Propane-1,2-diol, propoxylated

Biodegradation in water: screening tests

Description of key information

No test is available for ‘propane-1,2-diol, propoxylated’. However, tests with structurally related substances and constituents indicate that the substance, depending on compostion, will be somewhere between inherently and readily biodegradable.

Additional information

Physico-chemical properties of mono-, di- and tripropylene glycol reflect a homological trend. The substances are viscous liquids with high boiling points (184 ˚C for mono-, 227 ˚C for di- and 270 ˚C for tripropylene glycol), low vapour pressures (20 Pa for monopropylene glycol, 1.3 Pa for dipropylene glycol and 0.26 Pa for tripropylene glycol) and are miscible with water. The log Kow values for mono-, di and tripropylene glycol are -1.07, -0.462 and -0.379, respectively. Physico-chemical properties of ‘propane-1,2-diol, propoxylated’ in general also fit the same observed trend and are overall consistent with what could be expected based on its composition. The substance boils at ca. 254 ˚C (with possible decomposition), has a vapour pressure of 0.2 Pa at 25 ˚C, is essentially miscible with water and its low Kow lies in the range <0.3-1.13. Since the physico-chemical properties of the substances reflect a homological trend, and taking into account that the substances are structural analogues of each other, differing only in the number of propylene glycol units, it is considered acceptable to derive the data on biodegradation and aquatic toxicity for ‘propane-1,2-diol, propoxylated’ from its constituents mono-, di- and tripropylene glycol.

Taking into the available information regarding physico-chemical properties and environmental fate, it seems likely that ‘propane-1,2-diol, propoxylated’, like mono-, di- and tripropylene glycol, is biodegradable.

• Monopropylene glycol was found readily biodegradable after 28 days under aerobic conditions.
• In an OECD306 test (seawater), after 64 days 95.8 % biodegradation was observed (DOC removal) and 90.6% biodegradation was observed (CO2evolution)(West et al., 2007)
• Dipropylene glycol was found to be readily biodegradable after 28 days under aerobic conditions.
• Significant biodegradation (>20%) was found in a screening test with natural seawater after 64 days (West et al., 2007).
• Tripropylene glycol was found readily biodegradable after 28 days under aerobic conditions.
• Significant biodegradation (>20%) was found in a screening test with natural seawater after 64 days (West et al., 2007).
• Mono, di and tri propylene glycol meet the OECD definition of "readily biodegradable", and according to this definition are not expected to persist in either aquatic or terrestrial environments. The QSAR data suggests that the Tetra and Penta members may not be readily biodegradable, although they can be regarded as inherently biodegradable (West, 2014). They are not persistent and are expected to ultimately biodegrade in the environment, albeit at a somewhat slower rate that the lower members of the homologous series. Whilst the composition of 'propane-1,2-diol, propoxylated' can be such that a high proportion consists of tetraPG and pentaPG, available data supports a prediction of at least inherent biodegradability and lack of environmental persistence.