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

Endpoint summary

Additional information

CAS# 297730-93-9 is extremely insoluble in water (21.3 ppb) and extremely volatile from aqueous systems (Henry's Law constant 4.7 x 10⁷ Pa∙m³/mol). Nevertheless, two aquatic toxicity studies were performed with CAS# 297730-93-9 under flow-through conditions to attempt to maintain the test substance in solution. A 96-hour LC50 >10 mg/L and a 48-hour LC50 >50 mg/L were measured. Both studies were done preliminary to 56-day bioconcentration studies and were conducted under guideline requirements for a JIS K 0102-1998-71 assay (Japanese guideline). The 96-hour assay used nominal concentrations. As this study was preliminary to a lengthy and expensive bioconcentration study, it must be assumed that adequate precautions were taken to keep the test substance in solution. The test solution also contained 2-methoxyethanol (ca. 1000 mg/L) and HCO-20 (200 mg/L) as dispersants, both of which are in excess of current OECD guidelines for solubility aids in aquatic testing. However, this use would be expected to increase bioavailability and apparent toxicity of the test substance, and as the study demonstrated no toxicity at the highest concentration tested the study result is reliable with restrictions. The 48-hour assay is not adequate on its face due simply to insufficient study duration. As noted, 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 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 subjects of existing risk assessments. Numerous studies of PFBA aquatic toxicity have been conducted. Results by taxonomic level are summarized in taxon-specific sections. It may be seen that PFBA is not acutely toxic to aquatic organisms according to GHS criteria. The most sensitive species is the aquatic invertebrate Hyalella azteca, with a 96-hour LC50 of 971 mg/L. All other taxonomic levels and species had endpoints well in excess of 1000 mg/L. 

 

In addition to toxicity studies with PFBA to purely aquatic organisms, a 96-hour LC50 > 10,000 mg/L was measured for Chironomus tentans, a sediment organism which spends a portion of its lifecycle above the sediment-water interface.

 

The key studies and most supporting studies were performed in accordance with accepted testing guidelines and GLP criteria, and have at least some analytical data available to confirm test substance concentration. Most studies used the potassium salt of PFBA, which is equivalent to neutralization of stock solution with potassium hydroxide before dilution and assembly of test chambers. Further details are available by section.