Docosyl stearate

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

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

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

based on water accommodated fraction

Basis for effect:

growth rate

Remarks on result:

other: Source, CAS 36078-10-1, Dako, 2013, D. subspicatus, 72 h

Duration:

72 h

Dose descriptor:

NOELR

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

based on water accommodated fraction

Basis for effect:

growth rate

Remarks on result:

other: Source, CAS 36078-10-1, Dako, 2013, D. subspicatus, 72 h

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

based on water accommodated fraction

Basis for effect:

growth rate

Remarks on result:

other: Source, CAS 93803-87-3, 1998, S. capricornutum

Duration:

72 h

Dose descriptor:

NOELR

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

based on water accommodated fraction

Basis for effect:

growth rate

Remarks on result:

other: Source, CAS 93803-87-3, 1998, S. capricornutum, 72 h

Conclusions:

The key values for the toxicity to aquatic algae are an EL50 (72 h) of > 100 mg/L and a NOELR (72 h) of ≥ 100 mg/L (nominal), based on experimental data with two structurally and chemically closely related source substances (OECD 201, D. subspicatus and S. capricornutum).

Description of key information

ErL50 (72 h) > 100 mg/L (WAF, nomminal, D. subspicatus and S. capricornutum, respectively, read-across)

NOErLR (72 h) ≥ 100 (WAF, nomminal, D. subspicatus and S. capricornutum, respectively, read-across)

Additional information

Since no studies are available investigating the toxicity of Docosyl stearate (CAS 21443-03-2) to aquatic algae and cyanobacteria a read-across to the structurally related source substances dodecyl oleate (CAS 36078-10-1) and 2-octyldodecyl isooctadecanoate (CAS 93803-87-3) were conducted, in accordance to Regulation (EC) No 1907/2006 Annex XI. The source substances are considered to be representative to evaluate the short-term toxicity of Docosyl stearate (CAS 21443-03-2) to aquatic algae and cyanobacteria. 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). 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 short-term toxicity of the target substance to aquatic algae and cyanobacteria.

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 dodecyl oleate (CAS 36078-10-1) was performed according to OECD 201 (GLP) with the green algae Desmodesmus subspicatus. Five loading rates up to 100 mg/L (nominal) were tested in this study. The loading rates were prepared by siphoning an appropriate amount from the middle after a suitable stirring and settling period (Water Accommodated Fraction). Measured values resulted in concentrations below the Limit of Quantification (< 0.005 mg/L) for all test concentrations. No effects on the growth rate and yield resulted after an exposure of 72 h. Thus, a NOErLR (72 h) of ≥ 100 mg/L and an ErL50 (72 h) > 100 mg/L resulted.

A second GLP Guideline study is available investigating the toxicity of the read-across substance 2-octyldodecyl isooctadecanoate (CAS 93803-87-3) to aquatic algae. The study was performed according to OECD 201 with the freshwater algae Selenastrum capricornutum. Water Accommodated Fractions (WAF) of nominal 10 and 100 mg/L were prepared and tested under static conditions. A chemical analysis of the test substance concentrations in the test vessels was not possible since no applicable method could be established due to the very low water solubility to detect test concentrations. An inhibition of cell growth (31.2%) was observed after 72 h in the WAF test solution of 100 mg/L, whereas no inhibition was observed in the WAF test solution of 10 mg/L. It was reported that this effect is probably related to insoluble particles which might have adsorbed fractions of light needed for algal cell growth. However, the growth rate was not inhibited resulting in an EL50 (72 h) of > 100 mg/L and a NOELR (72 h) of ≥ 100 mg/L.

Based on the available result from two 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 short-term toxicity to aquatic algae and cyanobacteria up to the limit of water solubility.