Abstract

Background
Obstructive airways disease in aluminium potroom workers has been recognised for over 50 years. There is still controversy about whether this is true occupational asthma.

Methods
A cross-sectional survey of 379 potroom workers identified 26 subjects with symptoms suggestive of occupational asthma. Of these 26, 14 were considered by the plant physician to have occupational asthma and have a measurable PC20 methacholine. These 14 were further investigated by serial measurements of PEF at home and work, symptom diaries and measurements of methacholine reactivity before and after a three-week holiday.

Results
There was a good correlation between daily symptom scores and minimum PEF measurements; these showed changes characteristic of occupational asthma in 10 workers, with increased diurnal variation in PEF and consistent deterioration in relation to work exposure. One further record showed probable occupational asthma and two showed consistent small changes in PEF related to work exposure more in keeping with an irritant effect. Only one record was inadequate. Methacholine reactivity on a work-day was within the normal range in 13 subjects. A doubling of PC20 methacholine occurred in five of nine subjects with occupational asthma in whom repeated measurements were possible.

Conclusion
This study confirms the existence of aluminium potroom asthma. The lack of correlation with measurements of non-specific responsiveness suggests that the primary mechanism is one of hypersensitivity, perhaps enhanced by the bronchial irritants also present in the potroom.

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