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Ecotoxicological information

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Description of key information

Members of this category are gases at standard temperature and pressure, therefore conducting an aquatic ecotoxicity test is technically difficult and based on exposure estimates the test may not be relevant. Therefore, the use of a QSAR to predict the ecotoxicity of representative components of these streams is an appropriate technique for aquatic toxicity. In addition, it is difficult to assess the toxicity of UVCB streams using standard test methods. Instead, it is more appropriate to consider the toxicity of representative components of these streams. As such, as the category is made up of C4 hydrocarbons, representative hydrocarbon C4 substances have been used as read-across.

The estimated EL50 TLM calculated range for short term toxicity to fish for but-1 -ene, 2 -butene, 2 -methylpropene, butene and propene is 14.758 mg/l-43.279 mg/l. These results are used as key read across. The lowest value has been taken forward as the key value for chemical safety assessment.

The use of ECOSAR is appropriate for this Category as these streams falls within the applicability domain of the model. The calculated 96 hour LC50 values for representative substances within this Category showed a short term toxicity to fish range of 19 - 27.9 mg/L These values have been used as supporting read across for this category.

Additional information

Measured ecotoxicity data are not available for the aquatic toxicity endpoints. In accordance with column 2 of REACH Annex VII and VIII, the acute toxicity tests do not need to be conducted if there are mitigating factors indicating that aquatic toxicity is unlikely to occur. 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. Therefore, in the absence of measured data, the toxicity of butenes has been estimated using a suitable QSAR (Nabholz and Mayo-Bean 2009). The equation used is suitable for non-polar narcotic chemicals. The endpoints calculated here are therefore reasonable estimates of their baseline toxicity.

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