Benzimidazole-2-thiol

PBT assessment

PBT assessment: overall result

Reference

Name:

benzimidazole-2-thiol

Type of composition:

boundary composition of the substance

State / form:

solid: bulk

Reference substance:

benzimidazole-2-thiol

PBT status:

the substance is not PBT / vPvB

Justification:

Classification of Benzimidazole-2-thiol (CAS no. 583-39-1) for effects in the environment:

The test chemical Benzimidazole-2-thiol (CAS no. 583-39-1) is used in adhesives, sealants, automotive care products, and fragrances, washing & cleaning products.. The test chemical herein critically and independently evaluated for the PBT.

The aim was to assess whether the PBT criterion within Annex XIII was fulfilled forBenzimidazole-2-thiol. The PBT criterion was herein assessed based on experimental data in conjunction with standardized environmental fate models.

 

1. Persistence assessment

 

The tested substance doesn’t meet the P criterion within Annex XIII based on the assessment that here follows:

 

1.1.Overall degradability

 

All the biodegradable information available for the target chemical Benzimidazole-2-thiol(CAS no. 583-39-1), conducted using various OECD guidelines, for different exposure periods states that the test chemical can undergo degradation up to 42 % in the exposure period of 28 days, By which it is categorised into is ultimate inherently biodegradable chemical.

In conclusion, the chemical was estimated to be non-persistent in water, because of it ultimate inherently biodegradable nature

1.2Environmental fate and exposure risk

The test chemical 583-39-1 if released intentionally or un intentionally into the environmental media. It is predicted that the test chemical would mostly accumulate in the soil up to 74.4 % followed by water (24.8%) and sediment (0.36%).

 

Table 2:Summary of estimated half-life and Mackay Fugacity model (level III) in freshwater, sediment and soil by EPI suite version 4.1:

 

Medium	Predicted half-life	Mackay fugacity model level III
fresh- or estuarine water	15 days	24.8%
fresh- or estuarine sediment	135 days	0.36%
soil	30 days	74.8%

 

The test chemical, Benzimidazole-2-thiol was determined to be ultimate inherently biodegradable in nature, and all the predicted values in the various environmental compartments, suggests us that test substance could not be considered as persistent chemical.

 

2. Bioaccumulation assessment

 

The tested substance doesn’t meet the B criterion within Annex XIII based on the assessment that here follows:

I.             From section 4.7, Partition coefficient was studied based on the OECD 117 guidelines. The Reverse Phase High Performance Liquid Chromatographic method has been applied to determine the log Kow. The Log Kow value of the test chemical Benzimidazole-2-thiol was obtained to be 0.88, at 25°C and 1.6 from other databases. On the basis of this values, test chemical Benzimidazole-2-thiol can be considered to have hydrophilic nature.

J.            The Bioaccumulation study was performed using the fresh water fish, Cyprinus carpio. The exposed concentrations has shown a very low potential to get accumulate the fish i.e., 0.7 -3.5 L/kg. correspondingly, the predicted values were also low ie., 1.0-5.785. The obtained values suggests, if the test chemical is released into the water bodies it has lower tendency to get accumulate in the fishes

By relying on the data, CAS 583-39-1 chemical cannot be classified into Bio accumulative category.

 

3.    Toxicity assessment

 

The tested substance does meet the T criterion within Annex XIII based on the assessment that here follows:

 

3.1. Mammals

 

Based on available information on repeated study, the No Observed Adverse Effect Level (NOAEL) for the test chemical was determined to be less than 2 mg/Kg bw using male and female rats. Thus, the test chemical is expected to be toxic upon repeated exposure by oral route as per the criteria mentioned in CLP regulation.

Based on the available data for the assessment of repeated dose toxicity by oral, inhalation route and following Regulation (EC) 1272/2008 the test chemical is classified in STOT RE – 2 (oral) category.

 

3.2. Freshwater organisms

The effects of test chemical was studied on the aquatic ecosystem, by using fish, daphnia and algae as the experimental model. The studies on the various aquatic species revealed that the toxic values of the test chemical was ranging from 15.70 to 80.92 mg/L. Based on the obtained values it is classified as aquatic chronic 3. By considering all the data available related to the ecotoxicity endpoints, it is expected that the test chemical is will not have NOEC value below 0.01mg/L.

It can be concluded that the test chemical cannot be toxic to the aquatic ecosystem. Thus, it can be classified as non-toxic chemical as per Annex XIII for PBT classification. 

 

Overall conclusion about Persistence, Bioaccumulation and Toxicity (PBT).

Based on critical, independent and collective evaluation of information summarized herein, the tested compound didn’t meet P and B criteria. Whereas it has qualified for T criterion. However, , the tested compound has not been classified as a PBT chemical as per Annex XIII.