Toward the framework and implementation for clearance of materials from regulated facilities.

The disposition of solid materials from nuclear facilities has been a subject of public debate for several decades. The primary concern has been the potential health effects resulting from exposure to residual radioactive materials to be released for unrestricted use. These debates have intensified in the last decade as many regulated facilities are seeking viable management decisions on the disposition of the large amounts of materials potentially containing very low levels of residual radioactivity. Such facilities include the nuclear weapons complex sites managed by the U.S. Department of Energy, commercial power plants licensed by the U.S. Nuclear Regulatory Commission (NRC), and other materials licensees regulated by the NRC or the Agreement States. Other facilities that generate radioactive material containing naturally occurring radioactive materials (NORM) or technologically enhanced NORM (TENORM) are also seeking to dispose of similar materials that may be radioactively contaminated. In contrast to the facilities operated by the DOE and the nuclear power plants licensed by the U.S. Nuclear Regulatory Commission, NORM and TENORM facilities are regulated by the individual states. Current federal laws and regulations do not specify criteria for releasing these materials that may contain residual radioactivity of either man-made or natural origin from regulatory controls. In fact, the current regulatory scheme offers no explicit provision to permit materials being released as "non-radioactive," including those that are essentially free of contamination. The only method used to date with limited success has been case-by-case evaluation and approval. In addition, there is a poorly defined and inconsistent regulatory framework for regulating NORM and TENORM. Some years ago, the International Atomic Energy Agency introduced the concept of clearance, that is, controlling releases of any such materials within the regulatory domain. This paper aims to clarify clearance as an important disposition option for solid materials, establish the framework and basis of release, and discuss resolutions regarding the implementation of such a disposition option.

Application of the Supreme Court's Daubert criteria in radiation litigation.

In 1993, the U.S. Supreme Court set forth the standard for determining the admissibility of expert scientific evidence in litigation. This standard is known as the Daubert criteria, named after the pertinent case, Daubert v. Merrell Dow Pharmaceuticals, Inc. The Daubert criteria require the courts to determine whether an expert's testimony reflects scientific knowledge, whether his/her findings are derived by the scientific method, and whether the work product is based on good science. The Daubert criteria are especially important in radiation litigation because issues involving radiation doses and effects are often complex and thus a jury will typically rely heavily on the analysis and opinions of experts. According to the Daubert criteria, scientific opinions must be based on a methodology that has a valid, testable hypothesis; has been subject to peer review; and is generally accepted in the scientific community. Additionally, the expert must be qualified to present opinions based on the methodology. Although the application of the Daubert criteria in radiation litigation is highly dependent on the specific court and judge presiding over the case, there have been recent high-profile cases in which application of the criteria has resulted in the dismissal of analysis and opinions offered by scientific experts. Reasons for the dismissals have included basic scientific errors such as failure of the expert to consider all possible explanations for an observed phenomenon, the selective use of data by the expert, and the failure to acknowledge and resolve inconsistencies between the expert's results and those of other investigators. This paper reviews the Daubert criteria as they apply to radiation litigation and provides examples of the application of the criteria from recent judgments involving the Three Mile Island and Hanford Downwinders cases.

Evaluation of uncertainties in estimates of fetal doses from 59Fe kinetic studies at Vanderbilt University.

In a 1997 paper, Stabin et al. published estimates of the fetal radiation doses for women who received oral administrations of 59Fe at Vanderbilt University in the 1940's. These authors concluded that there was "considerable uncertainty... in the amount of radioactive material administered to these subjects." In an effort to quantify this uncertainty, the underlying factors in the input data used in the Stabin et al. dose estimates have been examined in detail. Such factors include (a) an absence of detailed information on, and discrepancies in, the amounts of 59Fe reported to have been administered; (b) the probability that the radioactive iron included 55Fe as well as 59Fe; (c) uncertainties as to the period of time that elapsed between the administration of the radioiron and the taking of the maternal blood samples, and the accompanying impacts of radioactive decay; (d) possible losses of 59Fe in the procedures used in preparing the blood samples; and (e) questions as to the reported efficiency of the counting equipment. Our principal conclusion is that, due to the significant uncertainties and the lack of key information, it is not possible to estimate the doses accurately. An ancillary conclusion, however, is that the doses were probably significantly higher than previously estimated. This latter possibility should be carefully considered by any investigators who subsequently seek to use these estimates to quantify the relationship between the doses to the fetus and the resulting health effects.

Optimization of filtration for reduction of lung dose from Rn decay products: Part I--Theoretical.

A theoretical model was developed for the optimization of filter characteristics that would minimize the dose from the inhalation of Rn decay products. Modified forms of the Jacobi-Porstendorfer room model and the Jacobi-Eisfeld lung dose model were chosen for use in the mathematical simulation. Optimized parameters of the filter were the thickness, solidity, and fiber diameter. For purposes of the calculations, the room dimensions, air exchange rate, particle-size distribution and concentration, and the Rn concentration were specified. The resulting computer-aided optimal design was a thin filter (the minimum thickness used in the computer model was 0.1 mm) having low solidity (the minimum solidity used was 0.5%) and large diameter fibers (the maximum diameter used was 100 microns). The simulation implies that a significant reduction in the dose rate can be achieved using a well-designed recirculating filter system. The theoretical model, using the assumption of ideal mixing, predicts an 80% reduction in the dose rate, although inherent in this assumption is the movement of 230 room volumes per hour through the fan.

Optimization of filtration for the reduction of lung dose from Rn decay products: Part II--Experimental.

Research was performed to determine the validity of a model developed to theoretically predict the optimal characteristics of a recirculating filter system for minimizing the lung dose to a person breathing airborne Rn progeny. Four designs, each with different filter thicknesses, solidities, and fiber diameters, were tested to evaluate the accuracy of the model over a range of parameters. Increasing thicknesses were then tested for the most effective filter design to provide a more definitive comparison of experimental data and model predictions for this key parameter. The experimental data supported the conclusion that the most effective design was a thin filter of low solidity composed of coarse fibers. Although the maximum reduction in the dose-equivalent rate observed in these experiments was 50%, this was largely due to constraints on the experimental arrangements. With properly constructed filter units, much better removal efficiencies can undoubtedly be achieved.

Radiological health effects models for nuclear power plant accident consequence analysis.

Improved health effects models have been developed for assessing the early effects, late somatic effects and genetic effects that might result from low-LET radiation exposures to populations following a major accident in a nuclear power plant. All the models have been developed in such a way that the dynamics of population risks can be analyzed. Estimates of life years lost and the duration of illnesses were generated and a framework recommended for summarizing health impacts. Uncertainty is addressed by providing models for upper, central and lower estimates of most effects. The models are believed to be a significant improvement over the models used in the U.S. Nuclear Regulatory Commission's Reactor Safety Study, and they can easily be modified to reflect advances in scientific understanding of the health effects of ionizing radiation.

Effective removal of airborne 222Rn decay products inside buildings.

Comparisons were made of the effectiveness of various indoor air treatment methods in reducing the lung dose due to inhalation of 222Rn decay products. The comparisons were based upon measurements of the total steady-state concentrations of 218Po, 214Pb and 214Bi, and the concentrations of these nuclides not attached to particles. These measurements, which were made inside a 78-m3 room before and after air treatment, were used along with a state-of-the art lung dose model to predict reductions in the dose to the radiosensitive bronchial tissues. Results suggest that flow-through air-cleaning methods, such as filtration and electrostatic precipitation, although effective in reducing total potential alpha energy concentration, cause a greater quantity of airborne potential alpha energy to be unattached to particles. This may result in a substantial increase in the dose to bronchial tissues. The optimal form of air treatment appears to be a combination of nonuniform positive space charge generated by an ion generator and enhanced convection from a fan. This combination of air treatment gave reductions in the mean dose to the bronchial tissues of up to 87%.

Airport preparedness for mass disaster: a proposed schematic plan.

With the growth in the size of airplanes and the number of flights, the potential impact on airports of airplane-related disasters involving large numbers of people is increasing. Such disasters may result from accidents or terrorist activities. Although the development of plans for coping with such situations is a prerequisite to full certification of airports by the FAA, exercising the plans through disaster drills is only a recommendation. This has resulted in a situation where only a small minority of the fully certified airports are actually ready to handle a major disaster. Presented in this paper is a proposed schematic plan for handling the medical aspects of airport disasters, including a discussion of the relevant background issues.

Cost evaluation of control measures for indoor radon progeny.

Based on assumed conditions within a typical U.S. home, annualized costs for reducing indoor airborne radon progeny concentrations have been calculated for a variety of methods of control. These analyses were limited to methods for control in existing homes. Control through modified construction techniques was not evaluated. Methods assessed included increased air circulation, increased ventilation, particle removal using electrostatic precipitation and unipolar ion generation, and the application of sealants to room surfaces. Although surface sealants proved to be reasonably cost-effective per person- sievert dose reduction, such sealants are prone to cracking and the durability of their effectiveness is questionable. Use of ceiling fans for increased air circulation and particle deposition appears to be least cost-effective, but this method may be attractive in some cases for reasons of comfort. The use of unipolar ion generators appears to be the best approach from the standpoint of cost effectiveness. These devices are also easy to install and are esthetically readily acceptable.

Survey of industrial hygiene short course training.

Approximately 2400 short courses were presented in the U. S. for environmental health professionals from 1977 through 1979. During 1977, over 30% of these courses pertained to the field of industrial hygiene. By 1979, this had increased to 41% and the average annual growth rate in the number of such courses was over 75%. A major part of this growth is attributable to private sector companies which offered 67% of the industrial hygiene courses presented during the first half of 1979, up from 35% in 1977. Profiles of industrial hygiene course participants showed that the majority were mid-career professionals. Their average age was 37.5 years, over 86% were males, and 85% had college degrees.

Dental x-ray use in Boston.

A telephone survey of 40 dental offices in Boston, Massachusetts, revealed that 95 per cent perform x-ray procedures as part of the initial examination of a new patient, that almost one-half (47.5 per cent) routinely include a full-mouth x-ray series in the initial examination, and that 85 per cent include some type of radiographic procedure as part of the periodic visits for cleaning and checkups. These percentages are substantially in excess of those reported by other investigators in which the respondents were aware that their policies with respect to the use of x-rays were being evaluated.

Trends in university environmental health research and training.

A survey of 157 college and university programs in the United States indicates that, during the ten-year period from 1967 through 1976, the number of people completing graduate programs in environmental health specialties at the master's, doctoral, and post-doctoral levels doubled. In 1974-75, 75 per cent of those completing master's degree programs were in the specialty areas of water pollution, air pollution, and occupational health; 76 per cent of those completing doctoral programs were in water pollution, toxicology, radiation protection, air pollution, and cancer research; and 61 per cent of those completing post-doctoral programs were in cancer research and toxicology. Including those whose current positions could not be ascertained, less than 10 per cent of all graduates accepted employment outside the field of environmental health. Funding for university environmental health research continued to increase throughout this ten-year period. The sources of this funding, however, changed dramatically, with the relative contributions from the U.S. Department of Health, Education, and Welfare decreasing significantly, while those from industry and other federal agencies increased. In contrast, funding for university environmental health training increased significantly between 1966 and 1971, but showed no increase from 1971 to 1975. During this latter period, training support provided by HEW remained essentially constant, that by the Environmental Protection Agency decreased to less than half, while that from the universities approximately tripled. (Am. J. Public Health 69:125-129,1979.)