[Carcinogenicity in mice by inhalation of benzotrichloride and benzoyl chloride]

Benzotrichloride and benzoyl chloride are suspected to be causative agents of lung cancer and maxillary malignant lymphoma of workers employed in factories producing benzoyl chloride. The present study was undertaken to evaluate the carcinogenicity in mice of inhaling benzotrichloride and benzoyl chloride. Mice inhaled benzotrichloride and benzoyl chloride vapor for 30 min/d for 2 d/wk for 5 months, and each animal was followed for several month without subsequent exposure. Tumor developed in the lung, skin and lymphatic tissues at high incidences in mice inhaling benzotrichloride. By benzotrichloride vaporized at 50 degrees C, the incidence of pulmonary tumors was 53.1% (17/32, p less than 0.001), that of skin tumors was 25% (8/32, p less than 0.02), and that of malignant lymphoma was 25% (8/32, p less than 0.02) observed at the 10th month after exposure. These are significantly higher than that observed in control mice. In mice exposed to benzotrichloride vaporized at room temperature, the incidence of pulmonary tumors was 81.1% (30/37), that of skin tumors was 27.0% (10/37), and that of malignant lymphoma was 10.8% (4/37) observed at the 15th month after exposure. On the other hand, by benzoyl chloride vaporized at 50 degrees C, the incidence of pulmonary tumors was 10.7% (3/28) and that of skin tumors was 7.1% (2/28), but these incidences did not show any significant difference from the controls. These results suggest that the carcinogenicity of benzotrichloride is much higher than benzoyl chloride and that benzotrichloride is the primary cause of malignancies developing among workers engaged in manufacturing benzoyl chloride.