Health

Can radiation protection standards be based on best science?

Shortly after the discovery of x-rays and radium,scientists found that radiation can damage the skin. Photo: Special Arrangement

Shortly after the discovery of x-rays and radium,scientists found that radiation can damage the skin. Photo: Special Arrangement  

Are the current radiation protection standards based on best science? Can we improve them now, by using advanced scientific knowledge, tools and techniques which were not available two decades ago?

Too stringent radiation protection standards will impose humongous expenditure on society; too liberal standards may cause unacceptable health impact for the population. Is it proper to spend astronomical amounts to reduce patently trivial radiation risks to still lower values?

During the early years, many who handled x-ray equipment and radium carelessly died. Shortly after the discovery of x rays and radium, scientists found that radiation can damage the skin. The aim of the first radiation protection standard was to avoid obvious radiation injuries. Over the years, as more information became available, the specialists lowered the dose limits substantially to the present values.

High level radiation exposures may cause cancer.

Scientists accepted a prudent approach to derive radiation protection standards based on the Linear No Threshold (LNT) hypothesis which states that the response to radiation is proportional to dose without a threshold.

LNT hypothesis is shaky in the low dose region. That the smallest dose may initiate cancer is un-provable. This led to needless controversies even among scholarly bodies, though workers have been handling radiation sources safely for over a century.

In a cell exposed to radiation, the precisely set cell multiplication mechanism may fail; it may multiply uncontrollably causing cancer. Cell repair takes place at low doses; but we are not sure whether the repair will be perfect or not.

Scientists have developed micro-beams to study how single cells behave when hit by all types of radiation (alpha particles, electrons and x-rays) of different energies. They can now record a single Double Strand Break (DSB) of DNA. DSB may be important in cancer induction.

Using these tools and techniques of unparalleled sensitivity, scientists unravelled biological responses such as bystander effects, adaptive response, and genomic instability and challenged the notion that cancer originates in a single cell

Cells hit by radiation communicate with neighbouring cells which are affected either directly, or indirectly from release of substances into blood. We do not fully know the importance of bystander effects.

Scientists found that cells exposed to low doses change their response to a subsequent radiation exposure. The adaptive response became controversial because of the claim that it proves the beneficial effects of low dose radiation!

After getting hit by radiation, cells may divide and return to their normal state. The cells formed after a few divisions had abnormalities in their chromosomes. This genomic instability occurs frequently.

Low dose research supported by US Department of Energy during 1998-2008 revealed a lot; but was not enough to arrive at more scientific standards.

In a review published in Radiation Research (2013), Drs W.F Morgan and W. J Blair of Pacific North West National Laboratory, U.S. suggested that ‘system biology’ approach may help to resolve the complex issues.

The International Commission on Radiological Protection (ICRP) arrived at radiation risk estimates based primarily on human epidemiology; this includes the effects, if any, of adaptive response, bystander effects and genomic instability in the final outcome. They may not influence radiation risk estimates. Thus the present ICRP recommendations on dose limits are based on sound judgment, and are robust and pragmatic. All scholarly bodies agree that so far, researchers did not find any evidence for a threshold dose.

Many extensive studies of tens of thousands of radiation workers show that the impact, if any, of low dose exposures is acceptably low. In spite of being the most studied agent, why public considers radiation differently?

When we use antibiotics, we trust the tests done to study them. We feel assured that, when clinically indicated and the doses are right, benefit far outweighs the possible harm. Scientists must convince the public that radiation risks are better studied than risks from drugs.

“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....,” Ian Douple, Associate Chief of Research at the Radiation Effects Research Foundation, Hiroshima, proposed in an e-mail response to this writer.

That is the way forward. Over emphasis on hormesis and over simplification of some observations by medical and nuclear enthusiasts may not be appropriate. Not yet. Low dose research must continue. There are no short cuts. Using the correct information, we disseminate, discerning public will make the right choice.

K. S. Parthasarathy, Former Secretary, Atomic Energy Regulatory Board

ksparth@yahoo.co.uk

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Printable version | Sep 20, 2020 8:07:55 AM | https://www.thehindu.com/sci-tech/health/can-radiation-protection-standards-be-based-on-best-science/article7057861.ece

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