Sunday, November 06, 2005

Popcorn Workers Lung (III) - Toxicology - Don't Ask, Don't Tell, Don't Pursue

Laboratory toxicology is a special NIOSH asset. As the endemic of popcorn workers lung was identified, environmental sampling identified diacetyl [2,3-butanedione] as the most prominent exposure. The peak exposure ranged to 100 ppm, the high exposure grouped medianed about 20 ppm, the largest exposed group medianed in the single digits.

Toxlining diacetyl revealed virtually nothing before 2002; a few papers on diacetyloxime. Toxlining diacetyl still reveals nothing beyond this one day exposure study in rats. Diacetyl is used in products other than popcorn. The Dodger thinks the butter smell of microwave popcorn is diacetyl, as well as the aroma of "I can't believe it's not butter." Human exposure is widespread. Yet the published literature contains no 2 week, 13 week or chronic bioassay of this material.

Wouldn't it be nice to know something about lower dose toxicity, or even a NOEL for a single 6 hour exposure?

Does the 1,2-dione structure have some specific biological activity leading to tissue damage? Is it binding to the respriatory epithelium?

Inquiring minds want to know. Inquiring minds would also be interested in whether FDA is dead, comatose, anethatized or just asleep at the switch.

Toxicol Appl Pharmacol. 2002 Dec 1;185(2):128-35.

Necrosis of nasal and airway epithelium in rats inhaling vapors of artificial butter flavoring.

Hubbs AF, Battelli LA, Goldsmith WT, Porter DW, Frazer D, Friend S, Schwegler-Berry D, Mercer RR, Reynolds JS, Grote A, Castranova V, Kullman G, Fedan JS, Dowdy J, Jones WG. Health Effects Laboratory Division, National Institute for Occupational Safety and Health1, Centers for Disease Control and Prevention, 1095 Willowdale Road, Morgantown, West Virginia 26505, USA.

... Rats were exposed to vapors liberated from heated butter flavoring. Rats were exposed for 6 h by inhalation and were necropsied 1 day after exposure. The exposure was found by GC-MS analysis to be a complex mixture of various organic gases with the major peaks consisting of diacetyl (2,3-butanedione), acetic acid, acetoin (3-hydroxy-2-butanone), butyric acid, acetoin dimers, 2-nonanone, and delta-alkyl lactones. Diacetyl was used as a marker of exposure concentration. In the lung, butter flavoring vapors containing 285-371 ppm diacetyl caused multifocal, necrotizing bronchitis, which was most consistently present in the mainstem bronchus. Alveoli were unaffected. Butter flavoring vapors containing 203-371 ppm diacetyl caused necrosuppurative rhinitis, which affected all four levels of the nose. Within the posterior two nasal levels (T3 and T4), necrosis and inflammation was principally localized to the nasopharyngeal duct. Control rats were unaffected. Therefore, concentrations of butter flavoring vapors that can occur during the manufacture of foods are associated with epithelial injury in the nasal passages and pulmonary airways of rats.

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