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Biomedical subjects

M E Wrenn

Publications and source records attributed to M E Wrenn.

At least 19 recordsLinked to original sources
PubMed1994

Thermoluminescence measurements of gamma-ray doses attributable to fallout from the Nevada test site using building bricks as natural dosimeters.

During the 1950's, the U.S. Government conducted an intensive atmospheric nuclear testing program in Nevada. Fallout from these atmospheric tests was measured throughout the U.S. with some of the heaviest concentrations to populated areas falling east of the test site in Washington County, UT. External exposures from 6.5 x 10(-4) C kg-1 to 26 x 10(-4) C kg-1 (2.5-5.0 R) were reported for this region. This study provides an independent measurement of fallout radiation doses to selected communities in Utah using a thermoluminescence technique originally developed for the dating of ancient pottery. The application of the predose thermoluminescence technique to fallout dosimetry is described. A mean dose of 38 +/- 15 mGy (4.4 +/- 1.7 R), attributed to fallout radiation, was measured in quartz grains extracted from the outer centimeter of bricks removed from six communities in Washington and Kane Counties in Utah.

Construction Materials↗
PubMed1990

Individual external exposures from Nevada Test Site fallout for Utah leukemia cases and controls.

External gamma-ray exposures from fallout originating at the Nevada Test Site (NTS) have been assigned to 6,507 individual subjects (1,177 leukemia cases and 5,330 control subjects) who died as Utah residents between 1952 and 1981. Leukemia cases were identified, confirmed, and classified by cell type from the Utah Cancer Registry, Utah State vital records, and medical records. Residential histories were obtained from the Deceased Membership File (DMF) of the Church of Jesus Christ of Latter-day Saints (LDS), supplemented by information from the LDS Church Census Records that were taken in 1950, 1955, and 1960-62. Control subjects were selected randomly within age strata from the DMF and were frequency-matched to the cases by age at death and for sex. Individual radiation exposures were assigned as a function of residence location and time interval for each residence during the fallout period (1951-1958) using geographic exposure data taken from the literature. Temporal distribution of exposure for subjects who resided in more than one locality or who were born or died during the fallout period was determined from data of other investigators. Calculated gamma-ray exposures for each place of residence were summed for each subject to yield the exposure to fallout from the NTS.

Case-Control Studies↗
PubMed1989

Utilization of femoral head for estimating the skeletal burden of U and Pu in humans.

Uranium and Pu were determined in vertebrae, ribs and femoral head samples obtained from the same population. Vertebrae and rib samples were obtained at autopsy and femoral head samples were obtained from persons undergoing hip surgery. The results indicate that there was no statistically (p less than or equal to 0.05) significant difference between the mean concentration of 239,240Pu in vertebrae and ribs. Also, there was no significant difference between the mean concentration of 239,240 Pu in ribs and femoral head. Also, statistical tests were performed to see whether the mean concentrations of 238U and 234U in three different bones differ from each other. The results suggest that there was no statistically significant difference between vertebrae and ribs, vertebrae and head of the femur nor between ribs and femoral head. These results indicate that femoral head may be an appropriate substitute for vertebrae or ribs, the most commonly used bone for inferring the skeletal burden of U and Pu in human. Femoral head samples can be obtained from living persons undergoing hip surgery, while vertebrae and ribs are obtained only at autopsy.

Body Burden↗
PubMed1989

Is the beagle dog an appropriate experimental animal for extrapolating data to humans on organ distribution patterns of U, Th, and Pu?

Concentrations and organ distribution patterns of alpha-emitting isotopes of U (238U and 234U), Th (232Th, 230Th, and 228Th), and Pu (239,240Pu) were determined for beagle dogs of our colony. The dogs were exposed to environmental levels of U and Th isotopes through ingestion (food and water) and inhalation to stimulate environmental exposures of the general human population. The organ distribution patterns of these radionuclides in beagles are compared to patterns in humans to determine if it is appropriate to extrapolate organ content data from beagles to humans. The results indicated that approximately 80% of the U and Th accumulated in bone in both species. The organ content percentages of these radionuclides in soft tissues such as liver, kidney, etc. of both species were comparable. The human lung contained higher percentages of U and Th than the beagle lung, perhaps because the longer life span of humans resulted in a longer exposure time. If the U and Th content of dog lung is normalized to an exposure time of 58 y and 63 y, median ages of the U and Th study populations, respectively, the lung content for both species is comparable. The organ content of 239,240Pu in humans and beagles differed slightly. In the beagle, the liver contained more than 60%, and the skeleton contained less than 40% of the Pu body content. In humans, the liver contained approximately 37%, and the skeleton contained approximately 58% of the body content. This difference may have been due to differences in the mode of intake of Pu in each species or to differences in the chemical form of Pu. In general, the results suggest that the beagle may be an appropriate experimental animal from which to extrapolate data to humans with reference to the percentage of U, Th, and Pu found in the organs.

Administration, Inhalation↗
PubMed1988

Determinations of actinides in biological and environmental samples.

This paper summarises the radiochemical procedures utilised in our laboratory to determine U, Th and Pu in different sample matrices, including soft tissues, bones, urine, faeces, soil, water, air-filters, lichen, and building materials such as granite, phosphate and concrete. Sample preparation, depending upon the matrix of the sample, includes either dry ashing and/or wet ashing with a mixture of HNO3 and H2SO4 or HNO3 alone with occasional additions of a few drops of HNO3 and H2O2. Uranium, Th and Pu are either co-precipitated with Fe carrier as hydroxides or with Ca as oxalates. Solvent extractions are performed from 2M HNO3, 4M HNO3 or 10M HCl depending upon the actinide or combination of actinides to be determined. The techniques have been very successful for most samples, with radiochemical recoveries exceeding 70%. However, radiochemical recoveries of Th from soil samples have been very poor (10-30%). Attempts are being made to improve these recoveries.

Actinoid Series Elements↗
PubMed1988

The beagle: an appropriate experimental animal for extrapolating the organ distribution pattern of Th in humans.

The concentrations and the organ distribution patterns of 228Th, 230Th and 232Th in two 9-y-old dogs of our beagle colony were determined. The dogs were exposed only to background environmental levels of Th isotopes through ingestion (food and water) and inhalation as are humans. The organ distribution patterns of the isotopes in the beagles were compared to the organ distribution patterns in humans to determine if it is appropriate to extrapolate the beagle organ burden data to humans. Among soft tissues, only the lungs, lymph nodes, kidney and liver, and skeleton contained measurable amounts of Th isotopes. The organ distribution pattern of Th isotopes in humans and dog are similar, the majority of Th being in the skeleton of both species. The average skeletal concentrations of 228Th in dogs were 30 to 40 times higher than the average skeletal concentrations of the parent 232Th, whereas the concentration of 228Th in human skeleton was only four to five times higher than 232Th. This suggests that dogs have a higher intake of 228Ra through food than humans. There is a similar trend in the accumulations of 232Th, 230Th and 228Th in the lungs of dog and humans. The percentages of 232Th, 230Th and 228Th in human lungs are 26, 9.7 and 4.8, respectively, compared to 4.2, 2.6 and 0.48, respectively, in dog lungs. The larger percentages of Th isotopes in human lungs may be due simply to the longer life span of humans. If the burdens of Th isotopes in human lungs are normalized to an exposure time of 9.2 y (mean age of dogs at the time of sacrifice), the percent burden of 232Th, 230Th and 228Th in human lungs are estimated to be 3.6, 1.3 and 0.66, respectively. These results suggest that the beagle may be an appropriate experimental animal for extrapolating the organ distribution pattern of Th in humans.

Administration, Inhalation↗
PubMed1987

Cancer incidence and lifespan vs. alpha-particle dose in beagles.

Young adult beagles were injected with graded activities of 239Pu, 241Am, 228Th, 228Ra or 226Ra and observed throughout their lifespans. The vast majority of the dose was from alpha particles. The lifetime incidence of bone sarcoma increased with average skeletal dose, more or less linearly up to high incidence for 239Pu, 241Am, 228Th and 226Ra, but sigmoid fashion for 228Ra. Based on average skeletal dose, the toxicity of the emitters relative to 226Ra = 1.0 was 239Pu = 16.6 +/- 4.5, 241Am = 5.4 +/- 1.6, 228Th = 8.5 +/- 2.3 and 228Ra = 2.0 +/- 0.5. At the lowest doses, the average lifespans were 97% +/- 3% of that in the controls. If beneficial effects occurred, they may have been overwhelmed by the destructiveness of the densely ionizing alpha particles. A cell nucleus 5 micron in diameter receives a mean dose of about 1 Gy (100 rad) when traversed by a single alpha particle. We found no evidence that alpha-particle doses suppressed cancer or lengthened lifespan in beagles.

Alpha Particles↗
PubMed1987

Macro-distribution of naturally occurring alpha-emitting isotopes of U in the human skeleton.

Argonne National Laboratory (ANL) exhumed the remains of two individuals who had received Pu by intravenous injection, performed Pu analysis on these remains, and then sent portions of individual bones to our laboratory. We analyzed these bone samples to determine the macro-distribution of naturally occurring alpha-emitting isotopes of U (234U and 238U). We found that the sacrum contained the highest concentrations of 234U and 238U (4.9 +/- 0.3 mBq g-1 of bone ash). Different ribs contained varying concentrations of 234U and 238U ranging from 0.26 +/- 0.2 to 1.6 +/- 0.4 mBq g-1 of bone ash for 234U, and from 0.16 +/- 0.1 to 1.5 +/- 0.4 mBq g-1 ash for 238U. The upper and lower values differ significantly at p = 0.001. Concentrations of 234U and 238U in vertebral bodies were lower than in left ribs numbers 1 and 2, but were similar to the concentrations in the other left ribs. The concentration of 235U was below the detection limit in each bone (lower limit of detection (LLD) = 4 X 10(-4) Bq per sample). The results indicate that the distribution of U isotopes is not uniform throughout the skeleton. Thus, the skeletal burden of U estimated from determinations in an individual bone sample may be quite erroneous until the fraction of total skeletal U contained in each bone is known.

Adolescent↗
PubMed1987

Concentrations of alpha-emitting isotopes of U and Th in uranium miners' and millers' tissues.

The concentrations of alpha-emitting isotopes of U (234U, 235U, and 238U) and Th (228Th, 230Th, and 232Th) were determined in soft tissues and bones of three deceased U miners and two deceased U millers. The soft tissues generally included lung, liver, kidney, spleen, gonad and heart. The concentrations of U isotopes in the miners' lungs varied up to a factor of 18, suggesting that the accumulations of U in lungs at the time of death varied drastically. The concentrations of 230Th in the miners' lungs were similar to the concentrations of 234U and 238U. The concentrations of U isotopes and 230Th in millers' lungs also differed by a factor of almost 10. The most noticeable difference between the concentrations of U isotopes (238U and 234U) and 230Th was in the skeleton of U miners and millers. The 230Th/234U concentration ratios were as high as 94 in bones of miners and as high as 23 in millers. These results suggest that the fraction of Th transferred from blood to bones is much higher than the fraction of U transferred, and that the residence time of Th in skeleton is much higher than the residence time of U as suggested in ICRP Publication 30.

Alpha Particles↗
PubMed1986

Concentrations of 210Pb and its states of equilibrium with 238U, 234U and 230Th in U miners' lungs.

The concentrations of 210Pb and its states of equilibrium with 238U, 234U and 230Th in U miners' lungs obtained at autopsy are reported. The concentration of 210Pb ranged from 0.63 to 123 Bq/kg wet weight with an average of 32.7 Bq/kg. The 210Pb concentrations were almost seven times higher than the concentrations of 238U, 234U and 230Th. The radiation dose rates to U miners' lungs from 210Po alone ranged from 0.017 to 3.30 mGy/y with an average of 0.88 mGy/y. The dose rates from 238U, 234U and 230Th combined ranged from 6.8 X 10(-3) to 7.2 X 10(-1) mGy/y with an average of 2.9 X 10(-1) mGy/y. The dose rates from all alpha-emitting members of the 238U series, excluding 210Po, varied from 1.1 X 10(-2) to 2.2 mGy/y with an average of 7.5 X 10(-1) mGy/y.

Aged↗
PubMed1985

Reducing radon exhalation from covered tailings: optimization or cost effectiveness?

Reduction of radon exhalation from uranium tailings as a function of the number of radon diffusion lengths in cover materials is discussed, based on dimensionless mathematical functions. Cost effectiveness is examined to determine the least expensive cover with a preselected number of radon diffusion lengths (i.e., a preselected level of radiation protection), and to find the maximum attainable reduction in radon flux with a predetermined cost (i.e., a fixed amount of money). Cost effectiveness rather than optimization through cost benefit analysis can be used advantageously in these cases.

Cost-Benefit Analysis↗
PubMed1985

Metabolism of ingested U and Ra.

The literature on metabolism of U and Ra for man relevant to deriving drinking water standards has been reviewed and summarized. Radium is well understood, but significant gaps remain in our knowledge about U metabolism. Limits should be based on an equilibrium model where a constant relationship between intake and organ burden is established, using the best and most likely metabolic parameters. For the skeleton we conclude that the best estimate of skeletal burden expressed in days equivalent intake are 25 days for 226Ra, 10 days for 228Ra, and 0.3 days for 224Ra. For long-lived isotopes of U, we chose 11 days, with a range between 1 and 35 days. The committee believes that intake of natural U in water should be limited by considerations of toxicity to the kidney, and we believe that the metabolic model of Spoor and Hursh with a modified gastrointestinal (GI) absorption (1.4%) should be used to infer kidney content. Our review and analysis of the world literature leads us to believe the average human GI absorption of U is most likely 1-2% and is probably reasonably independent of age or the mass of U ingested. Using a safety factor of 50-150, the committee recommends a limit of U in water of 100 micrograms/l in order to limit toxic effects in the kidney. One hundred micrograms/liter is equivalent to 67 pCi/l of long-lived alpha-emitting natural U isotopes. Further research into the distribution of U in the human body is desirable, especially at natural levels in kidney and skeleton, the time-dependent pharmacokinetics of U in animals, the GI absorption of U in man from water and food, toxicological and U distribution studies in animals under conditions of chronic oral U intake, and metabolic model error propagation.

Animals↗