1,3-dihydro-4(or 5)-methyl-2H-benzimidazole-2-thione, zinc salt

Endpoint summary

Description of key information

Acute toxicity: oral
LD50 of ZMB2 is 800 mg/kg (Bioscience Incorporated, 1977).
Acute toxicity: dermal
LD50 of ZMB2 is >2000 mg/kg bodyweight (Safepharm, 2002).
Acute toxicity: inhalation
LC50 of ZMB2 is >2.12 mg/L (Safepharm, 2003).

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

800 mg/kg bw

Quality of whole database:

2 (reliable with restrictions)

Acute toxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LC50

Value:

2 120 mg/m³ air

Quality of whole database:

1 (reliable without restriction)

Acute toxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

2 000 mg/kg bw

Quality of whole database:

1 (reliable without restriction)

Additional information

Acute toxicity - oral:

Key study:

ZMB2, when studied in male albino rats has an acute oral LD50 of 3.2 ml/kg with 19/20 Confidence Limits of from 2.5 to 4.3 ml/kg or 0.8g/kg (800 mg/kg) with 19/20 Confidence Limits of 0.63 to 1.08 g/kg (Biosearch Incorporated, 1977).

Supporting study:

In an OECD 401 study, not conducted to GLP, the acute oral LD50 to rats of ZMB2 is 390 mg/kg bw (rat, male) (Loeser, 1978).

Acute toxicity - dermal:

The acute dermal median lethal dose (LD50) of ZMB2 in the Sprague-Dawley CD strain rat was found to be greater than 2000 mg/kg bodyweight (Safepharm, 2002).

Acute toxicity - inhalation:

No deaths occurred in a group of ten rats exposed to a mean achieved atmosphere concentration of 2.12 mg/L. It was therefore considered that the acute inhalation median lethal concentration of ZMB2 in the Sprague-Dawley Crl:CD (SD) IGS BR strain rat, is greater than 2.12 mg/L (Safepharm, 2003).

Justification for selection of acute toxicity – oral endpoint
Well conducted study, equivalent or similar to OECD Guideline 401 (Acute Oral Toxicity).

Justification for selection of acute toxicity – inhalation endpoint
Well conducted study in accordance with OECD Guideline under GLP conditions. No additional studies available.

Justification for selection of acute toxicity – dermal endpoint
Well conducted study in accordance with OECD Guideline under GLP conditions. No additional studies available.

Justification for classification or non-classification

Acute toxicity - oral:

The LD50 of ZMB2 is 800 mg/kg, therefore, according to Regulation EC No. 1272/2008 on classification, labelling and packaging (CLP) of substances and mixtures the substance is classified as Category 4 (Warning) H302: Harmful if swallowed.

Acute toxicity - dermal:

The LD50 of ZMB2 is >2000 mg/kg, therefore, according to Regulation EC No. 1272/2008 on classification, labelling and packaging (CLP) of substances and mixtures the substance is not classified.

Acute toxicity - inhalation:

The LD50 of ZMB2 is >2.12 mg/L, therefore, according to Regulation EC No. 1272/2008 on classification, labelling and packaging (CLP) of substances and mixtures the substance is classified as Category 4 (Warning) H332: Harmful if inhaled.

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