2-Methylpropene, trimers

Short-term toxicity to fish

Description of key information

The 96 hour LC50 for fish was calculated to be 1.19 mg/L for a category representative C8 structure. For C12 and C16 structures no effects were predicted at saturation – which supports the experimental data for the C16 stream.

Toxicity data was available for tetrabutene (Infracor (Speikamp), 2002) which reported the 96 hour LC50 to be >1.55 mg/L. Although this substance is not identified as a category member it would clearly fall within the category domain, being a tetramer of butylene with a predominant carbon number of C16. Due to the low solubility of the test substance, a WAF method was used to prepare the stock solution. 1 g of the test item was added to the test media and stirred for 18 hours. This solution was used as the highest exposure concentration and was diluted to provide the lower test concentrations. Samples were taken to confirm the exposure concentrations at the time of test media exchange (new and old media sampled). The geometric mean concentration at the highest loading rate was 1.55 mg/L. This was the highest exposure concentration that could be produced, and no mortality was observed at this concentration. The 96 hour LC50 was therefore determined to be > 1.55 mg/L.This value have been used in the PBT assessment of this category.

In the absence of experimental data for the other streams in this category this single result is supported by data estimated using an established QSAR (ECOSAR, model in EPISuite V4.0). The 96 hour LC50 for fish was calculated to be 1.19 mg/L for a category representative C8 structure. For C12 and C16 structures no effects were predicted at saturation – which supports the experimental data for the C16 stream.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

1.19 mg/L