Effects of naturally-occurring acid fog on inflammatory mediators in airway and pulmonary functions in asthmatic patients

Floating fog occurs every summer in Kushiro City in Japan, and the annual a verage of fog water pH in the past 4 years has been under 5.0. We previousl y reported that epidemiologically fog was the most important positive facto r contributing to increased hospital visits of asthmatic patients compared with other meteorological values and air pollutants. This study aimed to in vestigate the mechanism of the effects of naturally-occurring acid fog on a sthmatic patients. We compared pulmonary functions and inflammatory mediato rs in induced sputum between the foggy (July 1995) and the non-foggy (May 1 996)season, and assessed airway responsiveness to hypo-osmolar aerosol. For ty-four out of 118 asthmatic patients of Kushiro City residents participate d, pulmonary function tests were completed in 36 patients, and sputum data were available in 26 patients in both seasons. Percent forced expiratory vo lume in 1 sec (FEV1) was significantly (P<0.05) decreased, and % peak expir atory flow rate (PEFR) had a trend to decrease in the foggy season more tha n in the non-foggy, and sputum eosinophil cationic protein (ECP) and interl eukin (IL)-8 were higher in the foggy season but not significantly. A moder ate inverse correlation was revealed between sputum ECP and %PEFR in the fo ggy season (r = -0.55, P < 0.005). Subjects were divided into two groups ac cording to the best PEFR; one had > 10% lower PEFR levels in the foggy seas on than in the non-foggy season (Group A, n = 7), the remainder did not (Gr oup B, n = 19). In group A, sputum ECP was significantly increased (P < 0.0 1) in the foggy season, but there were no changes in IL-8 and prostaglandin D-2. Ultrasonic nebulized distilled water provocation test revealed no dif ferences between group A and B. These results suggested that eosinophilic i nflammation rather than hypo-osmolar effect of fog might contribute to resp iratory deterioration by inhalation of naturally-occurring acid fog.