SUMMARYOn December 17, 1991, the National Institute for Occupational Safety and Health (NIOSH) received a request from the Brooks Air Force Base Armstrong Laboratory, Occupational Medicine Division, to evaluate occupational exposures and health consequences associated with the use of d-limonene-based cleaning solvents at U.S. air force bases (AFB). d-Limonene is a "natural" hydrocarbon obtained from citrus peels and is a potential replacement for chlorofluorocarbons and other halogenated solvents in a number of industrial and commercial applications. Workplace observations regarding the use of personal protective equipment and housekeeping in these shops were made during the site visit.On December 17-18, 1992, a NIOSH Medical Officer conducted confidential interviews with 14 workers and 1 supervisor from Shops 169 and 76. ALC Base medical records of employees in these shops were reviewed, and the ALC Base Chief Medical Officer was interviewed.The highest concentration of d-limonene detected was a one-hour time-weighted average (TWA) of 114 parts per million (ppm), obtained from a Shop 76 employee cleaning aircraft wheel hubs. A one-hour TWA exposure of 14 ppm was detected on a This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved. applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports