Future Tense

Going Out With a Bang

As pacemakers and other implantable devices become more common, so are crematoria explosions.

Is your pacemaker oven-safe?


In 1958, a plucky engineer used a Kiwi shoe polish tin as a mold to create the world’s first implantable pacemaker. Since then, others have copied the basic design of that early device—a battery and assorted circuitry encased in a sealed chamber—to produce an array of futuristic implantables: continuous glucose and blood pressure monitors, bowel and bladder stimulators, neurologic pulse generators, and enough biorobotic capsules and sensors to make the Six Million Dollar Man look more like the Tin Man. The implantable medical device sector is now thriving, with a market value projected to top $26 billion by 2022. Cardiovascular devices still lead the category, with over 700,000 pacemakers implanted worldwide each year. Many of today’s battery-powered implantables store a wealth of data helpful in diagnosis and treatment, and some directly intervene to keep users alive.

But after patients die, these trippy devices can become booby traps.

In the United States, most of the deceased are destined for cremation—an option that eclipsed burial for the first time last year. But when people whose bodies contain certain medical device implants go through the blazing hot incineration process, they may literally go out with a bang.

In fact, one study found that nearly half of crematoria staff in the U.K. reported having experienced a pacemaker explosion in their facility. Statistics for the U.S. are scarce, perhaps because letting it get out that you blew up someone’s grandfather wouldn’t be good for business. But at least one recent report suggests that the risk of such mishaps is escalating in countries where both medical device implantation and cremation are becoming increasingly popular.

Technological advances are making the possibility of such incidents more worrisome. For starters, batteries in pacemakers and other implants are getting smaller and more energy-dense. Energy density is the amount of stored energy a battery contains relative to its size. (If your eyes just glazed over, bear with me. We’ll get back to the exploding corpses in a jiff.) The batteries in most of today’s medical devices use small but powerful lithium metal anodes paired with cathodes composed of iodine, carbon monofluoride, silver vanadium, or other materials. In the intense heat of the cremation chamber, which tops out at 1800 degrees Fahrenheit, these elements emit a highly flammable gas. As the gas expands, a frenzied chemical reaction occurs. All the energy stored in the device—enough to power it for several years—gets discharged in less than a second. The gas within the sealed casing ignites, essentially turning the device into a bomb that detonates, producing shrapnel, molten metal, and toxic smoke.

Such an explosion might be undignified, but it’s unlikely to interfere with cremation of the body. The dispersed remains would be incinerated and any metal shards removed from the ash with a magnet. The blast could, however, damage the brick walls, concrete floor, and even the metal door of the cremation chamber. More significantly, the explosion could cause serious harm to anyone in the room when it happens. Many crematoria have rules requiring that the door remain closed for the duration of the process, which would contain such a blast. But anyone who’s ever baked a soufflé knows how tempting it is to take a peek now and then.

“Crematory operators often open the door of the machine to monitor the progress of the body,” Caitlin Doughty, author of From Here to Eternity: Traveling the World to Find the Good Death, explained to me. “If they happen to open the door at the moment an explosion occurs, it would obviously be incredibly dangerous.” (If you’re curious, you can watch a video of the process here. Don’t worry—it’s not graphic.) Those present for the cremation could be burned or injured by the shrapnel, which can cause eye trauma or other wounds.

Because the funeral industry has a low overall rate of on-the-job injury, crematoriums aren’t required to report workplace accidents to the Occupational Safety and Health Administration—so whether or how often such incidents occur would be hard to track in the U.S. Barbara Kemmis, executive director of the Cremation Association of North America, told me she’s not aware of any device-related blast injuries. But she agrees there’s a risk.

Of course, removing such devices from the body before cremation would seem to be the obvious solution. But that’s not so simple. Though standard cremation authorization forms require disclosure of pacemakers and other “hazardous implants,” individuals sometimes give information that’s inaccurate or incomplete. The family may forget or not know a loved one had an implanted device. Or they may know but not want to pay for the cost of removal and decide to take their chances, hoping the implant will be destroyed along with the body. If staff don’t know to look for them, these tiny devices, such as new models of pacemakers that are small enough to be threaded through a vein, can be difficult for mortuary staff to detect and retrieve.

Some crematoriums use handheld metal detectors to check for undisclosed implants. But contradicting earlier evidence, recent studies published in Heart Asia and the New England Journal of Medicine report that TSA-style wands can’t reliably pick up on leadless pacemakers buried deep within the heart. What’s more, placement of many modern devices is accomplished using minimally invasive techniques, which leave no obvious scars or other evidence that might prompt mortuary staff to double-check the paperwork or make inquiries. Likewise, placement of sensors may leave no physical clues. Some capsular devices, such as ingestible endoscopes (pillcams), are simply swallowed, making their location hard to pinpoint even in live patients.

Even when they know to look for them, in many instances staff are told not to retrieve these miniaturized devices. In a white paper on the explosive potential of its popular transcatheter pacing system (dubbed “the world’s smallest pacemaker”), Medtronic, the world’s leading medical device manufacturer, recommends that the unit not be removed, or “explanted,” for cremation. The risk of infectious disease transmission to staff preparing the body, the paper suggests, outweighs the risk of blast injury. Point taken.

(Update, Nov. 2, 2017: Medtronic reached out after this article was published to clarify that the company concluded, based on internal and third-party testing, that its Micra transcatheter pacing system can be safely cremated without causing a noticeable explosion, damage to crematoria equipment, or risk to staff or those attending cremation ceremonies.)

A traditional pacemaker lies just beneath the skin. Removing it is no more complicated than deveining a shrimp. (The new death-positive video game A Mortician’s Tale lets players simulate this process using an animated scalpel and forceps.) To retrieve this newer style of pacemaker, on the other hand, the mortician must open the chest and make an incision into the heart itself. It can get messy.

According to Kemmis, if a crematorium worker finds an undisclosed device, the funeral director may be called in to take custody of the body. The implant would then be removed by mortuary staff or the body would be buried, depending on the type of device, the manufacturer’s recommendations, state law, the family’s wishes, and the mortuary’s policies.

Families and funeral directors may soon be spared these awkward snafus and their associated hazards. Bioengineers and materials scientists have already devised a clever sort of organic battery that could, among other benefits, eliminate battery-related explosion hazards altogether. Rising bioelectronics star Islam Mosa, for example, is working to develop a battery-less power source that uses electrolytes in blood or other body fluids to replace the chemical medium used for energy delivery in existing commercial batteries. Other researchers are investigating ways of using solar energy, kinetic energy, radiofrequency radiation, or even energy generated by the heart muscle itself to power implantables.

Such technology could be clinically viable and market ready in as little as six years, Mosa told me. But some fear that manufacturers, physicians, and hospitals may slow down the process (after all, periodic replacement of battery-powered medical devices can yield handsome financial rewards).

Until more stable batteries or battery substitutes become available, patients and their families should educate themselves about the options for handling an implanted medical device after death. If a device can’t be incinerated, families can consider traditional embalming and burial or turn to greener alternatives, such as natural burial or alkaline hydrolysis (sometimes called “liquid” or “flameless” cremation). Mortuaries and crematoriums, too, can step up to prevent accidents by asking about specific If warranted kinds of medical device implants and sensors on cremation authorization forms. If warranted, the crematorium might also ask to review the deceased person’s medical records for clarification. Most significantly, manufacturers of these implantable devices need to issue recommendations for postmortem care of every implantable medical device they market. I asked Medtronic, for example, whether the company recommends that its new Intellis spinal cord neurostimulator be explanted before cremation, but company spokespeople responded with product-specific guidance on just the Micra transcatheter pacing system.

Sixty years ago, that first primitive pacemaker failed within hours. But the invention was nevertheless a watershed moment in medicine. It coupled an implantable device with wireless communication, a pairing that ultimately launched the mobile health revolution, streamlining the diagnosis and treatment of many conditions. Nifty advances in nanotechnology, microfabrication techniques, energy harvesting, and other areas will further integrate implantables with the Internet of Things and give patients a range of handy, painless ways to track their own health in real time.

Life was less convenient for the 43-year-old recipient of that first pacemaker. But he was lucky. He went through 22 more pacing devices, which kept him alive until 2001, when he died of cancer at age 86. No word on whether his body was cremated.

This article is part of Future Tense, a collaboration among Arizona State University, New America, and Slate. Future Tense explores the ways emerging technologies affect society, policy, and culture. To read more, follow us on Twitter and sign up for our weekly newsletter.