Triisotridecyl phosphite

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Persistence(P, vP)

A biodegradation screening study, OECD 301D Closed Bottle Test, was performed by van Ginkel (2014) on TiTDP 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.

Based on the biodegradation study and the hydrolysis information, TiTDP is not expected to meet the criteria for P or vP. The hydrolysis products of TiTDP (isotridecyl alcohol and phosphorous acid) are readily biodegradable are also do not meet the criteria for P or vP.

Bioaccumulation (B, vB)

Bioaccumulation concentration factor (BCF) cannot not be measured for TiTDP 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 TiTDP 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. 

TiTDP BCF and hydrolysis product BCFs are well below the criteria for B (bioaccumulative) or vB (very bioaccumulative). As such, it is concluded that TiTDP does not meet the criteria for B or vB.

Toxicity (T)

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

Aquatic Classification of TiTDP

A quantitative approach to assessment the aquatic hazard potential of TiTDP based on its hydrolysis products suggests that it will not be toxic to aquatic organisms. These results are due primarily to the very low water solubility of TiTDP. Since the original TiTDP REACH dossier was submitted in 2010, the registrants have learned that isotridecanol (C13 alkyl alcohol) has been self-classified as Acute Aquatic 1 (H400). Given that the aquatic hazard effect level for isotridecanol is several orders of magnitude higher than the highest estimated water solubility for TiTDP, it does not appear appropriate to carry this aquatic classification over to TiTDP. Based on the CLP regulation, the registrants are proposing to classify TiTDP as Chronic Aquatic 4 (H413). This classification is based on the fact the TiTDP is poorly water soluble, though may hydrolyze to more hazardous products in the environment