Q: Is it true that microwave popcorn contains substances that cause cancer?
A: No, but at least one ingredient, when inhaled regularly, can cause lung damage—what has been dubbed “popcorn lung.” The suspect chemical, diacetyl, is found naturally in foods such as yogurt, wine, butter, and cheese, but the trouble comes from the synthesized diacetyl added to impart an artificial buttery flavor and smell to popcorn. Diacetyl is also used in some flavored e-cigarettes and in tobacco.
Popcorn lung is an irreversible, debilitating, and potentially fatal lung disease. The term was coined when workers in factories producing popcorn or their flavoring developed the respiratory condition, medically known as bronchiolitis obliterans. This inflammatory disease obstructs the small airways of the lung, causing chronic cough and severe shortness of breath.
It wasn’t until a middle-aged popcorn lover came down with this condition—and was awarded $7 million in damages in 2012when he sued the manufacturer and retailers—that the public heard about popcorn lung. The plaintiff reportedly inhaled the buttery vapors from two or three bags of extra-butter-flavored microwave popcorn nearly every day for seven years.
When the Center for Science in the Public Interest (CSPI) recently contacted major microwave popcorn manufacturers, all claimed they had switched from diacetyl to a similar chemical additive, 2,3-pentanedione. This may also be unsafe when inhaled, at least according to animal data. Neither chemical is named on ingredients lists; they are simply included under “artificial flavorings.”
Microwave popcorn bags may be lined with other potentially harmful chemicals, notably PFOS (perfluorooctane sulfonate). This chemical prevents oil from migrating through the bag and is found not just in microwave popcorn bags but also in some fast-food wrappers, pizza boxes and other food wrappings. Because of concerns regarding its toxic effects, including its hormonal effects and the link to thyroid disease and various cancers, the FDA recently banned PFOS in all food packaging.
The biggest concern with chemicals such as diacetyl and PFOS is for occupational exposure. There’s no reason to panic if you eat microwave popcorn occasionally. Still, it’s always wise to have good ventilation in your kitchen, since smoke and fumes from cooking contain an array of risky chemicals. CSPI recommends allowing a bag of microwave popcorn to cool before opening it—or opening it under a ventilation hood or near an exhaust fan, if you have one. If you buy microwave popcorn, compare labels for calories and sodium, and avoid brands that still have partially hydrogenated oils, which contain trans fat. Better yet, pop plain kernels on your own.
Also see Picking a Popcorn.