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

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

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 are available on the ready biodegradability of Stearic acid, monoester with propane-1,2-diol. The ready biodegradability of this substance is therefore assessed in a weight of evidence analysis based on existing test data on similar compounds as well as hydrolysis products. See attached report.

The data set for assessment of the ready biodegradability of the substance is based on
-existing data on the group of fatty acid esters,
-existing data on the relevant hydrolysis products including the group of fatty acids and propane-diol,
-QSAR predictions for main components (monoesters and diesters of propane-diols).

Qualifier:

no guideline followed

Principles of method if other than guideline:

The conclusion is based on a collection of data which were generated based on relevant guidelines. Please refer to attached weight of evidence document.

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Duration of test (contact time):

28 d

Key result

Parameter:

other: The substance is concluded to be readily biodegradable based on weight of evidence

Sampling time:

28 d

Remarks on result:

other: Based on weight of evidence

Details on results:

Test data on ready biodegradability are reported for di- and triglycerol fatty acid esters, for sorbitan monoester of stearic acid and for ethylene diester of stearic acid. All data conclude readily biodegradability
Results from studies on ready biodegradability of salts from stearic acid and from C20-22 fatty acid demonstrate that the salts are and thus the acid is readily biodegradable. The biodegradability of propane-1,2-diol (propylene glycol) in aerobic environments is in general reported to be rapid.
QSAR predictions on ready biodegradability of the main components (monoesters of propane-diols) using the Danish QSAR database and the EPI Suite program have been used to support and complement the test data. Only the diester of stearic acid failed the criteria for ready biodegradability in the QSAR predictions. The component comprises less than 10% of the UVCB substance. However this is not considered to have impact on the readily biodegradability of the substance as the diester is subject to hydrolysis where after the hydrolysis products will be biodegraded.

Validity criteria fulfilled:

not applicable

Interpretation of results:

readily biodegradable

Conclusions:

Based on a weight of evidence approach the substance is concluded to be ready biodegradable

Executive summary:

“Stearic acid, monoester with propane-1,2-diol” is an UVCB substance. Several test data on ready biodegradability of similar substances within the group of fatty acid esters, the hydrolysis products including the group of fatty acids and propane-diol are available all concluding readily biodegradability. Hereby, a huge data set is available for deriving a conclusion on the ready biodegradability of the UVCB-substance.

QSAR predictions on ready biodegradability of the main components (monoesters of propane-diols), using the Danish QSAR database and the EPI Suite program, have been used to support and complement the test data.

Both the test data and the QSAR predictions support that “Stearic acid, monoester with propane-1,2-diol” should be considered as readily biodegradable.

Based on the studies available for the group of fatty acid monoesters and diesters, the relevant hydrolysis products and the components of the UVCB substance, it is concluded that “Stearic acid, monoester with propane-1,2-diol” is readily biodegradable.

Description of key information

Test data on this endpoint are not available for “Stearic acid, monoester with propane-1,2-diol” (PGMS). The ready biodegradation of this substance is therefore assessed based on a weight of evidence analysis of the ready biodegradability of the components in the substance and their major metabolites. 

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.  

Several test data on ready biodegradability of similar substances within the group of fatty acid esters, the hydrolysis products including the group of fatty acids and propane-diol are available all concluding readily biodegradability. Hereby, a huge data set is available for deriving a conclusion on the ready biodegradability of the UVCB-substance. 

QSAR predictions on ready biodegradability of the main components (monoesters of propane-diols) using the Danish QSAR database, Leadscope, and the EPI Suite program have been used to support and complement the test data.  

Both the test data and the QSAR predictions support that “Stearic acid, monoester with propane-1,2-diol” should be considered as readily biodegradable. Only the diester of stearic acid failed the criteria for ready biodegradability in the EpiSuite predictions but was found to be readily biodegradable in the Leadscope predictions.  

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 and 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.  

Therefore, it is concluded that “Stearic acid, monoester with propane-1,2-diol” is readily biodegradable. 

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater