Bronchial responsiveness and work-related asthma in aluminium potroom workers: effect of removal from exposure.

Twelve subjects relocated from aluminium potrooms due to work-related asthma were followed up for 2-27 months (median 23 months). Repeated post-relocation examinations (numbering 3-7, median 6) of methacholine challenge, forced expiratory volume in one second (FEV1), eosinophil cell count and respiratory symptoms were carried out at regular intervals. At the time of relocation, bronchial hyperresponsiveness (provoking concentration producing a 20% fall in FEV1 (PC20) less than or equal to 8.0 mg.ml-1) was found in eight of the subjects. During the follow-up period a twofold increase in PC20 was found in 7 of the 8 subjects who had PC20 less than 8.0 mg.ml-1 at the time of relocation. There was an improvement of symptoms but no improvement in FEV1 or decrease of eosinophils during the follow-up examinations.