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Radiation Doses, Their Limits: Related Issues Of Public Perception – Analysis


Everyone knows that workers in the active areas of a nuclear power reactor may be exposed to radiation. A group of professionals called health physicists monitors and measures the radiation levels at the workplace. They estimate the radiation doses to members of the public at the fence post of the reactors. They provide special radiation measuring devices to individual workers and keep track of the radiation doses received. The Atomic Energy Regulatory Board (AERB) has prescribed dose limits to workers and members of the public. They follow mostly international norms. The operating management must ensure that these doses are as low as reasonably achievable and within the limits prescribed by the Board.


AERB publishes the relevant data on the radiation doses to workers and the members of the public in its Annual Reports. These doses are well within the limits prescribed by AERB.

The estimated doses at the fence posts of all nuclear power reactors are small compared to the dose limit to the public. In addition, these values are less that the deviations in natural background radiation at the place even in the absence of nuclear power plants.

The operating management maintains the dose records of all workers. The Nuclear Power Corporation of India Limited (NPCIL) uses state-of the art methods to measure and keep track of doses to individual radiation workers.

Radiation protection specialists unanimously agree that radiation at high dose levels can cause cancer. At low dose levels, say less than 100 mSv, the results are not conclusive. (Sv is a unit of biologically effective dose. One Sv corresponds to a radiation energy absorption of one joule per kg; millisievert is one thousandth of a Sv; Annual dose limit to workers prescribed by the Atomic Energy Regulatory Board is 30 mSv).

Radiation protection specialists accept the Linear-No-Threshold (LNT) dose-effect relationship as a practical approach in radiation protection. This concept has created controversies.


Many scientists question the scientific validity of the LNT hypothesis. Scientists are unable to settle the debates over the effects of ionizing radiation at low dose levels. Admittedly, these are very trivial. The dose-effect relation at very low doses is very complex and unknown now. Many agencies are supporting research efforts to unravel the relation. The latest Low Dose Research (1998-2008) funded by the US Department of Energy revealed many new and interesting phenomena. Presently they are of academic interest. These efforts have not provided any actionable inputs to revise the already conservative radiation protection standards.

Radiation protection specialists presently follow a radiation protection regime without causing undue radiation exposures to workers and members of the public. It will be inappropriate not to derive the benefits arising from nuclear power generation or the applications of radiation in medicine, industry, agriculture and research just because the exact dose-effect relation is unknown. This is because we know enough about the interaction of radiation with living matter. We have been using ionizing radiation safely for the past several decades. In fact, our knowledge on potential effects of ionizing radiation is far more detailed and accurate than those from any other physical or chemical agent we know of today.

The application of the so called Linear No-threshold (LNT) concept without appreciating that it is just a pragmatic and practical concept leads to unreasonable fear about radiation. Equally, radiation-phobia is also due to the association of radiation with atomic bomb. Atomic radiation got associated with fear of cancer, a vague feeling of uncertainty, the images of children suffering from leukemia, birth defects of various types and description among others.

There are many strongly held misunderstandings on biological effects by different sections of people.

A typical example is the so-called genetic effects of radiation.

Genetic effects of radiation

In 1991, Shri Karan Thapar interviewed me on a popular TV programme “Eye Witness”. He asked me 40 questions in ten minutes. This is certainly not a conducive format for eliciting scientific information.

In the ensuing controversy, I stated the known fact (known to radiobiologists and others who cared to read!) that scientists did not find any genetic effects among the thousands of children born to the atomic bomb survivors at Hiroshima and Nagasaki. Thapar, however, unhesitatingly contested my statement as “inexplicable”; he wondered how I did form the impression that no genetic effects were found among the thousands of children of Hiroshima and Nagasaki. “The opposite is not just a fact, it is the truth,” he asserted. That was his perception.

This scientifically unsupported conviction did not surprise me, as we have found that misgivings and myths about effects of radiations are rampant even amongst technologists, social scientists, physicists, and other highly qualified experts. You may realize that this has nothing to do with LNT concept.

While responding to an opinion survey organized by AERB, for the National Academy of Engineering, over 80% of the participants from reputed academic and research institutions in India (IITs at Mumbai, Kanpur, Indian Institute of Science, Bangalore, Roorkee University, Saha Institute of Nuclear Physics, Kolkata, Tata Institute of Social Sciences, Mumbai) stated that genetic effect is a major health effect seen in the children of survivors of atomic bombings contrary to the fact.

Overall 762 persons responded: Trained scientists and engineers 242, including the faculty of some institutes of science and technology 182; science and technology students 456.

A large proportion (37%) believed (wrongly) that nuclear power makes the highest contribution to population exposure. Similarly significant number of people thought that nuclear medicine and industrial applications make the highest contribution to population exposure (actually their contribution is negligible).

An opinion poll I did among eighty specialists attending an advanced training programme at the International Centre for Theoretical Physics at Trieste, Italy showed that nearly 30% of the scientists believed in the myth that double-headed monsters were born to the survivors of atomic bombings.

It is virtually impossible to correct such firmly held beliefs. In that context, every stakeholder may face problems.

The fear adversely affect acceptance of nuclear power as a source of energy; it also raises issues on many life saving medical procedures involving the use of ionizing radiation.

Misunderstanding about the adverse effects of radiation is widely prevalent. Belief in the scientifically not accurate LNT concept also contributes. To what degree depends on the individual. People conversant with principles of radiation protection including the “believers” in radiation hormesis (they believe that radiation exposure has some beneficial effects) may blame LNT concept for the fear.

What is the role of the regulatory community in allaying unwanted fear of radiation? One has to be cautious about this. Regulatory community must not go over board as it may compromise the regulator’s impartial role. Regulators must explain the position cogently, confidently and impartially.

The Government of India set up the Atomic Energy Regulatory Board to enforce the provisions under Section 16 (control of radioactive substances), Section 17 (Special provisions as to safety) and Section 23 (Administration of the Factories Act 1948) of the Atomic Energy Act 1962.

The former two are applicable in the present discussion. The mission of the AERB is to ensure that the use of ionising radiation and nuclear energy in India does not cause undue risk to the health of people and the environment.

An important function of the Board is to “take such steps as necessary to keep the public informed on major issues of radiological safety significance”.

In 1990, the International Commission on Radiological Protection (ICRP) recommended for radiation workers a dose limit of 100mSv over any 5-year period and 50mSv in any one year. The limit for public was one mSv averaged over five years.ICRP retained a dose limit of 500mSv for any tissue or organ and 150mSv for eye lens. AERB implemented the new ICRP prescription in a phased manner.

What is a safe level of radiation?

It will be very useful to convey the values of radiation doses in medical procedures and other activities such as space travel for a full appreciation of dose limits.

What is a safe level of radiation?

The best answer is “It depends”. However, some puritans may argue that there is no safe dose.

There is no universally acceptable safe dose. For radiation workers, Atomic Energy Regulatory Board (AERB) wants the annual dose to be “as low as reasonably achievable” (ALARA); also, it should not exceed 30 millisievert (mSv) excluding the dose due to natural background radiation and medical exposure, if any. AERB dose limit at 30mSv is lower than 50 mSv prescribed by USA/ICRP. I have received about 0.9mSv while recovering a lost radiation source used in industry.

During the Fukushima accident one worker received 106mSv.

For members of the public, the dose limit is one mSv. Pregnant workers may continue to work but the dose to the foetus should not exceed one mSv. In medically justified procedures, we may measurethe following doses in mSv. Cardiac CT scan 12; angioplasty (a life-saving procedure involving removal of blocks in blood vessels)on an average 400; at times even 1000mSv; treatment of hyperthyroidism, 100,000; radiation treatment of cancer 60,000 mSv

In USA, the dose limit for an astronaut is 250mSv per mission. In an off-site radiation emergency, sheltering and administration of stable iodine may start at a minimum dose of 20 mSv; evacuation is mandated at 100mSv.

The average natural background radiation dose is 2.4mSv annually. This arises mainly from radiation emitted by thorium, uranium and potassium-40 in soil and a major contribution from radon and its decay products present in air.

In England and Wales, the radiation exposure to residents of over 100,000 to 200,000 homes is 10mSv annually from radon, a radioactive gas found in nature. The maximum value is more than 100mSv. Millions of persons in countries with temperate weather receive doses ranging from 5-to10 mSv from radon decay products.

Very detailed radiation measurements in the high background radiation areas in Karunagappally Kerala revealed that the maximum gamma radiation dose in different panchayats vary between 5.7 mSv to 76.5 mSv per year. Nearly 100,000 people have been living in the area where the average gamma radiation level is estimated to be 4mSv per year.

Thus, we note the presence of different values of doses, depending on circumstances.

One need not lose sleep over receiving a few tens of mSv, if the occasion demands it.

Radiation is like any other physical agent. It is not appropriate to attribute any special importance to radiation. In fact, ionizing radiation is a weak carcinogen.

The evolution of the radiation protection standards clearly demonstrates how the regulators followed a very conservative and careful approach in accepting the standards.

The French Academy of Sciences, the only scholarly body with views closer to those who support hormesis (radiation has beneficial effects) 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.

The dose levels to radiation workers achievable are so low compared to the dose limits recommended by the International Commission on Radiological Protection (ICRP) that the risk from them is negligible. Negligible risk is no risk at all. That we cannot rule out beneficial effects of radiation is also a comforting thought.

“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 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,” Evan Douple, , Associate Chief of Research at the Radiation Effects Research Foundation, Hiroshima, proposed in an e-mail response to me. Dr Evan Douple was director of the Board on Radiation Effects Research that provided oversight to the Biological Effects of Ionizing Radiation (BEIR VII Report).

This is certainly a pragmatic and acceptable way forward. I believe that 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.

Over 26 years ago, NiemanReports listed the Understanding Factors of Risk Perception. The first among the 14 factors was Trust Vs Lack of Trusts.

With understanding trepidation, I read it thus:

“The more we trust the people informing us about a risk, the less afraid we are. The more we trust the process used in deciding whether we will be exposed to a hazard, the less afraid we are. When we trust the agency or company exposing us to the risk, we are less afraid. When we trust government agencies that are supposed to be protecting us, we are less afraid. The less we trust the people informing us, the people protecting us, or the process determining our exposure to a risk, the more afraid we are.”

In any, case “Regulators”: must strive hard to earn the trust, the trust of those whom they serve. I got an opportunity to realize readers impressions when I wrote an article titled, “How safe Kudankulam nuclear power reactors are” in The Hindu on November 10, 2011. I got 93 responses on line and 30 e-mail responses.

Over 50 of the 93 comments and most of the e-mail messages were positive and in favour of safe nuclear power.

“The writer is part of the Nuclear Establishment in India, he has scientific credentials but his entire article is clearly from the Public Relations department of the Koodankulam plant”, one reader wrote.

“The article by the writer, coming close on the heels of green signal given by Dr. Kalam for Nuclear Power / Kudankulam, was very informative and authentic. Just because, the writer belongs to the nuclear establishment, we should not view it with pre-conceived notions, but try to analyse these issues objectively…,” another reader commented.

“A DAE person giving a clean chit to a DAE run plant. What an irony? Who will believe it? I suggest that DAE should get neutral experts from foreign countries, especially people who are known for their integrity, who are not working for supplier companies and countries, which have interest in nuclear plants in India. DAEs trust quotient is very low” was another negative comment (DAE is Department of Atomic Energy; AERB is a functionally independent agency but many consider it as a part of DAE)

Mercifully, other readers balanced the negative views. Thus:

“The above debate is interesting….we often say….one should listen to expert’s views on a given a subject! Yet, some of our friends above have objection, when two eminent scientists & authority speak in favour of Nuke Projects / Kudankulam. What is their fault? They are all ex-officials of same dept. Well, when ex-cricketers Sunil Gavaskar or Kapil Dev speak on cricket with, we all respect their authority on the subject & clap their views. Right, after all, they are experts in the field & we respect / listen to their views. Why on earth double standards then, when two ex – DAE experts speak with authority on Nuke/Kudankulam. One should s and listen to experts & not rabble-rousers. It is indeed shameful that, people are asked to make a choice ….Dr. Kalam or Uday Kumar. Parthsarathy or Pushparayan? Where is the comparison? Let people of our country decide, if they want to go back to Dark Age or bright age!”

“If it is so safe, then Can KSParthasarathy move inside the kudankulam nuclear plant campus if provided a free apartment? Don’t advice for others sitting in a safe place,” a reader suggested.

Since I have superannuated, I cannot get an official residence. Since I did not know his e-mail ID, I blogged that I shall be most grateful if I get a residence in the premises of Kudankulam reactors. I do not need it free, I shall pay rent. I know that the residential premises near nuclear power plants owned by the Department of Atomic Energy are aesthetically appealing!

The comments I received convinced me that the credibility of scientists is not very low as I initially thought. There were a few anti-nuclear activists; we cannot change their views. However, there are many fence sitters waiting for a nudge, based on scientific information.

Everyone must contribute regardless of the perceived trust deficit. Readers of articles and audience attending lectures have access to a lot of material; most of them not authentic. It is appropriate to assist such readers in their quest for accurate and reliable information.

Dr. K S Parthasarathy

Dr. K S Parthasarathy is former Secretary, Atomic Energy Regulatory Board and a former Raja Ramanna Fellow in the Strategic Planning Group, Department of Atomic Energy, Mumbai. Dr. K S Parthasarathy may be contacted at [email protected]

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