A REEVALUATION OF CANCER INCIDENCE NEAR THE 3 MILE ISLAND NUCLEAR-PLANT - THE COLLISION OF EVIDENCE AND ASSUMPTIONS

Previous studies concluded chat there was no evidence that the 1979 nu clear 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 readi ngs and models of atmospheric dispersion. Incident cancers from 1975 t o 1985 were ascertained from hospital records and assigned to study tr acts. Associations between accident doses and incidence rates of leuke mia, lung cancer, and all cancer were assessed using relative dose est imates 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 inc rease per dose unit +/- standard error was 0.020 +/- 0.012 for all can cer, 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, lu ng cancer, and leukemia, respectively. Associations were generally lar ger considering a 5-year latency, but were based on smaller numbers of cases. Results support the hypothesis that radiation doses are relate d to increased cancer incidence around TMI. The analysis avoids medica l detection bias, but suffers from inaccurate dose classification; the refore results may underestimate the magnitude of the association betw een radiation and cancerincidence. These associations would not be exp ected, based on previous estimates of near background levels of radiat ion exposure following the accident.