Popcorn is one of the world's most popular confections, frequently enjoyed in ballparks, movie theaters and at home. Popcorn makers sell three billion bags of microwave popcorn every year [source: Seattle Post-Intelligencer]. However, some doctors and consumer groups have been concerned that a chemical used to give microwave popcorn its tasty butter flavor may pose a serious health hazard.

The chemical is called diacetyl, and it's used in the production of microwave popcorn, but it has also likely led to scores of factory workers developing a severe lung condition. Diacetyl occurs naturally in some foods, including butter and many dairy products, fruits, wine and beer. It's reportedly used in "thousands" of food products to add or increase butter flavoring [source: Seattle Post-Intelligencer].

Hundreds of factory workers have developed a condition called "popcorn lung," also known by the medical name bronchiolitis obliterans. The condition is caused by inhalation of diacetyl fumes, which cause scarring in the lungs. Sufferers of popcorn lung have difficulty exhaling, and when severe, the condition can be fatal. In many cases of severe bronchiolitis obliterans, only a lung transplant will save a patient's life. Some former popcorn factory workers died while waiting for transplants.

In September 2007, the murmurs of concern surrounding microwave popcorn became louder as some began to wonder whether consumers were in danger as well. The publicity, caused in part by a suspected case of popcorn lung in a consumer, led four major popcorn makers to announce that they planned to drop diacetyl. The companies -- Weaver Popcorn Co., ConAgra Foods Inc., American Popcorn Company and General Mills Inc. -- had, as of early September, phased out use of the chemical or claimed they would within a year. The companies differed in their reasons for dropping the chemical, but some cited consumer concerns or issues of worker health.

­In 2003 and 2004, federal health officials looked into the cases of several hundred sick workers at popcorn manufacturing plants. Those workers were diagnosed with popcorn lung, likely caused by inhalation of diacetyl fumes. The owner of a popcorn company in Montana died from complications believed to be related to ingredients in popcorn flavoring [source: Seattle Post-Intelligencer]. It's not only hundreds of popcorn factory workers -- workers in candy and potato chip factories have gotten sick as well, as have at least 20 more workers who manufactured products with diacetyl [source: Seattle Post-Intelligencer]. More than $20 million in damages have been paid out as a result of lawsuits filed by factory workers harmed by diacetyl, and as previously mentioned, some workers have died [source: Seattle Post-Intelligencer].

The sick workers in popcorn and candy factories were exposed to large quantities of diacetyl fumes on a daily basis, but could consumers be at risk? On the next page, we'll look at what's believed to be the first case of a popcorn lover suffering from bronchiolitis obliterans.