Nasal Injury in Rats Exposed to Diacetyl may be Predictive of Lung Injury in Humans

John B. Morris, Ph.D.
University of Connecticut
NIEHS Grant R01ES014041

Exposure to the butter flavor ingredients diacetyl and butyric acid has recently been found to cause a respiratory condition called bronchiolitis obliterans. The popular press has dubbed the condition "popcorn workers lung" because it is otherwise a rare condition but strikes workers in the popcorn industry at a much higher rate than the general population. The condition causes scarring of the lungs inhibiting normal respiration.

NIEHS supported scientists investigating the health effects of butyric acid and diacetyl have discovered that the severity of airway injuries in rats above the level of the lung are predictive of similar injuries in human lung tissue. The current results suggest that simultaneous exposure to butyric acid and diacetyl may increase the toxicity and potential lung injury caused by diacetyl. Butyric acid is a potent inhibitor of an enzyme, diacetyl reductase, that metabolizes diacetyl. These findings highlight the need to consider the multiple components of butter flavoring vapors in comprehensive risk assessments and safety evaluations.

Citation: Morris JB, Hubbs AF. Inhalation dosimetry of diacetyl and butyric acid, two components of butter flavoring vapors. Toxicol Sci. 2009 Mar;108(1):173-83.