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Flavorings-Related Lung Disease

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In 2000, NIOSH conducted an investigation of exposures at a microwave popcorn manufacturing plant in Missouri.1, 2 Public health officials contacted NIOSH because a cluster of former employees of the facility had developed a rare lung disease called bronchiolitis obliterans. The majority of employees diagnosed with bronchiolitis obliterans had been exposed to mixtures of butter flavoring chemicals. Evaluations of employees working in the plant revealed high rates of both respiratory symptoms and abnormal lung function.1 The investigation concluded that there was "a risk for occupational lung disease in workers with inhalation exposure to butter flavoring chemicals".2

Investigations of other workplaces have also shown that employees that use or manufacture certain flavorings have developed similar health problems.3 Similar findings were also reported in workers exposed in the manufacture of diacetyl.3 Because many of the cases have been associated with popcorn manufacturing plants, the term "popcorn lung" has often been used to describe the respiratory symptoms and fixed obstructive lung disease seen in these employees. Although much of the research and attention has been focused on butter flavorings, employees who are involved in the use or manufacture of other types of flavorings, such as strawberry, caramel, vanilla, and butterscotch, may also be at risk.3 Research is continuing in other industries, such as the investigations that NIOSH is doing at coffee production plants.3, 6

Manufacturing Plant

Flavorings can be either natural or manmade. Some are simple and made up of only one ingredient, but others are complex mixtures of several substances. Employees may be exposed to flavorings in the form of vapors, dusts, or mists.4 There are many different types of flavorings and most have not been tested for respiratory toxicity. The Food and Drug Administration (FDA) regulates the safety of food additives for consumption, but it does not require safety testing of other routes relevant to occupational exposure, such as inhalation. Research continues to determine if certain components or combinations of flavorings are associated with pulmonary disease.

Flavorings commonly contain diacetyl or its structurally similar substitute, 2,3-pentanedione. NIOSH established recommended exposure limits (RELs) of 5 ppb for diacetyl and 9.3 ppb for 2,3-pentanedione as 8-hour time weighted averages (TWAs). NIOSH also recommended 15-minute short-term exposure limits (STELs) of 25 ppb for diacetyl and 31 ppb for 2,3-pentanedione. The higher REL for 2,3-pentanedione was based on analytical limitation.3 The American Conference of Governmental Industrial Hygienists set a threshold limit value (TLV)® of 0.010 ppm as an 8-hour time weighted average and a STEL of 0.020 ppm for diacetyl (ACGIH 2012).5 There are currently no specific OSHA standards for occupational exposure to flavorings, diacetyl, or 2,3-pentanedione. However, OSHA standards regulating all workplaces offer protection to workers exposed to these substances.

NIOSH has also expressed concern about other volatile and reactive flavorings that could potentially have toxic effects that are similar to those caused by diacetyl and 2,3-pentandione exposure. NIOSH recommends controlling exposures to those flavorings with assistance from occupational safety and health professionals and by following recommendations in their criteria document for diacetyl and 2,3-pentandione.3

OSHA Standards

There are currently no specific OSHA standards for occupational exposure to butter-flavoring, diacetyl, or 2,3-pentanedione. However, OSHA standards regulating all workplaces offer protection to workers exposed to these substances.


Health Effects

Describes the health effects of flavorings-related lung disease, diagnosis and treatment.


Diacetyl and 2,3-Pentandione

Provides exposure information for diacetyl and 2,3-Pentadione.


Hazards and Solutions

Provides resources for recognizing and controlling hazards related to flavorings-related lung disease.



Provides links and references to additional resources related to flavorings-related lung disease.


How do I find out about employer responsibilities and workers' rights?

Workers have a right to a safe workplace. The law requires employers to provide their employees with safe and healthful workplaces. The OSHA law also prohibits employers from retaliating against employees for exercising their rights under the law (including the right to raise a health and safety concern or report an injury). For more information see www.whistleblowers.gov or Workers' rights under the OSH Act.

OSHA can help answer questions or concerns from employers and workers. To reach your regional or area OSHA office, go to the OSHA Offices by State webpage or call 1-800-321-OSHA (6742).

Small business employers may contact OSHA's free and confidential On-Site Consultation program to help determine whether there are hazards at their worksites and work with OSHA on correcting any identified hazards. Consultants in this program from state agencies or universities work with employers to identify workplace hazards, provide advice on compliance with OSHA standards, and assist in establishing injury and illness prevention programs. On-Site Consultation services are separate from enforcement activities and do not result in penalties or citations. To contact OSHA's free consultation service, go to OSHA's On-Site Consultation web page or call 1-800-321-OSHA (6742) and press number 4.

Workers may file a complaint to have OSHA inspect their workplace if they believe that their employer is not following OSHA standards or that there are serious hazards. Workers can file a complaint with OSHA by calling 1-800-321-OSHA (6742), online via eComplaint Form, or by printing the complaint form and mailing or faxing it to the local OSHA area office. Complaints that are signed by a worker are more likely to result in an inspection.

If you think your job is unsafe or if you have questions, contact OSHA at 1-800-321-OSHA (6742). Your contact will be kept confidential. We can help. For other valuable worker protection information, such as Workers' Rights, Employer Responsibilities, and other services OSHA offers, visit OSHA's Workers' page.

1 Kreiss K. et al. "Clinical bronchiolitis obliterans in workers at a microwave-popcorn plant." New England Journal of Medicine 347.5(2002): 330-330.

2 NIOSH, (2006). Gilster-Mary Lee Corporation, Jasper, Missouri National Institute for Occupational Safety and Health (NIOSH) Health Hazard Evaluation Report. HETA 2000-0401-299, (January 2006).

3 NIOSH, (2016). Criteria for a recommended standard: occupational exposure to diacetyl and 2,3-pentanedione. U.S. Department of Health and Human Services (DHHS), National Institute for Occupational Safety and Health (NIOSH) Publication No. 2016-111, (October 2016).

4 NIOSH Alert. Preventing Lung Disease in Workers who Use or Make Flavorings. U.S. Department of Health and Human Services (DHHS), National Institute for Occupational Safety and Health (NIOSH) Publication No. 2004-110, (December 2003).

5 ACGIH. 2012 TLVs® and BEIs®: threshold limit values for chemical substances and physical agents and biological exposure indices. Cincinnati, Ohio: American Conference of Governmental Industrial Hygienists (2012).

6 NIOSH, (2017). Evaluation of exposures and respiratory health at a coffee processing facility. NIOSH Health Hazard Evaluation Report No. 2015-0147-3266. (January 2017).


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