Uncertainty in predictions of fallout radionuclides in foods and of subsequent ingestion.

Uncertainty in predictions from the PATHWAY food-chain model was estimated using Monte Carlo simulation. Uncertainty estimates, measured by the geometric standard deviation (GSD), were obtained for median values of time-integrated concentrations of 131I, 136Cs, and 137Cs in foods and for the corresponding time-integrated intakes resulting from ingestion of all foods. The GSDs associated with a given food for the two short-lived radionuclides, 131I and 136Cs, were not significantly different, but they differed from the GSDs for the longer-lived radionuclide. The GSDs for integrated concentrations of radionuclides in milk varied with the time of year fallout was deposited, but uncertainty for nondairy products was relatively independent of the date of fallout deposition. The estimated GSDs were applied to other radionuclides of interest based on physical half-life and ranged from 1.7 to 2.7 for time-integrated intake across all foods for radionuclides with physical half-lives less than 30 d, from 1.8 to 2.3 for half-lives ranging from 30 to 500 d, and from 1.9 to 2.1 when half-lives were greater than 500 d.