Health Effects of Exposure to Radon BEIR VI (1999) / Chapter Skim
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Appendix D Miner Studies
Appendix D Miner Studies
Pages 254-290
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From page 254... ...
These studies consistently demonstrate excess lung-cancer mortality compared with expected numbers from the general population and increasing risk with increasing exposure to radon progeny. The recently published studies provide information on issues that could not be addressed adequately in the BEIR IV report.
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From page 255... ...
The risk model recommended in the current report is based on analyses of data from the 11 cohorts evaluated by NCI, although for some cohorts data have been updated or modified in other ways. Although the committee chose to conduct its own analyses of these data to develop its risk model, it drew heavily on the extensive results included in the NCI report and papers noted above, particularly for addressing the modifying effects of such variables as smoking, exposure rate, age at first exposure, and time since exposure.
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From page 256... ...
The statistics presented in Tables D-1 through Dell refer to the data used in analyses to develop the risk models for this report, which, for 7 of the cohorts, are very similar to data used in the NCI analyses, although in some cases changes in the approach used to allocate person-years resulted in minor changes from tables presented in the NCI report. For Czechoslovakia, exposures were re-evaluated and follow-up data were improved (Tomasek and Darby 1995)
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From page 257... ...
Significant decrease in ERR/exposure with increasing attained age, decreasing exposure duration, increasing average exposure rate, and increasing time since last exposure. Significant variation of ERR/exposure with categories of age at first exposure, but pattern was not consistent.
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From page 258... ...
also evaluated additional workers, including miners who started working in middle Bohemia in 1968-1975, iron miners, and burnt-clay miners; these additional workers had much lower cumulative exposures than the early uranium miners and were not included in the NCI analyses. Methods for follow-up and ascertainment of lung-cancer deaths: Both vital status and disease outcome were established from the population registry at the Ministry of Interior, examination of district death-registry records, oncologic notification records that were maintained by the Ministry of Health, and pathology records at district hospitals.
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From page 259... ...
Significant decrease in ERR/exposure with increasing attained age, decreasing exposure duration, increasing average exposure rate, decreasing age at first exposure, and increasing time since last exposure. Special studies: Sevc and others (1988)
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From page 260... ...
Significant decrease in ERR/exposure with increasing attained age, decreasing exposure duration, increasing average exposure rate, and increasing time since exposure. No evidence of modification by age at first exposure.
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From page 261... ...
Methods for follow-up and ascertainment of lung-cancer deaths: Vital status and cause of death were determined for 1955-1986 by searching the Mortality Database of Statistics, Canada. Number of exposed miners in cohort: 21,346 Number of exposed person-years: 300,608 Average cumulative exposure: 31.0 WLM Average duration of exposure: 3.0 years Average exposure rate: 0.9 WL Period of follow-up: 1955-1986
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From page 262... ...
This is an older cohort with the longest mean duration of exposure of the 11 cohorts. The average exposure rate is the lowest of the 11 cohorts, and this cohort makes a strong contribution to the estimation of effects at lower exposure rates.
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From page 263... ...
; estimated power of exposure was 1.32. Significant decrease in ERR/exposure with increasing attained age, decreasing exposure duration, increasing average exposure rate, and increasing time since exposure.
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From page 264... ...
Significant decrease in ERR/exposure with increasing attained age and increasing time since exposure. No evidence of significant modification by exposure duration, time since exposure, or age at first exposure.
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From page 265... ...
Significant decrease in ERR/exposure with attained age and decreasing exposure duration. No evidence of significant modification by exposure rate or time since exposure.
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From page 266... ...
Methods for follow-up and ascertainment of lung-cancer deaths: Vital status and cause of death were determined for 1950-1980 by searching the Mortality Database of Statistics, Canada. Number of exposed miners: 6,895 Number of exposed person-years: 67,080 Average cumulative exposure: 21.2 WLM Average duration of exposure: 1.7 years Average exposure rate: 1.3 WL Period of follow-up: 1950-1980 Average length of follow-up: 14.0 years Average year of first exposure: 1962.6 Average age at first exposure: 28.0 years Number of exposed lung-cancer deaths: Total: 56 Cumulative exposure < 100 WLM: 38 (68%)
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From page 267... ...
Significant decrease in ERR/exposure with increasing attained age, decreasing exposure duration, and time since last exposure. No evidence of significant modification by exposure rate or age at first exposure.
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From page 268... ...
Number of exposed miners: 1,457 Number of exposed person-years: 24,138 Average cumulative exposure: 7.6 WLM Average duration of exposure: 1.1 years Average exposure rate: 0.7 WL Period of follow-up: 1948-1987 Average length of follow-up: 21.9 years Average year of first exposure: 1956.0 Average age at first exposure: 29.2 years Number of exposed lung-cancer deaths: Total: 31 Cumulative exposure < 100 WLM: 30 (97%) Cumulative exposure < 50 WLM: 29 (94%)
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From page 269... ...
Cause of death was determined for 96% of workers who had been identified as deceased. Number of exposed miners: 1,769 Number of exposed person-years: 29,172 Average cumulative exposure: 59.4 WLM Average duration of exposure: 7.2 years Average exposure rate: 0.8 WL Period of follow-up: 1948-1986 Average length of follow-up: 24.7 years Average year of first exposure: 1956.8 Average age at first exposure: 29.5 years Number of exposed lung-cancer deaths: Total: 45 Cumulative exposure < 100 WLM: 33 (73%)
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From page 270... ...
In addition to providing quantitative information on the dependence of risks on exposure and exposure rate, the miner data are used to address the modifying effects of attained age, time since exposure, and age at first exposure. Table D-16 provides summary information on the 11 miner cohorts, and Table D-17 provides TABLE D-12 Number of exposed miners, person-years, lung cancer deaths, and mean WLM and WE Number Number Number Weighted of of person- of lung Mean Mean Mean mean Study workers years cancers WLMa duration WLa WLb China 13,649 134,842 936 286.0 12.9 1.7 2.3 Czechoslovakia 4,320 102,650 701 196.8 6.7 2.8 4.2 ColoradoC 3,347 79,556 334 578.6 3.9 11.7 17.0 Ontario 21,346 300,608 285 31.0 3.0 0.9 1.6 Newfoundland 1,751 33,795 112 388.4 4.8 4.9 12.2 Sweden 1,294 32,452 79 80.6 18.2 0.4 0.4 New Mexico 3,457 46,800 68 110.9 5.6 1.6 5.7 Beaverlodge 6,895 67,080 56 21.2 1.7 1.3 2.5 Port Radium 1,420 31,454 39 243.0 1.2 14.9 33.4 Radium Hill 1,457 24,138 31 7.6 1.1 0.7 1.0 France 1,769 39,172 45 59.4 7.2 0.8 2.6 Totald 60,606 888,906 2,674 164.4 5.7 2.9 10.8 aWeighted by person-years; includes 5-year lag interval.
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From page 271... ...
The highest average exposure rates (WL) are found in the Colorado, Newfoundland, and Port Radium cohorts, whereas the lowest average rates are found in Ontario, Sweden, Beaverlodge, Radium Hill, and France.
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From page 272... ...
. With the committee's categorical exposure-rate model, the quantitative risk estimates for exposure at residential levels are based on the portion of the miner data with exposure rates less than 0.5 WL, although estimates of parameters indicating the effects of attained age and time since exposure were based on all miner data.
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From page 273... ...
bWeighted by WLM received at each exposure rate. CThere were no lung cancers and very few person-years in the Czechoslovakia, Colorado, and Port Radium cohorts with average exposure rates < 0.5 WL, so means are not presented for these cohorts.
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From page 274... ...
This figure also illustrates the relatively short duration of employment for many of the workers in the Ontario and Beaverlodge cohorts. Data on Other Exposures Some cohorts of underground miners have been exposed to dust, arsenic, silica, and diesel exhaust in addition to radon progeny.
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From page 275... ...
Those analyses provide the most comprehensive summary of available data on lung-cancer risks in miners. Although, as noted above, the BEIR VI committee chose to base its risk model on analyses specifically conducted for this purpose, the committee relied on the NCI analyses for
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From page 276... ...
/o 4" 2~ 1" O 2~ o 2 1 1~ O_ C -.n WL-r Chat ...- Cam at_ .
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From page 277... ...
. PoM RadbJrn - - Radium ~11 Fret 010 20 30 40 50 (SO 70 80 90 Number of exposed miners ,; 0 10 20 30 40 50 60 70 80 00 Number of miners In follow~up r .
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From page 278... ...
278 rip C .° ~|I : ·4 o c 0 1 ~ jock 1" ~, I ~ , ~ I r' ~d)
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From page 279... ...
279 U~ _ , U~ ~n oo · E ~ o ~ I o ~ ~ ~, o ~ ~ _ ~ C ~ o ~ o _ ~ Z ° 1;: i i: o ~j; .
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From page 280... ...
That was followed by investigation of the modifying effects of attained age, age at first exposure, exposure rate, exposure duration, time since last exposure, and time since exposure. The effects of those variables were investigated both individually and after the inclusion of other variables.
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From page 281... ...
Even after adjustment for the modifying effects of time since exposure, attained age, and either exposure rate or exposure duration, evidence of heterogeneity remained. It was therefore necessary to include "between-cohort" variation in expressing the uncertainty in the risk estimates.
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From page 283... ...
Only for the Colorado cohort was there clear evidence of nonlinearity; for this reason, analyses of this cohort were restricted to cumulative exposures under 3,200 WLM; with this restriction, tests for nonlinearity were no longer statistically significant. For other cohorts, the only instance where a p value less than 0.05 was achieved was for the linear-exponential model in the Czechoslovakian cohort; in this case, the p value for a test of y= 0 was 0.03, whereas that for the nonlinear model was 0.07.
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From page 284... ...
Analyses Addressing the Modifying Effects of Attained Age, Age at Exposure, Time Since Exposure, Time Since Last Exposure, and Exposure Rate The BEIR IV committee found that relative risk depended on both attained age and time since exposure, and it included the modifying effects of these factors in its recommended risk model. Although the BEIR IV analyses indicated that exposure rate modified risk in the Colorado cohort, such evidence was not found in the other 3 cohorts, and the recommended model did not include modification by exposure rate.
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From page 285... ...
Analyses based on a simple linear model without consideration of modifying effects of other variables were repeated with adjustment for calendar year; the results changed little. Attained Age Like previous analyses by the BEIR IV committee, the NCI analyses indicated that ERR/exposure declined with attained age; that is, the increase with age in the excess lung-cancer risk attributable to radon was not as rapid as the background rate for the nonexposed.
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From page 286... ...
No clear trend was present with the categorical treatment applied to all 11 cohorts and ERR/exposure for those under age 20 was generally similar to ERR/exposure for those age 20 and older. The effects of age at first exposure were re-evaluated with inclusion of other variables (time since exposure, attained age, and exposure rate or duration)
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From page 287... ...
A particular concern is that earlier measurements, when exposure rates were largest, were generally subject to much greater errors than later measurements. Analyses treating both exposure duration and average exposure rate as categorical variables were conducted for each of the 11 cohorts.
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From page 288... ...
were compatible with no inverse exposure-rate effect. Most of the NCI analyses were based on either total duration of exposure or average exposure rate obtained as the total WLM divided by exposure duration.
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From page 289... ...
Overall Evaluation of Statistical Analyses Conducted Thus Far, with Emphasis on NCI Report Overall, the NCI analyses provide a comprehensive summary of nearly all the relevant data on underground miners exposed to radon and radon progeny. The application of the same methods to all cohorts (parallel analyses)
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From page 290... ...
Analyses based on age at exposure would be desirable especially if substantial numbers of workers with very early ages at start of exposure continued to be exposed for many years. The NCI analyses of exposure rate (or exposure duration)
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