Occupational asthma in the aluminum smelters of Australia and New Zealand: 1991–2006

OBJECTIVE: To examine the incidence of occupational asthma in the seven aluminum smelters of Australia and New Zealand from 1991 to 2006. METHODS: Incidence and exposure data were collected by survey from the smelters prospectively during the study period. RESULTS: The incidence of occupational asthma across all smelters combined was highest in 1992 at 9.46/1,000/year, declining to 0.36/1,000/year in 2006; a 96.2% reduction. The incidence of occupational asthma was correlated with geometric mean total fluoride concentration, measured as personal samples from employees undertaking anode changing (r(s) = 0.497, P < 0.001). CONCLUSIONS: The control of exposures, respiratory protection and pre-placement medical assessments undertaken during the study period seem to have contributed to the substantial decline in occupational asthma incidence.