The partial meltdown at Three Mile Island, March 28, 1979, involved the loss-of-coolant, the melting of half its fuel, a hydrogen explosion in the “containment” building,  the uncontrolled, frightening buildup of explosive hydrogen in the reactor vessel, the venting of radioactive gases, and the dumping of contaminated water into a major source public drinking water. The accident caused such a scare that it ended the expansion of nuclear power in the US. Today, reactor builds can’t keep up with closures.
Yet the human health consequences of TMI aren’t well known, and official cover-ups, propaganda and ignorance of radiation-induced illnesses have led to trivialization of the disaster. As Gar Smith notes in his 2012 book Nuclear Roulette, public officials issued one false statement after another for days, like: there were no radiation releases; radiation releases were “controlled”; radiation releases were “insignificant”; there was no melting of the reactor fuel; there was never any danger of an explosion; there was no need to evacuate close communities. In fact, TMI’s failed containment released a plume of radiation “about 100 times more significant than the initial estimates offered” by the industry and the Nuclear Regulatory Commission — which still doesn’t know how much radiation was released or where it went.
David Lochbaum of the Union of Concern Scientists estimates between 40 million curies and 100 million curies escaped during the accident. President Carter’s Kemeny Commission estimated about 15 million curies of radioactive gas was vented from the containment building, including 43,000 curies of krypton-85  — which stays in the environment for 100 years — and 15-to-24 curies of radioactive iodine-131.  (A curie is a huge amount of radiation — 37 billion disintegrations per second.) The NRC later admitted to several “deliberate but uncontrolled releases” of the cancer-causing gases. Estimates of these airborne releases are mere guesses, because half of the outside radiation monitors were not working, and of those that worked, a large number of them went off-scale. 
Approximately 400,000 gallons of highly radioactive cooling water leaked from the reactor into “containment” areas. This water was secretly dumped into the Susquehanna River, a source of drinking water for nearby communities.  Later, about 2.3 million gallons of radioactively contaminated cooling water were allowed to be “evaporated” into the atmosphere.
On the third day of the venting and dumping, half the population within 15 miles — 144,000 people — fled the area. By this time the bulk of the airborne radiation gusher had already been spewed and was drifting on the wind. Yet the Kemeny Commission ignored all data on the effects of wind-borne radiation, even though the wind blew 6-to-9 mph toward upstate New York and western Pennsylvania. 
“Nobody died at Three Mile Island” — unless you count babies
In 1980, Pennsylvania State Health Department authorities reported a sharp rise in hypothyroidism in newborn infants in the three counties downwind from the reactor. Late in 1979, four times as many infants as normal were born with the disease. The NRC said the increase was unrelated to radiation released by TMI.  Upwind incidence of the disease had dropped to below the national average.
Eric Epstein, Chair of Three Mile Island Alert had noted that in March 1982, the American Journal of Public Health reported, “During the first two quarters of 1978, the [newborn] mortality rate within a 10 mile radius of Three Mile Island was 8.6 and 7.6 per 1,000 live births, respectively. During the first quarter of 1979, following the startup of accident-prone Unit 2, the rate jumped to 17.2; it increased to 19.3 in the quarter following the accident at TMI, and returned to 7.8 and 9.3, respectively, in the last two quarters of 1979.” (Dr. Gordon MacLeod, Secretary, Pennsylvania Department of Health.)
A June 1991, Columbia University Health Study’s findings (Susser-Hatch) were published in the American Journal of Public Health. The data actually shows more than a doubling of observed cancers in areas near the partial meltdown, including lymphoma, leukemia, colon and the hormonal category of breast, endometrium, ovary, prostate, and testis. For leukemia and lung cancers in the six-to-12 kilometer distance from TMI, the number observed cases was almost four times greater. In the zero-to-six kilometer range, colon cancer was 4 times greater. The study found “a statistically significant relationship between incidence rates after the accident and residential proximity to the plant.”
In the county where TMI is located, infant mortality (deaths of kids under one) soared 53.7% in the first month after the accident; the rate rose 27% in the first year after the accident. As originally published, the federal government’s own Monthly Vital Statistics Report shows a statistically significant rise in infant and over-all mortality rates shortly after the accident.
Studying 10 counties closest to TMI, Jay Gould and Benjamin Goldman, in their 1990 book Deadly Deceit, found that childhood cancers, other infant diseases, and deaths from birth defects were 15% to 35% higher than before the accident, and those from breast cancer 7% higher. These increases far exceeded those elsewhere in Pennsylvania.  Gould suggests that between 50,000 and 100,000 excess deaths occurred after the TMI accident.
Joseph Mangano studied the three counties closest to TMI — Daupin, Lancaster, and York. He found that between 1980 and 1984, “death rates in these three counties were considerably higher than 1970-74 (before the reactor opened) for leukemia, female breast cancer, thyroid and bone and joint cancers.” Cancer deaths among kids fewer than 10 years of age (between 1980 and 1984) nearly doubled compared to the national rate.
The death and disease associated with TMI’s radiation releases were foretold by Roger Mattson, a Director of the Systems Safety Division at the NRC at the time. Mattson told the NRC’s members during the accident: “I’m not sure why you are not moving people. I don’t know what we are protecting at this point.”
John LaForge is a co-director of Nukewatch, a nuclear watchdog group in Wisconsin, and edits its Quarterly.
 Daniel Ford, Three Mile Island, Viking Press, 1982, p. 237-238
 Nuclear Regulatory Commission: <http://www.nrc.gov/POA/gmo/tip/tip10.htm>
 John May, The Greenpeace Book of the Nuclear Age, Pantheon, 1989, p. 82
 Dr. John Beyea, study for the National Audubon Society, 1984, in John May, above, pp. 220-221
 Allen Hedge, Cornell University, “Systems Thinking,” August 2007, <ergo.human.cornell.edu/studentdownloads/DEA325/pdfs/systems.pdf> Stephen Pople, Oxford, Explaining Physics, GCSE Edition, Sec. 8, Electrons and Atoms, 1990, p. 323; and Report of the President’s Commission on the Accident at TMI, October 30, 1979
 The Washington Post, March 28, 1989
 Jay Gould and Benjamin Goldman, Deadly Deceit: Low Level Radiation, High Level Cover-Up, New York, Four Walls Eight Windows, 1990, p. 59
 Boston Globe, February 23, 1980
 Joseph Mangano, Low-Level Radiation and Immune System Damage: An Atomic Era Legacy, Lewis Publishers, New York, 1999, p. 65
 Ford, Three Mile Island, p. 234