In environmental risk assessments of nuclear facilities (power plants and processing facilities) and in the uranium industry radionuclides (radioactive parameters) need to be considered alongside conventional chemical stressors, but they do not always fit comfortably within the same assessment framework. Whereas metals, nutrients, and organic contaminants are typically evaluated using concentration-based benchmarks and toxicity thresholds, radionuclides are evaluated through a radiological dose which requires additional consideration of radioactive decay, daughter products, exposure geometry, bioaccumulation, and dosimetry.

This presentation will introduce key differences in how radionuclides are assessed in environmental risk assessment, with a focus on practical challenges encountered when integrating radionuclides into conventional ecological and human health risk assessment approaches based on CanNorth’s extensive experience working on projects in the nuclear industry. Topics will include the importance of activity-based units, dose conversion factors, identification of relevant exposure pathways, treatment of background radiation, radionuclide-specific behaviour in environmental media. The discussion will also highlight why a simple “screening value exceedance” approach may be insufficient for radionuclides and how regulatory expectations, dose-based criteria, and site-specific exposure assumptions can influence risk conclusions.

This talk will provide a practical overview for risk assessors who may be familiar with conventional contaminants but less comfortable with radionuclides. The goal is to demystify the evaluation of radionuclides and demonstrate why they should not be treated as just another chemical stressor, but instead as contaminants requiring a distinct and carefully structured assessment approach.