Our planet is home to many radioactive substances—not just in its geologic innards or its weapons caches but also in its hospitals, at its industrial sites and in its food processing plants. In Colorado, for instance, 27 buildings house scary-sounding elements such as cesium 137, cobalt 60, americium 241 and iridium 192.

These materials are not there for risky purposes, though. They play a part in cancer therapy, blood irradiation, medical and food sterilization, structure and equipment testing, geologic exploration and instrument calibration. Radioactive material is not always bad in a black-and-white way: it can be a useful tool. The gamma rays emitted by cesium and cobalt can kill germs multiplying in your meat and make your apples last longer. Radiographic instruments can detect, say, defects in a city’s pipes in a similar way to an x-ray picking up a hairline fracture in your patella. A practice called “well logging” uses sealed radioactive sources to map the geology of holes oil seekers drill into the earth. And of course, radiation is key to cancer treatment. Near the dawn of the nuclear age, the International Atomic Energy Agency (IAEA)—a global organization that reports to the United Nations—was established to promote peaceful nuclear applications while minimizing weaponization risks. In the ensuing years, the security risks from such nonviolent applications have increased, but so have less emissive alternatives to radioactive technology. Organizations such as the IAEA, along with domestic groups, are hoping to reduce reliance on such tech that could result in threats to safety.

The risk arises because the same radioactive material that is beneficial could also be stolen or misplaced and find its way into trafficking rings or dirty bombs. It might also harm workers if something accidentally goes wrong during a normal nine-to-five day. In 2017 alone, according to a report from the James Martin Center for Nonproliferation Studies, there were 171 “incidents of nuclear or other radioactive materials outside of regulatory control,” based on open source reports, 104 of which happened in the U.S. Historically, fear of the material falling into the wrong hands has focused on foreign extremist groups, but some experts suggest the risk may also be turning toward violent extremist groups stateside.

Both the material’s presence and its potential problems were news to Ryan Grothe, of Denver Police Department’s Special Operations Division. He received that news around 2018, courtesy of the Office of Radiological Security (ORS) at the Department of Energy’s National Nuclear Security Administration. “I doubt hardly anyone in this entire department really understood what was sitting within the city,” Grothe says.

Since Grothe got the call, he has been to two DOE sites—the Y-12 National Security Complex and Oak Ridge National Laboratory, both in Tennessee—to learn more about what the radioactive material is, why it is both handy and hazardous, how to protect humans and the material, what protection is already in place and what resources could help should the unthinkable occur. Back in Denver, Grothe created an in-person training program for officers, and ORS helped him produce a training video, provided facilities for doing drills and sent personal radiation detectors. With this new knowledge, Grothe has turned into what he calls a “rad nerd.”

Grothe’s current work with ORS is part of an initiative called RadSecure 100, which aims to remove or better secure energetic material in 100 U.S. cities. “Where is the most high-risk material located around the most people?” says Emily Adams, deputy director of ORS’s domestic program. “And that‘s how we got our 100.”

Replacement Options

In Colorado, ORS has now cleared two buildings of the concerning material, with another under contract. Eighteen now have upgraded security. From Fargo, N.D., to Greenville, S.C., and from Sioux Falls, S.D., to Salt Lake City, Utah, ORS is engaged in similar work.

Inside each metropolitan area, ORS presents two options to sites with emissive atoms: It can, with facilities’ voluntary permission, remove the radioactive devices and replace them with equivalent—or better—technology. Or it can help the sites improve their security.

Door number one is experts’ preferred option. After all, if a nonradiological tool can do the same job as a radioactive one, at a reasonable price, few reasons exist to continue with the riskier choice. Why use a switchblade to spread jam on toast when you can use a butter knife?

One removal-and-replacement success strategy involves swapping blood irradiators that use cesium 137 for those that rely on x-ray technology. “It’s the most straightforward replacement technology,” Adams says. With financial incentives to make the switch, many facilities already have. “People respond to that,” says Miles Pomper, a senior fellow at the James Martin Center for Nonproliferation Studies. “It’s not magic.”

Similarly, medical facilities have largely phased out the cobalt 60 machines that doctors once deployed for cancer treatment in favor of medical linear accelerators, or linacs, which offer more targeted treatment that does not do as much damage to surrounding tissue.

But aside from those two cases, “there are no broadly accepted replacement technologies for other applications,” according to a 2021 National Academies of Sciences, Engineering, and Medicine report. Given that reality, “get rid of it” cannot be ORS’s only option. For that reason, the RadSecure project also offers upgraded security, adding what officials call “detection and delay elements.” Motion sensors and tamper indicators can immediately let officials know something is up; hard-to-undo fasteners can buy time for first responders to arrive before a thief gets away. And a new ORS-sponsored app called Sentry-SECURE can send automatic alerts to law enforcement when something is amiss.

But police need to know what to do should the alarm sound. It is important, Adams says, “that they treat it like a national security kind of incident as opposed to maybe the theft of a bicycle.”

Through RadSecure, dozens of other cities are being offered the coaching that places such as Denver and people such as Grothe have gotten. “It’s just one of those threats—because it’s such a low probability, it’s put on the backburner,” Grothe says.

Still, high security at places such as hospitals is not an ideal solution, not only because stopping potential “rad trade” is not medical professionals’ primary concern or job. “You can try to put in guards and gates and all that kind of thing, but it just doesn’t work very well with the culture of the institution,” Pomper says. Similarly, at, say, an oil-drilling site, equipment with radioactive material is “just a tool, like a hammer,” not a city-threatening device, he adds. Asking nurses and geologists to change their focus to protection is complicated and distracts from the actual work. “The easiest security culture is not to have to worry about it,” Pomper says.

Weighing the Risk

Although someone could steal radioactive material for a dirty bomb at any time, the possibility is what is classically called a “low-probability, high-consequence” event. It is so low-probability, quantitatively, that no “radiological dispersal device” has ever gone off.

Qualitatively, concern has typically turned its eye toward extremist groups from outside the U.S. But the current American environment may—or maybe should—also slew the gaze inward. At least, that is the argument in a recent Bulletin of the Atomic Scientists article by analysts at the Henry L. Stimson Center, a policy research nonprofit, which contends that the U.S. should worry about domestic extremists slipping cesium up their sleeves. “There are plenty of examples where far-right extremists have, particularly recently, pursued acts of terrorism, acts of violence and historically radiological terrorism,” says Nickolas Roth, one of the authors of the article and now a senior director within the Nuclear Threat Initiative’s Global Material Security program.

Violent domestic ideologies concern him in part because some embrace the philosophy of “accelerationism”—the idea that society is bound to disintegrate, and someone could quicken that disintegration and so herald the revolution sooner. “Indiscriminate, highly destructive acts of terror—like a nuclear attack—are therefore perfect tools to sow chaos and accelerate this societal collapse,” the Bulletin of the Atomic Scientists article claims.

Roth notes that there is no public evidence that any such stateside groups could carry out a sophisticated attack with an actual nuclear bomb. But a dirty bomb, containing the sorts of material RadSecure wants to secure, does not require as much sophistication. “The barrier for entry for that kind of thing is much, much lower,” Roth says.

No matter who, if anyone, might be seeking the radiological material, getting those elements out of the equation decreases the risk. “Every time you eliminate one of these sources, you’re eliminating a potential target,” he says.

A Global Problem

RadSecure focuses on domestic radiation sources, but replacing cobalt and other radioactive substances is more complicated globally. For example, the linacs now populating the U.S. cannot just be plopped into hospitals in low- and middle-income countries. Linacs typically cost much more than their riskier alternatives, are more complex and require a steady power supply, specially trained professionals and costly maintenance plans for inevitable hiccups.

Given all that, replacing cobalt 60 machines does not always go well. The Black Lion Hospital in Addis Ababa, Ethiopia, for instance, got a linac in 2018, but when the National Academies prepared its 2021 report, the device still had not been commissioned. Lack of trained people and power outages plagued its early integration.

Pomper is part of a collaborative group that intends to fix such situations by building a less complicated, expensive or breakable modular linac. The group calls the hypothetical device STELLA, or Smart Technology to Extend Lives with Linear Accelerators, and is focused on deploying it in underserved geographical regions such as sub-Saharan Africa, where radiation therapy is lacking and terrorist activity is high. The team has a conceptual design and is looking for funding to build a prototype. “It’s not a big technological challenge,” says Manjit Dosanjh, lead of the STELLA project and a member of the International Cancer Experts Corps, which is driving the effort. But, she adds, “the proof of the pudding is in the eating.” If the team’s members cannot show medical partners in Africa, who have been part of the device development process, a prototype, then they cannot show that it works better than what already exists.

The concerns and solutions look different—and fuzzier,—in, say, Addis Ababa than they do in Denver—and the 99 other cities in RadSecure 100. But even with the uncertainties, Dosanjh is sure of one thing: “We have to provide solutions for the world,” she says, “because we are no longer disconnected.”

This reporting was supported by the International Women’s Media Foundation’s Howard G Buffett Fund for Women Journalists.