1. Introduction Lung cancer is the most common cancer and leading cause of cancer mortality in
the world (1;2). In Canada, lung cancer is the leading cause of cancer mortality, with an
estimated 10,700 deaths in males (29% of the total cancer deaths) and 8600 deaths in
females (26% of the total cancer deaths) for the year 2006 (3). The five-year survival rate
for lung cancer in Canada is 16%, based on the cases diagnosed from 1995-1997 (3). The
high incidence rate and poor survival rate for lung cancer demonstrates the need for
primary prevention.
Epidemiological research has contributed greatly towards identification of the
determinants of lung cancer. One major contribution was identifying cigarette smoking as
the major causative factor for lung cancer. It is estimated that 90% (about 5/6th) of the
lung cancer cases in the United States and Canada can be attributed to smoking (4;5).
However, Doll and Peto in 1981, reported that occupational factors also contribute to the
etiology of lung cancer, attributing one-sixth of the lung cancers in men to occupational
factors (6). Other recent studies have attributed 9% of lung cancer cases to occupational
factors (7;8).
Occupational studies have contributed greatly towards the identification of many
carcinogenic substances. The first occupational carcinogen was identified by Percival
Pott in 1775, who noted an excess of scrotal cancer among chimney sweeps (9; 10). He
attributed soot deposition on the scrotum as the cause of the elevated cancer risk (10).
Asbestos has been found to contribute to the high lung cancer risk among British textile
workers and American ship yard workers (11-13). Most of the carcinogens that have been
identified in occupational settings have been associated with excess risk of lung cancer