Subchronic toxicology of butyl nitrites in mice by inhalation.

Mice were exposed by inhalation to n-butyl, iso-butyl sec-butyl or tert-butyl nitrite in a dynamic airflow chamber 7 h per day for 60 days at concentrations that caused less than 20% fatalities. Under these conditions, body-weight gain was depressed over the first 30 days by all four compounds, but returned to normal over the final 30 days for all compounds except tert-butyl nitrite. Spleen weights were increased by all four butyl nitrites, and lung weights were increased by all except sec-butyl nitrite. Kidney weights were increased by iso-butyl and sec-butyl nitrites, but decreased by the tert-butyl compound. Liver weights were increased by iso-butyl nitrite exposure and decreased by tert-butyl nitrite exposure. The results are consistent with the hypothesis that a significant aspect of butyl nitrite toxicity is due to the resultant methemoglobinemia.