ST. LOUIS – The Environmental Protection Agency is testing microwave popcorn to find out what chemicals are released when a bag of popcorn is popped or opened.

Vapors from a butter flavoring used in microwave popcorn have been linked to severe lung damage in dozens of people who work in microwave popcorn plants around the country, including in Missouri and Illinois.

Federal officials have said there is no evidence that consumers face a health risk from microwave popcorn. Until now, no one has directly studied the issue.

Environmental scientist Jacky Rosati, one of EPA’s principal investigators, said she decided to pursue the study after hearing a presentation on the sick popcorn workers at a medical conference in 2002.

“I thought this could fit in very well with what our lab does, which is indoor air,” said Rosati, who works in the EPA’s Indoor Environment Management Branch at Research Triangle Park, N.C. “We were very interested in the aspect of what is coming off of the microwave popcorn when you pop it.”

The EPA study, which is expected to be finished this fall, focuses on the type and amount of chemicals emitted from popping microwave popcorn and opening the bag. Other studies would be needed to determine any health effects of those chemicals and whether consumers are at risk.

The Flavor and Extract Manufacturers Association, a trade group based in Washington, D.C., said that flavors do not pose a risk to consumers.

“We are confident that flavored microwave popcorn is safe for all of us to enjoy, and FEMA looks forward to working cooperatively with the EPA,” Glenn Roberts, executive director of the flavor association, said in a statement.

The EPA study comes as 30 former workers at a microwave popcorn plant in Jasper, Mo., took their claims to court in a lawsuit that began last week.

The study involves only microwave popcorn, one of the nation’s most popular snack foods. It does not include other types of popcorn, such as that sold in movie theaters and sporting events, or popped at home on top of the stove.

Rosati and her co-investigator, Ken Krebs, have bought about 50 types of microwave popcorn of different brands, batches and flavors for the study. They declined to reveal the brands used.

The popcorn bags will be popped in a microwave oven placed inside a sealed box built specially for the experiment. Gloves stick through the front wall for access to the oven.

Air will be tested for volatile organic compounds and particles, the researchers said. The study will look at chemicals emitted from the contents of the bag and from the microwaveable bag itself.

Chemicals of interest include diacetyl, the compound that gives butter its flavor. Diacetyl occurs naturally in milk, cheese, vegetables and beer. It also can be manufactured from a solvent and used to make artificial butter flavor.

The National Institute on Occupational Safety and Health, a federal workplace safety agency, believes that diacetyl may be the component of butter flavoring responsible for dozens of cases of “popcorn workers’ lung” it has discovered in the past four years.

The Food and Drug Administration, which regulates food additives, considers butter flavoring and diacetyl to be safe for consumer use.

George Pauli, acting director of FDA’s office of food additive safety, said he is interested in EPA’s results.

“On its face, it doesn’t appear to be an issue, but you never close your eyes and ears to an issue like this,” Pauli said. “If it really was (an issue), we’d definitely look into it.”

The industry-funded Popcorn Board promotes the snack as “one of the most wholesome and economical foods available.”

“Popcorn is the type of thing that always evokes smiles,” Popcorn Board executive director Deirdre Flynn said. “That’s why you’ve seen the industry rally as much as it has.”

The average American eats 59 quarts of popcorn a year, according to the Chicago-based board. Consumers bought $1.33 billion worth of microwave popcorn in the United States in 2002, according to the Virginia-based Snack Food Association.

Microwave popcorn ranks fifth in retail sales among salty snacks, after potato chips, tortilla chips, meat snacks such as beef jerky, and snack nuts, the association said.

The snack appears in grocery stores in a wide variety of flavors, including “movie theater butter,” “blast-o-butter,” and the slightly sweet “kettle corn.”

Popcorn fanatic Ruben Micich of St. Louis said he eats three large bowls of popcorn a week. He makes popcorn at work in a movie-theater style popper for his fellow firefighters. He also eats microwave popcorn at home.

Micich, 45, said he didn’t worry about his own safety when he heard about the workers’ illnesses. “I can only assume because of the large quantities they’re dealing with at the factory that it must be in the atmosphere at a pretty high level,” he said. “I don’t think it would be that way at home, at least hopefully.”

But Micich said he’d quit eating microwave popcorn if EPA’s study finds a problem. “It’s got to be one of the worst feelings, not being able to breathe,” he said.

The workers in the Missouri lawsuit say they suffered various respiratory illnesses from breathing butter flavor vapors. At least eight have been diagnosed with bronchiolitis obliterans, a rare and incurable lung disease. Several are on waiting lists for lung transplants.

Their lawsuit claims that butter flavoring manufacturer International Flavors & Fragrances, and its subsidiary, Bush Boake Allen, knew or should have known that the flavoring was hazardous, and that the manufacturers failed to adequately warn the workers.

The manufacturers have denied liability in the case. International Flavors & Fragrances has blamed any health problems on “inadequate workplace conditions.”

The plant’s owner since 1999, Chester, Ill.-based Gilster-Mary Lee, is not a defendant in the lawsuit.

Most of the attention in the butter flavor controversy has focused on workplace safety. Fred Blosser, a spokesman for NIOSH, said that the respiratory problems the agency has observed so far appear to relate to workers breathing high levels of butter flavor vapors for extended periods.

But there is no known “safe” level of butter flavor vapors. In a NIOSH study, rats developed severe airway damage after being exposed to butter flavor vapors for six hours. The vapors contained levels of diacetyl two to four times higher than the highest average level measured during a workday.

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