For over a decade, the National Institute for Occupational Safety and Health (NIOSH) has paid close attention to the food flavoring industry and workplaces in which natural and artificial flavorings containing diacetyl and other flavoring chemicals are used. The use of diacetyl-containing butter flavoring in the process for the manufacture of microwave popcorn was among the first to come under fire by NIOSH and in civil litigation by plant workers. The incorporation of diacetyl-containing flavorings has been scrutinized in other food products, such as candy and bakery products, and most recently, scientists have identified the presence of diacetyl in the flavoring substances used in flavored e-cigarettes. See recently published “Diacetyl Update: What’s in Your Product?”

NIOSH is now looking closely at potential respiratory hazards posed by exposure to diacetyl at coffee processing facilities. The difference in the coffee processing scenario is the scrutiny extends beyond the diacetyl-containing flavorings that are sometimes added to coffee. Diacetyl and 2,3-pentanedione (a chemical sometimes used as a diacetyl substitute) are naturally produced when coffee beans are roasted. The grinding of the beans has the potential for producing greater surface area for the off-gassing of the chemicals. Different processes used to allow for off-gassing can contribute to worker exposures.

Obliterative bronchiolitis, a rare and irreversible form of fixed obstructive lung disease, and the disease identified in the microwave popcorn workers, was identified in five people who had worked at a coffee processing facility. A subsequent Health Hazard Evaluation was performed at the facility, and in November, 2015 NIOSH researchers published an article describing their findings in the American Journal of Industrial Medicine. NIOSH identified three sources of elevated diacetyl and 2,3-pentanedione in the plant: 1) flavoring chemicals added to flavor coffee; 2) grinding and packaging of unflavored roasted coffee; and 3) storage of roasted coffee in hoppers to off-gas.

NIOSH continues to examine worker exposure to diacetyl in coffee processing workplaces and has ongoing Health Hazard Evaluations in a number of plants. At present NIOSH has made the following recommendations:

  1. Air sampling to detect and measure potential concentrations of the chemicals. Both time weighted average (TWA) samples and short term exposure limit (STEL) samples are recommended, as are air samples taken during specific tasks such as roasting, grinding, pouring flavors and opening bins. NIOSH has proposed a recommended exposure limit of five parts per billion for diacetyl and 9.3 parts per billion for 2,3-pentanedione for an eight hour TWA. Fifteen minute STELs proposed by NIOSH are currently set at 25 parts per billion for diacetyl and 31 parts per billion for 2,3-pentanedione.
  2. Implementation of engineering controls and ventilation changes in those areas where air sampling has identified exposures.
  3. Implementation of appropriate fit-tested respirators to be used by workers until workplace interventions can be made to reduce identified exposures and have been proven to do so in follow-up air sampling.
  4. Medical surveillance of the workforce that includes health questionnaires and spirometry to screen for respiratory symptoms or abnormalities in employees. Occupation medicine physicians must be alert to symptoms of progressive shortness of breath and take immediate steps to control further exposure to prevent ongoing deterioration of lung function.

NIOSH recommends ongoing hazard assessment in all industries that use flavorings or in which diacetyl exposure may occur, and in 2015, it published a “best practices” document that describes exposure monitoring and workplace interventions. NIOSH has additionally instituted a “Coffee Processing” webpage containing its recommendations, which will be revised as further information is gathered.