NIOSH Occupational Energy Research Program

I. Oak Ridge Institute for Science and Education (ORISE)

The following studies were performed by investigators from the Center for Epidemiologic Research of ORISE, under the leadership of Donna Cragle, Ph.D. The analysis of the studies of two sites, X-10 and Y-12, were conducted by investigators from the University of North Carolina, as a subcontract to Oak Ridge Associated Universities.

1. Oak Ridge National Laboratory (X-10)
   
   

   Manuscript:
   Wing S, Shy CM, Wood JL, Wolf S, Cragle DL, Frome EL [1991]. Mortality among workers at Oak Ridge National Laboratory. JAMA 265(11): 1397-1402.
   
   

   Summary:
   

   White males hired at the Oak Ridge National Laboratory between 1943 and 1972 were followed up for vital status through 1984 (N=8,318). Relatively low mortality compared with that in U.S. white males was observed for most causes of death. However, leukemia mortality was elevated in the total cohort (63% higher, 28 deaths) and in workers who had at some time been monitored for internal radionuclide contamination (123% higher, 16 deaths). External radiation with a 20-year exposure lag was related to all causes of death (2.68%, increase per 10 mSv), primarily due to an association with cancer mortality (4.94%, increase per 10 mSv).
   
   Manuscript:
   Shy C, Wing S [1994]. A report on mortality among workers at Oak Ridge National Laboratory: followup through 1990. (PO 3C-70837, Final Report). Oak Ridge, TN: Oak Ridge Associated Universities, 21 pg.
   

   
   Summary:
   This study is a followup of the mortality experience of the cohort of white males employed at the Oak Ridge National Laboratory, originally described in 1991 (see preceding manuscript citation). An additional 586 deaths were identified (compared with 1,524 deaths in the original followup). The all-cause SMR, the all-cancer SMR, and lung cancer SMR were unchanged from the previous update; however, the leukemia SMR was 1.35, compared with 1.63. The SMR for leukemia declined to 0.71 for the recent followup years (1985-1990). This decline may reflect a leukemia-radiation association due to relatively high doses in the 1940s and 1950s.
   
   

2. Y-12 Plant, Oak Ridge

   
   Manuscript:
   Loomis D, Wolf S [1996]. Mortality of workers at a nuclear materials production plant in Oak Ridge, Tennessee, 1947-1990. Am J Ind Med, 29:131-141.
   
   Summary:The mortality experience of a cohort of 10,597 males and females who worked at Y-12 between 1947 and 1974 was somewhat lower than that of the United States population, and cancer mortality was equal to that of the general population. Deaths from lung cancer were significantly elevated (SMR=1.17, 95% CI=1.01, 1.34). Small excesses of brain and miscellaneous lymphatic cancers were also found (SMRs=1.13 and 1.32, respectively). A small increase in pancreatic cancer deaths was also noted (SMR=1.36).
   
   

3. Oak Ridge Gaseous Diffusion Plant (K-25)
   
   
   
   Oak Ridge K-25 Site. Oak Ridge, Tennessee. Date unknown. Photo courtesy of the U.S. Department of Energy.

   
   Manuscript:

   Dupree EA, Wells SM, Watkins JP, Wallace PW, Davis NC [1994]. Mortality among workers employed between 1945 and 1984 at a uranium gaseous diffusion facility. Oak Ridge, TN: Center for Epidemiologic Research Medical Sciences Division; Oak Ridge Institute for Science and Education; (DOE Contract DE-AC05-760R00033, Final report.) Available from the National Institute for Occupational Safety and Health/Health-Related Energy Research Branch, Cincinnati, OH, 24 pg.
   
   

   Summary:
   

   Mortality patterns among 35,712 workers ever employed for 30 days or more at K-25 between 1945 and 1984 were investigated. For white males, the SMR for all causes of death was significantly elevated (SMR=1.03, CI=1.01, 1.05). Other statistically significant increases among the white male population included cancers of the respiratory system including lung cancer, cancer of the bone, mental disorders, and respiratory diseases, and all injuries. Among nonwhite males, no cause of death showed a statistically significant increase.
   
   

4. Combined Oak Ridge Facilities (Tennessee Eastman Corporation [TEC], Y-12, X-10, K-25)
   
   

   Manuscript:
   

   Watkins JP, Cragle DL, Frome EL, Reagan JL, West CM, Crawford-Brown D, Tankersley WG [1997]. Collection, validation, and treatment of data for mortality study of nuclear industry workers. Appl Occup Environ Hyg 12(3):195-205.
   
   

   Summary:
   

   This paper describes methodologic issues related to combining facilities at Oak Ridge Operations in Tennessee. It includes evaluation of 118,588 workers employed at TEC, Y-12, K-25, or X-10. Validation and treatment of data for study members, and characteristics of their radiation exposure are discussed. Findings suggest under-ascertainment of external dose during the early years at two of the facilities.
   
   

   Manuscript:
   

   Frome EL, Cragle DL, Watkins JP, Wing S, Shy CM, Tankersley WG, West CM [1997]. A mortality study of employees of the nuclear industry in Oak Ridge, Tennessee. Radiation Res 148:64-80.

   
   Summary:
   

   An analysis was conducted of 27,982 deaths occurring among 106,020 persons employed for at least thirty days at four nuclear facilities in Oak Ridge, Tennessee [TEC, Y-12 (after 1947), X-10, and K-25] between 1943 and 1983. Overall mortality and overall cancer mortality estimates were in close agreement with national rates. The only notable excesses occurred for lung cancer (SMR=1.18) and nonmalignant respiratory disease (SMR=1.12) among white males. Analysis showed that workers employed at TEC, K-25, and multiple facilities had higher death rates than similar workers employed only at X-10 and Y-12. These elevations were due to differences among the facilities for lung cancer, leukemia, and other lymphatic cancers.
   
   

5. Welders at Oak Ridge Facilities
   
   

   Manuscript:
   

   Wells SM, Cragle DL, Tankersley WG [Undated]. An update of mortality among welders, including a group exposed to metal oxides. Oak Ridge, TN: Oak Ridge Associated Universities, Oak Ridge Institute for Science and Education, Center for Epidemiologic Research; (DOE Contract DE-AC05-76OR00033) Unpublished. 22 pg.
   
   

   Summary:
   

   Overall mortality and all causes of death were examined among 1,211 white male welders employed at three DOE facilities in Oak Ridge, from 1943 through 1989. A slight excess in emphysema deaths was noted in the overall cohort, and a slight excess of deaths from diseases of the respiratory system among workers exposed to nickel oxides. The SMR for lung cancer in the total cohort also reached statistical significance (SMR=1.38, CI=1.03-1.82). Elevations in deaths due to ulcers and prostate cancer were also noted among workers exposed to nickel oxides.
   
   

6. Lung Cancer Case-Control Study of Uranium Workers (TEC, Y-12, Fernald, Mallinckrodt)
   
   

   Manuscript:
   

   Dupree EA, Watkins JP, Ingle JN, Wallace PW, West CM, Tankersly WG [1995]. Uranium dust exposure and lung cancer risk in four uranium processing operations. Epidemiology 6(4): 370-375.
   
   

   Summary:
   

   This study sought to examine the relationship between uranium dust exposure and lung cancer mortality among workers employed in four uranium processing or fabrication operations located in Missouri, Ohio, and Tennessee. A total of 787 cases were identified. Odds ratios for lung cancer mortality for seven cumulative internal dose groups did not demonstrate increasing risk with increasing dose. However, an exposure effect was suggested for workers hired at age 45 years or older. Categorizing workers by facility, and further analyses for cumulative external dose and exposures to thorium, radium, and radon did not reveal any statistically significant association between exposure and increased risk.
   
   

7. Mallinckrodt Chemical Works
   
   

   Manuscript:
   

   Dupree-Ellis E, Watkins JP, Ingle JN, Phillips JA [2000]. External radiation exposure and mortality in a cohort of uranium processing workers. Am Epidemiol 152:91-95.
   
   

   Summary:
   

   This study investigated 2,514 white males employed in a uranium processing plant between 1942 and 1966. Through 1993, a total of 1,013 deaths were ascertained. The SMR for all causes was 0.90 (95% CI, 0.85-0.96) and 1.05 (95% CI, 0.9 - 1.17) for all cancers. Respiratory diseases, chronic nephritis, and lymphatic cancers were significantly elevated. Trend test revealed a statistically significant increase of kidney cancers with external radiation based on 10 cases with an excess relative risk of 10.5 per Sv of whole body exposure. The results must be considered provisional, since external radiation exposure may be a surrogate for internal radiation dose or chemical exposures that were not considered in this study.
   
   

8. 5 Rem Study (multiple facilities)
   
   

   Manuscript:
   

   Fry SA, Dupree EA, Sipe AH, Seiler DL, Wallace PW [1996]. A study of mortality and morbidity among persons occupationally exposed to >50mSv in a year: phase I, mortality through 1984. Appl Occup Environ Hyg 11(4):334-343.
   
   

   Summary:
   

   This study investigated the mortality experience of 3,145 individuals who reportedly received 50 mSv of penetrating ionizing radiation in any calendar year of employment (1943 through 1978) at all facilities operated for DOE. A total of 588 deaths (19%) occurred. The overall mortality experience of the total white male cohort was consistent with a healthy worker effect. SMRs for all causes of death, as well as diseases of the circulatory and digestive systems, were significantly decreased. SMRs were elevated for cancers of the esophagus and rectum, for lymphosarcoma, and for benign neoplasms. However, no statistically significant differences were found in mortality that were due to these causes or due to cancers of any of the major organ systems.
   
   

9. Cohort Mortality Study of Workers at Fernald Feed Materials Production Center
   
   
   Feed Materials Production Center (FMPC). Fernald, 20 miles outside Cincinnati, Ohio. January 1, 1987. Photo courtesy of the U.S. Department of Energy.
   
   Contractor: Oak Ridge Associated Universities (Donna Cragle, Ph.D.)
   
   Award Period: 1992-1997
   
   Summary:
   Mortality patterns were examined for 4,014 white males hired at the Fernald Feed Materials Production Center between 1951 and 1981. Vital status ascertainment through 1989 found 1,064 deaths among this population. Exposure estimates were developed for internal radiation, because of the potential for exposure to uranium dust and for external ionizing radiation. Although salaried workers showed a healthy worker effect, a significant increase for stomach cancer deaths was found in this subcohort. Hourly workers did not demonstrate a healthy worker effect and had excess mortality from all cancers, lung cancer, and motor vehicle injuries. For all workers, chronic non-malignant respiratory disease showed a positive dose-response relationship with internal exposure. These findings were produced without controlling for other lung carcinogens that were likely present in the work environment, such as radon and other chemicals.
   
   Manuscript:
   Cragle DL, Watkins JP, Ingle JN, Robertson-Demers K, Tankersley WG, West CM [1995]. Mortality among a cohort of white male workers at a uranium processing plant: Fernald feed materials production center, 1951-1989. Oak Ridge, TN: Center for Epidemiologic Research, Oak Ridge Institute for Science and Education. Unpublished. 29 pg.
   
   Significance:
   This assessment of a previously unstudied cohort complements Mallinckrodt studies and includes exposure assessment for both internal and external radiation.
   
   
10. Cohort Mortality Study of Workers at Savannah River Plant
    
    
    L-Reactor Facility. L Area, Savannah River Site, South Carolina. September 16, 1982. Photo courtesy of the U.S. Department of Energy.
    
    Contractor: Oak Ridge Associated Universities (Donna Cragle, Ph.D.)
    
    Award Period: 1992-1997
    
    Summary:
    A cohort mortality study of 9,757 white male workers at the Savannah River site employed between 1952 and 1974 reported 1,722 deaths, with followup complete through 1986. A strong healthy worker effect was noted in the SMR analysis, with no significant excesses noted. However, when trend tests were performed by external dose category, a significant positive dose-response relation was observed for external radiation and leukemia mortality when doses were lagged 2 years. The estimated for excess relative risk per Sievert for leukemia mortality was 13.61, which is consistent with the estimates derived for the Canadian (19.0 per Sievert) and Sellafield (13.92 per Sievert) populations. A draft final report was prepared for NIOSH in 1996.
    
    Manuscript:
    Cragle D [1998]. Mortality among workers at the Savannah River nuclear fuels production facility. In: ASA 1998 proceedings of the section on statistics in epidemiology. Alexandria, VA: American Statistical Association, pp. 83-87.
    
    Significance:
    This cohort, included in the leukemia case-control study, demonstrated a significant dose-response for leukemia. Both internal and external radiation exposures were evaluated.

II. Los Alamos National Laboratory

The "gadget" in the Trinity Test Site tower awaiting detonation. Built in 1945 at the Los Alamos National Laboratory. Los Alamos, New Mexico. July 1945. Photo courtesy of the U.S. Department of Energy.

The following five studies were performed by investigators at Los Alamos National Laboratory (principal epidemiologist: Laurie Wiggs, Ph.D.).

1. Mound Plant, Miamisburg, Ohio
   
   

   Manuscript:
   

   Reyes M, Wilkinson GS, Tietjen GL, Wiggs LD, Galke WA [1991]. Mortality among workers at the Mound facility: a preliminary report. (DOE Contract DE91 010482) Los Alamos National Laboratory, Los Alamos, NM, 20 pg.

   
   Summary:
   

   This technical report details an investigation of 4,697 white males employed at least 30 days between 1943 and 1979. No statistically significant elevations were found for the overall cohort. However, SMRs for thyroid, pharyngeal, lung, and prostate cancers were greater than 1.0. Significant elevations in lung cancer deaths were found among polonium workers employed between 1943 and 1959. Among workers employed for less than two years between 1943 and 1959, significant elevations were found for all causes, lung cancer, and for all injuries.
   
   

   Manuscript:
   

   Wiggs LD, Cox-DeVore CA, Wilkinson GS, Reyes M [1991]. Mortality among workers exposed to external ionizing radiation at a nuclear facility in Ohio. J Occup Med 33(5): 632-637.
   
   

   Summary:
   

   This study investigated 4,182 white males employed at the Mound facility between 1947 and 1979. No statistically significant elevations for overall mortality or site-specific cancers were noted. A subcohort of 3,229 workers were monitored for external radiation. This subcohort was assessed for possible dose-response relationships between mortality from various causes and external exposure to ionizing radiation. No statistical differences in mortality were observed between workers exposed to ionizing radiation and unexposed workers. However, among workers exposed to external radiation, a statistically significant dose-response relationship was seen for lymphopoietic/hemotopoietic cancers and for all leukemias.
   
   

   Manuscript:
   

   Wiggs LD, Cox-DeVore CA, Voelz GL [1991]. Mortality among a cohort of workers monitored for 210Po Exposure: 1944-1972. Health Phy 61(1):71-76.
   
   

   Summary:
   

   his study investigated mortality patterns among 2,181 white males employed at the Mound facility between 1944 and 1972, years in which polonium-210 was processed and urine monitoring was in place. The SMR for all causes was less than 1.0. SMRs for cancers of the thyroid, rectum, esophagus, lymphatic system, oral cavity, and lung were elevated, though not significantly. Elevated SMRs were seen for lung cancer among workers employed during WWII, but not for the post-WWII group. No dose-response relationship was noted between mortality and exposure to internal radiation.
   
   

2. Los Alamos National Laboratory (LANL)
   
   

   Manuscript:
   

   Wiggs LD, Johnson ER, Cox-DeVore CA, Voelz GL [1991]. Mortality through 1990 among white male workers at Los Alamos National Laboratory: Considering exposures to plutonium and external ionizing radiation. Health Phy 67(6): 577-588.

   
   Summary:
   

   A cohort mortality study was conducted of 15,727 white males employed at LANL from 1943 to 1977. No cause of death was elevated among this cohort. Mortality from all causes of death and all cancers was significantly low, as was mortality from many other cause-specific categories. SMR analyses were also conducted for a subcohort of workers first employed during WWII. The SMRs for the WWII subcohort indicated that mortality in this subcohort was also low compared with the general population. No cause of death was significantly elevated. Analyses of mortality comparing plutonium-exposed with unexposed workers considering a 10-year induction period also showed that no cause of death was significantly elevated. However, dose-response relationships were observed for cumulative dose of external ionizing radiation and cancers of the brain/central nervous system, esophagus, and Hodgkin's disease.
   
   

3. Rocky Flats Nuclear Weapons Plant, Golden, Colorado

   
   Manuscript:
   

   Wilkinson GS, Tietjen GL, Wiggs LD, Galke WA, Acquavella JF, Reyes M, Voelz GL, Maxweiler RJ [1987]. Mortality among plutonium and other radiation workers at a plutonium weapons facility. Am J Epidemiol 125(2): 231-250.

   
   Summary:
   

   Mortality patterns were examined for 5,413 white males employed for at least two years at the Rocky Flats Plant from 1952 through 1979. Fewer than expected deaths were observed for all causes, all cancers, and lung cancer. An excess of brain cancer was found for the overall cohort. Elevated rate ratios (RRs) for all causes of death and all lymphopoietic cancers were found, when comparing workers with plutonium burdens of 2 nCi with those with body burdens < 2 nCi. Increased RRs were also observed for esophageal, stomach, colon, and prostate cancers, as well as lymphosarcomas and reticulum cell sarcomas. When workers with 1 rem were compared with those with < 1 rem cumulative exposure, several elevated RRs were observed (myeloid leukemia, lymphosarcomas and reticulum cell sarcomas, liver neoplasm, and unspecified brain tumors). No overall dose-response relationships were found for either plutonium or external radiation exposure.
   
   

4. Zia Company, Los Alamos, New Mexico
   
   

   Manuscript:
   

   Galke GA, Johnson ER, Tietjen GL [1992]. Mortality in an ethnically diverse radiation exposed occupational cohort. Los Alamos, NM: Los Alamos National Laboratory; Unpublished. 70 pg.

   
   Summary:
   

   A total of 5,424 workers employed at Zia between 1946 and 1978 who were monitored for exposure to either plutonium or external ionizing radiation were included in this retrospective cohort mortality study. Among male workers, significantly elevated SMRs were seen for stomach cancer, senility and ill-defined conditions, all injuries, all incidents, and motor vehicle incidents. SMRs for female workers were consistent with mortality rates in the general population. Hispanic male workers, however, had significantly higher mortality from stomach cancer, all injuries, all incidents, and motor vehicle incidents. Non-Hispanic males had significantly higher mortality from all causes, all cancers, lung cancer, all circulatory diseases, and all respiratory diseases. Stratified rate ratio (RR) analyses were conducted to test the association between radiation exposure and mortality. No significantly high RRs were seen in either Hispanic or non-Hispanic males in the plutonium or external ionizing radiation analyses.
   
   

5. Plutonium Workers (Los Alamos National Laboratory, Zia)

   
   Manuscript:
   

   Voelz GL, Johnson ER, Lawrence JNP [1993]. Mortality of 244 male workers exposed to plutonium. Los Alamos, NM: Los Alamos National Laboratory; Unpublished. 16 pg.

   
   Summary:
   

   This paper describes an updated mortality study of 224 male workers exposed to plutonium at the Los Alamos National Laboratory and Zia. Study subjects were selected by searching the Los Alamos plutonium dosimetry records for all workers who were estimated to have plutonium depositions over 370 Bq. Two types of mortality analyses were performed: (1) SMRs (calculated as of 1990) based on mortality rates of white males in the U.S. general population, and (2) mortality RRs to compare deaths occurring in the exposed group with those in an unexposed comparison group. The SMRs for all malignant neoplasms were below 1.0. Only the SMR for bone cancer was elevated (SMR=10.6, CI=0.15, 59), though this is based on only one case. All mortality rate ratios (RRs) were calculated with a 10-year cancer induction time. The ratios for all causes of death and all malignant neoplasms were not significantly elevated. Only the standardized rate ratio (SRR) for digestive system cancer was above 1.0 (SRR=1.13, CI=0.42, 3.08).

III. Hanford Environmental Health Foundation
Battelle Pacific Northwest Laboratories

Several research projects were performed jointly by investigators at the Hanford Environmental Health Foundation(principal epidemiologist: Ellen Omohundro, Ph.D.) and Pacific Northwest Laboratory (principal investigator: Ethel Gilbert, Ph.D.). Hanford Environmental Health Foundation was responsible for the collection and verification of mortality, occupational history, and medical and personal health history data. Pacific Northwest Laboratory gathered radiation dosimetry data and was responsible for data integration and analysis. With the exception of the combined studies, all the research efforts by these contractors pertained to the Hanford Site.

1. 1-3. Mortality of workers at the Hanford Site
   
   

   Manuscript:

   Gilbert ES, Omohundro E, Buchanan JA, Holter NA [1993]. Mortality of workers at the Hanford Site: 1945-1986. Health Phy 64(6):577-590.
   
   

   Summary:
   

   This study investigated mortality among contractor employees initially employed at the Hanford site from 1944-1978. Both the SMR for overall mortality and mortality from malignant neoplasms for all workers were below 1.0. SMRs for diseases of the musculoskeletal system among all workers, for cancer of the pancreas in males not monitored for external radiation, and for all other solid tumors in males not monitored for external radiation were elevated, but not significantly. Comparisons of death rates by radiation dose within the cohort showed no evidence of a correlation for all causes of death, all cancers, or leukemia with radiation dose. Cancer of the pancreas (p=0.07) and Hodgkin's disease (p=0.04) showed positive correlations with radiation dose. Rates for multiple myeloma death in this cohort continue to be elevated, consistent with a previous report.

   
   Manuscript:
   

   Omohundro E, Gilbert E [1993]. An evaluation of the adequacy of vital status follow-up in the Hanford Worker Mortality Study. Richland, WA: Hanford Environmental Health Foundation; (DOE Contract DE-AC06-76RLO 1830, report prepared for the National Institute for Occupational Safety and Health/Health-Related Energy Research Branch, Cincinnati, OH). Available from NTIS, Springfield, VA; DE94005179, 40 pg.

   
   Summary:

   
   This report was designed to evaluate the completeness of vital status ascertainment in the Hanford worker cohort. Identifying information about 17,708 Hanford workers was submitted to Equifax Government and Special Systems. For the period 1945-86, Equifax ascertained only 12 new deaths. To evaluate the adequacy of the methods used by Equifax, information about 2,254 Hanford workers who had been previously identified as dead were also submitted. Equifax missed less than 2% of known Hanford deaths during 1965-86, but missed about 18% of deaths occurring before 1965. For the period 1987-89, Equifax identified 49 new deaths. A stratified random sample of 1,600 of the 17,708 workers with unknown vital status was submitted to Equifax for a more extensive investigation of followup status. Information about these workers was compared with consumer credit databases to determine the last date these workers were known to be alive. The results of this part of the study indicate that if these procedures had been applied to all workers with unknown vital status, about 90% of these workers would have been confirmed to be alive. About 5% of the total study population would have remained lost to followup.
   
   

2. Combined U.S. Cohorts (Hanford, Oak Ridge National Laboratory, Rocky Flats)
   
   
   
   Oak Ridge Graphite Reactor, code-named "X-10," produced the world's first quantities of plutonium. Oak Ridge Graphite Reactor Landmark, Oak Ridge National Laboratory, Tennessee. Date not provided. Photo courtesy of the U.S. Department of Energy.

   
   Manuscript:
   

   Gilbert ES, Cragle DL, Wiggs LD [1993]. Update analyses of combined mortality data on workers at the Hanford Site, Oak Ridge National Laboratory, and Rocky Flats Nuclear Weapons Plant. Radiation Res 136:408-421.
   
   

   Summary:
   

   Combined analyses of mortality data for 44,943 workers from Hanford, Oak Ridge National Laboratory, (X-10), and Rocky Flats were undertaken to assess cancer risks associated with protracted low-dose exposure to ionizing radiation. Of 24 cancer sites evaluated, 12 showed positive correlations with radiation dose, and 12 showed negative correlations. Cancer of the esophagus, cancer of the larynx, and Hodgkin's disease showed statistically significant correlations with radiation dose, but these correlations were likely to have resulted from bias or chance fluctuations. Evidence of an increase in the excess relative risk with increasing age at risk was found for all cancer in both Hanford and Oak Ridge National Laboratory. Both populations showed significant correlations of all cancer with radiation dose among those 75 years and older. Although this age effect may have resulted from bias in the data, its presence suggests that summary risk estimates for nuclear workers be interpreted cautiously.
   
   

3. Combined International Studies (U.S., Canada, U.K.)

   
   Manuscript:
   

   Cardis E, Gilbert E, Carpenter L, Howe G, Kato I, Armstrong BK, Beral V, Cowper G, Douglas A, Fix J, Fry SA, Kaldor J, Lave C, Salmon L, Smith PG, Voelz GL, Wiggs LD [1995]. Effects of a low dose and low rates of external ionizing radiation: Cancer mortality among nuclear industry workers in three countries. Radiation Res 142:117-132.
   
   

   Summary:
   

   This paper presents the results of combined analyses of mortality data for 95,673 workers monitored for external exposure to ionizing radiation and employed for 6 months or longer in the nuclear industry in the United States, the United Kingdom, and Canada. No evidence was found of an association between radiation dose and mortality from all causes or from all cancers. Mortality from leukemia, excluding chronic lymphocytic leukemia, showed a statistically significant association with cumulative external radiation dose. Among 31 other cancer sites evaluated, a statistically significant association with external dose was observed only for multiple myeloma. This was attributable primarily to the associations reported previously in the Hanford and Sellafield cohorts. The relative risk of all cancers excluding leukemia was 0.99, and 1.22 for leukemia excluding chronic lymphopoietic leukemia for a cumulative protracted dose of 100 mSv compared to 0 mSv.
   

4. Combined U.S. Cohorts (Hanford, Oak Ridge National Laboratory, Rocky Flats
   
   Manuscript:
   
   Gilbert ES, Cragle DL, Wiggs LD [1993]. Update analyses of combined mortality data on workers at the Hanford Site, Oak Ridge National Laboratory, and Rocky Flats Nuclear Weapons Plant. Radiation Res 136:408-421.
   
   Summary:
   
   Combined analyses of mortality data for 44,943 workers from Hanford, Oak Ridge National Laboratory, (X-10), and Rocky Flats were undertaken to assess cancer risks associated with protracted low-dose exposure to ionizing radiation. Of 24 cancer sites evaluated, 12 showed positive correlations with radiation dose, and 12 showed negative correlations. Cancer of the esophagus, cancer of the larynx, and Hodgkin's disease showed statistically significant correlations with radiation dose, but these correlations were likely to have resulted from bias or chance fluctuations. Evidence of an increase in the excess relative risk with increasing age at risk was found for all cancer in both Hanford and Oak Ridge National Laboratory. Both populations showed significant correlations of all cancer with radiation dose among those 75 years and older. Although this age effect may have resulted from bias in the data, its presence suggests that summary risk estimates for nuclear workers be interpreted cautiously.
   
5. Combined International Studies (U.S., Canada, U.K.)
   
   Manuscript:
   
   Cardis E, Gilbert E, Carpenter L, Howe G, Kato I, Armstrong BK, Beral V, Cowper G, Douglas A, Fix J, Fry SA, Kaldor J, Lave C, Salmon L, Smith PG, Voelz GL, Wiggs LD [1995]. Effects of a low dose and low rates of external ionizing radiation: Cancer mortality among nuclear industry workers in three countries. Radiation Res 142:117-132.
   
   Summary:
   
   This paper presents the results of combined analyses of mortality data for 95,673 workers monitored for external exposure to ionizing radiation and employed for 6 months or longer in the nuclear industry in the United States, the United Kingdom, and Canada. No evidence was found of an association between radiation dose and mortality from all causes or from all cancers. Mortality from leukemia, excluding chronic lymphocytic leukemia, showed a statistically significant association with cumulative external radiation dose. Among 31 other cancer sites evaluated, a statistically significant association with external dose was observed only for multiple myeloma. This was attributable primarily to the associations reported previously in the Hanford and Sellafield cohorts. The relative risk of all cancers excluding leukemia was 0.99, and 1.22 for leukemia excluding chronic lymphopoietic leukemia for a cumulative protracted dose of 100 mSv compared to 0 mSv.