There's no better snack for movie night at home than a bucket of buttery popcorn. But you may think twice about the microwave stuff after we tell you about and ingredient it contains, diacetyl, and the trouble it has caused.

Diacetyl was first synthesized more than 80 years ago and can now be found in about 6,000 food products. It’s used as a preservative in unsalted butter to lengthen shelf life, but higher amounts are added to butter-flavored products like microwave popcorn, cooking oils and sprays and margarine.

Low levels of this additive are safe, however diacetyl gained notoriety around 2005 to 2007 when employees working in American factories became very ill after long-term exposure. Studies have also found that professional chefs who stand over hot grills or skillets for hours using large amounts of butter substitutes are also at risk. Reported side effects included persistent dry cough and wheezing, shortness of breath. Several employees of food companies using the ingredient were diagnosed with obstructive lung disease, which is potentially fatal. After this fiasco, most major food companies switched to safer ingredients.

Bottom Line: To play it safe, you're better off making your own popcorn. Leave the microwave stuff for a once-in-a-while snack.