Stearic acid, monoester with propane-1,2-diol

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

other: Weight of evidence

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Weight of Evidence (WoE) assessment based on structural analogues and hydrolysis products

Justification for type of information:

No data on the ecotoxicity are available for Stearic acid, monoester with propane-1,2-diol. The ecotoxicity of this substance is therefore assessed in a weight of evidence analysis based on existing data on similar compounds and hydrolysis products. See the attached report.
The environmental toxicity to algae is assessed based on existing data on:
- the group of fatty acid esters (C10-C18),
- the relevant hydrolysis products including the group of fatty acids and propane-diol.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Test data used in the weight of evidence analysis are results from studies performed according to standard guidelines.

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Test type:

static

Water media type:

freshwater

Total exposure duration:

72 h

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

19 mg/L

Remarks on result:

other: It is to be noted that all short-term effect concentrations are above the estimated water solubility of 0.0062 mg/L at 25 °C

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

12.5 mg/L

Remarks on result:

other: It is to be noted that all short-term effect concentrations are above the estimated water solubility of 0.0062 mg/L at 25 °C

Validity criteria fulfilled:

not applicable

Conclusions:

Based on a weight of evidence approach the substance is concluded to have a short-term toxicity (72h) to algae of EC50 = 19 mg/L and NOEC =12.5 mg/L

Executive summary:

Data on this endpoint are not available for “Stearic acid, monoester with propane-1,2-diol”. The environmental toxicity of this UVCB substance is therefore assessed in the present weight of evidence analysis based on existing data on:

-       the group of fatty acid esters (C10-C18),

-       the relevant hydrolysis products including the group of fatty acids and propane-diol,

-       QSAR predictions for main components (monoesters and diesters of propane-diols).

Hereby, a solid data set is available for deriving a conclusion on the environmental toxicity of the UVCB-substance.

As the substance is an UVCB-substance, and as expert assessments of substances with similar properties and structure in addition to assessments of the components in the substance and the hydrolysis products are considered the most valid method for the assessment of the environmental toxicity of the UVCB substance, an overall weight of evidence approach is used for the assessment.

Based on a weight of evidence approach the substance is concluded to have a toxicity to algae of EC50 = 19 mg/L and NOEC =12.5 mg/L

Description of key information

Test data on this endpoint are not available for “Stearic acid, monoester with propane-1,2-diol”. The short-term toxicity of this substance is therefore assessed on a weight of evidence analysis of the short-term toxicity of the components in the substance, their major metabolites, the substances used for the synthesis of the UVCB-substance.

The two main constituents of the UVCB substance are both monoester of propane-diol with octadecanoic acid (45-98%) and the monoester of propane-diol with palmitic acid (2-50%). Thus, the UVCB substance belongs to the group of fatty acid esters, and has a very similar structure to the well-known monoglycerides – the only exception being the lack of a OH-group on the C₃-carbon in the propylene glycol. The UVCB substance is assessed to be metabolised in the same manner as the monoglycerides via the formation of the fatty acid and the propylene glycol.

“Stearic acid, monoester with propane-1,2-diol” is an UVCB substance. Data on short-term toxicity to fish, aquatic invertebrate and aquatic algae and cyanobacteria as well as data on inhibition of activated sludge respiration are not available for “Stearic acid, monoester with propane-1,2-diol”. The environmental toxicity of this UVCB substance was therefore assessed based on a weight of evidence analysis.

A large set of test data on environmental toxicity have been found for the group of fatty acid esters including substances of similar structure and for the hydrolysis products of the UVCB substance to constitute a basis for conclusion on short-term toxicity of the UVCB substance.

Using the Danish QSAR database for the main constituents, QSAR predictions of short-term toxicity have been used to support and complement the test data.

As a conservative approach, the conclusions in this weight-of-evidence approach are based on the results obtained during the studies leading to the highest toxicity i.e., the lowest EC/LC50 and NOEC values respectively, leading to the following value:

Short-term toxicity to algae: 72hr-EC50= 19 mg/L; 72hr-NOEC= 12.5 mg/L (study with 1,2,3-Propanetriol, homopolymer, decanoate (C12 fatty acid ester).

It is to be noted that the short-term effect concentrations are above the estimated water solubility of 0.0062 mg/L.

The available information comprises adequate, reliable studies from reference substances with similar structure and intrinsic properties. Weight-of-Evidence is justified based on common functional group, common precursors/breakdown products. The information from these independent sources is consistent and provides sufficient weight of evidence leading to an endpoint conclusion in accordance with Annex XI, 1.2, of Regulation (EC) No 1907/2006