The development of awareness of the carcinogenic hazard of inhaled iron.

Numerous studies have observed that workers in ferriferous industries have an elevated risk of respiratory tract neoplasia. Research at the cellular and animal model levels indicates that iron compounds, per se, are carcinogenic. However, some investigators have suggested that inhaled iron compounds are merely carriers of other carcinogens. Evidence is presented that iron apparently is a principal carcinogenic hazard in inhalation of silicon dioxide, asbestos, and tobacco smoke. Included in the discussion are unresolved questions concerning the precise role of inhaled iron as a carcinogen.