Concerns about diacetyl and related flavorings have spread from the microwave popcorn industry to new areas, such as coffee processing. The CDC published a report on the health effects of chemicals produced during coffee processing, that stated, "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.". The CDC also reported that exposures to these chemicals at certain levels may result in reduced lung function, severe fixed obstructive lung disease, and an irreversible, and sometimes fatal, lung disease, obliterative bronchiolitis.
After five cases of former workers of a coffee processing facility that roasted, ground, and flavored coffee were identified in 2012, additional studies were undertaken based on worker concerns. In August 2015, the American Journal of Industrial Medicine reported several other cases in the coffee processing industry, leading to the need for evaluation of work places beyond the microwave popcorn and flavoring industries, where concerns about these chemicals first arose. Workers may be exposed to diacetyl and 2,3-pentanedione during several phases of coffee processing, including grinding, roasting, flavoring, and packing. One study measured the highest exposures in the flavoring and grinding of unflavored coffee. Other industries with fermentation and pyrolysis products can also generate diacetyl exposures, such as in the manufacture of beer, wine, and dairy products.
As these relationships illustrate, this is clearly an area where medical and scientific knowledge is evolving. Source material includes numerous points made by government agencies or regulators (such as NIOSH, CDC, OSHA, etc.), and the science at this point is likely incomplete or subject to change. Employers facing issues related to flavoring-type exposures during coffee processing, such as diacetyl and 2,3-pentanedione, need to be aware of, and follow, all applicable regulations for their specific circumstances.