[1] Italian Soc Tobaccol SITAB, Bologna, Italy
[2] Univ Perugia, Sect Occupat Med Resp Dis & Toxicol, Perugia, Italy
[3] Western Univ, Div Respirol, London, ON, Canada
[4] London Hlth Sci Ctr, Victoria Hosp, 800 Commissioners Rd East,Room E6-203, London, ON N6A 5W9, Canada