Is silicosis required for silica-associated lung cancer?

Background: Abundant epidemiologic and experimental evidence supports the 1997 International Agency for Research on Cancer classification of crystalline silica as a human lung carcinogen. Nonetheless, there remains uncertainty about whether excessive lung cancer occurs exclusively among workers with silicosis.

Methods: A review was performed of published occupational epidemiologic literature directly pertinent to the interrelations among silica exposure, silicosis, and lung cancer.

Results: The association between silica and lung cancer is generally, but not uniformly, stronger among silicotics than nonsilicotics. However, the existing literature is ambiguous due to incomplete or biased ascertainment of silicosis, inadequate exposure assessment, and the inherently strong correlation between silica exposure and silicosis which hinders efforts to disentangle unique contributions to lung cancer risk.

Conclusions: Until more conclusive epidemiologic findings become available, population-based or individually-based risk assessments should treat silicosis and lung cancer as distinct entities whose cause/effect relations are not necessarily linked.