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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

Area under the growth curve (measured concentrations);
EbC50 (72h): 10.5 mg/L (95% confidence limits, 9.55 & 11.7 mg/L)
EbC50 (96h): 10.1 mg/l (95% confidence limits, 9.21 & 11.1 mg/L)
No observed effect concentration (NOEC): 3.61 mg/L
Average specific growth rate (measured concentrations):
ErC50 (0-72h): 12.0 mg/L (95% confidence limits, 7.22 & 21.1 mg/L)
ErC50 (0-96h): 13.2 mg/L (95% confidence limits, 12.2 & 14.3 mg/L)
No observed effect concentration (NOEC): 7.22 mg/L

Key value for chemical safety assessment

EC50/LC50 for freshwater algae:
12 mg/L
EC10, LC10 or NOEC for freshwater algae:
7.22 mg/L

Additional information

One reliable proprietary freshwater study, Huntingdon (2004d) is available for the isomer 2-methylbut-2-ene (CAS 513-35-9). Since isoamylene (2-methylbutene, CAS 26760-64-5) is a mixture of the two isomers, 2-methylbut-2-ene (CAS 513-35-9) and 2-methylbut-1-ene (CAS 563-46-2) and in the absence of any reliable data for isoamylene the data for the isomer (CAS 513-35-9) are considered suitable for read-across.

These results show that using area under average specific growth rate (measured concentrations); ErC50 (0-72h): 12.0 mg/L (95% confidence limits, 7.22 & 21.1 mg/L), ErC50 (0-96h): 13.2 mg/L (95% confidence limits, 12.2 & 14.3 mg/L), no observed effect concentration (NOEC): 7.22 mg/L.