Year : 2013 | Volume
: 36 | Issue : 3 | Page : 97--98
Exposure to natural sources: Why the concern?
Division of Radiation, Transport and Waste Safety IAEA, Vienna, Austria
P P Haridasan
Division of Radiation, Transport and Waste Safety IAEA, Vienna
|How to cite this article:|
Haridasan P P. Exposure to natural sources: Why the concern?.Radiat Prot Environ 2013;36:97-98
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Haridasan P P. Exposure to natural sources: Why the concern?. Radiat Prot Environ [serial online] 2013 [cited 2020 Nov 25 ];36:97-98
Available from: https://www.rpe.org.in/text.asp?2013/36/3/97/137467
Exposures to natural sources of radiation and control have been a subject of concern among regulators, operators, workers, and public at large in the past decades. Natural radionuclides are omnipresent and to fix a level above which it is judged to be appropriate to introduce radiation protection measures is sometimes challenging and is hard to convince.
There is considerable progress in achieving broad international consensus on managing exposure to natural sources over time. However, the standards and regulatory approaches being adopted at the national level still need to be harmonized in many countries. A large effort is underway at national and international level to assess exposure to naturally occurring radioactive material (NORM) and to develop strategies to address existing situations that give rise to exposures. UNSCEAR in its report (2008), encourage further development of inventories and methodologies for dose assessment in order to have a more comprehensive view over the topic.
The new International Basic Safety Standards published by the IAEA in 2011 provides requirements for exposure to natural sources and reflect the three types of exposure situation - planned exposure situations, existing exposure situations and emergency exposure situations in line with the 2007 Recommendations of the ICRP. Exposure to natural sources, exposure due to contamination of areas by residual radioactive material from past activities or after a nuclear or radiological emergency and exposure due to commodities containing radionuclides from the residual radioactive material are generally subject to the requirements for existing exposure situations. Exposure control is based on the use of reference levels, defined by the ICRP as levels of dose or risk above which it is judged inappropriate to allow exposures to occur and below which optimization of protection should be implemented. The maximum reference level for exposure to radon is set at 10 mSv/year - corresponding to radon concentrations of 300 Bq/m3 for homes and 1000 Bq/m3 for workplaces. This brings growing challenges for protection against radon in homes, buildings and workplaces, including underground mining and processing of uranium and other non-uranium mines such as copper, iron or coal mines.
There is a growing concern over the exposure to naturally occurring radionuclides at elevated levels. The need for a national radon strategy is often highlighted recently. For exposure to radionuclides in commodities, a maximum reference level of about 1 mSv/year is applicable, ensuring a level of protection similar to that for planned exposure situations, even though the mechanism of control is different. By exception, public exposure to radioactive discharges and waste; occupational exposure to radon when its concentration exceeds 1000 Bq/m 3 or when required by or directly related to the work; and exposure to material (other than commodities such as food, feed, drinking water, fertilizers, and construction materials) with a radionuclide activity concentration exceeding 1 Bq/g of any radionuclide in the uranium or thorium decay chains (or 10 Bq/g in the case of K-40) are subject to the requirements for planned exposure situations. For natural radionuclides, exemption is determined on the basis of dose commensurate with natural background levels (about 1 mSv/year). Clearance criteria for NORM are 1 Bq/g for uranium and thorium series radionuclides and 10 Bq/g for K-40. According to the standards, food, feed, drinking water, agricultural fertilizer, soil amendment, and construction materials are to be treated as existing exposure situations, and national authorities need a long-term strategy for exposure control as well as fixing a suitable reference level.
Accordingly, studies on natural radionuclides in mining sites, building materials, ground water and surface water are important in developing a sensible and practical approach for protection of humans from exposure to the natural sources. In this issue, few such studies from uranium mining sites, ground water concentrations of natural radionuclides and a study on granite rock tiles are being published.
For Further Reading
International Atomic Energy Agency. Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards (Interim edition), GSR Part. 3. Vienna: IAEA;2011.International Atomic Energy Agency. Radiation Protection and NORM Residue Management in the Production of Rare Earths from Thorium containing Minerals, Safety Reports Series No. 68. Vienna: IAEA;2011.International Atomic Energy Agency. Radiation Protection and NORM Residue Management in the Titanium Dioxide and Related Industries, Safety Reports Series No. 76. Vienna: IAEA;2012.International Atomic Energy Agency. Radiation Protection and Management of NORM Residues in the Phosphate Industry, Safety Reports Series No. 78. Vienna: IAEA;2013.International Atomic Energy Agency. Proceedings of the Sixth International Symposium on Naturally Occurring Radioactive Material, Marrakech, Morocco, 22 26 March, 2010, IAEA Proceedings Series;2011.International Atomic Energy Agency. Regulatory Control for Safe Transport of Naturally Occurring Radioactive Material (NORM), TECDOC 1728. Vienna: IAEA;2014.International Atomic Energy Agency. Measurement and Calculation of Radon Releases from Residues, Technical Reports Series No. 474. Vienna: IAEA;2013.International Atomic Energy Agency. Management of NORM Residues, TECDOC 1712. Vienna: IAEA;2013.