The Significance of an Across-Shift Decrease in Vital Capacity—A Re-Analysis of a Study on Subjects Exposed to Diesel Exhaust

Abstract

Occupational exposure to diesel exhaust may develop acute as well as chronic lung function impairment. In this study, data from an earlier study on a group of subjects working at tunnel construction site were analyzed. The aini of h e analysis was lo exanline the significance of an across-shift decrease in vital capacity with concern to other lung physiological measuremcnts. There were no statistically significant differences, either in the average agc, time of employment, vital capacity before a working shift after two days of no exposure, or the distributions of smoking habits and respiratory symptoms, bctween thc eight workers who had an across-shift decrease in vital capacity and the five workers who had not. Subjects with an across-shift decrease in vital capacity had a significantly greater across-shift decrease in residual volume and total lung capacity than subjects without an across-shift dccreasc in vital capacity. Thc pathophysiological mechanisms for this across-shift decrease in rcsidual volume is not fully understood. However, an altcrcd defence mechanism in the lung may play a role for a prolonged relenlion time for the particlcs in the inhaled diesel exhaust, resulting in the across-shift decrease in residual volume. The results thus suggest that measurements of across-shift vital capacity is of importance in identifying susceptible subjects with occupational exposure to diesel exhaust.