commission of the revised dose coefficients for the inhalation and ingestion of radionuclides, including radon and radon progeny, will complete the updated set of publications on the control of exposure to radon” I would like to draw the attention of the Commission on the comment I submitted last year: not to use in future a set of reference dose conversion coefficients depending on the exposure conditions, such as aerosol characteristics and equilibrium factors.
I prefer using a single dose conversion factor for both workers and members of the public, and as an operational choice I suggest to select the long-established UNSCEAR conversion factor.
Supporting evidence
Defining a whole set of different dose coefficients per unit exposure to radon and its progeny ignores the most important factor influencing the radon risk, which is smoking. Indeed, because of its almost multiplicative relationship with radon, a smoker has for the same radon exposure at least a 10 times higher lung cancer risk than a non-smoker. As a consequence, changes in the ratio of smokers to non-smokers will result in significant changes in the estimated lung cancer risk. I don't see in this uncertain context the added value of using a set of dose coefficients on the basis of exposure conditions, such as aerosol characteristics and equilibrium factors. Moreover, it has been shown that the equilibrium factor is largely determined by the aerosol characteristics and that in many exposure situations the conditions are compensating, making radon a fairly good measure of the radiation exposure (Vanmarcke et al: Radon versus radon daughters, Health Phys. 56, 229-231; 1989).
Publishing a whole set of reference dose conversion factors based on exposure conditions has in my opinion little benefit and will, on the contrary, complicate the operational radiation protection of the exposed workers and members of the public.
I am in favor of using the single UNSCEAR dose conversion factor for both workers and members of the public. This factor is well within the range of possible dose conversion factors from the epidemiological and dosimetric approaches, as shown in the recent paper published in Health Physics by Marsh et al (99: 511-516; 2010), and does not give a false impression of precision of the lung cancer risk as would do a set of reference dose conversion factors. Moreover, the current worldwide average population exposure from natural radiation sources of 2.4 mSv/y is calculated using the long-established UNSCEAR conversion factor.
I refer to my recent paper in Radiation Protection Dosimetry for the discussion on the reason to select the UNSCEAR dose conversion factor for exposure to radon and its progeny (H. Vanmarcke, Radon: a special case in radiation protection, Rad. Prot. Dos. 130: 76-80; 2008).
2) Specific comments
Paragraph 56: the worldwide average radon concentration outdoors is according to UNSCEAR 10 Bq m-3. So the end of line 1097 is not correct: instead of “a few tens of Bq m-3” it should be “up to a few tens of Bq m-3”.
Paragraph 86: I suggest to add the words “in most cases” to the last sentence: “It is important to note that in most cases reference levels relate to the annual mean concentration of radon in a building or location”. The reason for this is that in a lot of workplaces, schools and mixed use buildings people are present only during the day, so that the average radon concentration could be quite different from the long term exposure.
Paragraph 107: in the first line only the attached fraction is mentioned as a factor modifying the relationship between measured radon concentration and effective dose. The attached fraction is in my experience only one of many factors. More important factors are occupancy factor, breathing rate, equilibrium factor… Therefore, I suggest deleting “including attached fraction”.
Figure 7 on page 44 seems to me unnecessary complicated. The distinction between the types of buildings (dwellings, mixed use buildings and workplaces) can be made below the ALARA box.
Paragraph 145: the last sentence gives as an example “or buildings with double glazing”. In most countries, at least in developed countries, double glazing is standard practice in the building industry so that (nearly) all new buildings have double glazing.