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Diacetyl Coffee Vapors – Are Coffee Industry Workers Exposed to Diacetyl?


diacetyl coffee vaporsThe federal Center for Disease Control and Prevention (CDC) recently released evidence indicating that coffee industry workers could be at risk of dangerous diacetyl exposure because of diacetyl coffee vapors.

Following a probe by the Milwaukee Journal Sentinel that exposed how a naturally occurring chemical actually endangers the health of coffee workers, federal investigators have been conducting tests over the past year at approximately one dozen facilities across the U.S.

A recent report issued by the CDC details the agency’s findings from a study of workers at a mid-sized coffee roastery. The study found that the roastery workers suffered from wheezing in their chests at four times the expected rate of a comparable demographic of the U.S. population.

The study was conducted at Just Coffee Cooperative of Madison, Wisconsin.  Of the 16 workers screened for the study, more than a third showed upper-respiratory symptoms with a work-related pattern in many employees. The report went on to say that the workers affected had “four-fold excess of wheeze and abnormalities in lung function” as compared to a similar demographic group. Beyond wheezing, Just Coffee Cooperative workers reported experiencing mucous membrane symptoms, which is likely a reaction to coffee dust exposure.

This is the first report issued of a bureaucratic agency’s medical analysis of workers in a coffee production facility that does not add flavors to its coffee.

All previous studies have been conducted at production facilities that use flavors additives. These studies have found that workers were exposed to the chemical compound diacetyl, a synthetic compound used to create dairy flavoring in coffee. While the FDA approved diacetyl’s use for ingestion in minimal amounts as safe, inhalation of the vaporized form of the compound is known to cause serious lung disease – most commonly, popcorn lung.

Until 2015, it was unknown that natural diacetyl vapors are created when roasting and grinding coffee. When coffee beans are roasted, two chemicals, diacetyl and 2,3-pentanedione, form and are released into the air in greater concentrations when the beans are ground. Levels have also been found to build when the beans are held in storage bins. The coffee bean fumes, while determined not to be dangerous if ingested in small amounts, have been found to be deadly when inhaled.

This discovery prompted the National Institute of Safety and Health (NISH) – a branch of the CDC – to issue a recommendation that, on a daily basis, workers not be exposed to more than 5 parts per billion of either synthetic or naturally occurring diacetyl coffee vapors for fear of worker’s developing lung disease. Those familiar with diacetyl and 2,3-pentanedione believe that workers’ exposures to short amounts of high levels of these chemicals are also of concern, and caution workers to avoid sticking their heads in or hovering over the bins in which coffee beans are stored, as diacetyl concentrations found there have reached as high as 7,000 parts per billion.

The CDC’s recent follow-up study found that 10 of 49 air samples collected from Just Coffee Cooperative worker’s personal breathing zones exceeded the recommended 5 parts per billion naturally occurring diacetyl level. Worker’s tasked with weighing and packaging coffee were exposed to the highest levels of diacetyl.

Following the study, the CDC made recommendations that Just Coffee Cooperative takes extra precautionary measures to minimize workers’ exposure to diacetyl, including vacuuming rather than sweeping, providing masts and respirators to workers for certain jobs, improving the facilities ventilation system, and continually running the facility’s overhead exhaust fan.

The CDC report included a statement warning for all coffee production workers involved with roasting, opening bins and scooping bean, grinding weighing and packaging the product. Normal coffee consumers are not at risk, according to the report.

“Recognizing the dangerous conditions of these facilities is a good first step. Now the CDC needs to create stricter regulations on the coffee production industry to ensure that the work environment is safe,” said Jake Plattenberger, head of TorHoerman Law’s diacetyl litigation team.

The report urges the coffee industry to implement a medical program to monitor employees who could possibly develop lung disease from diacetyl coffee vapors. Many workers with obliterative bronchiolitis have no idea that they have it or that they got it from their workplace, likely because their symptoms do not improve when they go home or over the weekend. Regular exposure to diacetyl causes the bronchioles to be injured, scarred, constricted, and smaller in size. Some workers have developed such severe, disabling lung disease that they have been placed on lung transplant waiting lists.

The CDC is currently completing research at 18 other coffee facilities around the U.S. If the data correlates to the CDC’s recent report, the finding from this research could lead to increased safety standards for coffee production workers.

+ - References

LeBouf, Ryan F, et al. “Evaluation of Exposures and Respiratory Health at a Coffee Roasting and Packaging Facility.” DocumentCloud, Health Hazard Evaluation Program, Aug. 2017,

Rutledge, Raquel. “CDC Warns Coffee Workers of Hazardous Chemicals.” WATCHDOG REPORTS|GASPING FOR ACTION | A JOURNAL SENTINEL WATCHDOG UPDATE, Milwaukee Wisconsin Journal Sentinel, 2 Oct. 2015,

Rutledge, Raquel. “Coffee-Bean Fumes Called Hazardous to Workers' Health.” The Seattle Times, The Seattle Times Company, 7 Apr. 2016,

Sara, Al-Ghanem, et al. “Bronchiolitis Obliterans Organizing Pneumonia: Pathogenesis, Clinical Features, Imaging, and Therapy Review.” Annals of Thoracic Medicine, Medknow Publications, 2008,

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