2,2,5-trimethyl-5-pentylcyclopentan-1-one

Short-term toxicity to fish

Description of key information

Weight of Evidence approach:
96h-LC50 = 1.3 mg/L (95% CL: 1.2 - 1.5 mg/L). 

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

1.3 mg/L

Additional information

To assess the short-term toxicity of the registered substance to fish, a weight of evidence approach was used with two data available.

The first data (Kyushu, 1986) was experimentally determined according to Japan Industrial Standard K 0102 titled "Test method on effluents from factories" but without GLP statement, in order to assess the 48h-acute toxicity of the registered substance to Oryzias latipes, under semi-static conditions. The test substance was exposed to Oryzias latipes at nominal concentrations of 4.8, 6.4, 8.5, 11.3, 15.0 and 20.0 mg/L, including a control group. Ten fish per level was used and no analytical monitoring of tested concentrations was performed. Estimation of 48h-LC50 value was obtained graphically by Doudoroff method. According to the results of this study, the 48h-LC50 was determined at 5.45 mg/L based on nominal concentrations. This study is considered not assignable because details on materials and methods were not completely reported. In addition, the study period was shorter than recommended for a fish study (96 hours). Therefore, the value of 5.45 mg/L for a fish 48h-LC50 is probably unrepresentative of the true 96h-LC50.

The second data (KREATiS, 2015) is a QSAR. This QSAR prediction (iSafeRat holistic approach v1.4) was performed on the registered substance, to assess the acute toxicity of the substance to fish. This QSAR has been validated to be compliant with the OECD recommendations for QSAR modelling (OECD, 2004) and predicts the endpoint value which would be expected when testing the substance under experimental conditions in a laboratory following OECD Guideline 203. The acute toxicity to fish was determined using a validated QSAR for the Mode of Action in question, (MOA 1, non-polar narcosis). The QSAR is based on validated data for a training set of 67 chemicals derived from 96-hour tests on fish, for which the concentrations of the test substance had been determined by chemical analyses over the test period. The substance falls within the applicability domain of the model. The 96h-LC50 value based on mortality and measured concentrations was determined to be 1.3. mg/L (95% CL: 1.2 - 1.5 mg/L).

The registered substance, as a ketone, is attributed to the class of non-polar narcotic compounds (MOA 1). For this mode of action, there is no reason to consider significantly higher toxicity for any of the three aquatic species. The 96h-LC50 fish is considered to be comprised between 1 and 10 mg/L like aquatic invertebrates and algae.

In conclusion, according to this weight of evidence approach, the lowest LC50 value, predicted at 1.3 mg/L by iSafeRat holistic approach v1.4, is considered as the key value for chemical safety assessment and PNEC derivation.