The light-dependent cytotoxicity of benzo[a]pyrene: effect on human erythrocytes, Escherichia coli cells, and Haemophilus influenzae transforming DNA.

In vitro, the photodynamic compound benzo[a]pyrene (BAP) generates singlet oxygen efficiently when irradiated in organic solvents. It also photogenerates superoxide anion radical in water and can act as a photoreducing agent in the absence of oxygen. In vivo, the hemolysis of human erythrocytes, the inactivation of Escherichia coli cells representing a series of strains differing in excision repair and catalase proficiency, and the inactivation of Haemophilus influenzae transforming DNA activity were used to characterize the phototoxicity of BAP in the presence of near-UV light (290-400 nm). The results are consistent with BAP behaving as a photosensitizer that generates both superoxide and singlet oxygen, and that damages chiefly membranes. DNA does not seem to be a major target in the phototoxic reactions investigated.