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Biophysical and biomathematical adventures in radiobiology

Description: Highlights of my biophysical and biomathematical adventures in radiobiology is presented. Early adventures involved developing state-vector models'' for specific harmful effects (cell killing, life shortening) of exposure to radiation. More recent adventures led to developing hazard-function models'' for predicting biological effects (e.g., cell killing, mutations, tumor induction) of combined exposure to different toxicants. Hazard-function models were also developed for predicting harm to man from exposure to large radiation doses. Major conclusions derived from the modeling adventures are as follows: (1) synergistic effects of different genotoxic agents should not occur at low doses; (2) for exposure of the lung or bone marrow to large doses of photon radiation, low rates of exposure should be better tolerated than high rates; and (3) for some types of radiation (e.g., alpha particles and fission neutrons), moderate doses delivered at a low rate may be more harmful than the same dose given at a high rate. 53 refs., 7 figs.
Date: January 1, 1991
Creator: Scott, B.R.
Partner: UNT Libraries Government Documents Department

Improved Radiation Dosimetry/Risk Estimates to Facilitate Environmental Management Of Plutonium Contaminated Sites

Description: Currently available radiation dosimetry/health-risk models for inhalation exposure to radionuclides are based on deterministic radiation intake and deterministic radiation doses (local and global). These models are not adequate for brief plutonium (Pu) exposure scenarios related to Department of Energy (DOE) decontamination/decommissioning (D&D) operations because such exposures involve the stochastic-intake (StI) paradigm. For this paradigm, small or moderate numbers of airborne, pure, highly radioactive PuO2 particles could be inhaled and deposited in the respiratory tract in unpredictable numbers (stochastic) during D&D incidents. Probabilistic relationships govern intake via the respiratory tract for the StI paradigm. An StIparadigm incident occurred on March 16, 2000, at Los Alamos National Laboratory. It involved eight workers who inhaled high-specific-activity, alpha-emitting (HSA-aE) 238PuO2-contaminated room air (glovebox-failure incident). Health-risk estimation is not trivial for the StI-exposure paradigm, especially for HSA-aE 238PuO2, as different individuals can have very different and uncertain radioactivity intakes for the same exposure duration and same incident. Indeed, this occurred in the Los Alamos incident. Rather than inappropriate point estimates of intake, dose, and risk, more appropriate probability distributions are needed. A main objective of this project has been to develop a stochastic dosimetry/risk computer model for evaluating radioactivity intake (by inhalation) distributions, organ dose distributions, and health risk distributions for DOE workers who may inhale airborne, alpha-emitting, pure PuO2 at DOE sites such as Rocky Flats. Another objective of this project has been to address the deterministic intake (DI) paradigm where members of the public could inhale, over years, millions and more resuspended, air-transported, PuO2-contaminated dust particles while residing (e.g., farmer) or working (e.g., office worker) at a remediated DOE site that contains mainly residual PuO2 (and daughters) in soil.
Date: December 31, 2001
Creator: Scott, B.R.
Partner: UNT Libraries Government Documents Department

Models for pulmonary lethality and morbidity after irradiation from internal and external sources

Description: This report provides a hazard-function model for estimating the risk of death from radiation pneumonitis and/or pulmonary fibrosis following a light-water nuclear power accident. A similar model is also provided for estimating the prevalence of respiratory functional morbidity among those that survive death from acute effects. Hazard-function models for lethality and for morbidity were constructed using the cumulative hazard estimator H, which is related to the risk estimator R through the equation R = 1-exp(-H). The estimator H can be calculated using information provided in the report. The method of calculation depends on the exposure scenario. In general, the total normalized dose X for lethality or for morbidity is calculated. For lethality, X = 1 corresponds to a median lethal dose (LD/sub 50/); for morbidity, X = 1 corresponds to a median effective dose (ED/sub 50/). H is related to X by the equation H = 1n(2)X/sup V/, where V depends on the type of radiation (or radiations) involved. Contributions to X can arise from each of two main modes of exposure: (1) brief exposure of the lung, at a relatively high dose rate, to mainly external gammas, followed by (2) chronic internal alpha, and/or beta, and/or gamma irradiation of the lung. Equations are provided for calculating the contributions to X from both modes of exposure. 73 refs., 16 figs., 2 tabs.
Date: May 1, 1989
Creator: Scott, B.R.; Filipy, R.E. & Hahn, E.F.
Partner: UNT Libraries Government Documents Department

Improved radiation dosimetry/risk estimates to facilitate environmental management of plutonium contaminated sites. 1998 annual progress report

Description: 'The objective of this research is to evaluate distributions of possible alpha radiation doses to the lung, bone, and liver and associated health-risk distributions for plutonium (Pu) inhalation-exposure scenarios relevant to environmental management of PuO{sub 2}-contaminated sites. Currently available dosimetry/risk models do not apply to exposure scenarios where, at most, a small number of highly radioactive PuO{sub 2} particles are inhaled (stochastic exposure [SE] paradigm). For the SE paradigm, risk distributions are more relevant than point estimates of risk. The focus of the research is on the SE paradigm and on high specific activity, alpha-emitting (HSA-aE) particles such as 238 PuO{sub 2} . The scientific goal is to develop a stochastic respiratory tract dosimetry/risk computer model for evaluating the desired absorbed dose distributions and associated health-risk distributions, for Department of Energy (DOE) workers and members of the public. This report summarizes results after 1 year of a 2-year project.'
Date: June 1, 1998
Creator: Scott, B.R.
Partner: UNT Libraries Government Documents Department

Experimental studies of the early effects of inhaled beta-emitting radionuclides for nuclear accident risk assessment: Phase 2 report

Description: This report summarizes a series of experiments concerning the effect of linear energy transfer and temporal radiation dose pattern to the lung from inhaled beta-emitting radionuclides. The results were used to test the validity of a hazard-function mathematical model for predicting death from radiation pneumonitis. Both morbidity and mortality within 18 months after exposure were examined in rats exposed to beta-emitting radionuclides, giving brief or protracted irradiation of the lung or having weak or strong beta emissions. Protraction of the radiation dose to the lung from a half-time in the lung of less than three days to a half-time with a long-term component of about 150 days has a sparing effect. The median lethal dose for the protracted irradiation is about 1.7 times the median lethal dose for the brief irradiation. Low energy beta emissions from /sup 147/Pm have a similar effectiveness in producing lethal injury as high energy beta emissions from /sup 90/Sr. Changes in three parameters of morbidity were measured: body weight, hematology and pulmonary function; only changes in pulmonary function correlated well with pulmonary radiation injury. The doses of radiation required to produce impaired function, however, were not significantly different from those that produced death. The hazard-function model for predicting death from radiation pneumonitis, which was developed from previously obtained data for inhalation exposures of dogs to beta-emitting radionuclides, adequately predicted the median lethal doses for rats receiving one of several different beta dose rate patterns to the lung, thus strengthening the validity of the mathematical model. 23 refs., 41 figs., 12 tabs.
Date: November 1, 1987
Creator: Scott, B.R.; Hahn, F.F.; Newton, G.J.; Snipes, M.B.; Damon, E.G.; Mauderly, J.L. et al.
Partner: UNT Libraries Government Documents Department

Early and continuing effects of combined alpha and beta irradiation of the lung:

Description: This report summarizes an inhalation exposure experiment that concerns early and continuing effects of combined alpha and beta irradiation of the lung of rats. Both morbidity at 18 months and mortality within 18 months after exposure were examined for rats exposed to the beta-emitter /sup 147/Pm, the alpha-emitter /sup 238/Pu, or both combined. The results were used to validate hazard-function models that were developed (1)for pulmonary functional morbidity at 18 months and (2) for lethality from radiation pneumonitis and pulmonary fibrosis within 18 months. Both models were found to adequately predict the experimental observations after combined chronic alpha and beta irradiation of the lung. A relative biological effectiveness of approximately 7 was obtained for /sup 238/Pu alpha radiation compared to /sup 147/Pm beta radiation for both pulmonary functional morbidity and lethality from radiation pneumonitis and pulmonary fibrosis. 12 refs., 16 figs., 11 tabs.
Date: March 1, 1988
Creator: Scott, B.R.; Hahn, F.F.; Snipes, M.B.; Newton, G.J.; Eidson, A.F.; Mauderly, J.L. et al.
Partner: UNT Libraries Government Documents Department

Health effects models for nuclear power plant accident consequence analysis. Modification of models resulting from addition of effects of exposure to alpha-emitting radionuclides: Revision 1, Part 2, Scientific bases for health effects models, Addendum 2

Description: The Nuclear Regulatory Commission (NRC) has sponsored several studies to identify and quantify, through the use of models, the potential health effects of accidental releases of radionuclides from nuclear power plants. The Reactor Safety Study provided the basis for most of the earlier estimates related to these health effects. Subsequent efforts by NRC-supported groups resulted in improved health effects models that were published in the report entitled {open_quotes}Health Effects Models for Nuclear Power Plant Consequence Analysis{close_quotes}, NUREG/CR-4214, 1985 and revised further in the 1989 report NUREG/CR-4214, Rev. 1, Part 2. The health effects models presented in the 1989 NUREG/CR-4214 report were developed for exposure to low-linear energy transfer (LET) (beta and gamma) radiation based on the best scientific information available at that time. Since the 1989 report was published, two addenda to that report have been prepared to (1) incorporate other scientific information related to low-LET health effects models and (2) extend the models to consider the possible health consequences of the addition of alpha-emitting radionuclides to the exposure source term. The first addendum report, entitled {open_quotes}Health Effects Models for Nuclear Power Plant Accident Consequence Analysis, Modifications of Models Resulting from Recent Reports on Health Effects of Ionizing Radiation, Low LET Radiation, Part 2: Scientific Bases for Health Effects Models,{close_quotes} was published in 1991 as NUREG/CR-4214, Rev. 1, Part 2, Addendum 1. This second addendum addresses the possibility that some fraction of the accident source term from an operating nuclear power plant comprises alpha-emitting radionuclides. Consideration of chronic high-LET exposure from alpha radiation as well as acute and chronic exposure to low-LET beta and gamma radiations is a reasonable extension of the health effects model.
Date: May 1, 1993
Creator: Abrahamson, S.; Bender, M. A.; Boecker, B. B.; Scott, B. R. & Gilbert, E. S.
Partner: UNT Libraries Government Documents Department

Inhaled /sup 147/Pm and/or total-body gamma radiation: Early mortality and morbidity in rats

Description: Rats were given doses of /sup 60/Co gamma radiation and/or lung burdens of /sup 147/Pm (in fused aluminosilicate particles) within lethal ranges in an experiment to determine and compare morbidity and mortality responses for the radiation insults within 1 year after exposure. Radiation-induced morbidity was assessed by measuring changes in body weights, hematologic parameters, and pulmonary-function parameters. Acute mortality and morbidity from inhaled promethium were caused primarily by radiation pneumonitis and pulmonary fibrosis that occurred more than 53 days after exposure. Acute mortality and morbidity from total-body gamma irradiation occurred within 30 days of exposure and resulted from the bone-marrow radiation syndrome. Gamma radiation caused transient morbidity, reflected by immediately depressed blood cell levels and by reduced body weight gain in animals that survived the acute gamma radiation syndrome. Inhaled promethium caused a loss of body weight and diminished pulmonary function, but its only effect on blood cell levels was lymphocytopenia. Combined gamma irradiation and promethium lung burdens were synergistic, in that animals receiving both radiation insults had higher morbidity and mortality rates than would be predicted based on the effect of either kind of radiation alone. Promethium lung burdens enhanced the effect of gamma radiation in rats within the first 30 days of exposure, and gamma radiation enhanced the later effect of promethium lung burdens. 70 refs., 68 figs., 21 tabs.
Date: May 1, 1989
Creator: Filipy, R.E.; Lauhala, K.E.; McGee, D.R.; Cannon, W.C.; Buschbom, R.L.; Decker, J.R. et al.
Partner: UNT Libraries Government Documents Department

Inhaled /sup 239/PuO/sub 2/ and/or total-body gamma radiation: Early mortality and morbidity in rats and dogs

Description: Rats and beagle dogs were given doses of /sup 60/Co gamma radiation and/or body burdens of /sup 239/PuO/sub 2/ within lethal ranges in an experiment to determine and compare morbidity and mortality responses of both species within 1 year after exposure. Radiation-induced morbidity was assessed by measuring changes in body weights, hematologic parameters, and pulmonary-function parameters. Gamma radiation caused transient morbidity, reflected by immediately depressed blood cell concentrations and by long-term loss of body weight and diminished pulmonary function in animals of both species that survived the acute gamma radiation syndrome. Inhaled plutonium caused a loss of body weight and diminished pulmonary function in both species, but its only effect on blood cell concentrations was lymphocytopenia in dogs. Combined gamma irradiation and plutonium lung burdens were synergistic, in that animals receiving both radiation insults had higher morbidity and mortality rates than would be predicted based on the effect of either kind of radiation alone. Plutonium lung burdens enhanced the effect of gamma radiation in rats within the first 30 days of exposure, and gamma radiation enhanced the long-term effect of plutonium lung burdens in both species. Rats were less sensitive to both kinds of radiation, whether administered alone or in combination. 71 refs., 105 figs., 48 tabs.
Date: August 1, 1988
Creator: Filipy, R.E.; Decker, J.R.; Lai, Y.L.; Lauhala, K.E.; Buschbom, R.L.; Hiastala, M.P. et al.
Partner: UNT Libraries Government Documents Department

Health effects models for nuclear power plant accident consequence analysis: Modifications of models resulting from recent reports on health effects of ionizing radiation

Description: The Nuclear Regulatory Commission has sponsored several studies to identify and quantify the potential health effects of accidental releases of radionuclides from nuclear power plants. The most recent health effects models resulting from these efforts were published in two reports, NUREG/CR-4214, Rev. 1, Part 1 (1990) and Part 2 (1989). Several major health effects reports have been published recently that may impact the health effects models presented in these reports. This addendum to the Part 2 (1989) report, provides a review of the 1986 and 1988 reports by the United Nations Scientific Committee on the Effects of Atomic Radiation, the National Academy of Sciences/National Research Council BEAR 5 Committee report and Publication 60 of the International Commission on Radiological Protection as they relate to this report. The three main sections of this addendum discuss early occurring and continuing effects, late somatic effects, and genetic effects. The major changes to the NUREG/CR-4214 health effects models recommended in this addendum are for late somatic effects. These changes reflect recent changes in cancer risk factors that have come from longer followup and revised dosimetry in major studies like that on the Japanese A-bomb survivors. The results presented in this addendum should be used with the basic NUREG/CR-4214 reports listed above to obtain the most recent views on the potential health effects of radionuclides released accidentally from nuclear power plants. 48 refs., 4 figs., 24 tabs.
Date: August 1, 1991
Creator: Abrahamson, S. (Wisconsin Univ., Madison, WI (United States)); Bender, M.A. (Brookhaven National Lab., Upton, NY (United States)); Boecker, B.B.; Scott, B.R. (Lovelace Biomedical and Environmental Research Inst., Albuquerque, NM (United States). Inhalation Toxicology Research Inst.) & Gilbert, E.S. (Pacific Northwest Lab., Richland, WA (United States))
Partner: UNT Libraries Government Documents Department