Estimation of Radiation Doses in the Marshall Islands Based on Whole Body Counting of Cesium-137 (137Cs) and Plutonium Urinalysis

Under the auspices of the U.S. Department of Energy (USDOE), researchers from the Lawrence Livermore National Laboratory (LLNL) have recently implemented a series of initiatives to address long-term radiological surveillance needs at former nuclear test sites in the Republic of the Marshall Islands (RMI). The aim of this radiological surveillance monitoring program (RSMP) is to provide timely radiation protection for individuals in the Marshall Islands with respect to two of the most important internally deposited fallout radionuclides-cesium-137 ({sup 137}Cs) and long-lived isotopes 239 and 240 of plutonium ({sup 239+240}Pu) (Robison et al., 1997 and references therein). Therefore, whole-body counting for {sup 137}Cs and a sensitive bioassay for the presence of {sup 239+240}Pu excreted in urine were adopted as the two most applicable in vivo analytical methods to assess radiation doses for individuals in the RMI from internally deposited fallout radionuclides (see Hamilton et al., 2006a-c; Bell et al., 2002). Through 2005, the USDOE has established three permanent whole-body counting facilities in the Marshall Islands: the Enewetak Radiological Laboratory on Enewetak Atoll, the Utrok Whole-Body Counting Facility on Majuro Atoll, and the Rongelap Whole-Body Counting Facility on Rongelap Atoll. These whole-body counting facilities are operated and maintained by trained Marshallese technicians. Scientists from LLNL provide the technical support and training necessary for maintaining quality assurance for data acquisition and dose reporting. This technical basis document summarizes the methodologies used to calculate the annual total effective dose equivalent (TEDE; or dose for the calendar year of measurement) based on whole-body counting of internally deposited {sup 137}Cs and the measurement of {sup 239+240}Pu excreted in urine. Whole-body counting provides a direct measure of the total amount (or burden) of {sup 137}Cs present in the human body at the time of measurement. The amount of {sup 137}Cs detected is often reported in activity units of kilo-Becquerel (kBq), where 1 kBq equals 1000 Bq and 1 Bq = 1 nuclear transformation per second (t s{sup -1}). [However, in the United States the Curie (Ci) continues to be used as the unit of radioactivity; where 1 Ci = 3.7 x 10{sup 10} Bq.] The detection of {sup 239}Pu and {sup 240}Pu in bioassay (urine) samples indicates the presence of internally deposited (systemic) plutonium in the body. Urine samples that are collected in the Marshall Islands from volunteers participating in the RSMP are transported to LLNL, where measurements for {sup 239+240}Pu are performed using a state-of-the-art technology based on Accelerator Mass Spectrometry (AMS) (Hamilton et al., 2004, 2007; Brown et al., 2004). The urinary excretion of plutonium by RSMP volunteers is usually described in activity units, expressed as micro-Becquerel ({micro}Bq) of {sup 239+240}Pu (i.e., representing the sum of the {sup 239}Pu and {sup 240}Pu activity) excreted (lost) per day (d{sup -1}), where 1 {micro}Bq d{sup -1} = 10{sup -6} Bq d{sup -1} and 1 Bq = 1 t s{sup -1}. The systemic burden of plutonium is then estimated from biokinetic relationships as described by the International Commission on Radiological Protection (e.g., see ICRP, 1990). In general, nuclear transformations are accompanied by the emission of energy and/or particles in the form of gamma rays ({gamma}), beta particles ({beta}), and/or alpha particles ({alpha}). Tissues in the human body may adsorb these emissions, where there is a potential for any deposited energy to cause biological damage. The general term used to quantify the extent of any radiation exposure is referred to as the dose. The equivalent dose is defined by the average absorbed dose in an organ or tissue weighted by the average quality factor for the type and energy of the emission causing the dose. The effective dose equivalent (EDE; as applied to the whole body), is the sum of the average dose equivalent for each tissue weighted by each applicable tissue-specific weighing factor (which equates to the sensitivity of that tissue to damage by the equivalent radiation dose it receives). The SI unit of effective dose equivalent is the joule per kilogram (J kg{sup -1}), named the Sievert (Sv). The unit often used by federal and state agencies in the United States to describe EDE continues to be the more historical radiation equivalent man (rem); where 1 rem = 0.01 Sv

Individual Radiological Protection Monitoring of Utrok Atoll Residents Based on Whole Body Counting of Cesium-137 (137Cs) and Plutonium Bioassay

This report contains individual radiological protection surveillance data developed during 2006 for adult members of a select group of families living on Utrok Atoll. These Group I volunteers all underwent a whole-body count to determine levels of internally deposited cesium-137 ({sup 137}Cs) and supplied a bioassay sample for analysis of plutonium isotopes. Measurement data were obtained and the results compared with an equivalent set of measurement data for {sup 137}Cs and plutonium isotopes from a second group of adult volunteers (Group II) who were long-term residents of Utrok Atoll. For the purposes of this comparison, Group II volunteers were considered representative of the general population on Utrok Atoll. The general aim of the study was to determine residual systemic burdens of fallout radionuclides in each volunteer group, develop data in response to addressing some specific concerns about the preferential uptake and potential health consequences of residual fallout radionuclides in Group I volunteers, and generally provide some perspective on the significance of radiation doses delivered to volunteers (and the general Utrok Atoll resident population) in terms of radiological protection standards and health risks. Based on dose estimates from measurements of internally deposited {sup 137}Cs and plutonium isotopes, the data and information developed in this report clearly show that neither volunteer group has acquired levels of internally deposited fallout radionuclides specific to nuclear weapons testing in the Marshall Islands that are likely to have any consequence on human health. Moreover, the dose estimates are well below radiological protection standards as prescribed by U.S. regulators and international agencies, and are very small when compared to doses from natural sources of radiation in the Marshall Islands and the threshold where radiation health effects could be either medically diagnosed in an individual or epidemiologically discerned in a group of people. In general, the results from the whole-body counting measurements of 137Cs are consistent with our knowledge that a key pathway for exposure to residual fallout contamination on Utrok Atoll is low-level chronic uptake of {sup 137}Cs from the consumption of locally grown produce (Robison et al., 1999). The error-weighted, average body burden of {sup 137}Cs measured in Group I and Group II volunteers was 0.31 kBq and 0.62 kBq, respectively. The associated average, annual committed effective dose equivalent (CEDE) delivered to Group I and Group II volunteers from {sup 137}Cs during the year of measurement was 2.1 and 4.0 mrem. For comparative purposes, the annual dose limit for members of the public as recommended by the National Council on Radiation Protection and Measurements (NCRP) and the International Commission on Radiological Protection (ICRP) is 100 mrem. Consequently, specific concerns about elevated levels of {sup 137}Cs uptake and higher risks from radiation exposure to Group I volunteers would be considered unfounded. Moreover, the urinary excretion of plutonium-239 ({sup 239}Pu) from Group I and Group II volunteers is statistically indistinguishable. In this case, the error-weighted, average urinary excretion of {sup 239}Pu from Group I volunteers of 0.10 {mu}Bq per 24-h void with a range between -0.01 and 0.23 {mu}Bq per 24-h void compares with an error-weighted average from Group II volunteers of 0.11 {mu}Bq per 24-h void with a range between -0.20 and 0.47 {mu}Bq per 24-h void. The range in urinary excretion of {sup 239}Pu from Utrok Atoll residents is very similar to that observed for other population groups in the Marshall Islands (Bogen et al., 2006; Hamilton et al., 2006a; 2006b; 2006c, 2007a; 2007b; 2007c) and is generally considered representative of worldwide background

Absolute calibration in vivo measurement systems

Lawrence Livermore National Laboratory (LLNL) is currently investigating a new method for obtaining absolute calibration factors for radiation measurement systems used to measure internally deposited radionuclides in vivo. Absolute calibration of in vivo measurement systems will eliminate the need to generate a series of human surrogate structures (i.e., phantoms) for calibrating in vivo measurement systems. The absolute calibration of in vivo measurement systems utilizes magnetic resonance imaging (MRI) to define physiological structure, size, and composition. The MRI image provides a digitized representation of the physiological structure, which allows for any mathematical distribution of radionuclides within the body. Using Monte Carlo transport codes, the emission spectrum from the body is predicted. The in vivo measurement equipment is calibrated using the Monte Carlo code and adjusting for the intrinsic properties of the detection system. The calibration factors are verified using measurements of existing phantoms and previously obtained measurements of human volunteers. 8 refs

Setting standards for radiation protection: A time for change

In 1950, the International Commission on Radiation Protection (ICRP) recommended that ``certain radiation effects are irreversible and cumulative.`` Furthermore, the ICRP ``strongly recommended that every effort be made to reduce exposures to all types of ionizing radiations to the lowest possible level.`` Then in 1954, the ICRP published its assumption that human response to ionizing radiation was linear with dose, together with the recommendation that exposures be kept as low as practicable. These concepts are still the foundation of radiation protection policy today, even though, as Evans has stated, ``The linear non-threshold (LNT) model was adopted specifically on a basis of mathematical simplicity, not from radio-biological data.... Groups responsible for setting standards for radiation protection should be abreast of new developments and new data as they are published; however, this does not seem to be the case. For example, there have been many reports in scientific, peer-reviewed, and other publications during the last three decades that have shown the LNT model and the policy of As Low As Reasonably Achievable (ALARA) to be invalid. However, none of these reports has been refuted or even discussed by standard-setting groups. We believe this mandates a change in the standard-setting process

Thyroid phantom measurements in joint EURADOS-LLNL intercomparison exercise

International audienceThe European Radiation Dosimetry Group (EURADOS), in collaboration with Lawrence Livermore National Laboratory's (LLNL's) Thyroid Intercomparison Program (TRIP), conducted an intercomparison exercise consistent with the goals of EURADOS. In total, 35 in vivo radiobioassay facilities from 18 countries participated to evaluate the differences between the neck and thyroid phantoms specified in two standards issued by the American National Standards Institute. Radioiodine (125I and 131I) measurement results were compared to the traceable standard activity levels added to each phantom. Measurement data showed no statistically significant differences between normalized activity measurements of the thyroid phantom types (20 and 30 ml). Differences were noted between the laboratories that routinely participate in the radioiodine thyroid intercomparison program (TRIP participants) and laboratories that have not previously participated in TRIP. Evaluation of the reasons for these differences will require additional EURADOS-LLNL collaborations. Finally, the measurement data from this intercomparison was used with a designed intake scenario for intercomparison of dose evaluations. Results from the dose intercomparison will be presented in a subsequent article. © The Author 2017. Published by Oxford University Press. All rights reserved

Apoptosis in cervical squamous carcinoma: predictive value for survival following radiotherapy

Background—Apoptosis, or programmed cell death, can be induced by radiotherapy. The extent of apoptosis in a tumour before treatment may have important implications for response to radiotherapy and long term survival. Aim—To examine the extent of apoptosis in tumour tissue from patients with squamous carcinoma of the cervix before radiotherapy, and to correlate this with response to treatment and prognosis. Methods—The percentage of apoptotic cells was assessed in 146 carcinomas of the cervix from patients scheduled to receive radiotherapy. The CAS 200 static image analysis system was used to count the number of tumour nuclei per high power field, while the numbers of apoptotic cells in the same field were visualised simultaneously on the image analyser and recorded manually. Results—The median apoptotic level was 0.73%. Patients were divided into two groups around the median. There was no statistically significant difference in outcome between the two groups as determined by long term survival following radiotherapy. Conclusions—The CAS 200 static image analyser system can be used to assist in the rapid semiautomated assessment of apoptosis in conventionally prepared tissue. The results suggest that the apoptotic state of a tumour before treatment is of no value in predicting response to radiotherapy and subsequent prognosis. Tumour stage, size, and BrdU labelling index, as a measure of proliferation rate, remain the most important prognostic factors in terms of predicting local tumour control. Key Words: apoptosis • uterine cervix • squamous cell carcinom

Description of a new species of Pinnotheres

Roderic D. M. Page (1983): Description of a new species of Pinnotheres, and redescription of P. novaezelandiae fBrachyura: Pinnotheridae). New Zealand Journal of Zoology 10: 151-162, DOI: 10.1080/03014223.1983.1042390