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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

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Ecotoxicological information

Short-term toxicity to fish

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Administrative data

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Description of key information

The calculated freshwater fish 96 hour LC50 for butenes range from 29 to 38 mg/L. This range was derived from the members of the butenes category: but-1-ene (CAS 106-98-9), 2-butene (CAS 107-01-7) and 2-methylpropene (CAS 115-11-7) using QSAR estimates (Nabholz and Mayo-Bean 2009).

Key value for chemical safety assessment

Fresh water fish

Fresh water fish
Effect concentration:
29 mg/L

Additional information

Butenes are gases at standard temperature and pressure and are expected to partition primarily to air, therefore aquatic toxicity tests may not be relevant. In addition, it is technically difficult to maintain aqueous concentrations of gases for toxicity testing.

Measured data are not available for butenes for this endpoint. Due to the practical difficulties associated with the ecotoxicity testing of gases (i.e. maintaining exposure concentrations), the use of QSAR toxicity estimatesis an appropriate alternative. The ECOSAR model is a reliable and appropriate QSAR model to apply to butenes as it is based on a related chemical dataset that calculates the toxicity of neutral organic hydrocarbons whose mode of action is non-polar narcosis. The endpoint calculated here is therefore a reasonable estimate of the baseline toxicity.

A QSAR (ECOWIN v1 ECOSAR, Nabholz and Mayo-Bean 2009) has been used to give an indication of the toxicity of butenes to freshwater fish. The calculated 96 hour LC50 are 32.5 mg/L for but-1-ene, 38.2 mg/L for 2-butene and 28.9 mg/L for 2-methylpropene.