May 2, 2008 - Microwave Popcorn Tied to Lung Disease

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An unusually high incidence of bronchiolitis obliterans among workers at microwave popcorn factories is thought to be the result of exposure to diacetyl, which gives products a buttery flavor. The chemical, which is produced through the fermentation process, is also found in margarines, as well as some beers and wines. It is believed to be carcinogenic when inhaled over a long period of time.

Bronchiolitis obliterans is commonly called “Popcorn Workers Lung” because of the high incidence amongst worker in factories that make microwave popcorn. The disease causes the scarring and eventual destruction of the small airways in the lungs and results in chronic inflammation of the large airways. There is no known cure, other than lung transplant. The disease was thought to be limited to people working in the flavorings industry. But last July, the FDA was notified of a patient who had contracted the disease after eating several bags of microwave popcorn on a daily basis for 15 years. According to the Centers for Disease Control (CDC), this is the first report of Popcorn Workers Lung in a consumer.  That victim has since filed a lawsuit against the company that produced the microwave popcorn he favored.

Diacetyl is easily vaporized at temperatures used in microwave popcorn production, which results in high concentrations in the workplace. Research by the National Institute for Occupational Safety and Health (NIOSH) examined the acute toxicity of inhaled diacetyl in mice, and compared different exposure patterns. It was one of the very first studies to evaluate the respiratory toxicity of the chemical flavoring agent at levels relevant to human health. The researchers found that diacetyl vapors can indeed be damaging to the lungs. The researchers made laboratory mice inhale diacetyl vapors over a three-month period, and found that the mice developed lymphocytic bronchioloitis, a precursor to bronchiolitis obliterans, though none actually developed Popcorn Workers Lung.

In 2007, several makers of microwave popcorn, including ConAgra, General Mills and American Popcorn Company, took steps to remove diacetyl from their products.  There has also been a movement to convince federal regulators to police the use of diacetyl in the workplace, but those efforts have had mixed results.  The Occupational Safety and Health Administration (OSHA), which sets limits on the levels of dangerous substances to which workers may be subjected, said in 2000 that it had no standards for exposure to diacetyl, and that it was not considered to be a problem, as the FDA had determined diacetyl to be “safe.” The FDA, on the other hand, maintains that it has no jurisdiction to evaluate hazards posed by breathing vapors from food additives. OSHA is expected to begin investigating next month, and will ultimately set limits for workplace exposure.