“…The occurrence of emphysema is related to cumulative exposure to respirable dust, although it is also closely related to smoking and ageing [Miller and Jacobsen, 1985;Parks, 1994]. As to whether increased risk of emphysema is related to simple CWP, the findings have been inconsistent [Ryder et al, 1970;Cockcroft et al, 1982;Ruckley et al, 1984]. Our data could not provide evidence to support the hypothesis that simple CWP is a contributing factor to emphysema.…”