ICRP Publication 136: Dose Coefficients for Non-human Biota Environmentally Exposed to Radiation.

Abstract ­: The diversity of non-human biota is a specific challenge when developing and applying dosimetric models for assessing exposures of flora and fauna from radioactive sources in the environment. Dosimetric models, adopted in Publication 108, provide dose coefficients (DCs) for a group of reference entities [Reference Animals and Plants (RAPs)]. The DCs can be used to evaluate doses and dose rates, and to compare the latter with derived consideration reference levels (DCRLs), which are bands of dose rate where some sort of detrimental effect in a particular RAP may be expected to occur following chronic, long-term radiation exposure, as outlined in Publication 124. These dosimetric models pragmatically assume simple body shapes with uniform composition and density, homogeneous internal contamination, limited sets of idealised sources of external exposure to ionising radiation for aquatic and terrestrial animals and plants, and truncated radioactive decay chains. This pragmatic methodology is further developed and systematically extended in this publication, which supersedes the DC values of Publication 108. Significant methodological changes since Publication 108 include: implementation of a new approach for external exposure of terrestrial animals with an extended set of environmental radioactive sources in soil and in air; considering an extended range of organisms and locations in contaminated terrain; transition to the contemporary radionuclide database of Publication 107; assessment-specific consideration of the contribution of radioactive progeny to DCs of parent radionuclides; and use of generalised allometric relationships in the estimation of biokinetic or metabolic parameter values. These methodological developments result in changes to previously published tables of DCs for RAPs, and revised values are provided in this publication. This publication is complemented by a new software tool, called 'BiotaDC', which enables the calculation of DCs for internal and external exposures of organisms with user-defined masses, shapes, and locations in the environment and for all radionuclides in Publication 107.

Environmental risks of radioactive discharges from a low-level radioactive waste disposal site at Dessel, Belgium.

The potential radiological impact of releases from a low-level radioactive waste (Category A waste) repository in Dessel, Belgium on the local fauna and flora was assessed under a reference scenario for gradual leaching. The potential impact situations for terrestrial and aquatic fauna and flora considered in this study were soil contamination due to irrigation with contaminated groundwater from a well at 70 m from the repository, contamination of the local wetlands receiving the highest radionuclide flux after migration through the aquifer and contamination of the local river receiving the highest radionuclide flux after migration through the aquifer. In addition, an exploratory study was carried out for biota residing in the groundwater. All impact assessments were performed using the Environmental Risk from Ionising Contaminants: Assessment and Management (ERICA) tool. For all scenarios considered, absorbed dose rates to biota were found to be well below the ERICA 10 µGy h-1 screening value. The highest dose rates were observed for the scenario where soil was irrigated with groundwater from the vicinity of the repository. For biota residing in the groundwater well, a few dose rates were slightly above the screening level but significantly below the dose rates at which the smallest effects are observed for those relevant species or groups of species. Given the conservative nature of the assessment, it can be concluded that manmade radionuclides deposited into the environment by the near surface disposal of category A waste at Dessel do not have a significant radiological impact to wildlife.

Lung cancer mortality at a UK tin smelter.

BACKGROUND: An earlier study of mortality among male former employees at a tin smelter in Humberside, UK, had identified excess mortality from lung cancer, which appeared to be associated with occupational exposure. AIMS: The aim of the present study was to investigate the relationship between lung cancer mortality and quantitative measures of exposure. METHODS: Using available records of occupational hygiene measurements, we established exposure matrices for arsenic, cadmium, lead, antimony and polonium-210 ((210)Po), covering the main process areas of the smelter. We established work histories from personnel record cards for the previously defined cohort of 1462 male employees. Three different methods of extrapolation were used to assess exposures prior to 1972, when no measurement results were available. Lung cancer mortality was examined in relation to cumulative inhalation exposure by Poisson regression analysis. RESULTS: No significant associations could be found between lung cancer mortality and simple cumulative exposure to any of the substances studied. When cumulative exposures were weighted according to time since exposure and attained age, significant associations were found between lung cancer mortality and exposures to arsenic, lead and antimony. CONCLUSIONS: The excess of lung cancer mortality in the cohort can most plausibly be explained if arsenic is the principal occupational carcinogen (for which the excess relative risk diminishes with time since exposure and attained age) and if there is a contribution to excess mortality from an enhanced prevalence of smoking within the cohort. The implications of the dose-response for arsenic exposure for risk estimation merit further consideration.