Low Dose radiation: Regulators Dilemma

I wrote a detailed feature article with the same title last year. I am reproducing it again for the benefit of my colleagues in the field of health physics and radiation protection. These disciplines progressed well. Side by side, we have not  made any attempt to carry information to the public at large  in jargon-less language. It is indeed a tall order. We have to make an attempt. Our discipline cannot remain in isolation.

Low dose research has made substantial progress by developing new tools, methodologies and techniques. It is now possible to make a single Double Strand Break (DSB) visible. DSB is believed to have a significant influence in initiating the carcinogenic process .The capability to identify and record a single double strand break is an admirable technological achievement.  This has a negative impact.Many persons have criticized this.The earlier explanation of the importance of a DSB is doubtful as per present knowledge. Cancer formation is much more complex.

With this introduction, let me reproduce my PTI article. I shall greatly appreciate feedback. Most of this article was covered by me in an invited talk at the Annual Conference of the Indian Nuclear Society in Mumbai.

PTI Feature                                                     Science

VOL NO XXX(02)-2014  January 11, 2014                     PF-07/2014

Low Dose Radiation: Regulators’ Dilemma

Dr. K.S.Parthasarathy

The dose levels to radiation workers achievable are so low compared to the dose limits recommended by the Atomic Energy Regulatory Board (AERB)  that the risk from them is negligible.

Radiation protection specialists unanimously agree that radiation at high dose levels can cause cancer. At low dose levels, the results are not conclusive. Specialists accept the Linear-No-Threshold (LNT) dose-effect relationship as a practical approach in radiation protection. That means that the effect increases linearly with dose without a threshold; any dose however small will have some deleterious effect. Blind application of this pragmatic concept leads to unreasonable fear about radiation. Regulators face their own dilemma

In 2011,  Dr.Edward Calabrese, an environmental toxicologist at the University of Amherst discovered that Dr Hermann J. Muller, famous radiation geneticist knowingly lied in his Nobel Prize(1927) lecture when he claimed that there was “no escape from the conclusion that there is no threshold.” ( Archives of Toxicology and Environmental and Molecular Mutagenesis, Sept 2011)

Did this assertion led to the LNT concept  which became a corner stone of radiation protection? James Schwartz, a biographer of Muller, Kenneth Muller, Hermann Muller’s grandson and Elof Axel Carlson, Muller’s former student do not agree with Calabrese. Some argued that Calabrese, a supporter of radiation hormesis ( beneficial effect) has conflict of interest.

The correspondence this writer had with specialists such as Dr Evan B. Douple, Associate Chief of Research at the Radiation Effects Research Foundation, Hiroshima,  Dr. Allen Brodsky, Adjunct Professor of Radiation Science, Georgetown University, Prof. Edward Calabrese and Prof Ludwig E. Feinendegen, Heinrich-Heine University, Germany suggested  that the edifice of radiation protection is not built on a lie.

The French Academy of Sciences, the scholarly body with  views closer to those of Calabrese on hormesis conceded that on the basis of present knowledge, it is not possible to define the threshold level (between 5 and 50 mSv) or to provide the evidence for it. Evidently the value of threshold dose is not going to be useful to the regulator.

The  report published by the French Academy of Sciences and the French Academy of Medicine in March 2005 and another report published in July 2005 by the American National Academy of Sciences’ Committee on Biological Effects of Ionizing Radiation ( BEIR VII –phase 2 report) arrive at different conclusions on LNT concept, seemingly using the same set of peer-reviewed papers on the topic

This writer  brought the regulators’ dilemma to the notice of Dr. Richard Monson, the Chairman, BEIR-VII and Professor Tubiana Chairman, of the committee which wrote the report of the French Academies.

In response, Dr Ian Douple the then director of the Board on Radiation Effects Research that provided oversight to the BEIR VII Report revealed that the reasons for the difference include approach used by the BEIR committee, timing of the report, information available to the committee and the composition of the committee.. He argued that the BEIR committee had direct access  to the very latest A-bomb survivor data, including cancer incidence data, with the new dosimetry (DS02),

The French report criticized the paper titled “Cancer risks attributable to low doses of ionizing radiation: Assessing what we really know” authored by key specialists across the world in the Proceedings of the National Academy of Sciences (PNAS, 25 November 2003). This report appears to have played a key role in the deliberations of the BEIR committee.

This writer sent the extracts of the French criticism to the lead author Dr David J Brenner, Center for Radiological Research, Columbia University, USA. He addressed one major point. Evidently, there is no agreement among specialists who deal with biological effects at a few to few tens of mSv, the region of interest in radiation protection. I sent Brenner’s views to Prof. Tubiana. He promised to address the issues in some forthcoming papers; he sent them later when they were published.

The regulatory agencies will stick to LNT as it is a practical model. The LNT baiters including  Calabrese and his followers are not able to give precise threshold doses for various effects; This writer is  waiting for their recommendations on dose limits!

The dose levels to radiation workers achievable are so low compared to the dose limits recommended by the Atomic Energy Regulatory Board (AERB)  that the risk from them is negligible. For instance, the AERB Annual Report of 2012-2013 (www.aerb.gov.in) indicates that in 2012 no radiation worker in any nuclear power plant (there are over 14,400 workers in Indian nuclear power plants) exceeded the dose limits prescribed by AERB.The average radiation dose varied from 0.35 mSv to 2.84 mSv, a fraction of the AERB annual dose limit of 30 mSV. Conclusions were similar in earlier years. At these doses, radiation risks, if any, are negligible. Negligible risk is no risk at all. That we cannot rule out beneficial effects of radiation is also a comforting thought!.

Probably radiation dose is not important. “People can be easily sensitized to issues of climatic changes. So nuclear power protagonists can have a natural alliance with informed environmentalists.” Dr Roald Hoffmann, Nobel Laureate suggested in an interview given to this writer  in January 1988.

“We need to educate the public regarding the importance of ‘acceptable levels of risk’—levels that are believed to include risks, but risks for adverse effects that are so small that one would not be able to observe and measure an excess of the effects with a realistic study. Only then will the fear and paranoia associated with radiation effects gradually become less and less and sources for energy production can be fairly and objectively be evaluated,” Ian Douple, , Associate Chief of Research at the Radiation Effects Research Foundation, Hiroshima, proposed in an e-mail response.

This is certainly a pragmatic and acceptable way forward.  Over emphasis on hormesis and over simplification of some reassuring observations by nuclear enthusiasts may not be appropriate. Not yet. Low dose research must continue. We must disseminate correct information on recent advances in radiation biology. Relative impacts of various sources of energy may also be discussed.

Discerning public will make the right choice

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About ksparthasarathy

I am a former Secretary of the Atomic Energy Regulatory Board. I am a former Raja Ramanna Fellow in the Department of Atomic Energy. Free lance journalism is my hobby
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One Response to Low Dose radiation: Regulators Dilemma

  1. It is misinterpretation that
    ‘Populations living in areas of elevated radiation levels for several generations do not appear to have suffered any harmful effect. Some specialists feel that it is time to liberalize radiation protection standards.’ Law of minimum threshold radiation without any lower limit still holds good.(http://bhattsdentalclinic.blogspot.in)

    1)You rightly brought the point that quantum of radiation within few seconds or minutes or days or years, all will have different and increasing damage to cellular structures.
    2)It would be appreciated that blast or heat of war head or disaster is less responsible for the fatalities and cell injury than due to the radiation of gamma and X rays and neutrons and neutrinos and the fission products’ fall out from usual fission events ( for that matter fusion reactions can be considered GREEN!, from the view point that there is zero fallout except momentary high energy neutrons and hence treaties to use only fusion war heads and ban for all conventional thermal reactors or devices on U or Pl be adopted internationally!,,! and protect the future generations from long half life bye products of fissile fallout which is absent in fusion devices.)
    3)why only the back ground high radiation of Kerala is being quoted? Even at high altitudes many communities endure high radiation. There is genetic variation for mutation threshold which varies from species to species. Ideal model for such study can not be humans but standard bacteria like E Coli. The rule of minimum threshold values holds good for multicellular with high probability. There is one hypothesis that resistant strains against bacteria are never developed but only those sub-types survived which had high genetic threshold giving false impression that over a period resistance has developed.

    Like

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