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

Biodegradation in water: screening tests

Description of key information

Readily biodegradable: ≥60% in 28 days

The hazard assessment is based on the currently available data. New studies with the registered substance and/or other member substances of the glycol esters category will be conducted in the future. The finalised studies will be included in the technical dossier as soon as they become available and the hazard assessment will be re-evaluated accordingly.

For further details, please refer to the category concept document attached to the category object (linked under IUCLID section 0.2) showing an overview of the strategy for all substances within the glycol esters category.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

The hazard assessment is based on the currently available data. New studies with the registered substance and/or other member substances of the glycol esters category will be conducted in the future. The finalised studies will be included in the technical dossier as soon as they become available and the hazard assessment will be re-evaluated accordingly.

For further details, please refer to the category concept document attached to the category object (linked under IUCLID section 0.2) showing an overview of the strategy for all substances within the glycol esters category.

 

One study is available evaluating the biodegradability of the UVCB substance isooctadecanoic acid, monoester with propane-1,2-diol (CAS 68171-38-0) according to the OECD Guideline 301 B and GLP. Surface water was used as inoculum, at a final concentration of 100 mL/L media. The microorganisms were exposed to concentrations of 12.9 and 25.8 mg/L test material for 28 d. A functional, inoculum and toxicity control were run in parallel. The CO2 evolution was measured at regular intervals in order to monitor the biodegradation of the substance. Isooctadecanoic acid, monoester with propane-1,2-diol biodegraded readily at the concentration of 12.9 mg test item/L (82.9% biodegradation after 28 d). At the higher concentration of 25.8 mg test item/L, 44.2% of the substance biodegraded after 28 d. The inoculum used in this study was surface water yielding lower cell densities compared to activated sludge that is normally used for the biodegradation studies according to OECD 301 B. Furthermore the test item concentration of 25.8 mg/L (corresponding to 25.2 mg/L total carbon in the vessel) slightly exceeds the total carbon concentration recommended by the guideline (10 – 20 mg/L TOC). Therefore, it is suspected that the cell numbers – test item ratio was not optimal and appropriate in the 25.8 mg test item/L treatment to test the biodegradability of the substance. Additionally the test item bears a very low water solubility, which could have affected the bioavailability of the substance to microorganisms at the higher concentration of 25.8 mg test item/L. Therefore the result obtained by the vessel containing the 12.9 mg test item/L was considered as key and the substance is regarded as readily biodegradable.

 

In order to support this result read across data from the analogue substances decanoic acid, mixed diesters with octanoic acid and propylene glycol (CAS 68583-51-7), propylene glycol diisostearate (CAS 68958-54-3) and butylene glycol dicaprylate / dicaprate (CAS 853947-59-8), were used within the frame of a weight of evidence. These substances bear very similar physicochemical parameters to the target substance and are characterized by similar fatty acid chain lengths as well as alcohol components. All source substances are readily biodegradable and support the fact that isooctadecanoic acid, monoester with propane-1,2-diol (CAS 68171-38-0) will be readily biodegradable by microorganisms. Read across was performed in accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5.

 

The study with the source substance decanoic acid, mixed diesters with octanoic acid and propylene glycol (CAS 68583-51-7) was conducted according to the EU Method C.4-C (GLP) under aerobic conditions using domestic activated sludge as inoculum (1995). A mean biodegradation of 82% was recorded after 28 d. The substance reached the biodegradation pass level of > 60% within the 10-day window and therefore considered as readily biodegradable.

 

The biodegradation potential of the source substance butylene glycol dicaprylate / dicaprate (CAS 853947-59-8) was tested according to OECD Guideline 310 and GLP using 10% mixed liquor supernatant from a sewage works as inoculum (1997). 79.4% biodegradation was recorded after 28 d and the substance passed the expected biodegradation level (> 60%) within the 10-day window. Therefore the substance was considered readily biodegradable. 

 

A further test with the source substance butylene glycol dicaprylate / dicaprate (CAS 853947-59-8) is available. The study was conducted according to the EU Method C.4-C and GLP (1997). Domestic activated sludge was used as inoculum. > 60% of the substance was biodegraded within the 10-day window while a biodegradation of 87% was recorded after 28 d revealing that the substance is readily biodegradable.

 

The data obtained in the study with 12.9 mg/L isooctadecanoic acid, monoester with propane-1,2-diol (CAS 68171-38-0) in combination with the appropriate read across data, reveal in a weight of evidence approach that the substance is readily biodegradable.