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

Background Establishing a clear relationship between workplaceexposures and cancer is often difficult. The latent period forcancer development can make it difficult to establish a definitecause–effect relationship. The picture is further complicatedby variable job histories, concomitant exposure to other carcinogensand other factors such as genetic susceptibility and poor nutrition.The lack of accurate and detailed record keeping may potentiallymask informative differences among group of workers. Removingor reducing exposures to probable and known carcinogens, however,can prevent workplace cancer. Aim This paper gives an overview of the literature reportinginvestigations of the relationship between exposure to silicaand development of lung cancer with a focus on the controversyconcerning the roles of silicosis and smoking in the developmentof cancer. Method A literature search was conducted to identify epidemiologicpapers on silica, silicosis and lung cancer using electronicdatabases (MEDLINE, PubMed, Web of Science) from 1996 onwardsand paper bibliographies. Results If silicosis were the necessary step leading to lungcancer, enforcing the current silica standards would protectworkers against lung cancer risk as well. Alternatively, a directsilica–lung cancer association that has been suggestedimplies that regulatory standards should be revised accordingly. Conclusion Further research is needed in order to understandthe complex pattern of interactions leading to lung cancer amongsilica-exposed workers (and cancers and workplace exposuresin general) and to understand whether and to what extent otherworkplace lung carcinogens, total respirable dust and totalsurface size and age of silica particles affect the carcinogenicpotential of silica. In addition, the apparent paradox of alower lung cancer risk in some workplaces with high-level silicaexposure needs further investigation.