Millions of Americans are exposed regularly to vapors released when they heat products containing the same synthetic butter flavoring blamed for destroying the lungs of workers in popcorn and flavoring factories. But public health activists say no one in government has stepped up to assess whether consumers are at risk.

The Food and Drug Administration has jurisdiction over products people ingest but reports it has no plans to investigate. Critics say the agency's response reflects a pattern of governmental indifference to the possible threat posed by breathing diacetyl, a butter flavoring agent.

In addition to the FDA, two other agencies charged with protecting Americans' health have some authority in this area. The Occupational Safety and Health Administration holds sway over the workplace, and the Environmental Protection Agency deals with air pollutants.

"The problem with a chemical like diacetyl is that the route of exposure - inhalation - does not fit easily the jurisdiction of any of these agencies," said David Vladeck, a Georgetown University law professor who spent 30 years at Public Citizen handling litigation on food and drug issues.

Rep. Henry A. Waxman of California, the ranking Democrat on the House Government Reform Committee, was more blunt.

"Multiple agencies appear to have simply passed the buck" on diacetyl, he said, "and as a result we still don't know if the average consumer should be worried."

Problems with diacetyl first surfaced in 2000 when dozens of workers at a microwave popcorn plant in Jasper, Mo., developed a rare disease called bronchiolitis obliterans, which destroys the lungs.

The National Institute for Occupational Safety and Health, the investigatory workplace-safety arm of the Centers for Disease Control and Prevention, tracked the disease to five other Midwest popcorn plants, finding that the butter flavorings, and most likely diacetyl, caused the disease. NIOSH documented that diacetyl gave off toxic vapors when it was heated and, in some of the plants, found the highest incidence of disease among workers in the quality-control areas, where the packaged corn, ready for market, was popped in microwaves and sampled.

NIOSH repeatedly informed OSHA of the hazard it identified and urged a broader investigation of workplaces throughout the country that either manufacture flavorings with diacetyl or use it in thousands of consumer products.

In April, The Sun reported on more than a dozen cases of lung disease across the country. Since then, health officials in Ohio have identified more than 20 former workers at a Cincinnati flavoring manufacturer who have the disease, and physicians elsewhere have diagnosed more than a dozen other cases.

OSHA has taken no action to set exposure limits for the chemical. Last month, the Teamsters, other unions and Congress members petitioned it to take immediate action to identify and eliminate the risk to food and flavoring workers.

The Flavor and Extract Manufacturers Association of the United States, which represents some companies that make or use flavoring with diacetyl, has told OSHA it "supports the expeditious establishment of an appropriate standard for diacetyl that will help to protect workers," according to John Hallagan, the association's spokesman.

While OSHA is being faulted for ignoring workers, no other government agency has calculated the hazard, if any, to consumers who use microwave popcorn or cook with other products containing diacetyl. The butter-flavoring agent is used in margarine, faux butters, cooking oil, lard and, according to food scientists, in thousands of frozen products.

The Environmental Protection Agency has been studying the amount of diacetyl released during home cooking of microwave popcorn. But that study, which so far has been shared with the flavoring industry but not released to the public, will not fully answer questions about potential hazards.

That's because no one has determined what amount of diacetyl poses a threat to humans. To date, no federal regulatory agency has plans to do so.

The FDA, which could investigate under its governmental mandate, said it has no plans to do so because it says studies have shown that diacetyl could be safely consumed in food. But those studies were done in the late 1950s and early 1980s and examined only the hazard from ingesting diacetyl, not inhaling its vapor, which is what sickened the workers.

Michael Cheeseman, associate director of the FDA's Office of Food Additive Safety, said diacetyl occurs naturally in butter. And while the agency has not tested what kinds of vapors are released when products containing diacetyl are used in cooking, he said home cooks are not "being exposed to anything that they would not be exposed to if the food were prepared with real butter."

That statement is questioned by many familiar with the chemical.

"How does he know that the diacetyl from cows is identical to diacetyl brewed in chemical vats?" asked Dr. David Egilman, a specialist in occupational medicine who was an expert witness for many of the injured popcorn workers in their lawsuits against flavoring companies.

Dr. David Michaels, director of the Project on Scientific Knowledge and Public Policy at George Washington University's School of Public Health, called the FDA's conclusions "absurd."

"There is no evidence that breathing diacetyl vapors is safe and plenty of evidence that it is deadly," he said.

andrew.schneider@baltsun.com