2,2,3,3,5,5,6,6-octafluoro-4-(trifluoromethyl)morpholine

Short-term toxicity to fish

Description of key information

Perfluoromethylmorpholine (PMM) is not expected to be toxic to fish at the limit of solubility (>0.295 mg/L) by readacross from category members.  When category members were tested, no toxicity was observed to fish in tests conducted with nominal concentrations ranging from 100 to 2700 mg/L.  This categorical result  is considered applicable to PMM.

Additional information

PMM is the most water soluble member of the Perfluorinated Organic Chemicals, C5-C18 category. Because these substances exhibit similarity in their physicochemical properties and toxicological properties in mammals, and because available data indicates that parent molecules are not reactive toward biological molecules and cannot undergo bioactivation by normal enzymatic processes, they can be considered members of a chemical category. Data gaps for ecological toxicity can therefore be addressed by read-across and/or trend analysis between category members. Toxicity studies using P. promelas resulted in 96-hour LC50s >750 mg/L and >2700 mg/L. However, these studies were not reliable enough to stand on their own and were deemed suitable for use in a weight of evidence. Two reliable studies are available for other category members. Perfluoro-N-C1,3-alkyl morpholines (FC-770) was tested using D. rerio. After 96-hours, no toxicity was observed from a water-soluble fraction prepared at 100 mg/L. The mean measured concentration during the test was 0.096 mg/L. Perfluoro-C6,8-furans, pyrans and acyclic ethers (FC-77) was tested using P. promelas. In this case, test chambers were prepared at an initial loading rate of 1000 mg/L. Exposure concentrations were not measured, however, the test material could not be entirely dissolved and was observed in the test chambers throughout the experiment. No toxicity was observed. Other category members had study reports which were less detailed but were suitable for weight of evidence in the aggregate. These category members were not toxic to fish in reliable limit tests with nominal concentrations of 1000 mg/L. Analytically determined concentrations for other category members are not reasonable to use for readacross because of divergent solubilities. Lack of toxicity at the limit of solubility is read across qualitatively to PMM. The solubility of PMM was determined to be 0.295 mg/L in organism-free Daphnia medium controls during the short-term toxicity test. This value is less than the measured PMM solubility in water (0.758 mg/L) and also less than the analytically determined concentrations in medium containing live daphnids. The organism-free medium solubility value is understood to be better representative of PMM solubility in natural waters, and avoids potential impacts on contamination of the analytical result by the action of living organisms. In accord with other category members, 0.295 mg/L is accepted as the basis for estimating the highest possible exposure concentration of PMM in order to define the LC50. Please see IUCLID section 13 for the category justification and a matrix of aquatic toxicity data for members of the Perfluorinated Organic Chemicals C5-C18 category.