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Long-term toxicity to aquatic invertebrates

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Description of key information

The estimated freshwater invertebrate 21-day NOELR (No Observed Effect Loading Rate) value is 13.29 mg/l for 2-methylbutane, based on reproduction.

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 partitioning coefficients (KMW) that describe the partitioning of the hydrocarbons between the water and organism. The estimated freshwater invertebrate 21-day NOELR (No Observed Effect Loading Rate) value is 13.29mg/l based on reproduction.

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.