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: 1) flavoring chemicals added to roasted coffee beans in the flavoring area, 2) grinding and packaging unflavored roasted coffee in a distinct area of the facility, and 3) storing roasted coffee in hoppers to off-gas.
Current workers had excess shortness of breath and obstruction on spirometry (meaning air is exhaled from the lungs more slowly than normal), which are both consistent with undiagnosed lung disease.
Respiratory symptoms were associated with exposure and not limited to the flavoring area.
NIOSH has ongoing health hazard evaluations at a number of coffee processing facilities and has developed a coffee processing webpage with interim recommendations which may change to reflect additional knowledge as we learn more over the coming year. Current recommendations include air sampling to detect and measure potential concentrations of the chemicals. NIOSH has proposed a recommended exposure limit of 5 parts per billion (ppb) for diacetyl and 9.3 ppb for 2,3-pentanedione (as a time-weighted average (TWA) for up to 8 hours/day during a 40-hour workweek).
The NIOSH proposed 15-minute short-term exposure limits (STELs) are 25 ppb for diacetyl and 31 ppb for 2,3-pentanedione.iii In addition to TWA and STEL samples, air sampling during specific tasks, such as roasting, grinding, packaging, opening storage bins or containers with roasted coffee beans, and pouring and adding flavorings, is an important way to identify where exposures may occur and for targeting workplace interventions (e.g., engineering controls, ventilation changes) to reduce contaminant air concentrations.
Employees may need to wear appropriate fit-tested respirators until these workplace interventions have been put into place and shown to reduce air concentrations in follow-up air sampling. Additionally, a medical surveillance program that includes health questionnaires and breathing tests (e.g., spirometry) may be indicated to screen for respiratory symptoms or abnormalities in employees.
These cases reinforce the need for evaluating work-related exposures in all industries in which workers are exposed to diacetyl or 2,3-pentanedione. Currently, no specific federal regulations govern workers exposed to diacetyl or its substitutes. NIOSH has drafted a recommended standard for occupational exposure that includes recommended exposure limits (RELs) for diacetyl and 2.3-pentanedione.[iii]
One of NIOSH’s crucial recommendations, in addition to limitation of exposure, is regular hazard assessment in industries that use flavorings. Whereas most studies have focused on the microwave popcorn and flavoring industries, this report shows that other industries might benefit from the recommendations. In 2015, NIOSH published a best practices document that describes exposure monitoring and work interventions (e.g., engineering controls, work practices) for occupational exposures to diacetyl and 2,3-pentanedione.iiii
Physicians who find progressive shortness of breath in current or former workers in food production industries should be alert to the possibility that this may be a symptom of obliterative bronchiolitis associated with occupational exposure to flavoring chemicals. If obliterative bronchiolitis is suspected, it is crucial to take immediate steps to control further exposure to prevent further deterioration of lung function.
If exposure to diacetyl and 2,3-pentanedione are a concern in your workplace, contact NIOSH through the Health Hazard Evaluation Program. When situations arise that are not already understood based on prior health hazard evaluations, site visits are often conducted that can include exposure and/or health evaluations to better understand potential hazards.