Sleuths hot on the trail of a disease, its cause

A cluster of cases of a rare illness in a tiny Missouri town triggers a meticulous collection and study of data by government scientists

The Science

Special Report


MORGANTOWN, W.VA. -- The knowledge that dozens of workers exposed to butter flavoring at popcorn plants in six states were falling ill wasn't enough for the federal scientists who investigate occupational health diseases.

They had to collect thousands of samples of air and chemicals, X-rays and medical tests. They had to pick apart the evidence to establish what was happening and why.

All the data were brought back for analysis and interpretation at the two buildings in this picturesque college town where National Institute of Occupational Safety and Health experts on respiratory disease work.

The cases of lung damage among popcorn workers came to light over the Thanksgiving holiday in 1999. A lawyer helping his stepfather file for worker compensation learned that others at the same popcorn plant were also ill.

He consulted Dr. Allen Parmet in Kansas City, Mo. "What I saw made no sense at all," recalled Parmet, an occupational medicine specialist. "Bronchiolitis obliterans is a very rare disease, and I'd only seen three cases of it in my quarter-century of practice."

Two were victims of a 1977 Titan missile leak of nitrogen tetroxide and the third was a patient exposed to sulfuric acid. Now he had eight cases from one tiny town - Jasper, Mo.

The town's largest employer was the Gilster-Mary Lee Corp. popcorn plant.

Parmet notified Missouri's health department, which alerted the Centers for Disease Control and Prevention. Because the health problems involved a workplace, CDC bounced the cases to NIOSH, its agency for investigating occupational hazards.

In late 2000, field investigation teams from NIOSH's respiratory laboratory swarmed in and around the Jasper plant, where 31 workers suffered serious breathing problems. Five former workers were already so sick they were waiting for transplants.

"It sounded like something serious, and we wasted no time getting our people out there," said Dr. Kathleen Kreiss, chief of the institute's field studies branch.

The teams of physicians, industrial hygienists, medical interviewers, epidemiologists and technicians worked out of government trailers. They tested how well the workers' lungs functioned and took chest X-rays.

They "asked every employee all the places they had ever worked in the plant and compared that to measurements of chemicals in the air," said Kreiss.

Six months later, the institute issued an emergency bulletin to all state health departments about the disease surfacing among popcorn workers. The bulletin cautioned that in the process of sealing corn into a microwave-able plastic pouch with heated oil, salt and butter flavoring, toxic vapors were being released.

NIOSH's investigation widened to include sick workers at five other plants throughout the Midwest. "Some plants were very eager to cooperate, including the smaller ones. They seemed genuinely concerned about the safety of their workers," said Kreiss.

The sleuths from NIOSH were as extensive and meticulous as the busiest crime scene investigators. They repeatedly observed, tested, questioned and, at the six plants, examined how well worker's lungs were functioning.

They collected hundreds of samples of air from different work stations along production lines and gathered samples of flavorings and other chemicals.

Back in the agency's laboratory, Dr. Ann Hubbs, a veterinary pathologist, was able to document butter flavoring's toxicity on rats. Another elaborate animal study is under way to test the outcome of exposure to diacetyl by itself.

Scientists had to rule out coincidence and chance and show precisely how toxic exposures had occurred. They recorded the exact location where each worker was assigned and how much time was spent on the production line. They determined whether the butter flavoring containing diacetyl was being added to heated oil and, if so, at what temperature. They identified which chemicals were being released and at what concentrations.

Studies in different popcorn plants showed that the same injury occurred among workers even at much lower levels of exposure than at the first plant. Such consistency of finding disease where similar hazards exist shows that the flavoring exposures cause it.

The greatest risk of serious lung disease was among the workers who mixed the flavoring, NIOSH concluded.

Kreiss called the findings "highly statistically significant and not likely to be due to chance."

NIOSH, which found the disease in five of the six plants, recommended ways to prevent it, such as ventilation, appropriate respiratory protection and isolation of the oil and flavoring mixing process.

"Exposure controls implemented by the microwave popcorn companies," said medical officer Dr. Richard Kanwal, "have largely eliminated butter flavoring exposures as a risk for lung disease for most workers in these plants."

A little more than 400 miles southeast, at Research Triangle Park, N.C., a scientist with the Environmental Protection Agency has popped several dozen bags of supermarket popcorn in a battered microwave to see whether dangerous vapors are released when the bags are opened.

The EPA says it's awaiting evaluation of the tests.

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