Fatty acids, C16-18, stearyl esters

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to microorganisms

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

Refer to the analogue approach justification provided in IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

>= 14.2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Result of toxicity control from ready biodegradability test

Remarks on result:

other:

Remarks:

Source: RA-A, CAS 93803-87-3, Notox, 1998

Conclusions:

The key value retained for the toxicity to microorganisms is a NOEC (14 d) of ≥ 14.2 mg/L (nominal) based on an experimental study with a structurally and chemically closely related source substance (OECD 301 B); read-across

Description of key information

NOEC (14 d) ≥ 14.2 mg/L (OECD 301B, activated sludge microorganisms); read-across

Additional information

There is no experimental data available for the toxicity of the target substance Fatty acids, C16-18, stearyl esters (CAS 85536-04-5) to microorganisms.Therefore, read-across to the structurally and chemically closely related source substance 2-octyldodecyl isooctadecanoate (CAS 93803-87-3) was performed in accordance with Regulation (EC) No 1907/2006 Annex XI, section 1.5 in order to fulfill the data requirements for this substance. The source substance is characterized by similar fatty acid chain lengths and alcohol components as the target substance and is therefore considered a suitable representative for the assessment of the toxicity of the target substance to aquatic microorganisms. A detailed read-across justification in provided in IUCLID section 13.

Since no studies on the toxicity to aquatic microorganisms are available a ready biodegradability study is used to derive a NOEC for the toxicity to aquatic microorganisms. If a compound degrades well in a ready biodegradability test, or does not inhibit the degradation of a positive control at a certain concentration, this concentration can be used as a NOEC value. This approach is in accordance with the Guidance on information requirements and chemical safety assessment (Chapter R.7b: Endpoint specific guidance, ECHA, 2017).

The available biodegradation study with the source substance2-octyldodecyl isooctadecanoatewas conducted according to OECD guideline 301 B and in compliance with GLP. The test included a toxicity control, containing 14.2 mg/L test item and 39.85 mg/L reference substance. After 14 d incubation, the toxicity control attained 78.1% degradation. A substance can be assumed to be not inhibitory to aquatic microorganisms, if in the toxicity control of a ready biodegradation test, more than 25% degradation based on CO2 evolution occurred within 14 days (OECD guideline 301). Thus, the substance is not toxic to aquatic microorganisms and a NOEC (14 d) of ≥ 14.2 mg/L was derived.

Based on the high degree of structural and chemical similarity between the target and selected source substance, the target substance is expected to exhibit a similar ecotoxicological profile as the source substance. Therefore, it is concluded that the target substanceFatty acids, C16-18, stearyl esters (CAS 85536-04-5) does not have inhibitory effects on the activity of aquatic microorganisms upto its limit of water solubility (< 0.507 mg/L, 20 °C, OECD 105).