Radiation Effectiveness Factors for Use in Calculating Probability of Causation of Radiogenic Cancers

Abstract

This paper presents so-called radiation effectiveness factors that are intended to represent the biological effectiveness of different radiation types, relative to high-energy Co gamma rays, for the purpose of estimating cancer risks and probability of causation of radiogenic cancers in identified individuals. Radiation effectiveness factors are expressed as subjective probability distributions to represent uncertainty that arises from uncertainties in estimates of relative biological effectiveness obtained from radiobiological studies of stochastic endpoints, limited data on biological effectiveness obtained from human epidemiological studies, and other judgments involved in evaluating the applicability of available information to induction of cancers in humans. Primarily on the basis of reviews and evaluations of available data by experts, probability distributions of radiation effectiveness factors are developed for the following radiation types: neutrons of energy less than 10 keV, 10-100 keV, 0.1-2 MeV (including fission neutrons), 2-20 MeV, and greater than 20 MeV; alpha particles of any energy emitted by radionuclides; photons of energy 30-250 keV and less than 30 keV; and electrons of energy less than 15 keV. Photons of energy greater than 250 keV and electrons of energy greater than 15 keV are assumed to have the same biological effectiveness as reference Co gamma rays and are assigned a radiation effectiveness factor of unity, without uncertainty. For neutrons and alpha particles, separate probability distributions of radiation effectiveness factors are developed for solid tumors and leukemias, and small corrections to represent an inverse dose-rate effect are applied to those distributions in cases of chronic exposure. A radiation effectiveness factor different from unity for 15-60 keV electrons is discussed but is not adopted due to a lack of relevant radiobiological data. Radiation effectiveness factors presented in this paper are incorporated in the Interactive RadioEpidemiological Program and were developed for use by The National Institute for Occupational Safety and Health and U.S. Department of Labor in evaluating claims for compensation for radiogenic cancers by workers at U.S. Department of Energy facilities.

Considerations on Estimating Upper Bounds of Neutron Doses Equivalents to Military Participants at Atmospheric Nuclear Tests

“…By applying a dose and dose-rate effectiveness factor (DDREF) for photons of 2 (ICRP, 1991) (Kocher et al, 2002) by assuming a DDREF for photons of 2 (ICRP, l99l), incorporates an assumption that there is no uncertainty in DDREF. However, DDREF also is uncertain.…”

“…When a cancer type of concem in a claim was included in the CIRRPC IREP accounts for uncertainties in the biological effectiveness of different radiation types relative to high-energy (> 250 keV) photons by incorporating probability distributions of REFs developed by Kocher et al (2002), including the probability distributions of REF for fission neutrons discussed in Section 3. When a neutron equivalent dose and the associated energy range of neutrons are entered into IREP, the equivalent dose is divided by the wn that IREP assumes was used to estimate equivalent dose to obtain the corresponding absorbed dose.…”

“…The NRC committee's finding was based mainly on an evaluation of data on the relative biological effectiveness (RBE) of fission neutrons and their uncertainties by Kocher et al (2002); see also Kocher et al (2005). On the basis of estimates of RBE in studies of life-shortening, which was due primarily to cancers, and induction of specific cancers in mice, Kocher et al…”

“…Recommended increases in the biological effectiveness of neutrons were based mainly on estimates of RBE at low doses in studies of various stochastic endpoints that were reviewed by expert groups (ICRU, 1986;NCRP, 1990), including RBEs that were used by Kocher et al (2002) to develop probability distributions of REFs.…”

Revue de l’état des connaissances des effets du tritium sur la santé et l’environnement au Canada – un outil pour orienter la surveillance réglementaire

“…De nombreuses études expérimentales ont été menées afin de caractériser la valeur de l'efficacité biologique relative du tritium (EBR) (Straume et (Kocher et al, 2005).…”