Proposal of GHS sub-categorization criteria for LLNA: BrdU-ELISA (OECD TG442B).

The Globally Harmonized System of Classification and Labelling of Chemicals (GHS) is a hazard classification and communication system for providing information on the safe handling of chemicals worldwide. While the GHS provides sub-categorization criteria for sensitizers when using the guinea pig maximization test/Buehler test (OECD TG406) and the standard radioisotopic LLNA (OECD TG429), the sub-categorization criteria for LLNA: BrdU-ELISA (OECD TG442B) are not currently provided. In this study, we re-analyzed the existing data of 32 sensitizers classified in the 1A or 1B categories of the GHS, and attempted to determine optimal criteria for GHS sub-categorization using LLNA: BrdU-ELISA. Consequently, the optimal criterion for the GHS sub-categorization was determined to be 6% when using EC1.6, showing the correct outcomes (%) for GHS 1A and GHS 1B category chemicals were 92.3 and 84.2 for all 32 chemicals, respectively. When excluding 2-mercaptobenzothiazole which may cause strain specific low response in this assay system, the correct outcomes (%) for GHS 1A chemicals was 100. Further work would be necessary, but the GHS sub-categorization criteria proposed in this study might be promising when using LLNA: BrdU-ELISA to provide information on the skin sensitization potency category of chemicals.