Ventilatory function changes over a workshift.

Thirty-four production workers at three chemical plants were tested for acute changes in lung function over the course of their three-day, twelve-hour workshift. Mean percentages of the predicted lung function indices (FVC, FEV, and FEF 25-75) showed a workshift decrement, particularly evident in the evening shift. A workweek effect was shown in that no recovery in mean %FEV1 and %FEF-25-75 was shown by the last working day. Diurnal variation in respiratory function was regarded as being only partly responsible for the observed workshift effect.