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and polyaromatics were also the predominant products of incomplete combustion (PICS). The data represent an average of three samples taken over the entire course of the day's run. The organic emissions summary is presented in Table 3. PAH emissions data are presented in Table 4. The 16-PAHs include several compounds known to be carcinogenic. In particular, the presence and magnitude of benzo(a)pyrene (BaP) is of major concern. BaP is often a highly-scrutinized compound during evaluations of combustion processes, due to its high cancer potency. Particulate was collected using three separate systems, a semi-volatile organic system, airborne metals particulate collection, and a medium volume ambient PM to sampler located inside the burn but [operated at 0.11 cubic meters per minute (m 3/min) or 4 cubic feet per minute (W/min)]. The particulate emissions data generated from the use of these three systems are presented in Table 5. The authors found that the particulate emissions rate decreases with decreasing burn rate, and that nearly 100 g of particulate is emitted for every kilogram of tire combusted. A separate particulate collection system was used to analyze 17 metals found in combusted-tire ash residues. The results of the metals analysis are presented in Table 6. The only significant metals emissions compared to blank samples were lead and zinc emissions. The authors concluded that both average gaseous concentration and estimated emissions of zinc increase with increasing burn rates. 2.2 MUTAGENICITY OF TIRE FIRE EMISSIONS In a follow-up study to the 1989 Ryan report, Lemieux and DeMarini (1992) analyzed the air emissions data collected in the laboratory study to evaluate potential health impacts. An experimental technique called bioassay-directed fractionation combined with additional GC/MS analyses was used to evaluate quantity and potency of airborne mutagens from the PICs emitted during open tire burning. The method of bioassay-directed fractionation uses mutagenic assays of chemical fractions of complex mixtures such as PICs to identify chemical classes and species responsible for mutagenic activity. It was concluded that: "The mutagenic emission factor for open tire burning is the greatest of any other combustion emission studied previously. For example, it is 3-4 orders of magnitude greater than the mutagenic emission factors for the combustion of oil, coal, or wood in utility boilers" (Lemieux and DeMarini, 1992). A mutagen is defined as a substance that causes mutations. A mutation is a change in the genetic material in a body cell. These mutations can lead to birth defects, miscarriages, or cancer (ATSDR, 1990). Mutagens are of concern because "the induction of genetic damage may cause an increased incidence of genetic disease in future generations and contribute to somatic cell diseases, including cancer, in the present generation" (Amdur, 1991). Mutagenic emission factors are compared in the bar chart presented as Figure 1 for various combustion processes [units: revertants per kilogram (revertants/kg) of fuel. A revertant is represented by a bacterial colony that forms after the organic effluent from a tire burn is mixed with a specific bacteriological strain. The number of colonies are 9