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Michael P. Kenny, Executive Officer -5- September 3, 1998 levels of CO were <1 ppm, hydrocarbons were 9 ppm to <1 ppm, and toluene was 5 ppm to <1 ppm. Note: The NIOSH recommended exposure limit (REL) for CO is 35 ppm (10-hr ay.), and the immediately dangerous to life and health (IDLH) level is 1200 ppm. The NIOSH REL for toluene is 100 ppm, and the IDLH level is 500 ppm. Total carbon results for the period August 10— 21, 1998 are shown in Table 2. Atmospheric particulate matter, a complex mixture of chemicals, is partially made up of organic and elemental carbon. The elemental carbon (soot) is a product of combustion. Total carbon (organic and elemental) concentrations in the northern San Joaquin Valley are generally between 5 and 10 micrograms per cubic meter during the summertime, and 40 - 60 micrograms per cubic meter during the wintertime. The higher wintertime concentrations are due to lower temperatures and the use of fireplaces. In an effort to determine the affect of the tire fire near Tracy, filter samplers were placed near the fire (0.25 mile downwind) and further downwind from the fire -. - --. (1.5 miles) on August 8. A third sampler was TP installed at a generally upwind location on August 11. The particles collected on these filters were analyzed for total carbon. Total carbon, rather than total particulate matter, was thought to be a much better indicator of the fire's impact. Table 2 shows the results of that monitoring. As expected, the impact near the fire on August 8 is clearly visible. However, because the smoke plume rose nearly vertically and dispersed in the upper atmosphere, the impact further downwind from the fire was minimal. After August 8, total carbon concentrations fell to near normal levels, Total Carbon Sampler showing much less impact in the area. In cooperation with the San Joaquin Public Health Department, total carbon sampling and analyses were discontinued on August 21. An instrument called an aethylometer was installed at the nearest residence (Site#1, 0.25 mile SE of the fire), instead. This instrument measures elemental carbon (soot) on an hourly basis. The instrument is currently being operated by the San Joaquin Public Health Department to determine the impact of the fire at this location. Carbon data obtained by the instrument has not been validated, finalized and released by the Health Department staff, however, the results are reportedly consistent with the 24-hour samples obtained by ARB earlier. The instrument does show hourly concentration variations as expected with diurnal meteorological changes.