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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

The following results were determined for the test item reaction mass of 2,2'-oxybisbutane (DSBE), DIPE, SBA and 2-methylpropan-2-ol (TBA) (species: Desmodesmus subspicatus): 72h-ErC50 (growth rate) = 58 mg/L

Key value for chemical safety assessment

EC50 for freshwater algae:
58 mg/L

Additional information

The EC50 value and the NOEC for growth inhibition, AUC and yield of reaction mass of 2,2'-oxybisbutane (DSBE), DIPE, SBA and 2-methylpropan-2-ol (TBA) was measured according to OECD 201, respectively EU C.3 guideline under GLP. Following results were obtained:

Endpoint

NOEC

LOEC

EC50

Growth Rate

8.6 mg/L

19 mg/L

58 mg/L

AUC

8.6mg/L

19 mg/L

23 mg/L

Yield

8.6mg/L

19 mg/L

25 mg/L

The analytical determinations of the test item showed poor correlation between nominal and measured concentrations and acceptable recovery rates. The poor correlation is probably caused by the high volatility of the test item. Therefore, the determination of the results of the test item reaction mass of 2,2'-oxybisbutane (DSBE), DIPE, SBA and 2-methylpropan-2-ol (TBA) was based on the geometric means of the measured concentrations.

Based on these data in combination with the fact that the substance is not readily biodegradable, a classification into aquatic chronic category 3 (H412) according to the CLP regulation (corresponding to R52/53) is necessary (EC50 10-100 mg/l).

Based on the lowest EC50 value of the three species daphnia, algae and fish (available studies), an aquatic PNEC value was calculated for the risk assessment. As values from algae test based on growth rate, not on biomass or yield, should be employed for classification and risk assessment, the relevant EC50 value is 58 mg/L. Therefore, the value for algae does not represent the lowest value of the three species daphnia, algae and fish.