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Biodegradation in water: screening tests

Description of key information

The biodegradation of this class of alkyl phosphites is expected to occur by the hydrolysis of the phosphite (abiotic degradation) into their component alcohols and then biodegradation of the alcohols. In this regard, these phosphites could generally be considered as biodegradable as their component alcohols. 2-Propylheptanol is readily biodegradable.

 

A biodegradation screening study, OECD 301D Closed Bottle Test, was performed by van Ginkel (2014) on TiTDP, a similar tris alkyl phosphite analog, to evaluate the persistence of TiTDP and also to compare the rate of biodegradation of TiTDP to that of its primary hydrolysis product – isotridecyl alcohol. The results of the new OECD 301D study found 57% degradation at 28 days, with degradation continuing to 63% degradation at 42 days. Whilst these results do not fully meet the ready biodegradable standard, they demonstrate that TiTDP is inherently biodegradable and not persistent. The rate of biodegradation of TiTDP is somewhat slower than that of isotridecyl alcohol, which does meet the ready criterion. This is probably due to the additional time needed for hydrolysis to occur and also for the greater sorption potential of the phosphite vs. the alcohol, which can also delay the biodegradation process. 

 

A new OECD 301D Closed Bottle Test was performed by van Ginkel (2019) on phenyl diisodecyl phosphite, another related alkyl phosphite analog. The results found 64% degradation at 28 da and were considered to be ready biodegradable given the complex composition of the substance.

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable

Type of water:

freshwater