PF-32/2015 February 21, 2015
Can we relax radiation protection standards?
Dr K S Parthasarathy
Kerala is famous for high literacy, high life expectancy, low levels of infant mortality and low population growth. Presence of high background radiation areas with high population density is another noteworthy feature of Kerala. Relaxing radiation protection standards based on the reassuring studies of these populations has been a topic of discussion among a section of the world scientific community.
. “Kerala has a very high rate of background radiation due to sands containing thorium. The level ranges from about 70 percent above the global average to about 30 times the global average. For thousands of years, some of the population of Kerala have been living bathed in radiation at more than triple the level which will get you compulsorily thrown out of your home (evacuation) in Japan”, Geoff Russell, a maverick pronuclear blogger wrote in his guest post titled “What can we learn from Kerala” on Brave New Climate blog on January 24, this year.
He seems to have done his homework well.
His article was packed with so much interesting information on Kerala that this writer struggled hard to add some new points as comments. Keralites burn 8 million tonne of firewood annually to cook rice alone! He quotes a report from the Energy Management Centre, Kerala to prove the point. I brought to his notice the fact that in Kerala, the cooking pattern has changed. A 2012 report revealed that from 5 m to 9am Kerala needs 200 MW of electricity additionally just to satisfy the households using about 100,000 induction cookers. This may go up to 300 MW as the actual number of induction cookers in use may be 150,000. Since he is a pronuclear blogger I informed him that 266 MW, Kerala’s share of power from the newly commissioned 1000 MW Kudankulam nuclear power plant may not be enough to keep those cookers on load.
Coming back to high background radiation areas. There is a misunderstanding that the radiation level in the entire Kerala is high. Actually, the High Level Natural Radiation Area (HLNRA) in Kerala is a strip of land of about 55 km long and 0.5 to 1.5 km wide. Just over 173,000 (1.73 lakhs) out of the Kerala population of 330, 00,000 (330 lakhs) live in the area for generations.
What excited Mr Russell was a paper in Health Physics Journal in 2009, which concluded that researchers found no excess cancer risk from exposure to terrestrial gamma radiation in HLNRA They estimated the radiation doses to 69,958 persons.
HLNRA has a high density of stable, non-migratory population living in the area for generations and exposed to a wide range of doses providing an invaluable opportunity to investigate health effects of low-level chronic radiation exposure directly on human population. Radiation exposures to people in these areas are of the same order as occupational radiation doses.
“People getting a dose of 500 mSv should show a measurable rise in cancer rates. They did when the dose was delivered quickly as with atom blasts. They don’t at Kerala”, he asserted.
Apparently, he was not aware of several other studies
In a study published in PLoS one in February 2009 researchers from the National Institute of Immunology looked for possible structural variations in the Y chromosome in blood and semen samples of 390 males of two generations at two high radiation regions of Kerala. They used similar samples from 390 healthy unexposed males of matched age groups from Kochi (Kerala) and 400 normal males from different parts of India.
They found that in the samples from HLNRA “the germ line is protected because the human genome has some unknown but powerful mechanism of protecting it,”
“Natural radiation poses no major risk” Dr K S Jayaraman, eminent science journalist concluded after reviewing the study
In 2012, a case -control study published in Radiation Research concluded that the prevailing high-level natural radiation in the study area does not appear to increase the risk of either mental retardation or cleft lip/palate among offsprings of parents staying in the area.
In yet another paper published in 2012 in Journal of Community Genetics, researchers working in Low Level Radiation Laboratory in the area and the physicians from the Department of Paediatrics, Victoria Hospital, Kollam, Directorate of Health Services, Government of Kerala did not find significant differences in the prevalence of stillbirths, heart disease, or birth defects, at different radiation dose levels at parental residence. They studied 141,540 newborns from 140,558 deliveries from August 1995 to June 2011.
They faced a major problem. Researchers had to wait patiently to get enough numbers of newborns! Birth rates in Kerala population are low as families follow family planning practices universally.
Researchers did not spare their favourite mouse in the studies. During early 60s, Dr A R Gopal Ayengar, renowned geneticist, and Dr Gruneberg, an authority on the genetics of Indian rat and mice and Dr LH Gray an eminent radiobiologist and their team observed 438 black rats from eight villages of HLNRA and 458 rats away from HLNRA. Their measurements of teeth, skull, mandibles and other bony structures did not show any strong and consistent pattern of difference. They failed to see differences in pregnancy rates, fertility and survival of zygotes while in uterus.
The WHO Expert Committee on Radiation during the 60s and The French Academy of Sciences in 2005 commented specially on the importance of the studies carried out in HLNRA
Presently researchers in advanced countries use micro-beams of various types of radiation of different energies to study biological response of single cells They believe that use of tools and techniques of unparalleled sensitivity along with developing “system biology” will lead to mechanistic models which may help to unravel various phenomena at low dose levels and low dose rates. 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.
[Dr. K S Parthasarathy is a former Secretary of the Atomic Energy Regulatory Board]