“Popcorn lung” is a term one doesn’t readily forget. It is the euphemism often used for the medical condition bronchiolitis obliterans, a rare, irreversible obstructive lung disease that can necessitate a lung transplant. For the snack industry, manufacturers producing microwave popcorn and the companies supplying diacetyl to those manufacturers, it has become a serious concern during the past decade.

Initially, it was workers at microwave popcorn manufacturers who began alleging that they had developed bronchiolitis obliterans as a result of their exposure to diacetyl in the workplace.  Workers in other plants later followed suit, and even consumers eventually began filing claims alleging exposure to diacetyl through consumption of microwave popcorn.

What does all of this have to do with the beverage industry? A recent investigation claims that the coffee roasting process — even where no flavoring ingredients are used — could expose workers to airborne concentrations of diacetyl similar to those measured in the popcorn plants.

Many working in the beverage industry will recognize diacetyl as a natural byproduct of the fermentation process. Brewers work to balance diacetyl levels in beer to obtain the preferred flavor profile. Diacetyl also occurs naturally in dairy products, fruit and wine, albeit in trace quantities.

The Food and Drug Administration (FDA) has categorized diacetyl as a Generally Recognized as Safe (GRAS) substance since 1980. It is therefore not considered a “food additive” and does not require premarket approval by the FDA. The GRAS approval  was based on effects of ingestion of small quantities of diacetyl, but did not consider the effects of inhalation.

Recently, an investigation conducted by the Milwaukee Journal Sentinel concluded that workers in the coffee industry were at risk from inhalation exposure to diacetyl released during the bean roasting process. In prior cases, claims by coffee workers exposed to diacetyl came from workers handling liquid flavors added to the beans during roasting. But the Journal Sentinel’s investigation focused not on flavor additives, but on the diacetyl naturally released from unflavored beans during the roasting process.

The paper conducted air monitoring tests at two midsized Wisconsin roasters, which picked up airborne diacetyl concentrations similar to those found in popcorn manufacturing plants. These were modern, clean facilities with industrial grade exhaust systems, roasting relatively small batches of beans. The industrial hygienist conducting the air monitoring was therefore surprised at the concentrations detected and surmised that larger facilities roasting more beans on a continuous basis would likely have even higher airborne concentrations of diacetyl. It is important to note, however, that these air monitoring results were momentary snapshots of airborne concentrations, not analyses of true worker exposure over time.

The government presently does not regulate workplace exposure to diacetyl. In 2011, the National Institute for Occupational Safety and Health (NIOSH) proposed short-term, as well as eight-hour, time-weighted exposure limits for workers handling diacetyl, but these occupational exposure limits have yet to be finalized as formal recommendations. The Occupational Safety and Health Administration (OSHA) does not issue workplace standards for diacetyl exposure.

In an attempt to partially fill the void, the California Occupational Safety and Health Standards Board adopted a process-oriented standard for the handling of diacetyl in 2010. This standard sets no exposure limits, but rather mandates industrial hygiene controls, medical surveillance procedures and hazard communication. The standard only applies to California manufacturers using diacetyl or food flavorings containing at least 1 percent diacetyl, not coffee roasters.

Employers of coffee grinders and roasters want to protect their people from avoidable harms in the workplace, as all employers do. The following are some of the measures that can be taken to minimize potentially harmful exposures:

  • Mandate use of personal protective equipment for grinders and roasters, particularly air-purifying respirators.
  • Ensure that ventilation systems in the grinding/roasting rooms have adequate air exchange rates and consider installing local ventilation around grinding and roasting equipment.
  • Provide employees with education and training on potential risks and best practices for avoiding them.

Additionally, periodic medical surveillance, particularly in the form of spirometry testing, can catch and address any developing health effects at an early stage.

 The scientific community remains split on the true health risks that low concentrations of diacetyl pose, but rather than waiting for the science to develop more fully, the use of proper industrial hygiene controls and personal protective equipment is advisable as a means of ensuring the best possible worker safety.