EFFECT OF AIR-POLLUTANTS ON THE PULMONARY SURFACTANT SYSTEM

Air pollutants have been recognized to influence the structure and fun ction of the surfactant system. Agents that have received the most att ention include ozone, nitrogen dioxide, hyperoxia, diesel exhaust, tob acco smoke, silica and fibrous materials such as asbestos. The deleter ious effects of air pollutants on the surfactant system depend on the size of the agent, on its solubility in aqueous solutions and chemical reactivity and on its concentration and the duration of exposure. Her eby the following general rules apply: the smaller the agent's size an d the less water soluble the pollutant is, the greater the tendency to reach the alveoli during breathing. In addition, the reactivity also determines the depth of penetration into alveoli. Compounds with high reactivity such as O-3, which also fulfil the earlier rules, will. rea ct with the upper respiratory tract compared with compounds with sligh tly reduced reactivity, such as NO2, which will penetrate the alveoli. The common consequence of exposure to air pollutants is an accumulati on of surfactant phospholipids and surfactant-specific proteins in the bronchoalveolar lavage fluid. These components also are structurally altered, mainly by oxidant gases, resulting in impairment of their bio logical activity. Thus, for surfactant phospholipids, there is impaire d adsorption to the air-liquid interface due to oxidation of their fat ty acids. Also, surfactant protein A, regarded as a modulator of the s urfactant system, shows impaired functions after exposure to oxidants. It is likely that in addition to the effects described in this review not all effects are known because the molecular effects of several ke y components (e.g SP-B and C) have not been well studied.