RIFM fragrance ingredient safety assessment, 2-mercaptopropionic acid, CAS Registry Number 79-42-5.

The existing information supports the use of this material as described in this safety assessment. 2-Mercaptopropionic acid was evaluated for genotoxicity, repeated dose toxicity, reproductive toxicity, local respiratory toxicity, phototoxicity/photoallergenicity, skin sensitization, and environmental safety. Data show that 2-mercaptopropionic acid is not genotoxic. The repeated dose, reproductive, and local respiratory toxicity endpoints were evaluated using the Threshold of Toxicological Concern (TTC) for a Cramer Class I material, and the exposure to 2-mercaptopropionic acid is below the TTC (0.03 mg/kg/day, 0.03 mg/kg/day, and 1.4 mg/day, respectively). The skin sensitization endpoint was completed using the Dermal Sensitization Threshold (DST) for reactive materials (64 μg/cm); exposure is below the DST. The phototoxicity/photoallergenicity endpoints were evaluated based on ultraviolet (UV) spectra; 2-mercaptopropionic acid is not expected to be phototoxic/photoallergenic. For the hazard assessment based on the screening data, 2-mercaptopropionic acid is not persistent, bioaccumulative, and toxic (PBT) as per the International Fragrance Association (IFRA) Environmental Standards. For the risk assessment, 2-mercaptopropionic acid was not able to be risk screened as there were no reported volumes of use for either North America or Europe in the 2015 IFRA Survey.