Health hazard evaluation report: HETA-99-0266-2850, Costa Mesa Fire Department, Costa Mesa, California.
On August 4, 1999, the National Institute for Occupational Safety and Health (NIOSH) received a request from the Costa Mesa Fire Department (CMFD), located in Costa Mesa, California, to conduct a health hazard evaluation (HHE). The CMFD was planning to install diesel exhaust filtration systems on some of their apparatus and wanted NIOSH to evaluate the effectiveness of the controls. In response to the request, NIOSH conducted pre- and post-control evaluations of diesel exhaust in two fire stations. The pre-control evaluations were conducted on November 8-11, 1999. Samples were collected to characterize contaminant concentrations at the fire stations, and to provide base line data for determining the effectiveness of the ceramic exhaust filters at controlling these contaminants. Airborne concentrations of elemental carbon (Ce), sulfur dioxide (SO2), nitric oxide (NO), nitrogen dioxide (NO2), and volatile organic compounds (VOCs) were measured. After the ceramic filters were installed on the engines, a follow-up evaluation was conducted on March 14-17, 2000, to determine the control's effectiveness in reducing diesel soot (measured as Ce) in the fire stations. In the initial survey, only trace concentrations of Ce were measured in personal breathing zone (PBZ) samples at each station. Concentrations of Ce in the living quarters of each station were mostly in the none detected to trace range as well. The 12 Ce area samples collected in the apparatus bay of each station had mean concentrations of 6.1 micrograms per cubic meter ( g/m3) in station 3, and 15.6 g/m3 in station 5. SO2 was not detected in any spot samples collected in the apparatus bay of either station. This indicates that the concentration of SO2 in the bay did not exceed 0.1 ppm as the apparatus entered and departed the station. NO concentrations in the apparatus bay of both stations were all below the minimum detectible concentration (MDC). This indicates that all concentrations were below 0.5 ppm as an 8-hour time weighted average, which is well below the current evaluation criteria. Low concentrations of several organic chemicals were identified. Identified chemicals included methyl t-butyl ether, C4-C7 alkanes, benzene, toluene, and xylenes. Concentrations of benzene and xylene were quantified, and were well below current exposure criteria. In the post-control evaluation, Ce was not detected on 12 of 16 area samples collected in the bay of station 3. Four area samples had a trace amount of Ce, indicating that Ce concentrations in the bay were between the MDC of 1.3 g/m3 and the minimum quantifiable concentration (MQC) of 5.1 g/m3. Ce was not detected on 11 of 16 area samples collected during the post-control sampling campaign at station 5. Trace concentrations of Ce were detected in four area samples, indicating that Ce concentrations for these samples ranged from 1.3 to 5.1 g/m3. A significant reduction in geometric mean Ce concentrations in the apparatus bay of both stations was evident in the data. The reductions were 76% in station 3 and 91% in station 5. The NIOSH environmental assessment of diesel exhaust in two fire stations found that concentrations of diesel exhaust gas-phase components were low prior to the installation of engineering controls. Personal exposures to diesel exhaust particulate-phase components in these two fire stations were also low because the quantities of Ce generated were moderate and because firefighters and paramedics did not spend very much time in the apparatus bay. However, geometric mean concentrations of Ce in the two bays were reduced by 76% and 91% after the ceramic diesel exhaust filters were installed. NIOSH researchers concluded that, in stations with pull-through apparatus bays, the ceramic filters are effective at reducing the emission of diesel soot. Recommendations were made for maintaining positive pressure in the living quarters relative to the bay and for a more formalized means of training and information exchange about engineering controls, should they be installed at other stations.