The Fallout over Fallout

D. Muska

In the 1950s, almost 100 nuclear bombs were set off in Southern Nevada. It is now known that residents, livestock and military personnel in the immediate vicinity of the blasts suffered adverse health effects. But for many years, activists have claimed that nuclear fallout from atomic testing made thousands of additional Americans sick—people who did not live or work close to the Nevada Test Site (NTS). This claim received a bit more credibility last year, when a federal health institute concluded that as many as 75,000 children developed thyroid cancer due to nuclear fallout. While there is no doubt that Americans were exposed to radioactive material from explosions at the NTS, the public health consequences of the blasts remain murky. Earlier this month, two federal science panels concluded that there is little evidence to indicate widespread thyroid cancers from nuclear testing, and thus a national screening program for the disease is not needed.

Mushroom Cloudy

Between January 1951 and October 1958, the United States conducted 97 atmospheric tests of nuclear weapons at the Nevada Test Site. (A few additional tests were performed in the 1960s.) Some bombs were positioned through airdrops and metal towers. Others were launched by rockets, fired from cannons and suspended by helium balloons at altitudes between 340 and 1,500 feet. In the early 1960s—as a result of the Limited Test Ban Treaty signed by the United States and the Soviet Union—nuclear testing moved underground. Over 800 tests have been performed at the NTS since then, including two experiments in 1997.

The mushroom cloud which results from an atomic blast produces several types of fallout. Large particles fall back to the ground within a few hours, while small particles return to earth over the course of days and weeks. Minute particles can be carried to high altitudes and be dispersed over months and even years. The dispersal pattern for each blast varies, depending on the size of the weapon and wind speed and direction.

Got Thyroid Cancer?

Iodine 131 is a radioactive byproduct of atomic blasts. When it is absorbed by vegetation which is consumed by cows, contaminated milk can result. Humans who ingest contaminated milk, many say, are at greater risk for thyroid cancer. While no smoking gun exists to prove this theory, a number of studies have suggested that such a link exists. In 1995, one report found a connection between fallout and the thyroid tumors of Nevada children who lived downwind from the NTS. More recently, Italian researchers discovered that children downwind from the Chernobyl nuclear disaster are more susceptible to thyroid diseases.

In 1983, Congress ordered the secretary of the Department of Health and Human Services (HHS) to research Americans’ exposure to radioactive iodine. The National Cancer Institute (NCI) was directed to conduct a study, and for 14 years the organization examined every county in the nation in an attempt to gauge which regions saw the most exposure. Last fall, after much criticism over alleged foot-dragging, the Institute issued its 100,000-page study. The NCI concluded that radioactive iodine from atomic blasts was deposited in every state, with the largest doses in the area immediately downwind of the NTS and the smallest doses along the west cost. Overall, Americans’ exposure to Iodine 131 from nuclear testing in the 1950s was about 2 "rad," a measurement of energy deposition. "To put this amount of exposure in perspective," NCI Director Richard Klausner told a congressional subcommittee, "routine medical use of x-rays during the 1940s and 1950s exposed children to anywhere from 5 to several hundred rad, and all persons receive doses from natural background radiation of about .1 rad per year." To its credit, the NCI enumerated the weaknesses of its methodology. Perhaps the Institute’s biggest problem was the short half-life of Iodine 131. In only eight days, half of the substance’s radioactivity decays. Since no atmospheric nuclear tests have been performed for 40 years, little Iodine 131 remains. Other problems with the NCI’s study included its reliance on computer models for both weather patterns and cattle grazing behavior, and the wide variance of Americans’ milk consumption. "[T]he uncertainties associated with thyroid dose estimates are fairly large," Klausner admitted.

The Overreaction

While the NCI was not charged with establishing a connection between Iodine 131 and thyroid cancer—its focus was the amount of exposure—a separate memorandum to its report did suggest a "worst-case scenario" of 75,000 childhood cancer cases resulting from atomic blasts. Not surprisingly, this figure was immediately seized upon by the media. America’s general paranoia about all things nuclear—combined with the violent image of mushroom clouds in the Nevada desert—played into the hands of activists as well. The worst-case scenario figure seemed to confirm what alarmists had been saying for years. Author Simon Walters felt vindicated: "We keep paying and paying for atomic testing. Generations from now, the bill will still be coming due." Discussions of compensation to possible victims began, and the Clinton administration dutifully assigned the Institute of Medicine (IOM) and National Research Council (NRC) to assess the implications of the NCI’s findings and recommend how the federal government should proceed.

The Rest of the Story

Two weeks ago, the IOM and NRC reached conclusions which surely disappointed fallout alarmists. While praising the NCI for its exhaustive research, the two agencies found "little evidence of widespread increases in thyroid cancer related to the patterns of Iodine 131 exposure described in the NCI report." IOM/NRC researchers echoed a point made several times by the NCI—that what limited data there is on childhood exposure to iodine has provided "suggestive but not conclusive evidence that it is linked to thyroid cancer." The IOM/NCR team also stressed that thyroid cancer remains quite rare—it accounts for less than 1 percent of all cancer deaths per year—and 90 percent of those with the disease live for at least another 30 years. The report recommended not a national screening program, but a public information campaign aimed at those concerned about "the likely (albeit small) risk of thyroid cancer linked to exposure to Iodine 131 from the Nevada atomic weapons tests."

"The legacy of [nuclear testing] and its aftermath," the report stated, "is considerable and sometimes intense distrust of government as a source of information and advice and a segment of the public that is convinced the health impacts of exposure are significant and severe." Although not saying so explicitly, the report seems to suggest that fallout concerns are hyped by those unwilling or unable to view the research objectively. (It was not surprising when the left-wing Physicians for Social Responsibility "expressed dismay at the omissions and limitations" of the IOM/NCR analysis.)


The atomic blasts set off in Southern Nevada in the 1950s exposed millions of Americans to low-level radiation—that much is certain. And indeed, the federal government should have done a better job communicating the possible dangers of fallout to citizens at the start of the testing. But hysteria over the dangers of radioactive iodine is unwarranted. No link has yet been established between Iodine 131 and thyroid cancer. Furthermore, thyroid cancer is extremely rare, and highly curable. As public health risks go, exposure to radioactive iodine from atmospheric nuclear detonations is minuscule. Nuclear testing in Nevada, despite the suspicions of many citizens and the claims of some activists, did not severely irradiate the nation.

D. Dowd Muska, a non-smoker, is a contributing editor for Nevada Journal, the Nevada Policy Research Institute’s monthly magazine. He can be contacted at