Benzene-1,2,4-tricarboxylic acid 1,2-anhydride, oligomeric reaction products with ethane- l,2-diol

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Persistence: The results from the ready biodegradability closed bottle test (screening criterion) indicated 63% biodegradation in 28 days; until test conditions, ready biodegradability was observed, although the substance was not shown to meet the 10-day window. Therefore, the substance does not fulfil the criteria for persistence and is “not P” (ECHA, Chapter R.11, PBT Assessment, Guidance on information requirements and chemical safety assessment, November 2014, Section R.11.4.1.1, p. 45). The demonstration that the substance undergoes rapid hydrolysis was based upon a weight of evidence, including a semi-quantitative stability study report of 5-Isobenzofurancarboxylic acid, 1,3-dihydro-1,3-dioxo-, reaction products with 1,2-propanediol, a structurally-similar substance based upon read-across (which estimated the hydrolysis half-life as 20 min and 15 min under neutral and acidic conditions, respectively), and a literature study based on read-across (from which the half-life for phthalic anhydride was estimated at 1.26 min at 25^oC under acidic-to-neutral conditions). Each of these hydrolysis half-life values is substantially below the threshold half-life of 24 hours which provides “clear evidence of environmental degradation” (ECHA, Chapter R.7.b, “Endpoint-specific guidance”, Guidance on information requirements and chemical safety assessment, May 2008, Section R.7.9.5.3, p. 193). Hydrolysis is the most significant abiotic degradation process, as it “may proceed effectively in aquatic, sediment and soil compartments” (Chapter R.11, “PBT Assessment”, version 1.1,Guidance on information requirements and chemical safety assessment, ECHA, November 2012, Section R.11.1.3.1, p. 19). This information is sufficient to show that the substance and its hydrolysis products are “not persistent” (“not P”) in the environment. 

Bioaccumulation: An experimentally-determined octanol-water partitioning coefficient for the substance could not be determined. During the test, the retention time of the primary peak was shorter than the retention time of the reference substance with the lowest log Kow (i.e., acetophenone, with log Kow = 1.70), indicating the substance does not exhibit the properties of a high octanol-water partitioning coefficient. This result indicates that the value likely meets the screening criterion (i.e.,log Kow ≤ 4.5) to determine that the substance is “not bioaccumulative” (“not B”) and “not very bioaccumulative” (“not vB”). Additionally, a weight of evidence demonstration shows that the substance is likely to undergo rapid hydrolysis at environmentally relevant pH and temperature conditions. This demonstration shows that the hydrolysis half-life value for the substance is substantially below the threshold half-life of 12 hours, below which “it can be assumed that the rate of hydrolysis is greater than that for uptake by exposed organisms” (Chapter R.7.c, “Endpoint-specific guidance”, Guidance on information requirements and chemical safety assessment, ECHA, May 2008, Section R.7.10.3.4, p. 24). The guidance also states that “in most cases hydrolysis products are more hydrophilic and as a consequence will have a lower potential for bioaccumulation” (Ibid.). Therefore, based on the weight of evidence regarding the octanol-water partitioning behaviour of the substance, the expected rapid hydrolysis of the substance, and the expected hydrophilic properties of the hydrolysis product, the substance may be determined to be “presumably not B” and “presumably not vB”.

Toxicity: A definitive determination regarding the mammalian toxicity of the substance indicates that the substance is not toxic. With respect to mammalian toxicity, the substance has not been classified as “carcinogenic, mutagenic or toxic for reproductive toxicant” (CMR) and has not been classified as “STOT RE” with respect to chronic exposures; these are definitive determinations of “not T” with respect to mammalian toxicity.

 

The results of the short-term aquatic toxicity tests indicate that that the substance is presumably “not toxic” (“not T”) when compared to the screening criteria for short-term aquatic toxicity.  The NOEC values for algal growth inhibition, short-term daphnid toxicity and short-term fish toxicity to trimellitic anhydride (based on read-across) were reported at 739 mg/L, 792 mg/L and 896 mg/L, respectively; due to the lack of observed toxicity, an EC₅₀or LC₅₀value could not be determined in any of the three studies. Since the substance does not exhibit the potential for bioaccumulation and has been shown to undergo rapid hydrolysis in the environment, the substance may be considered to be presumably "not T" for both acute and chronic exposures. 

 

Therefore, the substance may be considered to be “not T”. The substance is "not T" with respect to mammalian toxicity, based on definitive criteria (the substance has not been classified as “carcinogenic, mutagenic or toxic for reproductive toxicant” (CMR) and has not been classified as “STOT RE” with respect to chronic exposures). The substance is "not T" with respect to aquatic toxicity, based on the screening criterion (the lowest L(E)C50 for all three trophic levels is ≥ 0.1 mg/L). 

 

Conclusions: Any determination based on screening criteria requires that “each of the three properties persistency, bioaccumulation and toxicity need to be considered in conjunction” (Chapter R.11, “PBT Assessment”,Guidance on information requirements and chemical safety assessment, ECHA, May 2008, Section R.11.1.2.2, p. 13). Therefore, the substance is considered to be “not PBT “(not P, presumably not B and presumably not T) and “not vPvB” (not vP, presumably not vB).