How Natural Radioactivity Harms Goans
By Dr Nandkumar M Kamat
After the Japanese nuclear catastrophe I have been researching material which can tell us something on the natural radiation dose to which we here in Goa get exposed. This work is absolutely necessary in public interest because people are now concerned about operational Kaiga and the proposed Jaitapur mega nuclear reactors. My own university and the nearby NIO had been a great disappointment in this regard. Scientists from these public funded institutes need to proactively reveal any information about natural background radiation which they have for any location or samples in Goa. There is a solid lid on such information which is a sad comment on our research culture. But the published research since 1986 is now available from radiation health physicists outside Goa.
Neither the Goa state pollution control board nor the state STE department has cared to prepare and disclose a natural radiation Atlas of Goa. So people are taking chances with their lives and the medical sector is blindly ruling out natural radiation and the atmospheric nuclear fallout which we get in Goa as the probable potential cause of various cancers.
What is natural radiation? I referred to the publication of health physics division of BARC (1986) by Nambi and co-workers. According this publication, nearly 75 per cent of the radiation dose to the public arises from the natural background. BARC claims that mankind has in fact evolved in a natural background radiation environment which can be basically divided into four components: (i) cosmic rays originating in outer space: it has a slight variation with the latitude but increases markedly with altitude. (ii) primordial radioactivity in the rocks and soils: the outer half-metre layer of the earth’s crust contributes effectively to almost all of this component of the background radiation at any location; the radioistopes responsible are daughter products of natural U and Th and K-40. (iii) internal radioactivity distributed within the body in its tissues: the major contribution arises from K-40. (iv) lung irradiation due to radon and thoron inhaled through air and their daughter products; this is generally higher inside a building because of restricted ventilation.
What is intriguing on the background of the veil of secrecy by Goa government is the justification given by BARC for understanding the levels of background natural radiation. BARC believes that – “A knowledge of the population exposure to natural radiation and the general distribution of exposure as is not only important for its own sake but also because: (i) it creates a proper perspective vis-à-vis the radiation insult caused by the nuclear industry and (ii) it helps in epidemiological studies correlating radiation exposure.
BARC report conducted studies in Panaji and Marmagoa and concluded in 1986 that the radiation levels were below the natural average for these two stations. They calculated Goa’s per capita natural radiation dose as 600 microSieverts per year and population dose as 215 Sieverts per year estimated with 1981 census data. For the members of public, the maximum permissible whole body effective dose limit is 1000 microSieverts in a year. So BARC reports indicate that people in Panaji and Marmagoa receive only 60 per cent of the dose. But both these towns account for only 15 percent of the state’s population and less than half a percent of geographical area.
What the BARC missed has been published by Scientist D N Avadhani and his colleagues from Mangalore University. In their October 2001 study titled - Dietary intake of 210Po and 210Pb in the environment of Goa of south-west Coast of India. Both these are potent poisons-notorious slow killers. They dealt with the distribution and activity intake of 210Po and 210Pb in food, diet, and potable water samples of Goa. They estimated committed effective dose due to ingestion of these radionuclides. They detected activity concentrations of 210Po and 210Pb in about 30 food and diet samples from different places of Goa in order to know the distribution and intake of these radionuclides. They were surprised to find that activity concentration of 210Po in fish and prawn samples were significantly higher than concentrations found in vegetable and rice samples. Higher concentrations of 210Po and 210Pb were observed in leafy vegetables than in non-leafy vegetables. Among the diet samples the activity concentrations of 210Po and 210Pb in non-vegetarian meal samples were relatively higher than in vegetarian meal and breakfast samples. The committed effective dose due to annual intake of 210Po was found to be 94.6 microSv, 49.1 microSv, 10.5 microSv, and 2.2 microSv and that of 210Pb found to be 81.6 microSv, 59.9 microSv, 14.6 microSv, and 2.0 microSv for the ingestion of non-vegetarian meal, vegetarian meal, breakfast, and potable water, respectively. So we would like to know the official stand of FDA authorities of Goa about the natural radiation levels in our diet.
In another paper (2005) authored by Dr Avadhani it has been proven that radioactive Radium and Polonium is deposited in Goa from atmospheric precipitation. This study also found that Radioactive Radium, Thorium and Potassium leaches out from granite rocks of Canacona where they detected higher levels of these radionuclides.
Canacona soils have higher levels of radioactive Radium, Potassium and Thorium. Then why did all the medical research teams which investigated the causes for the kidney failures in Canacona taluka ignore this dangerous dimension? Along with alkaline groundwater I have suspecting that the natural radioactivity could be a cause of the high prevalence of kidney diseases in Canacona. I won’t be surprised if this lead proves to be correct.
The Government of Goa needs to have an active collaboration with Dr Avadhani’s team to survey and sample all rocks, minerals, soil types, water resources, vegetation and come out proactively with a detail village and town wise natural radiation map of Goa. People have right to know that the place where they live or the tourists reside is normal from radiation angle, the houses have tolerable Radon emissions, drinking and irrigation water and locally grown food which they consume is safe from radionuclide contamination. The world 25 years after Chernobyl disaster is now moving very cautiously on anything that is nuclear. Many genetic disorders, tumours and cancers could be accounted Our government is afraid to tell us how much natural radiation which we, including the cabinet ministers and MLAs receive and what radionuclides we get from our diet. Even the granite tiles and tabletops generate radioactivity. But there are no standards for such materials in India.