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Description of key information

ADMINISTRATION / EXPOSURE  - 5d/ 6 hours per day; Type of exposure: dynamic head-nose only vapor exposure 
RESULT: NOAEC = 1 mg/m³ air (male rats); LOAEC = 5 mg/m³ air (male rats)

Key value for chemical safety assessment

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion
Dose descriptor:
NOAEC
1 mg/m³

Additional information

No results from repeated-dose toxicity tests are available for the oral and dermal route of exposure. No subacute inhalation study according to OECD TG 412 is available. An exploratory subacute vapor inhalation study (1, 5, 15, 25 mg/m3, 5 x 6 hours/day) with male rats demonstrated obstructive and progressive lung disease (emphysema) at 25 mg/m³, which is considered to be the cause of delayed mortality. Repeated exposure of sublethal concentrations (< 15 mg/m³) did not lead to microscopic detectable adverse effects on the lung. Based on cageside observations and hypothermia a concentration of 5 mg/m³ was tolerated without toxicologically significant effects. But changes in biochemical and cellular components in bronchoalveolar lavage fluid (BALF) gave evidence for inflammations of the airways at n butyl isocyanate concentrations ¿ 5 mg/m³. Thus the reported NOAEL is 1 mg/m3; the LOAEL being 5 mg/m3 which may be in excess of what is likely to be determined after inhalation during 28 days.

Justification for classification or non-classification

In an inhalation repeated dose toxixity study were male rats were exposed to butyl isocyanate for 5 days/6 hours per day a LOAEC of 5 mg/m³ air and a NOAEC of 1 mg/m³ was found.

Due to these results a classification is not justified.

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