Flavour production: lung disease study

In May this year we reported on a US study​ that suggested workers in the food-flavouring manufacturing industry may be at risk of developing an irreversible type of damage to the lungs. This week a new study implies that some workers who mix and package flavoured microwave popcorn or are involved in other flavouring manufacturing may have up to 11 times the expected risk for a serious lung obstruction disorder.

The report is a follow-up to last year's widely published news of severe lung illnesses in eight people who all worked in a small Missouri microwave-popcorn factory. Initially, health officials did not associate their illnesses with their jobs. After the eight cases accumulated and came to the attention of a lawyer, an eagle-eyed physician brought it to the attention of the state.

Missouri brought the CDC's National Institute of Occupational Safety and Health (NIOSH) in to investigate and their new report on the matter is published in the 1 August issue of the New England Journal of Medicine​.

The eight workers had no other risk factors for lung disease, but became severely ill with a respiratory illness called bronchiolitis obliterans​, a severe, obstructive lung disease that has normally been seen in people exposed to a toxic irritant in a big spill. In these workers, it appears they became ill from long-term exposure to a chemical used in making artificial butter flavouring.

After studying conditions at the plant, investigators concluded that workers were most likely becoming ill from exposure to chemicals being given off by flavour additives being mixed into the popcorn.

Soybean oil, salt and flavourings are mixed in a large, heated vat. The heat produces visible dust, aerosols and vapours with a strong buttery odour. The vapours were found in greatest concentration around the mixers, and in lesser amounts near the packaging operation. Mixers were at higher risk of developing illness than packagers.

In their investigation, which was conducted in November 2000, lead investigator Dr Kathleen Kreiss of NIOSH in Morgantown, West Virginia and colleagues conducted medical exams and environmental surveys of 117 workers in the plant.

All of these workers were 2.6 times more likely than those in the general population to experience chronic cough and shortness of breath, and twice as likely to have these symptoms compared to people diagnosed with asthma and chronic bronchitis, the study indicates.

"Overall, the workers had 3.3 times the expected rate of airway obstruction and those who had never smoked had 10.8 times the expected rate,"​ the authors write.

In other findings, a chemical analysis of the air in the mixing room revealed high levels of the artificial butter-flavouring ingredient diacetyl (2,3-butanedione).

According to Kreiss and colleagues, studies of the effects of butter-flavouring vapours with diacetyl levels at 352 parts per million "damaged" cells lining the respiratory tract of rats. Mixers at the microwave-popcorn plant in question may have been exposed to levels between 3 and 4 times that amount, they note.

"Our findings of excess rates of lung disease and associations between indexes of exposure to volatile organic chemicals and obstructive lung disease support the conclusion that an agent in butter flavouring caused occupational bronchiolitis obliterans in exposed workers at this popcorn plant,"​ Kreiss and colleagues conclude.

"Clearly, work in the mixing room of this microwave popcorn plant conferred a high risk of this rare, severe lung disease,"​ wrote Dr E. Neil Schachter of Mount Sinai School of Medicine in New York City in an accompanying editorial. "As for the health effect of microwave-popcorn products in the general population, there are no findings to date to suggest that consumers are at any risk,"​ Schachter concluded.