Insight into the Variation in Calculated Human Exposure to Soil Contaminants Using Seven Different European Models

In order to get insight into the variation in calculated human exposure, the outputs of 7 European exposure models have been compared. Twenty scenarios, differing with respect to land use, soil type, and contaminant, formed the basis for calculating human exposure to soil contaminants. All calculations were performed twice: Once with a standardized set of parameters for all models and once with the own default parameters. This led to the conclusion that the variation in calculated total exposure (combining all exposure pathways) is large (the majority of the outputs is in between a factor of 100 higher and a factor of 100 lower than the scenario medians). In addition, variation for exposure due to indoor air inhalation is also large. The variation for exposure due to crop consumption is substantial (the majority of the outputs is in between a factor of 10 higher and a factor of 10 lower than the scenario medians) and limited for exposure due to soil ingestion (limited = the majority of the outputs is within a factor of 5 higher and a factor of 5 lower than the scenario medians). The variation in calculated exposure increases when a contaminant is more mobile and, particularly, more volatile. The variation due to selection of input parameters does only yield an additional variation over the variation due to model algorithms for exposure due to soil ingestion and, to a lesser extent, for exposure due to crop consumption. The variation in calculated exposure is not dependent on the soil type and hardly dependent (only for exposure due to soil ingestion) on land use. The choice of model is a very significant factor for the absolute value of calculated exposure. For the promotion of uniformity it was recommended to construct a toolbox for the calculation of human exposure, for general use, including standardized tools and flexible tools, the latter to account for region-specific or country-specific (geographical, ethnological, and cultural) elements and national policy decisions.