Agent Name
CAS Number
Major Category
Other Classes
Diacetyl formula graphical representation
2,3-Butadione; 2,3-Butanedione; 2,3-Diketobutane; 2,3-Dioxobutane; Biacetyl; Butadione; Butanedione; Diacetyl (natural); Dimethyl diketone; Dimethyl glyoxal; Dimethylglyoxal; Glyoxal, dimethyl-; UN2346; [ChemIDplus] DA; [NIOSH]
Aliphatic Ketones, Other
Clear liquid with a chlorine-like odor; [CAMEO]
Used to carry aroma of butter and other food flavors; [Hawley] Diacetyl occurs naturally in butter, cheese, yogurt, milk, coffee, cocoa, honey, tobacco smoke, beer, wine, and a number of flowers and plant extracts; [ACGIH]
"Little is currently known about which chemicals used in flavorings have the potential to cause lung disease and other health effects, and 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 that caused by exposure to vapors from the intact butter flavoring mixture itself." [Reference #1] In the original 8 cases, there was no history of acute toxic exposure as is typical for other causes of bronchiolitis obliterans (BO). The disease developed over a longer period of time. [Reference #2] BO also reported in two flavor-manufacturing workers in California; [MMWR 2007 Apr 27;56(16): 389-93] "Exposure to high concentrations (>190 ppm) of diacetyl-containing butter flavor and to pure diacetyl resulted in necrosis of nasal and airway epithelium in rats exposed in a whole-body inhalation chamber for 6 hr. . . . Our data suggest that diacetyl levels in small- to medium-sized flavor manufacturing facilities are widely variable, ranging from the limit of detection (<0.01 ppm) to as high as 60 ppm, with a mean of 1.80 ppm and a median of 0.10 ppm. These ranges are lower than those reported in the microwave popcorn plant with the index cases of BO, where diacetyl levels ranged from less that 0.01 ppm to 98 ppm, with a mean of 8.1 ppm. [PMID 18720288] In 6-hour inhalation studies of rats, causes changes to trachea or bronchi at concentrations >294 ppm; In oral lethal-dose studies, causes ataxia and coma in guinea pigs and somnolence in rats; [RTECS] See "Airway obstruction related to diacetyl exposure at microwave popcorn production facilities." [PMID 19567602] TLV Basis = "lung damage (bronchiolitis obliterans-like illness)"; "Animal data suggest the respiratory tract is the primary target of diacetyl exposure, similar to humans, although, in rats this tends to be the upper airways rather than the lower airways (bronchioles). Adverse health effects also seem to occur at higher levels of exposure than in humans." Diacetyl has notations of DSEN and A3. [ACGIH] "DA exposures, often exceeding 1 ppm in the past, place workers at high risk of pulmonary impairment." [PMID 29443707] Danger of skin sensitization; [MAK] See "2,3-Pentanedione."
See Reference #2 for the OSHA National Emphasis Program--Microwave Popcorn Processing Plants.
Biomedical References

Exposure Assessment

Skin Designation (ACGIH)
Insufficient data
0.01 ppm
0.02 ppm
0.02 ppm
Vapor Pressure
56.8 mm Hg
Explanatory Notes
A highly flammable liquid that is soluble in water; b.p. = 88 degrees C; [CAMEO] mp = -2.4 degrees C; [ChemIDplus] VP from ChemIDplus;
may ignite at ambient temp

Adverse Effects

Skin Sensitizer
ACGIH Carcinogen
Confirmed Animal

Diseases, Processes, and Activities Linked to This Agent


Occupational diseases associated with exposure to this agent: