Assessment of /sup 99/Tc releases to the atmosphere: a plea for applied research. [Dose to man through food chain concentration] Article Swipe
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· 1978
· Open Access
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· DOI: https://doi.org/10.2172/6851868
· OA: W304334331
Recent experimental data suggest that the concentration factor for uptake of /sup 99/Tc by vegetation from soils may be two to three orders of magnitude higher than the 0.25 value currently being used in radiological assessments. Following a survey of the literature, a concentration factor of 50 was applied to evaluate the dose from a 1.0 Ci/year release to the atmosphere by a hypothetical uranium enrichment facility. Doses to the GI tract and thyroid of an adult living 1600 m from the facility were 18 millirems and 80 millirems, respectively. These doses are delivered entirely through transport of /sup 99/Tc through food chain pathways. This assessment indicates a potential for /sup 99/Tc exposures to exceed recently proposed standards of the U.S. Environmental Protection Agency in 40 CFR 190. The previously assumed concentration factor of 0.25 would have produced corresponding doses of 0.13 millirem to the GI tract and 0.57 millirem to the thyroid. The results of this analysis demonstrate the need for additional research on the environmental behavior and dosimetry of /sup 99/Tc. In particular, data are needed to elucidate the retention of /sup 99/Tc in soils and the uptake of /sup 99/Tc by edible vegetation in field studies of chronic exposure conditions. Data on the uptake and retention of /sup 99/Tc in humans are also necessary to improve the reliability of dose conversion factors for specific organs and various age groups.
