Controlling Diacetyl Exposures

An estimated 1,000-plus flavoring ingredients are potential respiratory hazards. This was the predominant VOC identified in NIOSH's studies.

On Sept. 24, 2007, OSHA issued a Safety and Health Information Bulletin, Respiratory Disease Among Employees in Microwave Popcorn Processing Plants. The purpose was to inform employees and employers about the potential hazards of food flavorings containing diacetyl, recommend exposure controls to reduce exposures to food flavorings containing diacetyl, and inform employers of applicable mandatory OSHA standards. OSHA has subsequently released a Guidance Document, Hazard Communication Guidance for Diacetyl and Food Flavorings Containing Diacetyl. The purpose of the Guidance Document is to alert employers, chemical manufacturers, and importers of their responsibilities relative to diacetyl and 29 CFR 1910.1200 Hazard Communication.

In 2002, NIOSH conducted an investigation in a microwave popcorn processing facility where eight workers were diagnosed with fixed obstructive lung disease. All eight workers had respiratory illnesses resembling a rare lung disease, bronchiolitis obliterans, which does not respond to treatment. The severity of symptoms can range from a mild to severe cough and shortness of breath on exertion.Symptoms do not improve when removed from the workplace exposure.

The workers who had respiratory symptoms had worked in the mixing room and on the production line. Some of the affected workers have developed a disabling lung disease and were recommended for a lung transplant. Bronchiolitis obliterans is currently the most severe adverse health effect resulting from airborne exposure to diacetyl and food flavorings containing diacetyl.

NIOSH investigated five other microwave popcorn plants and found that workers exposed to butter flavorings had similar disease symptoms.

Flavorings are complex mixtures of natural and man-made chemicals. The Food and Drug Administration (FDA) evaluates flavoring ingredients to determine whether they are “generally recognized as safe to be eaten. ”No consideration is given to airborne exposure hazards.

Diacetyl (CAS# 431-03-08) is a natural byproduct of fermentation and can be synthesized by chemical manufacturers. It gives food flavorings a “buttery flavor and aroma.” Diacetyl is only one of thousands of flavoring compounds; it has been used as a “marker” chemical in the NIOSH studies to determine airborne concentration of flavorings and risk of symptoms developing in exposed workers. That is, diacetyl was the most predominant volatile organic compound (VOC) identified in the NIOSH studies, and analytical results demonstrated a strong statistical relationship between diacetyl exposure and development of airway symptoms. The NIOSH Alert Document “Preventing Lung Disease in Workers Who Use or Make Flavorings” states in the Conclusion section on page 5:

“Case clusters of fixed obstructive lung disease, one with biopsy evidence of bronchiolitis obliterans, have been documented among workers at several different plants where flavorings are used, or where chemicals are handled, in the production of flavorings. Recent attention has been largely focused on workers exposed to volatile chemicals in butter flavorings at microwave popcorn plants, but other reports indicate that other flavorings, and food manufacturing workers exposed to various flavorings, may also be at risk.

“Little is currently known about which chemicals used in flavorings have the potential to cause lung disease and other health effects, or what workplace exposure concentrations are safe. As part of ongoing investigations into airways disease in microwave popcorn workers, NIOSH has recently undertaken animal experiments to evaluate individual butter flavoring chemicals. Results of an animal study indicate that exposure to vapors from diacetyl, a chemical used to impart butter-like flavor, causes airway injury, though perhaps to a smaller extent than caused by exposure to vapors from the intact butter flavoring mixture itself.

“Most chemicals used in flavorings have not been tested for respiratory toxicity via the inhalation route, and occupational exposure limits have been established for only a relatively small number of these chemicals. Although much remains unknown regarding the toxicity of flavoring- related chemicals, employers and workers can take steps to address working conditions and work practices that place workers at risk.”

Therefore, the exact causative agent of lung disease from airborne exposure to food flavorings remains unknown until further research can demonstrate conclusive findings. The flavorings industry estimates that there are more than 1,000 flavoring ingredients that are potential respiratory hazards.

OSHA Compliance
. Manufacturers and importers of flavorings must include the most recent toxicology information on their Material Safety Data Sheets (MSDSs) to provide information to employers and employees of the hazards of flavorings containing at least 1 percent diacetyl. Currently, many MSDSs do not contain up-to-date toxicological information regarding the severe respiratory hazards, indicating only the irritation effects to the eyes, respiratory tract, and skin. This information must be on the most current MSDS.

MSDSs must contain wording that includes “animals exposed to diacetyl experienced damage to the nose and upper airways, including severe damage to cells lining the respiratory tract. NIOSH has reported that employees exposed to butter flavorings containing diacetyl are at risk of developing occupational lung disease, and that in one instance similar illnesses have been found among employees producing butter and vanilla flavorings containing diacetyl. Contact with liquid or vapors can cause irritation to the eyes, skin, nose, and throat.”

The MSDS also must contain information stating that diacetyl is a “Flammable Liquid.”

Employers must contact the flavorings manufacturer and request the most current MSDS for use in their Hazard Communication Programs.

Labeling. Manufacturers and importers also must label their products with appropriate warning labels if the product contains at least 1 percent diacetyl. Suggested warning labels for diacetyl and food flavorings containing at least one percent diacetyl are shown below:

Engineering Controls. NIOSH has determined that effective control measures to reduce worker exposure include enclosures, general dilution, and local exhaust ventilation.

PPE. Personal Protective Equipment (PPE) can include an air-purifying respirator equipped with an organic vapor cartridge in combination with particulate filters (to provide minimum protection). Any supplied air respirator also can be used. Powered air purifying respirators with organic vapor cartridges and particulate filters also will provide minimum protection. The selection of an appropriate respirator depends on the worker’s exposure. A complete respiratory protection plan also must be implemented to comply with 29 CFR 1910.134,Respiratory Protection.

Gloves and aprons made from butyl rubber, Teflon™, or Tychem™ are effective in reducing skin contact with ketones (diacetyl). Chemical goggles also must be worn when handling liquid diacetyl or liquid flavorings. The facility PPE Hazard Assessment (29 CFR 1910.132) should include the required PPE for diacetyl exposures.

Training and Information. Employers are required to train employees in the methods used to detect the presence or release of diacetyl, the physical and health hazards of diacetyl, and control measures (including work practices, emergency procedures, PPE, and engineering controls) used to reduce potential exposure.

No Established PEL. Currently, no established occupational exposure limit exists for diacetyl. NIOSH recommends that exposure levels be limited to as low as reasonably achievable. NIOSH also recommends using substitution, engineering controls, administrative controls, PPE, worker education, and worker health monitoring.

Air Monitoring for Diacetyl. Collecting personal or area air samples includes using two silica gel tubes in series. The analytical method is OSHA PV2118.Measuring worker exposure can aid in determining whether engineering controls are effective in reducing exposures to as low as reasonably achievable.

On Sept. 26, 2007, the U.S.House of Representatives passed “The Popcorn Workers Lung Disease Prevention Act,” H.R. 2693. This legislation would require OSHA to issue an interim standard to protect workers from diacetyl and set a permanent standard within two years. To date, OSHA has issued a Safety and Health Information Bulletin, Respiratory Disease Among Employees in Microwave Popcorn Processing Plants and a Guidance Document, Hazard Communication Guidance For Diacetyl And Food Flavorings Containing Diacetyl. NIOSH is conducting ongoing research into diacetyl and food flavorings exposures and lung disease.

Employers are urged to identify potential exposures to diacetyl and food flavorings containing diacetyl (and vanilla) and implement measures to reduce workplace exposures to as low as reasonably achievable.

1. Fixed Obstructive Lung Disease in Workers at a Microwave Popcorn Factory—Missouri, 2000—2002, MMWR April 26, 2002, 51(16): 345-7, www.cdc .gov/mmwr/preview/mmwrhtml/mm5116a2.htm
2. Flavorings-Related Lung Disease, niosh/topics/flavorings
3. Hazard Communication Guidance for Diacetyl and Food Flavorings Containing Diacetyl, www
4. House Passes Diacetyl legislation, www.defending Legislation.cfm
5. Preventing Lung Disease in Workers Who Use or Make Flavorings, NIOSH Alert, NIOSH Publication No. 2004-110
6. Report on Severe Fixed Obstructive Lung Disease in Workers at a Flavoring Manufacturing Plant. R. Kanwal, M.D., MPH, G. Kullman, Ph.D., M.D. Department of Health and Human Services, Centers for Disease Control and Prevention, Health Hazard Evaluation Report, HETA 2006-0303-3043
7. Respiratory Disease Among Employees in Microwave Popcorn Processing Plants,

This article originally appeared in the September 2008 issue of Occupational Health & Safety.

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