Evaluating the radiological impact of uranium emissions in Port Hope, Ontario—A comparison of monitoring and modelling results

During 1988 and 1989, an environmental monitoring study was conducted to assess the possible health impact of airborne emissions from a Canadian uranium processing facility. Airborne U dust was collected using high-volume air samplers located within 2km of the facility. Weekly concentrations of U in air varied from the detection limit of 0.06 ng m−3 to 75.7ng m−3, with a geometric mean of 1.05ng m−3. Decreases in concentration during the summer facility slowdown period indicated that the observed levels of airborne U resulted primarily from processing operations, and not from the resuspension of previously emitted material. The committed inhalation dose to the nearest receptor from 1 year of facility operation was estimated to be 0.014 mSv. This was well below ICRP guidelines, and represented a small fraction of normal background radiation. No health effects would be expected at these levels. Results of the study were compared with the predictions of a longterm Gaussian dispersion model based on a hindcast approach to derive the best-fit emission rates. Predicted concentrations were generally within a factor of 2–3 of field observations. Discrepancies were due to inherent limitations of the model, uncertainties in the source emission characteristics, and variations between the long-term meteorological frequency distributions based on remote and local data.