Iron miners--a ten year follow-up.

1167 workers of Lorraine (France) iron mines, a random sample of 5600 workers aged 35 to 55 years, at work in 1975 constituted the initial cohort that was examined twice at 5-year intervals after the first examination. A questionnaire on respiratory symptoms and smoking habits (MRC questionnaire) plus questions on the work history of each participant was completed, vital capacity (VC), forced expiratory volume in one second (FEV1.0), residual volume (RV) and fractional uptake of CO (FuCO) were measured at the first examination and repeated five and ten years later. At the end of the ten year follow-up, 522 subjects were re-examined, 186 were lost to follow-up, 328 answered a mail questionnaire, and 111 had died. The total number of deaths was not different from that of the general population, but for lung cancer the standardized mortality ratio (SMR) was significantly increased (SMR = 3.7). For the miners re-examined, frequency of bronchitis and decrease of functional tests were more related to age and smoking habits than to occupation.