Smoking, carcinogen risk assessment

Cancer. The information available on the carcinogenicity of lead in occupationally exposed humans is limited in its usefulness because the lead compound(s), the route(s) of exposure, and the levels of exposure were not always reported. Furthermore, concurrent exposure to other chemical (including arsenic, particularly in lead smelters) and confounding variables, such as smoking, were often not evaluated. Therefore, the data currently available do not support an assessment of the potential carcinogenic risk of lead in humans. 

The preliminary benzopyrene experiments described in this paper have important implications in assessing carcinogenic hazards associated with human exposure to metal carcinogens. If smokers (benzopyrene is found in cigarette smoke as well as other inducers of microsomal enzymes) are exposed to metal carcinogens, the relative risks of contracting neoplasms of the respiratory systems are greater in these individuals than in those who do not smoke. 

---