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Toxicity to aquatic algae and cyanobacteria

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Description of key information

The 72-h ErC50 is > 114 mg/L and the 72-h NOErC is ca. 13.2 mg/L in Pseudokirchneriella subcapitata (tested as Selenastrum capricornutum) for the structurally similar HFC 365mfc.

Key value for chemical safety assessment

EC50 for freshwater algae:
114 mg/L

Additional information

The assessment of the possible aquatic toxicity of HFC 227ea has been carried out by considering available data on structurally analogue substances.

Experimental data for acute toxicity on Selenastrum capricornutum are available for HFC 245fa (1,1,1,3,3-pentafluoropropane) and HFC 365mfc (1,1,1,2,2 -pentafluorobutane).

The experimental studies were conducted in closed system to avoid substance volatilisation.

In both cases, results indicated a low toxicity to algae and no EC50 could be identified in the studies for HFC 245fa and HFC 365mfc, as low toxicity was observed up to the highest tested concentrations. Overall, a 72 hour-EC50 = 114 mg/l (i.e. the lowest value determined for structural analogs) can be considered a conservative estimation for HFC 227ea.

HFC 245fa:The toxicity of pentafluorobutane to S. capricornutum was studied in a test carried out in accordance to OECD guidelines. A closed system was used in order to limit the substance volatility. The substance was tested at the nominal concentration of 100 mg/l (measured concentrations = 108 mg/l and 128 mg/l at 0 and 72 hours, respectively). Inhibition of 7 % and 22 % were observed at the end of the study for biomass and growth rate, respectively. No EC50 could be determined (72 hour-EC50> 118 mg/l average concentration).

HFC365mfc:The toxicity of pentafluorobutane to S. capricornutum was studied in a test carried out in accordance to OECD guidelines. A closed system was used in order to limit the substance volatility. The algae medium was adapted to the close system conditions by adding a higher concentration of NaHCO3, in order to maintain a sufficient dissolved CO2 concentration. Pentafluorobutane was tested at nominal concentrations of 0, 3, 10, 30, 100 and 300 mg/l (mean measured concentrations: 0, 2.0, 4.8, 13.2, 45.6 and 114 mg/l). Algae were exposed for 3 days to the substance and the cell densities were measured at the end of the testing period via spectrophotometric analysis. The biomass integral and the growth rate were calculated from the cell density determinations. All the test acceptability criteria were met.

Pentafluorobutane showed a low toxicity to algae: no EC50 for biomass and growth rate could be determined at any timepoint (72h-EC50 > 114 mg/l). A 0 -72 h NOEC of 13.2 mg/l was determined both for biomass and growth rate.