Coffee Roasting Chemical and Flue Combo Seriously Damage Lungs

Since the 1990s, scientists have known that chronic exposure to high levels of the flavoring chemical diacetyl, which is present in many foods and beverages, can cause lung damage.

Researchers first connected diacetyl, which gives microwave popcorn its buttery flavor, to flavorings-related lung disease in the early 2000s, when a group of former microwave-popcorn factory workers developed the disease. Recently, coffee roasters who inhale high concentrations of diacetyl, a natural byproduct of the coffee roasting process, have been diagnosed with a similar lung disease.

The new study, published in the American Journal of Physiology—Lung Cellular and Molecular Physiology, aimed to determine whether low-level, short-term exposures to the same chemical could have a comparable effect.

The study’s lead author, assistant professor of pediatric pulmonology at the University of Rochester Medical Center, Matthew D. McGraw, found that a single exposure to diacetyl for short periods of time did not significantly damage the lungs. “However, when mice are also exposed to a common environmental exposure, such as influenza, the double whammy can cause airway disease similar to that observed with high-dose, long-term diacetyl exposures.”

In the study, mice were exposed to diacetyl for one hour per day for five consecutive days at levels comparable to those experienced by coffee roasters. The researchers then exposed the mice to influenza A, the virus that causes seasonal influenza in humans.

More than half of the mice exposed to this combination died within two weeks, whereas all of the mice in the control groups (exposed to diacetyl alone, influenza alone, or neither) survived. Lung function and airway repair were significantly impaired in mice exposed to “two-hits” compared to controls.

The researchers then reversed the exposure order, infecting a second group of mice with influenza, allowing them to recover for nine days, and then exposing them to diacetyl for five days. Whether the mice were exposed to diacetyl before or after influenza, their lungs were unable to fully recover, indicating that exposure to both the chemical and the virus results in abnormal airway repair.

McGraw explains, “Our study demonstrates that common environmental exposures that appear harmless on their own can have severe effects on lung function and long-term respiratory health when combined.”

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