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Ecotoxicological information

Long-term toxicity to aquatic invertebrates

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Description of key information

In accordance with column 2 of REACH Annex IX, the long term testing on invertebrates does not need to be conducted as the chemical safety assessment according to Annex I has not indicated a need to investigate further the effects on aquatic organisms. For butenes the estimated NOEC for Daphnia range from 1.23 mg/L to 1.54 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 invertebrates

Fresh water invertebrates
Effect concentration:
1.54 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 estimates is 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 Daphnia. The calculated ChV are 1.91 mg/L for but-1-ene, 2.18 mg/L for 2-butene and 1.73 mg/L for 2-methylpropene. These ChV values correspond to 21 day NOECs of 1.35 mg/L, 1.54 mg/L and 1.23 mg/L respectively.