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The Coffee Roaster Guide to Diacetyl

NCA Guide to Diacetyl and Workplace Safety

Diacetyl (and the related compound 2,3-pentanedione) is a naturally occurring chemical that is common in many foods, from butter to beer. In terms of coffee, it's naturally produced in the roasting process and may be found in some flavorings. 

While it poses no risk for consumers, extreme levels of airborne diacetyl may be linked to a rare and serious lung disease known as bronchiolitis obliterans (BO), or "popcorn lung" - so called for the chemical's association to that aromatic buttery flavoring. 

To better understand this complicated issue, the National Coffee Association (NCA) has been working with scientists from across the industry to assess safe and accurate occupational exposure levels (OELs) for coffee facilities. 

The NCA has curated the following resources to help coffee roasters understand what this means for them - and to keep their employees safe.

Coffee Industry Resources

NCA Member login may be required. Check to see if your organization is a member. For further assistance, please contact us.


NCA Diacetyl FAQ

☕⭐ NCA Member exclusive 

All you need to know (and more) about diacetyl, plus resources for coffee companies and roasters.

Latest OEL Research

The latest peer-reviewed study on safe airborne diacetyl levels, published by the Journal of Applied Toxicology.


OEL Development

Understanding occupational exposure limits (OELs) development - and why the latest research matters. 

Testing Protocol Guidance

☕⭐ NCA Member exclusive 

How coffee production facilities may implement a sampling and testing program, and what to do with the results.

About Diacetyl & Coffee Roasting

Diacetyl is a substance found in many surprising places – like human breath, cigarette smoke, and many common foods. In terms of coffee, it is produced naturally in the roasting process. 

While diacetyl occurs naturally during the production of certain foods and beverages, it was also historically added to flavorings for its buttery taste. Today, added diacetyl has largely been removed from flavorings - often substituted by compounds like  2,3-pentanedione (which also share similar concerns for occupational exposure limits). However, naturally-occurring diacetyl may still be present.

Similar to many things we may eat, drink, touch, or inhale, there are typically established amounts, concentrations, or levels of exposure that are considered safe for human health. Foods and beverages containing diacetyl are not unhealthy as a result. However, concerns have been raised with respect to workers who may be exposed on a consistent and concentrated basis to diacetyl vapors. 

Scientists are not unanimously sure what level of exposure is appropriate in a workplace setting.  Despite varying opinions about this potential hazard, there are a number of exposure guidelines and recommended precautions that have been suggested by various authorities (described in the NCA members-exclusive FAQ below).

Log in to access additional resources, including a comprehensive overview of OEL development, FAQs, sampling guidance, and groundbreaking research.  

Coffee Industry Resources

NCA Member login required. Check to see if your organization is a member. For further assistance, please contact us.

Industry Feedback Appreciated!

The NCA invites members of the industry to let us know what we should address in upcoming diacetyl training and education, and other areas of interest. Your feedback will help us develop future NCA content and resources.

Specific questions and constructive comments are also welcome. Please submit those here.

Disclaimer: We invite you to review these resources to ensure that your workplace is as safe as possible – and compliant with all applicable laws and regulations. NCA’s Guide to Workplace Safety, and the resources provided within The Guide are not meant to be a substitute for on site assessment, evaluation, hazard control, and training, which is the responsibility of coffee organizations, which should consult with qualified industrial hygiene professionals to implement workplace safety programs.




NCA Diacetyl FAQ


OEL Development


Testing Protocol Guidance