David C. Kocher

Derivation of a screening methodology for evaluating radiation dose to aquatic and terrestrial biota.

The United States Department of Energy (DOE) currently has in place a radiation dose standard for the protection of aquatic animals, and is considering additional dose standards for terrestrial biota. These standards are: 10 mGy/d for aquatic animals, 10 mGy/d for terrestrial plants, and, 1 mGy/d for terrestrial animals. Guidance on suitable approaches to the implementation of these standards is needed. A screening methodology, developed through DOEs Biota Dose Assessment Committee (BDAC), serves as the principal element of DOEs graded approach for evaluating radiation doses to aquatic and terrestrial biota. Limiting concentrations of radionuclides in water, soil, and sediment were derived for 23 radionuclides. Four organism types (aquatic animals; riparian animals; terrestrial animals; and terrestrial plants) were selected as the basis for development of the screening method. Internal doses for each organism type were calculated as the product of contaminant concentration, bioaccumulation factor(s) and dose conversion factors. External doses were calculated based on the assumption of immersion of the organism in soil, sediment, or water. The assumptions and default parameters used provide for conservative screening values. The screening methodology within DOEs graded approach should prove useful in demonstrating compliance with biota dose limits and for conducting screening assessments of radioecological impact. It provides a needed evaluation tool that can be employed within a framework for protection of the environment.

INTERACTIVE RADIOEPIDEMIOLOGICAL PROGRAM (IREP): A WEB-BASED TOOL FOR ESTIMATING PROBABILITY OF CAUSATION/ASSIGNED SHARE OF RADIOGENIC CANCERS

The Interactive RadioEpidemiological Program (IREP) is a Web-based, interactive computer code that is used to estimate the probability that a given cancer in an individual was induced by given exposures to ionizing radiation. IREP was developed by a Working Group of the National Cancer Institute and Centers for Disease Control and Prevention, and was adopted and modified by the National Institute for Occupational Safety and Health (NIOSH) for use in adjudicating claims for compensation for cancer under the Energy Employees Occupational Illness Compensation Program Act of 2000. In this paper, the quantity calculated in IREP is referred to as “probability of causation/assigned share” (PC/AS). PC/AS for a given cancer in an individual is calculated on the basis of an estimate of the excess relative risk (ERR) associated with given radiation exposures and the relationship PC/AS = ERR/ERR+1. IREP accounts for uncertainties in calculating probability distributions of ERR and PC/AS. An accounting of uncertainty is necessary when decisions about granting claims for compensation for cancer are made on the basis of an estimate of the upper 99% credibility limit of PC/AS to give claimants the “benefit of the doubt.” This paper discusses models and methods incorporated in IREP to estimate ERR and PC/AS. Approaches to accounting for uncertainty are emphasized, and limitations of IREP are discussed. Although IREP is intended to provide unbiased estimates of ERR and PC/AS and their uncertainties to represent the current state of knowledge, there are situations described in this paper in which NIOSH, as a matter of policy, makes assumptions that give a higher estimate of the upper 99% credibility limit of PC/AS than other plausible alternatives and, thus, are more favorable to claimants.

Principles and issues in radiological ecological risk assessment

This paper provides a bridge between the fields of ecological risk assessment (ERA) and radioecology by presenting key biota dose assessment issues identified in the US Department of Energys Graded Approach for Evaluating Radiation Doses to Aquatic and Terrestrial Biota in a manner consistent with the US Environmental Protection Agencys framework for ERA. Current radiological ERA methods and data are intended for use in protecting natural populations of biota, rather than individual members of a population. Potentially susceptible receptors include vertebrates and terrestrial plants. One must ensure that all media, radionuclides (including short-lived radioactive decay products), types of radiations (i.e., alpha particles, electrons, and photons), and pathways (i.e., internal and external contamination) are combined in each exposure scenario. The relative biological effectiveness of alpha particles with respect to deterministic effects must also be considered. Expected safe levels of exposure are available for the protection of natural populations of aquatic biota (10 mGy d(-1)) and terrestrial plants (10 mGy d(-1)) and animals (1 mGy d(-1)) and are appropriate for use in all radiological ERA tiers, provided that appropriate exposure assumptions are used. Caution must be exercised (and a thorough justification provided) if more restrictive limits are selected, to ensure that the supporting data are of high quality, reproducible, and clearly relevant to the protection of natural populations.

Beyond dose assessment: using risk with full disclosure of uncertainty in public and scientific communication.

Evaluations of radiation exposures of workers and the public traditionally focus on assessments of radiation dose, especially annual dose, without explicitly evaluating the health risk associated with those exposures, principally the risk of radiation-induced cancer. When dose is the endpoint of an assessment, opportunities to communicate the significance of exposures are limited to comparisons with dose criteria in regulations, doses due to natural background or medical x-rays, and doses above which a statistically significant increase of disease has been observed in epidemiologic studies. Risk assessment generally addresses the chance (probability) that specific diseases might be induced by past, present, or future exposure. The risk of cancer per unit dose will vary depending on gender, age, exposure type (acute or chronic), and radiation type. It is not uncommon to find that two individuals with the same effective dose will have substantially different risks. Risk assessment has shown, for example, that: (a) medical exposures to computed tomography scans have become a leading source of future risk to the general population, and that the risk would be increased above recently published estimates if the incidence of skin cancer and the increased risk from exposure to x-rays compared with high-energy photons were taken into account; (b) indoor radon is a significant contributor to the baseline risk of lung cancer, particularly among people who have never smoked; and (c) members of the public who were exposed in childhood to 131I in fallout from atmospheric nuclear weapons tests and were diagnosed with thyroid cancer later in life would frequently meet criteria established for federal compensation of cancers experienced by energy workers and military participants at atmospheric weapons tests. Risk estimation also enables comparisons of impacts of exposures to radiation and chemical carcinogens and other hazards to life and health. Communication of risk with uncertainty is essential for reaching informed consent, whether communicating to a larger community debating the tradeoffs of risks and benefits of an action that involves radiation exposure or communicating at the level of a physician and patient.

Biological effectiveness of photons and electrons as a function of energy

*Division of Cancer Epidemiology and Genetics, National Canc Institute, Bethesda, MD 20892‐7238; †Texas AM ‡S International, Menlo Park, CA 94025‐3493; §Medical Research Cou cil, Harwell OX11 0RD, United Kingdom; **Center for Risk a Economic Analysis of Terrorism Events, University of Southe California, Los Angeles, CA 90089‐2902; ††Oak Ridge Center f Risk Analysis, Oak Ridge, TN 37830‐7739; ‡‡U.S. Environmen Protection Agency, Washington, DC 20460‐0001; §§Department Epidemiology, School of Public Health, University of North Carolin Chapel Hill, NC 27599‐7435; ***Clarksburg, MD 20871-436 †††Department of Biological Sciences, Wayne State Universi Detroit, MI 48202‐3917; ‡‡‡Department of Radiology, Medici School, Complutense University, Madrid, Spain. The authors declare no conflicts of interest. For correspondence contact: Steven L. Simon, Division of Canc Epidemiology and Genetics, National Cancer Institute, Bethesda, M 20892‐7238, or email at ssimon@mail.nih.gov. (Manuscript accepted 22 October 2012) 0017-9078/15/0 Copyright

John Richard Trabalka (1942–2014).

IT IS with great sadness that we report that our friend and colleague, John Richard Trabalka, Ph.D., 71, of Oak Ridge, Tennessee, passed away on 23 February 2014 from complications of multiple myeloma. All who knew John would agree that he was a powerful intellect and a wonderful human being. John had more than 43 y of professional experience investigating the biogeochemistry and effects of environmental pollutants, particularly radionuclides and xenobiotic organic chemicals. He earned a B.S. in physics and an M.S., M.P.H., and Ph.D. in Environmental Health Sciences from the University of Michigan. The first 31 y of John’s career were spent at Oak Ridge National Laboratory in the Environmental Sciences and Chemical Technology Divisions. In his last year at ORNL, he served as technical assistant to the Associate Laboratory Director for Biological and Environmental Sciences. From 2004 until the time of his death, he joined us at the Oak Ridge Center for Risk Analysis, Inc. (formerly SENES Oak Ridge, Inc.). His scientific contributions and interests ranged from protection of human health and the environment at contaminated sites to anthropogenic effects of carbon on global climate. His earliest research was on radiation effects on fish populations. His investigations of the transuranic elements included long-term laboratory, field, and microcosm experiments using Pu as a tracer for environmental plutonium. He received a citation for his service as the editor and a major contributor to the 1985 state-of-the-art report on Atmospheric Carbon Dioxide and the Global Carbon Cycle for the U.S. Department of Energy. In the late