ABSTRACr In a longitudinal study of a sample of firemen in London 1006 firemen were interviewed and examined in 1976 and 895 were seen a second time 12 months later. On each occasion a Medical Research Council respiratory questionnaire was administered and forced expiratory volume in one second (FEV,) and forced vital capacity (FVC) were measured. The average levels of FEV1, FVC, and FEV,/FVC in both years compared favourably with conventional predicted values. Separate multiple regression

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... sis for the two years indicated that the FEV1 and FVC fell more rapidly in those aged over 40, and that cigarette smoking had a strong harmful effect on these measures of function. Only among men with over 20 years' service was there possibly any evidence (not statistically significant) of an effect from duration of employment. The comparatively large fall in FEVy and FVC from 1976 to 1977 was due mainly to instrumental variation. The prevalence of respiratory symptoms was higher in smokers than non-smokers and increased with the number of cigarettes smoked. This study is the first to be reported on respiratory function of firemen in the United Kingdom. Before its conception in 1975 work had been reported from the United States'-3 which suggested that respiratory function in firemen declined at a rate significantly greater than expected. Methods SAMPLE Twenty five stations were selected at random from all stations in the London Fire Brigade after stratification by geographical area, numbers of fires attended, and size of station. The selected stations were distributed throughout the 11 divisions of the brigade. The sample consisted of all 1207 men active (in May 1976) in the selected stations, about 20% of the total strength of the brigade. DATES OF THE STUDY Each participant was seen once in 1976 and again in 1977, with so far as practicable an interval of 12 months for each fireman. The study was carried out from May to October each year. . RESPIRATORY FUNCTION TESTS Forced expiratory volume in one second (FEVy) and forced vital capacity (FVC) were measured in both years using a Vitalograph dry spirometer with digital readout that was calibrated daily. The mechanism of the instrument was serviced at completion of the 1976 fieldwork. In two stations flow volume measurements were also made in each year using an integrating pneumotachograph. As circadian rhythms have been shown to affect pulmonary function in work people,4 tests were performed so far as possible at the same hour of day in each year. FEV, and FVC were measured with the fireman standing and each man performed a least five forced expiratory manoeuvres and the mean of the last three values was used in the analysis. All values were corrected to BTPS. Height in stockinged feet was measured only in 1976 and weight was determined in both years. QUESTIONNAIRE The 1966 MRC respiratory questionnaire with additional questions about exposure to smoke and part time employment was administered each year. OCCUPATIONAL EXPOSURE Measures of occupational exposure used included duration of service in the brigade, whether the firemen had ever been "punished" by smoke, and in 55 on 27 April 2019 by guest. Protected by copyright.