EXTRACT OF THE INTERVIEW GIVEN BY Prof. Roger Clarke, chairman, International Commission on Radiological protection to Dr. K.S. Parthasarathy, Secretary, AERB during his visit to India to participate in the International Conference on Medical Physics and the XIXth annual Conference of Association of Medical Physicists of India
( Published in the AERB Newsletter)
Dr. KSP : I remember that it is not your first visit to India
Prof. Roger Clarke : I cam to India a few years ago. But I am attending the Medical Physics Conference for the first time.
KSP : In your last visit you addressed the officers of the Atomic energy Regulatory Board (AERB).
RC : I know a few colleagues from India who worked with me in the Committees of the International Commission on Radiological protection.
KSP: How did you get into the field of radiological protection? What was the incentive to enter this field? The career of a radiation physicist may not have been lucrative. Is it not?
RC : I was a reactor physicist working for the Central Electricity Generating Board (CEGB). One day my head of Division came to me. He wanted an answer for the question, with how many failed fuel plus pins you can operate an Advanced Gas Cooled Reactor (AGCR). It was in the Sixties. AGCR fuel was more expensive. Primarily the emphasis was on the basis of those to the public. I collected relevant data. In the process, I calculated the inventory of the fission products. I got introduced to health physics. I did some environmental modeling, got interest in radiobiology. Later I joined the National Radiological Protection Board to establish close assessment capability after gathering inputs on the environmental concentration of radionuclide. There was a group working on the movement of radionuclide in the biosphere. This was 20 years ago. This group was primarily interested in the study of radiation doses due to releases of radionuclide.
KSP: Historically, the International Commission on Radiological Protection (ICRP) was setup to make recommendations on the safe use of ionizing radiation in medicine. But it took a few decades for ICRP to bring out comprehensive recommendations on the protection of patients in diagnostic radiology. What was the reasons for this? Was it because ICRP did not want any control on medical radiation proactive?
RC : In the early years, therapeutic treatment was given more emphasis. The forerunner of the ICRP originated from the recommendations of the British X-ray and Radium Protection Committee. Then the major concern was protection of the workers. This was because deterministic effects such as extensive skin damage was seen among the x-ray workers who handled x-ray units. After the Second World War more penetrating radiations came to be used in medicine. Artificial radioisotopes appeared on the scene. More and More public were exposed. The emphasis shifted to public exposure. It coincided with more developments in fifties the emphasis was on therapy. Later more and more diagnostic technologies were developed.
KSP: Is it true that after the Second World War, many technically qualified people entered the job market. Many of them were electrical engineers. Apparently, this gave a boost to the development of newer technologies, which included manufacture of x-ray generations of higher and higher voltages.
RC : That is true. Radiation generators emitting more penetrating radiation began to appear in medical practice. Leukemia was identified among medical practitioners. The work by an American Physician Mr. Shields Warren is notable. He reported that Leukemia among radiologists was higher than that among general medical practitioners. It was obvious that ICRP, in this background, started giving more emphasis to patient protection. I would like to mention one recent development. Deterministic effects are coming out into focus now. Some of the interventional procedure, if carried out without care, can give substantial does to patients.
KSP: So it is not true that ICRP was somewhat biased in favour of radiologists over the years. What was the type of representation radiologists had in the ICRP?
RC: That ICRP charter states that only one radiologist need be there in ICRP though it was set up by the International Congress of Radiology – a professional association of radiologist – It is often not known that there are two more organizations to be considered, the International Commission on Radiation Units (ICRUs) and the International Committee for Education in Radiation and Radiology. The latter organization was established a few years back, but was not very active. It was re-established around five years back.
KSP: What are the new concerns?
RC: The concern of the radiologists shifted to finding out what is a better image. Future is in imaging, in medical imaging. For instance, digital imaging in interventional radiology, electronic manipulation of images, fluoroscopy with computer software. These technologies are likely to appear. More and more computer will start controlling x-ray imaging. Surgeons will turn round and expect computers to control the imaging procedure. With the newer techniques being used a dose reduction of a factor of about 10 is possible to the patient. The workers are also benefited by the dose reduction.
KSP: Do you agree that the scholarly discussion on the Linear-Non Threshold (L-NT)hypothesis has contributed to the notion that there is no safe level of radiation. Has it not sensitized the large public to greater and unreasonable levels?.
RC : I agree. When experts disagree, the credibility of specialists suffers. If experts do not agree, how can people decide which side of the argument is believable? I cannot deny that the arguments on L-NT has created some difficulties. The situation could be bad because there is an increasing possibility that decisions in science may be made by judges and juries in court rooms and not by professional association or by Royal Societies. The judiciary system may not be able to convince itself about the increased possibilities of radiation effects.
KSP: Don’t you thing that it is futile to try to get a deterministic answer to a purely probabilistic question?
RC: Yes. But I do not understand why some people wanted to establish that there is a threshold does below which there will not be any radiation effect. One of the major difficulties is in tackling the problem of old contaminated sites. Small radiation doses due to residual radio activities left behind at certain sites an cause very tiny amount of radiation doses. But when these doses are integrated over several thousand years. One may end up with getting significant amount of doses. We ill be left with the estimates of a few hundreds of probable deaths due to these collective doses accumulated over a long period of time. But I believe that we must have started dialogue on acceptable risks.
KSP : I am sure we must exclude voluntary risks such as risk due to smoking while we consider acceptable risks.
RC : Yes, I agree. Only involuntary risks are to be considered. In general, I am worried that the philosophy of protection has become somewhat complex.
KSP :Even for the professional ……..
RC : You said that and I agree. We must develop simpler concepts. ICRP must start consultations with other groups and collect ideas for reviewing and consolidating the system of protection. We have started to do that already. It explains why some of our recent documents are better than earlier ones. Consultation with others will help to improve the documents. The document on radon is an instance in point.
KSP: Everyone was keen on the on-going L-NT controversy. While the ICRP and the NRPB supported the argument that there is no threshold for the effects of ionizing radiation, the US Health Physics Society was unconvinced. The NRPB bulletin went to town with the suggestion that the attitude of the Health Physics Society is in tune with the liberalized attitude of US Administration to nuclear power. Can you comment on this development?
RC : Yes, certainly different professional groups looked at this issue very differently. American Health Physics Society has its own stated view. I have been to Health Physicists Society. Lots of people were interested in the controversy. The arguments put forth by the Health Physics Society are outdated with respect to the recent findings on the Japanese survivors of the atomic weapons. They did not then have the occasion to see the data. The recent data indicated that there could be significant risk at doses as low as 50 mSv, of course with much uncertainty. I do not still understand why they are looking for a threshold. There are many unknown cellular phenomena to be understood. Genomic instability, for instance.
KSP: You have become an unquestionable proponent of the linear non threshold theory. Certainly you didn’t ask for such a position. Do you really think that this controversy when uncontrolled?
RC: Yes. In my view, there is no need to search for a threshold. Nobody denies that there is evidence for the repair of cellular damage. But we cannot ignore that the repair mechanisms are also statistical in nature.
KSP: Biological effects of radiation has been studied for the past 100 years. The stochastic effects such as cancer world not have even been through about, but for the long an expensive epidemiological studies. Is it not unfair to spend too much of resources, in fact, vast sums of money to carry out studies about an agent which is now known to be much less hazardous than hundreds of toxic chemicals about which practically nothing is known.
RC: I may say that physicists should take the blame for it. The study of nuclear physics progressed rapidly. Some of the best brains entered the profession. The study of physics was intellectually satisfying and scientifically stimulating. Unfortunately, the same was not true for chemicals. Of late, biologists are also stating to use more and more mathematical formulations. Probably natural sciences are getting ready to make quantitative estimate.
The biggest injustice done is to attach a speaker to a Geiger counter, You must remember that nobody attaches a speaker to a gas chromatograph. In case higher values of hazardous chemicals are detected, the speaker howling is more dramatic and will definitely arrest the attention and create a problem.
There are several aspects to the understanding of the risks from chemical compared to the risks from chemical radiation. Natural radiation is present everywhere. There is no such analogue in the case of hazardous chemicals. Releasing genetically modified plants without control is probably in my view a higher problem. No doubt of course, this area getting more attention now.
KSP When the French Academy if Sciences published a report critical of ICRP for lowering dose it as French Government policy. To many, it was not surprising as France has a stake in nuclear power. They feel that lower dose limit is probably not in this interest. What is the current position of the French Government?
RC: The French Government has signed the European Directive. The French Electric Power Industry is committed to ICRP recommendations.
KSP: Release form a nuclear facility can be controlled by appropriate methods. It may cause increase in the collective doses to workers. In some instances the collective doses to workers may be far more than those to public. Which option will be acceptable in your opinion?
RC: Both occupational and public exposures are being reduced by optimization procedures. Storage of waste on-site may actually cause a potential for accidental exposure of the public as well as exposing workers. As long as individual doses – workers and public – are acceptably low, the situation is optimized.
KSP: The recommendation of ICRP are universally respected. I remember that the National Radiological Protection Board recommended a dose limit of 15 mSv/year even before ICRP recommendation were issued. NRPB faced some amount of criticism. What is the status of implementation in the UK and USA?
RC: The European directive was issued in May1996. These directives are legally binding on all states and the directives were to be implemented by 2000. In UK, the Health and Safety Executive has to make appropriate already been started. There is a need for harmonizing different documents. For instance different exemption levels are given under different contexts in Europe.
KSP: why are there such differences in exemption levels in Europe?
RC: In UK, the Radioactive Substances Act is one of the regulations which is different from The lionizing Radiation Regulation 1985. Health and Safety Executive is reviewing both these. The disposal of radioactive substances comes under the Radioactive Substances Act. The harmonizing of values and concepts and making them consistent is taking some time.
KSP: Was it not because there are some differences in opinions and views?
RC: That is not the reason. Certainly different agencies are at work. Most of the values of exemption levels are given in the European Directives.
KSP: Based on the impression that ICRP may revise the dose limits downward, AERB had its first comprehensive review of occupational exposures in 1989, a year before ICRP 60 was issued. We have implemented the recommendations are similar to those of ICRP except that the maximum dose limit in any year recommended by AERB is 30 mSv instead of 50 mSv recommended by ICRP.
Our experience is that among the various groups using ionizing radiation, industrial radiography is the most important. In India this field is probably one of the most regulated. The Regulatory Board issue authorization only if certified radiographers, a site-in-charge and appropriate radiation measuring instruments and protective accessories are available at every site.
RC: Industrial radiography has certain peculiarities. In this field, the workers are likely to be exposed to high radiation doses. The field has more potential for accidental exposures. I understand that ionizing radiation occurred in the field of industrial radiography. A man whose film badges did not record any reading but did due to radiation exposure related symptoms.
KSP: He must have been totally careless. I remember that the dose to this worker was evaluated by very advanced dosimeter method using his teeth as sample. What do you propose to make this field safer?
RC: This field is such that it is impossible to supervise them well, as their place of work is distributed in various work environments. For instance, often they work alone in the field while laying gas pipelines. So the only way we can improve the safety status in by imparting appropriate training to the workers. The regulatory organisation should ensure that such dedicated training programme is extended to all the workers.
KPS: Since reducing dose in medical X-ray practice is easier and less expensive, is it not more appropriate to allocate resources more prudently to achieve substantial reduction in collective doses in diagnostic radiology? If I say that there should be more efforts to reduce needless medical exposures, it may be looked upon as an attempt to divert public opinion from exposures in nuclear installation. ICRP should come out with such clear statements on avoiding needless exposure.
RC: We have gone a long way. The International Basic Safety for Protection against Radiation and safety of Radiation Sources has given certain guidance values. The United Kingdom also accepted certain guidelines. With these precautions, the collective dose can be reduced by about 40% But this was more than offset by the predominant use of CT scan units.
KSP: When many States in the US brought out guidelines for typical X-ray examination based on the National X-ray Trend Programmes, UK was less enthusiastic about the concept. Now Basic Safety Standards came out with guidance. What is your general view on this? Can you include the guidance levels in regulation?
RC: I believe that prescribing guidance levels similar to the one stated in BSS is in the right direction. The experience in the UK has been that there has been substantial reduction in collective doses to population at large over the year.
KSP: In your lecture at the International Conference on Medical Physics you spoke about carrying out appropriate evaluation of dose to commercial airline workers under the category of occupational workers. How many countries in Europe have done this?
RC: Cosmic rays obviously come under natural radiation. Under the European law, the member states shall undertake surveys to estimate the magnitude of the radiation exposure due to natural radiation. Currently large groups of persons journey by commercially operated airlines. Because of this, exposure to sensitive groups such as pregnant women may also have to be considered. There is a general thinking that dose contribution to the crew of commercial airline should be quantified by appropriate methods. This cab be done by on-board instrumentation and by considering the number of hours of flying by the airline. The intention is not that all the crew must wear dosimeters but the measurement of exposure will have to be carried out systematically.
KSP: At such high altitudes, the primary component of cosmic rays are high energy protons and neutrons. This is probably one area where we cannot do much about source control. What we can do is that regulated the exposure and the altitude in which the airline flies. The probability of radiation hitting the embryo or foetus will be miniscule. What is your thinking?
RC: I must say that currently the air crew are not subject to dose limits. But the radiation dose should be measured reasonably accurately by asking the number of hours the crew has flown and also by ascertaining the route of travel.
KSP: I understand that the Concord has appropriate monitoring equipment on board way back in 1970. When I was attending the Congress of international Radiation Protection Association at Brighton, I was at the dinner table with a group of scientist from UK who were actually making measurements in the Concord. Have you carried out systematic measurements? Is there anything new published since the special issue of “Radiation Protection Dosimetry” journal was published?
RC: Yes. Radiation measurements have been done and date are available.
KSP: I thought that the exposure is significant only during solar flares.
RC: According to my information the radiation levels on no occasion has increased to such an extent during the past 20 years which led to reducing the altitude of the aircraft to get the benefit of atmospheric shielding.
KSP: ICRP recommendation on pregnant women is known to be too conservative. What was the background information? Was there any re-thinking on this? As the dose limit recommended is different to measure, many institution may decide to withdraw pregnant women from radiation work. I understand that the topic is widely discussed in countries such as Canada where a great proportion of medical radiation workers are women.
RC: ICRP considers that the basis for the control of occupational exposure of women who are not pregnant is the same as that for men. On the other hand if a women is or may pregnant there is a need for additional controls to be considered to protect the unborn child. The considered is at times more prone than the post-natal individual to deterministic injuries caused by radiation and may be more sensitive to the induction of later deterministic effects in the live-born child including significant mental retardation will not happen if the exposure of the mother dose not exceed the dose limits now recommended for occupation exposure regardless of the distribution of the exposure over time.
Accidental high exposure of the mother may be more damaging to the concepts than to the mother.
The commission’s policy us that the methods of protection at work for women who may be pregnant should provide a standard of protection for any concepts broadly comparable with that provided for members of the general public. The commission considers that its policy will be adequately applied if the mother is exposed prior to the declaration of pregnancy under the system of protection recommended by the commission including the recommended dose limits for occupational exposure. This is the basis on which the commission recommended that no special occupational dose limits is needed for women in general.
The ICRP thought the recommendation of 2 mSv measured over the abdomen of a pregnant woman for the entire gestation period is very helpful. But there is some feeling that it is very restrictive.
KSP: In fact in Canada Atomic Energy Control Board (AECB) arranged discussion with woman workers in eight cities and asked for views. A few hundred women participated. Many of them argued that there is no reason to change the earlier limit of 10mSv.
RC: The Commission no longer recommends a dose limit of 2 mSv during the gestation period as measured on the abdomen of the pregnant women. The ICRP publication number 75 describes the current ICRP recommendation. Overall risks associated with radiation exposure of men and women are broadly similar. ICRP now sees no need to make any distinction between the two sexes in the control of occupational exposure. But once a worked is known to be pregnant, ICRP recommends higher standard of protection for the concepts.
The advice given in publication No.60 has been interpreted too rigidly. ICRP now recommends that the working conditions of a pregnant worker after the declaration of pregnancy, should be such as to make it unlikely that the addition equivalent dose to the concepts will exceed about one mSv during the remainder of the pregnancy.
It is important to highlight the responsibility of the worker and employer to meet the Commission’s objective. The pregnant worker should declare her pregnancy promptly to the management. The management should then organize the working conditions to make it unlikely that the additional equivalent dose to the concepts will exceed about one mSv during the remainder of the pregnancy.
KSP: Atomic Energy Control Board of Canada had detailed consultations with women groups on the reco0mmendation. I understand they may now recommend an external dose limit of 4 mSv on the abdomen or an intake of 20 percent of the annual limit if intake. ACEB had compared the general risks to the foetus during pregnancy and showed that at 4 mSv it is very low indeed. What is your view on this approach? I feel that if ICRP’s view expressed in publication No.75 is accepted, many employers will discriminate against women being employed in radiation work.
RC: The ICRP position is essentially as it was in publication 60 and elaborated in publication 75. The foetus to be protected broadly as though it were a member of the public.
KSP: Though conceptually it is clear that exposure at the dose limit is just tolerable, exposing everyone to the dose limit all the tome is not acceptable. Was it not more appropriate for ICRP to recommend a range of values rather than a single value?
RC: The current dose limit of 20 mSv per year average for 5 years offers this operational flexibility. A single number is administratively convenient. It is obvious that the body dies not known whether the exposure occurred in one calendar year or another. Biology does not identify this.
KSP: The recommendations of ICRP are scientifically the best available. But you will agree with me that these recommendation have enormous social impact. Is it justifiable for over a dozen specialists in purely scientific disciplines to take such decisions which have enormous social impact? Don’t you think that the representation in ICRP should be broadened to include social scientists and economists?
RC: There are various components to this question. ICRP recommendations reflect the best scientific information. We do not say what is acceptable to society or not. There is one recent development. ICRP is currently engaged in more and more consultations with specialists by providing drafts of their recommendations to other specialists and concerned people for review. It would certainly reveal whether there is any inconsistency in the concept and approach put forward by ICRP. It will help to find out whether there is any fallacy in our approach. I believe the recent ICRP document bear testimony to this.
