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Ecotoxicological information

Long-term toxicity to fish

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Description of key information

The long-term toxicity of o-tert-butylphenol was estimated using a QSAR model.  The 30 day NOEC was 0.231 mg/L.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish
Effect concentration:
0.231 mg/L

Additional information

No reliable long-term toxicity studies with fish are available for o-tert-butylphenol. However modeled data are available and included in the dossier.

Sasol (2013) provided reliable (Klimisch 2) data for o-tert-butylphenol using the QSAR model, Ecological Structure Activity Relationships (ECOSAR) Class Program to estimate long-term toxicity to fish. The ECOSAR model estimates aquatic toxicity based on the structural similarity to chemicals for which aquatic studies are available. In addition, the log Kow and molecular weight of o-tert-butylphenol are within the criteria (max log Kow = 7 for acute, 8 for chronic and max molecular weight = 1000) and domain of the model. The measured log Kow of 3.3 was used in the model. Model results indicate a 30 day chronic value (the geometric mean of the NOEC and LOEC) to be 0.327 mg/L for phenol. The baseline 30 day chronic value was 0.945 mg/L. As per REACH Guidance Ch 10, a NOEC can be calculated from the chronic value. Therefore, the calculated NOEC = 0.231 mg/L for the phenol category and consequently will be taken for the long-term toxicity to fish endpoint.

To evaluate model results for long-term toxicity to fish, measured toxicity data for other aquatic organisms were compared to modeled results. Below is a comparison of measured data and modelled data for the invertebrate, Daphnia, and algae for both the baseline case and for the phenol class. Comparisons indicate that modelled data, in general, are slightly lower and more conservative than the measured data. Therefore, use of the modelled data for fulfilling the requirement for long-term toxicity to fish is a conservative approach. Since o-tert-butylphenol is in the class of phenols, the result for phenol will be used as key for long-term toxicity to fish.

    ECOSAR 1.10
(w/ measured log Kow)
Measured Values
 96 hr Fish LC50   Phenol: 2.682 mg/L
Baseline: 8.391 mg/L
 >0.1 mg/L
 48 hr Daphnia EC50   Phenol: 1.441 mg/L
Baseline: 5.681 mg/L
 3.4 mg/L
 72/96 hr Algae EC50   Phenol: 5.839 mg/L
Baseline: 5.309 mg/L
6.5 mg/L 
 72/96 hr Algae ChV   Phenol: 2.698 mg/L
Baseline: 2.249 mg/L
  EC10 = 2.0 mg/L
NOEC = <1.2 mg/L
 30 day Fish ChV   Phenol: 0.327 mg/L
Baseline: 0.945 mg/L