coffee beans on table ready to roast in small coffee shop

What is Diacetyl? The PPE You Should Consider for Coffee Processing

What is diacetyl? Diacetyl is also known as an alpha-diketone, 2,3-butanedione, or by its Chemical Abstracts Service (CAS) number, 431-03-08. That’s the science. Diacetyl is a volatile organic compound most known as a flavoring agent in microwavable buttered popcorn. What you may not realize, is that diacetyl is also produced naturally during coffee processing and in other food processing with distillation, fermentation and pyrolysis: such as in the manufacture of beer, wine and dairy products. Overexposure to diacetyl may lead to respiratory problems, but taking certain measures can help workers be protected.

There is a growing need to understand exposure to diacetyl and 2,3-pentanedione and its effect on coffee processors. As more coffee is consumed, more coffee processing is taking place throughout the U.S. and the rest of the world and this may mean the potential of more diacetyl exposure is also taking place.1

While this is not a hazard you will be talking about around the coffee table, in 2015 the Centers for Disease Control and Prevention (CDC) published a new report on the health effects of chemicals produced during coffee processing.2 The CDC reported, “Roasting coffee beans naturally produces diacetyl and 2,3-pentanedione. Volatile organic compounds, including alpha-diketones (e.g, diacetyl and 2,3-pentanedione), can be released during grinding of coffee.”

Don’t worry. We aren’t here to tell you that you need to give up your coffee drinking. But, there are respiratory hazards coffee roasters and processing facilities should consider. While considered safe to eat, the CDC reports that respiratory exposure to these chemicals at certain levels may result in a variety of negative health effects for workers.3

While the hazards of artificial flavorings in microwave popcorn and flavoring manufacture have been known for some time—birthing the term “popcorn lung,”— the impact of naturally occurring versions of these chemicals in coffee processing is now receiving more attention. For instance, USA Today in September 2017 reported that the CDC found more evidence of respiratory problems in more than a third of the 16 workers screened at the Just Coffee co-op plant in Wisconsin. These workers had abnormal breathing tests where no artificial flavoring agents were being added during the processing of coffee.4 But more research is needed because the full effect is still not known. NIOSH has completed 11 health hazard evaluations of coffee processing facilities and is continuing to aggregate data. ( accessed 3-18-2019).

Coffee processors should consider the possibility of flavoring chemical-related lung disease in workers who have been overexposed to diacetyl or similar flavoring chemicals (such as 2,3-pentanedione, a common substitute for diacetyl, 2,3-hexanedione and 2,3-heptanedione) and have respiratory symptoms. This is especially noteworthy since diacetyl has also been detected in the air while coffee is being processed without any flavorings being added during production, which means that airborne diacetyl can arise from just the act of processing natural coffee beans.

NIOSH has reported that the health effects of diacetyl exposure may include:
• Dry persistent cough
• Shortness of breath on exertion
• Wheezing
• Reduced, rapid or permanent reduction in lung function
• Occupational asthma
• Eye, nose and throat irritation
• Skin rashes

Workers such as those that work in coffee processing facilities may be overexposed to diacetyl and 2,3-pentanedione during several phases of coffee processing including grinding, roasting, flavoring and packing. In fact, one study measured the highest exposures in the flavoring and grinding of unflavored coffee.5

NIOSH Recommendations

In coffee processing facilities, NIOSH recommends air sampling for diacetyl and 2,3-pentanedione to help determine if control measures are needed to reduce airborne concentrations of these alpha-diketones. Area and personal air sampling as well as air sampling during specific tasks such as roasting, grinding, or pouring and adding flavorings can help characterize exposures by area, job, and task. Detailed best practice sampling techniques are described further in the NIOSH 2016-111 publication.

While no OSHA Permissible Exposure Limit currently exists, the American Conference of Governmental Industrial Hygienists (ACGIH) has established a Threshold Limit Value® (TLV) for diacetyl of 10 parts per billion for an 8-hour TWA. Additionally, NIOSH has published its proposed recommended exposure limits (RELs) in workplace air of 5 ppb for an 8h TWA. [See NIOSH 2016-111 publication Table 1]. Some studies have shown that industrial coffee processing may produce levels of diacetyl and 2,3-Pentanedione in excess of both these ACGIH TLV and NIOSH RELs.

NIOSH recommendations for controlling exposure and protecting workers include engineering controls and work practices (see the NIOSH 2016-111 publication for full best practice recommendations).

Engineering Controls

Per NIOSH, this includes providing local ventilation and properly designed room dilution ventilation systems, maintaining negative pressure in and isolating handling areas. Substitution may be challenging, as some exposures are naturally occurring from just the act of processing coffee as mentioned above. The health effects of any flavoring substitutes would need further evaluation.

Work Practices

To minimize exposures per the NIOSH 2016-111 publication, NIOSH recommended steps that can be taken may include covering containers, working towards reducing spills, using closed processing (ie. avoiding open pouring), maintaining good housekeeping, providing proper work clothing, and training. Housekeeping techniques may also include using HEPA-filtered vacuums and wet cleanup techniques to remove spills. Companies should require workers to wash hands after exposures.

Hazard Communications

Per the Haz Comm standard, workers should have access to appropriate Safety Data Sheets (SDS), make sure hazards are labeled, and training has been conducted. Per the NIOSH 2016-111 publication, NIOSH further recommends that workers should be trained to immediately report eye/skin problems, cough, shortness of breath, or wheezing.

Medical Monitoring

NIOSH recommends that medical monitoring should include both questionnaires and breathing tests (eg. spirometry) before the first exposure, and on a regular basis thereafter, to all workers at risk of hazardous exposure of diacetyl, 2,3-pentanedione, or related flavorings.6 Since diacetyl occurs naturally and from being used in flavorings, the need for initial testing and continuous monitoring is even more important. Refer workers for evaluation by a physician if they have abnormal test results, an accelerated drop in test results over time, or persistent symptoms.

PPE Considerations for Coffee Roasting and Diacetyl Exposure

If air monitoring and exposure assessment indicate exposures above occupational exposure limits, employees may need to wear appropriate NIOSH approved and fit-tested respirators until workplace interventions can be put into place. Additionally, eye, face and skin protection should be considered based on assessment results.*


Respiratory protection should be selected based on the results of air monitoring and in compliance with the assigned protection factors (APFs) outlined in the OSHA Respiratory Protection Standard 29 CFR 1910.134. NIOSH suggests a full face piece respirator* with a combination organic vapor cartridge/P100 filter or a powered air purifying respirator (PAPR) with an organic vapor cartridge/HE filter. (Source: Per OSHA regulations, a site-specific cartridge change-out schedule must be developed; noticeable odor cannot be relied upon. Supplied air respirators may also be considered to control inhalation exposures.

NIOSH-approved respirators must be used in accordance with the NIOSH cautions and limitations specified on the NIOSH approval label, follow all relevant user instructions, and comply with OSHA’s respiratory protection regulations laid out in 29 CFR 1910.134. OSHA requires employers to implement a written respiratory protection program meeting all the requirements of the standard when respirators are used. There must be written worksite-specific procedures for respirator selection, medical evaluations, use of respirators, maintenance and care, measures to assures adequate air quality, training and fit testing, program evaluations and a program administrator who oversees and maintains this program. To learn more about how to implement and maintain this type of program, we encourage you to visit our Center for Respiratory Protection.

The respirator manufacturer or a health and safety professional should be consulted if there is any question regarding respirator selection and use. Users must understand the respirator capabilities, as well as limitations, and carefully follow the respirator manufacturer’s User Instructions in order to receive the assigned level of protection. Misuse of a respirator may result in sickness or death. Always consult User Instructions, seek out technical assistance when considering what respiratory PPE to buy, and follow local laws and regulations.

Eye Protection

NIOSH recommends that eyes be protected from contact with diacetyl or 2,3-pentanedione, or related flavorings. NIOSH recommends that employers should consider either a full face piece respirator, hood, or helmet. If not required to wear a respirator with eye protection, eye and face protection meeting ANSI Z87.1-2010, such as a face shield and or chemical splash goggles meeting the D3 Splash and D4 Dust rating are suggested. (, p 206-207)

Skin Protection

Skin contact must be avoided to help reduce the risk of dermal exposure. NIOSH suggests protective coveralls, lab coats, aprons, and gloves should be considered. In addition, chemical-resistant gloves should be worn to protect the hands (e.g., butyl, nitrile). Refer to coverall and glove manufacturers recommendations for specific products. (, p 206-207)

While this concern for workers in the coffee processing industry started to brew back in 2012, many workers may be just learning of potential health effects of naturally occurring diacetyl and 2,3-pentanedione. All coffee processing facilities should complete air monitoring for diacetyl and 2,3-pentanedione, including flavoring areas, as well as, any part of the production facility where unflavored coffee is roasted, ground or packaged. Even non-production areas may be affected.

Quick Takeaways

Based on this exposure assessment, the company should implement the required controls to help reduce exposures which may include:

  • Appropriate engineering controls
  • Changes to administrative controls and work practices
  • Use of proper personal protective equipment to help reduce exposures while other controls are implemented

To learn more about how we can help you protect your workers from diacetyl exposure, please do not hesitate to contact us today.

*Full face piece must be quantitatively fit tested to receive an APF of 50.

2 “Flavorings Related Lung Disease- Coffee Processing Facilities” February 1, 2016.
5 Bailey, Cox-Ganser, Duling, LeBouf, Marting, Bledsoe, Green, and Kreiss. American Journal of Industrial Medicine. “Respiratory Morbitdity in a Coffee Processing Workplace With Sentinel Obliterative Bronchiolitis Cases”
6DHHS (NIOSH) Publication Number 2004–110. NIOSH Alert: Preventing Lung Disease in Workers Who Use or Make Flavorings.

*These PPE products are suggested, not recommended. Please select PPE that is appropriate given your situation.