Docosyl stearate

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

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

Justification for type of information:

Please refer to the analogue justification attached to IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Duration:

21 d

Dose descriptor:

NOELR

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

based on Water Accomodated Fraction

Basis for effect:

reproduction

Remarks on result:

other: Source, CAS 3687-45-4, DHW, 2013, D. magna, 21 d

Duration:

21 d

Dose descriptor:

NOELR

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

based on Water Accomodated Fraction

Basis for effect:

mortality

Remarks on result:

other: Source, CAS 36078-10-1, Dako, 2013, D. magna, 21 d

Remarks on result:

other: not determinable because of methodological limitations

Remarks:

Source, CAS 93803-87-3, 1998, D. magna

Conclusions:

The key value for the long-term toxicity of the target substance is a NOELR (21 d) ≥ 100 mg/L (nominal) based on experimental studies for two structurally and chemically closely related source substances (OECD 211, D. magna).

Description of key information

NOELR (21 d) of ≥ 100 mg/L (nominal, OECD 211, read-across)

Additional information

Since no studies investigating the long-term toxicity to aquatic invertebrates of Docosyl stearate (CAS 21443-03-2) are available, in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5 a read-across to the structurally related source substances 9-Octadecenoic acid (Z)-, 9-octadecenyl ester, (Z)- (CAS 3687-45-4), dodecyl oleate (CAS 36078-10-1) and 2-octyldodecyl isooctadecanoate (CAS 93803-87-3) were conducted. The source substances are considered to be representative to evaluate the short-term toxicity of Docosyl stearate (CAS 21443-03-2) to aquatic invertebrates. The target substance is an ester of stearic acid (C18) and docosanol (C22). The source substance Dodecyl oleate (CAS 36078-10-1) is an ester of similar fatty acid (C18:1) and a shorter chain alcohol (C12). 9-Octadecenoic acid (Z)-, 9-octadecenyl ester, (Z)- (CAS 3687-45-4) is described by oleic acid (C18:1) and an a alcohol chain (C18:1). 2-octyldodecyl isooctadecanoate (CAS 93803-87-3) is described by isostearic acid (C18) and a branched alcohol (C20) with comparable chain length to the target substance. The source substances are therefore considered suitable representatives for the assessment of the long-term toxicity of the target substance to aquatic invertebrates.

This read-across is justified in detail within the analogue justification in IUCLID Section 13. In this case of read-across, the best suited (highest degree of structural similarity, nearest physico-chemical properties) read-across substance was used for the assessment.

The study with the read-across substance 9-Octadecenoic acid (Z)-, 9-octadecenyl ester, (Z)- (CAS 3687-45-4) was performed according to OECD. The study was performed with the water flea 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. No effects on reproduction and mortality were recorded after 21 d 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 the result it can be concluded that 9-Octadecenoic acid (Z)-, 9-octadecenyl ester, (Z)- will not exhibit chronic effects on aquatic invertebrates up to the limit of water solubility.

The second study with the read-across substance dodecyl oleate (CAS 36078-10-1) was performed according to OECD 211 under GLP conditions with the water flea Daphnia magna. Five nominal loading rates up to 100 mg/L were tested in a semi-static exposure system as Water Accommodated Fractions (WAFs). No effects on the reproduction of D. magna were observed after 21 d. One dead animal was recorded at 50 mg/L but it was reported that it was no substance specific effect (accident during medium change). Therefore, a NOELR (21 d) of ≥ 100 mg/L (nominal) was derived. The chemical analysis resulted in concentrations below the analytical detection limit of 0.005 mg/L reflecting the very low water solubility of the test item. Based on the result it can be concluded that dodecyl oleate will not exhibit chronic effects on aquatic invertebrates up to the limit of water solubility.

For the read-across substance 2-octyldodecyl isooctadecanoate (CAS 93803-87-3) a statement from a laboratory is available indicating that the study is technically not feasible due to substance characteristics. Acute testing in Daphnia magna was performed by exposing organisms to Water Accommodated Fractions (WAFs). 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. 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. 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. 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. Thus, no chronic test with aquatic invertebrates was conducted and the same difficulties are expected to occur when testing the target substance itself.

Based on the available results from three structurally related source substances (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5) which are characterized by a similar ecotoxicological profile and comparable structure, it can be concluded that docosyl stearate (CAS 22413-03-2) will not exhibit long-term effects to aquatic invertebrates up to the limit of water solubility.