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LEA Advisory #46 - Evaluation of Employee Health Risk from Open Tire Burning Page 3 of 8
<br /> Thermal degradation and oxidation of tires is a function of the process conditions applied, cross-
<br /> linkage, and how the rubber is cured. Degradation below 250° C produces an oily tar. Gaseous C1-05
<br /> hydrocarbons (methane, ethane, isopropene, butadiene, propane) are produced at temperatures
<br /> typically between 250° -450° C. As the reaction proceeds, various primary products formed in the
<br /> initial fragmentation will be rapidly converted into secondary products. Several aromatic and cyclic
<br /> compounds by means of the Diels-Alder reaction are also produced.
<br /> It has been shown that open burning, regardless of feed stock or fuel, results in greater mutagenic
<br /> emission factors than does controlled combustion provided by incinerators, boilers, cement kilns, or
<br /> other combustion devices. Chunk tires produce higher burn rates and more potent organic emissions
<br /> than do shredded tires. The mutagenic emission factor for the open burning of tires was 3-4 orders of
<br /> magnitude greater than that for the combustion of oil, coal, or wood in a utility boiler.
<br /> Airborne Emissions
<br /> All tire fires may vary and the exact emissions and concentrations cannot be predicted. There are
<br /> many factors that influence the emissions produced while the fire is burning. Some of these factors
<br /> include the amount of fuel, fire temperature, meterologic conditions, topography of the area, etc. In
<br /> most cases airborne emissions found will include volatile organics, semivolatile organics (including
<br /> polycyclic aromatic hydrocarbons [PAH]), carbon monoxide, and particulate matter, which includes
<br /> metals.
<br /> In 1983, the National Institute of Occupational Safety and Health (NIOSH) evaluated a fire
<br /> containing approximately 5 million tires. This fire,called the Rhinehart Tire Fire, covered a 4-acre
<br /> site and created a black plume of smoke approximately 3,000 feet high and 30-50 miles long. The
<br /> NIOSH evaluation showed no acute hazard for employees performing containment and cleanup
<br /> operations. Airborne monitoring of the plume indicated the presence of carbon monoxide (50-100
<br /> ppm), PAH (58-6802 ng/m3), metals (all below 2 ug/m3 except lead, zinc, and iron), total organic
<br /> compounds (0.73-0.81 mg/m3), and nitrosamine (below laboratory detection limits). (See report for
<br /> more specific emission data information.) The potential for excessive inhalation exposure to PAHs
<br /> and carbon monoxide and dermal absorption of heavy metals, primarily zinc and lead, were reported
<br /> as exposure concerns.
<br /> Volatile organic emissions were detected during the 16-acre Panoche Tire Fire, which burned 3-5
<br /> million tires within a steep-sided box canyon. Benzene concentrations did not exceed OSHA and
<br /> NIOSH allowable exposure levels when sampled on two different days at a location 50 feet
<br /> downwind of the fire. Measured benzene levels ranged from .43-.50 mg/m3. Airborne emission
<br /> sampling also detected, not significantly, PAHs, metals, and semivolatile organics (see report for
<br /> more specific emission data information). These concentrations did not exceed regulatory allowable
<br /> exposure levels. Sampling points were 50 feet downwind, 50 feet upwind and west and east of the
<br /> visual smoke plume. Subsequent industrial hygiene monitoring of Board personnel many weeks after
<br /> the fire had been extinguished indicated no employee overexposure. Sampling results indicated no
<br /> detectable hydrocarbons or heavy metals dust(zinc, cadmium,chromium, and lead). The breathing
<br /> zone samples were taken during site supervision and the soil sampling process. Air monitoring results
<br /> of employees performing remediation activities, specifically scraping burn residues from the canyon
<br /> walls onto the floor, showed the presence of nuisance particulate (.51-11 mg/m3 ), zinc (<0.002-11
<br /> mg/m3), and PAHs below their detection limits (See report for more specific emission data
<br /> http://www.ciwmb.ca.gov/pe/advisory/46/46.htm 8/11/98
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