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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

CAS# 297730-93-9: activated sludge, 30 minute EC50 (respiration), >100 mg/L; 30 minute NOEC, 100 mg/L (OECD TG209).
PFBA: activated sludge, 3-hour EC50 (respiration), >1000 mg/L; 3-hour NOEC, 1000 mg/L (read-across values from iso-PFBA OECD TG209)

Key value for chemical safety assessment

Additional information

Toxicity of CAS# 297730-93-9 to microorganisms was addressed in one study. Toxicity ofperfluorobutyric acid(PFBA) was addressed in two studies asperfluorobutyric acid(PFBA, CAS# 375-22-4) or iso-perfluorobutyric acid (iso-PFBA, CAS# 335-10-4).  PFBA is one of the persistent degradation products of CAS# 297730-93-9 for which laboratory data is available and summarized in IUCLID.  Therefore, toxicity tests based on PFBA concentrations will also be addressed in the effects of CAS# 297730-93-9 in the environment.


Three tests were performed relevant to this compound. In the key study, CAS# 297730-93-9 was used as the test substance.  The 30 minute EC50 (respiration) to activated sludge microorganisms was >100 mg/L, and the 30 minute NOEC was 100 mg/L.  This study was performed in accord with established test guidelines and was in compliance with OECD GLP standards. In the supporting study, PFBA was used as the test substance. The 6.63-minute EC50 (respiration) was determined to be 1000 mg/L. However, this study is considered unreliable due to its unsuitably short exposure duration time. As a result, iso-PFBA was considered as a read-across value for PFBA for its toxicity to microorganisms since it is a chemical analogue and has distinct structural similarity to PFBA. In the weight of evidence study, the 3-hour EC50 (respiration) of iso-PFBA to activated sludge microorganisms was >1000 mg/L, and the 3-hour NOEC was 1000 mg/L.  Based on the results of the key study and weight of evidence, both CAS# 297730-93-9 and PFBA are classified as not acutely toxic to microorganisms in accordance with the classification system of the Globally Harmonized System (GHS).


The key study was performed in accord with OECD TG209 as well asDirective 87/302/EEC, C L133and was in compliance with GLP standards; therefore, the key study is classified as acceptable and reliable with restrictions with the limitations of water-insolubility of CAS# 297730-93-9.  The supporting study on PFBA is classified as unreliable. The weight of evidence study on iso-PFBA was performed in accord with guidelines OECD TG209 and was in compliance with OECD GLP standards and is used as a read-across value for PFBA.