Popcorn makers across the country have decided to eliminate use of diacetyl flavoring, which gives microwave popcorn its distinctive buttery aroma, because of its linkage to a fatal lung disease.

Hundreds of workers at a ConAgra Foods popcorn factory in Marion, Ohio, and at a Cincinnati plant filed lawsuits after coming down with the disease, known as bronciolitis obliterans, according to theCleveland Plain Dealer. The Marion plant makes microwave popcorn under the Orville Redenbacher and Act II brands, while the Cincinnati factory makes the diacetyl buttery flavoring.

The lawsuits contend that at least one worker at the Cincinnati plant run by Givaudan Flavors Corp., a division of a Swiss-based maker of food flavorings and cosmetic fragrances, died from repeatedly breathing the chemical diacetyl.

Members of Congress launched campaigns this summer to have the Food and Drug Administration examine diacetyl's safety and to have OSHA set airborne standards for diacetyl in factories.

Last week, two senators, union leaders and researchers urged the federal government to set tougher restrictions on diacetyl. Democratic Sens. Edward Kennedy of Massachusetts and Patty Murray of Washington sent letters on the matter Sept. 7 to the Centers for Disease Control, FDA and Department of Labor. They urged the Labor Department to issue an "emergency temporary standard" for employees regularly exposed to the chemical, saying it "has caused death and serious injury in many workers."

FDA spokeswoman Kimberly Rawlings said her agency is "evaluating the recent information on the association of inhalation of diacetyl with lung disease" and is "carefully considering the safety and regulatory issues it raises."

Also Sept. 7, a group representing the AFL-CIO, Teamsters and other unions, plus researchers from numerous medical schools, urged the Labor Department to regulate workers' exposure to diacetyl. House legislation that would require new guidelines is backed by the Flavor and Extract Manufacturers Association, a key trade group, they noted.

Popcorn makers including ConAgra announced plans to ditch diacetyl earlier this month. ConAgra spokeswoman Stephanie Childs says the company doesn't think consumers face hazards from diacetyl, noting it is approved by the FDA and exists naturally in foods including butter. She said that the company will phase out its use in popcorn because of inhalation risks to employees.

OSHA, which has adopted an upgraded safety program limited to popcorn plants, opposes a bill proposed by California Democratic Rep. Lynn Woolsey that would regulate airborne diacetyl in the workplace. OSHA's Edwin G. Foulke Jr. said in a letter to Congress that that focusing on diacetyl alone might result in a failure to consider other factors that contribute to bronciolitis obliterans and that OSHA would need more time than the two years the bill allows to determine all the ways workers might be exposed to diacetyl.