Revising Strontium-90 Radiation Standards for Environmental Cleanup. W. C. Griffith, Department of Environmental Health, University of Washington, Seattle, WA; S. B. Curtis, Fred Hutchinson Cancer Research Center, Seattle, WA; and S. M. Bartell and E. M. Faustman, Department of Environmental Health, University of Washington, Seattle, WA
Standards for exposure to ionizing radiation from internally deposited radionuclides were developed by advisory organizations using simple and consistent models that can be applied for all radionuclides, chemical forms, types of radiation, and combination of target tissues—even in cases where little or no data is available. The simple models should be reviewed, based on the best scientific information, when their application leads to a long-term effort at high cost for environmental cleanup. Cleanup of Strontium-90 contaminated groundwater at the Hanford Nuclear Reservation by the U.S. Department of Energy is used as an example. The health effects of soluble Sr-90 have not been studied in human populations and are inferred to be bone cancers and leukemia based on studies of other types of radiation exposures. The scientific evidence suggests that the standard should be changed, based on a dose threshold for bone cancer observed in people exposed to other radionuclides and in laboratory animal studies. The scientific evidence for leukemia suggests the standards do not need to be modified for this effect, the leukemia risks extrapolated using a linear-quadratic dose response from studies of the atomic bomb survivors are appropriate. The standard for Sr-90 would increase by 56% based on this change. Although this is a relatively modest change in the standard it could lead to substantial cost savings because of the reduction of the extent of the area at Hanford needing cleanup.
Supported (not endorsed) by CRESP by Department of Energy Cooperative Agreement #DE-FCO1-95EW55084.
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