Determining a safe exposure level for diacetyl-containing butter flavoring

Workers and consumers have been diagnosed with bronchiolitis obliterans and other respiratory illnesses caused by inhalation exposure to high and low levels of diacetyl. While diacetyl is a natural product of fermentation found in lower quantities in some dairy and alcohol products, artificial butter flavorings contain thousands of times more diacetyl than these natural products. Diacetyl vapors emitted from these flavorings have caused disease in workers and microwave popcorn consumers. Other volatile compounds in butter flavoring may potentiate diacetyl's effect on the lungs. The various testing methods used to measure diacetyl further complicate the matter of determining a TLV. The NIOSH 2557 testing method that was used to determine exposure levels for most of the worker studies has been found to be unreliable. Some testing was done with the Fourier transform infrared (FTIR) method. We have reviewed published and unpublished studies and case reports of workers and consumers who developed lung disease from diacetyl exposures and characterized cumulative chronic and peak diacetyl exposure levels that caused their disease to determine dangerous levels of exposure. FTIR measurements have been used to calculate chronic exposures below 2 ppb for 9 - 11 years (with no peaks) and peak exposures as low as 4-13 ppm that have been associated with disease. The proposed California OSHA standard does not regulate exposures to products with less than 1% diacetyl. 1% products may result in exposures as high as 65,000 ppm at room temperature. Companies have externalized costs onto exposed workers and consumers.