Diacetyl and Food Flavorings

Commercial 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