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).
An epidemiological investigation was carried out to determine the relationship between silicosis in hardrock miners in Ontario and cumulative exposure to silica (free crystalline silica--alpha quartz) dust. This second report describes a side-by-side air-sampling program used to derive a konimeter/gravimetric silica conversion curve. A total of 2,360 filter samples and 90,000 konimeter samples were taken over 2 years in two mines representing the ore types gold and uranium, both in existing conditions as well as in an experimental stope in which dry drilling was used to simulate the high dust conditions of the past. The method of calculating cumulative respirable silica exposure indices for each miner is reported.
An epidemiological investigation was undertaken to determine the relationship between silicosis in hardrock miners in Ontario and cumulative exposure to silica (free crystalline silica--alpha quartz) dust. This report describes the analytic method and presents the risk estimates.
Comment In: Am J Ind Med. 1990;17(2):277-802154097
An epidemiological investigation was undertaken to determine the relationship between silicosis in hardrock miners in Ontario and cumulative exposure to silica (crystalline silica--alpha quartz) dust. This first report describes the cohort, the method of classifying the radiographs, and the identification of a case of silicosis.
This paper describes observed and expected mortality from cancers of the lung, larynx, nose, and kidney in a cohort of 54,509 nickel workers followed for 35 years. For analysis purposes the cohort was subdivided into men with and without service in one of the three high nickel dust areas of the operation: the Sinter Plants at Copper Cliff and Coniston, and the Leaching, Calcining and Sintering (LC&S) department at Port Colborne. At Copper Cliff Sinter Plant workers experienced three times the expected number of lung cancer deaths; the SMR rose steeply with increasing duration of service peaking at 943 with 10 to 15 years. A similar overall excess risk of lung cancer was seen in the smaller Coniston Sinter Plant again with an indication of an exposure risk gradient. Men in the LC&S department at Port Colborne also experienced a dose related excess risk of lung cancer death that rose to an SMR of 806 with 20 to 25 years of service. Nasal cancer deaths were increased at both the Copper Cliff Sinter Plant (6 deaths) and the LC&S department at Port Colborne (19 deaths), representing SMRs of 3,704 and 7,755, respectively, for this rare cancer. Laryngeal cancer and kidney cancer, both previously associated with nickel, were not in excess in these high risk groups. A further exploration of death from these causes in the lower exposure remainder of the cohort revealed an epidemiologically modest elevation in lung cancer death in miners (probably not nickel related) and parts of the Copper Refinery. No evidence of laryngeal cancer excess was found.(ABSTRACT TRUNCATED AT 250 WORDS)
Following the publication of the NIOSH nickel criteria document in 1977, the Joint Occupational Health Committee of the International Nickel Company (INCO) commissioned a mortality study of the company's Ontario workforce. This paper describes the detailed methodology and primary mortality results of the ensuing study; subsequent papers will describe more detailed findings of cause-specific mortality. An historical prospective mortality study of approximately 54,000 INCO workers has been conducted. Men with six months or more of service were followed for mortality during a 35-year period by computerized record linkage to the Canadian National Mortality Data Base. From a company-provided list of men known to have died and through independent follow-up of a random sample of 1,000 subjects of unknown status, we estimate a mortality ascertainment rate of 95%. Cause-specific standardized mortality ratios calculated with respect to Ontario provincial mortality rates indicate an excess of accidental deaths in men working in the Sudbury area and an excess of cancer deaths at the company's Port Colborne nickel refinery. A strong healthy worker effect was found for both all-disease mortality ad cancer mortality. The lower than expected mortality persisted for about 15 years beyond initial hiring.