Human exposure to silica dust is very common in both working and living environments. However, the potential long-term health effects have not been well established across different exposure situations. The authors studied 74,040 workers who worked at 29 metal mines and pottery factories in China for 1 y or more between January 1, 1960, and December 31, 1974, with follow-up until December 31, 2003 (median follow-up of 33 y).