Cohort mortality study of rock salt workers in Italy

A cohort mortality study of rock salt workers was carried out in Volterra, Italy. The occupational risk factors identified during environmental hygiene surveys were high noise levels and exposure to dusts and to chrysotile asbestos. The cohort consists of 487 subjects (367 males and 120 females) employed in the mine between 1/1/1965 and 12/31/1989. At the end of follow-up, 387 individuals were alive (295 males and 92 females), and 100 were decreased (72 males and 28 females). For two decedents, the cause of death was unknown. Regional rates were used for the computation of standardized mortality ratios (SMRs). In the entire cohort, observed mortality for all causes was similar to expected (SMR = 98, 100 obs); SMR for all cancer was 127 (41 obs); for lung cancer, the SMR was 146 (10 obs). Two cases of pleural mesothelioma, both in males, resulted in a statistically significant elevation of this cause (SMR = 741, 90% confidence interval (CI) 131-2,332). Two malignant brain tumors were detected (SMR 328, 90% CI 58-1,032); one of these was identified as a secondary neoplasm with consideration of additional clinical information. Among males, mortality for all cancers was significantly increased (SMR = 140, 90% CI 106-192). The observed mortality for malignant tumors of the digestive and the respiratory systems was higher than expected. In women, two cases of malignant ovarian cancer were observed vs. 0.42 expected on the basis of the regional rates. Increased mortality from lung and pleural tumors was consistent with the exposure to asbestos, which has also been shown to play a role in the development of ovarian tumors. The main limitations of this study were the small number of subjects and the definition of exposure solely in terms of duration of employment. Further studies of rock salt workers are needed to elucidate our findings.