Figure IV-2 Relation between additional lung-cancer frequency and cumulative radiation exposure in three groups of Czechoslovakian uranium miners by time course of exposure accumulation see text.
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Source: Kunz et al. An earlier report 28 of follow-up through is the only report on the cohort of Czechoslovakian uranium miners that provided observed and expected mortality rates per 10, Ontario Uranium Miners A retrospective cohort study of Ontario miners 37 — 39 engaged in various types of mining included a subcohort of gastric cancer incidence miners who met the following criteria: received a miner's physical examination required annually by the company any time in — uranium mining began in in Ontario ; worked at gastric cancer incidence 1 month as an underground uranium miner; and had not worked in a job with any known asbestos exposure, in uranium processing except in millsor in any uranium mining in another province as an employee of Eldorado Nuclear.
Radon-daughter exposure was estimated by different methods for and earlier and for and later. For and later, exposure records of WLM maintained by the mining companies were used.
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The standard or lower WL values were the averages of the four quarterly averages or gastric cancer incidence 4-month averages gastric cancer incidence a particular year. To calculate the special or upper WL values, the investigators weighted the average of the four highest quarterly measurements or the three highest 4-month measurements in headings, stoops, and raises a total of 12 or 9 measurements, respectively by 0.
The difference between the gastric cancer incidence and special WL values varied with mine and year; 38 for some mines in some years, the special and standard values were equivalent, but the special values were up to 4 times the standard WL estimates in the years and mines for which both were available.
During —, 13, measurements were taken Table IV For one large mine, WL data for the 4 yr fromwhen the mine started operating, through had to be rejected, because they were shown to be unreliable.
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The values for the missing years were estimated by taking into account tonnage mined, ventilation, and dust concentrations at various times. Work-history gastric cancer incidence was obtained primarily from records of pre-employment and yearly examinations carried out by Ontario government agencies, 38 Additional information related to the first 5 yr of employment in the mining industry was collected from work-history cards.
The WLM values for — were calculated by combining the work-history information with a matrix of annual WL values for each mine in each year. No estimates of WL were made for prior gold-mining experience, but persons with such experience were analyzed separately, because Ontario gold miners were at increased risk of lung cancer. Because the WL measurements did not cover the complete working experience of the cohort, some estimation gastric cancer incidence exposures before was necessary.
These years included the period of highest exposures and, as Muller et al. For one large mine, this percentage includes extrapolation up to The period of extrapolation weighted by WLM is, however, less than 2 yr.
Follow-up through was carried out by computer gastric cancer incidence with national mortality data gastric cancer incidence combined with manual cross-checking to resolve problems. The investigators did not report on the percentage lost to follow-up or gastric cancer incidence the percentage of death certificates not obtained.
However, on the basis of a sample of known deaths, 6. Death certificates were the only source of information on cause of death. Using the modified life-table technique, Muller et al. Gastric cancer incidence for causes of death other than lung cancer were available only for — The authors did not have information on cigarette-smoking habits of the miners.
The mean cumulative WLM of miners with no previous gold-mining experience was 40 lower estimate to 90 upper estimate. All other descriptions of the cohort included those who had previously mined gold.
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The median year of birth of the cohort wasand the median year first employed in a mine in Ontario was ; thus, the median age at first employment in a mine in Ontario was probably about 25 yr. The median duration of work in a mine was 1.
Among uranium miners without any gold-mining experience, Muller et al. When the upper estimated gastric cancer incidence were used, the first definite gastric cancer incidence occurred at a cumulative WLM of — mean,with 14 observed and 6. When the lower estimated exposures were used, there was a definite excess at a cumulative WLM of 40—70 mean, 53with 13 observed and 7.
Muller et al. A 5- and yr exposure lag did not change the slope of the relative-risk model 0. However, dose-response analysis for two age groups of PYAR indicated that the slopes for the relative-risk model were age-independent, whereas the slopes for the excess risk model were not.
Eldorado Uranium Miners Howe et al. The cohort was identified from company employment and payroll records.
The authors were unable to detect any bias due to these exclusions. Follow-up from through was carried out by linkage with a national gastric cancer incidence data base. Only one person was lost to follow-up.
Different approaches were used for and earlier years and for and later years. For and earlier, the WL estimates were based on all available measurements of radon and radon daughters Table IV Equilibrium between radon and gastric cancer incidence daughters was estimated by comparing paired measurements of radon and radon-daughter concentrations.
When paired measurements were unavailable for a particular year, the average of the equilibrium factors for adjoining years was interpolated.
Because the distribution of measurements was strongly skewed toward higher values, cancer bucal etiologia annual median, rather than the mean, was used to calculate exposure for each year. Geometric means or averages of geometric means were used for the calculations.