2-butyloctanoic acid

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

(Q)SAR

Adequacy of study:

key study

Study period:

2017

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: A QSAR model, ECOSAR was used to estimate long-term toxicity to aquatic invertebrates

Justification for type of information:

QSAR prediction from reliable model

Qualifier:

no guideline required

Principles of method if other than guideline:

The QSAR model, Ecological Structure Activity Relationships (ECOSAR) Class Program was used to estimate the long-term toxicity to aquatic invertebrates. The following measured values were used in the model: log Kow = 4.33 and water solubility = 21.7 mg/L.

Test organisms (species):

Daphnia sp.

Water media type:

freshwater

Key result

Duration:

21 d

Dose descriptor:

other: chronic value (geometric mean of NOEC and LOEC)

Effect conc.:

1.662 mg/L

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

1.175 mg/L

Details on results:

As per REACH Guidance Ch 10, a NOEC can be calculated from the chronic value by dividing the chronic by the square root of 2. Therefore, the calculated NOEC = 1.175 mg/L and will be used in the assessment.

Conclusions:

Using a reliable QSAR model, Ecological Structure Activity Relationships (ECOSAR) Class Program was used to estimate the 21d ChV for daphnids to be 1.662 mg/L.

Executive summary:

A reliable QSAR model (Ecological Structure-Activity Relationship (ECOSAR) version 1.11) was used to predict the chronic aquatic toxicity of 2 -butyloctanoic acid to daphnids. The 21 day chronic value (the geometric mean of the NOEC and LOEC) was 1.662 mg/L for the neutral organic class. As per REACH Guidance Ch 10, a NOEC can be calculated from the chronic value. Therefore, the calculated NOEC = 1.175 mg/L and will be used in the assessment as the key value for long-term toxicity to aquatic invertebrates.

Description of key information

The long-term toxicity of 2 -butyloctanoic acid was estimated using a QSAR model.  The 21 day ChV was 1.662 mg/L and the calculated NOEC was 1.175 mg/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

1.175 mg/L

Additional information

No reliable experimental long-term toxicity studies with aquatic invertebrates are available for 2 -butyloctanoic acid. However reliable (Klimisch 2) modeled data are available and included in the dossier.

Sasol (2017) provided reliable (Klimisch 2) data for 2 -butyloctanoic acid using the QSAR model, Ecological Structure Activity Relationships (ECOSAR) Class Program to estimate long-term toxicity to aquatic invertebrates. 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 2 -butyloctanoic acid 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 4.33 was used in the model. Model results indicate a 21 day chronic value (the geometric mean of the NOEC and LOEC) to be 1.662 mg/L using the baseline toxicity equation. As per REACH Guidance Ch 10, a NOEC can be calculated from the chronic value. Therefore, the calculated NOEC is 1.175 mg/L.