Brief exposure to coffee roasting chemical when you're sick can seriously damage lungs -

ROCHESTER, N.Y. — For years, we’ve known that a flavoring chemical called diacetyl, found in various foods and drinks, can damage the lungs. However, researchers from the University of Rochester Medical Center reveal that even brief exposure to this chemical, combined with another ailment like the flu, can harm the lungs.

Diacetyl, the compound responsible for the buttery taste of microwave popcorn, was initially linked to lung disease in the early 2000s when microwave popcorn factory workers fell ill. More recently, coffee roasters exposed to high concentrations of diacetyl during the roasting process have experienced similar lung problems. While previous cases involved long-term, high-level exposure, this study aimed to determine if low-level, short-term exposures could have comparable effects.

“Our findings indicate that a single short-term exposure to diacetyl alone doesn’t cause significant lung damage,” explains Dr. Matthew D. McGraw, the study’s lead author, in a university release. “However, when mice are exposed to another common environmental factor, such as the flu, the combination can lead to airway disease similar to what we see with high-dose, long-term exposures to diacetyl.”

During the study, researchers exposed mice to diacetyl for one hour a day over five consecutive days, mirroring the exposure levels of coffee roasters. Subsequently, the mice were infected with influenza A, the virus responsible for seasonal flu in humans. Within two weeks, over half of the mice exposed to diacetyl and the flu died, while those in control groups (exposed to diacetyl alone, the flu alone, or neither) survived. The mice subjected to the combined exposure displayed significant impairment of lung function and airway repair compared to the controls.

Coffee maker pouring fresh cup — Photo by John Schnobrich on Unsplash

To further investigate, researchers reversed the order of exposure. They infected a different group of mice with the flu first, allowed them to recover for nine days, and then exposed them to diacetyl for five days. In both cases, the mice’s lungs struggled to heal fully, indicating that exposure to both the chemical and the virus disrupts normal airway repair.

“Our study highlights the serious impact that seemingly harmless environmental exposures can have on lung function and long-term respiratory health when they occur together,” says Dr. McGraw.

Although further research is required to understand the effects of low-level diacetyl exposure in humans, this study has implications for individuals working with diacetyl, like coffee roasters. Dr. McGraw’s team is investigating how long after a flu infection it is safe for coffee roasters to be exposed to diacetyl, which can guide their return to work protocols. Additionally, the researchers plan to collaborate with local coffee roasters to raise awareness about diacetyl risks, evaluate existing exposure mitigation procedures, and survey workers for lung disease symptoms.

The study is published in the American Journal of Physiology – Lung Cellular and Molecular Physiology.