Docosyl stearate

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to microorganisms, other

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:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks on result:

other: Source, CAS 36078-10-1, Dako, 2012, activated sludge microorganims

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks on result:

other: Source, CAS 36078-10-1, Dako, 2012, activated sludge microorganisms

Conclusions:

The key values for the toxicity to activated sluge microorganisms are a NOEC (3 h) of ≥ 1000 mg/L (nominal), based on experimental data with two structurally and chemically closely related source substances (OECD 209, activated sludge).

Description of key information

NOEC (3 h)>= 1000 mg/L (OECD 209, read-across)

Additional information

Since no studies are available investigating the toxicity to microorganisms of Docosyl stearate (CAS 21443-03-2) 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 microorganisms. 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 microorganisms.

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) to activated sludge microorganisms was performed according to OECD 209 using activated sludge from a predominantly domestic sewage treatment plant. A limit test with a nominal concentration of 1000 mg/L was performed for 3 h. The respiration rate of activated sludge microorganisms was not inhibited resulting in a NOEC (3 h) of ≥ 1000 mg/L. Thus, it can be concluded that no toxicological effects of dodecyl oleate on microorganisms are expected.

Furthermore a biodegradation test conducted according to OECD guideline 301B is available as supporting study investigating the effects of the read-across substance 2-octyldodecyl isooctadecanoate (CAS 93803-87-3) (Desmares-Koopmans, 1998). The test includes a toxicity control, which contains 14.2 mg/L of the test substance and 39.85 mg/L of the reference material. The toxicity control attained 78.1% degradation after 14 days of incubation. Hence, the substance is not toxic to aquatic microorganisms and a NOEC (14 d) of ≥ 14.2 mg/L was derived.

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 inhibit the degradation process in sewage treatment plants.