Crystalline silica, a human carcinogen, produces an increase in reactive oxygen species (ROS) when fractured in certain occupational settings compared to aged silica. The role of enhanced ROS production in carcinogenesis is not completely understood, although it has been linked to increases in apoptosis. The goal of this study was to determine the effect of exposure to freshly fractured silica compared to aged silica using a normal human cell line (HBEAS), a human adenocarcinoma cell line (H460) with altered p53 expression, and a non-small cell lung cancer cell line (H1299) deficient in p53. Following exposure to freshly fractured or aged silica, studies were performed to determine certain downstream cellular events, including ROS production, apoptosis, cell cycle and gene expression. ROS production, specifically hydroxyl radical (oOH) generation, increased significantly following exposure to freshly fractured silica compared to aged silica. The pattern of oOH generation was in parallel with DNA damage as measured by AP-site counting. Apoptosis showed comparable levels of induction with freshly fractured and aged silica in H460 and HBEAS cells. Cell cycle parameters showed a more varied response to silica for each of the cancer cell lines as compared to the normal cells, which was similar to the results of gene expression analysis. Given the similarities in response between H460 and H1299, these studies suggest a role for the increased oOH generation causing DNA damage and the induction of apoptosis without the involvement of p53, while p53 appears to play an important role in cell cycle alterations.