Evaluation of the Variation in Calculated Human Exposure to Soil Contaminants Using Seven Different European Models

ABSTRACT

Calculations using seven European exposure models were performed for 20 different exposure scenarios. The objective of this article is to understand the variation in the resulting calculated human exposures due to soil contamination. To this purpose, the variation in calculated exposures has been compared with the variation in calculated concentrations in contact media and in the soil compartments and with the variation in the input parameters. This led to the conclusion that most of the variation in Exposure through soil ingestion is explained by differences in the input parameter average daily soil intake. When model-specific input parameters are used the variation in Exposure through crop consumption is explained by differences in the product of total consumption rate and fraction of total consumption rate that is home-grown. When standardized input parameters are used, this variation is comparable with the variation in Concentration in root vegetables and in Concentration in leafy vegetables. The variation in Exposure through indoor air inhalation is comparable with the variation in Concentration in indoor air. This suggests that the parameters that control the variation in Concentration in the indoor air, that is, surface and volume of the building and, to a lesser extent, ventilation frequency of the building, also control the variation in Exposure through indoor air inhalation.

Key words:

• human exposure models
• soil ingestion
• plant consumption
• indoor air inhalation
• soil contamination

ACKNOWLEDGMENTS

This investigation was performed for the account of the Dutch Ministry of Housing, Spatial Planning and the Environment (VROM) of the Netherlands, Directorate General for the Environment (DGM), Directorate of Soil, Water and Rural Areas (BWL), which is appreciated. Besides, the author sincerely appreciates the efforts and many useful comments of the participants of the human exposure comparison study, that is, Ms.dr. Francesca Quercia (the National Environmental Protection Agency (ANPA), Italy), Ms.dr. Roseline Bonnart (the National Institute for Industrial Environment and Risks (INERIS), France), Ms. Christa Cornelis (the Flemish Institute of Technology and Development (VITO), Flanders, Belgium), Ms.dr. Naomi Earl (University of Nottingham, Land Quality Management (LQM; present affiliation Atkins), United Kingdom), Dr. Paul Nathanail (University of Nottingham, Land Quality Management (LQM), United Kingdom), Mr. Mark Elert (Kemakta Konsult AB, Sweden), Mr. Piet Otte (the National Institute of Public Health and the Environment (RIVM), the Netherlands), and Ms. Dorte Rasmussen (DHI Water and Environment and Danish Toxicological Centre, Denmark).

Notes

¹To derive these RDs for a specific scenario, each of the seven individual model results is divided by the median value of these seven individual model results. The resulting index represents a “factor x higher,” or “a factor y lower” than the median value of that specific scenario, for each output. The index enables mutual comparison of variation between calculated outputs in different scenarios, although absolute values of these outputs might be of a different order of magnitude

²The following (arbitrary) categorization has been used:

• Limited variation: The majority of the outputs is within a factor of 5 higher and a factor of 5 lower than the scenario medians.

• Substantial variation: Themajorityoftheoutputsisinbetweenafactorof 10 higheranda factorof 10 lowerthanthescenariomedians: thereisa “substantialvariation” inthe calculated human exposures.

• Large variation: The majority of the outputs is in between a factor of 100 higher and a factor of 100 lower than the scenario medians

* Expressed as a factor higher than the scenario medians (95-percentile) and a factor lower than the scenario medians (5-percentile)

^# The following (arbitrary) categorization for variation in calculated outputs has been used: