Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Stability:

No abiotic degradation of the test item was observed. 1,3-Dihydro-4(or 5)-methyl-2H-benzimidazole-2-thione is found to be stable at 50°C at all three pH-values. Therefore it can be assumed that the test item is also stable at 25 °C and no half-life times and hydrolysis rates were calculated.

Biodegradation:

Biodegradation in water (screening test): ready biodegradability:

The ready biodegradability of the substance was determined according to OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I)). Within 28 days, a degradation rate of 0 % was determined. Based on this result, the substance is regarded as not ready biodegradable.

Biodegradation in water and sediment (simulation test):

ZMB2 dissociates to MB2 and zinc ions within seconds when a non-aqueous solution of ZMB2 is exposed to an aqueous environment.

Therefore, a read-across approach (structural analogue or surrogate) from Vulkanox ZMB2 (1,3-dihydro-4(or 5)-methyl-2H-benzimidazole-2-thione, zinc salt; CAS 61617-00-3) to Vulkanox MB2 (1,3-dihydro-4(or 5)-methyl-2H-benzimidazole-2- thione, CAS 53988-10-6) was conducted for this endpoint.

This study is concerned with the aerobic mineralisation of ZMB2 in natural surface water under controlled laboratory conditions. It was carried out according to the OECD Guideline 309 "Aerobic Mineralisation in Surface Water – Simulation Biodegradation Test”. The incubation was performed using a 14C-labelled test item [phenyl-U-14C]zinc-4- and 5-methyl-2-mercaptobenzimidazole under aerobic conditions at 12 °C in the dark. The DegT50 value of MB2 (12° C) is 12.9 days (low concentration) and 24.6 days (high concentration).

Bioaccumulation:

In accordance with Section 1 of REACh annex XI, a bioaccumulation study is scientifically unjustified. The substance can be expected to have a low pontential for bioaccumulation, because the substance has a low octanol water partition coefficient (LogPow = 0.3-0.4).

Adsorption:

The adsorption coefficient of 1,3-dihydro-4(or 5)-methyl-2H-benzimidazole-2-thione was tested according to OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC)). The adsorption coefficient of the test item is deteminined to be: log Koc = 1.9 or Koc = 79 L/kg.