Coffee Workers at Risk for Lung Disease

Posted on by Rachel L. Bailey, DO, MPH; Ryan F. LeBouf, PhD, CIH; and Kristin J. Cummings, MD, MPH


Roasted Coffee Beans

Obliterative bronchiolitis, an irreversible form of lung disease in which the smallest airways in the lung (the bronchioles) become scarred and constricted, blocking the movement of air, was previously identified in flavoring manufacturing workers and microwave popcorn workers who were occupationally exposed to diacetyl (2,3-butanedione) or butter flavorings containing diacetyl. Now, NIOSH research finds that workers at coffee processing facilities may also be at risk.

Diacetyl and 2,3-pentanedione (a diacetyl substitute) are volatile organic compounds known as alpha-diketones. Diacetyl and 2,3-pentanedione are produced commercially by chemical manufacturers as ingredients in flavorings that are added to some food products (e.g., microwave popcorn, bakery mixes, flavored coffee). However, diacetyl and 2,3-pentanedione are also naturally produced when coffee beans are roasted. Grinding roasted coffee beans produces greater surface area for the off-gassing of these and other chemicals. Coffee roasting facilities package newly roasted coffee in bags fitted with one-way valves or in permeable bags to allow for off-gassing. Alternatively, newly roasted coffee is placed in containers and allowed to off-gas, which can contribute to worker exposures.

Physicians at a university medical center diagnosed obliterative bronchiolitis in five individuals who had worked at a coffee processing facility. In 2013, NIOSH and colleagues from the university health system summarized two of the cases of obliterative bronchiolitis in a Morbidity and Mortality Weekly Report (MMWR), published by the Centers for Disease Control and Prevention.[i] In November 2015, NIOSH investigators published an article in the American Journal of Industrial Medicine about a health hazard evaluation at the same facility where these individuals worked.[ii]  NIOSH found elevated levels of butter flavoring chemicals diacetyl and 2,3-pentanedione in the air at the facility and identified three sources: 1) flavoring chemicals added to roasted coffee beans in the flavoring area, 2) grinding and packaging unflavored roasted coffee in a distinct area of the facility, and 3) storing roasted coffee in hoppers to off-gas. Current workers had excess shortness of breath and obstruction on spirometry (meaning air is exhaled from the lungs more slowly than normal), which are both consistent with undiagnosed lung disease. Respiratory symptoms were associated with exposure and not limited to the flavoring area.

NIOSH has ongoing health hazard evaluations at a number of coffee processing facilities and has developed a coffee processing webpage with interim recommendations which may change to reflect additional knowledge as we learn more over the coming year. Current recommendations include air sampling to detect and measure potential concentrations of the chemicals. NIOSH has proposed a recommended exposure limit of 5 parts per billion (ppb) for diacetyl and 9.3 ppb for 2,3-pentanedione (as a time-weighted average (TWA) for up to 8 hours/day during a 40-hour workweek). The NIOSH proposed 15-minute short-term exposure limits (STELs) are 25 ppb for diacetyl and 31 ppb for 2,3-pentanedione.iii In addition to TWA and STEL samples, air sampling during specific tasks, such as roasting, grinding, packaging, opening storage bins or containers with roasted coffee beans, and pouring and adding flavorings, is an important way to identify where exposures may occur and for targeting workplace interventions (e.g., engineering controls, ventilation changes) to reduce contaminant air concentrations. Employees may need to wear appropriate fit-tested respirators until these workplace interventions have been put into place and shown to reduce air concentrations in follow-up air sampling. Additionally, a medical surveillance program that includes health questionnaires and breathing tests (e.g., spirometry) may be indicated to screen for respiratory symptoms or abnormalities in employees.

These cases reinforce the need for evaluating work-related exposures in all industries in which workers are exposed to diacetyl or 2,3-pentanedione. Currently, no specific federal regulations govern workers exposed to diacetyl or its substitutes. NIOSH has drafted a recommended standard for occupational exposure that includes recommended exposure limits (RELs) for diacetyl and 2.3-pentanedione.[iii] One of NIOSH’s crucial recommendations, in addition to limitation of exposure, is regular hazard assessment in industries that use flavorings. Whereas most studies have focused on the microwave popcorn and flavoring industries, this report shows that other industries might benefit from the recommendations. In 2015, NIOSH published a best practices document that describes exposure monitoring and work interventions (e.g., engineering controls, work practices) for occupational exposures to diacetyl and 2,3-pentanedione.iiii

Physicians who find progressive shortness of breath in current or former workers in food production industries should be alert to the possibility that this may be a symptom of obliterative bronchiolitis associated with occupational exposure to flavoring chemicals. If obliterative bronchiolitis is suspected, it is crucial to take immediate steps to control further exposure to prevent further deterioration of lung function.

If exposure to diacetyl and 2,3-pentanedione are a concern in your workplace, contact NIOSH through the Health Hazard Evaluation Program. When situations arise that are not already understood based on prior health hazard evaluations, site visits are often conducted that can include exposure and/or health evaluations to better understand potential hazards.

Rachel L. Bailey, DO, MPH, is a medical officer in the NIOSH Respiratory Health Division.

Ryan F. LeBouf, PhD, CIH, is  a research industrial hygienist in the NIOSH Respiratory Health Division.

Kristin J. Cummings, MD, MPH, is the Chief of the Field Studies Branch within the NIOSH Respiratory Health Division.




[i] MMWR 62(16):304-307. Available at

[ii] AJIM 2015;58(12):1235-1245. Available at;jsessionid=B4787EE549F4C69DEAA7DD161934D413.f03t04.

[iii] National Institute for Occupational Safety and Health (NIOSH). Draft criteria for a recommended standard: occupational exposure to diacetyl and 2,3-pentanedione. Cincinnati, OH: US Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health; 2011. Available at

iiii NIOSH. Best practices: engineering controls, work practices and exposure monitoring for occupational exposures to diacetyl and 2,3-pentanedione. By Dunn KH, McKernan LT, Garcia A. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication 2015-197; 2015. Available at




Posted on by Rachel L. Bailey, DO, MPH; Ryan F. LeBouf, PhD, CIH; and Kristin J. Cummings, MD, MPH

11 comments on “Coffee Workers at Risk for Lung Disease”

Comments listed below are posted by individuals not associated with CDC, unless otherwise stated. These comments do not represent the official views of CDC, and CDC does not guarantee that any information posted by individuals on this site is correct, and disclaims any liability for any loss or damage resulting from reliance on any such information. Read more about our comment policy ».

    John Newton, OSHA IH in Maine office, wrote an article Carbon Monoxide from Coffee Roasting; which was in Applied Occupational and Environmental Hygiene; Vol 17 (9); 600-602; 2002. Employee carboxyhemoglobin level 27.1 at hospital after receiving O2; calculated exposure 2500 ppm; the article has lots of other exposure information for various parts of the process.

    I think these cases reinforce the need for evaluating work-related exposures in industries at coffee processing facilities. How to better understand potential hazards in which workers are exposed to diacetyl?

    We agree. NIOSH is currently responding to requests for health hazard evaluations at other coffee processing facilities and welcomes additional requests. A health hazard evaluation can be requested by an employer, 3 current employees, or a union official here:

    CO issues more on
    Carbon Monoxide Poisoning from Industrial coffee extraction JAMA 2003 290[3]:334
    A fatality CoHB in heart blood 76% at 17hrs after death; and five workers hospitalized storage tank CO levels 10,000 to 100,000ppm

    Thank you for bringing attention to this important issue. In addition to alpha-diketone exposure, coffee processing poses a risk of exposures to other potentially harmful compounds including carbon monoxide. Evaluation of the ventilation system (e.g., local exhaust, general ventilation) and air sampling can help determine if control measures are needed to reduce airborne concentrations of alpha-diketones, carbon monoxide, and other potentially harmful compounds.

    I really appreciate you drawing attention to this crucial matter. Besides the exposure to alpha-diketones, it’s important to be aware that coffee processing also carries the risk of exposure to other harmful substances like carbon monoxide. It would be wise to assess the ventilation system (such as local exhaust and general ventilation) and conduct air sampling.

    Off topic a bit, but I am concerned about inhaling these dangerous chemicals via my ecig. Many of the flavorings in popular ejuices do contain the chemicals mentioned in this and other similar articles. Following, is a partial list of flavor groups which may contain diacetyl and 2,3-pentanedione: Any ejuice manufacturer that advertises such flavor profiles as-
    ■custard- lemon custard, strawberry custard, apple turnovers with custard, etc.
    ■buttery- any dessert flavor involving a buttery crust, any pastry, also- popcorn, cookie dough…
    ■creamy- such as, strawberries + cream, lemon cream, cream sickle, Bavarian cream, and so forth.
    ■ice cream- ice cream sandwich, ice cream sunday, chocolate ice cream, spamoni, etc.
    ■milkshake- as one would expect; chocolate shake, café mocca shake, vanilla bean milk shake…
    ■yogurt- there are many ejuices that are called yogurt with…granola, honey-cream, blueberries and the like.
    ■milk with cereal- every sweet cereal that one can imagine has been turned into an ejuice…with milk.
    ■chocolate- this flavor is used in shakes, with custards, buttery desserts and icecream, to name a few.
    ■cinnamon + cloves- used in many ejuices listed here.
    ■caramel + butter pecan- again, used in dozens of ejuices.
    I was able to quit smoking due to ecigs, like so many others. If we just avoid the questionable flavors, I’m hoping that all of us x-smokers will be improving our health, however- I would like to know if the flavors in question are in fact a danger to all who vape and if so, have we damaged our lungs permanently?
    Thanks in advance for reading (and hopefully) responding! Gratefully, Sage

    Thank you for contacting us with your concerns. NIOSH has studied ecigs and e-juice emissions for a number of years now including a recent laboratory investigation of the emissions and frequencies of diacetyl and 2,3-pentanedione (among other chemicals) identified in the air above e-juices (not vaped). Diacetyl (2,3-butanedione) and 2,3-pentanedione (acetyl propionyl) are volatile organic compounds known as alpha-diketones that can occur naturally and may also be added as ingredients in food flavorings. A debilitating respiratory disease, obliterative bronchiolitis, may be caused by inhalation exposure to diacetyl and 2,3-pentanedione, but this disease has not been identified among ecig users. Our research found that other flavor groups outside the ones you list also contained diacetyl and 2,3-pentanedione.

    The flavors you list below are consistent with the types we tested, and they did contain diacetyl and 2,3-pentanedione in varying amounts. It is difficult to say whether the e-juice you use contains diacetyl and 2,3-pentanedione without testing. As far as permanent lung damage, I would urge you to communicate with your doctor regarding respiratory health and monitoring to make sure your lung function does not decline over time (beyond the usual decline due to aging).

    Feel free to contact me with any questions.

    Ryan LeBouf, PhD, CIH

    I experience severe allergic reaction from exposure to diacetyl and 2,3-pentanedione compounds, such as those produced by microwave popcorn. Regarding the naturally-occurring chemical compounds from coffee production discussed above – I live less than three miles from a major coffee manufacturing plant – could the amount of the compounds released into the atmosphere contribute to the incidence of asthma in the area?

    Thanks for sharing your important research. Thanks, too, for your reply.

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Page last reviewed: July 12, 2019
Page last updated: July 12, 2019