Effect of variable consumption habits in the Nordic populations on ECOSYS model predictions of ingestion dose

The two European standard decision support systems, ARGOS and RODOS, have in recent years become increasingly integrated in the Nordic preparedness against nuclear and radiological accidents and incidents. In the event of an emergency, decision making will rest heavily on the reliability of these tools. The ECOSYS model is the ingestion dose module in both decision support systems. This module is highly sensitive to variation in a number of input parameters, food production patterns, diets and environmental transfer data. With regard to for instance consumption habits, the ECOSYS default values, based on data from Southern Germany, have shown to be inadequate for Nordic conditions. We have thus collected recent data describing the human diets for four different age groups in each of the Nordic countries. Also the fractions of the consumed food items that have national origin and the animal feeding regimes in each of the Nordic countries have been examined. For a particular contamination scenario of atmospheric deposition of caesium-137, country specific data regarding consumption habits were used for dose calculations. Resulting 'country specific' doses were then compared among the participating countries and with the doses calculated using the default values of the parameters.The collected data for diets demonstrated that the average consumption of milk varied by a factor of 4-5 among the Nordic countries, and consumption of leafy vegetables varied by a factor of almost 4. Calculated ingestion doses based on country specific data for diets, with all other parameters being default values, varied by a factor of 1.8 among the countries. When also the import fractions were taken into account the calculated doses varied by a factor of 2. Due to the differences in the climate among the Nordic countries, and between these countries and Southern Germany, there were also very significant differences in the production regimes of some food items. In countries in the northernmost areas used for grain crops, the crops are entirely spring grain crops, whereas in Denmark and Germany, winter crops are dominant. This gives large deviations in growth periods and development stages of the crops, particularly in the spring. This implies that first year doses from the same contaminant plume can be very different in different Nordic countries. Thus we conclude that the food habits of the population in the Nordic countries affected the calculated ingestion dose significantly. Also it is important to ascertain the use of state-of-the-art data for the more generic model parameters and to test the effect of other parameters to improve the decision support system used in the Nordic countries.