This paper reports a longitudinal study carried out between
1977 and 1989 to determine whether the long-term rate of
change in the forced expiratory volume in 1 second (FEV,) is
influenced by exposure to the potronm environment of an aluminum smelter. Workers with diagnosed asthma were excluded from the analysis. The study population consisted of
393 potroom workers, with rate of change in FEV, used to assess any impairment in aimay function. Postshift urinaly
fluoride levels and length of s e ~ cwee re used to measure exposure. After allowing for age, smoking behavior, and a sundardiced measure of FEV,, the rate of change in FEVl was
found to be significantly greater for those workers who had
worked shorter times in the potroom. Possible explanations for
this finding include unrecognized asthma, a healthy-worker effect, and an exposure effect that occurs early in a worker's experience in the potroom; these explanations are not necessarily mutually exclusive. Apart from the risk of occupational asthma, there does not appear to be any long-term effect on the rate of decline in FEV, associatedwith exposure to the potroom environment in workers who remain at work longer than 40 months.