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

Short-term toxicity to fish

Description of key information

Key result for CAS# 297730-93-9:
96-h LC50 to Oryzias latipes (method JIS K 0102-1998-71): > 10 mg/L.  Adaptation of further testing requirements proposed due to lack of exposure. 
Key result for PFBA (degradation product):
96-h LC50 (OECD203) to Pimephales promelas: 4149 mg/L.

Additional information

The toxicity of CAS# 297730-93-9 was reported in two studies using Oryzias latipes (high-eyes medaka or orange-red killifish). Both tests were done as preliminary toxicology tests to establish the appropriate exposure levels for Bioconcentration Factor experiments. Both tests were conducted using test guideline JIS K 0102-1998-71 ("Testing methods for industrial waste water, Acute toxicity test with fish"), and made use of both a cosolvent (2-methoxyethanol in both studies) and an ethoxylated castor oil dispersing aid. The key study was conducted for 96-hours with replacement of test medium every 8 to 16 hours, using a limit concentration of 10 mg/L test substance (nominal concentration) plus ca. 1000 mg/L cosolvent and 200 mg/L HCO-20 dispersant. No mortality was observed. This result was corroborated by the supporting study. The supporting study was conducted using the same method and general procedures. However, the duration was 48-hours, test concentrations were 25 and 50 mg/L, the dispersant was HCO-30 at 1000 mg/L, and the cosolvent was present at ca. 3 mL/L. No mortality was observed. Given the limit of no mortality within 96 hours at 10 mg/L, the test substance would be classified as not acutely toxic to fish in accordance with the classification system of the Globally Harmonized System. This chemical will not persist in aquatic systems. We propose to waive any further testing of CAS# 297730-93-9 as not scientifically justified due to exposure considerations. 

 

The key study for CAS# 297730-93-9 was conducted according to a standard method and the overall work (acute toxicity plus bioconcentration) was conducted under GLP criteria. Further, the test substance is of low solubility and is highly volatile. The test was conducted preliminary to a bioconcentration test, and it may be safely assumed that steps were taken to retain the highly volatile test substance. While no analytical data confirming test substance retention is offered, the nominal concentration is therefore adequate for this study. OECD TG203 (Acute fish toxicity) permits the use of adjuvants in the case of difficult or poorly soluble test substances. The cosolvent and the dispersing aid employed in both studies are permitted by OECD TG203, but the amount used in the key study was in excess of limits established within the OECD guideline. The use of cosolvents may have had an effect on bioavailability, however the use would be expected to increase bioavailability and apparent toxicity. Since the test substance did not show toxic effects at the highest level tested, the key study is considered reliable with restrictions.

 

The primary fate of CAS# 297730-93-9 is expected to be photolysis to HF, TFA and PFBA. These acids are highly soluble and are expected to reside ultimately in the aquatic compartment. HF and TFA are the subjects of existing risk assessments. Seven studies of PFBA toxicity to fish conducted using three freshwater species: fathead minnow (Pimephales promelas), bluegill sunfish (Lempomis macrochirus) and rainbow trout (Onchorhynchus mykiss). Two studies were performed in accordance with accepted test guidelines and GLP criteria, had supporting analytical data, and were reliable without restriction. The lowest value for the most sensitive species (Pimephales promelas) was chosen as the key study for PFBA.  A similar study for Lepomis macrochirus had a 96-hour LC50 of 5573 mg/L. Three additional rangefinding studies support this assessment (96-hour LC50s of 3162 – 4815 mg/L). These were generally in accord with test guidelines, but were not GLP and, as rangefinding studies, had a factor of ten difference in concentrations. These nevertheless support the lack of toxicity of PFBA to fish. Two remaining studies were methodologically flawed and are not considered reliable, in one case by inadequate oxygen in the test chambers (96-hour LC50 was >2000 mg/L), in the other because of an inappropriate test method. PFBA is not acutely toxic to fish according to GHS criteria.