More than a dozen major, independent studies have assessed the radiation releases and possible effects on the people and the environment near TMI since the 1979 accident at TMI-2.
The findings of the most recent studies:
Largely in response to citizens' concerns, the Three Mile Island Public Health Fund asked Maureen C. Hatch of the Division of Epidemiology, Columbia University School of Public Health, New York City, and three associates - Jan Beyea, Jeri Nieves and Mervyn Susser - to study the pattern of accident releases to determine if they had any correlation with cancer incidence around TMI.
The Hatch-Susser team designed and carried out an elaborate study that was based on mathematical modeling of where the TMI-2 releases traveled and thousands of records of patients from 19 hospitals in the TMI area.
First, they had to consider whether the releases were accurately known. Despite variations in the estimate of what was released, Hatch-Susser found that "in every instance, the level of exposure was deemed to be very low" - an average of approximately 10 millirems and a projected maximum dose of 100 millirems.
In the September 1990 issue of the American Journal of Public Health, the Hatch-Susser team reported that "the prior expectation based on estimated releases and conventional radiobiology - that no excess cancer would be found - was confirmed in most if not all respects."
At the request of U.S. Sen. Edward M. Kennedy, chair of the Senate Committee on Labor and Human Resources, the National Cancer Institute conducted a study of cancer mortality rates around 52 nuclear power plants, including TMI, and nine U.S. Department of Energy facilities. The NCI study compared the counties containing nuclear facilities with control counties in the same region.
Released in September 1990, the NCI study "concludes that the survey has produced no evidence that an excess occurrence of cancer has resulted from living near nuclear facilities." At Senator Kennedy's request, the study looked closely at TMI and the Pilgrim Nuclear Power Station, Plymouth, Mass.
The Pennsylvania Department of Health maintained a registry of close to 35,000 persons who lived within five miles of TMI during the TMI-2 accident. This "close-in" data base was augmented by other statistical records available to the department.
The Department of Health found:
The following is a brief listing of other independent studies, most conducted by state and federal agencies, following the TMI-2 accident.
Population Exposure and Health Impact of the Accident at the Three Mile Island Nuclear Station, 1973 - The study was conducted by experts known as the Ad Hoc Population Dose Assessment Group from the U.S. Nuclear Regulatory Commission (NRC), the U.S. Department of Health and Human Services and U.S. Environmental Protection Agency. Its conclusion was that there were no immediate health effects, and that latent or long-term effects, if any, would be minimal.
Report of the President's Commission on the Accident at Three Mile Island, 1979 - The study was done by a commission appointed by President Jimmy Carter and chaired by John G. Kemeny, then President of Dartmouth College. Its conclusion on health effects was that there would be no detectable cancers or genetically related instances of ill-health from the accident. The report said the most important health effect of the accident was mental stress experienced by the general population and the workers.
Three Mile Island: A Report to the Commissioners and to the Public, 1980 - The report, commissioned by the NRC, was done by a Washington, D.C., law firm, Rogovin, Stern & Huge. It concluded that health effects on the population as a whole, if they existed at all, would be nonmeasurable and nondetectable.
Report to the Nuclear Regulatory Commission from the Staff Panel on the Commission's Determination of an Extraordinary Nuclear Occurrence, 1980 - The report was published by the NRC and based on work by representatives of the NRC, Environmental Protection Agency, U.S. Department of Health and Human Services, the former Pennsylvania Department of Environmental Resources and U.S. Department of Energy. It confirmed the population dose estimates of the Ad Hoc Population Dose Assessment Group, the report of the President's Commission and the report commissioned by Metropolitan Edison.
Investigations of Reported Plant and Animal Health Effects in the Three Mile Island Area, 1980 - The report was published by the NRC and based on the findings of investigators of the NRC, Pennsylvania Department of Agriculture, U.S. Environmental Protection Agency and Argonne National Laboratory. It concluded that "it appears that none of the reported plant and animal health effects (reviewed in the report) can be directly attributed to the operation of or the accident" at TMI.
Follow-up Studies on Biological and Health Effects Resulting from the Three Mile Island Nuclear Power Plant Accident of March 28, 1979 - This study was done by the Committee on Federal Research into the Biological Effects of Ionizing Radiation and published by the National Institute of Health. The committee's TMI Follow-up Research Subcommittee was made up of representatives from the National Institutes of Health; Food and Drug Administration; Alcohol, Drug Abuse and Mental Health Administration; Communicable Disease Center; Environmental Protection Agency; Nuclear Regulatory Commission; Department of Energy, and Department of Defense. The study concluded that the accident would produce no detectable health effects.
Report of the Governor's Commission on Three Mile Island, 1980 - The report was done by a commission established by Gov. Richard Thornburgh. It agreed with the findings of the President's Commission that accident health effects would be negligible and found that the mental stress from the accident would be transient for the general population.
Impact of TMI Nuclear Accident Upon Pregnancy Outcome, Congenital Hypothyroidism and Mortality, 1981 - The study was done by the Pennsylvania Department of Health. It concluded that pregnant women exposed to accident releases showed no measurable differences for prematurity, congenital abnormalities, neonatal deaths or any other factors examined. The "TMI Mother-Child Registry" established for the study continues to be monitored by the PA Health Department. Reports are issued at five-year intervals. The Health Department also found no increase in infant hypothyroidism as a result of exposure from radioactive iodine. Seven cases of congenital hypothyroidism in Lancaster County outside the 10 mile radius of the investigation also were found to be unrelated to the accident. The finding was supported by an independent Hypothyroidism Investigation Committee organized by the Health Department.
Cancer Mortality and Morbidity around TMI, 1985 - The study was done by the Pennsylvania Department of Health and is being followed up by the Department. It found no increased cancer risks to residences near TMI.
Assessment of Off-Site Radiation Doses from the Three Mile Island Unit 2 Accident, 1979 - The report, commissioned by Metropolitan Edison, was done by Pickard, Lowe and Garrick, Inc., a Washington, D.C. consulting firm. Its findings on doses from the accident were generally consistent with those studies that concluded that radiation releases from the accident were too small to cause detectable health effects
Last updated July 11, 2012, 11:14am CDT.