Abstract

Atmospheric fog plays some role in the production of symptoms in chronic bronchitis, but hitherto the blame has rested with pollutants rather than with the water droplet content itself. An investigation of the effects of an artificial water-containing fog at room temperature on the F.E.V._1·0 of seven patients with chronic bronchitis showed a significant reduction (mean 17·9%) as compared with a minimal or absent effect in seven out of eight normal subjects. The effect tended to persist in sensitive subjects but could be reversed by a bronchodilator. Additional experiments measuring airways resistance, total pulmonary resistance, and static and dynamic compliance tended to support the hypothesis that the fog effect is due to reflex bronchoconstriction. I suggest that water droplets, each having a finite momentum, initiate the reflex in the same manner as dust particles. Although these experiments were confined to large doses inhaled for brief intervals, it is possible that the presence of water droplets alone would increase the morbidity from atmospheric fog. Epidemiological studies on the effects of fog should include direct measurement of the water droplet content. Therapeutic aerosols might also produce this adverse effect.