Distribution and retention of benzo(A)pyrene in rats after inhalation.

Tritium levels in tissues of rats were determined after inhalation of tritiated benzo(a)pyrene (3H-BaP; 500 micrograms/l; activity mass median diameter, 1-2 micrometers) for 1 h. Significant amounts of radioactivity were found in the nasal turbinates, trachea, larynx, lungs, tracheobronchial lymph nodes, kidneys, and liver immediately after exposure. Lower concentrations of radioactivity were found in the brain, testes, and spleen. Clearance of radioactivity from the respiratory tract occurred in two phases; a rapid phase where 50% of the radioactivity cleared by approx. 2 h, and a slower phase that continued for about 2 days after exposure. Radioactivity in the brain, testes, and spleen remained at about the same level during the first day after exposure and then decreased slightly during the second day. Benzo(a)pyrene inhaled in this particulate form was rapidly solubilized, translocated to internal organs, and excreted primarily in feces.