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PBT assessment

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PBT assessment: overall result

Reference
Name:
4,4'-(1-phenylethane-1,1-diyl)bis(heptyloxybenzene)
Type of composition:
legal entity composition of the substance
Reference substance:
Composition 1
PBT status:
the substance is not PBT / vPvB
Justification:

Persistence:Based on a reliable ready biodegradation study for 4,4’-(1-phenylethane-1,1-diyl)bis(heptyloxybenzene) it was concluded that the substance is not readily biodegradable (5% degradation after 28 days). A reliable laboratory study (Ciric, 2016) demonstrated the potential of 4,4’-(1-phenylethane-1,1-diyl)bis(heptyloxybenzene) to adsorb or partition to sewage sludge, sediment or soil (Log Koc of >5.63).

The test item, 4,4’-(1-phenylethane-1,1-diyl)bis(heptyloxybenzene) was determined to have a very low water solubility (≤4.4 x 10-7g/L or 0.44 µg/L). In accordance with ECHA PBT Guidance (June 2017) further degradation and simulation testing is not warranted due to the technical challenges and questionable reliability that such testing would result in if conducted for substances with very low solubility. Similarly, no analytical method was available to support the hydrolysis test at such a low concentration, therefore, the hydrolysis of the substance could not be performed and the potential for abiotic degradation could not be assessed.

It is concluded that the substance is unlikely to persist in the water column, although may be considered persistent (P) or very persistent (vP) in other environmental compartments.

Bioaccumulation: The Log Kow of the test substance 4,4’-(1-phenylethane-1,1-diyl)bis(heptyloxybenzene) was determined experimentally to be >7.2. When persistence criteria are also taken into account and it is considered likely that the substance will persist in some environmental compartments, which can sometimes be a trigger for bioaccumulation testing. However, further testing is waived on the basis that it is technically unfeasible to perform a bioaccumulation study due to the very low (<1 µg/L) solubility of the substance. It is considered that the very low solubility of the test substance would mean availability and uptake of the substance from the water column would be very limited, if at all.

Based on available reliable data, it is concluded that the test substance is not B or vB.

Toxicity: Due to the very low solubility of 4,4’-(1-phenylethane-1,1-diyl)bis(heptyloxybenzene) in the test media used for all three acute toxicity tests, concentrations that may be toxic to fish, invertebrates and algae could not be reached. The water solubility of 4,4’-(1-phenylethane-1,1-diyl)bis(heptyloxybenzene) was experimentally determined to be ≤ 4.4 x 10-7g/L (or 0.44 µg/l). Reported acute toxicity values were all greater than the limit of solubility of the test substance.

The parameters for the toxicity (T) criterion are based on long-term chronic toxicity values for aquatic organisms. ECHA PBT Guidance (2017) states that acute or short-term aquatic toxicity data are considered to be screening information and may be used as an indication that the substance may fulfil the T criterion. Acute data cannot be used for concluding definitively “not T”. In this instance the lowest acute toxicity value for the test substance is the algae unbounded EC50 of > 1.4 ug/l, which may or may not be <0.1 mg/L and in a worst case scenario could be Potentially T (Figure R.11-5, ECHA PBT Guidance (2017)). However, it is considered that toxicity would be highly unlikely based on the very low solubility of the substance.

The overall conclusion is that 4,4’-(1-phenylethane-1,1-diyl)bis(heptyloxybenzene) is considered to be Potentially T (although unlikely to be toxic) and not B/vB. 4,4’-(1-phenylethane-1,1-diyl)bis(heptyloxybenzene) is unlikely to persist in the water column, although may be considered persistent (P) or very persistent (vP) in other environmental compartments.