Microwave popcorn
Popcorn is quite harmless; it’s actually healthy when done right — whole grains right there, corn kernels, and nothing more, but microwave popcorn poses some threats. Popcorn bags are lined with something called PFOA, a possible carcinogen liked to pancreas, liver, bladder, and kidney cancer.
There’s some debate around this one, but you don’t want to risk it.
