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PBT assessment

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PBT assessment: overall result

PBT status:
the substance is not PBT / vPvB

Persistence(P, vP)

There are no persistence studies on DPDP; however, there are 2 ready biodegradation studies on TPP, a close analog. Whilst the earlier screening study (Serben 2003) showed poor degradation, the results of this study may have been impacted by the low solubility of TPP. A new and enhanced biodegradation study of TPP (van Ginkel 2015) showed rapid and extensive biodegradation, meeting both the 10 -day window and overall degradation (84% in 28 days) criteria. As such, TPP can be considered as readily biodegradable and not meeting the Annex XIII criteria for persistence. It is reasonable to read these results to DPDP since it chemically very similar to TPP and it too will hydrolyse rapidly in the environment.

Based on the very short half-lives in water and the TPP ready biodegradation test results, DPDP is not expected to meet the criteria for P or vP. The hydrolysis products of DPDP (isodecanol, phenol 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 DPDP due to its rapid hydrolysis. The BCF model estimates for DPDP are generally low, though they may be of limited utility given their wide range and the fact that hydrolysis is not considered in the model. Given the rapid hydrolysis, the bioaccumulation potential of the hydrolysis products, isodecanol, phenol and phosphorous acid, were considered. All are low and well below the criterion for B (bioaccumulative) or vB (very bioaccumulative). As such, it is concluded that DPDP does not meet the criteria for B or vB.

Toxicity (T)

The primary toxicity effect is skin sensitisation; for which DPDP is classified. Based on DPDP’s low water solubility and rapid hydrolysis, it is not anticipated to cause aquatic toxicity based on the amount and relatively aquatic toxicity of its hydrolysis products. Its mains hydrolysis product, phenol, is now classified as Aquatic Chronic 2 (H411). As such, this same classification is being adopted for DPDP.

PBT/vPvB criteria and justification

DPDP is not classifiable as a PBT or a vPvB substance as it does not meet criteria for either persistence or bioaccumulation.

It should be noted that the ECB PBT Working Group review diisodecyl phenyl phosphite (DDPP), a related substance, and the conclusion from their assessment was that DDPP is not a PBT or vPvB substance based on hydrolysis. This conclusion should also be applicable to DPDP.

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