Hazard Warning for Roasting Coffee

Roasting coffee beans has been linked to a severe health hazard known as bronchiolitis obliterans, sometimes referred to as obstructive lung disease or popcorn lung.

A Bit of History

This condition came to prominence decades ago when the Missouri Department of health requested assistance from the National Institute of Occupational Safety & Health (NIOSH) to investigate why former workers from a microwave popcorn manufacturing facility had developed this disease. The investigation revealed workers were breathing vapor that contained food flavorings they were adding to popcorn. The food flavorings were a combination of natural and manmade ingredients. The research done by NIOSH scientists revealed certain chemicals in the manmade flavorings, while safe to eat, were unsafe if inhaled.

While there is more than one chemical that can cause the condition, the one noted most often is diacetyl, described as having a “buttery flavor.” Diacetyl, as well as related chemicals, react on contact with the mucus membranes in the airway when inhaled. This causes irritation and inflammation and as it is inhaled deeper into the lungs it continues to react damaging the epithelium tissue, which causes the body to create scar tissue. It is this scar tissue that restricts your ability to breathe. There is no cure for this condition and treatment options are limited. The best treatment is exposure prevention; workers must be protected from breathing any vapors or dust generated by the flavoring ingredients as they are added or mixed with food products.

This condition is not limited to flavoring popcorn. There are reports that other workers exposed to adding flavorings to manufactured food products could also be at risk. It has also been found to exist in the vaping industry in the liquid flavorings used for e-cigarettes.

As a result of the research into the popcorn workers exposure, NIOSH has issued this NIOSH Alert through the Centers for Disease Control (CDC): “Preventing Lung Disease in Workers: Who Use or Make Flavorings.” It outlines the problem and recommends workplace controls.  The CDC also provides additional information on flavorings-related lung disease.

Coffee Roasting

So, what does this have to do with roasting coffee? First, if the coffee being roasted will have flavorings added to it, the flavoring products have to be closely scrutinized to determine if they contain any of the chemical compounds known to cause obstructive lung disease. In addition to diacetyl, workers could also be exposed to related flavoring chemicals including 2,3-pentanedione or 2,3-butanedione. A review of each flavoring ingredient’s Safety Data Sheet (SDS) is the first step, but it might also be necessary to check with the manufacturer of the flavoring.

More importantly, it has been found that diacetyl will occur or be released naturally when coffee is roasted. It is a natural byproduct of the roasting process, having nothing to do with the addition of flavorings. The diacetyl released during the roasting process can cause an exposure level that will be hazardous to workers.  This was revealed when the Milwaukee Journal-Sentinel did an in-depth investigation with the assistance of two Wisconsin coffee roasting companies. In some areas, they found worker exposure was four times the Recommended Exposure Level (REL) issued by NIOSH of 5 ppb (parts per billion) for diacetyl.

The CDC also provides additional information for coffee roasting facilities, including the following examples of workplace interventions: engineering controls, personal protective equipment, administrative controls, and medical surveillance.

Next Steps

If you roast coffee and/or add chemical flavorings to food products, you should conduct a review of your workplace exposure. If you add flavorings, begin with a review of the CDC information related to flavorings-related lung disease. Next, review in detail the SDS for each flavoring additive you are using as well as any other information you can obtain from the manufacturer of the flavoring chemical. If the flavoring contains any chemicals that are known or suspected of causing obstructive lung disease, try to replace them with a safer alternative.

Whether you add flavorings or only roast coffee, your next step is to evaluate the worker’s airborne exposure to diacetyl or flavoring chemicals generated as a result of a coffee roasting process or from the addition of flavoring chemicals to coffee or other food products. This is best done by bringing in an Industrial Hygienist who is also a Certified Industrial Hygienist (CIH).

The hygienist should conduct individual air sampling to clearly define each worker’s actual exposure. At the same time, they can evaluate the general and local exhaust ventilation in the area where the chemicals are added and make recommendations for improvement. When dealing with any occupational health exposure, your first choice is always to engineer out the exposure. This is done by substitution with a safer product or through improved ventilation, typically local exhaust ventilation, which will remove any hazardous vapor from the workplace and the employee’s breathing zone.

If engineering controls are not effective in reducing the workplace exposure below the REL, then it will be necessary to implement a written respiratory protection program consistent with the Occupational Safety & Health Administration (OSHA) Respiratory Protection standard for General Industry 29 CFR 1910.134. ­­

Do not try to short-cut this process and just handout respirators. As stated in part from section (a)(1) of OSHA’s respiratory protection standard, “In the control of those occupational diseases caused by breathing air contaminated with harmful dusts, fogs, fumes, mists, gases, smokes, sprays, or vapors, the primary objective shall be to prevent atmospheric contamination. This shall be accomplished as far as feasible by accepted engineering control measures (for example, enclosure or confinement of the operation, general and local ventilation, and substitution of less toxic materials)…” Only then, if the engineering controls are not effective or if there will be a delay in implementation, should respirators be used – and then only with a written respiratory protection program that ensures employees can safely and properly wear the respirator.

When it comes to risk management, prevention is key. Contact our risk control team for more information about keeping your workplace a safe place.

-Tim Hoffmann


Tim has broad experience working with manufacturers, school districts, distributors, service industries, municipalities and the hospitality industry. He is a Certified Safety Professional (CSP), holds the Associate Loss Control Management (ALCM) designation, and is a Professional Member of the American Society of Safety Engineers (ASSE).

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