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Evelyn O. Talbott,¹ Ada O. Youk,² Kathleen P. McHugh,¹ Jeffrey D. Shire,¹ Aimin Zhang,³ Brian P. Murphy,¹ and Richard A. Engberg¹

¹Department of Epidemiology, ²Department of Biostatistics, ³Department of Environmental and Occupation Health, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania, USA

Abstract

The largest U.S. population exposed to low-level radioactivity released by an accident at a nuclear power plant is composed of residents near the Three Mile Island (TMI) Plant on 28 March 1979. This paper (a collaboration of The University of Pittsburgh and the Pennsylvania Department of Health) reports on the mortality experience of the 32,135 members in this cohort for 1979-1992. We analyzed standardized mortality ratios (SMRs) using a local comparison population and performed relative risk regression modeling to assess overall mortality and specific cancer risks by confounding factors and radiation-related exposure variables. Total mortality was significantly elevated for both men and women (SMRs = 109 and 118, respectively) . All heart disease accounted for 43.3% of total deaths and demonstrated elevated SMRs for heart disease of 113 and 130 for men and women, respectively ; however, when controlling for confounders and natural background radiation, these elevations in heart disease were no longer evident. Overall cancer mortality was similar in this cohort as compared to the local population (male SMR = 100 ; female SMR = 101) . In the relative risk modeling, there was a significant effect for all lymphatic and hematopoietic tissue in males in relation to natural background exposure (p = 0.04) . However, no trend was noted. We found a significant linear trend for female breast cancer risk in relation to increasing levels of TMI-related likely -exposure (p = 0.02) . Although such a relationship has been noted in other investigations, emissions from the TMI incident were significantly lower than in other documented studies. Therefore, it is unlikely that this observed increase is related to radiation exposure on the day of the accident. The mortality surveillance of this cohort does not provide consistent evidence that radioactivity released during the TMI accident has a significant impact on the mortality experience of this cohort to date. However, continued follow-up of these individuals will provide a more comprehensive description of the morbidity and mortality experience of the cohort. Key words: dose-response relationship, epidemiology, ionizing radiation, mortality, neoplasms, nuclear reactors. Environ Health Perspect 108:545-552 (2000) . [Online 27 April 2000]

http://ehpnet1.niehs.nih.gov/docs/2000/108p545-552talbott/ abstract.html

Address correspondence to E.O. Talbott, Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, 507 Parran Hall, Pittsburgh, PA 15261 USA. Telephone: (412) 624-3074. Fax: (412) 624-7397. E-mail: eot1+@pop.pitt.edu

We thank N. Wald for guidance in the preparation of this manuscript. We also thank K. Ramaswamy and J. Bratz for their early contributions and continuing support of this project.

This research was supported by a grant from the Three Mile Island Public Health Fund.

Received 30 September 1999 ; accepted 28 December 1999.