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PBT assessment

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PBT assessment: overall result

Reference
Name:
di(benzothiazol-2-yl) disulphide
Type of composition:
legal entity composition of the substance
State / form:
solid: bulk
Reference substance:
di(benzothiazol-2-yl) disulphide
PBT status:
the substance is not PBT / vPvB
Justification:

PBT AND vPvB ASSESSMENT  

8.1. Assessment of PBT/vPvB Properties - Comparison with the Criteria of Annex XIII

The assessment of PBT and vPvB is performed by comparison of the relevant intrinsic properties of MBTS with the criteria of the REACH regulation (Annex XIII) as shown inTable 45. PBT and vPvB criteria and the corresponding properties of MBTS  

Table45. PBT and vPvB criteria and the corresponding properties of MBTS

 Criterion  PBT criteria  vPvB criteria  MBTS 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 (Bayer AG, 1988) yes 
B BCF > 2000 BCF > 2000 BCF of MBTS < 2000 (MITI, 1992) no
T Long-term NOEC for marine or freshwater organisms < 0.01 mg/l   Short-term and long-term studies showed no toxic effect up to water solubility. 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

8.1.1. Persistence Assessment

MBTS is not readily biodegradable with 0% degradation in 28 days (Bayer AG, 1988a) and hydrolytically stable in presence of atmospheric oxygen (Hansson & Agrup, 1993), however it can photolyse in water with a direct photolysis half-life of 3 hours at midday of August (Monsanto, 1980). The degradation products of direct photolysis were not identified, however potential metabolites such as 2-Mercaptobenzothiazol (MBT, CAS: 149-30-4), benzothiazole (BT, CAS: 95-16-9) and benzothiazolone (BTon, CAS: 934-34-9) are described in the appendix B of EU-Risk Assessment for N-Cyclohexylbenzothiazol-2-sulphenamide (CBS, CAS: 95-33-0). As the potential abiotic degradation products of MBTS and MBT, BT and BTon are resistant to both biotic and abiotic degradation.

Accordingly MBTS can be considered as provisionally persistent in the environment.

8.1.2. Bioaccumulation Assessment

The BCFs of MBTS and all of its potential metabolites are smaller than 2000, either from experiment or from estimation. Therefore MBT together with its potential metabolites does not fulfil the B criterion.

8.1.3. Toxicity Assessment

In the acute and chronic toxicity studies, no toxic effect of MBTS to three taxonomic groups from three trophic levels was observed up to the water solubility of MBTS (i.e. 0.05 mg/l at 20°C). Therefore MBTS is considered as not toxic.

Furthermore, MBTS is not classified as carcinogenic, mutagenic or toxic for reproduction. For these reasons, MBTS does not meet the T-criterion.

MBTS is hydrolytically stable (Hansson & Agrup, 1993). The transformation of MBTS to MBT (CAS: 149-30-4) requires reductive condition and the formation of benzothiazole (BT) and benzothiazolone (BTon) requires high temperature (< 60°C ) and high pH (>9); and hence these potential metabolites of MBTS are considered to be not relevant in the ecotoxicity studies of MBTS.

8.1.4. Summary and overall Conclusions on PBT or vPvB Properties

Due to the B and T criteria are not fulfilled; MBTS is neither PBT nor a vPvB substance.