Registration Dossier
Registration Dossier
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EC number: 276-763-0 | CAS number: 72676-55-2
PBT assessment
Administrative data
PBT assessment: overall result
- PBT status:
- the substance is not PBT / vPvB
- Justification:
According to ECHA Guidance on Information Requirements and Chemical Safety Assessment Chapter R.11: PBT/vPvB assessment (Version 3.0 June 2017) a PBT assessment must take into account the PBT/vPvB properties of relevant constituents and relevant transformation and/or degradation products. Although 5,5'-Dithiodi-1,3,4-thiadiazole-2(3H)-thione undergoes non-hydrolytic transformation when exposed to a protic solvent, the transformation is more accurately described as tautomerization. Tautomers are considered to be the same compound of the parent substance; therefore, PBT Assessments of each tautomer would not be appropriate. Nevertheless a screening PBT assessment was conducted with each of the degradation products, identified by the EAWAG tool, with the US EPA EPISUITE software. None of the identified degradation products are bioaccumulable according to Biowin estimations.
Persistence (P)
In an OECD Guideline 301B study, conducted according to GLP, 5,5'-Dithiodi-1,3,4-thiadiazole-2(3H)-thione achieved 0% biodegradation after 28 days and is therefore considered as not readily biodegradable (Harlan Laboratories, Ltd, 2016).
According to Table R.11-4 of ECHA’s guidance on information requirements and chemical safety assessment chapter R11 (v3.0, June 2017, p.49), 5,5'-Dithiodi-1,3,4-thiadiazole-2(3H)-thione should be considered as potentially P or vP.
In addition, 12 of the 18 degradation products identified by the EAWAG tool are not expected to be persistent.
Bioaccumulation (B)
In a study conducted according to GLP, the partition coefficient (log Pow) of 5,5'-Dithiodi-1,3,4-thiadiazole-2(3H)-thione estimated based on the ratio of n-octanol solubility and water solubility is 1.46 at 25 ± 1°C (Intertek Pharmaceutical Services Manchester, 2016).
According to Figure R.11-4 of ECHA’s guidance on information requirements and chemical safety assessment chapter R11 (v3.0, June 2017, p.68), 5,5'-Dithiodi-1,3,4-thiadiazole-2(3H)-thione should be considered as not B and not vB.
In addition, none of the 18 degradation products identified by the EAWAG tool are expected to bioaccumulate.
Toxic (T)
As the substance does not meet the B/vB criteria, no assessment is needed on the T criterion and the substance is not considered PBT or vPvB,
Overall Summary:
According to ECHA Guidance on Information Requirements and Chemical Safety Assessment Chapter R.11: PBT/vPvB assessment (Version 3.0 June 2017) 5,5'-Dithiodi-1,3,4-thiadiazole-2(3H)-thione should not be considered as PBT or vPvB, nor its identified degradation products.
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