Model for estimating population impacts averted through the remediation of contaminated soil.

This is the second in a series of papers that discuss methodologies being developed and employed by the U.S. Environmental Protection Agency in support of its decisions on cleanup levels for radioactively contaminated sites that are to be remediated and released for public use. It describes a model, CU-POP, designed by the U.S. Environmental Protection Agency to obtain estimates of the potential collective radiological health impacts over specific periods of time (100, 1,000 and 10,000 y following cleanup), both on and off site, due to residual radioactive materials in on-site soil. Collective doses and risks are linear in population density for the direct exposure, dust and indoor radon inhalation, and soil ingestion pathways; it is assumed that specific fractions of all food grown and all groundwater pumped at a site are consumed by on- and off-site populations. The model was developed for application to a set of hypothetical "reference" sites; its testing on a simple generic site is discussed briefly here.

Technical basis for EPA's proposed regulation on the cleanup of sites contaminated with radioactivity.

The U.S. Environmental Protection Agency is proposing a regulation for the protection of the public from radioactive contamination at sites that are to be cleaned up and released for public use. The rule will apply to sites under the control of Federal agencies, and will impose limits on radiation doses to individuals living or working on a site following cleanup; it will thereby provide site owners and managers with uniform, consistent cleanup criteria for planning and carrying out remediation. This paper presents an overview of EPA's approach to assessing some of the beneficial and adverse effects associated with various possible values for the annual dose limit. In particular, it discusses the method developed to determine how the choice of cleanup criterion affects (1) the time-integrated potential numbers of non-fatal and fatal radiogenic cancers averted among future populations, (2) the occurrence of radiogenic cancers among remediation workers and the public caused by the cleanup process itself, and (3) the volumes of contaminated soil that may require remediation. The analytic methods described here were used to provide input data and assumptions for the Regulatory Impact Analysis (RIA) that supports the proposed regulation; the RIA also considered non-radiological benefits and costs (i.e., public health, economic, and ecological) of the standards.

Xenon: effect on radiation sensitivity of HeLa cells.

HeLa cells, plated onto plastic petri dishes, were exposed to various atmospheres composed of air and carbon dioxide; helium, oxygen, and carbon dioxide; and xenon, oxygen, and carbon dioxide in a pressure vessel. Survival curves with x-rays, 280 kilovolts (peak), show that air and helium have the same effect, but that xenon potentiates x-irradiation to the extent that the dose to produce a given level of survival with xenon is 0.58 of the dose required with air.