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Toxicity to microorganisms

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Description of key information

The estimated protozoan, Tetrahymena pyriformis, 48-hr EL50 value is 112.4 mg/l for cyclpentane, based on growth inhibition. The estimated NOEL is 25.16 mg/l for cyclopentane, based on growth inhibition.

Key value for chemical safety assessment

Additional information

The aquatic toxicity was 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 partition coefficients (KMW) that describe the partitioning of the hydrocarbons between the water and organism. The estimated protozoan,Tetrahymena pyriformis, 48-hr NOEL value for cyclopentane is 25.16mg/L based on growth inhibition. The estimated protozoan,Tetrahymena pyriformis, 48-hr EL50 value for cyclopentane is 112.4mg/L based on growth inhibition.

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.