Mortality among Radiation Workers at Rocketdyne (Atomics International), 1948–1999

A retrospective cohort mortality study was conducted of workers engaged in nuclear technology development and employed for at least 6 months at Rocketdyne (Atomics International) facilities in California, 1948-1999. Lifetime occupational doses were derived from company records and linkages with national dosimetry data sets. International Commission on Radiation Protection (ICRP) biokinetic models were used to estimate radiation doses to 16 organs or tissues after the intake of radionuclides. Standardized mortality ratios (SMRs) compared the observed numbers of deaths with those expected in the general population of California. Cox proportional hazards models were used to evaluate dose-response trends over categories of cumulative radiation dose, combining external and internal organ-specific doses. There were 5,801 radiation workers, including 2,232 monitored for radionuclide intakes. The mean dose from external radiation was 13.5 mSv (maximum 1 Sv); the mean lung dose from external and internal radiation combined was 19.0 mSv (maximum 3.6 Sv). Vital status was determined for 97.6% of the workers of whom 25.3% (n = 1,468) had died. The average period of observation was 27.9 years. All cancers taken together (SMR 0.93; 95% CI 0.84-1.02) and all leukemia excluding chronic lymphocytic leukemia (CLL) (SMR 1.21; 95% CI 0.69-1.97) were not significantly elevated. No SMR was significantly increased for any cancer or for any other cause of death. The Cox regression analyses revealed no significant dose-response trends for any cancer. For all cancers excluding leukemia, the RR at 100 mSv was estimated as 1.00 (95% CI 0.81-1.24), and for all leukemia excluding CLL it was 1.34 (95% CI 0.73-2.45). The nonsignificant increase in leukemia (excluding CLL) was in accord with expectation from other radiation studies, but a similar nonsignificant increase in CLL (a malignancy not found to be associated with radiation) tempers a causal interpretation. Radiation exposure has not caused a detectable increase in cancer deaths in this population, but results are limited by small numbers and relatively low career doses.

Cancer mortality among populations residing in counties near the Hanford site, 1950-2000

A descriptive epidemiologic study of cancer mortality among residents of counties near the Hanford nuclear facility site in Richland, Washington, was conducted. Between 1944 and 1957, radioactive 131I was released into the environment from the Hanford site. Cancer mortality from 1950 through 2000 was evaluated in four counties with the highest estimated exposure to 131I and compared with the cancer mortality experience in five demographically similar counties in Washington State with minimal 131I exposure. Overall, cancer rates in the study counties were slightly below those in the comparison counties [relative risk (RR) 0.95; 95% confidence interval (CI) 0.93-0.97], due mainly to a low risk for lung cancer (RR 0.89; 95% CI 0.85-0.93). Thyroid cancer (n=33; RR 0.84; 95% CI 0.56-1.26), female breast cancer (n=1,233; RR 0.99; 95% CI 0.92-1.06), leukemia other than chronic lymphocytic leukemia (n=492; RR 0.95; 95% CI 0.85-1.06), and childhood leukemia (n=71; RR=1.06; 95% CI 0.78-1.43) were not significantly increased in the exposed counties. Furthermore, there was no evidence that the cancer death rates over time differed between study and comparison counties. Patterns over time of thyroid cancer in particular were similar for exposure and comparison counties. Although based on a geographic correlation design, these data suggest that living near the Hanford site has not increased cancer rates.

Childhood cancer mortality in relation to the St Lucie nuclear power station

An unusual county-wide excess of childhood cancers of brain and other nervous tissue in the late 1990s in St Lucie County, Florida, prompted the Florida Department of Health to conduct a case-control study within the county assessing residential chemical exposures. No clear associations were found, but claims were then made that the release of radioactive substances such as strontium 90 from the St Lucie nuclear power station, which began operating in 1976, might have played a role. To test the plausibility of this hypothesis, we extended by 17 years a previous study of county mortality conducted by the National Cancer Institute. Rates of total cancer, leukaemia and cancer of brain and other nervous tissue in children and across all ages in St Lucie County were evaluated with respect to the years before and after the nuclear power station began operation and contrasted with rates in two similar counties in Florida (Polk and Volusia). Over the prolonged period 1950-2000, no unusual patterns of childhood cancer mortality were found for St Lucie County as a whole. In particular, no unusual patterns of childhood cancer mortality were seen in relation to the start-up of the St Lucie nuclear power station in 1976. Further, there were no significant differences in mortality between the study and comparison counties for any cancer in the time period after the power station was in operation. Relative rates for all childhood cancers and for childhood leukaemia were higher before the nuclear facility began operating than after, while rates of brain and other nervous tissue cancer were slightly lower in St Lucie County than in the two comparison counties for both time periods. Although definitive conclusions cannot be drawn from descriptive studies, these data provide no support for the hypothesis that the operation of the St Lucie nuclear power station has adversely affected the cancer mortality experience of county residents.

Cancer mortality in counties near two former nuclear materials processing facilities in Pennsylvania, 1950-1995

There has been concern that living near nuclear installations might increase the risk of cancer, including childhood leukemia, in surrounding communities. Such concern has been voiced by residents in Armstrong and Westmoreland Counties in Western Pennsylvania in conjunction with the operation of two former nuclear materials processing facilities located in the Apollo borough and the Parks township, just three miles apart. These facilities began operating in 1957 and 1960 and processed uranium and plutonium for commercial and naval applications. To evaluate the possibility of increased cancer rates in communities around the Apollo-Parks nuclear facilities, a cancer incidence and a cancer mortality survey were conducted. The county mortality findings are reported here. Nearly 40,000 cancer deaths occurred in the population residing in Armstrong and Westmoreland Counties from 1950 through 1995. Each of these two study counties was matched for comparison to three control counties in the same region on the basis of age, race, urbanization, and socioeconomic factors available from the 1990 U.S. Census. There were over 77,000 cancer deaths in the 6 control counties during the 45 y studied. Following similar methods used by the National Cancer Institute, Standardized Mortality Ratios (SMRs) were computed as the ratio of observed numbers of cancers in the study and control counties compared to the expected number derived from general population rates of the United States. Relative risks (RR) were computed as the ratios of the SMRs for the study and the control counties. There were no significant increases in the study counties for any cancer when comparisons were made with either the U.S. population or the control counties. In particular, deaths due to cancers of the lung, bone, liver, and kidney were not more frequent in the study counties than in the control counties. These are the cancers of a priori interest given that uranium and/or plutonium might be expected to concentrate in these tissues. Deaths from all cancers combined also were not increased in the study counties, and the RRs of cancer mortality before the facilities operated (1950-1964), during plant operations (1965-1980) and after plant closure (1980-1995) were similar: 0.96, 0.95 and 0.98, respectively. For childhood leukemia mortality, the relative risk comparing the study counties with their controls before plant start-up was 1.02, while during operations (RR 0.81) and after closure (RR 0.57) the relative risks were lower. The study is limited by the correlational approach and the relatively large size of the geographic areas of the counties studied.

Cancer incidence in municipalities near two former nuclear materials processing facilities in Pennsylvania

Because nuclear facilities can release radionuclides into the surrounding environment accidentally or during normal operations, there has been public concern over the possibility of adverse health effects. Two former nuclear materials processing facilities in Armstrong County Pennsylvania have been the focus of such public concern for over 20 y. The Apollo and Parks facilities processed uranium and plutonium fuels for use in nuclear applications. To evaluate the possibility of increased cancer rates in the communities near the Apollo-Parks nuclear processing materials plants, cancer incidence rates were assessed for the years 1993-1997, or nearly 40 y after the plants had begun operation in 1957 and 1960, respectively. The rates of cancer were evaluated among the approximately 17,000 persons living in 1 of 8 municipalities encompassing or near these nuclear sites. Numbers of cancers and mailing addresses (n = 935) were obtained from the Pennsylvania Department of Health. Because mailing addresses in small rural areas do not always reflect actual residences within a municipality, each of 935 addresses was validated (and corrections made when indicated) by contacting area postmasters and using Census Bureau geocoding information, street maps, and aerial photographs. Standardized Incidence Ratios (SIRs) were computed as the ratio of observed numbers of cancers in the study area compared to the expected number derived from general population rates of Pennsylvania. Forty percent of the mailing addresses were found not to be within the boundaries of the study municipalities. After excluding these persons who did not reside in one of the eight municipalities near the Apollo-Parks facilities, 581 cancers remained in contrast to 574.0 expected (SIR 1.01; 95% confidence interval 0.93-1.10). Based upon knowledge of the tissues where uranium or plutonium likely would be deposited after intake, cancers of the lung (SIR 0.88), kidney (SIR 1.05), non-Hodgkin's lymphoma (SIR 1.10), liver (SIR 0.61), and bone (2 observed vs. 1.19 expected) were carefully evaluated, but no significant excesses were noted at these sites. Cancers of the female breast and thyroid and leukemia also were not significantly increased, as expected since these tissues are not sites where uranium or plutonium would concentrate. Overall, no increase in cancer risk could be attributed to living near the two former nuclear materials processing facilities. However, misleading elevations in cancer risks would have been suggested if mailing addresses had not been corrected to exclude addresses that were not within the boundaries of the municipalities for which population data were available. The study had sufficient power to exclude increased cancer risks of 10% or greater.

Cancer mortality in relation to environmental chromium exposure

From the 1950s to the 1980s, hexavalent chromium compounds were used as additives at certain water-cooling towers at three southern California gas compressor facilities. Claims of potential residential chromium exposure prompted the examination of age-adjusted mortality rates during 1989 to 1998 for lung cancer, all cancer, and all deaths for neighborhoods near versus distant from the plants. Differences in the rates between areas tended to be small and not statistically significant. The only significant difference was a lower, rather than higher, rate of total cancer among women in the potentially exposed areas. Study limitations preclude a definitive assessment of risk, but similar to previous investigations of cancer in relation to environmental chromium exposure in other locations, this study found no evidence of a cancer hazard among residents living near these California gas compressor facilities.