### APPROACH FOR MODELING POM Issues with modeling POM Not all POM reported to EPA’s national emission inventory (NEI) are speciated into individual compounds. As a result, we must apply some simplifying assumptions in order to model and assess the risk from the individual pollutants that comprise POM. This involves establishing different POM “groups” and modeling them as separate pollutants. In establishing these groups, we considered the need to provide the most detailed information about risks from the individual pollutants within POM while taking into account the inconsistencies in how much speciation is reported in the inventory. We used a more refined method to establish POM groups for the 1999 NATA than we did for the 1996 NATA to reflect improvements in the speciation of POM within the inventory. Specifically, for the 1996 NATA we had two overlapping POM groups and for the 1999 NATA we have eight distinct groups.

1996 NATA Approach For the 1996 NATA, we had two POM groups: (1) 7-PAH and (2) total POM. Note that the two groups overlap one another in that the total POM also contains pollutants in the 7-PAH group. We chose these groups in order to provide a range of the risk estimate. This is because the bulk of the POM was reported in the inventory as unspeciated POM. In addition, in some cases, the inventory contained more than one PAH group for the same stack (e.g., unspeciated POM, unspeciated 7-PAH in the same stack). For 7-P AH, we included only those pollutants that either were individual constituents of the 7-PAH group, su ch as benzo(a)pyrene, or were reported as “7-PAH” in the inventory. This would potentially be the low range since it did not include any pollutants identified as total POM, which presumably include some 7-PAH. The total POM group included all individual compounds belonging to POM as well as unspeciated POM and PAH groups. In addition, the total POM group included the compound “naphthalene” which is listed as a separate HAP in the Clean Air Act list of 188, but was not inventoried this way in the 1996 inventory. The total POM group could concei vably double count emissions from stacks in which multiple POM groups were reported. Additional explanations for the approach can be found in Appendix D of the EMS-HAP User’s Guide, Version 2.0, which can be downloaded from www.epa.gov/ttn/emch/models . An explanation of the risk assumptions for these two groups can be found at http://www.epa.gov/ttn/atw/nata/nettables.pdf . As is stated in the latter document, the risk from the 7-PAH group was found to be significantly lower than that from the total POM group, and the 7-PAH group was subsequently dropped from the assessment.

1999 NATA Approach For the 1999 NATA, we used a very different, more refined approach to group POM to reflect the improvements in the inventory. There are three main 1999 NEI improvements related to POM. First, a larger quantity of the 1999 NEI emissions is speciated into individual POM compounds. Second, there is no double-counting of POM groups from individual stacks in the point source inventory. There was still an inve ntory issue relating to double counting of 7-PAH and 16-PAH from numerous non-point sources (e .g., animal cremation, human cremation) and nonroad (e.g., 2-stroke logging equipment). We fixed this issue prior to ASPEN modeling by creating a “new” inventory pollutant, whose em issions are the difference between 16-PAH and 7-PAH. Third, naphthalene is inventoried as a separate HAP and is not included nor summarized in any PAH group.

### APPROACH FOR MODELING POM The approach taken to assess POM for the 1999 NATA is to group inventory POM species into non-overlapping categories for which we can associate similar inhalation risks based on the unit risk estimate (URE). Unit risk estimates were obtained from the toxicity table http://www.epa.gov/ttn/atw/toxsource/table1.pdf (ver sion dated October 2003) for the individual POM compounds. Table 1 shows the 8 POM groups and the associated URE assignments. Note that naphthalene is not included within any of the 8 POM groups for the 1999 NATA. For the 1999 NATA, naphthalene is modeled and treated as a separate HAP; it is not combined with other pollutants considered to be POM.APPROACH FOR MODELING POMTable 1. POM groups for the 1999 National Scale Air Toxics AssessmentPOMGROUP(EMSHAPcode)Names Used in NATAWebsiteDescription of Group URE forRiskCharacterizationBasis for URE71002POM, Group 1: UnspeciatedPOM_Group_1_unspecGroup contains unspeciated POM, noURE is associated with them5.5 * 10-5Assume same URE as was assumedfor total POM group in NATA 1996:5% of risk from Benzo(a)pyrene72002POM, Group 2: No URE dataPOM_Group_2_nodataGroup contains individual POM speciesthat have no URE associated withthem5.5 * 10-5Assume same URE as is used forunspeciated POM (71002)73002POM, Group 3: 5e-2<URE<5e-1POM_Group_3_vhigh1Group contains individual POM speciesin which the UREs are between:5e-2<URE<5e-11 * 10-1Midpoint of range74002POM, Group 4: 5e-3<URE<5e-2POM_Group_4_high2Group contains individual POM speciesin which the UREs are between:5e-3<URE<5e-21 * 10-2Midpoint of range75002POM, Group 5: 5e-4<URE<5e-3POM_Group_5_mhigh3Group contains individual POM speciesin which the UREs are between:5e-4<URE<5e-31 * 10-3Midpoint of range; note this is thegroup that contains Benzo(a)pyrene76002POM, Group 6: 5e-5<URE<5e-4POM_Group_6_med4Group contains individual POM speciesin which the UREs are between:5e-5<URE<5e-41 * 10-4Midpoint of range77002POM, Group 7: 5e-6<URE<5e-5POM_Group_7_mlow5Group contains individual POM speciesin which the UREs are between:5e-6<URE<5e-51 * 10-5Midpoint of range78002POM, Group 8: Unspeciated 7-PAHPOM_Group_8_Unspec_7Group contains pollutant reported as“7-PAH”2 * 10-4Assume same URE as was used for7-PAH from 1996 NATA, 18% of ofrisk from Benzo(a)pyrene

### APPROACH FOR MODELING POM

Table 2 shows the assignment of the POM in the 1999 NEI to the eight POM modeled pollutant groups. Note that summaries of POM in the 1999 NEI are provided for a different set of groups that don’t have a one-to-one relationship to the modeled groups. Column 4 of Table 2 shows how the 1999 NEI POM groups relate to the modeled groups. Table 2 also shows the nationwide (50 States, Puerto Rico and Hawaii) emissions of the various POM reported in the inventory 1



### . In Table 2, the pollutant called “16-PAH-7-PAH” was created from the 1999 NEI version 3 prior to modeling by subtracting 7-PAH (inventory po llutant code 40) from 16-PAH (inventory pollutant code 75). It was assigned a pollutant code of 75040, but because it is not in the NEI, it does not have an associated “POM category in 1999 NEI” entry.

Table 2. Mapping of NEI HAPs belonging to POM into the modeled POM groups And 1999 NEI National-level Emissions

POM group Pollutant code Description of Pollutant POM category in 1999 NEI Pointinventtory Nonpointinventory Onroadinventory Nonroadinventory Total Tons/Year

71002 103 Benz(a)Anthracene/Chrysene POM as 7-PAH 0 0.00267 0 0 0.00267

71002 234 total PAH POM as 7-PAH 54.85 976.96 0 0 1031.81

71002 246 Polycyclic Organic Matter POM as 7-PAH 3314.58 644.09 0 0 3958.67

71002 40 16-PAH POM as non-15 PAH 13.12 320.38 0 0 333.5 71002 75040 16PAH-7PAH 0 132.42 0 1.4012 133.8212

72002 120127 Anthracene POM as 15-PAH 38.1 332.92 31.91 15.2 418.13

72002 129000 Pyrene POM as 15-PAH 399.16 617.33 46.37 35.2 1098.06

72002 191242 Benzo[g,h,i,]perylene POM as 15-PAH 2.04 283.7 9.35 9.91 305

72002 192972 Benzo[e]pyrene POM as non-15 PAH 0.59 184.69 0 0 185.28

72002 195197 Benzo(c)phenanthrene POM as non-15 PAH 0 152.71 0 0 152.71

72002 198550 Perylene POM as non-15 PAH 2.3 35.4 0 0 37.7



### 1 Also note that the non-point inventory benzo-a-pyrene emissions in Table 2, which are based on the 1999 NEI version 3.0 (Fall 2003) are greatly overestimated. Afte r the initial ASPEN modeling was completed, it was found that the State of Oregon mistakenly used a wrong emissi on factor for estimating its wildfire emissions (SCC = 2810001000) that caused an overestimation of benzo(a)pyrene by about factor of 4. The ASPEN results were adjusted to reflect this error, but the emissions were not changed.

### APPROACH FOR MODELING POM

POM group Pollutant code Description of Pollutant POM category in 1999 NEI Pointinventtory Nonpointinventory Onroadinventory Nonroadinventory Total Tons/Year

72002 203123 Benzo(g,h,i)Fluoranthene POM as non-15 PAH 0 7.5 0 0 7.5

72002 203338 Benzo(a)fluoranthene POM as non-15 PAH 0.00001 7 101.81 0 0 101.81

72002 206440 Fluoranthene POM as 15-PAH 231.63 523.85 33.26 30.49 819.23

72002 208968 Acenaphthylene POM as 15-PAH 1.42 1744.67 139.2 66.04 1951.33

72002 2381217 1-Methylpyrene POM as non-15 PAH 0 354.36 0 0 354.36

72002 2422794 12-Methylbenz(a)Anthracene POM as non-15 PAH 0 0.51 0 0 0.51

72002 247 Methylbenzopyrenes POM as non-15 PAH 0.00003 5 114.51 0 0 114.51

72002 248 Methylchrysene POM as non-15 PAH 0 305.61 0 0 305.61

72002 2691418 1 Methylanthracene POM as non-15 PAH 0.63 322.43 0 0 323.06

72002 5683273 6 Benzofluoranthenes POM as 7-PAH 0.03 205.14 0 0 205.17

72002 779022 9-Methylbenz(a)Anthracene POM as non-15 PAH 0 1.01 0 0 1.01

72002 832699 1-Methylphenanthrene POM as non-15 PAH 0 7.58 0 0 7.58

72002 83329 Acenaphthene POM as 15-PAH 39.77 309.59 26.42 26.07 401.85

72002 85018 Phenanthrene POM as 15-PAH 175.02 1085.44 90.99 100.74 1452.19

72002 86737 Fluorene POM as 15-PAH 59.73 254.13 55.29 51.32 420.47

72002 91576 2-Methylnaphthalene POM as non-15 PAH 9.53 20.76 0 0 30.29

72002 91587 2-Chloronaphthalene POM as non-15 PAH 0.09 0.00000 0737 0 0 0.090001

73002 57976 7,12- Dimethylbenz[a]anthracene POM as non-15 0.1 1.93 0 0 2.03

### APPROACH FOR MODELING POM

POM group Pollutant code Description of Pollutant POM category in 1999 NEI Pointinventtory Nonpointinventory Onroadinventory Nonroadinventory Total Tons/Year PAH

74002 189559 Dibenzo[a,i]pyrene POM as non-15 PAH 0.00000 176 0 0 0 1.76E-06

74002 189640 Dibenzo[a,h]pyrene POM as non-15 PAH 0.00001 69 0 0 0 1.69E-05

74002 56495 3-Methylcholanthrene POM as non-15 PAH 0.00016 0.25 0 0 0.25016

75002 192654 Dibenzo[a,e]Pyrene POM as non-15 PAH 0.00095 4 0 0 0 0.000954

75002 3697243 5-Methylchrysene POM as non-15 PAH 0.00021 0.00000 405 0 0 0.000214

75002 50328 Benzo[a]pyrene(7PAH) POM as 7-PAH 15.67 1073.9 4.84 3.19 1097.6

75002 53703 Dibenzo[a,h]anthracene POM as 7-PAH 0.87 7.12 0.00098 5 0.07 8.060985

76002 102 Benzo[b+k]fluoranthene POM as 7-PAH 0.01 0.19 0 0 0.2

76002 193395 Indeno[1,2,3-c,d]pyrene POM as 7-PAH 0.43 178.2 2.58 3 184.21

76002 205823 B[j]fluoranthen POM as non-15 PAH 0.00136 3 0 0 0 0.001363

76002 205992 Benzo[b]fluoranthene POM as 7-PAH 4.95 85.87 5.32 2.57 98.71

76002 207089 Benzo[k]fluoranthene POM as 7-PAH 2.07 143.53 5.32 2.37 153.29

76002 224420 Dibenzo[a,j]Acridine POM as non-15 PAH 0.0001 0 0 0 0.0001

76002 56553 Benz[a]anthracene POM as 7-PAH 109.4 433.97 7.97 4.85 556.19

77002 218019 Chrysene POM as 7-PAH 30.23 388.2 4.18 3.09 425.7

78002 75 7-PAH POM as 7-PAH 66.26 39.96 0 1.38069 107.6007