North America's largest union for hotel, restaurant, and kitchen workers—Unite Here???has asked manufacturers to stop using the butter-flavor chemical diacetyl in commercial and home cooking products. Exposure to high levels of diacetyl has been linked to the lung disease bronchiolitis obliterans, known as popcorn lung, among workers in factories where microwave popcorn is made. At the same time, members of the House Committee on Education & Labor have written a letter to National Institute for Occupational Safety & Health Director John Howard, asking him to investigate the uses of the additive in flavorings and cooking oils, the industries where workers may be exposed, and any health effects on the workers. The union's concern was prompted by a study commissioned by the Seattle Post Intelligencer newspaper and conducted by Seattle-based laboratory LabCor. The lab analyzed 23 cooking oils and margarines used by professional and home cooks. It found that the amount of diacetyl released from cooking oils and margarines could result in exposures for professional cooks that are as high as or higher than those that caused sickness in workers at popcorn plants. At the moment, there are no safety standards or regulations involving the inhalation of diacetyl.