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Short-term toxicity to fish

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Description of key information

LC50 estimated from available data on structural analogs

Key value for chemical safety assessment

Fresh water fish

Fresh water fish
Effect concentration:
100 mg/L

Additional information

The assessment of the possible aquatic toxicity of HFC 125 has been carried out by considering available data on structurally analogue substances.

Experimental data for acute toxicity on fish are available for HFC 134a (1,1,1,2 -tetrafluoroethane), HFC 143a (1,1,1 -trifluoroethane), HFC 245fa (1,1,1,3,3 -pentafluoropropane) and HFC 365mfc (1,1,1,2,2 -pentafluorobutane).

In all cases studies were conducted in closed systems to avoid substance volatilisation. However, significant volatility was observed in the study for HFC 143a, in which the mean measured concentration were only 20% of the initial nominal concentrations. For this reason, the experimental result of the HFC 143a study is considered of lower relevance for the extrapolation to HFC 125.

In all cases, the substances showed a low toxicity to fish. 96 h-LC50 could be identified only for HFC 134a (LC50 = 450 mg/l), as low mortality was observed up to the highest tested concentration for the other substances. Overall, a fish 96h LC50= 100 mg/l

(i.e. the lowest experimental value determined for structural analogues) can be considered as a conservative estimation of the acute toxicity to fish for HFC 125.

HFC 245fa: The acute toxicity test was conducted in Oncorhynchus mykiss (rainbow trout). Fishes were exposed to 1, 10 and 100 mg/l HFC 245fa (nominal concentrations) in a closed system (semi-static conditions) for 96 hours. Measured concentrations increased between renewals suggesting HFC-245fa has a slow rate of dissolution in the dilution medium under the conditions of the test. A condition of maximum attainable exposure was considered to have been achieved. No mortality was observed during the study. An LC50 > 100 mg/l based on nominal concentration was derived from the study (mean measured concentration = 81.8 mg/l).

HFC 365mfc: The acute toxicity of pentafluorobutane in zebra fish (Brachydanio rerio) was studied under semi-static conditions. The study was conducted at nominal concentrations of 0, 100, 150 and 200 mg/l pentafluorobutane. The substance was solubilised in ISO-water and the test was performed in closed system due to the high volatility of pentafluorobutane. 7 fishes/exposure group (3 vessels per group containing 2, 2 and 3 fishes, respectively) were exposed for 96 hours. Test solutions were renewed each day to avoid decrease of dissolved oxygen below the acceptable limits. Concentration of the test substance in the vessels was determined at the start of the study, before and after the test solution daily renewal and on the last day of the study. The difference among nominal and measured concentration was always below 20%. No mortality was observed during the test in the control and exposure group (LC50>200 mg/l nominal concentration). Sublethal effects (lower activity or fishes lying at the bottom of the flaskes) were observed at 200 mg/l (NOEC = 150 mg/l).

HFC 134a: The 96-hour LC50 for HFC-134a in rainbow trout (Salmo gairdneri) was 450 mg/l under semi-static conditions. No mortality was observed at concentrations of 180 and 300 mg/l, although symptoms of toxicity were observed (dark discolouration, quiescence and sounding behaviour). No symptoms of toxicity were seen at a concentration of 87 mg/l.

HFC 143a: The 96 -hr LC50 in rainbow trout was determined to be > 40 mg/l (analytically measured by GC). The nominal concentration for this level was 350 mg/l. This large difference between nominal concentrations and measured concentrations is the result of testing a highly volatile material (boiling point -47.4 deg C) that is only slightly soluble in an aqueous system and rapidly is lost from the test system. It is therefore concluded that the calculated value of 109 mg/L is the more accurate value.