How Safe Is Your Kitchen?
Reality: A report from the National Institute for Occupational Safety and Health linked diacetyl, a chemical used in butter flavorings in microwave popcorn, to respiratory illnesses found in factory workers who mixed them. Researchers suspected that when inhaled over extended periods, the butter-flavoring vapors become hazardous. According to the EPA, however, the flavorings pose no threat to consumers.
Bottom line: It’s probably fine to nuke popcorn, but if you need more certainty, pop your corn in a covered pot on the stove or with an air popper.