RIFM fragrance ingredient safety assessment, 2,2-dimethyl-3-methyl-3-butenyl propanoate, CAS Registry Number 104468-21-5.

The existing information supports the use of this material as described in this safety assessment. 2,2-Dimethyl-3-methyl-3-butenyl propanoate was evaluated for genotoxicity, repeated dose toxicity, reproductive toxicity, local respiratory toxicity, phototoxicity/photoallergenicity, skin sensitization, and environmental safety. Data from read-across analog rhodinyl formate (CAS # 141-09-3) show that 2,2-dimethyl-3-methyl-3-butenyl propanoate is not expected to be 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 2,2-dimethyl-3-methyl-3-butenyl propanoate 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 non-reactive materials (900 μg/cm); exposure is below the DST. The phototoxicity/photoallergenicity endpoints were evaluated based on ultraviolet (UV) spectra; 2,2-dimethyl-3-methyl-3-butenyl propanoate is not expected to be phototoxic/photoallergenic. The environmental endpoints were evaluated; 2,2-dimethyl-3-methyl-3-butenyl propanoate was found not to be persistent, bioaccumulative, and toxic (PBT) as per the International Fragrance Association (IFRA) Environmental Standards, and its risk quotients, based on its current volume of use in Europe and North America (i.e., Predicted Environmental Concentration/Predicted No Effect Concentration [PEC/PNEC]), are <1.