Background radiation no evidence for ill-effects

Background radiation: no evidence for ill-effects

Cancer occurrence not consistently higher in monazite-rich areas

RECENTLY, A section of the media published stories about excess cancer deaths in the high background radiation areas (HBRA) in Kerala and Tamil Nadu.

But scientific studies do not substantiate such claims. The natural radiation levels are high in these areas primarily because of the presence of monazite (thorium ore) in soil.

Ionising radiation can cause mutations in all parts of the cell including the DNA. Dr Lucy Forster from the University of Cambridge and her team analysed mitochondrial DNA from 248 families (mostly over three generations) that have been exposed to natural radiation throughout their lives.

Widely published

They found 22 mutations in individuals from the high radiation areas and one in persons from areas of low radiation (Proceedings of the National Academy of Sciences, 2002).

The media widely published the results as the authors, during interviews, suggested that people exposed to even low levels of radiation may be at risk of cancer.

BBC's headline was `cancer risk for radiation workers.' Responding to my queries, Ray Dunne, Health Reporter, BBC news online agreed that BBC did not suggest that that was the conclusion of the original research.

BBC focused on it as it was of more relevance to more people. It was purely speculative. A mutation to manifestation of cancer involves several steps.

Low doses

Responding to my e-mail query, Prof K.Sankaranarayanan, Professor Emeritus, Leiden University Medical Centre, The Netherlands, stated that at the current state of knowledge, we cannot attach any importance to these mutations from the standpoint of adverse health effects at low doses of radiation.

He must know as he wrote all the reports on genetic effects of radiation for the United Nations Scientific Committee on the Effects of Atomic Radiation!

"It might be worth considering whether to lower the allowed limits for radiation workers of reproductive age," Dr Peter Forster, one of the authors, warned.

Exposed populations

"It is premature to try to draw any conclusion concerning cancer risk from the study, let alone to call for a reduction in dose limits etc... " After all, our risk estimates (which form a part of the basis for dose limitation) are computed from epidemiological data on populations exposed to radiation. In other words, although we may have been unaware of this particular mechanism, its contribution to the total risk due to the combinations of mutations is already taken into account, automatically," Dr Jack Valentin, a geneticist and Scientific Secretary of the International Commission on Radiological Protection — the agency which recommends dose limits, clarified in an e-mail response.

Survey result

In a thorough health survey of about 400,000 people (100,000 from HBRA), researchers from the Regional Cancer Centre and Bhabha Atomic Research Centre did not see that cancer occurrence is consistently higher because of external gamma radiation exposure in the monazite-rich areas (Radiation Research, 1999).

Scientists did not observe significant differences in any of the reproductive parameters between the two population groups based on monitoring of 26,151 newborns from HBRA and 10,654 from areas of normal background radiation in the Kerala coast.

The stratification of newborns with malformations, still births or twinning showed no correlation with the natural radiation levels in different areas. (Radiation Research, 1999)

Critical review

In a critical review, of the health studies at HBRA carried out by different authors till 1981, Dr K.S.B. Rose, UK Atomic Energy Research Establishment, Harwell concluded that none of them produced any reliable evidence that the high level natural radioactivity in the area has a detectable adverse effect on the inhabitants (Nuclear Energy, 1982). More recent studies published in peer reviewed journals led to the same conclusion.

Further studies

The studies at HBRA carried out by different agencies have been scattered and limited. Epidemiology must complement molecular genetics, which currently employs tools of unparalleled sensitivity.

India, with advanced technology, must build a national institute at HBRA, modelled more or less like Radiation Effects Research Foundation, Hiroshima, to carry out "research in clinical medicine, epidemiology, statistics, genetics and molecular biology"; an advanced school of radiobiology and allied sciences may be a spin-off from the institute.

K.S.PARTHASARATHY

Former Secretary, AERB
(ksparth@yahoo.co.uk)

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