At least 340,000 Americans died from radioactive fallout between 1951 and 1973

Domestic nuclear testing wreaked havoc on thousands of families.

At least 340,000 Americans died from radioactive fallout between 1951 and 1973
Wikimedia Commons
  • Hiroshima and Nagasaki resulted in the deaths of hundreds of thousands. But new research shows that domestic U.S. nuclear tests likely killed more.
  • The new research tracked an unlikely vector for radioactive transmission: dairy cows.
  • The study serves as a reminder of the insidious and deadly nature of nuclear weapons.

When we think of nuclear disasters, a few names probably come to mind. There's the Chernobyl disaster, which killed around 27,000 people, although estimates are fuzzy. After Fukushima, there were no deaths due to radiation poisoning, but this event occurred relatively recently, and radiation poisoning often kills slowly over decades. When the U.S. dropped atomic bombs on Hiroshima and Nagasaki, estimates put the death toll at around 200,000 people, but again, exact numbers are difficult to calculate.

One name that almost certainly didn't come to mind is Nevada. When the Soviet Union detonated their first atomic bomb in 1949, the U.S. was shocked into action. America's prior nuclear testing had been carried out in the Pacific, but it was logistically slow and costly to conduct tests there. In order to maintain dominance over the growing Soviet threat, the U.S. selected a 1,375 square-mile area in Nye County, Nevada.

This was an ideal spot for several reasons. It was closer than Bikini Atoll. The weather was predictable and very dry, reducing the risk that radioactive fallout would be dispersed by rainstorms. It was sparsely populated. There was an understanding that there would be some amount of risk posed to nearby civilians, but it was deemed acceptable at the time. The trouble is, our understanding of radioactive fallout was still in its infancy. It was a catch-22; the only way to learn more was to test nuclear weapons.

New research with a wider scope

Subsidence craters at the Nevada test site. These craters result from underground weapons testing, typically from nuclear weapons. Federal Government of the United States [Public domain], via Wikimedia Commons

In the 1950s, the U.S. government downplayed the danger of radioactive fallout, asserting that all radioactivity was confined to the Nevada test site. Despite this, a national estimate attributed 49,000 cancer deaths to nuclear testing in the area.

But the results of new research suggest that this number is woefully inaccurate. Using a novel method, and today's improved understanding of radioactive fallout, Keith Meyers from the University of Arizona discovered that U.S. nuclear testing was responsible for the deaths of at least as many — and likely more — as those killed by the nuclear bombs in Hiroshima and Nagasaki. Specifically, between 340,000 and 690,000 Americans died from radioactive fallout from 1951 to 1973.

Prior studies generally looked at the areas surrounded the Nevada test site and estimated the deaths caused by fallout from the area. This number was relatively low, owing to the dry, predictable weather mentioned earlier. However, the bulk of the deaths were actually dispersed throughout the country, primarily in the Midwest and Northeast regions. These deaths were caused by an unfortunate synergy between meteorology, radiation, and — perhaps oddly enough — cows.

An unforeseen vector of radiation poisoning

Through an unforeseen chain of events, dairy cows became a vector for radioactive poisoning. ROBYN BECK/AFP/Getty Image

Out of all the radioactive elements produced by a nuclear explosion, iodine-131 was the biggest killer. I-131 has an eight-day half-life, tends to accumulate in the thyroid gland, and emits beta and gamma radiation. While alpha radiation is generally weak and doesn't penetrate material very well, beta and gamma radiation are highly energetic and shoot through clothing and flesh, ripping up DNA as it goes along.

Prior studies had examined the radioactive fallout dispersed by low-altitude winds, which would generally settle around the Nevada test site. However, a significant amount of I-131 was caught up in high-altitude winds. These winds carried the radioactive particles to other regions of the U.S., where it mixed with rain clouds.

The now-radioactive rain fell onto the grasslands in the Midwest and Northeast. Then, cows ate the now-radioactive grass. The cows then produced radioactive milk. Dairy practices during the study period were different than they are today — most people drank milk that had recently been extracted from local cows.

Thanks to a National Cancer Institute database that contains broad data on radiation exposure, Meyers was able to track the amount of I-131 found in local milk and compare this with the number and nature of deaths on a county level. In this way, Meyers was able to determine that a significant number of these deaths were due to drinking poisoned milk. These civilians would have had no idea that the milk they were drinking had been irradiated by nuclear explosions hundreds of miles away.

Ironically, the area around the Nevada test site didn't have this problem. Although they too drank fresh milk from local cows, they imported hay from other parts of the country. Since their cows weren't eating irradiated hay, the local Nevadans took in significantly less radioactive material than their less-fortunate, distant countrymen.

Although our understanding of radiation and nuclear fallout is much improved since the dawn of the nuclear age, the study serves as a warning of the insidious nature of nuclear weapons. Containing nuclear fallout is challenging, even when you know where all of the vectors of radioactive transmission are. The complexity and intertwining nature of our ecological and social systems means that words like "clean," "precise," or "surgical" will likely never apply to nuclear weapons.

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The theory could resolve some unanswered questions.

Image source: NASA/Big Think
Surprising Science
  • Most stars begin in binary systems, why not ours?
  • Puzzles posed by the Oort cloud and the possibility of Planet 9 may be solved by a new theory of our sun's lost companion.
  • The sun and its partner would have become separated long, long ago.

If most stars form in binary pairs, what about our Sun? A new paper presents a model supporting the theory that the Sun may have started out as one member of a temporary binary system. There's a certain elegance to the idea — if it's true, this origin story could resolve some vexing solar-system puzzles, among them the genesis of the Oort Cloud, and the presence of massive captured objects like a Planet Nine.

The paper is published in Astrophysical Journal Letters.

The Oort cloud

Oort Cloud graphic

Image source: NASA

Scientist believe that surrounding the generally flat solar system is a spherical shell comprised of more than a trillion icy objects more than a mile wide. This is the Oort cloud, and it's likely the source of our solar system's long-term comets — objects that take 200 years or more to orbit the Sun. Inside that shell and surrounding the planets is the Kuiper Belt, a flat disk of scattered objects considered the source of shorter-term comets.

Long-term comets come at us from all directions and astronomers at first suspected their origins to be random. However, it turns out their likely trajectories lead back to a shared aphelion between 2,000 astronomical units (AU) from the Sun to about 100,000 AU, with their different points of origin revealing the shell shape of the Oort cloud along that common aphelion. (An astronomical unit is the distance from the Sun to the Earth.)

No object in the Oort cloud has been directly observed, though Voyager 1 and 2, New Horizons, and Pioneer 10 and 11 are all en route. (The cloud is so far away that all five of the craft will be dead by the time they get there.) To derive a clearer view of the Oort cloud absent actually imagery, scientists utilize computer models based on planetary orbits, solar-system formation simulations, and comet trajectories.

It's generally assumed that the Oort cloud is comprised of debris from the formation of the solar system and neighboring systems, stuff from other systems that we somehow captured. However, says paper co-author Amir Siraj of Harvard, "previous models have had difficulty producing the expected ratio between scattered disk objects and outer Oort cloud objects." As an answer to that, he says, "the binary capture model offers significant improvement and refinement, which is seemingly obvious in retrospect: most sun-like stars are born with binary companions."

"Binary systems are far more efficient at capturing objects than are single stars," co-author Ari Loeb, also of Harvard, explains. "If the Oort cloud formed as [indirectly] observed, it would imply that the sun did in fact have a companion of similar mass that was lost before the sun left its birth cluster."

Working out the source of the objects in the Oort cloud is more than just an interesting astronomical riddle, says Siraj. "Objects in the outer Oort Cloud may have played important roles in Earth's history, such as possibly delivering water to Earth and causing the extinction of the dinosaurs. Understanding their origins is important."

Planet 9

rendering of a planet in space

Image source: Caltech/R. Hurt (IPAC)/NASA

The gravitational pull resulting from a binary companion to the Sun may also help explain another intriguing phenomenon: the warping of orbital paths either by something big beyond Pluto — a Planet 9, perhaps — or smaller trans-Neptunian objects closer in, at the outer edges of the Kuiper Belt.

"The puzzle is not only regarding the Oort clouds, but also extreme trans-Neptunian objects, like the potential Planet Nine," Loeb says. "It is unclear where they came from, and our new model predicts that there should be more objects with a similar orbital orientation to [a] Planet Nine."

The authors are looking forward to the upcoming Vera C. Rubin Observatory (VRO) , a Large Synoptic Survey Telescope expected to capture its first light from the cosmos in 2021. It's expected that the VRO will definitively confirm or dismiss the existence of Planet 9. Siraj says, "If the VRO verifies the existence of Planet Nine, and a captured origin, and also finds a population of similarly captured dwarf planets, then the binary model will be favored over the lone stellar history that has been long-assumed."

Missing in action

Lord and Siraj consider it unsurprising that we see no clear sign of the Sun's former companion at this point. Says Loeb, "Passing stars in the birth cluster would have removed the companion from the sun through their gravitational influence. He adds that, "Before the loss of the binary, however, the solar system already would have captured its outer envelope of objects, namely the Oort cloud and the Planet Nine population."

So, where'd it go? Siraj answers, "The sun's long-lost companion could now be anywhere in the Milky Way."

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