[Effect of fog on diurnal changes in peak expiratory flow rates in an asthmatic]

To evaluate the effects of fog on asthmatics, we analyzed the symptoms of a 45-year-old female during the foggy season and the relation between diurnal peak expiratory flow rate (PEFR) and fog and other meteorological factors. Her asthma attacks had been induced by specific smells: perfume, smoke from burning grass or industrial smoke. Two years previously, she had moved to the suburbs of Sapporo, where fog frequently occurs. From that time her asthmatic symptoms had been exacerbated, so it was suspected that the fog might have had some influence. We analyzed 251 measures of PEFR from June to August 1994. The average and standard deviation of PEFR in the absence of fog and specific smells was 403 +/- 40 L/min (n = 195). PEFR was significantly lower (p < 0.01) when it was foggy (347 +/- 60 L/min; n = 40), when specific smells were present (333 +/- 60 L/min; n = 5) and when there were both fog and specific smells (340 +/- 53 L/min: n = 11). On the other hand, there were no changes associated with other meteorological factors: barometric pressures, relative humidity, mean temperature, minimal temperature and most frequent wind direction. These results suggested that the inhalation of fog decreases PEFR and is an exacerbating factor in bronchial asthma.