In January 2004, the National Institute for Occupational Safety and Health (NIOSH) received health hazard evaluation (HHE) requests from the United States Department of Homeland Security, Transportation Security Administration (TSA) related to checked baggage screening operations at the following four international airports: Palm Beach, Florida (PBI); Miami, Florida (MIA); Washington-Dulles, Virginia (IAD); Baltimore-Washington, Maryland (BWI). TSA expressed concern about health hazards from exposure to contaminants found in exhaust emissions of tug and jet engines and noise from tugs, jets, conveyors, and baggage carousels. Health problems reported at the four airports included respiratory distress, dizziness, possible hearing loss, and headaches. NIOSH investigators conducted site visits at the four airports, collecting general area and personal breathing zone (PBZ) air samples for carbon monoxide (CO), nitrogen dioxide (NO2), nitric oxide (NO), diesel exhaust particulate (measured as elemental carbon [EC]), and volatile organic compounds (VOCs). Full-shift personal noise monitoring was also conducted. This report is a composite of the individual reports issued under HHE #s 2004-0100, 2004-0101, 2004-0130, 2004-0146. A total of 72 PBZ samples were collected for EC, a surrogate for diesel exhaust; concentrations ranged from 1 to 26 micrograms per cubic meter (microg/m3). There are no NIOSH or Occupational Safety and Health Administration (OSHA) exposure limits for EC; however, the California Department of Health Services recommends keeping exposure levels below 20 microg/m3. While four PBZ samples exceeded 20 microg/m3, the average exposures across all four airports were 11 microg/m3. A total of 40 PBZ samples were collected for both NO and NO2. "Trace" concentrations of NO were measured at MIA, IAD, and BWI (defined as between 0.03 parts per million [ppm] and 0.7 ppm). These values correspond to the Minimum Detectable Concentration [MDC] and the Minimum Quantifiable Concentration [MQC]. Trace concentrations of NO2 were also measured at these airports (between 0.02 ppm [MDC] and 0.8 ppm [MQC]). Concentrations of NO and NO2 were "not detectable" at PBI (defined as below 0.15 ppm [MDC]). Similar results were obtained for 21 full-shift general area air samples using the same sampling method. Measurements made with direct-reading instruments yielded similar results. None of the NO and NO2 samples exceeded their respective NIOSH Recommended Exposure Limit (REL), American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV), or the OSHA Permissible Exposure Limit (PEL) (25 ppm for NO; 3 ppm for NO2). A total of 61 full-shift exposure measurements for CO were collected using direct-reading instruments. PBZ exposures ranged from 1 to 5 ppm (full-shift time-weighted average [TWA]) and from 1 to 16 ppm (15-minute short-term exposures). Instantaneous peak values ranged from 176 ppm to 333 ppm. No average exposure values exceeded any occupational exposure limit (NIOSH REL = 35 ppm; ACGIH TLV =25 ppm; OSHA PEL = 50 ppm). The dominant VOCs identified within the baggage screening areas of all surveyed airports were isopropyl alcohol, toluene, and low molecular weight hydrocarbons. A total of 20 general area air samples were collected; concentrations ranged from "none detected" (below the MDC; isopropyl alcohol and low molecular weight hydrocarbons - 0.1 mg/m3; toluene - 0.02 mg/m3) to "trace" (below the MQC; isopropyl alcohol and low molecular weight hydrocarbons - 0.5 mg/m3; toluene - 0.05 mg/m3 but above the MDC). All measurements were well below any occupational exposure limit. Gasoline-powered tug tailpipe emissions for hydrocarbons (HC), CO, and oxides of nitrogen (NOx) were measured at two airports while the tugs idled. Tailpipe concentrations of these compounds were as follows: HC ranged from 20 ppm to 1700 ppm; CO ranged from zero ppm to 86,500 ppm; NOx ranged from zero ppm to 52 ppm. The majority of the tugs' engines ran poorly. None of the measured noise doses from the 56 full-shift samples exceeded the OSHA 8-hour PEL. However, each airport had a few workers with exposures above the NIOSH REL. This finding led to recommendations for additional noise assessments and changes in airport equipment and facility structure. Additionally, the interim use of hearing protection devices as part of a hearing conservation program is recommended unless measured noise doses do not exceed the NIOSH REL, or the use of engineering or administrative controls have been effective in reducing worker exposure to below the NIOSH REL. The NIOSH investigators determined that a hazard does not exist from exposure to EC, CO, CO2, NO2, NO, or VOCs. Some tug emissions were elevated when compared to ambient levels and could contribute to an increase in air contaminants in some baggage areas. There was little evidence of a serious noise problem. However, additional noise analyses may be useful in characterizing worker exposure in areas where the NIOSH REL was exceeded. Also, changes in the maintenance of baggage handling equipment (conveyors) and repairing cracks in the concrete floors are needed to reduce unnecessary noise. Additionally, the interim use of hearing protection devices is recommended for workers whose noise doses exceed the NIOSH REL. Other recommendations for maintaining the air quality and further reducing noise exposures are provided in the Recommendations Section of this report.