Coffee roasting

A One-Two Punch: Low levels of coffee-roasting chemicals and mild flu can damage lungs

We’ve known for two decades that chronic exposure to high levels of a flavoring chemical called diacetyl, found in many foods and drinks, can cause lung damage. Now, a study from the University of Rochester Medical Center suggests that even short-term exposures to this chemical aroma can damage mice’s lungs when combined with a second insult, such as the flu.

Diacetyl, which gives microwave popcorn its buttery flavor, was first linked to flavor-related lung disease in the early 2000s, when a group of former factory workers microwave popcorn contracted the disease. More recently, a similar lung disease has been observed in coffee roasters who inhale high concentrations of diacetyl, which is a natural byproduct of the coffee roasting process.

While these workers inhaled high levels of diacetyl over long periods of time, the URMC study published in the American Journal of Physiology – Cellular and Molecular Physiology of the Lung aimed to test whether short-term, low-level exposures to the same chemical could produce a similar effect.

“We found that a single exposure to diacetyl for short periods did not result in much lung damage,” said study lead author Matthew D. McGraw, MD, assistant professor of pediatric pulmonology at the ‘URMC. “But when mice are exposed to another common environmental exposure, such as influenza, the double hit can cause respiratory tract disease similar to what we see with high-dose, long-term exposures to diacetyl.”

In the study, which was supported by a pilot grant from URMC’s Center for Environmental Health Sciences and a career development award from UR’s Institute of Clinical and Translational Sciences, mice were exposed to diacetyl for one hour a day for five consecutive days at levels similar to what coffee roasters encounter on the job. The mice were then exposed to influenza A, which usually causes seasonal flu in humans.

Within two weeks of exposure, more than half of the mice that received this double shot died, while all mice in the control groups (exposed to diacetyl alone, influenza alone, or none) survived. The lungs of mice exposed to the “two shots” showed significantly impaired lung function and airway repair compared to controls.

The researchers then changed the order of exposure, first infecting another 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 the flu, their lungs were unable to fully heal, again suggesting that exposure to both chemicals and viruses results in abnormal airway repair.

“Our study shows that common environmental exposures that seem harmless on their own can have very serious impacts on lung function and long-term respiratory health when combined,” McGraw said.

Although more research is needed to understand the impacts of low levels of diacetyl on humans, this study may have implications for people exposed to diacetyl at work, such as coffee roasters. Currently, McGraw’s team is conducting a mouse study to see how soon after an influenza infection it is safe to be exposed to diacetyl, which could help inform when coffee roasters can safely return to work. after having the flu.

In the near future, the team also plans to work with coffee roasters in our region to educate the public about the risks of diacetyl exposure, assess existing exposure mitigation procedures, and investigate disease symptoms. lungs in workers.

Other authors of the American Journal of Physiology – Cellular and Molecular Physiology of the Lung study include Michael A. O’Reilly, Ph.D., professor of pediatrics; B. Paige Lawrence, Ph.D., president and professor of environmental medicine; Andrew M. Dylag, MD, associate professor of pediatrics; Min Yee, a technical associate at O’Reilly Lab; and So-Young Kim, MS, technician at the McGraw lab.


This project was supported by a pilot grant from the Center for Environmental Health Sciences at URMC under National Institute of Environmental Health Sciences grant number P30 ES001247 and University of Rochester CTSA award number KL2 TR001999 from the National Center for Advancing Translational Sciences.