|Section 7 – Exposure to natural sources
Particular question raised by ICRP
The treatment of natural sources of radiation requires some further clarification as indicated in the comments below.
This section does not discuss the cosmic radiation exposure of aircraft crew (annual doses up to 5 or 6 mSv possible; included in ICRP 60; in EU BSS Article 42; UK legislation and guidance). If it is considered that this is not amenable to control as discussed in the draft Scope document then it would help to also say so here.
Paragraph 280 – it is not particularly helpful to refer back to section 2.2 here. It might be better to include a general reference to section 2 here. It would also be helpful to mention the Foundation document on the scope of radiological protection regulations here as well as in paragraph 47. Also relying on intuition is not necessarily a good thing as this may further the myth that natural exposures are not controllable.
Paragraph 282 - “Siting of dwellings…” Why not “buildings”?
Paragraph 283 - “Living in areas with high concentrations…” Why not “Living and working in areas with high concentrations…”
Paragraph 285 - why change from mSv/y to mGy/y in the same sentence? Also, “These indoor exposures can generally be reduced.” Does this mean mitigated or prevented? Does this concern existing or new buildings?
Paragraph 286 – the third sentence seems to be incomplete- ‘the decay series are more what -variable? Also, “… where radiological protection requirements can be considered…” missing letter.
Paragraph 291 - “The distinction between ‘natural’ and ‘man-made’ or ‘artificial’ radiation exposure has proved to be peculiar and unconstructive.” And yet it continues in this document.
Paragraph 292 - “This is also due in part to the fact that ‘man-made’ sources are more readily controllable than natural sources.” How is “controllable” defined - by percentage or absolute reduction in level or dose? In either case, it is a generalisation and the statement should be qualified.
Paragraph 293 - “The Commission…perceived demands of those affected.” Given the past unequal treatment of radiation from different sources, pandering to the “perceived demands” is likely to perpetuate this effect.
Paragraph 294 - “Due to the wide variations in residential radon concentrations between regions, exclusion levels should be set 40 Bq m-3, i.e. the global mean indoor radon concentration.” This logic, if any, is difficult to follow. How do the variations justify an exclusion level set at the mean concentration given that “exclusion” means that they are not amenable to be controlled with regulatory instruments? Also, “The Commission recommends that such sources are excluded from the radiation protection system (see Chapter 10).” Why? How is the proposed exclusion level of 40 Bq m-3 thought to be helpful? There might be circumstances in which it was considered cost-effective to install preventive measures in some buildings below 40 Bq m-3. Does exclusion only apply to existing levels, rather than measures to control future ones? The reference to Chapter 10 also seems wrong as this is on protection of the environment.
Paragraph 295 - “Other sources that are feasible to control…” It would be helpful to have some examples here, especially as drinking water is mentioned further on in the paragraph.
Paragraph 297- it states here: “The Commission’s view on radon risk assessment has, up till now, been that it should be based on epidemiological studies of miners. Given the wealth of data on domestic exposure to radon, the Commission now recommends that the estimation of risk from domestic radon exposure be based on the results of pooled residential case control radon studies.” What are the implications for radon at work, especially as workplaces vary from the essentially house-like to heavy industry? Are the data from miners and domestic radon epidemiology being combined? However, this does not seem to be taken up in the following paragraphs. In particular the dose conversion convention for members of the public (Paragraph 300) is based on ICRP Publication 65 and hence miner epidemiology.
Paragraph 299 - “Because most people exposed to radon will also be exposed to other forms of radiation…” Surely everybody exposed to radon is exposed to other forms of radiation. Also interesting (and good) to see that the working level month is still being used.
Paragraph 300 - “In particular, this may be the case where action levels are set for new buildings where radon remedial measures are far more cost effective than for existing buildings.” Remedial measures apply to existing buildings; for new buildings measures are “preventive”.
Table 6 - “Domestic dwellings”. Should be “Domestic buildings” or “dwellings”. We do not think you can have non-domestic dwellings. However, should there be clarification for dual-use properties (residential care homes, office within a home)? Presumably the stricter constraint applies.
Paragraph 303 - “It is now recognised that in some occupational exposure situations, particularly mines, radon exposure can be merged with other exposures…” Merged is not the correct word. The idea seems to be that the other exposures are not insignificant compared to radon; perhaps: “associated with other exposures of similar magnitude”. This needs further thought to define the circumstances in which you go from a constraint on radon concentration in Bq m-3 to a constraint on radon concentration in mSv. Also “In general, for occupational radon exposure, a level should be set at which the system of protection is applied and the resulting doses should be recorded in the worker’s dose record.” However, no guidance is given on what that level should be, or on what it should be based. This assumes that all workers occupationally exposed to radon will be on radon personal dosimetry when this is the exception rather than the rule, even in mines. For an exposure situation such as an X-ray unit within a hospital with high radon levels, a TLD or film badge will be worn, but the radon doses will not be added to the person’s record because the emphasis has been to reduce the radon levels rather than to monitor long term exposures. Annual doses are often significant below the radon action level but at present there is no requirement to monitor or record these.
Paragraph 304 – this states that the current conversion convention is not applicable to thoron decay products but then what is applicable? Although controlling the intake of lead-212 is suggested for protection purposes, this is not the only concern. It is not clear what should be done to measure the exposure and convert to effective dose.
Paragraph 305 - “Once optimisation…well below…perhaps monitoring activity concentration sporadically…” How low is “well below”? Some guidance on the frequency of post-mitigation surveillance monitoring would be useful. Exposure optimisation might involve only a change of working practices
Section 8 – Potential exposures
ICRP rightly notes the interaction between potential exposure assessment and emergency planning, but the text confuses issues relevant only to solid waste disposal with those only relevant to emergencies, and measures intended to prevent an accident occurring with the prevention of potential exposures should the accident occur. An example of the first confusion is in paragraph 317, which introduces the ideas of risk constraints and comparing them with the product of probability of exposure and the risk of fatal cancer associated with that exposure. This is a concept ideally suited to solid waste disposal where exposures will occur far into the future and most scenarios result in expected exposures well below the thresholds for serious deterministic injuries. However, this concept has only limited relevance to emergency planning, since the plans are designed to deal with mitigating exposures assuming the event occurs. Moreover, fatal cancer is not the only consequence that emergency plans need to address (as stated in paragraph 310 “In the case of major events with large-scale consequences, an assessment based on health effects as an immediate consequence of direct exposure to radiation only would be insufficient”). An example of the second confusion is Section 8.4 (paragraphs 320-323) which seems to equate ‘optimisation of protection against potential exposures’ with prevention of an accident occurring: there is no mention at all of emergency planning.
This section could perhaps also include something on public exposure to cosmic radiation exposure in aircraft. In particular there is the possibility of solar particle events (SPEs) having effects in the atmosphere and giving significant values of dose equivalent at flight altitudes. Such events can occur roughly with the following magnitude per flight /frequency: a few tens of microSv once per year; a few hundreds of microSv once per decade; a few mSv once per century. Airlines and advisory bodies have asked for some guidance of what predicted doses might require avoiding action. Note that a typical value for a trans-Atlantic flight is 30 microSv.
Paragraph 308 - nuclear site accidents are probably ‘Events where the potential exposures would primarily affect individuals who are also subject to planned exposures.’ but this might not be what is meant here so it perhaps needs to be made clearer. What does ‘directly exposed’ mean?
Paragraph 310 – this has three separate themes, which would benefit from being enlarged and considered separately.
Section 8.2 – this is an example of where a number of issues are discussed but little is given in the way of positive recommendations (see general point above on sections 6 to 11).
Paragraph 317 – there is no mention of non-fatal health effects here. If ICRP thinks they are irrelevant in this context it should say so, and if not then it should say what should be done about them.
Paragraph 318 – it is not clear what the risk constraint relates to as numbers are given with no unit. Presumably this is the risk per event rather than per unit of time but it should say so? Also, the second sentence suddenly starts talking about ‘normal occupational exposures’. What about the acceptability of accident risk to members of the public?
Paragraph 319 – this paragraph is not very clear. ‘The estimates of annual probabilities of initiating events much less than 10-6 must be treated with doubt’ - they are probably very uncertain but it doesn’t mean it shouldn’t be attempted, and how does the suggestion in the last sentence improve things?
Section 8.5. This seems to have been developed (as is standard in documents dealing with terrorism) around consideration of a dirty bomb. Hence ‘In most postulated scenarios associated with a radiological attack, radiation doses incurred by the majority of exposed persons will probably be low’ – this would not necessarily be so in the case of a concealed source. And ‘Conversely, a small number of people could be exposed to high radiation doses’ – again this might not necessarily be the case. Paragraph 327 refers to explosions and nothing else. This seems a significant omission. Even more worryingly, there is no mention at all of the surrounding context of risk and hazard from non-radiological threats, the advice just takes the usual RP ‘radiation is the only hazard’ line.
Paragraphs 331-333 - as well as ‘Accidents in radiation therapy’, should there not be some discussion of the serious consequences of potential exposures from interventional procedures?
Section 9 – Emergency situations and existing situations
The draft recommendations are somewhat confused about the distinction between planning and response. In particular, this distinction seems almost completely lost in Sections 9.4 and 9.5 (paragraphs 345 – 350).
There is also confusion between the content of Sections 8 and 9. Section 9 has no mention of emergencies due to terrorism so should part of section 8.5 go into Section 9? All of the types of emergency situation considered in Section 9 are accidents.
Section 9.2 – another example of the general point given above on sections 6 to 11.
Paragraph 335 - it would be useful to include references to deliberate release scenarios here. Although it is covered in ICRP 96 it would also be worth including here in the interest of completeness.
Paragraph 336 – In the last line we suggest that the term ‘site’ is replaced with ‘location’.
Paragraph 337 - It would be better if the second sentence was changed from “In addition,...............may be a significant factor" to “will be a factor”.
Paragraph 338 – previously the Commission suggested a level of 500 mSv below which tissue reactions would not occur and this has now been reduced to 100 mSv without any real explanation (see comments made under section 5). If this is dealt with in more detail in Annex A it would help to refer to this here.
Paragraph 346 - states ‘Justification of an intervention should begin by considering the average projected dose to the exposed population to which the intervention would be applied’. It would be better to adopt the same approach as recommended for planned situations (eg paragraph 216), ie that of the representative individual. Averaging dose over all those who might, eg, be sheltered, could mean averaging over a very wide range of doses. This could result in a highly non-optimum solution, and, in particular, insufficient protection for those most at risk. While the paragraph goes on to say that ‘if protective action is not justified, consideration should be given to…subgroups’. this is the wrong way round, and inefficient. What planners more naturally do is to consider discrete groups of people who are similar in most respects, including their likely exposures, where they live or are located, the ease with which the countermeasure can be applied to them, etc, and then optimise their protection explicitly. After all such groups have been considered, consideration is then given to sorting out issues of applying the combination of countermeasures (eg evacuating a small group of people, who would otherwise have been sheltered, because this was already being planned for a larger, neighbouring group). This approach is much more like identifying a series of representative individuals than the approach set out in paragraph 346.
Paragraphs 348 – 350 - there does not seem to be any specific mention of the role of pre-planning and site emergency plans. Optimisation for planning and optimisation for response need to be performed somewhat differently but this sub-section tries to deal with them in the same way. They should be discussed separately with guidance on how site emergency plans link into each of these processes (i.e. emergency plans are the result of the planning optimisation and the starting point for response optimisation).
Section 10 – Protection of the environment
Section 11 – Implementation of the Commission’s recommendations
Paragraphs 358-395 - there is no specific mention of medical exposures
(e.g. in 11.3 on ‘The assessment of doses’).
Diagnostic reference level is missing.