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Ecotoxicological information

Long-term toxicity to fish

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Description of key information

The key study for this endpoint is based on the well described  literature study of Lanno and Dixon (1994) in which fathead minnows were exposed to potassium thiocyanate. The NOEC for decreased egg production, overt goitre, increased time to first spawn was 1.1 mg/L SCN-, equivalent to 1.84 mg/L KSCN

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater fish:
1.84 mg/L

Additional information

Four literature studies were available for this endpoint, two for KSCN, and one for SCN- (with the identity of the cation unknown). The study on the SCN- was considered unusable as only the abstract was available. The remaining studies described toxicity of potassium thiocyanate to fathead minnow (Pimephales promelas) and rainbow trout (Oncorhynchus mykiss) and toxicity of sodium thiocyanate to Cyprinus carpio. The key values from these studies were:

124 d NOEC = 1.1 mg/L SCN- (P. promelas) and 16 wk NOEC = 77 mg/L (O. mykiss). Both studies were well described and with analytical monitoring of the SCN- concentrations. The study describing chronic toxicity to P. promelas was chosen as the key study for this endpoint due to the lower NOEC value of 1.1 mg/L SCN- (1.84 mg/L KSCN)

As there were no GLP studies for this endpoint, further long term studies with fish were waived based on the short term data for daphnia, fish and algae; where it was shown that fish were the least sensitive organisms, thus it would not be expected that they would be more sensitive in a long term study, thus conducting a long term fish study would add no scientific value, except to use a lower assessment factor. Also due to ethical reasons, it would be inappropriate to conduct a long term fish study.