How Science and Advocacy Ended Dangerous Nuclear Testing in the United States
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If you had opened up a newspaper 50 years ago, there is a good chance you would be reading about the latest nuclear explosion over your cup of coffee. Nuclear weapons have only been used twice in war, but more than 2,000 nuclear weapons were detonated during the Cold War. From 1945 to 1992, the United States alone conducted 1,030 nuclear tests—far more than any other country.
A sobering time-lapse video by Japanese artist Isao Hashimoto maps this period of widespread nuclear testing, showing the dramatic increase in frequency and geographic spread of nuclear testing over a short period of time. These explosions may not have been acts of war, but they were still attacks on peace, human health, and the environment.
Fortunately, this era of widespread nuclear testing ended, thanks in large part to dedicated work from scientists and activists. They had the courage and vision to challenge what seemed “normal.” By educating others and organizing for change, they succeeded in their fight for a more secure and sustainable future. But that future is under threat as allies of the Trump administration call for the United States to resume nuclear testing. We all have a responsibility to prevent that from happening, and the Union of Concerned Scientists is taking action.
In the early years of the Cold War, hundreds of nuclear explosions were detonated aboveground or underwater, often on colonized and Indigenous land. Radioactive materials from these nuclear tests mixed with debris from the blast, fell to the earth with rain, or were spread by the wind, exposing hundreds of thousands of people to dangerous levels of radiation.
The fallout from atmospheric tests created a global health crisis—and scientists raised the alarm. In 1958, a team of physicians in St. Louis launched the Baby Tooth Survey to evaluate how radioactive materials from nuclear testing were affecting the population—particularly children.
Strontium-90, a radioactive isotope produced by nuclear explosions, is chemically similar to calcium. When ingested, it can be incorporated into bones and teeth. In St. Louis, the success of the Baby Tooth Survey relied on an extensive community network: dentists, doctors, librarians, and school officials who spread the word about the survey, and through this grassroots outreach, the project ultimately collected 300,000 baby teeth from local children between 1958 and 1970.
From this dataset, scientists demonstrated that levels of strontium-90 in children’s teeth had increased significantly, with the sharpest rises occurring during periods of extensive nuclear testing. This significant increase occurred despite St. Louis being located more than a thousand miles from the nearest test site in Nevada, indicating the far-reaching effects of radioactive fallout.
This type of evidence galvanized public opposition to nuclear testing, ultimately convincing leaders to sign the Partial Test Ban Treaty in 1963. This treaty, still in force today, prohibits nuclear testing in any environment that would allow radioactive material to spread across a country’s borders, including atmospheric tests, underwater tests, and tests in outer space.
While the Partial Test Ban Treaty was a major step toward reducing the environmental and health risks associated with nuclear fallout, it did not end nuclear testing programs. Instead, it drove them underground. Conducted in drilled holes or tunnels, underground nuclear tests are designed to contain the dangerous byproducts of a nuclear explosion. However, unintended releases of radiation can still occur when gases and particles escape to the surface or migrate away from the test site through processes like groundwater movement.
Underground tests also continued to contribute to the dangerous nuclear competition between states that characterized the Cold War. Countries used nuclear testing both to develop new weapons technologies and to send threats about their military capabilities. To prevent the spread of nuclear weapons to new countries and work towards global disarmament, it was clear that nuclear testing would have to be eliminated first.
Because of the environmental and geopolitical risks associated with competition over nuclear weapons, opponents of nuclear testing set their sights on the ambitious goal of an international treaty for the complete elimination of testing. One of the biggest obstacles to such an agreement was the fear that countries could “cheat” by conducting underground tests in secret.
In 1976, the Group of Scientific Experts was founded to investigate the challenges of verifying a comprehensive test ban. This international cohort of scientists worked for 20 years to develop a seismic verification system that could detect underground nuclear tests anywhere in the world. Their efforts were critical to the negotiation of the 1996 Comprehensive Test Ban Treaty that prohibits any explosive nuclear test, regardless of yield or environment.
While the treaty has been signed by 187 countries, it has not yet entered into force due to non-ratification by a handful of key states, including China and the United States. Nevertheless, the treaty has established a powerful norm: no country other than North Korea has conducted a nuclear test in the 21st century, and North Korea’s tests were met with international condemnation and heavy sanctions.
Even without explosive testing, nuclear-armed states are able to maintain confidence in the safety and reliability of their arsenals. Ever since the United States voluntarily suspended its nuclear testing program in 1992, US scientists have worked constantly to ensure that the US nuclear stockpile is safe, without needing to conduct further nuclear tests. Each year, the directors of the US nuclear weapons laboratories and the commander of the US Strategic Command review and certify the safety and reliability of each nuclear weapon type through a program of science-based stockpile stewardship. This entails a combination of non-nuclear laboratory experiments, advanced computer simulations, and forensic monitoring of the health of existing weapons.
During the Cold War, it took uncommon vision to imagine a world without widespread nuclear testing. But scientists and activists worked tirelessly to help secure that world for us. Now it is difficult to imagine going back.
Unfortunately, there have always been voices calling for a return to nuclear testing, and the second Trump administration has emboldened those voices. A US president can order the resumption of nuclear testing for any reason, but today we know more than ever about the dangers of nuclear testing, and scientists and activists are pushing back. Even one nuclear test in the deserts of Nevada could usher in a new era of widespread nuclear testing in other parts of the world—a new era marred by the relentless, reckless detonation of nuclear bombs.
Fortunately, this is a fight we have won before, and it is a fight we will win again—by building community, sharing knowledge, and forcing our leaders to take action. Understanding the scientific, environmental, and geopolitical consequences of nuclear testing remains essential. The experience of the Baby Tooth Survey, the success of the Partial Test Ban Treaty and Comprehensive Test Ban Treaty frameworks, and the evolution of stockpile stewardship all illustrate how scientific expertise can shape responsible policy.
More than 50 years ago, scientists and activists helped change the course of nuclear history by documenting the invisible harms of fallout and sharing that knowledge with the public. Their efforts helped shift global policy away from tolerating open-air detonations and towards greater accountability and safety. Today, their legacy endures. By helping people understand the true effects of nuclear use and nuclear war, history shows that scientific engagement—combined with public pressure—can lead to meaningful and lasting change.