A Mortality Study of 11,500 Nickel Workers2

A historical prospective mortality study was conducted at a nickel company with mines, mills, and a smelter in Ontario, Canada. All men were included in the study who worked for a total of at least 6 months and were employed at some time between 1950 and 1976. Mortality was ascertained and observed number of deaths (O) were compared with expected number of deaths (E), on the basis of the person-years method with the use of rates for Ontario males. There were 804 O compared to 743 E (P less than .001). However, the excess was more than accounted for by the increase in accidental and violent deaths (O = 242; E = 150). Deaths from circulatory diseases and all cancers were roughly equal to E. Laryngeal cancer mortality was significantly increased due to an excess in miners (O = 4; E = 1.00). Lung cancer mortality was somewhat increased (O = 46; E = 37.5); no nasal cancers were observed. Three deaths were due to pneumoconiosis. Sinter plant workers showed a significant increase of cancer deaths (O = 13; E = 6.7; P = .015).