Hidden Hazards: Occupational Risk of 1,2-Diones in Food & Beverage Manufacturing

By: William H Chapman, Ph.D., Contributor

A recent $58.6 million jury verdict underscores the grave danger posed by inhaling certain food flavoring chemicals—many of which remain undisclosed on safety data sheets. Among the most concerning are 1,2-diones, a class of volatile organic compounds (VOCs) widely used in flavor manufacturing. Diacetyl (2,3-butanedione) and 2,3-pentanedione, known for imparting rich, buttery notes, have been linked to irreversible lung damage, known as bronchiolitis obliterans—often called “popcorn lung.”

Despite existing exposure limits, one of the greatest challenges to protect workers is the frequent lack of transparency from flavor manufacturers. Under current regulations, proprietary ingredient exemptions permit the omission of hazardous compounds like diketones from SDSs when present at concentrations below 1%, leaving environmental health and safety professionals unaware of the hidden risks.

Understanding 1,2-Diones

1,2-diones are characterized by two adjacent carbonyl groups, a structure that makes them highly reactive. Diacetyl and 2,3-pentanedione are the most studied members of this chemical family in occupational health contexts. Both are naturally occurring and widely used in artificial flavorings, particularly those that mimic the flavors of butter, cheese, caramel and many more. Despite their pleasant aroma, these compounds pose a serious risk when inhaled over time, even at low concentrations.

Scientific studies have shown that inhalation of diacetyl and 2,3-pentanedione can cause severe damage to the respiratory epithelium, leading to inflammation, fibrosis and eventually bronchiolitis obliterans. The National Institute for Occupational Safety and Health (NIOSH) has established Recommended Exposure Limits (RELs) for both compounds: 5ppb (parts per billion) for diacetyl and 9.3ppb for 2,3-pentanedione, both as 8-hour, time-weighted averages. However, achieving these levels of protection requires knowledge of their presence, which is not always guaranteed.

The Disclosure Loophole

Under current OSHA Hazard Communication (HazCom) standards, manufacturers are not required to list ingredients present in concentrations below 1%, if they are not classified as carcinogens. This creates a significant loophole for volatile compounds like 1,2-diones, which can still present serious health risks even at trace levels. Flavor manufacturers often invoke proprietary rights to shield their formulations, meaning EHS professionals may not even be aware that monitoring for these compounds is necessary.

This lack of transparency undermines workplace safety. Industrial hygienists rely on SDSs and supplier communication to design effective monitoring programs and implement engineering controls. When diketones are not disclosed, sampling may not be conducted; respirators may not be issued; and workers may be unknowingly exposed to harmful airborne contaminants.

Implications for Worker Safety

There have been many documented cases of workers developing irreversible lung disease after chronic exposure to diacetyl, particularly in microwave popcorn and flavoring production facilities. In one widely publicized case, multiple workers at a Midwestern popcorn plant developed bronchiolitis obliterans, leading to investigations that ultimately connected the illness to diacetyl exposure. More recently, a jury awarded $58.6 million to a former flavoring plant worker who developed severe respiratory disease linked to long-term exposure to diacetyl and 2,3-pentanedione.

These incidents underscore the critical need for proactive industrial hygiene practices. In workplaces where SDSs do not list diketones, but flavoring agents are handled, there is a strong case for precautionary air monitoring. EHS professionals should consider deploying validated sampling methods, such as those offered by an accredited industrial
hygiene laboratory.

Chronic 1,2-dione exposure can lead to an inflammatory response, causing a decrease in the function of the lungs’ smallest passages, the bronchioles. Left: Healthy bronchioles; Right: Inflamed bronchioles, damaged by dione exposure. (photo courtesy of Air by CCSquared)

Diagnosis of popcorn lung (bronchiolitis obliterans) typically involves a combination of pulmonary function testing and radiographic imaging. (Image provided by professional Radiologist Ed Kotlyarov, MD)

Recommendations

To better protect workers in flavor manufacturing and other industries using flavoring agents, several strategies should be implemented:

1. Precautionary Monitoring: Even in the absence of SDS disclosure, workplaces handling flavorings should conduct routine air monitoring for diketones, especially during mixing, heating or aerosol-generating activities.
2. Engineering Controls: Local exhaust ventilation and/or closed-system methods (for example, carbon adsorbers) can significantly reduce airborne concentrations of diacetyl and/or related compounds.
3. Supplier Agreements: Organizations can negotiate with suppliers to disclose hazardous ingredients, regardless of concentration, or use third-party disclosure frameworks.
4. Training and PPE: Educating workers about the risks of diketones and providing appropriate PPE, including respirators where warranted, adds an additional layer of defense.
5. Policy Advocacy: EHS professionals and industry groups can advocate for regulatory updates that close disclosure loopholes for highly hazardous, low-concentration chemicals.

Conclusion

The risk posed by 1,2-diones such as diacetyl and 2,3-pentanedione is real, and recent legal verdicts highlight the financial and human cost of ignoring them. While proprietary ingredient protections are important for industry innovation, they should not come at the expense of worker health and safety.

EHS professionals must adopt a proactive and skeptical approach, assuming the potential for hidden hazards and acting accordingly. Through diligent monitoring, smarter sourcing and persistent advocacy, we can close the information gap and ensure safer workplaces for all. IHW

About the Author:

William H Chapman, Ph.D., is the Founder of Air by CCSquared, a provider of lab-based testing for airborne chemical hazards, supporting EH&S professionals in protecting workplace air quality.