Showing papers in "Health Physics in 1997"

Radiation absorbed dose to the embryo/fetus from radiopharmaceuticals

Abstract: Radiation protection practice requires the knowledge of estimated absorbed radiation doses to aid in the understanding of the potential detriment of various exposures. In nuclear medicine, the radiation doses to the internal organs of the subject are commonly calculated using the MIRD methods and equations. The absorbed dose to the embryo or fetus has long been an area of concern. The recent release of the pregnant female phantom series, and its incorporation into the MIRDOSE 3 computer software, has made possible the estimation of absorbed doses from radionuclides in the body to the fetus in early pregnancy and at 3, 6, and 9 mo gestation. A survey of several major medical institutions was made to determine the radiopharmaceuticals which might be given, whether intentionally or not, to women of childbearing years. Biokinetic data for these radiopharmaceuticals were gathered from various documents and other resources, and the absorbed doses to the embryo and fetus at these different stages of gestation from radiations originating within the mother's organs were estimated. In addition, information about activity distributed within the placenta and fetus was included where quantitative data were available. These absorbed dose estimates can be used to evaluate the risk associated with the use of different radiopharmaceuticals so that a more informed evaluation of the risks and benefits of the different procedures may be made. Further research is needed into the mechanisms and quantitative aspects of the placental transfer of many radiopharmaceuticals.

Early dose assessment following severe radiation accidents

Abstract: Early treatment of victims of high level acute whole-body x-ray or gamma exposure has been shown to improve their likelihood of survival. However, in such cases, both the magnitude of the exposure and the dosimetry profile(s) of the victim(s) are often not known in detail for days to weeks. A simple dose-prediction algorithm based on lymphocyte kinetics as documented in prior radiation accidents is presented here. This algorithm provides an estimate of dose within the first 8 h following an acute whole-body exposure. Early lymphocyte depletion kinetics after a severe radiation accident follow a single exponential, L(t) = L(o)e(-k(D?t), where k(D) is a rate constant, dependent primarily on the average dose, D. Within the first 8 h post-accident, K(D) may be calculated utilizing serial lymphocyte counts. Data from the REAC/TS Radiation Accident Registry were used to develop a dose-prediction algorithm from 43 gamma exposure cases where both lymphocyte kinetics and dose reconstruction were felt to be reasonably reliable. The inverse relationship D(K) may be modeled by a simple two parameter curve of the form D = a/(1 + b/K) in the range 0 < or = D < or = 15 Gy, with fitting parameters (mean +/- SD): a = 13.6 +/- 1.7 Gy, and b = 1.0 +/- 0.20 d(-1). Dose estimated in this manner is intended to serve only as a first approximation to guide initial medical management.

Residential radon and lung cancer in Sweden: risk analysis accounting for random error in the exposure assessment

Abstract: A large epidemiologic study on residential radon exposure and lung cancer has been conducted in Sweden. An attempt is now made to quantify the impact of random error in the exposure assessment on the risk estimate for lung cancer in this study. The study included 1,360 lung cancer cases, diagnosed from 1980 to 1984, and 2,847 population controls. Radon measurements were performed in 8,992 dwellings occupied by the study subjects some time since 1947. Questionnaires provided information on smoking and other risk factors. Imprecision in the retrospective exposure assessment for radon was estimated from a Monte Carlo technique modeling Swedish conditions. Adjusted risk estimates were obtained from regression analyses based on expected values for true time-weighted average residential radon concentration (TWA), conditional on observed TWA. Without adjustment for random error in the TWA estimates, the linear excess relative risk coefficient was 0.10 per 100 Bq m(-3), but an excess relative risk of about 0.15 to 0.20 per 100 Bq m(-3) was suggested following adjustment. The potentially significant consequences of errors in the retrospective radon exposure assessment should be taken into consideration in the risk estimation as well as in comparisons of results of different studies and in future pooled analyses.

A statistical analysis of the internal organ weights of normal Japanese people.

Abstract: Correlation of weights of various organs with age, body weight, and/or body height was statistically analyzed using data on the Japanese physique collected by the Medico-Legal Society from Universities and Research Institutes in almost all areas of Japan. After exclusion of unsuitable individual data for statistical analysis, findings for 4,667 Japanese, aged 0-95 y, including 3,023 males and 1,644 females were used in the present study. Analyses of age-dependent changes in weights of the brain, heart, lung, kidney, spleen, pancreas, thymus, thyroid gland and adrenal gland and also of correlations between organ weights and body height, weight, or surface area were carried out. It was concluded that organ weights in the growing generation (under 19 y) generally increased with a coefficient expressed as (body height x body weight0.5). Because clear age-dependent changes were not observed in adults over 20 y, they were classified into 4 physical types, thin, standard, plump and obese, and the relations of organ weights with these physical types were assessed. Some organs were relatively heavier in fat groups and light in thin individuals, or vice versa.

Neutron sources in the Varian Clinac 2100C/2300C medical accelerator calculated by the EGS4 code.

Abstract: The photoneutron yields produced in different components of the medical accelerator heads evaluated in these studies (24-MV Clinac 2500 and a Clinac 2100C/2300C running in the 10-MV, 15-MV, 18-MV and 20-MV modes) were calculated by the EGS4 Monte Carlo code using a modified version of the Combinatorial Geometry of MORSE-CG. Actual component dimensions and materials (i.e., targets, collimators, flattening filters, jaws and shielding for specific accelerator heads) were used in the geometric simulations. Calculated relative neutron yields in different components of a 24-MV Clinac 2500 were compared with the published measured data, and were found to agree to within +/-30%. Total neutron yields produced in the Clinac 2100/2300, as a function of primary electron energy and field size, are presented. A simplified Clinac 2100/2300C geometry is presented to calculate neutron yields, which were compared with those calculated by using the fully-described geometry.

New agents for in vivo chelation of uranium(VI): efficacy and toxicity in mice of multidentate catecholate and hydroxypyridinonate ligands.

Abstract: Soluble uranyl ion [UO2(2+), U(VI)] is a kidney poison. Uranyl ion accumulates in bone, and the high specific activity uranium isotopes induce bone cancer. Although sought since the 1940's, no multidentate ligand was identified, until now, that efficiently and stably binds U(VI) at physiological pH, promotes its excretion, and reduces deposits in kidneys and bone. Ten multidentate ligands patterned after natural siderophores and composed of sulfocatechol [CAM(S)], carboxy-catechol [CAM(C)], or hydroxypyridinone [Me-3,2-HOPO] metal-binding units have been tested for in vivo chelation of U(VI). Ligands were injected intraperitoneally (i.p.) into mice 3 min after intravenous (i.v.) injection of 233U or (232+235)U as UO2Cl2 [ligand-to-metal molar ratio 75 to 92]. Regardless of backbone structure, denticity, or binding unit, all 10 ligands significantly reduced kidney U(VI) compared with controls or with mice given CaNa3-DTPA, and four CAM(S) or CAM(C) ligands also significantly reduced skeleton U(VI). Several ligands removed U(VI) from kidneys, when injected at 1 or 24 h. Injected at molar ratios > or = 300, 5-LIO(Me-3,2-HOPO) and TREN-(Me-3,2-HOPO) reduced kidney U(VI) to about 10% of control. Given orally to fasted mice at molar ratios > or = 300, those ligands significantly reduced kidney U(VI). In mice injected i.v. with 0.42 micromol kg(-1) of 235U and given 100 micromol kg(-1) of one of those Me-3,2-HOPO ligands i.p. daily for 10 d starting at 1 h after the U(VI)) loss of kidney U(VI) was greatly accelerated, and the kidneys of treated mice showed no microscopic evidence of renal injury. Crystals of uranyl chelates with linear tetradentate ligands containing bidentate Me-3,2-HOPO groups demonstrate a 1:1 structure. Considering low toxicity, effectiveness, and reasonable cost, the structurally simple linear tetradentate ligands based on the 5-LI backbone (diaminopentane) offer the most promising approach to a clinically acceptable therapeutic agent for U(VI). Work is in progress to identify the most suitable CAM or HOPO binding unit(s).

Fifty years of plutonium exposure to the Manhattan Project plutonium workers: an update.

Abstract: Twenty-six white male workers who did the original plutonium research and development work at Los Alamos have been examined periodically over the past 50 y to identify possible health effects from internal plutonium depositions. Their effective doses range from 0.1 to 7.2 Sv with a median value of 1.25 Sv. As of the end of 1994, 7 individuals have died compared with an expected 16 deaths based on mortality rates of U.S. white males in the general population. The standardized mortality ratio (SMR) is 0.43. When compared with 876 unexposed Los Alamos workers of the same period, the plutonium worker's mortality rate was also not elevated (SMR = 0.77). The 19 living persons have diseases and physical changes characteristic of a male population with a median age of 72 y (range = 69 to 86 y). Eight of the twenty-six workers have been diagnosed as having one or more cancers, which is within the expected range. The underlying cause of death in three of the seven deceased persons was from cancer, namely cancer of prostate, lung, and bone. Mortality from all cancers was not statistically elevated. The effective doses from plutonium to these individuals are compared with current radiation protection guidelines.

Multifactorial analysis of lung cancer dose-response relationships for workers at the Mayak nuclear enterprise.

Abstract: Dose-response relationships for alpha-radiation-induced lung cancers (adenocarcinoma, squamous carcinoma and small cell carcinoma) were developed by multifactorial analysis using data for Mayak nuclear enterprise workers chronically exposed by inhalation to 239Pu. The three most important lung cancer risk factors (smoking, plutonium incorporation, and external gamma irradiation), out of six factors previously identified, were used. Relative risks (odds ratios) were determined for 500 nuclear enterprise workers (162 cancer cases, 338 control) for different dose levels using a case-control study design and logistic regression. A threshold at about 3.7 kBq or 0.80 Gy was discovered for incorporated plutonium, which is satisfactorily described by linear-quadratic and quadratic models. Excess relative risk was 0.020 kBq(-2) and 0.97 Gy(-2). This quadratic function was mainly due to adenocarcinoma. A trend for decreasing risk was noted for the lowest levels of plutonium incorporation, near permissible level. No clear-cut dose-response relationship for lung cancer induction by chronic external gamma irradiation was obtained. Lung cancer induction by cigarette smoking had a linear dependence: smoking of one pack of papiroses (a type of Russian cigarette) per day for 5 y increases the lung cancer risk twofold. The effect was most clearly manifested for squamous-cell carcinoma.

Placental transfer of radiopharmaceuticals and dosimetry in pregnancy

Abstract: The calculation of radiation dose estimates to the fetus is often important in nuclear medicine. To obtain the best estimates of radiation dose to the fetus, the best biological and physical models should be employed. In this paper the most recent data available on the placental crossover of many radiopharmaceuticals are presented. This information was used with standard kinetic models describing the maternal distribution and retention and with the best available physical models to obtain fetal dose estimates for these radiopharmaceuticals at all stages of pregnancy (presented in a separate paper). The literature yielded information on placental crossover of 15 radiopharmaceuticals, from animal or human data. From these data, radiation dose estimates were developed in early pregnancy and at 3, 6, and 9 mo gestation for these radiopharmaceuticals, as well as for many others used in nuclear medicine (the latter considering only maternal organ contributions to fetal dose).

A brief history of people and events related to atomic weapons testing in the Marshall Islands.

Abstract: The events related to nuclear testing in the Marshall Islands began at the end of WWII when the U.S. began an initiative to determine the effect of nuclear weapons on naval vessels and on the performance of military personnel. The first tests took place in 1946 even though the area known as Micronesia was not entrusted to the U.S. by the United Nations until 1947. Beginning with the first relocation of the Bikini people to Rongerik Atoll in 1946, the saga of the Marshall Islands involvement in the atomic age began. Although the testing program was limited to the years 1946 through 1958, many of the consequences and events related to the testing program continued over the decades since. That story is still ongoing with programs currently underway to attempt to resettle previously displaced communities, remediate contaminated islands, and to settle claims of damages to individuals and communities. The history of the years subsequent to 1958 are a mixed chronicle of a few original scientific investigations aimed at understanding the coral atoll environment, continued surveillance of the acutely exposed Marshallese, some efforts at cleanup and remediation, numerous monitoring programs and many studies repeated either for credibility purposes, to satisfy international demands or because the changing state of knowledge of radiation protection has necessitated us to rethink earlier beliefs and conclusions about late health effects and social consequences. The objective of this paper is to briefly note many of the historical and political events, scientific studies, persons and publications from 1946 to the present that relate to atomic weapons testing in the Marshall Islands.

Exposure setup to test effects of wireless communications systems on the CNS.

Abstract: This paper presents an exposure setup designed for in vivo studies of possible effects on the central nervous system due to the electromagnetic exposure from handheld mobile communications equipment. The setup consists of a carousel on which 10 rats, each restrained in a radially positioned tube, are exposed to the electromagnetic field emanating from a dipole antenna at the center. The rats are positioned with their snouts at a distance of 35 mm from the dipole antenna. The tubes restrain the movement of the animals to such an extent as to allow for well defined exposure conditions, yet without totally immobilizing them. Numerical and experimental dosimetric analysis of the setup was conducted using rats weighing 250-300 g at a frequency of 900 MHz. A detailed rat phantom derived from MRI scans was developed for the numerical assessment with a commercially available code based on the finite integration technique. The results were validated by measurements of the temperature rise in selected points of a rat cadaver. The dosimetric analysis shows that the setup is eminently suitable for central nervous system studies. It enables well defined field strengths to be induced in the brain tissue, whereby the variations in the specific absorption rate averaged over the brain tissue caused by movement and varying animal sizes was shown to be less than +/-16%. The specific absorption rate distribution in the brain is nonhomogeneous but comparable to that induced in the brain of a human using a handheld wireless phone. The efficiency of the exposure is about 0.20+/-0.05 mW g(-1) for the brain average value per 100 mA feedpoint current. The whole-body average specific absorption rate is considerably lower, i.e., about half of that of the brain averaged value. In addition, the setup has been proven to be practical in use, and the stress levels caused by restraining the animals in this setup are deemed by neurologists and veterinary scientists to be very low.

Anomaly in atmospheric radon concentration: A possible precursor of the 1995 Kobe, Japan, earthquake

Abstract: Clear seismic-related anomalies in the radon ({sup 222}Rn) concentration of the atmosphere were observed prior to the Kobe earthquake (magnitude 7.2) on 17 January 1995. The radon anomalies were observed at a monitoring station in Kobe, which is located about 20 km away from the epicenter. The means of radon concentration in the atmosphere for each day were calculated using the data observed between April 1984 and March 1994, in order to obtain the normal radon variation. The difference between the smoothed radon concentration and the smoothed mean radon concentration is the residual value. Using the weekly averages of residual values in the historical period, the weekly residual value in the validation period were predicted. The historical period was from April 1984 to March 1994. The validation period was from April 1994 to January 1996. The seismic-related radon anomaly higher than the 99% confidence limit of the residual value of radon concentration in the atmosphere was observed beginning about 2 mo before the earthquake. 7 refs., 5 figs.

Radiation exposure during cardiology fellowship training.

Abstract: We report catheterization laboratory personnel dose per case during parallel use of two laboratories from different manufacturers. Initially, four working positions were monitored. Review of the data from the first 140 cases showed a wide range of dose per case. Measurements were then limited to diagnostic coronary angiography cases in which a cardiology fellow was the primary operator. On a per case basis, the dose was higher when a fellow was in the laboratory with pulsed progressive fluoroscopy or was in fellowship year one. The increased dose for first year fellows was more related to increased fluoroscopy time than to cine angiography time. This study emphasizes the importance of close supervision of cardiology fellows early in their training to limit dose to patients and personnel, and it underlines the importance of each catheterization laboratory routinely having the actual personnel dose per case measured.

An updated dose assessment for resettlement options at Bikini Atoll--a U.S. nuclear test site.

Abstract: On 1 March 1954, a nuclear weapon test, codenamed BRAVO, conducted at Bikini Atoll in the northern Marshall Islands contaminated the major residence island. There has been a continuing effort since 1977 to refine dose assessments for resettlement options at Bikini Atoll. Here we provide a ra

Radon in residences: influences of geological and housing characteristics.

Abstract: 222Rn is a radioactive gas emitted during the decay of 238U. 222Rn is a recognized lung carcinogen in humans and a common indoor air contaminant. This paper describes the results of research undertaken in 894 residences of the Province of Quebec (Canada), in which one of the objectives was to evaluate the influence of geological and housing characteristics on 222Rn levels. After a random selection of homes, 222Rn concentrations were measured with alpha track detectors in the basement and the main bedroom during two consecutive 6-mo periods. Geological subsoil characteristics were determined from various sources (e.g., geological maps, databanks on uranium sampling in lake and stream sediments), and housing characteristics were documented with a questionnaire. Statistical variance analysis of data indicates that geological factors only explain 5% and 4.5% of the variations in 222Rn concentrations, respectively, in the basement and on the first floor. When variables relative to housing characteristics are added, the analysis explains only 18% and 15% of the variations in 222Rn concentrations in the basement and on the first floor. These results illustrate the difficulties in predicting 222Rn concentrations in homes.

Past and present levels of some radionuclides in fish from Bikini and Enewetak Atolls.

Abstract: Bikini and Enewetak were the sites in the Northern Marshall Islands that were used by the United States as testing grounds for nuclear devices between 1946 and 1958. The testing produced close-in fallout debris that was contaminated with different radionuclides and which entered the aquatic environment. The contaminated lagoon sediments became a reservoir and source term of manmade radionuclides for the resident marine organisms. This report contains a summary of all the available data on the concentrations of 137Cs, 60Co and 207Bi in flesh samples of reef and pelagic fish collected from Bikini and Enewetak Atolls between 1964 and 1995. The selection of these three radionuclides for discussion is based on the fact that these are the only radionuclides that have been routinely detected by gamma spectrometry in flesh samples from all fish for the last 20 y. Flesh from fish is an important source of food in the Marshallese diet. These radionuclides along with the transuranic radionuclides and 90Sr contribute most of the small radiological dose from ingesting marine foods. Some basic relationships among concentrations in different tissues and organs are discussed. The reef fish can be used as indicator species because their body burden is derived from feeding, over a lifetime, within a relatively small contaminated area of the lagoon. Therefore, the emphasis of this report is to use this extensive and unique concentration data base to describe the effective half lives and cycling for the radionuclides in the marine environments during the 31-y period between 1964 and 1995. The results from an analysis of the radionuclide concentrations in the flesh samples indicate the removal rates for the 3 radionuclides are significantly different. 137Cs is removed from the lagoons with an effective half life of 9-12 y. Little 60Co is mobilized to the water column so that it is depleted in both environments, primarily through radioactive decay. The properties of 207Bi are different at Enewetak and Bikini. At Enewetak the radionuclide is lost from the environment with an effective half live of 5.1 y. At Bikini only radioactive decay can account for the rate at which the radionuclide is lost from the lagoon. The difference in the binding properties of the sedimentary materials for 207Bi among the two Atolls is not understood.

Towards a generalized model for the primary and secondary contamination of lakes by Chernobyl-derived radiocesium

Abstract: As part of the UK Ministry of Agriculture Fisheries and Food Directorate of Fisheries Research (MAFF/DFR) post-Chernobyl monitoring program, a detailed study was carried out of the change over time in dissolved-phase {sup 137}Cs concentrations in a number of lakes in Cumbria, UK. These measurements have been combined with published data on {sup 137}Cs in Cumbrian and other European lakes in order to develop and test a {open_quotes}double exponential{close_quotes} model for changes in lakewater concentrations: A exp(-k{sub 1}t) + B exp(-k{sub 2}t) where the exponential terms correspond. respectively, to the initial fast flush of activity through the system followed by longer-term transfers (timescale, years) from the catchment. Parameter values have been determined for this model by curve-fitting to the set of measurements of post-Chernobyl {sup 137}Cs activities in lakes. Values of fitted parameters are shown to be related, in a simple manner, to the physical characteristics of the system, in particular water residence time and mean lake depth. These parameters are generalized to give a simple empirical model for the full set of study lakes. The model is shown to give estimates of {sup 137}Cs activity to within a factor of 5 of field data for a period of severalmore » years after the fallout. Initial fractional losses of activity from catchment to lake were determined to be within the range 0.44-8.7% per year, declining exponentially with a mean rate constant 0.98 x 10{sup -3} d{sup -1}. 33 refs., 6 figs., 5 tabs.« less

Measurement and Application of Uranium Isotopes for Human and Environmental Monitoring

Abstract: An improved method is described utilizing extraction chromatography, anion exchange, and alpha spectroscopy for measurement of uranium isotopes in human and environmental surveillance studies. These methods provide a sensitivity of {approximately}0.7 mBq per isotope per sample and are generally accurate within the precision of the measurements. The extraction chromatography methods greatly simplify separation of uranium from iron in silicate matrices and provide increased sample throughput and data quality for water, soil, and air filter samples. For bioassay samples, the coprecipitation/anion exchange/alpha spectrometric methods provide rapid throughput and sufficient sensitivity to meet new analytical performance standards in human monitoring studies. In addition, the {sup 234}U:{sup 238}U data can be used as a fingerprint of natural vs. anthropogenic sources of uranium. For 1995 data from our laboratory, a large percentage (79-94% by matrix) of samples appear to be of natural {sup 234}U:{sup 238}U isotopic composition. For all matrices, samples with higher uranium concentration generally have more depleted isotopic composition (smaller {sup 234}U:{sup 238}U). A small percentage of soil (11%), air filter (3%), urine (3%), and water (3%) samples have depleted isotopic signatures at the 95% confidence interval, indicating anthropogenic contributions of uranium to these samples. 29 refs., 5 figs., 2 tabs.

UV protection by clothing: an intercomparison of measurements and methods.

Abstract: In an attempt to reduce the incidence of skin cancer, cancer foundations have run educational campaigns which encourage the general population to limit their solar UVR exposures. An important part of these campaigns, in particular in Australia, but also more recently in Europe and the U.S., has been the adoption of protective measures such as sunscreens, hats, sunglasses and clothing. The protective properties of fabrics and clothing against ultraviolet radiation (UVR) have been known for some time, but recently there has been considerable interest in quantifying the degree of protection. This has been generated, in part, by the requirements for occupational protection for outdoor workers as well as the provision of UVR protection for the recreational market. The quantification of UVR protection has been laboratory based using in vitro test methods. Development of a standard test method has become an important part of the testing process, and this paper presents results from an intercomparison involving five independent testing laboratories. Agreement is good, in particular for samples with protection factors below 50. Technical difficulties and sources of errors associated with the measurements are discussed.

Lung cancer rate vs. mean radon level in U.S. counties of various characteristics.

Abstract: Plots of lung cancer rates corrected for smoking prevalence vs. average home radon levels are presented for U.S. counties with a wide variety of socioeconomic characteristics. The data are generally well described by the same negative slope linear, plus positive slope quadratic, "standard" curve. Plots are presented for geographic regions and these are also reasonably well fit by the standard curve. The findings are not consistent with predictions based on a linear no-threshold model.

60Co contamination in recycled steel resulting in elevated civilian radiation doses: Causes and challenges

Abstract: Since late 1992, more than 100 building complexes containing public and private schools and nearly 1,000 apartments have been identified in Taiwan with elevated levels of gamma-radiation from construction steel contaminated with 60 Co. Due to improper handling of 60 Co contaminated scrap steel in late 1982 and 1983, contaminated construction materials have been widely distributed throughout the country. These contaminated construction materials have generated elevated radiation exposures to members of the public in Taiwan. As of early 1996, more than 4,000 people, including young students, have been identified as receiving more than 1 mSv y -1 above the local background for up to 12 y. This report provides a detailed discussion of the sources of the 60 Co contamination in construction steel, its discovery in the building complexes, and preliminary evaluation and remediation activities.

Security on the Internet.

Abstract: Overview of Internet security As of 1996, the Internet connected an estimated 13 million computers in 195 countries on every continent, even Antarctica (1). The Internet is not a single network, but a worldwide collection of loosely connected networks that are accessible by individual computer hosts in a variety of ways, including gateways, routers, dialup connections, and Internet service providers. The Internet is easily accessible to anyone with a computer and a network connection. Individuals and organizations worldwide can reach any point on the network without regard to national or geographic boundaries or time of day.

Findings of the first comprehensive radiological monitoring program of the Republic of the Marshall Islands

Abstract: The Marshall Islands was the primary site of the United States atomic weapons testing program in the Pacific. From 1946 through 1958, 66 atomic weapons were detonated in the island country. For several decades, monitoring was conducted by the U.S. Department of Energy (or its predecessor agencies) on the test site atolls and neighboring atolls. However, 70% of the land area of the over 1,200 islands in the Marshall Islands was never systematically monitored prior to 1990. For the 5-y period from 1990 through 1994, the Government of the Republic of the Marshall Islands undertook an independent program to assess the radiological conditions throughout its 29 atolls. The scientific work was performed under the auspices of the Section 177 Agreement of the Compact of Free Association, U.S. public law 99-239, signed in 1986 by President Ronald Reagan. Although the total land area of the nations is a scant 180 km2, the islands are distributed over 6 x 10(5) km2 of ocean. Consequently, logistics and instrumentation were main considerations, in addition to cultural and language issues. The core of the monitoring program was in-situ gamma spectrometry measurements made on more than 400 islands. Native foods including coconuts and other tropical fruits were sampled as well as more than 200 soil profiles and more than 800 surface soil samples. The fruits, soil profiles and surface soil samples have been analyzed for all gamma emitters with an emphasis on determining concentrations of 137Cs; the surface soil samples were also analyzed for 239+240Pu. All measurements were conducted in a radiological laboratory built in the capital city of the Marshall Islands specifically for the purposes of this study. The program was extensively assisted in the field and in the laboratory by Marshallese workers. The interpretation of environmental radiation data in the Marshall Islands required thoughtful analysis because the atolls lie along a latitude and precipitation gradient that effected the deposition of local and global fallout. The objective of this paper is to report findings for all atolls of the Marshall Islands on the 137Cs areal inventory (Bq m(-2)) and the external effective dose-rate (mSv y(-1)), the projected internal effective dose-rate (mSv y(-1)) from an assumed diet model, and surface soil concentrations of 239,240Pu (Bq kg(-1)) for selected northern atolls. Interpretation is also provided on the degree of contamination above global fallout levels. This report provides the first comprehensive summary of the radiological conditions throughout the Marshall Islands.

Fundamentals for establishing a risk communication program.

Abstract: This paper provides a suggested outline for developing a risk communication organizational plan that could be used by a variety of federal, state, or private agencies. Drawing on various techniques presented in the literature and on the authors' insights, suggestions are provided as to how to formulate and convey risk messages. First, the paper provides a few risk communication fundamentals including definitions, the goal of informing vs. influencing, the importance of public participation in risk management, building trust and credibility, the consideration of outrage, and the importance of oral and visual communications. Second, a stepwise approach synthesized by the authors is presented that can be applied in developing a risk communication program. The approach is a 13-step method based on the premise that the risk communication program should be dynamic, flexible, and involve interaction with the public at every possible step.

A survey of radon and thoron progeny for dwellings in Hong Kong.

Abstract: The potential alpha energy concentrations of radon and thoron progeny have been surveyed for dwellings in Hong Kong and the mean values are obtained as 3.58 and 2.29 mWL, respectively. The relative importance of the value for thoron is unexpectedly high, which is attributed to the high 232 Th content of the building materials used in Hong Kong. It has also been found that the potential alpha energy concentration values for radon progeny changed dramatically with the season due to the different aerosol contents in the air in different seasons. The factors affecting the potential alpha energy concentration values have also been studied. These factors fall into three categories, namely (1) the building characteristics including age of the buildings, wall coverings and floor coverings; (2) the location of sites including nearby environments and the elevation of the sites; and (3) the meteorological parameters including wind speed, atmospheric pressure, air temperature and relative humidity. For categories (1) and (2), all factors seem to affect the potential alpha energy concentration values, although the effects may be different for radon and thoron progeny, which may be due to the very much different half lives of radon and thoron gas and to the different behavior of radon and thoron progeny in the attachment to aerosols. For category (3), only wind speed has been found to have effects.

Summary and evaluation of guidelines for occupational exposure to power frequency electric and magnetic fields

Abstract: Major U.S. and international guidelines for limiting occupational exposures to EMF are evaluated. These safety guidelines are designed to prevent short-term adverse effects by maintaining bulk-tissue current densities below 10 mA m(-2) (rms). Above this level, effects of induced currents and electric fields can include stimulation of neural and cardiac tissues. The models and input data used by guideline-setting organizations to relate 50/60-Hz magnetic-field exposures to induced current densities differ significantly. In order to develop a better understanding of such differences, the current densities derived from exposure guideline models are compared to minimum thresholds for cardiac stimulation and fibrillation. The nominal minimum thresholds for cardiac stimulation and ventricular fibrillation are 100 times and 200 times greater, respectively, than the current density of 10 mA m(-2) used as a dosimetric limit. However, the assumed relationship between the 10 mA m(-2) dose limit and magnetic field exposure limits introduces additional uncertainty. The ratios between the threshold for cardiac stimulation and the calculated induced current density at the exposure limit vary between a low of 50 and a high of 526, depending upon the guideline. These ratios, as indicators of implicit safety factors, are larger than those recommended to protect against adverse effects of induced current density, including cardiac stimulation, in magnetic resonance imaging or against adverse effects of toxic chemical exposures. This review and assessment of EMF occupational exposure guidelines suggests that several scientific and compliance issues remain ambiguous or unresolved. Recommendations are made for guideline organizations to strengthen and clarify the scientific basis for the guideline process. These recommendations include the documentation of supporting data, development of operational definitions for guidelines, examination of dosimetric models, clarification of safety factors, and identification of high priority topics for future research.

A history of the people of Bikini following nuclear weapons testing in the Marshall Islands : With recollections and views of elders of Bikini Atoll

Abstract: The people of Bikini Atoll were moved from their homeland in 1946 to make way for the testing of 23 nuclear weapons by the United States government, beginning with the world's fourth atomic detonation. The subsequent half-century exodus of the Bikini people included a 2-y stay on Rongerik Atoll, where near starvation resulted, and a 6-mo sojourn on Kwajalein Atoll, where they lived in tents beside a runway used by the U.S. military. In 1948, they were finally relocated to Kili, a small, isolated, 200-acre island owned by the U.S. Trust Territory government. Numerous hardships have been faced there, not the least of which was the loss of skills required for self-sustenance. Located 425 miles south of Bikini, Kili Island is without a sheltered lagoon. Thus for six months of the year, fishing and sailing become futile endeavors. Because of the residual radioactive contamination from the nuclear testing, the majority of the Bikinian population still resides on Kili today. One attempt was made to resettle Bikini in the late 1960's when President Lyndon B. Johnson, on recommendations from the Atomic Energy Commission, declared Bikini Atoll safe for habitation. In 1978, however, it was discovered by the U.S. Department of Energy that in the span of only one year, some of the returned islanders were showing a 75% increase in their body burdens of 137Cs. In 1978, the people residing on Bikini were moved again, this time to a small island in Majuro Atoll. In the early 1980's, the Bikinians filed a class action lawsuit against the U.S. government for damages arising out of the nuclear testing program. Although the claim was dismissed, eventually a $90 million trust fund was established for their local government. Since then the leaders of the people of Bikini residing on Kili Island and Majuro Atoll have been confronted with the immense responsibility of determining how to clean their atoll while at the same time maintaining the health and welfare of their displaced population. For the community and their leaders, grappling with these technical decisions has created a life of strife, debate and conflict-and an uncertain future. Now, a radiological cleanup of Bikini is expected to begin sometime within 1997. The objective of this paper, with the support of the views and the recollections of elder Bikinians, is to recount the history and discuss issues facing the first displaced people of the nuclear age.

The Northern Marshall Islands Radiological Survey: data and dose assessments.

Abstract: Fallout from atmospheric nuclear tests, especially from those conducted at the Pacific Proving Grounds between 1946 and 1958, contaminated areas of the Northern Marshall Islands. A radiological survey at some Northern Marshall Islands was conducted from September through November 1978 to eva

A compilation of nuclear weapons test detonation data for U.S. Pacific ocean tests

Abstract: Prior to December 1993, the explosive yields of 44 of 66 nuclear tests conducted by the United States in the Marshall Islands were still classified. Following a request from the Government of the Republic of the Marshall Islands to the U.S. Department of Energy to release this information, the Secretary of Energy declassified and released to the public the explosive yields of the Pacific nuclear tests. This paper presents a synopsis of information on nuclear test detonations in the Marshall Islands and other locations in the mid-Pacific including dates, explosive yields, locations, weapon placement, and summary statistics.

An investigation into the prevalence of thyroid disease on Kwajalein Atoll, Marshall Islands

Abstract: The objective of the study was to obtain thyroid disease rate statistics on as much of the population as possible that was alive during the years of nuclear testing and to test the hypothesis that described a linearly decreasing prevalence of palpable nodules with increasing distance from the Bikini test site. 1,322 Marshallese born before 1965 were given a thyroid examination using neck palpation, fine needle aspiration biopsy, and high resolution ultrasound imaging. Approximately 40% of the total population living on this island who are at risk from exposure to radioactive fallout during the years 1946-1958 were screened. Of that group, 815 were alive at the time of the BRAVO test on 1 March 1954. Two hundred sixty-six people with thyroid nodules were found (32.6%): 132 were palpable nodules (16.2%), and 134 were nodules that could be diagnosed with ultrasound only (15.7%). Prevalence of palpable nodules was particularly high in men and women older than 60 y, in men who were 6 to 15 y of age at the time of the BRAVO test, and in women 1 to 10 y of age at the time of the BRAVO test. In 22 people, the clinical diagnosis was most likely cancermore » though histopathological evidence was only available from 11 operated cases. Of the 11 operated cases, 10 were cancer. Cancer prevalence was particularly high in those women born between 1944 and 1953 (7/220 = 3.2%), i.e., who were children during the early years of nuclear testing. The Ebeye data showed a marginally significant correlation between palpable nodule prevalence among women and distance to Bikini (r = -0.44, p = 0.06). This report summarizes the clinical findings of the thyroid examinations, the age distributions for nodular disease and cancer, and examines the relationship between prevalence of nodules and present day levels of {sup 137}Cs in the environment of each atoll. 22 refs., 4 figs., 9 tabs.« less