1,2,3-Propanetricarboxylic acid, 2-(1-oxobutoxy)-, 1,2,3-trihexyl ester

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Although the substance was not shown to be readily biodegradable within the strict timeframe, the substance has been shown to exhibit inherent, primary degradation in a sealed vessel CO₂evolution test after extended incubation (28.9% degradation in 42 days and 37.6% degradation in 56 days. In addition, ultimate degradation of the substance was demonstrated in a modified Sturm ready biodegradability assay, after extended incubation (66% ThO₂in 71 days; 74% ThO₂in 85 days). These results indicate that the substance is not persistent.

The substance has an octanol-water partition coefficient (log Kow) of > 4, indicating that the substance may exceed the screening criterion of log Kow ≥ 4.5, above which a substance may be considered to be bioaccumulative and very bioaccumulative. However, bioaccumulation of the substance in organisms through direct and indirect exposure of the aquatic compartment is unlikely based upon the following lines of evidence: (1) although the octanol-water partition coefficient (K_ow) for the substance (log K_ow˃ 4) indicates a potential concern with respect to bioaccumulation (log K_ow≥ 3), the surface tension of the substance (56 mN/m) indicates that the substance exhibits surface active properties, and therefore the partition coefficient is not an accurate predictor of the tendency of the substance to bioaccumulate; (2) the substance exhibits a low water solubility (0.61 mg/L) and is thus not likely to be available in the aquatic environment; (3) the substance has been shown to undergo inherent, primary degradation and inherent, ultimate degradability, indicating that the substance is not likely to be persistent in the environment; (4) the fish early-life stage (FELS) toxicity test on the substance has adequately evaluated the potential effects of bioaccumulation on sensitive life stages; and (5) the substance has been shown to be rapidly hydrolysed in mammals in bothin vitroandin vivostudies, attributed to the enzymatic action of carboxylesterases (specifically, B-esterases), the hydrolysis products of which do not exhibit the tendency to bioaccumulate. Therefore, the substance is not bioaccumulative.

 

This substance does not meet the definitive criteria for aquatic toxicity, as the lowest chronic NOEC or EC10value from among the three aquatic trophic levels of 0.204 mg/L (i.e., the EC10 from the 21-d assay onDaphnia magna) is substantially above the definitive criterion of NOEC/EC10 (long-term) < 0.01 mg/L for marine or freshwater organisms. The substance does not meet any of the criteria for mammalian toxicity in accordance with the CLP Regulation, i.e., carcinogenic (category 1A or 1B), mutagenic (category 1 or 1B), toxic for reproduction (category 1A, 1B or 2), or other evidence of chronic toxicity, i.e., specific target organ toxicity after repeated exposure (STOT RE category 1 or 2).  Therefore, the substance is not toxic.

Thus, the substance has been determined to be not persistent, not bioaccumulative and not toxic, and is considered to be not PBT and not vPvB.