Skin sensitization risk assessment: Considering available data for weight of evidence assessments.

Basketter and Safford discuss estimating acceptable exposure levels based on data from human testing or from the Local Lymph Node Assay (LLNA), which is clearly the test that should be conducted for new chemicals or chemical registrations. However, LLNA data are not available for many existing chemicals which may nonetheless need to be evaluated under time and budgetary circumstances where new testing may not be feasible, e.g., cases of product adulteration, emergency release scenarios, or first pass screening for chemical alternatives assessment. In the absence of test data, Safford et al. (2015) proposed a dermal sensitization threshold (DST) of 64 μg/cm for chemical sensitizers not identified as high potency agents. But how should one address cases where data other than LLNA results for the chemical of interest are already available?