Fatty acids, C18-unsaturated, 2-hexyldecyl ester

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Statement from the laboratory that the study is technically not feasible due to the substance characteristics.

Qualifier:

according to guideline

Guideline:

other: OECD Guideline No. 202: “Daphnia sp., Acute Immobilisation Test and Reproduction Test”, Adopted April 4, 1984, extended with recommendations and supplements which are included in the Draft proposal for OECD Guideline 211.

GLP compliance:

yes

Remarks on result:

not determinable because of methodological limitations

Remarks:

No suitable analytical method could be established to conduct this study properly.

The testing in aquatic systems requires generation of test solutions which contain completely dissolved test substance concentrations or stable and homogeneous mixtures or dispersions. The test guidelines recommend to exclude concentrations that may disturb the test system (e.g. film of the test substance on the water surface or deposits of test substance on the bottom of the vessels).

 

With the analytical method available it was not possible to detect concentrations of the test substance in water samples. During a preliminary test, the water solubility was determined to be ≤ 0.1 mg/L at 19.0 ± 1.0 °C. Since the test substance is a liquid and the water solubility ≤ 0.1 mg/L, the flask method nor the column elution method are applicable for determination of the water solubility. Therefore, no main study for determination of the water solubility has been performed (see NOTOX Project 227126 “Determination of the water solubility of [trade name]‘). The partition coefficient (Pow) could not be experimentally determined, but was calculated to be ≥ 1 x 10^7 (log Pow ≥ 7) as a quotient of the n-octanol solubility and water solubility (see NOTOX Project 227148 ‘Determination of the partition coefficient (N-octanol/water) of [trade name]‘).

 

Acute testing with Daphnia magna was performed by exposing organisms to Water Accommodated Fractions (WAFs) (see NOTOX Project 227341 ‘Acute toxicity study in Daphnia magna with [trade name]‘). However, it is not common practice to use this approach in a prolonged toxicity test. The use of a column generator with the test substance coated on an inert carrier (glass beads or celite) is not possible as the test substance is a liquid. The testing in a flow-through system is also no possible alternative, since the hydrophobic character of the test substance hampers any way of mixing with the dilution water.

As already stated, owing to the high hydrophobicity, there is no analytical method sensitive enough to detect concentrations of the test substance in water samples. As a result, it is not possible to give any analytical support to the reproduction test with Daphnia magna. This analytical support is essential to meet the acceptability criterion for evidence that the actual concentration had been maintained within a 20% window during the total test period.

In conclusion: Owing to the fact that the test substance is a liquid with a water solubility below detection (< 0.1 mg/L) and a log Pow of ≥ 7, it is not possible to prepare solutions that can be tested in a 21-day reproduction test with Daphnia magna. Further, these characteristics support the expectation that it will not be very likely that bioavailable concentrations of the test substance will ever occur in the water phase, i.e. concentrations high enough to induce any acute or chronic effects in aquatic organisms.

Reference 2

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Refer to analogue justification provided in IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Remarks on result:

not determinable because of methodological limitations

Remarks:

No suitable analytical method could be established to conduct this study properly.

Executive summary:

The assessment of the long-term toxicity of the substance to aquatic invertebrates was on the one hand technically not feasible due to the high hydrophobicity (log Kow > 10) and very low water solubility of the substance below the limit of detection (< 0.1 mg/L), and on the other hand scientifcially not reasonable because bioavailable concentrations high enough to induce any acute or chronic effects in aquatic organisms are unlikely to ever occur in the water phase due to the above-mentioned properties.

Description of key information

A study according to OECD 211 for a similar source substance was technically not feasible due to substance properties; read-across

Additional information

No studies are available, in which the long-term toxicity of the target substance Fatty acids, C18-unsaturated, 2-hexyldecyl ester to aquatic invertebrates was assessed. Therefore, read-across to the structurally related source substance 2-octyldodecyl isooctadecanoate(CAS 93803-87-3) was conducted in accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5. The source substance is characterized by similar fatty acid and alcohol components and is therefore considered a suitable representative for the assessment of the chronic toxicity of the target substance to aquatic invertebrates. A detailed justification of the analogue approach is provided in IUCLID section 13.

By means of the read-across approach, results are available from a study conducted according to OECD guideline 211 and GLP. The report consists of a statement from the testing laboratory, which concluded that the study was technically not feasible and also scientifically not reasonable due to the substance properties (high hydrophobicity, poor solubility), which on the one hand preclude the analytical detection of the test item in the test media (solubility below detection limit) and on the other hand make it highly unlikely for bioavailable concentrations in water to ever occur that are high enough to cause any acute or chronic effects in aquatic organisms.

Based on the structural and chemical similarities between the target and source substance, it can be concluded that the testing of the long-term toxicity of the target substance Fatty acids, C18-unsaturated, 2-hexyldecyl ester to aquatic invertebrates would likely face the same technical challenges.