What Is Diacetyl and Why Is It a Concern in Coffee Facilities?
Diacetyl is a volatile chemical substance also known as 2,3-butanedione.
It is found in many foods and has been used by food manufacturers to create buttery or creamy flavor notes in products such as popcorn and other flavored foods.
Diacetyl became widely known after investigations involving microwave popcorn factory workers, where inhaled flavoring vapors were linked to severe small-airway disease.
That history is important, but coffee facilities present a more complicated exposure picture.
In coffee production, diacetyl may appear in two different ways: it can be added through flavorings used in flavored coffee products, and it can also be generated naturally during the roasting and grinding of coffee beans.
The Centers for Disease Control and Prevention (CDC), the National Coffee Association, and the University of Washington all note that roasting coffee beans can produce diacetyl and the related compound 2,3-pentanedione as a natural byproduct of the coffee roasting process.
That means the concern in coffee facilities is not limited to butter-flavored coffee or specialty flavoring rooms.
NIOSH has warned that air sampling in coffee plants should focus on roasting, grinding, opening storage bins, pouring and adding flavorings, and packaging because those tasks can create meaningful airborne concentrations in production areas and packaging areas.
In other words, workers may face exposure even in facilities that do not resemble classic flavoring manufacturing plants.
The legal and medical concern is inhalation.
Diacetyl may be acceptable to eat in food, but breathing repeated concentrations of flavoring emissions or roasting emissions is a different issue, especially in enclosed workspaces with poor ventilation or heavy production demands.
CDC states that workers exposed to diacetyl and similar chemicals are at risk of severe respiratory impairment, and studies in coffee facilities have linked those exposures to tasks involving roasting, grinding, packaging, and flavoring.
How Diacetyl Can Be Created During Roasting and Grinding Coffee Beans
Diacetyl is a natural byproduct of coffee roasting formed via the Maillard reaction, a chemical reaction between the beans’ sugars and amino acids.
Diacetyl is often most concentrated in fresh, dark-roasted ground coffee.
Darker and especially flavored coffees tend to have higher levels of diacetyl.
The concentration and exact volatile organic compounds (VOCs) released during coffee roasting depend on the roasting temperature, duration, coffee bean variety, and grinding process.
NIOSH-backed research states that both compounds are natural byproducts of roasting and are emitted during roasting, grinding, and packaging whole bean and ground coffee, which means exposure can occur even in facilities that do not add flavorings.
Grinding is especially important because breaking roasted beans apart can release trapped gases and create larger short-term emissions near equipment, and studies have found relatively high air concentrations during grinding, packaging, and flavoring tasks.
For coffee roasters and nearby production staff, that can mean low concentrations in some parts of a facility but large concentrations near grinders, open containers of roasted beans, and enclosed process points, with lower but still meaningful migration into other areas if ventilation and separation are weak.
How this happens in practice:
- Beans continue to off-gas after roasting, so opening bins, hoppers, or storage containers can release diacetyl-containing emissions into the worker’s breathing zone.
- Grinding increases surface area and disturbs the beans, which can cause sharp short-term spikes around the machine and nearby operator stations.
- Bagging and packaging can keep exposures elevated because freshly ground coffee continues releasing vapors while it is weighed, filled, sealed, and moved.
- Workers assigned to cleanup, maintenance, or material transfer can still be exposed when dust, residual grounds, and trapped vapors are released during ordinary handling.
- Exposure does not stay confined to one machine, because NIOSH and peer-reviewed studies emphasize isolating grinding, flavoring, and packaging sources from the main workspace to keep emissions from spreading into other areas.
How Added Coffee Flavorings Can Increase Diacetyl Exposure Risks
Added coffee flavorings can increase diacetyl exposure risks because flavoring formulations often contain diacetyl and the related compound 2,3-pentanedione, both of which may be released into the air when workers pour, mix, or apply those ingredients to roasted beans.
NIOSH has specifically identified “pouring and adding flavorings” as a task that should be sampled in coffee facilities because it can create meaningful short-term exposure and help reveal where controls are needed.
In coffee roasting and flavoring plants, these exposures often rise in flavoring rooms and adjacent workstations where liquids or coatings are handled in open processes rather than sealed systems.
A 2025 NIOSH health hazard evaluation found that one of the three main diacetyl sources in a coffee roasting and packaging facility was flavoring chemicals added to roasted coffee beans in the flavoring area, alongside grinding emissions from unflavored coffee.
That matters because flavoring can add a second diacetyl source on top of the natural emissions already produced by roasting and grinding, which may increase the total airborne burden workers inhale during a shift.
For workers assigned to flavoring, packaging, or nearby production tasks, the risk is not limited to direct handling alone, since emissions can move through the facility if ventilation, isolation, and capture controls are weak.
How Are Coffee Workers Exposed to Diacetyl?
Coffee workers are exposed to diacetyl mainly when roasting, grinding, packaging, and flavoring activities release alpha-diketone emissions into the air, including both naturally generated diacetyl from roasted beans and diacetyl from added flavorings.
Regulators have repeatedly identified grinding, packaging, opening containers of roasted coffee, and pouring or adding flavorings as tasks that can create meaningful airborne exposure, and NIOSH has warned that workers in coffee production facilities may face serious respiratory hazards from these emissions.
The highest risk often occurs in confined production spaces around grinders, bagging stations, and flavoring areas, where vapors can build up and where workers may spend hours each shift near active emission sources.
Studies and health hazard evaluations have also found that exposures are not limited to one station, because emissions can migrate into nearby work zones when source capture, enclosure, and general ventilation are weak.
Coffee facility job roles most at risk of diacetyl exposure include:
- Coffee roasters working near roasting drums, cooling trays, and bean transfer points
- Grinder operators assigned to industrial grinders or small-batch grinding equipment
- Packaging line workers who bag, seal, and handle freshly ground coffee
- Flavoring technicians who pour, mix, or apply liquid or powdered coffee flavorings
- Quality control employees who cup, grind, test, or sample coffee repeatedly during production
- Production associates who move roasted beans, open storage bins, or load hoppers
- Maintenance workers who service grinders, roasters, ducting, or enclosed equipment with residual vapors
- Sanitation workers who clean flavoring rooms, grinders, bins, and packaging equipment
- Warehouse or materials-handling staff working near roasting and packaging operations in enclosed facilities
Workers in coffee roasting facilities often face the highest exposure during grinding and packaging because those processes disturb roasted coffee and can release concentrated diacetyl vapors directly into the breathing zone.
NIOSH has also emphasized that the highest exposure settings are workplaces where flavoring chemicals are heated, mixed, or packaged, which makes flavored coffee operations especially important when evaluating risk. Proper ventilation, local exhaust systems, source enclosure, and protective equipment are all recognized control measures for commercial roasting facilities because they can reduce airborne concentrations where exposure is most intense.
OSHA likewise recommends exposure assessment, engineering controls, work practices, personal protective equipment, and medical monitoring with lung function testing for workers exposed to flavorings.
Safety Regulations for Diacetyl in the Coffee Roasting Industry
There is currently no diacetyl-specific OSHA standard, but the Occupational Safety and Health Administration (OSHA) states that existing workplace rules still apply to employers whose workers are exposed to diacetyl, butter-flavoring chemicals, or 2,3-pentanedione.
That matters in coffee roasting and other food production settings because employers still have a duty to protect workers from recognized inhalation hazards under the OSH Act’s General Duty Clause.
OSHA and NIOSH also recommend practical controls such as air monitoring, engineering controls, work practices, respirators when needed, medical monitoring with lung function testing, and employee training to reduce exposure and keep employees safe.
NIOSH has gone further by publishing recommended occupational exposure limits for diacetyl and 2,3-pentanedione, aimed at reducing the risk of decreased lung function and obliterative bronchiolitis from workplace exposure.
In coffee facilities, those rules and recommendations are most relevant where roasting, grinding, flavoring, and packaging operations can release airborne alpha-diketones into workers’ breathing zones.
Regulations and regulatory measures that apply to diacetyl exposure include:
- OSH Act Section 5(a)(1), the General Duty Clause, which requires employers to provide a workplace free from recognized hazards likely to cause death or serious physical harm
- 29 CFR 1910 Subpart I, Personal Protective Equipment, including OSHA’s general PPE requirements
- 29 CFR 1910.134, Respiratory Protection, covering respirator programs where engineering controls do not fully control inhalation risk
- 29 CFR 1910.1000 and Table Z-1, Air Contaminants, OSHA’s general industry air contaminant framework
- 29 CFR 1910.1200, Hazard Communication, requiring chemical hazard communication, labeling, and safety data information for workers
- OSHA-approved State Plans, which may impose standards or enforcement programs that are at least as effective as federal OSHA and can be more stringent
- NIOSH recommended exposure limits (RELs) for diacetyl and 2,3-pentanedione, used as important guidance even though they are not OSHA PELs
NIOSH has conducted exposure evaluations at numerous coffee production facilities to assess how diacetyl and related compounds affect worker safety, including facilities involved in roasting, grinding, flavoring, and packaging coffee.
Employers are expected to use air monitoring and medical surveillance, including breathing questionnaires and spirometry, to identify elevated exposures and catch early signs of respiratory injury before lung damage progresses.
OSHA and NIOSH also encourage engineering controls such as fume extractors, local exhaust ventilation, and source isolation to reduce exposure in areas where airborne concentrations are highest.
Diacetyl may be considered safe to ingest in the small amounts found in food and drinks, but federal health agencies have made clear that inhalation at high concentrations presents a very different hazard.
Where those protections are weak, delayed, or missing, the regulatory record can become important evidence in later claims involving occupational lung disease.
Can Coffee Roasting Cause Popcorn Lung?
Popcorn lung is the common name for bronchiolitis obliterans, a serious and irreversible lung disease that scars and narrows the smallest airways.
In coffee facilities, the condition has drawn attention because inhaled diacetyl and related compounds can damage the bronchioles and produce lasting respiratory impairment.
The health effects often begin with shortness of breath, wheezing, chest tightness, and a persistent dry cough, and some workers also report unusual fatigue as symptoms worsen over weeks or months.
Some exposed workers also develop eye, nose, and sinus irritation, and diacetyl exposure has been associated with occupational asthma and airway inflammation in addition to fixed small-airway injury.
The disease is often difficult to diagnose because its symptoms can resemble asthma or chronic obstructive lung disease, which can delay recognition while lung damage continues to progress.
In severe cases, bronchiolitis obliterans can cause profound loss of lung function, and some workers in flavoring-related cases have deteriorated to the point of requiring a lung transplant.
Popcorn lung remains one of the most serious health effects associated with diacetyl exposure: it can develop over a relatively short period, permanently reduce breathing capacity, and leave workers with life-altering respiratory limitations.
About Bronchiolitis Obliterans (Popcorn Lung)
Bronchiolitis obliterans, commonly called popcorn lung, is a rare disease that damages the bronchioles, the smallest airways in the lungs, and causes fixed breathing problems that do not fully reverse.
In severe cases, lung function can fall dramatically, and CDC case reports involving coffee workers show FEV1 values near 20% of predicted, illustrating how profoundly the condition can limit breathing capacity.
Some workers also report dark or black mucus along with worsening respiratory symptoms, especially when the disease develops in a setting with ongoing airborne irritant exposure, but the hallmark features remain persistent airflow obstruction and progressive shortness of breath.
Symptoms of popcorn lung include:
- Shortness of breath that becomes more noticeable with exertion
- A persistent dry cough and wheezing that may resemble asthma
- Fatigue or reduced stamina as breathing becomes more difficult
- Diagnostic confusion with asthma or chronic obstructive lung disease, which can delay proper treatment
- Severe obstruction on pulmonary function testing in advanced cases
Who May Qualify for a Diacetyl Coffee Roasting Lawsuit?
Workers may qualify for a diacetyl coffee roasting lawsuit when they developed bronchiolitis obliterans, flavorings-related lung disease, or another serious respiratory condition after repeated inhalation exposure in a coffee facility.
In coffee plants, the strongest claims usually involve roasting, grinding, flavoring, packaging, or quality-control work performed around airborne diacetyl and 2,3-pentanedione sources, especially in enclosed or poorly ventilated areas.
Lawsuits related to diacetyl exposure often require evidence of specific job duties, where the employee worked, how close the employee was to grinders or flavoring stations, and what the likely exposure levels were over time.
These cases also commonly allege that employers failed to provide adequate warnings, exposure controls, respirators, ventilation, or medical monitoring even though the respiratory hazard was known or knowable.
The first popcorn-lung lawsuits grew out of workplace clusters and targeted manufacturers and chemical suppliers, and modern coffee-worker claims follow the same basic theory when a company allegedly exposed workers without proper protection.
A qualifying case usually becomes stronger when medical records, pulmonary testing, coworker testimony, safety documents, and industrial hygiene evidence all point in the same direction.
People who may qualify can include:
- Coffee roasters who worked near roasting drums, cooling trays, or bean transfer points
- Grinder operators exposed during industrial grinding or small-batch grinding
- Packaging workers who handled freshly ground coffee in bagging and sealing areas
- Flavoring technicians who poured, mixed, or applied liquid or powdered coffee flavorings
- Quality-control employees who repeatedly ground, tested, or sampled coffee during production
- Maintenance and sanitation workers who cleaned or serviced grinders, bins, ductwork, or flavoring equipment
- Warehouse or production staff who worked near major emission sources in the facility
- Former coffee-facility employees whose symptoms appeared after they left the job but were later tied back to workplace exposure
Not every coffee worker with breathing symptoms will have a valid claim, because diagnosis, exposure history, and the available proof all matter.
The key question is whether the facts support a credible connection between coffee-facility exposure and a documented lung injury, along with evidence that another party failed to control or warn against the hazard.
Evidence for a Coffee Roasting Diacetyl Exposure Lawsuit
Evidence is critical in a coffee roasting diacetyl exposure lawsuit because these cases usually depend on proving both the source of exposure and the seriousness of the resulting lung injury.
Strong claims often require proof of specific job duties, where the worker spent time in the facility, and whether those duties placed the worker near roasting, grinding, flavoring, or packaging emissions.
These lawsuits also commonly allege that employers failed to provide adequate warnings, ventilation, respirators, air monitoring, or other exposure controls despite the known inhalation hazard.
The strongest cases connect the medical diagnosis, the work history, and the safety record into one clear exposure narrative.
Evidence in a coffee roasting diacetyl exposure lawsuit may include:
- Employment records showing job titles, departments, dates of employment, and assigned duties
- Detailed work history describing time spent in roasting, grinding, flavoring, packaging, or quality-control areas
- Medical records documenting bronchiolitis obliterans, flavorings-related lung disease, occupational asthma, or another respiratory diagnosis
- Pulmonary function tests showing reduced or fixed lung impairment
- CT scans, imaging reports, and lung biopsy results when available
- Air monitoring data, industrial hygiene reports, or exposure testing from the facility
- Safety data sheets, flavoring ingredient records, and internal hazard communications
- Evidence of missing or inadequate ventilation, local exhaust systems, respirators, or protective equipment
- Training records showing whether workers were warned about inhalation hazards
- Coworker statements about visible fumes, odors, symptoms, and working conditions
- OSHA records, inspection findings, or internal incident reports
- Wage loss records, disability documentation, and proof of other damages tied to the lung injury
Compensation in Popcorn Lung Lawsuit Claims
Damages in popcorn lung lawsuit claims are the financial and personal losses caused by a serious respiratory injury, including what the condition has already cost and what it is likely to cost in the future.
In diacetyl cases, compensation may include medical expenses, lost wages, and damages tied to reduced quality of life after permanent lung damage changes a person’s health, work capacity, and daily routine.
Lawyers assess damages by reviewing medical records, treatment needs, work history, wage loss, and the long-term impact of breathing impairment on ordinary life activities.
They then use that evidence to calculate a compensation demand that reflects both past losses and the future consequences of living with a chronic, irreversible lung disease.
Compensation in popcorn lung lawsuit claims may include:
- Past and future medical expenses
- Pulmonary specialists, testing, imaging, and prescription costs
- Oxygen therapy, pulmonary rehabilitation, and respiratory support
- Lost wages from missed work
- Reduced earning capacity if the worker cannot return to the same job
- Pain and suffering
- Reduced quality of life
- Physical limitations affecting exercise, sleep, and daily activity
- Out-of-pocket costs tied to treatment and travel
- Disability-related losses
- Wrongful death damages, where applicable
TorHoerman Law: Investigating Diacetyl Exposure Lawsuits
Diacetyl exposure cases require careful investigation into workplace conditions, medical evidence, and the companies responsible for producing or using flavoring chemicals.
Workers in coffee roasting and other food production environments may have spent years inhaling airborne compounds without clear warnings about the potential respiratory risks.
When a serious lung condition develops, the legal process focuses on determining whether employers, suppliers, or manufacturers failed to control exposure or provide adequate safety protections.
A thorough legal review can connect medical findings with work history and exposure conditions to determine whether a claim may be viable.
If you or a family member worked in coffee roasting, grinding, flavoring, or packaging and were later diagnosed with bronchiolitis obliterans or another serious respiratory illness, TorHoerman Law can review your situation.
Our attorneys investigate diacetyl exposure lawsuits by examining employment records, medical documentation, and the safety practices used in the facility where exposure occurred.
Contact TorHoerman Law for a confidential case review to learn whether you may have grounds to pursue compensation for diacetyl-related lung injury.
