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from the project which would not cause or contribute to an air quality exceedance of the most stringent applicable federal or state ambient air quality standard at the nearest sensitive receptor, taking into consideration ambient concentrations in each source receptor area, project size, distance to the sensitive receptor, and other factors... Table 3.2-2 shows that the proposed project's localized construction emissions would not result in a locally significant air quality impact" (p. 3.2-1— 3.2-2). Regarding operational health risk impacts, the Addendum attempts to justify its significance determination by stating, "Table 3.2-4 shows that on -site operational emissions would not exceed the LSTs for sensitive receptors in the project area" (p. 3.2-4). The excerpts above demonstrate the Addendum's attempts to evaluate the Project's health risk impact without conducting a quantified HRA. The failure to quantify the health risk posed to nearby sensitive receptors from exposure to toxic air contaminant (TAC) emissions released during Project activities, and instead reliance upon an LST analysis, is incorrect for several reasons. First, the use of the LST method to determine the Projects health risk impacts on nearby, existing sensitive receptors is incorrect. While the LST method assesses the impact of pollutants at a local level, it only evaluates impacts from criteria air pollutants. According to the Final Localized Significance Threshold Methodology document prepared by the SCAQMD, the LST analysis is only applicable to NO, CO, PMlo, and PM2.5 emissions, which are collectively referred to as criteria air pollutants.6 Because the LST method can only be applied to criteria air pollutants, this method cannot be used to determine whether emissions from DPM, a known human carcinogen, will result in a significant health risk impact to nearby sensitive receptors. As a result, health impacts from exposure to toxic air contaminants (TACs), such as diesel particulate matter (DPM), were not analyzed, thus leaving a gap within the Addendum's analysis. Second, by failing to prepare a quantitative HRA in addition to the LST analysis, the Addendum fails to provide a comprehensive analysis of the sensitive receptor impacts that may occur as a result of exposure to substantial air pollutant emissions. Seeing as Project construction is expected to occur over an approximately two-year period, it is reasonable to assume that a significant amount of diesel particulate matter (DPM), a known human carcinogen, will be emitted from the exhaust stacks of equipment required for Project construction (p. 2-10). Similarly, the Addendum determines that operational activities will include approximately 1,420 daily vehicle trips, thus generating diesel exhaust over the duration of Project operation (Appendix E-1, p. 19, Table 5-1). As such, the Addendum should have conducted a construction and operational health risk assessment, as long-term exposure to DPM and other TACs may result in a significant health risk impact that therefore, must be properly assessed. Furthermore, the SCAQMD provides a specific numerical threshold of 10 in one million for determining a 6 "Final Localized Significance Threshold Methodology." SCAQMD, Revised July 2008, available at: http://www.agmd.gov/docs/default-source/cega/handbook/localized-significance-thresholds/final-Ist- methodology-document.pdf. 5