diacetyl
diacetyl

Diacetyl (butter flavor)

Common names: Diacetyl, 2,3-Butanedione, Biacetyl, Butter Flavoring (commonly used in food industry), E150a (when referring to caramel color, which may contain diacetyl as a byproduct).
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KIDSADVISORY SAFETY RATING
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Risky
Published by Jordana Tobelem, RD, LDN — Last Updated on Apr 16, 2025
Medically reviewed by Dr. William Lin, MD
Diacetyl is a naturally occurring compound that imparts a buttery flavor and aroma, making it a popular additive in the food industry. It is widely used in dairy products, snack foods, and microwave popcorn to enhance flavor profiles. Its volatile nature and strong sensory impact make it a key ingredient in butter-flavored products and artificial flavorings.[1]
Despite its widespread use, diacetyl has raised health concerns, particularly regarding respiratory issues in workers exposed to high levels during manufacturing. Long-term inhalation has been linked to "popcorn lung" (bronchiolitis obliterans), though dietary exposure is considered safe for consumers. Regulatory agencies continue to monitor its use, and many manufacturers have reduced or replaced diacetyl in food products to address safety concerns.[2]

Safety Overview

Regulatory Bodies

FDA (US)
The U.S. Food and Drug Administration (FDA) classifies diacetyl as Generally Recognized As Safe (GRAS) for consumption in food, but it has issued warnings about occupational inhalation risks in manufacturing settings.[1]
Health Canada
Health Canada permits the use of diacetyl as a food additive but advises caution in occupational settings due to potential respiratory risks.[3]
EFSA (Europe)
The EFSA has evaluated diacetyl and considers it safe for use in food at specified levels, though it emphasizes the need for further research on long-term exposure effects.[2]
WHO (World Health Organization)
The WHO, through the Joint FAO/WHO Expert Committee on Food Additives (JECFA), has not established an ADI for diacetyl but acknowledges its widespread use and safety in food at typical exposure levels.[4]

FDA GRAS

U.S. Food and Drug Administration – Generally Recognized as Safe (GRAS)
Current Status
Classified

EWG Rating

Environmental Working Group
  • EWG Rating: Diacetyl is rated a moderate hazard by the Environmental Working Group due to concerns about respiratory risks and limited safety data.[5]
  • Level of Caution: The EWG advises moderate caution, particularly for occupational exposure, as inhalation of diacetyl has been linked to severe respiratory issues.[5]
  • Possible Health Risks: Inhalation of diacetyl can cause "popcorn lung" (bronchiolitis obliterans), though dietary exposure is considered low-risk for consumers.[5]
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More about Diacetyl (butter flavor)

  • Dairy Products: Butter, cheese, yogurt
  • Snack Foods: Microwave popcorn, potato chips, crackers
  • Baked Goods: Cakes, cookies, pastries

Historical Use
Diacetyl gained prominence in the early 20th century as a key component in butter flavoring, particularly in margarine and processed foods. Its use expanded in the mid-20th century with the rise of microwave popcorn and snack foods, where it became a staple for its strong buttery flavor.[1][6]
Current Exposure
Consumers are frequently exposed to diacetyl through butter-flavored products such as microwave popcorn, margarine, and baked goods. It is also found in some dairy products, snack foods, and flavored oils, though many manufacturers have reduced or replaced it due to health concerns.[6]

Bronchiolitis Obliterans (Popcorn Lung)
Long-term inhalation of diacetyl has been linked to bronchiolitis obliterans, a severe and irreversible lung disease characterized by inflammation and scarring of the small airways, leading to breathing difficulties[7]. Occupational exposure, particularly in workers handling food flavorings, has been a primary concern.[8]
Respiratory Irritation
Acute exposure to diacetyl vapors can cause coughing, wheezing, and shortness of breath, especially in environments with high concentrations, such as factories producing flavored food products.[9]
Potential Neurological Effects
Some studies suggest that diacetyl may have neurotoxic properties, as it can cross the blood-brain barrier and contribute to oxidative stress, potentially playing a role in neurodegenerative diseases.[10]
Possible Carcinogenic Risk
While diacetyl itself is not classified as a carcinogen, concerns exist regarding its potential to form harmful byproducts, particularly when heated, as seen in e-cigarettes and some industrial processes.[11]

Toxicological Studies
Animal studies indicate that inhalation of diacetyl at concentrations above 25 ppm can cause airway inflammation and epithelial damage, with repeated exposure leading to irreversible lung fibrosis[9]. Oral toxicity studies suggest that diacetyl is generally recognized as safe (GRAS) for consumption at low levels, but high doses in rodents have been associated with oxidative stress and cellular damage.[12]
Long-Term Safety
Chronic inhalation exposure in occupational settings has been linked to significant declines in lung function, with workers exposed to >5 ppm over extended periods showing increased risk of bronchiolitis obliterans.[13] While dietary exposure is considered low-risk, concerns remain over cumulative effects, particularly in individuals with preexisting respiratory conditions or repeated exposure through vaping products.[13]

High-Risk Groups
Workers in industries such as microwave popcorn production, flavoring manufacturing, and coffee processing are at increased risk of respiratory diseases due to diacetyl exposure.[6] Studies have linked occupational exposure to diacetyl with severe respiratory impairment and bronchiolitis obliterans, a serious lung disease.[14]
Health Impacts
Research indicates that even short-term exposure to diacetyl can make the lungs more vulnerable to infections.[15] A study found that mice exposed to diacetyl for one hour daily over five days exhibited abnormal lung function and impaired airway repair when subsequently infected with influenza, suggesting heightened susceptibility to respiratory infections in exposed populations.[9]

Recommended Intake
Regulatory bodies have not established a specific Acceptable Daily Intake (ADI) for diacetyl.[6] The U.S. Food and Drug Administration (FDA) has designated diacetyl as "Generally Recognized As Safe" (GRAS) for consumption in food products, implying that its presence at low levels in foods is considered safe.[14] However, this designation does not account for inhalation exposure, which has been associated with respiratory health risks in occupational settings.[16] The National Institute for Occupational Safety and Health (NIOSH) recommends that workplace exposure to diacetyl be limited to 5 parts per billion (ppb) as an 8-hour time-weighted average (TWA) to minimize respiratory health risks.[14]

General Safety Level
Diacetyl is widely used as a flavoring agent in the food industry and is generally recognized as safe for consumption. However, studies have shown that inhalation of diacetyl vapors can cause respiratory tract irritation and damage to airway epithelial cells.[9]
Sensitive Individuals
Individuals with pre-existing respiratory conditions or heightened sensitivity may experience exacerbated symptoms upon inhalation exposure to diacetyl. Research indicates that such exposure can lead to significant airway obstruction and decreased lung function in susceptible populations.[17]

FAQ

Is diacetyl in food safe?

Diacetyl is generally recognized as safe for consumption in food, but inhaling it in large amounts, such as in industrial settings, may pose health risks.

What is diacetyl butter flavoring?

Diacetyl is a naturally occurring compound that gives butter its rich flavor and is also used as an artificial butter flavoring in processed foods.

What are the health risks of diacetyl?

Inhalation of diacetyl, especially in high concentrations in industrial settings, has been linked to respiratory conditions such as 'popcorn lung' (bronchiolitis obliterans).

References

  1. US Food and Drug Administration FDA n.d. Code of Federal Regulations Title 21: Diacetyl Available at: https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-184/subpart-B/section-184.1278 ↩︎
  2. European Food Safety Authority 2013 Evaluation of a scientific publication associating diacetyl with enhancement of u03b2-amyloid-induced neurotoxicity EFSA Journal 11(11) 3474 Available at: https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2013.3474 ↩︎
  3. Health Canada 2023 Risks of Vaping Available at: https://www.canada.ca/en/health-canada/services/smoking-tobacco/vaping/risks.html ↩︎
  4. World Health Organization 2019 Diacetyl Available at: https://apps.who.int/food-additives-contaminants-jecfa-database/Home/Chemical/4329 ↩︎
  5. Environmental Working Group n.d. Diacetyl Available at: https://www.ewg.org/foodscores/ingredients/8659-Diacetyl/ ↩︎
  6. National Institute for Occupational Safety and Health NIOSH 2016 Criteria for a Recommended Standard Occupational Exposure to Diacetyl and 2,3-Pentanedione Centers for Disease Control and Prevention Available at: https://www.cdc.gov/niosh/docs/2016-111/pdfs/2016-111-all.pdf ↩︎
  7. Allen JG et al. 2015 Flavoring Chemicals in E-Cigarettes Diacetyl 2,3-Pentanedione and Acetoin in a Sample of 51 Products Environmental Health Perspectives 124(6) 733-730 Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC4892929/ ↩︎
  8. Kreiss K et al. 2002 Clinical Bronchiolitis Obliterans in Workers at a Microwave-Popcorn Plant New England Journal of Medicine 347(5) 330-8 Available at: https://www.nejm.org/doi/full/10.1056/NEJMoa020300 ↩︎
  9. Hubbs AF et al. 2008 Respiratory toxicologic pathology of inhaled diacetyl in sprague-dawley rats Toxicologic Pathology 36(2) 330-44 Available at: https://pubmed.ncbi.nlm.nih.gov/18474946/ ↩︎
  10. Choudhury SR 2020 Food Derivative Neurotoxins A Silent Killer of our Well-Being International Journal of Science and Research IJSR 10(6) 1021-1024 Available at: https://www.ijsr.net/archive/v10i6/SR21615122510.pdf ↩︎
  11. White AV et al. 2021 Risk assessment of inhaled diacetyl from electronic cigarette use among teens and adults Science of the Total Environment 772 145486 Available at: https://pubmed.ncbi.nlm.nih.gov/33770882/ ↩︎
  12. Brass DM Palmer SM 2018 Models of Toxicity of Diacetyl and Alternative Diones Toxicology 388 15-20 Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC5540796/ ↩︎
  13. National Center for Biotechnology Information NCBI 2021 Diacetyl Hazardous Substances Data Bank Available at: https://www.ncbi.nlm.nih.gov/books/NBK507184/ ↩︎
  14. Centers for Disease Control and Prevention CDC 2024 About Flavoring-related Lung Disease National Institute for Occupational Safety and Health Available at: https://www.cdc.gov/niosh/flavoring-related-lung-disease/about/index.html ↩︎
  15. McGraw MD 2023 Diacetyl Influenza Exposure and Lung Health University of Rochester Medical Center Available at: https://www.urmc.rochester.edu/MediaLibraries/URMCMedia/environmental-health-sciences-center/COEC/documents/Summary-of-Diacetyl-Research-080423.pdf ↩︎
  16. Occupational Safety and Health Administration OSHA 2010 Occupational Exposure to Flavoring Substances Health Effects and Hazard Control Available at: https://www.osha.gov/publications/shib10142010 ↩︎
  17. Lockey JE et al. 2009 Airway obstruction related to diacetyl exposure at microwave popcorn production facilities European Respiratory Journal 34(1) 63-71 Available at: https://pubmed.ncbi.nlm.nih.gov/19567602/ ↩︎

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