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Short-term toxicity to aquatic invertebrates

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Description of key information

The estimated freshwater invertebrate 48 hour EL50 value is 48.11mg/l based on mobility. This is supported by measured data. The 48hr EC50 for Daphnia magna reported was 2.7mg/l

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
2.7 mg/L

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 48 hour EL50 value is 48.11mg/l based on mobility.

This is supported by measured data. The study for n-pentane (Adema and Bakker 1986) is equivalent to OECD 202, using a static, closed system with low headspace, a standard test species (Daphnia magna) and the standard exposure duration (48hrs). The 48hr EC50for Daphnia magna reported was 2.7 for n-pentane, based on initial measured concentrations. The true EC50 value maybe higher since loss of the starting material was determine to be about 50% during the 48hr exposure period. The version of the study reviewed lacked the annex containing key details on the test conditions and therefore these could not be reviewed and generally validated against OECD criteria. Two other marine crustaceans were also used in the study, Chaetogammarus marinus and Mysidopsis bahia. The tests with marine crustaceans were carried out with only one animal per container (10 individuals per concentration). LC50values for both species were based on the initial measured concentration. C marinus LC 50 (96 hours) = 3.2 mg/l (initial measured concentration) and M bahia = 3.2 mg/l (initial measured concentration).

This is supported by a calculated QSAR value. The predicted 48 hour EC 50 for Daphnia of 2.8 mg/l has been calculated using QSAR estimations. This data was cited as a supporting study in the EU RAR n-pentane and is deemed adequate for assessment as a supporting study for this endpoint.

This result would not indicate that n-pentane would meet the criteria for toxic in the PBT assessment. However, the 48 hour EC50 of 2.7 mg/l would result in a classification of acute category 2 with the hazard phrase 'toxic to aquatic life'.

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.