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PubMed1996

Estimating internal dose due to ingestion of radionuclides from Nevada Test Site fallout.

The U.S. Department of Energy initiated the Radiation Exposure Review Project to provide a critical reexamination of radiation doses to people resulting from testing nuclear devices at the Nevada Test Site. One part of this effort focused on the dose resulting from the ingestion of contaminated food. The PATHWAY radionuclide transport model was developed to provide estimates of food concentrations for 20 radionuclides for each of 86 test events and 15 agricultural scenarios. These results were then used as input to the Human Ingestion model to provide dose estimates for individuals and populations in 9 western states. The model considered the life-style and age of the people, and accounted for the transport of milk between locations. Estimates of uncertainty were provided for all doses using Monte Carlo simulation techniques. Propagation of uncertainty between the PATHWAY model and the Human Ingestion model required the development of special strategies to ensure that the inherent correlations between concentrations of the radionuclides in foods were handled properly. In addition, the size of the input data base (60 megabytes), the number of cases to consider (over 30,000), and the number of Monte Carlo simulations (over 6 million) required the development of efficient and reliable methods of data access and storage while running simulations concurrently on up to 14 UNIX workstations. The problems encountered in this effort are likely to be typical of any dose reconstruction involving geographically heterogeneous environmental conditions. This paper documents the methods used to disaggregate the system to achieve computation efficiency, the methods used to propagate uncertainty through the model system, and the techniques used to manage data in a distributed computing environment. The radionuclide- and age-specific dose factors used in the analysis are also provided.

Environmental Exposure↗
PubMed2006

Factors for satisfaction among providers of ancillary health services in a community-based cancer prevention program: a pilot study in Nevada.

Providers of ancillary health services are essential members of any health care delivery system. They supply laboratory, radiology, and other diagnostic modalities necessary for quality medical care. Assessment of the providers' factors for satisfaction in participating in cancer prevention programs can contribute to better services and can serve as a model for other community-based health programs. We conducted a pilot survey of providers of ancillary services in the Nevada Women's Health Connection, a community breast and cervical cancer prevention program. Of the 93 participating providers, a total of 44 providers completed the survey. We subjected the survey data to factor analysis using iterative principal axis factoring with Varimax rotation. Three components of satisfaction were identified, comprising satisfaction with the (1) reimbursement process, (2) positive perception of the program, and (3) familiarity with program's requirements. All three components accounted for 72.08% of the total variance before the rotation. Amount of financial gain was not a significant factor for satisfaction among participating providers. Providers of ancillary health services were satisfied in their participation in this community-based cancer prevention program. There were three components of satisfaction identified. Further attention should be given on these issues as they have implications for quality improvement in health services for community-based programs dealing with low income and uninsured patients.

Ancillary Services, Hospital↗
PubMed2000

The assessment of radiation exposures in Native American communities from nuclear weapons testing in Nevada.

Native Americans residing in a broad region downwind from the Nevada Test Site during the 1950s and 1960s received significant radiation exposures from nuclear weapons testing. Because of differences in diet, activities, and housing, their radiation exposures are only very imperfectly represented in the Department of Energy dose reconstructions. There are important missing pathways, including exposures to radioactive iodine from eating small game. The dose reconstruction model assumptions about cattle feeding practices across a year are unlikely to apply to the native communities as are other model assumptions about diet. Thus exposures from drinking milk and eating vegetables have not yet been properly estimated for these communities. Through consultations with members of the affected communities, these deficiencies could be corrected and the dose reconstruction extended to Native Americans. An illustration of the feasibility of extending the dose reconstruction is provided by a sample calculation to estimate radiation exposures to the thyroid from eating radio-iodine-contaminated rabbit thyroids after the Sedan test. The illustration is continued with a discussion of how the calculation results may be used to make estimates for other tests and other locations.

Adolescent↗
PubMed2002

Semiparametric regression modeling with mixtures of Berkson and classical error, with application to fallout from the Nevada test site.

We construct Bayesian methods for semiparametric modeling of a monotonic regression function when the predictors are measured with classical error. Berkson error, or a mixture of the two. Such methods require a distribution for the unobserved (latent) predictor, a distribution we also model semiparametrically. Such combinations of semiparametric methods for the dose response as well as the latent variable distribution have not been considered in the measurement error literature for any form of measurement error. In addition, our methods represent a new approach to those problems where the measurement error combines Berkson and classical components. While the methods are general, we develop them around a specific application, namely, the study of thyroid disease in relation to radiation fallout from the Nevada test site. We use this data to illustrate our methods, which suggest a point estimate (posterior mean) of relative risk at high doses nearly double that of previous analyses but that also suggest much greater uncertainty in the relative risk.

Bayes Theorem↗
PubMed2005

Genetic monitoring of wild and repatriated populations of endangered razorback sucker (Xyrauchen texanus, Catostomidae, Teleostei) in Lake Mohave, Arizona-Nevada.

The Native Fishes Work Group, formed in 1991, developed and implemented a protocol to enhance the dwindling razorback sucker population in Lake Mohave, Arizona-Nevada. This large, genetically diverse population is severely reduced in size as a result of recruitment failure associated with predation on larvae. To circumvent this problem, wild larvae are captured, reared in protective custody until they are large enough to escape predation, and then released back into the lake. We present results of a monitoring program designed to assess the effectiveness of the sampling design in transmitting the high genetic diversity found in wild adults. Variation in a fragment from the mitochondrial DNA gene cytochrome b was examined by analysis of single-stranded polymorphisms and direct sequencing. Samples were characterized from three life history stages. Characterization of wild adults verified previous results that identified considerable diversity and provided baseline data. Samples of larvae from several temporal collections from throughout the spawning season and four geographical areas were characterized for 7 years (1997-2003) to assess the transmission of genetic variation from wild adults to larvae. Several analyses identified significant differences among temporal collections, resulting from sampling errors associated with finite number of females spawning at a given time and place. Comparisons among areas and years failed to identify significant variation, indicating that pooled collections for each year possess the same levels and patterns of genetic variation. Examination of repatriates representing 11 years (1992-2002) also failed to identify significant differences among cohorts; however, some sample sizes were small and the amova may lack sufficient power to detect differences. Contrasts of wild adults, larvae, and repatriates identified statistically significant differences among collections within these three groups; however, levels of variation are small and not biologically meaningful. More importantly, this analysis failed to detect significant differences among adults, larvae, and repatriates indicating that the program has been achieving its goal of transmitting variation from adults through the larvae and into the repatriate population. The reproductive capability of repatriates has not been examined, so it is unknown if the program will maintain genetic variation found in the original adult population. This will be most easily achieved by periodic monitoring of genetic variation in larval samples. If levels of variation become reduced in repatriates, levels and patterns of diversity in larvae are also expected to become reduced, and deviations in estimates of genetic diversity may become larger and more frequent. If this is the case, intervention may be necessary to ensure that certain individuals are not over-represented in the repatriate population.

Animals↗
PubMedDate not supplied

Effect of heterogeneity on radionuclide retardation in the alluvial aquifer near Yucca Mountain, Nevada.

The U.S. Department of Energy is currently studying Yucca Mountain, Nevada, as a potential site for a geological high-level waste repository. In the current conceptual models of radionuclide transport at Yucca Mountain, part of the transport path to pumping locations would be through an alluvial aquifer. Interactions with minerals in the alluvium are expected to retard the downstream migration of radionuclides, thereby delaying arrival times and reducing ground water concentrations. We evaluate the effectiveness of the alluvial aquifer as a transport barrier using the stochastic Lagrangian framework. A transport model is developed to account for physical and chemical heterogeneities and rate-limited mass transfer between mobile and immobile zones. The latter process is caused by small-scale heterogeneity and is thought to control the macroscopic-scale retardation in some field experiments. A geostatistical model for the spatially varying sorption parameters is developed from a site-specific database created from hydrochemical measurements and a calibrated modeling approach (Turner and Pabalan 1999). Transport of neptunium is considered as an example. The results are sensitive to the rate of transfer between mobile and immobile zones, and to spatial variability in the hydraulic conductivity. Chemical heterogeneity has only a small effect, as does correlation between hydraulic conductivity and the neptunium distribution coefficient. These results illustrate how general sensitivities can be explored with modest effort within the Lagrangian framework. Such studies complement and guide the application of more detailed numerical simulations.

Actinoid Series Elements↗
PubMedDate not supplied

Using temperature to test models of flow near Yucca Mountain, Nevada.

Ground water temperatures in the fractured volcanic aquifer near Yucca Mountain, Nevada, have previously been shown to have significant spatial variability with regions of elevated temperatures coinciding roughly with near-vertical north-south trending faults. Using insights gained from one-dimensional models, previous investigators have suggested upwelling along faults from an underlying aquifer as a likely explanation for this ground water temperature pattern. Using a three-dimensional coupled flow and heat-transport model, we show that the thermal high coinciding with the Paintbrush fault zone can be explained without significant upwelling from the underlying aquifer. Instead, the thermal anomaly is consistent with thermal conduction enhanced slightly by vertical ground water movement within the volcanic aquifer sequence. If more than approximately 400 m3/day of water enters the volcanic aquifer from below along a 10 km fault zone, the calculated temperatures at the water table are significantly greater than the measured temperatures. These results illustrate the potential limitations in using one-dimensional models to interpret ground water temperature data, and underscore the value in combining temperature data with fully coupled three-dimensional simulations.

Environmental Monitoring↗
PubMed1962

Nevada test fallout and radioiodine in milk.

The iodine-131 dosage to infant thyroids as a result of Nevada testing is evaluated. The case of heavy fallout in the Troy, N.Y., area on 26 April 1953 is cited. The possibility is discussed that a thyroid cancer survey would provide a critical test of linear response versus threshold theory for radiation injury to tissue.

Animals↗
PubMed1984

Childhood leukemia and fallout from the Nevada nuclear tests.

Cancer mortality data from the National Center for Health Statistics, covering the period 1950 through 1978, were used to test a reported association between childhood leukemia and exposure to radioactive fallout from nuclear weapons tests in Nevada between 1951 and 1958. No pattern of temporal and geographic variation in risk supportive of the reported association was found. Comparison of these results with those presented in support of an association of risk with fallout suggests that the purported association merely reflects an anomalously low leukemia rate in southern Utah during the period 1944 to 1949.

Adolescent↗
PubMed1983

Radiation exposures in Utah from Nevada Nuclear Tests.

The exposure of the population of Utah to external gamma-radiation from the fallout from nuclear weapons tests carried out between 1951 and 1958 at the Nevada Test Site has been reconstructed from recent measurements of residual cesium-137 and plutonium in soil. Although the highest exposures were found in the extreme southwest part of Utah, as expected, the residents of the populous northern valleys around Provo, Salt Lake City, and Ogden received a higher mean dose and a significantly greater population dose (person-rads) than did the residents of most counties closer to the test site. However, population doses from external exposure throughout Utah were far too low to result in any statistically observable health effects.

Environmental Exposure↗
PubMed1991

In situ bacterial selenate reduction in the agricultural drainage systems of western Nevada.

Dissimilatory in situ selenate reduction to elemental selenium in sediments from irrigated agricultural drainage regions of western Nevada was measured at ambient Se oxyanion concentrations. Selenate reduction was rapid, with turnover rate constants ranging from 0.04 to 1.8 h-1 at total Se concentrations in pore water of 13 to 455 nM. Estimates of removal rates of selenium oxyanions were 14.38, and 155 mumol m-2 day-1 for South Lead Lake, Massie Slough, and Hunter Drain, respectively.

Agriculture↗
PubMedDate not supplied

Mountaineering accidents in the Sierra Nevada.

Two hundred and fifteen mountaineering accidents occurred in the Sierra Nevada over a 5-year period in climbers on Class V routes. Patients were evaluated for: climbing preparation and training, first aid experience, altitude acclimatization, age, anatomical site of injuries, and cause of the injury. Consideration as to evacuation procedure was also given. The effect of high altitude exposure impairs judgment and muscular coordination and implies poor acclimatization. Acute mountain sickness and hypothermia were documented in 104 patients, the majority of whom sustained injuries resulting from judgmental errors. Ninety-four injuries involved the ankle and lower tibia, an incidence similar to that seen in alpine skiing a decade ago. There were 17 deaths resulting most frequently from head injuries. Few climbers had formal training in basic mountain medicine which was reflected in the poor assessment and management of injuries, with an unnecessary reliance upon others for evacuation. Morbidity and mortality may be lessened by proper climbing preparation--instruction in mountaineering techniques as well as basic mountain medicine--and by prevention of acute mountain sickness and cold injury.

Adolescent↗
PubMed2004

Probability estimates for the unique childhood leukemia cluster in Fallon, Nevada, and risks near other U.S. Military aviation facilities.

A unique cluster of childhood leukemia has recently occurred around the city of Fallon in Churchill County, Nevada. From 1999 to 2001, 11 cases were diagnosed in this county of 23,982 people. Exposures related to a nearby naval air station such as jet fuel or an infectious agent carried by naval aviators have been hypothesized as potential causes. The possibility that the cluster could be attributed to chance was also considered. We used data from the Surveillance, Epidemiology, and End Results Program (SEER) to examine the likelihood that chance could explain this cluster. We also used SEER and California Cancer Registry data to evaluate rates of childhood leukemia in other U.S. counties with military aviation facilities. The age-standardized rate ratio (RR) in Churchill County was 12.0 [95% confidence interval (CI), 6.0-21.4; p = 4.3 times symbol 10(-9)]. A cluster of this magnitude would be expected to occur in the United States by chance about once every 22,000 years. The age-standardized RR for the five cases diagnosed after the cluster was first reported was 11.2 (95% CI, 3.6-26.3). In contrast, the incidence rate was not increased in all other U.S. counties with military aviation bases (RR = 1.04; 95% CI, 0.97-1.12) or in the subset of rural counties with military aviation bases (RR = 0.72; 95% CI, 0.48-1.08). These findings suggest that the Churchill County cluster was unlikely due to chance, but no general increase in childhood leukemia was found in other U.S. counties with military aviation bases.

Adolescent↗
PubMed1994

High levels of mercury contamination in multiple media of the Carson River drainage basin of Nevada: implications for risk assessment.

Approximately 5.5 x 109 g (4.0 x 105) of mercury was discharged into the Carson River Drainage Basin of west-central Nevada during processing of the gold- and silver-rich Comstock ore in the late 1800s. For the past 13 decades, mercury has been redistributed throughout 500 km2 of the basin, and concentrations are some of the highest reported values in North America. This article documents the concentrations of mercury in the air, water, and substrate at both contaminated and noncontaminated sites within the basin and discusses the implications for risk assessment. At contaminated areas, the range of mercury concentrations are as follows: mill tailings, 3-1610 micrograms/g; unfiltered reservoir water, 53-591 ng/l; atmospheric vapor, 2-294 ng/m3. These values are three to five orders of magnitude greater than natural background. In all media at contaminated sites, concentrations are spatially variable, and air and water mercury concentrations vary temporally. The study are in situated in a natural mercuriferous belt, and regional background mercury concentrations in all environmental media are higher than values typically cited for natural background. As a mercury-contaminated site in North America, the Carson River Drainage Basin is unusual for a number of reasons, including its location in a natural mercuriferous belt, high and sustained levels of anthropogenic mercury inputs, long exposure time, aridity of the climate, and the riparian setting in an arid landscape, where biological activity is concentrated in the same areas that contain high levels of mercury in multiple media.

Air Pollutants↗
PubMed2006

Coliform bacteria in Sierra Nevada wilderness lakes and streams: what is the impact of backpackers, pack animals, and cattle?

OBJECTIVE: The presence of coliform bacteria indicates a watershed risk for harboring microbes capable of causing human disease. We hypothesized that water from watersheds that have different human- or animal-use patterns would have differing risks for the presence of coliform bacteria. METHODS; Water was collected in wilderness areas of the Sierra Nevada range in California. A total of 60 sites from lakes or streams were selected to statistically differentiate the risk categories: 1) high use by backpackers, 2) high use by pack animals, 3) cattle- and sheep-grazing tracts, and 4) natural areas rarely visited by humans or domestic animals. Water was collected in sterile test tubes and Millipore coliform samplers during the summer of 2004. Water was analyzed at the university microbiology lab, where bacteria were harvested and then subjected to analysis by standardized techniques. Confirmation was performed with a Phoenix 100 bacteria analyzer. Statistical analysis to compare site categories was performed with Fisher exact test. RESULTS: Only 1 of 15 backpacker sites yielded coliforms. In contrast, 12 of 15 sites with heavy pack-animal traffic yielded coliforms. All 15 sites below the cattle-grazing areas grew coliforms. Differences between backpacker and cattle or pack-animal areas were significant (P < or = .05). Only 1 of the 15 wild sites rarely visited by humans grew coliforms. All coliforms were identified as Escherichia coli. All samples grew normal aquatic bacteria of the genera Pseudomonas, Ralstonia, and Serratia and nonpathogenic strains of Yersinia. No correlation could be made with temperature or elevation. Sites below cattle-grazing tracts and pack-animal usage areas tended to have more total bacteria. CONCLUSIONS: Alpine wilderness water below cattle-grazing tracts or areas used by pack animals are at risk for containing coliform organisms. Areas exclusively used by backpackers were nearly free of coliforms.

Animals↗
PubMed2006

Review of methods of dose estimation for epidemiological studies of the radiological impact of nevada test site and global fallout.

Methods to assess radiation doses from nuclear weapons test fallout have been used to estimate doses to populations and individuals in a number of studies. However, only a few epidemiology studies have relied on fallout dose estimates. Though the methods for assessing doses from local and regional compared to global fallout are similar, there are significant differences in predicted doses and contributing radionuclides depending on the source of the fallout, e.g. whether the nuclear debris originated in Nevada at the U.S. nuclear test site or whether it originated at other locations worldwide. The sparse historical measurement data available are generally sufficient to estimate external exposure doses reasonably well. However, reconstruction of doses to body organs from ingestion and inhalation of radionuclides is significantly more complex and is almost always more uncertain than are external dose estimates. Internal dose estimates are generally based on estimates of the ground deposition per unit area of specific radionuclides and subsequent transport of radionuclides through the food chain. A number of technical challenges to correctly modeling deposition of fallout under wet and dry atmospheric conditions still remain, particularly at close-in locations where sizes of deposited particles vary significantly over modest changes in distance. This paper summarizes the various methods of dose estimation from weapons test fallout and the most important dose assessment and epidemiology studies that have relied on those methods.

Body Burden↗
PubMed1995

Condom use among female commercial sex workers in Nevada's legal brothels.

OBJECTIVES: The purpose of this study was to evaluate condom use and the incidence of breakage and slippage during vaginal intercourse among female prostitutes in legal Nevada brothels, where use of condoms is required by law. METHODS: Forty-one licensed prostitutes in three brothels were enrolled in a prospective trial in August 1993. Used condoms were collected to verify reported breaks visually. Retrospective breakage and slippage rates were obtained in a standardized interview. RESULTS: Condoms were used for every act of vaginal intercourse with a brothel client during the study period, as well as in the previous year. In the prospective study phase, condoms were used in 353 acts of vaginal intercourse with clients. No condoms broke, and none fell off the penis during intercourse. Only twice (0.6%) did condoms completely fall off during withdrawal. Twelve times (3.4%) during intercourse and 15 times (4.3%) during withdrawal, condoms slipped down the penis but did not fall off. CONCLUSIONS: These findings, among the lowest breakage and slippage rates published, suggest that regular condom use may lead to condom mastery and the development of techniques to reduce the likelihood of breakage and slippage.

Adult↗
PubMed1998

Facilitating condom use with clients during commercial sex in Nevada's legal brothels.

OBJECTIVES: This study examined condom use in legal Nevada brothels. METHODS: Forty female prostitutes in two brothels were interviewed about client resistance to condoms and techniques for facilitating condom use. RESULTS: Of 3290 clients in the previous month, 2.7% (95% confidence interval [CI] = 2.2%,3.4%) were reluctant to use condoms. Of these individuals, 72% ultimately used condoms, while 12% chose nonpenetrative sex without condoms. The remaining 16% left the brothels without services. Condom use rates were markedly lower with nonpaying sex partners (lowers) than with clients. CONCLUSIONS: Brothel prostitutes may be at greater risk for acquiring HIV and other sexually transmitted diseases from lovers than from clients.

Adult↗