1,3-dihydro-5-methoxy-2H-benzimidazole-2-thione

PBT assessment

PBT assessment: overall result

Reference

Name:

1,3-dihydro-5-methoxy-2H-benzimidazole-2-thione

Type of composition:

boundary composition of the substance

State / form:

solid: bulk

Reference substance:

1,3-dihydro-5-methoxy-2H-benzimidazole-2-thione

PBT status:

the substance is not PBT / vPvB

Justification:

Classification of 1,3-dihydro-5-methoxy-2H-benzimidazole-2-thione for effects in the environment:

 

The chemical 1,3-dihydro-5-methoxy-2H-benzimidazole-2-thione (CAS no. 37052-78-1) is used as a pharmaceutical intermediate. The aim was to assess whether the PBT criterion within Annex XIII was fulfilled for 1,3-dihydro-5-methoxy-2H-benzimidazole-2-thione. The PBT criterion was herein assessed based on experimental data in conjunction with standardized environmental fate models. Here follows a description of the PBT assessment.

 

Persistence assessment

The tested substance does not fulfil the P criterion within Annex XIII based on the assessment that here follows:

 

Environmental fate

According to the fugacity model levels III, the most likely environmental fate for this test chemical is soil (i.e.estimated to 66.3%). In soil,1,3-dihydro-5-methoxy-2H-benzimidazole-2-thione was expected to have rapid mobility based upon a Log KOC value of 1.491, respectively. The half-life in soil (75 days estimated by EPI suite) indicates that the chemical is not persistent in soil and the exposure risk to soil dwelling animals is moderate to low.

 

If released in to the environment, 33.6% of the chemical will partition into water according to the Mackay fugacity model level III in EPI suite version 4.1 (2017). However, the half-life (37.5 days estimated by EPI suite) indicates that the chemical is not persistent in water and the exposure risk to aquatic animals is moderate to low.

 

Moreover, its persistent characteristic is only observed in the sediment compartment but Fugacity modelling shows that sediment is not an important environmental fate (less than 1% i.e. reported as 0.0978% when estimated by EPI Suite version 4.1).

 

Hence it has been concluded that 1,3-dihydro-5-methoxy-2H-benzimidazole-2-thione is not persistent (not P) in nature.

 

 

Bioaccumulation assessment

The tested substance does not fulfil the B criterion within Annex XIII based on the assessment that here follows:

 

Theestimated BCF value from authoritative database was determined to be ranges from 1 to 10.6, respectively and theoctanol water partition coefficient of the test chemical ranges was determined to be 1.52, respectively, which is less than the threshold of 4.5. If this chemical is released into the aquatic environment, there should be a low risk for the chemical to bioaccumulate in fish and food chains.

 

Toxicity assessment

The tested substance does not fulfil the T criterion within Annex XIII based on the assessment that here follows:

 

Mammals

The tested chemical is regarded to be not classified for carcinogenicity, mutagenicity and reprotoxicity, Further, there is no evidence of chronic toxicity, as identified by the classifications STOT (repeated exposure), category 1(oral, dermal, inhalation of gases/vapours, inhalation of dust/mist/fume) or category 2 (oral, dermal, inhalation of gases/vapours, inhalation of dust/mist/fume).

 

Aquatic organisms

All of the available short-term eco-toxicity data for fish, invertebrates and algae for the substance1,3-dihydro-5-methoxy-2H-benzimidazole-2-thioneindicates the LC50/EC50 value to be in the range > 50 mg/l to < 100 mg/L, respectively. These value suggest that the substance is likely to be hazardous to aquatic organisms at environmentally relevant concentrations and can be considered to be classified in ‘Aquatic chronic category 3 as per the CLP regulation.

 

On the basis ofthelong term eco-toxicity data for fish and aq. invertebrates, the NOEC value was estimated to be ranges from 8.08 to 14.24 mg/l, respectively. By speculation, long-term NOEC for aquatic organisms were not expected for the substance at concentration below 0.01 mg/L based on the data mentioned above.

 

The chemical was therefore not considered as hazardous to aquatic environments as per the criteria set out in Annex XIII.

 

Conclusion

Based on critical, independent and collective evaluation of information summarized herein, the tested compound does not fulfil the P, B and T criterion and has therefore not been classified as a PBT compound within Annex XIII.