| Abstract: | The inhalation toxicity of peroxyacetyl nitrate (PAN) was examined in acute (single exposure), sub-acute (4-week repeated exposure) and subchronic (13-week repeated exposure) studies in rats. The 4-h LC50 was found to be 95 ppm.In the 4-week study rats were exposed to 0, 0.9, 4.1 or 11.8 ppm PAN vapour for 6 h/day, 5 days/week. Exposure to 11.8 ppm caused abnormal behaviour, growth retardation, mortality, elevated haemoglobin contents, haematocrit values and erythrocyte counts, increased lung weights and severe inflammatory changes and epithelial hyper- and metaplasia in the respiratory tract. At 4.1 ppm minimal behavioral disturbance, transient growth depression, slightly increased lung weights and mild histopathological changes in the respiratory tract were found. At 0.9 ppm no treatment-related alterations were detected.In the 13-week study rats were exposed to 0, 0.2, 1.0 or 4.6 ppm PAN vapour for 6.5 h/day, 5 days.week. Exposure to 4.6 ppm resulted in changes similar to those found at 11.8 ppm in the 4-week experiment, but no mortality occurred. At 1.0 ppm minimal irritation of the mucous membranes in the nasal cavity was the only PAN-related effect observed. No treatment- related changes were seen at 0.2 ppm. It was concluded that the no-toxic- effect level is between 0.2 and 1.0 ppm, and very probably close to the upper value. |
