Diacetyl and Food Flavorings

Posted on by Lauralynn Taylor McKernan, ScD, CIH; Kevin Dunn, MSEE, CIH; Kathleen Kreiss, MD; David N. Weissman, MD

Worker pouring flavoring chemicalsCommercial flavorings used in the flavoring manufacturing and food production industries are often complex mixtures of flavoring chemicals, many of which are volatile, meaning that they evaporate into the air from their liquid or solid form. Diacetyl is a prominent chemical ingredient in butter flavorings and is a component of the vapors coming from these and other flavorings. Inhalation of butter flavoring chemical mixtures, including diacetyl, has been associated with severe obstructive lung disease popularly know as “popcorn lung.” In many symptomatic individuals exposed to flavoring who have undergone lung biopsy, an irreversible type of lung damage called constrictive bronchiolitis has been found. In this condition, the smallest airways carrying air through the lungs, the bronchioles, are scarred and constricted. This can decrease or block air movement through these airways.

The November issue of Journal of Occupational and Environmental Hygiene contains two National Institute for Occupational Safety and Health (NIOSH)-authored articles related to current issues in diacetyl and food flavorings. “Field Evaluation of Diacetyl Sampling and Analytical Methods” (Volume 5 (11), D11-D16, 2008) reports on problems with NIOSH Manual of Analytical Methods (NMAM) Method 2557, used to monitor diacetyl in the workplace. The second article is “Engineering Case Reports: Evaluation of a Local Exhaust Ventilation System for Controlling Exposures During Liquid Flavoring Production” (Volume 5 (11), D103-D110, 2008). (Abstracts are available on the NIOSH website.)

Accurate measurement of diacetyl exposures is likely to be helpful in preventing flavorings-related lung disease. Even though flavorings exposures often involve multiple chemicals, diacetyl may serve as a marker or surrogate for mixed exposures to some hazardous flavorings, as it has been an ingredient in butter flavorings mixtures where disease has been observed. In addition, laboratory studies document that diacetyl has toxic properties as a single component that parallel the effects of exposure to a butter flavoring mixture. Thus, measuring diacetyl exposures identifies hazards. Furthermore, these measurements can guide corrective actions, such as engineering controls, improved work practices, and respiratory protection, to reduce or eliminate exposures.

NIOSH researchers developed and published an analytical method (NMAM 2557) to measure diacetyl in the workplace. Recent investigations indicate this method is adversely affected by humidity, resulting in an underestimation of true concentrations. A NIOSH project is underway to investigate these factors and determine the extent of this phenomenon. The first journal article presents the results from a field comparison between new and previously-existing exposure assessment methods for diacetyl. Side-by-side field samples were collected and analyzed according to NMAM 2557, OSHA method PV 2118, and a modified version of the OSHA method in flavoring manufacturing facilities. The results of the field work confirm the tendency of the NIOSH method to underestimate the true concentration of diacetyl. It is recommended that NMAM 2557 not be used to determine the concentration of airborne diacetyl. Until a new method is developed, NIOSH investigators currently utilize the modified OSHA method. It differs from OSHA method PV 2118 by using larger sample tubes (two 400/200 mg silica gel tubes in series) for sample collection. NIOSH investigators also measure temperature and relative humidity during investigations or research studies.

The second article describes an evaluation of new NIOSH-recommended ventilation controls for weighing and pouring flavoring chemicals on the bench top and mixing large-scale batches of flavorings in mixing tanks. NIOSH found that simple exhaust hoods based on existing designs can dramatically reduce worker exposure during the use and mixing of flavoring chemicals. The implementation of ventilated booths in the liquid production room provides a good engineering control that can be used for a variety of tasks, including large tank ventilation. Other operations such as packaging of powder flavorings and pouring of diacetyl and other high priority chemicals can be more safely completed in these booths. Proper training of employees and evaluation of the control during use is critical to ensure that the controls are operating effectively and that workers are being protected. Using these simple engineering controls can markedly decrease exposure to diacetyl and butter flavorings and hopefully reduce the risk of flavorings-related lung disease. Using them can also decrease exposures to the thousands of flavoring chemicals that have not been studied for toxicity after inhalation and do not have occupational exposure limits.

NIOSH is continuing to evaluate new information pertaining to the risk of respiratory disease from occupational exposures to flavorings. Several efforts are underway to investigate exposures, improve sampling methods, evaluate engineering controls, use animal toxicology models to study a range of flavorings and determine how lung injury occurs, disseminate important public health information, and determine appropriate steps to help safeguard workers’ health. More information can be found on the NIOSH Flavorings-related Lung Disease topic page.

As we move forward with this research we would like your input on the following questions:

  • What are the logistical sampling differences between the NIOSH and OSHA methods for diacetyl?
  • What is on the horizon for diacetyl and food flavoring sampling?
  • What are some general steps that can be taken to reduce exposure to workers handling diacetyl and other flavoring chemicals?
  • What sources of information are available on controlling exposure while working with diacetyl and other flavoring chemicals?

—Lauralynn Taylor McKernan ScD CIH; Kevin Dunn MSEE CIH; Kathleen Kreiss MD; David N. Weissman MD

Dr. McKernan is a research industrial hygienist in the NIOSH Education and Information Division. Mr. Dunn is a mechanical engineer in the NIOSH Division of Applied Research and Technology. Dr. Kreiss is the Chief of the Field Studies Branch within the NIOSH Division of Respiratory Disease Studies. Dr. Weissman is the Director of the NIOSH Division of Respiratory Disease Studies.

Posted 11/10/08 at 9:23 am

Posted on by Lauralynn Taylor McKernan, ScD, CIH; Kevin Dunn, MSEE, CIH; Kathleen Kreiss, MD; David N. Weissman, MD

35 comments on “Diacetyl and Food Flavorings”

Comments listed below are posted by individuals not associated with CDC, unless otherwise stated. These comments do not represent the official views of CDC, and CDC does not guarantee that any information posted by individuals on this site is correct, and disclaims any liability for any loss or damage resulting from reliance on any such information. Read more about our comment policy ».

    This is interesting and frightening. How safe are we as consumers of this product? What are the synergistic effects of this and other chemicals in our foods? Maybe we need to forgo the easy microwave method and go back to using a stove, a pan with a lid and real butter. But . . . is the butter safe?

    NIOSH studies occupational settings and makes recommendations to reduce worker exposures. Even if substances are safe to eat—”generally recognized as safe” as determined by the Food and Drug Administration—they may still be harmful to breathe in the forms and amounts to which food and chemical industry workers may be exposed. How much exposure that people have to diacetyl and other inhaled flavoring chemicals is an important determinant of risk for lung disease. Workers often have different exposure characteristics, including level of exposure, to flavorings than typical consumers.

    Unlike workers, so far there have not been peer-reviewed scientific studies showing that consumers using products such as microwave popcorn that contain butter flavoring chemicals are at increased risk for lung disease. Nor is there any evidence that cooking with butter is associated with increased risk for lung disease. Individual cases in consumers are difficult to evaluate for cause, since microwave popcorn consumption is very common. To address the question of whether microwave popcorn consumption is a risk to consumers would require comparing large numbers of cases of obstructive lung disease to controls without such disease to see if the two groups differed in their popping of microwave popcorn or other types of butter flavoring usage.

    Currently, even though there is little to suggest significant risk to normal consumers, a sensible precautionary approach is appropriate. Consumers could take simple precautions to minimize the amount of diacetyl and other chemicals that they breathe. Cooking or popping of products containing diacetyl and other butter flavoring chemicals should be done in a food preparation area with adequate exhaust ventilation. Good ventilation will help to dilute and remove vapors. In the case of microwave popcorn, the popped bags should be allowed to cool before they are opened, which will also decrease exposure to vapors. A very helpful guidance document for cooks has been developed by the Washington State Department of Labor and Industries, Safety & Health Assessment & Research for Prevention (SHARP) Program. It contains a number of useful recommendations and can be found on the internet at the following address: http://www.lni.wa.gov/Safety/REsearch/Files/DiacetylFactSheet.pdf.

    You also asked about the possibility of synergism between diacetyl and other flavorings. This is an important question. Flavoring mixtures are often complex and contain both natural and manmade substances. Much remains to be learned about the potential health effects of the individual component materials and how they interact when combined.

    OSHA is looking for comments on a proposed rule regarding Diacetyl. See below for details:


    Occupational Safety and Health Administration

    29 CFR Part 1910

    [Docket No. OSHA-2008-0046]

    RIN 1218-AC33

    Occupational Exposure to Diacetyl and Food Flavorings Containing Diacetyl

    AGENCY: Occupational Safety and Health Administration (OSHA), Department of Labor.

    ACTION: Advance notice of proposed rulemaking.

    SUMMARY: OSHA is requesting data, information, and comment on issues related to occupational exposure to diacetyl and food flavorings containing diacetyl, including current employee exposures to diacetyl; the relationship between exposure to diacetyl and the development of adverse health effects; exposure assessment and monitoring methods; exposure control methods; employee training; medical surveillance for adverse health effects related to diacetyl exposure; and other pertinent subjects.

    In this notice, OSHA intends the term “diacetyl and food flavorings containing diacetyl” to encompass other constituents of food flavorings containing diacetyl. In addition to information on diacetyl, OSHA seeks information on acetoin, acetaldehyde, acetic acid, furfural, and other compounds present in food flavorings that may cause or contribute to flavoring-related lung disease. The Agency is also interested in and seeks information about diacetyl present in substances other than food flavorings (e.g., naturally occurring diacetyl or diacetyl in fragrances) as well as substitutes used in place of diacetyl (e.g., diacetyl trimer).

    The information received in response to this document will assist the Agency in developing a proposed standard addressing occupational exposure to diacetyl and food flavorings containing diacetyl.

    DATES: Comments must be submitted (postmarked, sent, or received) by April 21, 2009.

    Several operations that I have been asked to evaluate involve diacetyl as an ingredient in powder material. The current sampling method only accounts for the vapor phase. Have any of the health studies looked at the effects from exposure to aerosols containing diacetyl/flavorings? Is exposure to these aersols a concern? Is a sampling and analytical method available to monitor exposure to diacetyl in powder?

    Although consumers are less likely to inhale levels of diacetyl in quantities high enough to cause lung damage, last year, one such case was reported in a Denver, CO, man. The man was said to have had a two-bag-a-day popcorn habit.

    As explained in a USA Today article ([http://www.usatoday.com/money/industries/food/2008-01-16-popcorn-lung-suit_N.htm]), doctors at National Jewish Hospital diagnosed the individual with bronchiolitis obliterans (commonly referred to as “popcorn lung disease”), a rare lung disease that is linked to the flavor chemical diacetyl.

    I am a graduate student from the University of Miami in an Environmental Health Course. I find these studies of diacetyl and health risks shocking, and question if this is only the tip of the iceberg. After doing a bit of brief research, I found that diacetyl is used in almost all cooking oils, butter substitutes, and sprays (excluding salted butter); diacetyl is being used as both a flavor additive and a preservative. Shouldn’t consumers be aware of this potential health risk? For instance, I use butters and oils almost every day in my cooking, and now I am a bit concerned. Are there measures being undertaken that require manufacturers to label their products that contain diacetyl? Also, it seems today’s common food is full of preservatives and flavor additives to prolong shelf-life; so how many other preservatives could there be that have similar effects? Do flavor additives/preservatives have to go through testing before they are added to our food and mass produced/distributed?

    If not, is it logical to assume we may be facing an enormous public health crisis because of these effects in the future?

    In response to your questions:

    Should consumers be concerned?

    This issue has already been touched on in response #1. Since NIOSH only does occupational research, it has not done work in this area.

    Are measures being taken to require manufacturers to label products containing diacetyl?

    NIOSH studies occupational settings and is not involved in labeling of food products for consumers, which is within the jurisdiction of the Food and Drug Administration (FDA). In occupational settings, the Occupational Safety and Health Adminstration (OSHA) requires that Material Safety Data Sheets (MSDS) be made available to workers using potentially hazardous substances at work. OSHA has provided guidance for content in MSDS addressing diacetyl and food products containing diacetyl.

    Can/do other preservatives have similar effects?

    As noted in the NIOSH Alert, Preventing Lung Disease in Workers Who Use or Make Flavorings, the flavorings industry has estimated that over a thousand flavoring ingredients have the potential to be respiratory hazards due to possible volatility and irritant properties (alpha, beta-unsaturated aldehydes and ketones, aliphatic aldehydes, aliphatic carboxylic acids, aliphatic amines, and aliphatic aromatic thiols and sulfides). That being said, we do not yet know whether other flavoring chemicals are able to cause bronchiolitis obliterans in people. However, a recent study in animals suggests that combined exposure to another flavoring agent, butyric acid, might slightly increase the penetration of diacetyl into the lung.

    Are flavor additives/preservatives tested before they are added to our food?

    NIOSH is not involved in food or food additive safety issues. That is the responsibility of FDA.

    The Department of Labor (OSHA) is withholding rulemaking on diacetyl and convening a Small Business Advocacy Review Panel. Details below:


    Occupational Safety and Health Administration

    29 CFR Part 1910

    [Docket No. OSHA-2008-0046]

    RIN 1218-AC33

    Occupational Exposure to Diacetyl and Food Flavorings Containing Diacetyl

    AGENCY: Occupational Safety and Health Administration (OSHA), Department of Labor.

    ACTION: Advance Notice of Proposed Rulemaking; withdrawal.

    SUMMARY: OSHA is withdrawing its Advance Notice of Proposed Rulemaking (ANPRM) on Occupational Exposure to Diacetyl and Food Flavorings Containing Diacetyl in order to facilitate convening a Small Business Advocacy Review Panel, pursuant to the Small Business Regulatory Enforcement Fairness Act (SBREFA). Materials submitted prior to this withdrawal as well as any other information submitted directly to OSHA after the withdrawal will be put in the public rulemaking docket and receive equal consideration as a part of the rulemaking record. In addition, there will be several other opportunities for stakeholders to provide information and comment during the rulemaking process.

    DATES: The ANPRM on Occupational Exposure to Diacetyl and Food Flavorings Containing Diacetyl, published January 21, 2009 (74 FR 3938), is withdrawn, effective March 17, 2009.

    Has diacetyl been found in any food flavoring involving the milk product industry, such as yogurt/flavorings? Most of the information I have read concerns popcorn manufacturing.

    Diacetyl occurs naturally in a variety of dairy products including cottage cheese, buttermilk, butter, sour cream, yogurt, and some cheeses/fermented milks. Diacetyl may also be added to other dairy products including those listed above as well as butter substitutes and processed cheese/dips. While diacetyl and other flavoring chemicals have been evaluated in the microwave popcorn and flavor manufacturing industry, less is known about the potential for exposure in other food production. NIOSH is recruiting companies in the food manufacturing industry for participation in a study to assess worker exposures to diacetyl among a range of food manufacturers, including dairy. The purpose of the study is to characterize workplace exposures to diacetyl and other flavoring chemicals and to evaluate the use and effectiveness of engineering controls in food production facilities.

    Thank you for this very informative article of yours. You have explained everything well. I appreciate that you shared this to us. I just wonder what are other side effect that will bring this chemicals to our health.

    No wonder why people only live at the age 70 below because of the food we take.

    To our knowledge, there is not an upper limit on diacetyl content in food products. Recipe formulations have changed throughout the years, depending upon desired taste in industry. Higher diacetyl content in products may lead to higher exposures, and thus greater risk to workers. However NIOSH has observed significant airborne diacetyl concentrations with flavoring formulations containing low diacetyl content. Regardless of the level of diacetyl content in the product, appropriate worker protection based on airborne levels should include engineering controls, respiratory protection, and appropriate work practices that reduce potential exposure.

    Now that diacetyl is linked to alzheimers disease it is time to take action to identify the products that diacetyl is in. The consumer needs to know when they buy a product whether or not it contains this dangerous ingredient.

    Thank you for your comment. We agree that people should be able to find out what ingredients are present in the products that they use. With regard to diacetyl and Alzheimer’s Disease, a newly published experimental study performed in cell culture found that diacetyl binds to beta-amyloid and accelerates its aggregation. (More et al. The Butter Flavorant, Diacetyl, Exacerbates β-Amyloid Cytotoxicity. Chem Res Toxicol. 2012 Jul 6. [Epub ahead of print]). Aggregation of beta-amyloid is one of the major pathologies of Alzheimer’s Disease. However, this study did not examine if diacetyl exposure has this effect in people or if people exposed to diacetyl have an increased risk for developing Alzheimer’s Disease.

    This is scary and information which the public should be aware of. We are all wondering why Alzheimer’s is increasing and yet the study mentioned identifies that this chemical inreases beta-amyloid which binds to the brain. This disease is growing in extraordinary numbers, affecting all families. Why is this chemical not identified as part of a product’s labeling? Better it, it should be banned immediately, if there is some connection at the cellular level. What can we as consumers do?

    Thank you for your comment. Alzheimer’s Disease is one of the most important public health issues in America today. Little could be more important than finding ways to prevent it. Although the paper by More et al raises concerns about interactions between diacetyl and beta-amyloid in a tissue culture system, it does not examine if similar effects occur in living animals or in people. It does not examine if people exposed to diacetyl are at increased risk for Alzheimer’s Disease. Thus, it would be premature to make public health policy intended to prevent Alzheimer’s Disease based on this report alone. NIOSH does not have any authority over consumer products. However, we believe that people should be able to know what ingredients are in the products that they use. As a consumer wishing to know the ingredients in the products that you use, we suggest that you carefully read product labels. If ingredients described as “natural flavor” or “artificial flavor” are listed, you would need to contact the manufacturer to find out if diacetyl is part of the added flavor.

    Can you please provide an update on the status of the criteria document? Does NIOSH have the criteria necessary to establish a REL for diacetyl and 2,3 pentandione? FEMA issued a new document, but the data is not substantially different than that provided in the 2011 draft criteria doc NIOSH submitted for comment.

    Thank you for your blog inquiry regarding the draft diacetyl /2,3-pentanedione criteria document. Yes, NIOSH believes that we have sufficient information to propose an REL. The team published its draft criteria document for public and peer review comment in August 2011, posted here: http://www.cdc.gov/niosh/docket/archive/pdfs/NIOSH-245/0245-081211-draftdocument.pdf . Within the draft document, NIOSH proposed a Recommended Exposure Limit (REL) that exposure to diacetyl be kept below a concentration of 5 parts per billion (ppb) as a time-weighted average (TWA) during a 40-hour work week. NIOSH also recommended a short-term exposure limit (STEL) for diacetyl of 25 ppb for a 15-minute time period. The draft criteria document also covered 2,3-pentanedione and recommended a REL that exposure to 2,3-pentanedione be kept below a concentration of 9.3 ppb in a TWA during a 40-hour work week. NIOSH also recommended a STEL for 2,3-pentanedione of 31 ppb during a 15-minute period.

    NIOSH held a public meeting on the draft diacetyl /2,3-pentanedione criteria document on August 26, 2011. A transcript of the meeting can be found here: http://www.cdc.gov/niosh/docket/archive/pdfs/NIOSH-245/0245-082611-Transcript.pdf Public comments submitted to the NIOSH docket can be found here: http://www.cdc.gov/niosh/docket/archive/docket245.html . After the meeting, the peer review period continued until May 2012. The diacetyl /2,3-pentanedione criteria document team is currently responding to both peer and public comments on the draft document. We plan to post all public and peer comments and subsequent responses in a response document when the final document is published. We anticipate publishing the document in calendar year 2013. The draft diacetyl /2,3-pentanedione criteria document has been referenced in several publications, including a recent Flavor and Extract Manufacturers Association (FEMA) publication on Respiratory Health and Safety in Flavor Manufacturing Workplace. The NIOSH flavoring website is updated frequently and might also be of interest to you: http://www.cdc.gov/niosh/topics/flavorings/

    Do you have an anticipated time line for comment reviews and responses to the Criteria Document that were submitted to the Federal Register in Feb 2014? Also do you anticipate a control banding approach for chemicals similar to diacetyl/2,3 pentanedione once REL(s) have been issued?

    Thank you for your response. As reflected in the Federal Register notice, NIOSH recently posted Chapter 6 and a subsection of Chapter 8 for public comment and peer review. The authors or the document are carefully considering these comments. As you may know, the rest of the criteria document was previously posted for public comment and peer review in 2011-12. NIOSH plans to publish a final criteria document this calendar year. This document will be responsive to the peer review and public comments that we received. A listing of how each of the comments was handled by NIOSH will be posted to and included in the NIOSH docket.

    NIOSH recognizes that chemicals are being introduced at a rate that outpaces current OEL development. Once finalized, the proposed NIOSH occupational exposure banding process will be useful for dealing with the myriad of unregulated chemicals in commerce. At this time, NIOSH is has not identified any specific chemicals to formally band.

    NIOSH published a draft criteria document which included an overview of the scientific literature pertaining to diacetyl and 2,3-pentanedione in August 2011. It also contains a draft Recommended Exposure Limit (REL) based upon a quantitative risk assessment. The draft criteria document can be found here: http://www.cdc.gov/niosh/docket/archive/pdfs/NIOSH-245/0245-081211-draftdocument.pdf

    NIOSH held a public meeting in August 2011, accepted comments from stakeholders on this draft document through November 2011, and peer review comments through May 2012. A transcript of the public meeting and all stakeholder comments received is posted on our docket website at: http://www.cdc.gov/niosh/docket/archive/docket245.html . NIOSH has carefully considered the peer and stakeholder comments to revise the document. We plan to publish the final document in 2015.

    NIOSH also recently released a new best practices document that outlines practical measures employers and workers can take to minimize risks associated with exposure to diacetyl. “Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3 Pentanedione” is currently available at: http://www.cdc.gov/niosh/docs/2015-197/pdfs/2015-197.pdf

    NIOSH has been investigating the use of a canister-based sampling and analysis for measuring diacetyl, 2,3-pentanedione, and 2,3-hexanedione in air. Also, a modified OSHA method 1016 is being investigated to improve detection limits by replacing flame ionization detection with mass spectrometric detection negating the need to derivatize.

    Thank you for your comment. The presence of flavoring chemicals such as diacetyl in e-cigarettes is an important health concern and discussed in recent publications from the American Industrial Hygiene Association https://www.aiha.org/about-aiha/Press/2014PressRelease/Pages/AIHA-Cautions-Against-Indoor-Use-of–Electronic-Cigarettes-.aspx and NIOSH http://www.cdc.gov/niosh/docs/2015-113/. You may also be interested in materials from a recent workshop sponsored by the U.S. Food and Drug Administration http://www.fda.gov/TobaccoProducts/NewsEvents/ucm428317.htm.

    Since it has been almost a year since I last asked, what is the status of the proposed RELs for Diacetyl and Acetyl propionyl? Is it unusual for this take this long to establish a REL or is it within the normal timeframe. Finally, have there been any advances in sampling methodology, specifically for powdered materials that have these compounds associated with them?

    The National Institute for Occupational Safety and Health (NIOSH) has released formal recommendations for controlling workplace exposures to diacetyl and 2,3-pentanedione, widely-used food flavoring compounds that have been associated with decreased lung function in exposed workers. The recommended exposure limits (RELs) were published in October 2016 in the NIOSH Criteria for a Recommended Standard: Occupational Exposure to Diacetyl and 2,3-Pentanedione. The entire document can be seen here: https://www.cdc.gov/niosh/docs/2016-111/default.html The development of the NIOSH assessment, including the proposed REL, followed a standardized and documented process, including carefully considering stakeholder input as well as rigorous peer reviews, in its evaluation of the scientific evidence. These are critical steps to ensure that we are providing the best possible guidance we can to minimize the risks of exposures for workers.

    A sampling and analytical method is being developed by NIOSH for the quantitative measurement of diacetyl, 2,3-pentanedione, and potentially other flavoring compounds in dust. A sampling cassette with a filter is used to collect airborne dust. The filter is then extracted in water and the aqueous solution is heated to promote the transfer of volatile components to the headspace above the solution. More information can be obtained from Dr. Robert Streicher at RStreicher@cdc.gov.

    The e-liquid industry are aware of Diacetyl in flavourings and have taken steps to ensure that the liquids do not contain Diacetyl.

    Thanks for sharing such a valuable information about flavors in which chemicals are involved. I got deeply concerned about harms of such toxic flavoring agents. We should use secure flavoring agents as substitute of diacetyl and such other chemicals.

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