Toxicological Risk Assessment of Soil Contaminants

International bodies such as the World Health Organization (WHO) and national governmental agencies like the U.S. Environmental Protection Agency (EPA) use the same basic concept to derive acceptable daily intake (ADI) and reference dose (RfD). This customary concept is used in toxicological risk assessment of soil contaminants in Germany. It is used in the following ways: with extension to new substances not yet assessed by, for example, WHO or EPA; with reevaluations for substances with new toxicologically relevant input data; with explicitly stated absorption rates used to calculate internal exposure; its results are presented differently and are better suited to multipathway situations of exposure such as in contaminated sites; and with extensions in assessment by assigning quality criteria to unit risk quantifications to carcinogenic substances. The respective derived doses are called TRD (tolerable resorbiente dosis—tolerable absorbed dose) values, that is, reference values equivalent to a no observed adverse effect level in sensitive human subpopulations. TRD values are proposed for approximately 85 soil contaminants and 20 warfare substances with high priority in Germany up to now. The article outlines some of the specific problems in deriving TRD values and gives examples for comparison with ADI (WHO) or RfD (EPA) values.