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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:

ZMBT is an organic complex with where the relation of Zn to Sulfur bridge is considered to be ionic. Thus the MBT structure is present in ZMBT. Meanwhile MBT is often found as impurity in ZMBT with variable percentage. The dissolution of MBT determines the hazard profile of ZMBT aqueous solution; and hence a read-across approach from MBT is used to support the risk assessment of ZMBT as a worst-case.

MBT being released into the waste water and the atmosphere undergo different degradation reactions. The known reaction pathways and relevant metabolites of MBT are already described in the appendix A of the EU-Risk Assessment for CBS from 2008.These described metabolites are MBTS (CAS: 120-78-5), BT (CAS: 95-16-9), BTon (CAS: 934-34-9), MeSBT (CAS: 615-22-5).All these compounds are detected in waste water and environmental compartments; therefore they are included into the MBT risk assessment and PBT/vPvB assessment.

The assessment of PBT and vPvB is performed by comparison of the relevant intrinsic properties of MBT and its described metabolites with the criteria of the REACH regulation (Annex XIII).

PBT and vPvB criteria and the corresponding properties of MBT and its described metabolites

 Criterion  PBT criteria  vPvB criteria  MBT and its described metabolites Criterion fulfilled?
 P Half-life in marine water > 60 d, or half-life in fresh- or estuarine water > 40 d, or half-life in marine sediment > 180 d, or half-life in fresh- or estuarine water sediment > 120 d, or half-life in soil > 120 d  Half-life in marine, fresh or esturarine water > 60 d, or half-life in marine, fresh or esturarine sediment > 180 d, or half-life in soil > 180 d  Not readily biodegradable (MITI, 1992) Fast hydrolysis (CMA, 1989) The main hydrolysis products BT and BTon are persistent (EU-RAR, 2008) yes 
 B BCF > 2000  BCF > 5000  BCF of MBT <2000 (MITI, 1992) BCF of the described metabolites of MBT <2000 (EU-RAR, 2008) no 
 T Long-term NOEC for marine or freshwater organisms <0.01 mg/l    89d-NOEC (fish) = 0.041 mg/l (CMA, 1989) no 
 T CMR n.a.   Not classified as CMR no 
 T Other evidence of chronic toxicity, as identified by the classifications: T, R48, or Xn, R48 according to Directive 67/548/EEC n.a.  Not classified as T, R48, or Xn, R48 according to Directive 67/548/EEC no 

Due to the B and T criteria are not fulfilled; MBT is neither PBT nor a vPvB substance. Based on the read across approach, ZMBT is also not a PBT or vPvB substance.