Long term analysis in former workers and residents exposed to blue asbestos in an Australian mining town confirms that lung function has continued to decline nearly four decades after exposure ceased. Furthermore, smoking has not worsened the asbestosis, as once claimed.

Forced expiratory volume in one second (FEV₁), forced vital capacity (FVC), and FEV₁/FVC were significantly higher for ex-residents of Wittenoom, Western Australia—where blue asbestos was mined from 1943 to 1966—than former workers, according to comparison in a mixed effects linear regression model. Each extra year of exposure reduced FEV₁ by 0.9 ml and FVC by 1.5 ml. Younger age at first exposure predicted significantly lower FEV₁ and FVC values and so did higher exposures.

Current smokers had significantly lower lung function values than never smokers. FEV₁ declined yearly significantly faster in current smokers, but not ex-smokers, versus never smokers. FEV₁/FVC declined yearly significantly faster in all smokers versus never smokers. However, there was no statistical interaction between smoking and asbestos exposure on lung function, suggesting each is an independent risk factor.

Subjects were participants in a vitamin A programme, set up in 1990 to offset effects of asbestos exposure. Lung function and its change over time were analysed by occupational and environmental exposure from consolidated annual follow up data from 1979 to 2002 and by self reported smoking history.

The cohorts are unique in having accurate records of known exposures almost exclusively to blue asbestos. They have a greater risk of reduced lung function from fibrosis owing to asbestos exposure and smoking, but independently, it now seems.