A retrospective cohort mortality study of iron ore (hematite) miners in Minnesota.

In a retrospective cohort mortality study of 10,403 Minnesota iron-ore (hematite) miners no excesses of lung cancer mortality were found among either underground (Standardized mortality ratio [SMR] = 100) or above ground (SMR = 88) miners. Yugoslav-born miners incurred a two-fold significant excess mortality for lung cancer that did not appear to be associated with their mining exposures. Significant excesses in mortality due to stomach cancer were found for both underground (SMR = 167) and aboveground (SMR = 181) miners as compared with U.S. white males. However, except among Finnish-born miners, these excesses disappeared when comparisons were made with the appropriate county rate. The apparent absence of significant radon exposure, a strict smoking prohibition underground, an aggressive silicosis control program, and the absence of underground diesel fuel use may explain why these underground miners did not appear to incur the lung cancer risk reported in other studies.