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Long-term toxicity to aquatic invertebrates

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Endpoint:
long-term toxicity to aquatic invertebrates
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Remarks:
Summary of available data used for the endpoint assessment of the target substance.
Adequacy of study:
key study
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Duration:
21 d
Dose descriptor:
NOELR
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
WAF
Basis for effect:
reproduction
Remarks on result:
other:
Remarks:
Source: CAS 3687-45-4, Ecogreeen, 2013, D. magna, 21 d
Duration:
21 d
Dose descriptor:
EL50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
WAF
Basis for effect:
mortality
Remarks on result:
other:
Remarks:
Source: CAS 3687-45-4, Ecogreeen, 2013, D. magna, 21 d
Conclusions:
No effects up to the limit of water solubility (< 0.05 mg/L, OECD 211, D. magna, 21 d); read-across
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:
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.

Endpoint:
long-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
05 Jan - 22 May 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 211 (Daphnia magna Reproduction Test)
Qualifier:
according to
Guideline:
EU Method C.20 (Daphnia magna Reproduction Test)
GLP compliance:
yes (incl. certificate)
Remarks:
Swiss Federal Office of Public Health, Bern, Switzerland
Analytical monitoring:
yes
Details on sampling:
- Concentrations: Control, 100 mg/L
- Sampling method: Duplicate samples were taken from the freshly prepared test medium of the single test concentration and from the control at one treatment period of the first, second and last week of the test (day 0, 2, 7 and 16, respectively). To determine the maintenance of the test substance concentration in test medium, stability samples were taken at the end of two test medium renewal periods of 48 h (day 2 and 9) and at the end of two renewal periods of 72 h (days 5 and 19).
- Sample storage conditions before analysis: All samples were stored deep-frozen (at about -20 °C) and protected from light immediately after sampling.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: A dispersion with the nominal concentration of 100 mg/L was prepared prior to the start of the test and prior to each medium renewal by dispersing 400 and 200 mg of the test item (dosed in the range of 400 to 401 mg on days 0, 7 and 16 and in the range of 200 to 201 mg on days 2, 5, 9, 12, 14 and 19) in 4000 and 2000 mL of test water under intense stirring for 96 h at room temperature in the dark to avoid photolytic degradation. After the 96 h stirring period, the test item was filtered through a membrane filter (Schleicher & Schuell, Type NC45, pore size 0.45 µm). The test medium was prepared just before the start of the test (= addition of daphnids) and before each test medium renewal.
- Eluate: no
- Differential loading: no
- Controls: yes, test medium control
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: water flea
- Source: Originally supplied by the University of Sheffield/UK in 1992. Since this date, the clone is successfully bred at Harlan Laboratories.
- Age of parental stock (mean and range, SD): < 24 h
- Feeding during test
- Food type: food mixture containing a suspension of green algae of the species Scenedesmus subspicatus (freshly grown at the laboratory) and a fish food suspension. The fish food suspension was prepared by dispersing 10 g of powdered commercial fish diet (TETRA MIN Hauptfutter, obtained from TETRA-Werke, Melle, Germany) in 500 mL of test water. The suspension was allowed to stand for 4 hours. Then, 400 mL of the supernatant were taken, diluted 1:1 with test water and boiled. The suspension was stored deep frozen in small quantities until use.
- Amount: 0.20 mg TOC per Daphnia and day
- Frequency: daily
- Method of breeding: Each stock animal was maintained separately in a 100 mL glass beaker filled with about 80 mL culture medium and was transferred twice a week to fresh medium. The condition of the stock animals was frequently checked. No signs of stress were observed and the brood stock was healthy.

ACCLIMATION
- Acclimation period: The daphnids used for the test originated form parental daphnids that were at least 14 d old but not older than four weeks and were not first brood progeny.
- Acclimation conditions (same as test or not): same as test
- Type and amount of food: same as test
- Feeding frequency: three times a week
Test type:
semi-static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
21 d
Test temperature:
20 - 21 °C
pH:
7.7 - 8.1
Dissolved oxygen:
8.2 - 9.2 mg O2/L
Nominal and measured concentrations:
nominal: control, 100 mg/L
measured: < LOQ in the control and treatment
Details on test conditions:
TEST SYSTEM
- Test vessel: beakers
- Type (delete if not applicable): covered with glass plates to reduce loss of water by evaporation and to avoid the entry of dust into the solutions.
- Material, size, headspace, fill volume: glass, 100 mL, headspace: 20 mL, fill volume: 80 mL
- Aeration: no
- Renewal rate of test solution (frequency/flow rate): renewed on days 2, 5, 7, 9, 12, 14, 16 and 19.
- No. of organisms per vessel: 1
- No. of vessels per concentration (replicates): 20
- No. of vessels per control (replicates): 20

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: reconstituted water (Elendt M7 medium)
- Alkalinity: 0.9 mmol/L
- Water hardness: 250 mg/L as CaCO3
- Culture medium different from test medium: no

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: 16 h light / 8 h dark (30 min transition period)
- Light intensity: 400 - 540 lux

EFFECT PARAMETERS MEASURED: Mortality and reproduction on days 0-2 and thereafter at least three times per week before renewal of test media. On the same dates, the test repliacates were observed for the number of living and dead offspring and for the presence of aborted eggs.
Reference substance (positive control):
no
Duration:
21 d
Dose descriptor:
NOELR
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
WAF
Basis for effect:
reproduction
Duration:
21 d
Dose descriptor:
EL50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
WAF
Basis for effect:
mortality
Details on results:
- Mortality of parent animals: 0% in control; 5% in treatment
- Type and number of behavioural abnormalities: No visible abnormalities were observed during the test.
- No. of offspring produced after 21 d per female: 142 (mean, control); 137 (mean, treatment)
- Time to first brood release or time to hatch: day 9 in control and treatment
Reported statistics and error estimates:
Student t-test (one-sided smaller, α = 0.05) with the mean values of living offspring.

Description of key information

No effects up to the limit of water solubility (1.39 µg/L, 20 °C, OECD 211, D. magna); read-across

Key value for chemical safety assessment

Additional information

There is no study available assessing the long-term toxicity of the target substance Isohexadecyl 12-[(1-oxooctadecyl)oxy]octadecanoate (CAS 97338-28-8) to aquatic invertebrates. Therefore, read-across to the structurally related source substances (Z)-octadec-9-enyl oleate (CAS 3687-45-4) and 2-octyldodecyl isooctadecanoate (CAS 93803-87-3) was conducted in accordance with Regulation (EC) No. 1907/2006 Annex XI, 1.5. The source substances are characterized by similar, but smaller fatty acid esters and are therefore considered suitable representatives 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.

The available study with the source substance (Z)-octadec-9-enyl oleate (CAS 3687-45-4) was conducted according to OECD 211 and GLP (Ecogreen, 2013). The test was performed with Daphnia magna under semi-static conditions. Due to the very low water solubility (< 0.05 mg/L) a limit test with a Water Accommodated Fraction (WAF) of nominal 100 mg/L was performed.

After 21 d no effects on reproduction and mortality were recorded, resulting in a NOELR (21 d) of ≥ 100 mg/L. 0% mortality was recorded in the control whereas 5% mortality was observed in the treatment. This mortality is regarded as natural and tolerated by the test guideline. The chemical analysis resulted in concentrations below the analytical detection limit of 0.0423 mg/L reflecting the very low water solubility of the test item. Based on this result, it can be concluded that the source substance (Z)-octadec-9-enyl oleate (CAS 3687-45-4) does not cause chronic effects on aquatic invertebrates up to the limit of water solubility.

No experimental studies assessing the long-term toxicity of the source substance 2-octyldodecyl isooctadecanoate (CAS 93803-87-3) to aquatic invertebrates are available. However, a statement from a laboratory is available indicating that the study is technically not feasible due to substance characteristics (Croda, 1998). Acute testing in Daphnia magna is performed by exposing organisms to nominal Water Accommodated Fractions (WAFs). Owing to the fact that the test substance is a liquid with water solubility below detection limit (< 0.05 mg/L) and a log Kow of > 7, it is not possible to prepare solutions that can be tested in a 21-day reproduction test with Daphnia magna. Based on 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. Furthermore, bioavailable concentrations of the test substance are not likely to ever occur in the water phase, i.e. concentrations high enough to induce any acute or chronic effects in aquatic organisms due to the particular substance characteristics. Therefore, no chronic test with aquatic invertebrates was conducted for the source substance 2-octyldodecyl isooctadecanoate (CAS 93803-87-3).

Based on the structural and chemical similarity of the target and source substance, the target substance is expected to exhibit a similar ecotoxicological profile. Therefore, it can be concluded that the target substance Isohexadecyl 12-[(1-oxooctadecyl)oxy]octadecanoate (CAS 97338-28-8) does not cause long-term effects to aquatic invertebrates up to the limit of water solubility. Moreover, experimental studies are a technical challenge due to substance characteristics.