Octyl laurate

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:

Refer to analogue justification provided in IUCLID section 13

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

WSF

Basis for effect:

growth rate

Remarks on result:

other: Source, CAS 2306-88-9, D. subspicatus, 72 h

Duration:

72 h

Dose descriptor:

NOELR

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

WSF

Basis for effect:

growth rate

Remarks on result:

other: Source, CAS 2306-88-9, D. subspicatus, 72 h

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

WAF

Basis for effect:

growth rate

Remarks on result:

other: Source, CAS 135800-37-2, D. subspicatus, 72 h

Description of key information

No toxic effects up to the limit of water solubility; read-across

Additional information

Since no studies are available, in which the toxicity of the target substance octyl laurate (CAS 5303-24-2) to algae was assessed, read-across to the structurally related source substances Fatty acids, C8-16, 2-ethylhexyl esters (CAS 135800-37-2), octyl octanoate (CAS 2306-88-9) and decyl laurate (CAS 36528-28-6) was conducted in accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5. Based on the high degree of structural and chemical similarity, the selected source substances are considered suitable representatives for the assessment of the toxicity of the target substance to aquatic algae.A detailed justification of the analogue approach is provided in IUCLID section 13.

The experimental study with the source substance Fatty acids, C8-16, 2-ethylhexyl esters (CAS 135800-37-2) was performed according to EU-Method C.3 with filtered and unfiltered solution of 100 mg/L (Henkel, 1998). Scenedesmus subspicatus was used as test organism. The filtered solution showed no significant inhibition of algae growth or growth rate which means that the water soluble part of the test substance was not toxic. With a more or less homogenous emulsion of test material high inhibitions of algae growth and growth rate were observed (75.7% and 42.6% respectively). This observed inhibition in presence of undissolved test substance can be accounted to physical, but not to biological effects, resulting in an ErC50 (72 h) of > 100 mg/L.

The second experimental study with the source substance octyl octanoate (CAS 2306-88-9) was conducted according to OECD guideline 201 and GLP (BMG, 2013). The test organism Desmodesmus subspicatus was exposed to the test substance at a nominal loading rate of 100 mg/L, prepared as water soluble fraction (WSF), for 72 h. No significant effect on algal growth was observed. The EL50 based on growth rate was > 100 mg/L and the NOELR >= 100 mg/L.

The third experimental study for source substance octly laurate (CAS 36528-28-6) was performed according to OECD guideline 201 and GLP (Scymaris, 2017). In a static test, Pseudokirchneriella subcapitata was exposed to the five nominal test item concentrations of 0.125, 0.25, 0.5, 1.0 and 2.0 mg/L for 72 h. Since the test item was poorly soluble, a primary test item stock solution with a nominal concentration of 20 g/L was prepared in the solvent tetrahydrofuran. The final test solutions were prepared by dilution of this stock solution with culture medium. Therefore, solvent and dilution water controls were run in parallel. Effect values were determined and reported on the basis of the mean measured total concentrations, which were 0.075, 0.15, 0.27, 0.75, and 1.3 mg/L (53 – 75% of nominal concentrations). After 72 h, inhibition was less than 50% in both cases and no significant growth rate and yield inhibition was observed. Therefore, the ErC50 (72 h) and EyC50 (72 h) is considered to be greater than the highest concentration tested and is reported as > 1.3 mg/L. The reported NOEC is 1.3 mg/L for growth rate and yield inhibition and the ErC10 (72 h) and EyC10 (72 h) are both > 1.3 mg/L, respectively.

Based on the structural and chemical similarity of the target and source substances, the target substance is expected to exhibit a similar ecotoxicological profile as the source substances. Therefore, it is concluded thatoctyl laurate (CAS 5303-24-2) does not cause toxic effects on aquatic algae up to the limit of water solubility.