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Toxicity to microorganisms

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Description of key information

PFPA (degradation product) CAS# 422-64-0: activated sludge 3-hour EC50 (respiration), >10,000 mg/L; 3-hour NOEC, 10,000 mg/L (OECD TG209).

Key value for chemical safety assessment

Additional information

Toxicity of CAS# 756-13-8 to microorganisms was addressed in two studies using either the substance itself or perfluoropropionic acid (PFPA, CAS# 422-64-0).  CAS# 756-13-8 hydrolyzes completely with a half-life < 2.5 minutes when forced into contact with water to PFPA and a volatile hydrofluorocarbon (heptafluoropropane).  Therefore, toxicity tests based on PFPA concentrations provide a more realistic appraisal of the effects of the test substance in the environment.

 

All studies were performed in accord with established test guidelines and were in compliance with OECD GLP standards.  In the key study, PFPA was used as the test substance.  The 3-hour EC50 (respiration) to activated sludge microorganisms was >10,000 mg/L PFPA, and the 3-hour NOEC was 10,000 mg/L PFPA (the highest concentration tested).  In the supporting study, the 30-minute EC50 (respiration) of CAS# 756-13-8 to activated sludge microorganisms was > 100 mg/L, and the 30-minute NOEC was 100 mg/L (only concentration tested).  With the assumption of no loss to volatilization, the 3-hour EC50 in the key study is equivalent to 19,300 mg/L of CAS# 756-13-8, an amount well in excess of the substance solubility limit.  Based on the results of the key study, both CAS# 756-13-8 and PFPA 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 (4 Apr.1984), and was in compliance with OECD GLP standard C(97)186/Final (1997). The key study is classified as acceptable and satisfies the guideline requirements for test method OECD TG209 (activated sludge, respiration inhibition test).  The supporting study was performed in accord with guidelines OECD TG209 (4 Apr.1984) and EEC directive 67/548, amendment 87/302, part C, publication L133 (30 May 1988), and was in compliance with OECD GLP standards then in effect.  The supporting study is classified as acceptable and satisfies the guideline requirements for test method OECD TG209, with the limitations of water-insolubility of the test substance and the unknown degree of hydrolysis of the notified substance to PFPA during the study period.