Registration Dossier

Classification & Labelling & PBT assessment

PBT assessment

Currently viewing:

Administrative data

PBT assessment: overall result

PBT status:
the substance is not PBT / vPvB
Justification:

Although the substance did not exhibit ready degradability in a ready biodegradability CO2 evolution test, degradation rates of 21.8% in 28 days and 25.6% in 47 days were observed. In accordance with ECHA guidance, the observed degradation rate is evidence of inherent, primary degradability (i.e., degradation of 20% or more in a biodegradability assay).  Additionally, a validated QSAR model (EPI Suite BIOWIN 4.10) predicts that while the substance is not readily biodegradable, four modules within the model (BIOWIN 1, BIOWIN 2, BIOWIN 5 and BIOWIN 6) predict that the substance “biodegrades fast”; one module (BIOWIN 3) predicts that ultimate degradation occurs within the timeframe of “weeks-months” and another (BIOWIN 4) predicts that primary degradation occurs in the timeframe of “days”. Thus, the substance exhibits primary degradability and is not refractory to ultimate degradation. Therefore, although a definitive determination has not been made, the substance is considered “potentially P” and “not vP”.

Aquatic bioaccumulation testing was not conducted on the substance, and therefore the bioaccumulative properties of the substance cannot be definitively determined. One screening-level datum indicates that the substance may be of potential concern for bioaccumulation; this datum is the predicted octanol-water partition coefficient (log Kow) of 9.39, which is above the screening criterion (log Kow ≤ 4.5) for both “not B” and “not vB”. However, this estimated value is a “very high” value (i.e., log Kow > 6). For substances with a very high partition coefficient, a decreasing relationship between log Kow and bioconcentration factor (BCF) is observed; ECHA guidance states that the “aquatic BCF of a substance is probably lower than 2000 if the calculated Log Kow is higher than 10” (ECHA, Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.11: PBT/vPvB assessment, Version 2.0, November 2014, Section R.11.4.12, p. 55). It is therefore expected that the aquatic BCF of the substance is lower than 5000 L/kg, the criterion above which a substance is determined to be very bioaccumulative. Additionally, the substance exhibits a low potential for aquatic exposure, based on its very low water solubility (experimentally determined to be < 0.1 mg/L, and predicted by QSAR modeling to be 1.868E-05 mg/L) and strong adsorption to soils, sediment and activated sludge (i.e., the adsorption coefficient predicted by QSAR modeling is log Koc = 5.4014). The bioconcentration factor for the substance (BCF = 227.7 L/kg w.w.) predicted by a validated QSAR model (EPI Suite BCFBAF v3.01) is substantially below the criteria for both bioaccumulative (BCF > 2000 L/kg) and very bioaccumulative (BCF > 5000 L/kg).  Therefore, although a definitive determination has not been made, the substance is considered “not B” and “not vB”, based upon multiple lines of evidence (including laboratory studies and QSAR modeling). 

The evaluation of short-term aquatic toxicity tests indicates that the substance does not exhibit aquatic toxicity. Values of 96-h LC50 > 1000 mg/L, 48-h EL50 > 100 mg/L and 72-h ErL50 > 100 mg/L were reported from acute fish toxicity, acute daphnid toxicity and algal growth inhibition assays, respectively, conducted on an analogue substance through read-across. These results indicate that the short-term toxicity of the substance is substantially above the screening criteria below which a substance is considered to exhibit potential aquatic toxicity (EC50 or LC50 < 0.1 mg/L) or may be definitively determined to exhibit aquatic toxicity (EC50 or LC50 < 0.01 mg/L). 

The substance does not exhibit the properties of a carcinogenic, mutagenic or reproductive toxicant (CMR), nor does the substance exhibit specific target organ toxicity in a repeated-dose study (STOT-RE). These results provide a definitive determination that the substance is not toxic with respect to mammalian endpoints.

 

Therefore, although a complete definitive determination cannot be made with respect to all endpoints, it has been shown by definitive data that the substance is “not T” (based on mammalian toxicity) and by multiple lines of evidence that that the substance is “not P”, “not vP”, and “not T” (based on aquatic toxicity). It is not necessary to have definitive criteria for all five endpoints to make the determinations as to whether the substance is “not PBT” and “not vPvB”. The determination only 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, Version 1.1, ECHA, November 2012, Section R.11.1.2.2, p. 15).

 

In summary, based on data available to date, the substance is “not PBT” (potentially P, not B, and not T based on aquatic and mammalian endpoints) and is “not vPvB” (not vP, not vB).