Risk-based screening levels (RBSLs) of some pollutants for residential adults were derived with risk assessment tools developed by United States Environmental Protection Agency (USEPA), American Society for Testing and Materials (ASTM), and Korea Ministry of Environment (KMOE) and compared each other. To make the comparison simple, ingestion of soil, dermal contact with soil, outdoor inhalation of vapors, indoor inhalation of vapors, and inhalation of soil particulates were chosen as exposure pathways. The results showed that the derived RBSLs varied for every exposure pathway. For direct exposure pathways (i.e., ingestion of soil and dermal contact with soil), the derived RBSLs varied mainly due to the different default values for exposure factors and toxicity data. When identical default values for the parameters were used, the same RBSLs could be derived regardless of the assessment tools used. For inhalation of vapors and inhalation of soil particulates, however, different analysis methods for cross-media transfer rates were used and different assumptions were established for each tool, identical RBSLs could not be obtained even if the same default values for exposure factors were used. Especially for inhalation of soil particulates pathway, screening level derived using KMOE approach (most conservative) was approximately 5000~10000 times lower than the screening level derived using ASTM approach (least conservative). Our results suggest that, when deriving RBSL using a specific tool, it is a prerequisite to technically review the analysis methods for cross-media transfer rates as well as to understand how the assessment tool derives the default values for exposure factors.

Keywords: Risk assessment;Risk-based screening level;Default values for exposure factors;Analysis of the crossmedia transfer rates of contaminants;