Registration Dossier

Diss Factsheets

Ecotoxicological information

Short-term toxicity to fish

Currently viewing:

Administrative data

Link to relevant study record(s)

Description of key information

The estimated freshwater fish 96 hour LL50 value is 29.3mg/l based on mortality. This is supported by an LC50 (96 hour) of 4.26 mg/l read across from n-pentane based on the geometric mean of the measured concentrations in the fresh and used medium. 

Key value for chemical safety assessment

Additional information

The aquatic toxicity was also estimated using the Petrotox computer model, which combines a partitioning model used to calculate the aqueous concentration of hydrocarbon components as a function of substance loading with the Target Lipid Model used to calculate acute and chronic toxicity of non-polar narcotic chemicals. Petrotox computes toxicity based on the summation of the aqueous-phase concentrations of hydrocarbon block(s) that represent a hydrocarbon substance and membrane-water partitioning coefficients (KMW) that describe the partitioning of the hydrocarbons between the water and organism. The estimated freshwater fish 96 hour LL50 value is 29.3mg/l based on mortality.

As there was no measured data available for cyclopentane, read across to n-pentane was used to support this value. The study (ExxonMobil Chemical 1997) was conducted according to OECD Guideline 203 (Fish, Acute Toxicity Test) with some minor deviations to minimise volatilisation of the substance. During testing a decrease of 80 % of n-pentane concentration was observed. Therefore LC50calculation was performed using the geometric mean of the measured concentrations in the fresh and used medium and a 95 % confidence limit was established. The study is considered reliable and suitable for use as a key study for this endpoint.

This value is supported by a QSAR calculation. The calculated 96 hour LC50 has been estimated as 7.128 mg/l for freshwater fish and 9.184 mg/l for saltwater fish. The ECOSAR model is a reliable and appropriate QSAR model to apply to cyclopentane as it is based on a related chemical dataset that calculates the toxicity to neutral organic hydrocarbons whose mode of action is non-polar narcosis. The endpoint calculated here is therefore a reasonable estimate of the baseline toxicity.

The hydrocarbon block method has been used for environmental risk assessment (see REACH guidance, R7, app.13-1). Aquatic PNECs for hydrocarbon blocks have been derived using the HC5 statistical extrapolation method and the target lipid model using representative structures. See Product Library tab in PETRORISK spreadsheet attached to IUCLID Section 13. Given the large database of freshwater organisms included in the target lipid model, an assessment factor of one has been applied to the HC5.