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Ecotoxicological information

Short-term toxicity to fish

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Description of key information

Using a reliable QSAR model, Ecological Structure Activity Relationships (ECOSAR) Class Program was used to estimate the 96hr LC50 for fish to be 2.16 mg/L. 

Key value for chemical safety assessment

Fresh water fish

Fresh water fish
Effect concentration:
2.16 mg/L

Additional information

Reliable (Klimisch 2) measured and modeled short-term toxicity studies in fish have been conducted for o-tert-amylphenol and are included in this dossier. These studies are summarized below. Additionally, reliable toxicity studies with fish with the structural analogues o-tert-butylphenol and o -sec-butylphenol have been included for supporting evidence.

Sasol (2016) provided a reliable (Klimisch 2) study for o-tert-amylphenol using the QSAR model, Ecological Structure Activity Relationships (ECOSAR) Class Program to estimate short-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-amylphenol 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 4.0 was used in the model. Model results indicate a 96 hr LC50 to be 2.16 mg/L based on the baseline toxicity equation. This result will be used as key for short-term toxicity to fish. In a reliable (Klimisch 2) 96-h acute toxicity study by Sewell (1992), rainbow trout (Oncorhynchus mykiss) were exposed to o-tert-amylphenol at nominal concentrations of 0 and 0.1mg/L under semi-static conditions. The 96-h LC50 was >0.1 mg/L as no mortality was observed during the test. Although this is considered a reliable study, the study results are based on a limit test, where only one test concentration was tested. Due to test performance, a definitive result was not possible.

For the structural analogues, acute fish studies are also available as supporting evidence. In a reliable (Klimisch 2) 96-h acute toxicity study by Wetton (1991), rainbow trout (Oncorhynchus mykiss) were exposed to o-tert-butylphenol at nominal concentrations of 0 and 0.1mg/L under semi-static conditions. The 96-h LC50 was >0.1 mg/L as no mortality was observed during the test. Although this is considered a reliable study, the study results are based on a limit test, where only one test concentration was tested. Due to test performance, a definitive result was not possible. In a 96-h acute toxicity study conducted by Japan MOE (1999) and presented in the SIDS Initial Assessment Report For CoCAM2 (2012) , medaka, (Oryzias latipes) were exposed to o-sec-butylphenol at measured concentrations of 0 ,1.0, 1.8, 3.2, 5.6, and 10 mg/L under semi-static conditions. The 96-h LC50 was 6 mg/L, based on mortality.

Reliable measured and modeled short-term toxicity studies with fish have been conducted for o-tert-amylphenol and the structural analogues o-tert-butylphenol and o-sec-butylphenol and are included in this dossier. In the experimentel short-term fish study with o-tert-amylphenol, no defined 96 -h LC50 value could be derived as no mortality was observed during the test. The result of the QSAR model was set as the k

ey study, Sasol (2016), providing a 96 -hr LC50 of 2.16 mg/L for fish for o-tert-amylphenol. Consequently this value will be taken as the short-term toxicity in fish endpoint for o-tert-amylphenol.