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Steve Wing,¹ David Richardson,¹ Donna Armstrong,¹ and Douglas Crawford-Brown²

¹Department of Epidemiology; ²Department of Environmental Sciences and Engineering, School of Public Health, University of North Carolina, Chapel Hill, NC 27599-7400 USA

Abstract

Previous studies concluded that there was no evidence that the 1979 nuclear accident at Three Mile Island (TMI) affected cancer incidence in the surrounding area ; however, there were logical and methodological problems in earlier reports that led us to reconsider data previously collected. A 10-mile area around TMI was divided into 69 study tracts, which were assigned radiation dose estimates based on radiation readings and models of atmospheric dispersion. Incident cancers from 1975 to 1985 were ascertained from hospital records and assigned to study tracts. Associations between accident doses and incidence rates of leukemia, lung cancer, and all cancer were assessed using relative dose estimates calculated by the earlier investigators. Adjustments were made for age, sex, socioeconomic characteristics, and preaccident variation in incidence. Considering a 2-year latency, the estimated percent increase per dose unit +/- standard error was 0.020 +/- 0.012 for all cancer, 0.082 +/- 0.032 for lung cancer, and 0.116 +/- 0.067 for leukemia. Adjustment for socioeconomic variables increased the estimates to 0.034 +/- 0.013, 0.103 +/- 0.035, and 0.139 +/- 0.073 for all cancer, lung cancer, and leukemia, respectively. Associations were generally larger considering a 5-year latency, but were based on smaller numbers of cases. Results support the hypothesis that radiation doses are related to increased cancer incidence around TMI. The analysis avoids medical detection bias, but suffers from inaccurate dose classification ; therefore, results may underestimate the magnitude of the association between radiation and cancer incidence. These associations would not be expected, based on previous estimates of near-background levels of radiation exposure following the accident. Key words: dose-response relationships, ecologic studies, environmental epidemiology, ionizing radiation, methodology, neoplasms, nuclear power. Environ Health Perspect 105:52-57 (1997)

Address correspondence to S. Wing, 2101F McGavran-Greenberg Hall, Department of Epidemiology, School of Public Health, CB# 7400, University of North Carolina, Chapel Hill, NC 27599-7400 USA.

The current address for D. Armstrong is Department of Epidemiology, School of Public Health, One University Place, Rensselaer, NY 12144-3456 USA.

This work was supported by a grant from the Center for Environmental Health Studies, John Snow Institute. The authors thank Joy Wood and Rita Fellers for their assistance with data processing and Carl Shy and David Savitz for comments on an earlier draft.

Received 26 August 1996 ; accepted 15 October 1996.