Silica exposure, smoking, silicosis and lung cancer--complex interactions.

BACKGROUND: Establishing a clear relationship between workplace exposures and cancer is often difficult. The latent period for cancer development can make it difficult to establish a definite cause-effect relationship. The picture is further complicated by variable job histories, concomitant exposure to other carcinogens and other factors such as genetic susceptibility and poor nutrition. The lack of accurate and detailed record keeping may potentially mask informative differences among group of workers. Removing or reducing exposures to probable and known carcinogens, however, can prevent workplace cancer. AIM: This paper gives an overview of the literature reporting investigations of the relationship between exposure to silica and development of lung cancer with a focus on the controversy concerning the roles of silicosis and smoking in the development of cancer.
METHOD: A literature search was conducted to identify epidemiologic papers on silica, silicosis and lung cancer using electronic databases (MEDLINE, PubMed, Web of Science) from 1996 onwards and paper bibliographies.
RESULTS: If silicosis were the necessary step leading to lung cancer, enforcing the current silica standards would protect workers against lung cancer risk as well. Alternatively, a direct silica-lung cancer association that has been suggested implies that regulatory standards should be revised accordingly.
CONCLUSION: Further research is needed in order to understand the complex pattern of interactions leading to lung cancer among silica-exposed workers (and cancers and workplace exposures in general) and to understand whether and to what extent other workplace lung carcinogens, total respirable dust and total surface size and age of silica particles affect the carcinogenic potential of silica. In addition, the apparent paradox of a lower lung cancer risk in some workplaces with high-level silica exposure needs further investigation.