By Rachel L. Bailey, DO, MPH; Ryan F. LeBouf, PhD, CIH; and Kristin J. Cummings, MD, MPH

Obliterative bronchiolitis, an irreversible form of lung disease in which the smallest airways in the lung (the bronchioles) become scarred and constricted, blocking the movement of air, was previously identified in flavoring manufacturing workers and microwave popcorn workers who were occupationally exposed to diacetyl (2,3-butanedione) or butter flavorings containing diacetyl. Now, NIOSH research finds that workers at coffee processing facilities may also be at risk.

Diacetyl and 2,3-pentanedione (a diacetyl substitute) are volatile organic compounds known as alpha-diketones.Diacetyl and 2,3-pentanedione are produced commercially by chemical manufacturers as ingredients in flavorings that are added to some food products (e.g., microwave popcorn, bakery mixes, flavored coffee). However, diacetyl and 2,3-pentanedione are also naturally produced when coffee beans are roasted. Grinding roasted coffee beans produces greater surface area for the off-gassing of these and other chemicals. Coffee roasting facilities package newly roasted coffee in bags fitted with one-way valves or in permeable bags to allow for off-gassing. Alternatively, newly roasted coffee is placed in containers and allowed to off-gas, which can contribute to worker exposures.

Physicians at a university medical center diagnosed obliterative bronchiolitis in five individuals who had worked at a coffee processing facility. In 2013, NIOSH and colleagues from the university health system summarized two of the cases of obliterative bronchiolitis in a Morbidity and Mortality Weekly Report (MMWR), published by the Centers for Disease Control and Prevention.[i] In November 2015, NIOSH investigators published an article in the American Journal of Industrial Medicine about a health hazard evaluation at the same facility where these individuals worked.[ii]  NIOSH found elevated levels of butter flavoring chemicals diacetyl and 2,3-pentanedione in the air at the facility and identified three sources:

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