Propane-1,2-diyl dibenzoate

Endpoint summary

Description of key information

Key data is available for propylene glycol dibenzoate (PGDB). This data is supported by relevant information available from a structural analogue Dipropylene glycol dibenzoate (DPGDB). The justification for read across is presented as an attachment included in Section 13 of the IUCLID dossier.

Hydrolysis

In studies performed to OECD guidelines and GLP, propylene glycol dibenzoate was determined to be readily biodegradable, hydrolytically unstable under basic conditions and possibly adsorbing to soil.

Propylene glycol dibenzoate was hydrolytically stable under acidic and neutral conditions, but unstable under basic conditions with a half-life of 9 days in an OECD Guideline 111 (hydrolysis as a function of pH) test performed to GLP guidelines (Huntingdon Life Sciences, 2014b; Klimisch Score = 1).

Biodegradation

Mean oxygen consumption in mixtures containing PGDB was 7% of the theoretical value (25 mgO₂/500 mL) after 1 day, 32% after 2 days, 60% after 7 days and 81% at the end of the test (Day 28). Therefore, PGDB was considered to be readily biodegradable under the conditions of the OECD Guideline 301 F, Ready Biodegradability: Manometric Respirometry Test (Huntingdon Life Sciences, 2014c; Klimisch score = 1).

 

In a modified Sturm test (Huntingdon Life Sciences, 1998a; Klimisch score = 1), DPGDB was found to have degraded by 6% after 2 days, 62% after 12 days, and by 85% at the end of the 28 -day biotic phase of the test.

 

Substances are considered to be readily degradable in this test if CO2 production is equal to or greater than 60% of the theoretical value within ten days of the level achieving 10%. In the Modified Sturm test, DPGDB met these criteria, so may be considered to be readily biodegradable. The BOD / COD studies show DPGDB to be inherently biodegradable and the anaerobic study showed it to be anaerobically biodegradable.

In accordance with the adaptations found in column 2 of Annex IX, simulation studies of biodegradation in water, sediments and soils are waived due to the demonstrated ready biodegradation of the substance. 

Bioaccumulation

According to the adaptations found in column 2 of annex IX, the bioconcentration in aquatic species study can be waived if direct and indirect exposure to the aquatic environment is unlikely. This substance has no defined uses where direct application to the aquatic environment would occur, and because the substance is readily biodegradable, wastewater treatment would also make indirect exposure to the aquatic environment unlikely. In addition, evidence of a low bioaccumulation potential is provided by QSAR estimates showing BCF values < 100 L/kg using a regression method based upon the experimental log Kow value of 3.2, and using the Arnot-Gobas QSAR method the BCF/BAF values for all trophic levels are < 10 L/kg when biotransformation rates are utilized and ~ 200 L/kg when biotransformation is not included in the estimation. For these reasons, and for animal welfare reasons, it is believed that a bioconcentration study is not justified and is not proposed.

 

Transport and distribution

PGDB may exhibit some immobility in the soil as suggested by the soil partition coefficient ofpropylene glycol dibenzoatemeasured as 4400 (log₁₀K_oc value of 3.6) in a study performed to OECD 121 guideline (Huntingdon Life Sciences, 2014a; Klimisch Score = 1). However it was deemed readily biodegradable in the "manometric respirometry test" (OECD 301F). QSAR prediction shows that the substance has a low potential to bioaccumulate.

Dipropylene glycol dibenzoate was determined to have a log₁₀K_oc valueof 3.6 (equivalent K_oc = 3.981 x 10³) at 20°C (Huntingdon Life Sciences, 1999b; Klimisch Score = 1).