Oct-2-ene

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Ready biodegradability tests were conducted on two analogue substances. Although one analogue substance did not exhibit ready biodegradability in a CO₂ evolution test, a degradation rate of >41% and <42% in 28 days was 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). A second analogue substance exhibited ready biodegradability in a manometric respirometry test, with an observed degradation rate of >80.8 and <80.9% in 28 days. 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, BIOWIN 5 and BIOWIN 6) predicted that the substance “biodegrades fast”; one module (BIOWIN 4) predicted that primary degradation occurs within the timeframe of “days”. Thus, the inherent biodegradability of the substance is supported by three lines of evidence: an analogue of the substance exhibited inherent, primary degradability and significant mineralisation in a CO₂ evolution test; another analogue exhibited ready biodegradability in a manometric respirometry test; and the substance itself is not refractory to ultimate degradation as indicated by QSAR predictions based on its structural components. 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 potential concern for bioaccumulation, i.e., the experimentally-determined octanol-water partition coefficient (log K_ow) of 4.51, which is above the screening criterion (log K_ow ≤ 4.5) for both “not B” and “not vB”.  However, the bioconcentration factor for the substance (BCF = 439.2 L/kg w.w.), as predicted by a validated QSAR model (EPI Suite BCFBAF v3.01), is 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 “potentially B” and “potentially 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 lowest acute L(E)C50 value from tests conducted on an analogue substance was the 48-h EC50 in Daphnia magna, reported as 0.56 mg/L < EC50 < 1 mg/L. These results indicate that the short-term toxicity of the substance is 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” and “not T” (based on aquatic toxicity).  Based upon screening criteria, the substance is considered “potentially P” and “potentially B/vB”.  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, potentially vB).