1,3,4-Thiadiazolidine-2,5-dithione, reaction products with tert-dodecanethiol and hydrogen peroxide

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Criteria for assessing PBT properties are defined in Annex XIII, REACH Regulation (EC) No. 1907/2006. Further details are laid down in ECHA Guidance on Information Requirements and Chemical Safety Assessment; Chapter R.11: PBT Assessment (May 2008). The assessment of PBT / vPvB properties is based upon a separate assessment for each parameter (i.e. P or vP, B or B and T). Substances are only assigned as PBT or vPvB when they fulfil the criteria for all three properties (persistency, bioaccumulation and toxicity in case of PBT substance) or both criteria (i.e. very persistent and very bioaccumulative) in case of vPvB, respectively.

Experimental results from the short-chain homologue '1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-nonanethiol' (CAS 91648 -65 -6) were also taken into account as supporting information in order to complete the PBT/vPvB assessment for the target substance '1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-dodecanethiol' (no CAS#, no EC#). This procedure is reliable; for justification, please refer to the Read-Across Statement (appended in section 13). Thus the same conclusions regarding PBT properties are drawn for the registered substance. In the following, the read across procedure is not mentioned separately, however, the assessment applies to the target as well as to the read-across substance.

Due to results of ready-biodegradability tests '1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-dodecanethiol'is considered as persistent (P), but not very persistent (not vP). The B criterion (bioaccumulative substance) is not fulfilled, due to the experimentally determined logPow of > 9.4 (at 30°C) and predicted Bioconcentration factor (BCF) below the trigger value of 2000 L/kg (3.16 L/kg wet-wt). Due to the lack of a long-term toxicity potential, also the T criterion is not fulfilled. Furthermore, no classification exists as carcinogenic, mutagenic or toxic for reproduction according to Regulation (EC) No. 1272/2008. The test substance is neither classified as "T, R48" or as "Xn, R48" based on the criteria laid down in Directive 67/548/EEC nor as STOT RE category 1 or 2 so far.

As conclusion, '1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-dodecanethiol' fulfils only one relevant criterion (persistency). Therefore, making all allowances for regulatory parameters available, the substance is neither PBT nor vPvB.

Likely routes of exposure:

Neither direct nor indirect exposure of the UVCB substance '1,3,4-Thiadiazolidine-2,5-dithione, reaction products with hydrogen peroxide and tert-dodecanethiol' to the environmental compartment is intended. Workers may be exposed via the dermal route due to substance handling during manufacture. Based on the substance specific properties (i.e. logPow > 9.4) the substance will be able to diffuse into the dermis but no deeper layers of the skin, i.e. neither the epidermis nor any bloodstream layers will be crossed. Based on the low vapour pressure of the substance, an uptake via the inhalative route is not relevant. Oral exposure is not relevant based on the handling, education and safety precautions in the factory. As conclusion, only the dermal exposure route may be relevant for humans.