A mathematical model of the penetration of polycyclic aromatic hydrocarbons through the bronchial lining layer.

The enhanced carcinogenicity of particle-associated polycyclic aromatic hydrocarbons (PAHs) has previously been explained by their prolonged retention in the lung due to the slow release of these substances from their carrier particles. However, the mathematical model presented here indicates that the lipid-aqueous heterogenic structure of the bronchial lining layer (BLL) in itself may constitute the major rate-determining step in the overall transport of PAHs from carrier particles to the bronchial epithelium. Conditions within the BLL are then as important for the resulting cellular burdens of PAHs in the lung as are the properties of the carrier particles for these hydrocarbons. Thus, in addition to other vital functions in the respiratory tract, the lipids in lung surfactant can also be important in protecting the lung from the action of lipophilic carcinogens.