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PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Persistence(P, vP)

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.

 

Bioaccumulation (B, vB)

Bioaccumulation concentration factor (BCF) cannot not be measured for T2PHP due to its rapid hydrolysis. Given the rapid hydrolysis of this substance, there will be little opportunity for it to bioaccumulate. Estimated BCF values for T2PHP are very low. Studies also show that the primary hydrolysis product will not bioaccumulate to any significant extent. The hydrolysis products are also readily biodegradable. 

T2PHP BCF and hydrolysis product BCFs are well below the criteria for B (bioaccumulative) or vB (very bioaccumulative). As such, it is concluded that T2PHP

does not meet the criteria for B or vB.

Toxicity (T)

T2HPHP has a low order of toxicity to mammalian species. The primary effect of interest is skin sensitisation; for which it is classified.