Relationship of acute obstructive airway change to chronic (fixed) obstruction.

In this report of a 5-yr longitudinal study of workers at six cotton textile mills, exposure and across-shift FEV, changes were evaluated as possible predictors of the annual change in FEV, for yarn manufacturing workers. A total of 611 workers had three repeatable spirometric tests, over at least 3yr, and at least one (average of three) across-shift test, while always working the same shift. The "same shift" criterion controlled for the effect of diurnal variation. Average exposure was determined from measures of lint-free elutriated cotton dust in combination with job histories. This study found a significant association between the acute and chronic effects of cotton dust exposure. Both exposure and across-shift change proved to be significant predictors of annual change, and excess annual declines in FEV, were predicted even for exposures of 200pg/m3 and across-shift drops in FEV, of 200 ml. These results suggest that, to prevent dust-related chronic decline in lung function, current smokers should be excluded from yarn manufacturing work and exposure should be reduced below 200 pgi/m3, to approximately 100 agin3. The concept that repeated acute obstructive airways responses to an occupational exposure may lead to chronic fixed airways obstruction is certainly biologically plausible. Increased airways responsiveness, which may potentiate acute obstructive changes of the airways, was listed in the 1984 Surgeon General's report on chronic obstructive lung disease' as a putative (host) risk factor. It is also biologically plausible that repeated exposure to the putative agent will maintain an increased level of airways responsiveness in much the same way as occurs in allergic asthma with sustained exposure to the putative allergen. "Will my condition become chronic?" is one of the first questions a patient will ask, particularly if he or she perceives the symptoms of acute airways obstruction to be work-related. Whether acute and chronic airways responses which occur following a particular exposure are each related independently to the exposure, whether the first leads to the second, or whether chronic airways obstruction may arise by either route is also important in the understanding of the disease process, and ultimately in its management. Such relationships are illustrated in fig 12 Finally, if chronic airways obstruction depends on repeated acute responses, across-shift changes could be used to monitor exposed populations and evaluate environmental controls. Studies of the natural history of chronic (fixed) airways limitation-including the role, if any, of acute airways responses in its genesis-are not easy for …