Extrapolating Ecological Risks of Ionizing Radiation from Individuals to Populations to Ecosystems

Abstract

Approaches for protecting ecosystems from ionizing radiation are quite different from those used for protecting ecosystems from adverse effects of toxic chemicals. The methods used for chemicals are conceptually similar to those used to assess risks of chemicals to human health in that they focus on the protection of the most sensitive or most highly exposed individuals. The assumption is that if sensitive or maximally exposed species and life stages are protected. then ecosystems will be protected. Radiological protection standards. on the other hand, are explicitly premised on the assumption that organisms, populations and ecosystems all possess compensatory capabilities to allow them to survive in the face of unpredictable natural variation in their environments. These capabilities are assumed to persist in the face of at least some exposure to ionizing radiation. The prevailing approach to radiological protection was developed more than 30 years ago at a time when the terms risk assessment and risk management were rarely used. The expert review approach used to derive radiological protection standards is widely perceived to be inconsistent with the open participatory approach that prevails today for the regulation of toxic chemicals. The available data for environmental radionuclides vastly exceeds that available for any chemical. Therefore , given an understanding of dose-response relationships for radiation effects and exposures for individual organisms , it should be possible to develop methods for quantifying effects of radiation on populations. A tiered assessment scheme as well as available population models that could beused for the ecological risk assessment of radionuclides is presented.