Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Stability

Hydrolysis

Key Study:

In an OECD 111 study, conducted according to GLP, transformation of 5,5'-Dithiodi-1,3,4-thiadiazole-2(3H)-thione was observed at environmental relevant pHs (pH 4, 7 and 9), however, transformation was not considered to originate from true hydrolysis,i.e.chemical breakdown due to reaction with water. Significant, extremely rapid transformation occurred prior to analysis.5,5'-Dithiodi-1,3,4-thiadiazole-2(3H)-thione is expected to undergo non-hydrolytic transformations (Envigo Research Limited, 2016).

Two reaction pathways must be considered in any experiments involving 5,5'-Dithiodi-1,3,4-thiadiazole-2(3H)-thione:

• Tautomerization; and

• Disulfide exchange.

Tautomerization should rapidly produce an equilibrium mixture of thione and thiol forms of the test substance upon exposure to a protic solvent (such as water). The position of the equilibrium will depend on temperature, solvent, and pH of the solution.

Disulfide exchange, involving the cleavage and reformation of the disulfide bridge, may be slower and the rate will depend on exposure to heat, light, and reducing or oxidizing species. Both the dimer and monomer present during this dynamic exchange will undergo tautomerization.

Biodegradation

Biodegradation in water: Screening

Key Study:

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 considered not readily biodegradable (Envigo Research Limited, 2016).

Bioaccumulation

n-octanol Partition coefficient

Key study :

The partition coefficient (log10 Pow) of the test item is estimated based on the ratio of n-octanol solubility and water solubility to be 1.46 at 25.0 +/- 1°C.

Transport and distribution

Adsorption / desorption

Key Study:

Using KOCWIN, version 2.00, September 2010 (©2000 to 2008, U.S. EPA), and taking into account the predominant anionic forms expected to be present within the environmentally relevant pH range (pH 5.5 to 7.5), the estimated adsorption coefficient (log Koc) values for 5,5'-Dithiodi-1,3,4-thiadiazole-2(3H)-thione ranges from -4.55 to 1.97. 5,5'-Dithiodi-1,3,4-thiadiazole-2(3H)-thione is expected to display high to very high mobility in soils (Harlan Laboratories Ltd, 2016).