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Administrative data

Description of key information

acute oral toxicity: LD50 = 360 mg/kg bw (rat, male)
acute dermal toxicity: ALD = 700 mg/kg bw (ALD = The lowest dose at which one or more animals died)
acute inhalation toxicity: LC50 = 59 mg/m³ (rat, male+female)

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion
Dose descriptor:
LD50
Value:
360 mg/kg bw

Acute toxicity: via inhalation route

Endpoint conclusion
Dose descriptor:
LC50
Value:
59 mg/m³

Acute toxicity: via dermal route

Endpoint conclusion
Dose descriptor:
discriminating dose
Value:
700 mg/kg bw

Additional information

The oral LD50 was determined to be 360 mg/kg bw for rats. Toxic symptoms included apathy, stiff gait, and labored breathings. Acute inhalation toxicity studies revealed that n-butyl isocyanate is highly toxic when inhaled. The LC50 (rat, 4h) value reported in a study according to OECD TG 403 with vapor inhalation is 59 mg/m³. Assessment of the acute inhalation toxicity data indicates that the primary toxic effects in response to exposure to evaporated n-butyl isocyanate are focused on the portal of entry, the respiratory tract. Thus death is due to severe respiratory tract lesions. Special investigations with male rats revealed overt inflammatory responses in the lung, which also could be confirmed histopathologically. The prominent microscopic changes were increased number of macrophages, perivascular round-cell infiltration, focal fibroproliferative reactions, emphysema, thickening septa, and abscessive pneumonia. Inflammation of the airways became prominent after exposure of a lethal concentration (50 mg/m³, 1x4h) and was marginally pronounced at a sublethal concentration (25 mg/m³, 1x4h)). No significant changes other than transient clinical signs were observed at 8 mg/m³. Ca. 3 mg/m³ were tolerated without any symptoms. For acute dermal toxicity only not assignable/invalid studies are available.

Justification for classification or non-classification

For the acute oral toxicity Xn, R22 is justified as a result of the LD50 = 360 mg/kg bw

For the acute inhalation toxicity T+, R26 is justified as a result of the LC50 = 59 mg/m³ air

In addition, several studies reported respiration irritational effects. Therefore R 37 is applicable

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