Researchers in the Netherlands have identified a chemical agent that may be a, if not the, culprit in bronchiolitis obliterans syndrome (BOS), or “popcorn worker’s lung,” a severe occupational lung disease first noted in 2001 among workers at an American plant that makes microwaveable popcorn.The research, which examined a population of workers at a chemical plant that produced diacetyl (a key component of butter flavoring), was reported in the first issue for September of the American Journal of Respiratory and Critical Care Medicine, published by the American Thoracic Society.