Understanding the atmospheric transformation mechanism of an emerging fluorinated alcohol (FESOH)

One important pathway for human exposure to per- and polyfluorinated alkyl substances (PFASs) is based on the Earth's atmosphere. Figuring out atmospheric transformation mechanism of PFASs is beneficial for understanding their effects on humans. However, the focus on the molecular-level transformation mechanism of emerging PFASs in the atmosphere still need to be improved. In this work, we used quantum chemistry calculation to study center dot OH-initiated degradation mechanism of a new fluorinated alcohol (C3F7OCHFCF2SCH2CH2OH, abbreviated FESOH) in the presence of oxygen and nitric oxide. Three main conformers of FESOH share the similar initial mechanism that the abstraction reactions of H atom at alpha-C and beta-C atoms are the main pathways (activation free energies of <10 kcal mol(-1) at 298 K), but make different contributions to the whole FESOH degradation. Subsequent transformations starting from initial products at alpha-C atoms will reunite with that at beta-C atoms, and the intermediate (C3F7OCHFCF2S center dot) is produced. After O-2 addition to the intermediate and the following SO2 elimination, the alkyl radical (C3F7OCHFCF2 center dot) can undergo consecutive chain cleavage cycles to form CF3OH finally. The bioaccumulation evaluation shows that FESOH and its transformation products cannot be accumulated in organisms. The work is helpful for knowing the atmospheric fate of FESOH at molecular level and can provide some insight into the transformation of other PFASs in the atmosphere.

Automated summary

One important pathway for human exposure to PFASs is through the Earth's atmosphere. However, the molecular-level transformation mechanism of emerging PFASs in the atmosphere needs further improvement. This study used quantum chemistry calculation to investigate the degradation mechanism of a new fluorinated alcohol (FESOH) in the presence of oxygen and nitric oxide. It was found that the degradation of FESOH involves abstraction reactions of H atom at alpha-C and beta-C atoms, leading to the formation of CF3OH. The bioaccumulation evaluation showed that FESOH and its transformation products cannot be accumulated in organisms.