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.