The Cancer Risk of Microwave Popcorn

There are lots of headlines swirling around the internet connecting microwave popcorn and cancer and claiming that microwave popcorn is one of the worst things you can eat, but are the claims true? And how do you differentiate between what's fact and what's fiction?

While there's nothing that connects the microwave popcorn itself to cancer, there are problems with some of the ingredients that are in the lining of the microwaveable bags. However, after some microwave popcorn brands got wind of potential problems with their packaging, they switched to safer alternatives.

One of the problems with microwave popcorn lies in the microwave-safe bag that houses the kernels. According to a December 2013 report in Environmental Health Perspectives, microwave popcorn bags contain chemicals called perfluorooctanoic acid (or PFOA), which is the same chemical used in Teflon® nonstick coating, and perfluorooctane sulfonate (or PFOS).

The same report notes that PFOA has been connected to kidney cancer and testicular cancer, as well as ulcerative colitis, thyroid disease, high cholesterol and high blood pressure during pregnancy. A February 2017 study that was published in the Journal of Endocrinological Investigation took a deeper dive into the effect on the thyroid and connected the chemicals to hypothyroidism, especially in women.

Read more: Can You Eat Too Much Popcorn?

But does the fact that the bags have PFOAs and PFOSs in them mean that you'd be ingesting the chemical if you eat the popcorn? Researchers from a report published in a newer October 2019 issue of Environmental Health Perspectives set out to answer this question.

They found that eating microwave popcorn had significant positive associations with the concentration of PFOA and PFOS in the blood. They also made the point that PFOAs and PFOSs can remain in the body for 3.5 and 4.8 years, respectively.

After popcorn manufacturers got wind of the health problems associated with PFOA, many of them took the chemical out of their bags; however, others did not. Researchers from a report that was published in Food Additives and Contaminants in September 2019 tested popcorn bags from seven microwave popcorn brands and found that two of them contained amounts over the acceptable limit, while the others had lower concentrations.

While this is definitely a step in the right direction, the problem is there's no way to tell which ones are safe and which ones aren't. Manufacturers don't list whether or not their popcorn bags contain PFOA on the labels.

Read more: How Healthy is Popcorn?

But it's not just cancer that's the problem. Another report that was published in Occupational and Environmental Medicine in October 2018 connected an ingredient in microwave popcorn butter flavoring, called diacetyl, to lung problems. According to the report's researchers, workers from popcorn manufacturing facilities were presenting with lung obstructions and chronic coughs that eventually got the nickname "popcorn lung."

After some digging, it was determined that diacetyl is a respiratory toxin and chronic exposure can irritate and harm the lungs. The Centers for Disease Control and Prevention reported that when diacetyl is heated, it can cause a vapor that damages the airways and can lead to obliterative bronchiolitis, or narrowing of the lungs' airways that's caused by inflammation.

Of course, the workers in the popcorn manufacturing facilities are exposed to much higher concentrations than you would be from eating a bag of microwave popcorn here and there. And, as of November 2019, there is not evidence connecting eating popcorn to popcorn lung. But the connection is still something that you may want to be aware of.