Acute inhalation toxicity of red phosphorus smoke

The acute inhalation toxicity of smoke generated from pure unformulated red phosphorus ignited in an air stream was investigated in male rabbits, rats, mice, and guinea pigs, exposed for 1 h. There was a wide range of 1h-LC50 values among the species. Expressed as phosphorus, they were 1689 mg/m(3) (rabbits), 1217 mg/m(3) (rat), 271 mg/m(3) (mouse), and 61 mg/m(3) (guinea pig); expressed as ortho-phosphoric acid equivalents, the values are 5337, 3846, 856, and 193 mg/m(3). In rabbits, rats, and mice that died, there were similar histopathological findings in the respiratory tract; laryngotracheal epithelial or mucosal necrosis with acute inflammatory cell infiltration, pulmonary congestion and edema, alveolar hemorrhages, alveolar wall polymorphonuclear cell infiltration bronchiolitis, and macrophage aggregations in alveoli and bronchioles. These findings are compatible with respiratory tract injury from the corrosive effects of phosphoric acids in the smoke composition. In contrast, guinea pigs at the highest lethal concentrations showed no lesions in the Larynx and trachea, and only alveolar capillary congestion in the lungs These findings are compatible with Lethal toxicity a consequence mainly of asphyxia secondary to laryngospasm in the guinea pig.