Updated on November 16, 2017

As a child of the ’90s, I’ll forever be a tiny bit terrified of the radioactive potential of microwaves, and standing too close to them. My natural inclination is to watch my food closely, which meant my mother had to tell me to take my face away from the microwave door as soon as I was tall enough to reach it. When I made instant oatmeal or Swiss Miss or the occasional hot Pop-Tart (very different from the toasted Pop-Tart) I would place them in the microwave, step back, and stand a foot to the side of it, like the microwave had peripheral vision I was trying to avoid. I have no scientific knowledge about the radioactive range of the average microwave, but I treat them like the sun: Don’t look directly at it, and you will be fine.

So imagine my shock and dismay when my own editor alerted me to a condition she’d heard of years ago (but brand-new to me) called “popcorn lung.” Despite the relatively jocular-sounding name, popcorn lung is the nickname given to bronchiolitis obliterans, a condition which causes coughing and shortness of breath—and a condition which is thought to be caused, at least sometimes, by diacetyl—a chemical sometimes used to flavor microwave popcorn. What if, all along, the most dire threat posed to me by my microwave was not radiation, but every packet of delicious, buttery popcorn I’ve ever consumed?

To find out, I got in touch with Len Horovitz, a pulmonary specialist at Lenox Hill Hospital in New York. First of all, he agrees “popcorn lung” is not the best name in the world. “It’s a little bit of a misnomer, because it almost makes you think the lungs, on close inspection, would look like popcorn,” he says. I didn’t even think of that but now it’s all I can think about.

Horovitz puts popcorn lung in the same “cauldron,” he says, as interstitial lung diseases (ILDs), a large group of disorders causing scarring of the lung tissue. Some ILDs are caused by behavioral factors, like smoking—a condition which Horovitz says is called bronchiolitis obliterans organizing pneumonia, or, hilariously, BOOP. Other ILDs are thought to be caused by chemical exposure—Horovitz cites those suffered by 9/11 first responders as an example. Popcorn lung would also fall in this camp. “It seems to be the case that when you microwave popcorn, especially when you're doing it in these bags, the bag expands, you pop the bag, and the steam and some sort of chemical—maybe some vegetable-oil metabolite—comes out,” says Horovitz.

One’s risk for popcorn lung—and other ILDs—is greatly increased among smokers, though nonsmokers can get them too, particularly if their line of work puts them in frequent contact with dangerous chemicals. “You usually find in the causation some sort of exposure that most of us aren't exposed to. Maybe they live over the Lincoln Tunnel, or they worked in a chemical plant,” says Horovitz. In other words, microwaving popcorn is not so much a cause of popcorn lung as it is a potential correlation. And less so than it used to be—many microwave popcorn manufacturers announced in 2007 that they would remove diacetyl from their products.

While an otherwise healthy person may be unlikely to contract popcorn lung, there is, as always, plenty to be said for using common sense. What that means, in this case, is: Don’t stick your face in a steaming-hot bag of microwave popcorn. Don’t be like the guy who popularized this condition in the first place with a high-profile lawsuit, who ate two bags a day, and inhaled their steam on purpose. “The average person should always be worried about smells in unventilated areas,” says Horovitz. “You're not supposed to mix Clorox and ammonia in your toilet bowl. You should always work in a well-ventilated area any time you're working with chemicals.” That means cleaning supplies and gasoline and paint, but it also, apparently, means microwave popcorn. To protect oneself, Horovitz suggests keeping a window open, or using an “out fan,” or exhaust fan, to keep the room ventilated. Don’t open your popcorn right away, and don’t open it right under your nose. “Let it sit out and try to wait until the gases have escaped,” adds Horovitz.

Horovitz emphasizes that bronchiolitis obliterans, like other ILDs, is not common. In fact, he says ILDs are “certainly not common the way infection and pneumonia and asthma and even lung cancer are common,” which gave me a whole host of things to worry about. It’s still not entirely clear what threat our microwaves pose to our health. But is it fairly easy to stand to the side of them, just in case, and keep our heads at safe distances from the popcorn they cook for us? Yes. So we might as well.

This story has been updated to reflect announcements from several major microwave popcorn manufacturers that say they have removed diacetyl from their products. The original version of this article also used “Orville Redenbacher” as a shorthand for microwave popcorn generally. We have removed this reference.