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Classification & Labelling & PBT assessment

PBT assessment

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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 9.9% biodegradation. The hydrolysis test (additional consideration) indicated rapid hydrolysis at all environmentally relevant pH conditions and temperatures (i.e., at pH 4, DT50= 61 minutes at 15oC and DT50= 37 minutes at 25oC; at pH 7, DT50= 44 minutes at 15oC and DT50= 22 minutes at 25oC; at pH 9, DT50= 4.9 minutes at 15oC and DT50= 2.3 minutes at 25oC). Each of these hydrolysis half-life values is substantially below the threshold half-life of 24 hours which provides “clear evidence of environmental degradation” (Chapter R.7.b, “Endpoint-specific guidance”, Guidance on information requirements and chemical safety assessment, ECHA, 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 not sufficient to show that the degradation products resulting from hydrolysis are “not persistent” (“not P”) in the environment. The BIOWIN model predicts that the hydrolysis product of the substance (tetrapropenyl succinic acid) is not readily biodegradable, based on the results of the seven modules in the model. However, the results of the BIOWIN 3 module indicate that ultimate degradation is expected to occur in the timeframe of weeks, which does not met the screening criterion for persistence and is indicative that the substance and its hydrolysis product is not likely to be ”very persistent “(“vP”) in the environment. 

 

Therefore, no definitive determination on persistence can be made based on available information. However, in the absence of a definitive determination, the substance may be described as potentially “persistent” (“P”) and potentially “very persistent” (“vP”), based on the screening criteria for ready biodegradability, although the results of hydrolysis testing and the predictions of the BIOWIN 3 module for the hydrolysis product indicate that the substance is unlikely to be very persistent in the environment. 

 

Bioaccumulation: The experimentally-determined octanol-water partitioning coefficient for the substance (log Kow ≥ 4.39) indicates but does not clearly show that the value 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”). However, the substance has been shown to undergo rapid hydrolysis at environmentally relevant pH and temperature conditions (i.e., at pH 4, DT50= 61 minutes at 15 °C and DT50= 37 minutes at 25 °C; at pH 7, DT50 = 44 minutes at 15 °C and DT50 = 22 minutes at 25 °C; at pH 9, DT50 = 4.9 minutes at 15 °C and DT50 = 2.3 minutes at 25 °C). Each of these hydrolysis half-life values 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 partition coefficient and rapid hydrolysis of the substance, and the expected hydrophilic properties of the hydrolysis product, the substance may be determined to be “not B” and “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”, T, 48” or “Xn, R48” 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 LC50 for fish was reported at > 100 mg/L, the EC50 for daphnids (based on read-across from tripropenyl succinic anhydride, another substance in the category) was reported as > 100 mg/L, and the ErC50for algae was reported as 110 mg/L (based on cell count). Therefore, all acute toxicity L(E)C50 values were four orders of magnitude above the definitive aquatic toxicity criterion of L(E)C50< 0.01 mg/L, and three orders of magnitude above the aquatic toxicity screening criterion of L(E)C50< 0.1 mg/L. 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. 

 

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 “(potentially P, not B and presumably not T) and “not vPvB” (potentially but unlikely to be vP, not vB).