Workers in microwave popcorn factories have actually developed an extremely rare form of lung cancer from inhaling fumes. If that isn’t enough of a reason to avoid the stuff, here’s another: the lining of the bags contains perfluorooctanoic acid (PFOA), a substance that has been linked to several other forms of cancer and infertility. Plus, so many microwave popcorns are loaded with bad fats and sodium. Homemade air-popped popcorn can actually be a health food, believe it or not, so stick to that for your next movie night.