3-ethoxy-1,1,1,2,3,4,4,5,5,6,6,6-dodecafluoro-2-(trifluoromethyl)-hexane

Endpoint summary

Additional information

No biodegradation of CAS# 297730-93-9 (HFE 7500) was observed under test conditions in an OECD TG301D assay.  Biodegradation was also studied in two OECD 308 tests conducted under aerobic and anaerobic conditions. Both studies were conducted in individual closed VOA vials spiked with HFE 7500 and containing sediment, water and headspace. HFE-7500 was administered to the cultures by applying it onto dried freshwater sediment and then that material dosed to the cultures by blending it with freshwater sediment and lake water. The vials were incubated at 12 deg C. For the aerobic test, intermittent supplementation of oxygen (air) was performed when oxygen levels were measured below 10% in the headspace. For the anaerobic test, sediments and cultures were handled in a glove box under nitrogen, and once closed were removed from the glove box and left sealed until sampling. Perfluorobutanoic acid (PFBA) was measured at trace levels in both the anaerobic and aerobic studies. The half-life (DT50) of HFE-7500 calculated from formation of PFBA was estimated to be between 91 and 224 years in the aerobic sediments and between 189 and 415 years in the anaerobic study. 1H-Heptafluoropropane (HFC-227) was also consistently detected at trace levels in the bioactive cultures of the anaerobic study. In the aerobic study, HFC-227 was occasionally detected but without a clear trend with time and later timepoints were also affected by an increase in limit of quantitation due to the oxygen replenishment procedure. A third potential degradation product, hexafluoropropene, was generally not detected in either study and no other degradation products could be identified via nontargeted analysis that was performed for the aerobic study. 

 

The products of abiotic degradation (see discussion of abiotic degradation / stability) are HF (CAS# 7764-39-3), TFA (CAS# 76-05-1), PFBA, and CO2. HF is an inorganic, mineral acid and is not subject to biodegradation.  A review of available published information indicates that TFA under aerobic conditions is not readily or inherently biodegradable.  A review of available information indicates that perfluorocarboxylic acids under aerobic conditions are not readily or inherently biodegradable. In addition, it has been shown from studies with many other longer chain perfluorinated moieties that perfluorinated acids are oxidatively recalcitrant and resistant to most conventional waste treatment technologies ⁽¹⁾. By a weight of evidence argument, PFBA is not expected to be biodegraded.  Therefore, the degradation products of CAS# 297730-93-9 are expected to be very persistent in aquatic systems.

 

1) C. D. Vecitis, H. Park, J. Cheng, B. T. Mader, M. R. Hoffman. 2009. Treatment technologies for aqueous perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA). Front. Environ. Sci. Engin. China. Vol. 3, No. 2, pp. 129-151.