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Show Visalli states "No relationships are apparent for any of the data sets. This result is not surprising, given the fact that the concentrations of HCI in the flue gas stream, even at the lowest levels, are thousands of times greater than the corresponding concentrations of dioxin. Chlorine availability in refuse is ubiquitous, and so little of it is needed to form typical quantities of dioxin, it is doubtful that limiting the quantity of any type of chlorinated waste material, such as chlorinated plastics, will have any effect on the quantity of dioxin produced by incineration. A similar scatter plot for total furans also showed no apparent relationship with HCI concentration." Role of PVC The role of PVC in the synthesis of dioxin is postulated to occur via two mechanisms: either the PVC is acting as a chlorine donor to form HCI, or the pyrolysis products of PVC include PCDD precursors, e.g. chlorobenzenes and chlorophenols. No PCDD/PCDF compounds have been formed in degrading pure PVC. Karasek l6 reported on the combustion of PVC added to the waste fed into a Martin waterwall, resource recovery boiler in France. Sufficient PVC was added to the MSW stream to triple its original PVC content. No differences in the PCDD/PCDF emission levels were measured despite 6the 300 percent additional PVC in the refuse. Commoner questioned the significance of these results, stating that "a null effect from increasing the availability of chlorine does not necessarily negate the likelihood that reducing it will lower PCDD/PCDF production. The latter effect depends on the fact that chlorine is the limiting factor in the reaction system. Increasing the chlorine content could readily reverse the situation, making the phenolic precursors the less available reactant and therefore the limiting factor". A recently completed studyl7 focused on the role of combustion conditions and the presence of PVC in the formation of PCDD/PCDF. The study was conducted at the Vicon incinerator facility in Pittsfield, MA, under the auspices of the New York State Energy Research and Development Authority (NYSERDA). The test program at Pittsfield is shown in Table 4 . All of the tests conducted during this study involved either MSW or PVC-free waste; two of the PVC-free waste runs included spiking with PVC in an effort to match the chlorine content in the MSW. Also, two of the MSW runs were spiked with larger quantities of PVC in an effort to increase the chlorine content to 4 to 5 times the amount present in the |