Can a microwave oven cause a pacemaker to malfunction?

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Dear Cecil: I believe the “pacemaker danger” signs people put up around microwave ovens are silly and baseless. Surely they spring from some lawyer worried about a suit. Please tell us the real deal. Nukem All, Houston


Illustration by Slug Signorino

Cecil replies:

Here at the Straight Dope we speak to the universal human condition. However, we recognize that a large part of our audience consists of baby boomers who, judging from the mail, are getting pretty long in the tooth. Consider the trend in subject matter:

  • ’70s. How do I get rid of the aphids in my marijuana plants?
  • ’80s. I don’t want to boink near as often as I used to.
  • ’90s. Kids these days.
  • ’00s. Pacemakers.

Sure, the pacemaker thing is a little premature. But I understand your feelings, Nuke. No harm being prepared.

As you rightly suspect, current medical opinion is that concerns about microwave ovens frying your pacemaker are, if not silly and baseless, certainly exaggerated given the precautions currently taken in manufacturing these devices. “In the early days of microwave ovens and cardiac pacemakers, there was a real possibility that a leaky oven with a significant electromagnetic field being emitted could interfere with operation of a pacemaker with an unshielded lead,” reads one typical bit of advice (Occupational Medicine Forum, Journal of Occupational Medicine, 1992). “Both problems have since been corrected.” The U.S. standard for microwave ovens limits energy leakage to five milliwatts per square centimeter at a distance of five centimeters, and cardiac pacemakers now have shielded leads.

But it’s no fun being a journalist if you can’t scare the pants off people once in a while. I scoured the medical journals for microwave horror stories. Pickings were slim, but I did turn up the following:

  • In 1983 an engineer working at a 275,000-volt electrical substation in the UK felt a thumping sensation in his chest when he was near high-voltage conductors. Experiments established that the electromagnetic field generated by the high voltage was interfering with the man’s pacemaker. A 275,000-volt electrical substation presumably generates a stronger electrical field than a microwave oven, and UK power operates at 50 cycles per second, compared to 2.45 billion cycles per second for ovens. But let’s not get technical. The lesson is clear: electricity + pacemakers = bad. The proposed solution, incidentally, was to outfit the guy with a geeky whole-body electricity-conducting protective suit that made him look like Nanook of the North. Faced with wearing one of these things on a hot day, or merely being seen in one, I’d be inclined to investigate a different line of work.
  • In 1984 a 51-year-old man wearing a transdermal patch (used to deliver drugs through the skin) was sitting near his mother’s microwave oven when she turned it on. The patch, which was on the man’s chest, became hot, and before he could pull it off it gave him a second-degree burn. Apparently the oven had been improperly repaired and was leaking microwave energy, which was absorbed by an adhesive strip of aluminized plastic on the patch. OK, a transdermal patch isn’t a pacemaker, but we need to look at the big picture. Not that the guy gets any sympathy from me. What’s a 51-year-old man doing having his mother make him dinner?
  • Deaf people have been known to pick up CB radio transmissions on their cochlear implants. This is getting pretty far afield even by my standards, so let’s leave it at that.

The occasional sign stuck on an oven notwithstanding, fears about microwaves have largely subsided in recent years, even among the paranoid element. A more common rant nowadays runs, “Nobody sticks his head inside a microwave oven. But a cellular telephone emits dangerous radiation ONLY MILLIMETERS FROM YOUR BRAIN!” You didn’t ask me to delve into that particular can of worms, though, and no way am I going to volunteer.

Cecil Adams

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