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Short-term toxicity to fish

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Description of key information

PFPA (degradation product) CAS# 422-64-0: fathead minnow (Pimephales promelas) 96-hr LC50 = >1070 mg/L.

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The substance tested in these studies, perfluoropropionic acid (PFPA, CAS# 422-64-0), is the hydrolysis product of CAS# 756-13-8.  Although CAS# 756-13-8 is immiscible in water, it hydrolyzes completely when forced into contact with water to PFPA and a volatile hydrofluorocarbon (heptafluoropropane), with a half-life of <2.5 minutes.  Therefore, short term toxicity testing of PFPA provides a more realistic appraisal of the effects of CAS# 756-13-8. The short term toxicity of PFPA (CAS# 422-64-0) to fish was examined in two studies performed in accord with accepted guidelines and compliant with OECD principles of Good Laboratory Practice.  In the key study, the fathead minnow (Pimephales promelas) 96-hour LC50 was found to be > 1070 mg/L (mean measured concentration) based on no observed mortality and no observed sublethal effects at the highest concentration tested.  In the supporting study, the test substance 96-hour NOEC for orange-red killifsh (Oryzias latipes) was 333 mg/L (nominal concentration) based on mortality, with 100% mortality observed at 500 mg/L.  Since PFPA (CAS# 422-64-0) is not subject to hydrolysis, photolysis volatilization or biodegradation over the timeframe of the test, the nominal concentration is an adequate measure of exposure.  Thus, the test substance is classified as not acutely toxic to fish in accordance with the classification system of the Globally Harmonized System (GHS).


The key study was performed in accord with OECD TG203 (17July1992) and U.S. EPA guideline OPPTS 850.1075, EPA712-C-96-118 (public draft published April 1996), and in compliance with OECD regulation C(97) 186/Final (1997).  The key study is classified as acceptable and satisfies the guideline requirements for test method OECD203 (Fish, Acute Toxicity Test).  The supporting study was conducted in accord with method JIS K 0102-1998-71 (Testing methods for industrial waste water, Acute toxicity test with fish, adoption date not reported), and in compliance with OECD principles of Good Laboratory Practice (26 November, 1997).   The toxicity study was performed as a limit-setting test prior to a bioconcentration study, and the study report was an addendum to the bioconcentration report.  As an English translation of this method is not available and the study report lacks sufficient detail to make a determination, compliance with accepted test methods cannot be assessed.  Also, test medium pH was not controlled and reached a level of 2.9 during the study.  This pH is not recommended in current OECD test methods and may have played a role in toxicity at the highest exposure level.  In addition, exposure in this study was based on nominal concentration whereas exposure in the Pimephales study was based, as is preferable, on measured concentrations.  While the result of the supporting study supports the key study, the reliability of the supporting study is limited.