[No public or meaningful name is available]

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Although the substance did not exhibit ready biodegradability in a CO₂ evolution test, degradation rates of 26% in 28 days and 42% in 60 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) and significant mineralisation (>40% degradation in a ready biodegradability test).  Additionally, a validated QSAR model (EPI Suite BIOWIN 4.10) predicted that the substance is readily biodegradable, based on two modules within the model: BIOWIN 3, which predicted ultimate degradation of the substance in the timeframe of “days-weeks”; and BIOWIN 5, which predicted that the substance “biodegrades fast”. Three additional modules within the model (BIOWIN 1, BIOWIN 2 and BIOWIN 6) predicted that the substance “biodegrades fast”; one module (BIOWIN 4) predicts that primary degradation occurs within the timeframe of “hours-days”. Thus, the substance exhibits inherent, primary degradability in a laboratory test and is not refractory to ultimate degradation as indicated by QSAR predictions based on structural components of the substance. 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, i.e., the predicted octanol-water partition coefficient (log K_ow) of 7.23, which is above the screening criterion (log K_ow ≤ 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.  Therefore, the octanol-water partition coefficient for the substance may not be an effective predictor of its actual bioaccumulation potential.  Additionally, the substance exhibits a low potential for aquatic exposure, based on its very low water solubility (predicted by QSAR modeling to be 0.00058 mg/L) and very strong adsorption to soils, sediment and activated sludge (i.e., the adsorption coefficient predicted by QSAR modeling is Koc = 3,211,000 L/kg or log Koc = 6.51).  The bioconcentration factor for the substance (BCF = 2,592 L/kg L/kg w.w.), as predicted by a validated QSAR model (EPI Suite BCFBAF v3.01), is above the criterion for bioaccumulative (BCF > 2000 L/kg) but below the criterion for very bioaccumulative (BCF > 5000 L/kg).  Therefore, although a definitive determination has not been made, the substance is considered “potentially 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. The NOEC values (from the acute fish toxicity test, acute daphnid immobilisation test and algal growth inhibition test) were each reported as 100% v/v saturated solution, based on a loading rate of 50 mg/L. Thus, there were no observed effects at saturation in any of the three tests.  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 vP”, “not vB” 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, potentially B, and not T based on aquatic and mammalian endpoints) and is “not vPvB” (not vP, not vB).