Two unions−the International Brotherhood of Teamsters and United Food & Commercial Workers−last week petitioned the Occupational Safety & Health Administration, demanding an emergency temporary workplace standard for diacetyl, a flavoring agent. This chemical is used in artificial butter for microwave popcorn, dog food, and other foods. In several studies, diacetyl has been linked to bronchiolitis obliterans, an irreversible lung disease that has sickened and killed workers at factories that manufacture popcorn and flavorings. Scientists and occupational health experts have also sent letters to Labor Secretary Elaine L. Chao urging OSHA to set an emergency standard. In addition, health experts have written to EPA asking about the status of a study on health effects from chemicals released when microwave popcorn is prepared at home. EPA said the study is undergoing internal and industry review and will be sent to a journal in October. But in their letter, the health experts argue that the study should not be subjected to industry review before its results are released to the public. Meanwhile, the Flavor & Extract Manufacturers Association says it is helping members upgrade safety measures and worker protections at flavor facilities.