Nuclear Radiation: Radiation Protection Standards

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• published: 05 Oct 2016
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http://www.balancedhealthtoday.com/xeneplex.html http://www.balancedhealthtoday.com/store/xeneplex.html In 1952 the International Commission on Radiological Protection (ICRP) issued its recommendations for limiting human exposure to external sources of radiation. The newly formed organisation accepted the standard agreed upon by nuclear physicists from the USA, Canada and the UK after the Second World War. In 1959 it issued its recommendations for limiting human exposure to internal sources of radiation. The early ICRP dose limits per year were: 5 rem to the whole body, gonads or active bone marrow; 30 rem to bone, skin or thyroid; 75 rem to hands, arms, feet or legs; and 15 rem to all other body parts. These standards applied only to `man-made' sources, other than medical exposures for diagnostic or therapeutic purposes of benefit to the patient exposed. ICRP Publication 2, in 1959, recommended no more than 5 rem per year external or internal exposure to the whole body due to inhalation, ingestion or absorption of radioactive chemicals into the body. Sometimes this was misinterpreted and workers were permitted to receive up to 5 rem internal and 5 rem external radiation exposure during one year. Another clause allowing averaging doses over years beyond age 18, gave excuse for still higher doses. In terms of the amount of whole body dose received in a chest X-ray (about 0.03 rem at the present time), this recommendation for workers allowed the equivalent of 400 chest X-rays in some years with a 170 (present-day) chest X-ray average (external and internal) dose a year. Prior to 1970 some X-ray machines used in mass chest X-ray programmes gave as high as 3 rem per chest X-ray. When one looks at dose to bone marrow, the permissible levels are even more troubling. By 1970 the average bone marrow dose for a chest X-ray was 0.001 to 0.006 rem averaging about 0.005 rem. In terms of dose to bone marrow, the ICRP radiation recommendation for workers permits up to the equivalent bone marrow dose of 1,000 chest X-rays per year. ICRP recommended that members of the general public should receive no more than one-tenth of the occupational exposure or 0.5 rem per year, the equivalent bone marrow dose of about 100 present-day chest X-rays per year. The bone marrow dose is important for estimating the likelihood of causing bone cancer, leukaemia, aplastic anaemia or other blood disorders. Medical X-rays are less penetrating of bone than of soft tissue, making them valuable for `picturing' the bones. For this reason comparisons between radiation exposures of nuclear workers and medical X-ray exposures are more appropriately based on the bone marrow dose of each than on dose to soft tissue. These radiation exposure recommendations stayed essentially the same until 1978, when in ICRP Publication 26 a recommendation was made to raise the levels of radiation permitted to humans from man-made sources of radiation (excluding that for medical purposes). For `internal consistency' of the recommendations there was some valid argument for scaling the standards for particular organ exposure in proportion to whole body exposure recommendations -- but scaling down as well as up would have accomplished this. For example, the ICRP reasoned that if the whole body could receive 5 rem per year, the active bone marrow should not be limited to 5 rem per year. This was used as a reason for increasing the permitted bone marrow dose from 5 rem to 42 rem with apparently little regard for the increased damage to bones and blood-producing organs. ICRP Publication 26 also reiterates the need to allow human exposure in order to enjoy the `economic and social benefits' of the nuclear industries. It is difficult to understand how this conclusion was reached when so much new research is available documenting human illness associated with the present permissible exposure levels.[32] Perhaps, in view of contemporary scientific concern for lowering radiation exposures, ICRP Publication 26 recommendations are a political move to hold the line at present regulatory levels. At any rate, it appears to be a document with a political rather than a scientific purpose. Some national regulatory agencies, such as the Atomic Energy Control Board in Canada, promptly implemented ICRP Publication 26 by increasing allowable radium levels in drinking water, thus reducing the clean-up cost for the uranium mining companies. Since some members of the national radiation protection community in Canada and elsewhere hold seats on ICRP, responsibility for what they recommend nationally cannot credibly be attributed to an international recommending body. http://www.balancedhealthtoday.com/store/ http://balancedhealthtoday.com/products.html