Fundamental and applied toxicology : official journal of the Society of Toxicology

Assessment of toxicity of o-nitrochlorobenzene in rats following a 4-week inhalation exposure.

PMID 3803755


o-Nitrochlorobenzene (ONCB) is a chemical intermediate used for the synthesis of various industrial chemicals. To evaluate the subchronic toxicity of this compound, three groups of 15 male and 15 female Sprague-Dawley rats were exposed to ONCB vapor 6 hr/day, 5 days/week for 4 weeks at target concentrations of 10, 30, or 60 mg/m3. A control group of 15 animals/sex was exposed to room air in a separate inhalation chamber. Concentrations of ONCB in the chambers were determined at least three times a day using a uv spectrophotometer. Parameters monitored in this study included observation for signs of toxicity, body weights, ophthalmoscopic exam, hematology, and clinical chemistry. At necropsy, selected organ weights were recorded and over 35 tissues/animal were examined microscopically for all control and high-exposure level animals. No mortality was observed in this study. Mean body weights of all groups were comparable to controls. Animals exposed to the mid and high concentrations of ONCB showed a significant increase in blood methemoglobin and a significant decrease in hemoglobin, hematocrit, and red blood cell counts. Spleen and liver weights (absolute and relative to body weight) were significantly increased for these two groups. Microscopic changes, observed only in the spleen, included increased degree of extramedullary hematopoiesis and hemosiderosis. These data suggest that the toxicity of ONCB is comparable to that of its structural analog, p-nitrochlorobenzene. Thus these two compounds should have similar work-place exposure limits.

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