Worker health and wellness Workplace exposures Respiratory conditions Food Manufacturing

Workers and diacetyl: 5 things to know

From microwave popcorn manufacturing workers to coffee roasters, employees who work with certain flavoring chemicals may be at risk for lung disease

Workers and diacetyl: 5 things to know

UPDATE: This article has been updated with information – describing how diacetyl can be produced naturally – unintentionally removed during the editing process.

Sixteen years ago, an irreversible lung disease showed up in a cluster of people who had worked at a microwave popcorn processing plant in rural Missouri. The disease, called bronchiolitis obliterans, would also come to be known as “popcorn lung.” Exposure to diacetyl, a flavoring chemical, has been linked to the disease.

Nearly two decades later, it appears that workers who roast coffee are at risk of exposure to diacetyl – as well as a substitute, 2,3-pentanedione – and at risk of contracting the same disease.

Diacetyl and 2,3-pentanedione can be created and added to foods such as popcorn, candy and baked goods, and in the liquid users “vape” in e-cigarettes. However, the chemicals also are naturally produced when coffee is roasted. Inhalation is the main route of exposure.

The exposure is much more widespread than we thought initially.

Dan Morgan
Respiratory Toxicology Group,
National Institute of Environmental Health Science

To help protect workers from 2,3-pentanedione and diacetyl, NIOSH on Oct. 31 released a document that includes recommended exposure limits and work practices.

“It’s so important when somebody is working in a facility with flavoring chemicals like diacetyl or 2,3-pentanedione, if they have any respiratory symptoms at all – cough, shortness of breath or wheezing – they be removed from exposure until they’re evaluated,” said Rachel Bailey, medical officer in the NIOSH Respiratory Health Division. “Because if they have this disease, it doesn’t improve. We don’t want it to get worse over time.”

Here, Safety+Health presents five things to know about diacetyl and 2,3-pentanedione.


Bronchiolitis obliterans symptoms

The symptoms of bronchiolitis obliterans, also known as obliterative bronchiolitis, are brought on when the lungs’ smallest airways become narrowed by scar tissue. Typically, symptoms do not improve when a worker is away from the job. The majority of cases have limited or no response to medical treatment, and, according to NIOSH, several patients have gone on waiting lists for lung transplants.

“Diacetyl and the related ketones are highly reactive chemicals, so they basically react on contact with the mucus membranes and the epithelium that lines the entire respiratory tract, so exposure to a vapor of this would cause irritation of the mucus membranes in the eyes, nose and throat,” said Dan Morgan, head of the Respiratory Toxicology Group at the National Institute of Environmental Health Sciences in Research Triangle Park, NC.

“When it gets deeper into the lung or respiratory tract, you get damage to the epithelium that lines the small airways, and this results in inflammation,” Morgan said. “The body tends to repair this damage by putting down scar tissue in the walls of the airways. This … can progress to a severe obstructive lung disease.”

David Egilman was more direct.

“It’s like you’re drowning all the time,” said Egilman, a doctor and clinical professor of family medicine at Brown University in Providence, RI. He has served as an expert witness for sick workers in their lawsuits against flavoring companies.


Widespread exposure

In 2000, NIOSH investigated severe lung disease seen in former employees of a microwave popcorn processing facility in Jasper, MO. Eight individuals had “fixed airways obstruction,” according to an agency alert. NIOSH found a connection between exposure to vapors from flavoring chemicals and lower lung function.

More than a decade later, the disease emerged among those who work with coffee. In 2013, bronchiolitis obliterans was reported in five former workers of a small processing facility in Tyler, TX.

To encompass the various industries connected with the disease, popcorn lung also is known as “flavorings-related lung disease.”

“The exposure is much more widespread than we thought initially,” Morgan said. “Any industry where the flavorings are mixed or heated can result in higher exposures. They’ve been looking at more and more different industries, and they’ve seen exposure in a lot of places where they haven’t really looked before.”

After sick workers filed lawsuits in the 2000s, flavoring companies moved away from using diacetyl but turned to substitutes that studies also have found to be harmful, according to Scott Hall, senior counsel with the Kansas City, MO-based law firm Motley Rice LLC.

“It’s important for us to look beyond diacetyl and these substitutes to see if there are other chemicals being used in the flavoring industry that are analogous and have similar structures and could cause similar disease,” Hall said Oct. 13 during a National Council for Occupational Safety and Health webinar. “It’s important for us to think how we can take action to keep pressure on industry and regulators to prevent more workers from becoming ill.”

In September, National COSH released a fact sheet about the hazards of food flavorings, warning that any potential exposures to flavoring chemicals should be considered dangerous.

Diacetyl and 2,3-pentanedione also have been found in e-cigarettes, a highly popular alternative to traditional tobacco cigarettes. A study published in December 2015 by the Harvard T.H. Chan School of Public Health determined that 39 of the 51 tested flavored e-cigarettes and liquids contained diacetyl and 23 contained 2,3-pentanedione.

“What is of concern is that the exposure pathway that led to illness in many workers – namely inhaling heated flavoring chemicals – is the same exposure pathway that is occurring for users of flavored e-cigarettes,” said Joseph G. Allen, lead study author and assistant professor at the school.


What NIOSH is doing

In 2015, the Milwaukee Journal Sentinel hired an industrial hygienist to test the air in two Wisconsin coffee-roasting facilities. Both had levels higher than safety recommendations allow, the newspaper reported in April.

One of the facilities, Madison, WI-based Just Coffee Cooperative, requested NIOSH conduct a health hazard evaluation. When the evaluation was performed in July 2015, researchers found some air samples were above the NIOSH recommended exposure limits for 2,3-pentanedione and diacetyl, according to an agency interim report. Some workers said they had work- related sneezing, and one had sinus issues from green coffee dust.

NIOSH also found “high instantaneous concentrations” of the chemicals – in some cases, more than 7,000 parts per billion of diacetyl – as well as high levels of carbon dioxide and carbon monoxide in storage bins that contained roasted beans. The agency cautioned workers to avoid putting their heads inside or near uncovered bins.

NIOSH has been conducting health hazard evaluations at about 20 coffee- processing facilities and collecting air samples during specific job tasks. The agency is planning to administer questionnaires to determine workers’ respiratory symptoms and breathing tests to assess lung function, Bailey said.

“Our goal of air sampling is to identify areas, tasks or jobs with high exposures that require exposure control,” Bailey said. “Once we know where the high air level concentrations are, then we can work on recommendations of how to get these air levels down through exposure control.”

At one facility, the agency observed higher concentrations of the chemicals where coffee beans were ground. The surface area of coffee beans increases as they are ground, releasing higher concentrations of the chemicals.

Both cumulative and peak exposures likely play a role in respiratory disease, and workers can develop the disease within months or years of exposure, Bailey said.

“We certainly saw in the microwave popcorn industry that when workers would empty the artificial butter flavoring into the mixing tank, when they dumped it, they’d get a peak exposure,” Bailey said. “In the flavor manufacturing industry, we saw one plant where they had three severe cases of obliterative bronchiolitis among 18 workers who had current or past exposure. These workers, when they packaged the powdered flavoring they produced, they would get these spikes of exposure.”

In October, the agency released finalized recommended exposure limits to help protect workers: 5 parts per billion for diacetyl and 9.3 ppb for 2,3- pentanedione for a maximum of 8 hours per day during a 40-hour work week. The short-term exposure limits are 25 ppb for diacetyl and 31 ppb for 2,3- pentanedione over a 15-minute timespan.

“Industry needs some guidance on what safe exposure is so they can put in proper procedures to protect their workers,” Morgan said. “It’s a very conservative number [for diacetyl]. They’ve estimated below that level, workers shouldn’t have any more than a 1-in-1,000 chance of having reduced lung function.”


What OSHA has done

OSHA has no specific standards regulating workplace exposure to diacetyl and butter flavoring, but the agency notes its standards for all workplaces can protect exposed workers and has released validated methods for air monitoring of diacetyl and 2,3-pentanedione.

In 2006, current OSHA administrator David Michaels – then a professor and associate chairman of the Department of Environmental and Occupational Health at George Washington University’s School of Public Health – was one of several experts who supported a labor union-led petition calling for an emergency temporary standard on diacetyl.

OSHA published an advance notice of proposed rulemaking in 2009 but withdrew it later “to facilitate timely development of a standard.” In 2012, the rulemaking was moved to “long-term status” on the agency’s regulatory agenda. It is not on the current agenda. OSHA has stated it plans to use parts of the NIOSH criteria document for its rulemaking.

“Given the resources it takes for OSHA to issue a standard and – for the most part – exposures were under control, it didn’t make sense to pursue issuing a standard because there are other exposures that are really quite a bit more serious,” Michaels said Oct. 18 during the 2016 National Safety Council Congress & Expo in Anaheim, CA. “But that leaves us still without a standard, and theoretically workers could be exposed, though the companies that expose them would face liability.

“The bigger concern though – and this is also related to OSHA standard- setting – is how safe are the substitutes? We don’t know. We don’t have human evidence. We have some animal evidence that they could be causing lung disease. It’s not even clear we could regulate a substitute if we wanted to because we can’t necessarily show significant risk. It really is wrapped into this challenge of how do you manage exposure to toxic or potentially toxic chemicals in the workplace, and we don’t have a good answer for that.”

In 2010, California, which runs its own occupational safety and health program, became the first state to implement a diacetyl standard. Employers in the state must protect employees who work with certain concentrations of the chemical through measures such as exposure level monitoring and medical surveillance.


How workers can be protected

In its recently released criteria document, NIOSH outlines a “hierarchy of controls” for controlling exposure: elimination/substitution, engineering controls, administrative controls and PPE. The agency cautions that information on the toxicity of substitutes is limited, and exposure may need to be controlled even with substitutes.

Examples of controls include:

  • Using local exhaust ventilation to trap and remove emissions
  • Separating rooms in which flavorings are handled with walls, doors or other boundaries
  • Forbidding workers from eating, drinking and smoking in work areas where flavoring compounds are used
  • Keeping mixing and other processes with high exposures away from other workplace areas

The document also provides information on medical monitoring and surveillance of exposed workers, stating that the most critical part of an effective medical monitoring program for an exposed worker is tracking spirometry test results to determine excessive decreases in lung function.

“It can be very disabling to doing things like getting up and walking around a room,” Bailey said about the disease. “[If] there’s a suspicion a person has this disease, you want to get them away from the exposure as soon as possible to stop the progression of the disease because usually when the exposure stops, the progression of disease stops, but the disease doesn’t get any better.”

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