My urgent proposal is to read the original text of ICRP report 103. You will find a lot of definitions and additional explanations in the scientific annexes.

One info to the reduced eye dose limits. It seems that cataract is a stochastic effect and no tissue reaction (deterministic effect) as supposed before.

I have gone through it at least once fully. I thought a discussion would help for better understanding , so posted question here.

Of course their is need for some discussion, but it is impossible to handle the whole contents. May be you could specify your question. You see, I´ve already marked a special point (cataract).

One is what is the basis of 50 mSv.

I suppose 20 mSv per year was for 1 in 1000 deaths due to cancer at age of 65 which corresponds to ILO limits.

So 20 mSv is deduced from 1 Sv assuming (conservatively) 50 years of occupation. 50 mSv can be deduced allowing more flexibility. E.g., before 2001, the German legislation allowed 50 mSv per year, but not more than 400 mSv within 20 years.

The ICRP considerations start with the assumption that a lifetime occupational dose of 1 Sv is tolerable, corresponding to 5% additional fatal cancers (ICRP 103, paragraph (87)). So if an individual receives 1 Sv, the individual risk of fatal cancer rises from about 20% to 25%. 

Dear E.Strub,

a small additional information and correction . The annual dose for professional exposition is 20 mSv/year, the life time accumulated dose restricted like you correctly mentioned to 400 mSv, but added up over 40 years, because it´s recommended to restrict the everage dose per year to 10 mSv, the half of the legal limit.

The cancer morbidity risk in the western industrial nations on average is about 30 %, 25% are letal (mortality) because of the prolonged life time. I Sv would increase to 36% morbidity and enlarge the risk for cancer death from 25 to 30%.

A short comment to dear Wael´s very well matching post. As you correctly mentioned, the eye lens dose limit is reduced from 150 mSv/a to 20 mSv/a. But there are some more important changes. The dominant changes concern the organ weighting factors to calculate the effective dose and the risk factor for heriditary effects diminuishing from 20 to 8%.

I want to repeat Wael´s and my request to thoroughly read the important ICRP report 103. It contains  lot of philosophy and literature.

ICRP 103:

@Strub and @Hanno

(87) It is therefore the recommendation of the Commission that the approximated

overall fatal risk coefficient of 5% per Sv on which current international radiation

safety standards are based continues to be appropriate for the purposes of radiological protection.

But it does not state about the period for this dose, then how 20 mSv per year for 50 years. 

The idea of ICRP is concentrated in Table 1 ICRP 103 (page 53). I think the maintaining of the old 5% risk is an approximation and neglects the "small" changes in morbidity and mortality rates. These rates are taken for all exposed persons.

The time interval for professionals is for my knowledges taken for 40 years, and thats the way the dose limits are fixed. Taking have the annual dose is a restriction of national commissions to reduce additionally this radiation risk.

Is there something like 1 in 1000 cancer incidents/deaths for radiation worker for this dose rate (20 mSv/yr) and 1 in 10000 for general public (1 mSv/yr)?

There is no physical, medical, or epidemiological explanation of new ICRP dose limits, radiation weighting factors, and tissue weighting factors. The changes are political and it was time to issue a new report.

The change of cataracts from deterministic to stochastic has no basis. Indeed, the definitions of deterministic and stochastic were based on theoretical reasons to support the linear no-threshold hypothesis.

The history of weighting factors is most interesting. In particular, there is insufficient epidemiological data to define the carcinogenic sensitivity of organs. The weighting factors are based on severity of cancer in an organ, latency time of cancer in an organ, natural occurrence rate, fraction of life lost, morbidity and mortality, and hereditary effects. The weighting factors are a committee decision.

The radiation weighting factors (biological consequences of radiation by type and energy) have a scientific basis. There are important controversies concerning values of the weighting factors. The weighting factors are a committee decision.

The lowering of dose limits was strictly political.

Assign doses based on the ICRP system or local requirements. Do not accept that the methods of dose assignment are correct. Study the literature and research to support or deny the current system.

Dear Joseph,

interesting contradictions to the stochastic cataract. The first time in the last decade we get an explanation (peripheral mother cells with gendefects) to understand the low dose cataract or uranium workers, astronauts...

I agree, all changing of weighting factors are "political" or like you named them "commissonal". I agree but have no problem to accept minimized dose limits (because of error bars, missing knowledge etc).

I hope for further discussions.

Hanno

Below are a few comments from

DRAFT REPORT FOR CONSULTATION, ICRP ref 4844-6029-7736, January 20, 2011.

Note the use of the word 'suggested.' I have reviewed several of the documents listed and find that 'suggested' may be too strong a word to describe the results.

recent studies have suggested that the lens of the eye may be more radiosensitive than previously considered. However, new data on the radiosensitivity of the eye with regard to visual impairment are expected.

In recent years a number of new studies have suggested an elevated risk for cataract development in populations exposed to low doses of ionising  radiation below these assumed thresholds

recent work with experimental radiation cataract in animals, suggest that cataract may occur following exposure to significantly lower doses of ionising radiation than assumed previously

Not all recent studies, however, support the observation of a lower threshold for radiation cataract.

It is also recognised that there is variability among clinicians and investigators in the precise clinical definition of a radiation cataract and a diversity of opinion as to whether all detectable lens changes, given sufficient time, will progress to visually disabling cataract.

Several recent lines of evidence from experimental and epidemiologic studies have, however, suggested these [threshold] values may be too high  and that radiation cataract may be even stochastic.

Dear Joseph,

thanks for the hint, I will read and continue with discussion.

I would like to add two short points.  First ICRP publications, particularly its main reccomendations, are not strictly speaking, scientific documents.  They are documents which use a lot of scientific data, but they add a lot of value judgements to the data.  So they are the potent mix of real evidence and value judgments that allow policies, good practices and laws be formulated.  The commision has been good at the science end, but perhaps not quite as smart with ethics.

Second, in earlier times the philosophy of ICRP was to have dose limits with which the associated (calculated)risk was the same as that for safe occupations.  From surveys this was set at a 1 in 10,000 risk of a fatality (if I remember correctly).  This philosophy and the system built around it were widely regarded as "honest" and dependable.  In more recent publications this link with the safe occupation was lost. Again, as far as I remember, this happened in ICRP 60 published around 1991.  Since then, the supporting framework for the main recomendations has been less secure and more difficult to defend, and the feeling that they are honest tends to be challenged. 

@Jim,

the essential remark in your post is the problem of "political judgements". You are right, ICRP reports are no pure scientific reports.

For some of the judgements e.g radiation weighting factor for proton it seems so but not sure?

I have published the review paper in this field

https://www.researchgate.net/publication/262054513_Classification_of_radiation_effects_for_dose_limitation_purposes_History_current_situation_and_future_prospects

Best wishes,

Nobby

Nobuyuki Hamada, Ph.D 

http://researchmap.jp/read0140945/?lang=english

https://www.researchgate.net/profile/Nobuyuki_Hamada

http://scholar.google.com/citations?user=lrHbuw4AAAAJ&hl=en

Article Classification of radiation effects for dose limitation purp...

Dear colleague, to discuss the ICRP Recommendations (of 1977, 1990 or 2007 - it does not matter), it will be good to start from their radiological basis provided by the UNSCEAR. About 20 UNSCEAR Reports issued in 1958 – 2013 contain a lot of information about human effects of atomic radiation. The 2000 Report is of highest interest for the discussion. Its review is given in article of James Conca in FORBES of 11 January 2013. It is available at http://www.forbes.com/sites/jamesconca/2013/01/11/like-weve-been-saying-radiation-is-not-a-big-deal/#678f77124c34. It is the best plain language introduction to the matter I had ever seen.

For addition, I would like to put your attention to the principal statement of the ICRP about the practical use of effective dose.

You can find it in 2007 ICRP Recommendations (ICRP Publication 103, Ann ICRP 37(2-4), Elsevier, 2007). In section 4.4.6 (paras. 153 – 158) the ICRP prohibits to use of effective dose for evaluation of the radiation health effects. In brief, the statement is the following

“(153) The main and primary uses of effective dose in radiological protection for both occupational workers and the general public are:

- prospective dose assessment for planning and optimisation of protection; and

- retrospective dose assessment for demonstrating compliance with dose limits, or for comparing with dose constraints or reference levels.

(154) In this sense, effective dose is used for regulatory purposes worldwide. In practical radiological protection applications, effective dose is used for managing the risks of stochastic effects in workers and the public.

(157) Effective dose is intended for use as a protection quantity on the basis of reference values and therefore is not recommended for epidemiological evaluations, nor should it be used for detailed specific retrospective investigations of individual exposure and risk. ”

So, the Scientific Annex G (Biological effects at low radiation doses) to the 2000 UNSCEAR Report and the section 4.4.6 of the 2007 ICRP Recommendations should be the start point for discussion about the ICRP dose limits for both occupational workers and the general public.