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Executive Summary The CEMEX portland cement plant in Lyons, CO is considering the use of scrap tires as a future supplemental fuel source. To confirm the potential impact on human health from tire- derived fuel {TDF) compared to fossil fuels alone {FF), the Lyons plant conducted a source emissions test from November 13-22, 2002. The test was conducted under normal operating conditions and measured a wide range of metals, inorganic, and organic chemicals. ^ CEMEX tested for a suite of elements and compounds far more extensive than required under current regulations. • Emissions were measured during both conditions: FF only, and FF combined with 19% TDF. • The results of the source emission tests indicate that overall emissions are low when either FF or TDF is used and well within all applicable permit and regulatory requirements. ^ Emission levels and related health risks are similar in the Lyons Plant test to those conducted at other facilities. • The Lyons Plant results indicate that the risk to human health from the use of FF or TDF is extremely low and below regulatory concern levels. The specific types and amounts of chemical emissions measured at the Lyons plant for both FF and TDF were generally similar to emission profiles from previous stack tests at other cement kilns around the country. However, there were also several differences in the Lyons Plant source emission worth noting. At cement kilns that have conducted comprehensive stack emission tests and human health risk assessments, the risk driver chemicals were either formaldehyde, benzene, polychlorinated biphenyls (PCBs), dioxins/furans, carcinogenic polycyclic aromatic hydrocarbons (PAHs), or a combination of these chemicals. Although some of these chemicals were detected during the Lyons Plant emissions tests, the emission 'rates tended to be lower than for other facilities. Furthermore, PCBs were not detected for either FF or TDF, and dioxin/furans, expressed as TCDD equivalents, were not detected during the TDF test. Conversely, the emission rate for chromium was higher for both FF and TDF at the Lyons Plant than at other facilities, although it was still low from a human health perspectivet The emission rates for these chemicals are of particular interest in terms of human health because collectively they have been shown to be responsible for 83-98% of the potential human health risks from cement kiln emissions. The differences in emission rates between FF and TDF were relatively modest, particularly in terms of the risk driver chemicals discussed above. Formaldehyde emission rates for TDF were twice the rates for FF and chromium was about 50% higher for TDF compared to FF. Dioxin/furan (TCDD equivalents) were barely detected during the FF test and not detected in the TDF test. Carcinogenic polycyclic aromatic hydrocarbons (PAHs expressed as benzo(a)pyrene equivalents) were detected at extremely low concentrations in both the FF and TDF tests. Benzene emission rates were higher for TDF than FF but still on the low end of the range for most cement kilns. 2