In 2000, NIOSH conducted an investigation of exposures at a microwave popcorn manufacturing plant in Missouri. Public health officials contacted NIOSH because a cluster of former employees of the facility had developed a rare lung disease called bronchiolitis obliterans. The majority of employees diagnosed with bronchiolitis obliterans had been exposed to mixtures of butter flavoring chemicals. Evaluations of employees working in the plant revealed high rates of both respiratory symptoms and abnormal lung function.1 The investigation concluded that there was "a risk for occupational lung disease in workers with inhalation exposure to butter flavoring chemicals".2 Investigations of other workplaces have also shown that employees that use or manufacture certain flavorings have developed similar health problems. Because many of the cases have been associated with popcorn manufacturing plants, the term "popcorn lung" has often been used to describe the respiratory symptoms and fixed obstructive lung disease seen in these employees. Although much of the research and attention has been focused on butter flavorings, employees who are involved in the use or manufacture of other types of flavorings may also be at risk.2 Flavorings can be either natural or manmade. Some are simple and made up of only one ingredient but others are complex mixtures of several substances. Employees may be exposed to flavorings in the form of vapors, dusts, or sprays.2 There are many different types of flavorings and most have not been tested for respiratory toxicity. The Food and Drug Administration (FDA) regulates food additives for safety when eaten, but it does not require testing by other routes of occupational exposure, such as inhalation. Research continues to determine if certain components or combinations of flavorings are associated with pulmonary disease. Consumers are not believed to be at risk from preparing or eating microwave popcorn products. There are currently no specific standards for occupational exposure to butter-flavoring or the chemical diacetyl. However, OSHA standards regulating all workplaces offer protection to workers exposed to these substances. See more from topic source: https://www.osha.gov/html/a-z-index.html