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## 6.2.3. HAPs Emission Inventory Methods 

Again, it is important to acknowledge that there are currently no federal regulatory guidelines specific to HAPs emissions from aircraft engines, specifically, and airports, in general. While the methodology discussed in this Handbook is useful for disclosure, reporting, and comparative purposes, it does not provide results that are directly comparable to any regulatory threshold or air quality standards. 

It is also important to note that other than an emissions inventory, a HAPs assessment prepared for the FAA must not include any other type of analysis including, but not limited to, atmospheric dispersion modeling, toxicity weighting, or human health risk analyses. These types of assessments require a more complete understanding of the reactions of HAPs in the atmosphere and downstream plume evolution as well as human exposure patterns. Because the science of these relationships with respect to aviation-related HAPs is still evolving, the corresponding level of understanding is also currently limited. 

As stated previously, in cases where it is necessary to prepare such an aviation-related HAP inventory, the inventory must be prepared following the Speciated Organic Gas Emissions from Airports Guidance and using EDMS/AEDT. In this application, EDMS/AEDT applies speciation factors to quantify individual HAP compounds. These factors estimate the quantities individual HAPs based on the total emissions of VOCs. Notably, t he EPA MOVES emission factor model should be used to develop individual HAP speciation data for motor vehicles. 

Presently, EDMS/AEDT calculates emissions for 394 different OGs. Of these, 45 are classified as HAPs by the EPA while the other 349 are considered to be non- toxic compounds. These 45 HAPs are listed in Table 6-4 ( Potential HAPs to be Included in an Airport Emissions Inventory ). 

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Source: FAA, Guidance for Quantifying Speciated Organic Gas Emissions from Airport Sources, September 2, 2009, http://www.faa.gov/regulations_policies/policy_guidance/envir_policy/media/Guidance%20for%20Quantifying%20Speciated %20Organic%20Gas%20Emissions%20from%20Airport%20Sources.pdf. 

