The National Institute for Occupational Safety and Health (NIOSH) received from the UNITE HERE International Union a request for health hazard evaluations (HHE) of respiratory health and inhalation exposures of food preparation workers at three New York City food service facilities managed by the Aramark Corporation. This request was prompted by concerns of exposure to artificial butter-flavored cooking oils, containing diacetyl. Exposure to diacetyl is associated with a severe lung disease, called bronchiolitis obliterans. NIOSH findings and recommendations are detailed.