The sources of quantitative and qualitative uncertainties of the exposure of a consumer to a pesticide residue are identified. The contribution of quantifiable uncertainties of input parameters of deterministic model to the combined uncertainty of the estimated exposure is shown with detailed calculation using the pesticide residue content of food consumed during two days. The daily intakes of bifenthrin residues calculated for the 60 kg bodyweight of the reporting person are 0.00257 mg/kgbw and 0.00281 mg/kgbw for day 1 and day 2, respectively with 27-28% combined uncertainty. The major contributors were fruits and whole meal bread. The contribution of the individual steps to the combined uncertainty depends on the particular food item. In general, the variability of recipes, estimation of the mass of consumed food, sampling, processing of raw commodities and analysis of pesticide residues influenced most, in decreasing order, the combined uncertainty of the estimated daily exposure.
Keywords: Pesticide residue; combined uncertainty; exposure assessment; food consumption; relative standard uncertainty; variability.