Background

Diacetyl and its substitute, 2,3-pentanedione, are flavoring compounds that are used extensively in the food flavoring and production industries. Occupational exposure to diacetyl has been associated with severe respiratory impairment and obliterative bronchiolitis, a serious lung disease that is irreversible. In this disease, the smallest airways in the lung (the bronchioles) become scarred and constricted, blocking the movement of air. In addition, 2,3-pentanedione is chemically similar and has had similar effects in animal models. The first observation of obliterative bronchiolitis in a food production employee may have occurred in 1985 in a facility where diacetyl was listed among ingredients used in making flavorings for the baking industry [NIOSH 1985Cdc-pdf ].

In August 2000, a health department requested technical assistance from NIOSH in an investigation of obliterative bronchiolitis in former workers of a microwave popcorn plant. The request led to research led by NIOSH. Through these investigations, it was determined that artificial butter flavorings added to the popcorn was responsible for causing the disease. The findings from NIOSH investigations in the microwave popcorn and flavorings manufacturing industries provided a basis for a 2004 NIOSH Alert: Preventing Lung Disease in Workers Who Use or Make Flavorings. In addition to the full Alert in English, a Summary Sheet is available in Spanish. Although much remains unknown regarding the toxicity of flavoring-related chemicals, employers and workers can take steps to address working conditions and work practices that place workers at risk.

In 2012, NIOSH identified obliterative bronchiolitis in a group of workers that used artificial flavorings to produce and package flavored whole-bean and ground roasted coffee. It was determined that diacetyl in the artificial coffee flavorings was responsible for causing these new cases of disease. This led to a series of investigations at coffee roasting and packaging facilities. As part of these ongoing investigations, NIOSH is evaluating diacetly, 2,3-pentanedione, and other chemicals that are naturally produced and released during the coffee roasting process [Duling et al. 2016External ; Daglia et al. 2007External ]. Grinding roasted coffee beans produces a greater surface area for off-gassing (sometimes called degassing) of these compounds.