Bronchial responsiveness and decline in FEV1 in aluminium potroom workers

We have investigated the relationship between annual decline in forced expiratory volume in one second (delta FEV1) and bronchial responsiveness (BR) in aluminium potroom workers. BR was measured in a cross-sectional study of 337 aluminium potroom workers half-way through a 6 yr follow-up study of lung function. A skin-prick test (SPT) was also performed. During follow-up the mean number of measurements of lung function (FEV1) in each subject was 6.8. Mean delta FEV1 was 21.3 ml.yr-1 (within subject SD = 30.5 ml.yr-1). Mean delta FEV1 was 57.0, 44.5 and 16.6 ml.yr-1 in subjects who had provocative concentration producing a 20% fall in FEV1 (PC20) < or = 8.0, 8.1-32.0 and > 32.0 mg.ml-1, respectively. After adjustment for gender, atopy, smoking habit, FEV1, age and familial asthma the association between BR and delta FEV1 was weakened, and was not statistically significant. A significantly accelerated decline in FEV1 with age was found. The difference in delta FEV1 between smokers and nonsmokers was 39.3 ml.yr-1, and between subjects who had a positive skin-prick test compared to subjects with a negative skin-prick test 39.6 ml.yr-1. In subjects reporting work-related asthmatic symptoms the decline in FEV1 was 43.2 ml.yr-1 greater than in asymptomatic subjects. In asymptomatic subjects, positive skin-prick test was also associated with increased delta FEV1. These data indicate that a single measurement of BR is not a predictor of delta FEV1 in aluminium potroom workers. Smoking, work-related asthmatic symptoms, and positive reaction to skin-prick test in asymptomatic workers were risk factors of increased delta FEV1.