### APPROACH FOR MODELING POM

1999 and 2002 NATA Approach

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 and 2002 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 and 2002 NATA we have eight distinct groups. See Table 1 for the bases for determining into which group an individual PAH would fall.

There are three main NEI improvements related to POM. First, a larger quantity of the1999 and 2002 NEI emissions are speciated into individual POM compounds. Second, doublecounting of POM groups from individual stack s in the point source inventory has been eliminated. Third, naphthalene is inventoried as a separate HAP and is not included nor summarized in any PAH group. Different POM were assigned to non-overlapping groups for which we can associate similar inhalation risks based on the unit risk estimate (URE). Unit risk estimates were obtained from the toxicity table found at the website http://www.epa.gov/ttn/atw/toxsource/table1.pdf Table 1 in this document shows the 8 POM groups and the associated URE assignments. The only difference between the list used in the 1999 NATA versus the current list is the addition of more PAHs which were reported to the

2002 NEI.Table 1. POM groups for the 1999 and 2002 National Scale Air Toxics AssessmentPOMGROUPCodeGroup NameDescription of GroupURE *Bases for URE71002Group1:Contains unspeciated POM;no URE5.5 x 10-5Assume same URE as wasassumed for total POM groupin NATA 1996: 5% of riskfrom Benzo(a)pyrene72002Group2Contains individual POM;no URE5.5 x 10-5Assume same URE as is usedfor unspeciated POM (71002)73002Group 3Contains individual POM;UREs between:5 x 10-2< URE < 5 x 10-11 x 10-1Midpoint of range(100x the BaP URE)74002Group4Contains individual POM;UREs between:5 x 10-3< URE < 5 x 10-21 x 10-2Midpoint of range(10x the BaP URE)75002Group5Contains individual POM;UREs between:5 x 10-4< URE < 5 x 10-31 x 10-3Midpoint of range(equal to BaP URE)76002Group6Contains individual POM;UREs between:5 x 10-5< URE <5 x 10-41 x 10-4Midpoint of range(0.1x the BaP URE)77002Group7Contains individual POM;UREs between:5 x 10-6< URE < 5 x 10-51 x 10-5Midpoint of range(0.01x the BaP URE)78002Group 8Contains HAPs reported as “7-PAH”2 x 10-4Used URE from 7-PAH in 1996NATA,( 18% of BaP URE)* These UREs are based on the potency of Benzo-a-pyrene (BaP). Each group represents a different percent of the BaP URE. Forexample,group 1 has a URE of 5.5 x 10-5which is 5% of the BaP URE (BaP URE = .0011 X .05 = .000055).

### Table 2. List of PAH HAPs included in the 2002 NATA
Group
Code Group Name Description of Pollutant

71002 Group 1 Benzo(a)anthracene/chrysene

74002 Group 4 1,6-Dinitropyrene

74002 Group 4 1,8-Dinitropyrene

72002 Group 2 12-Methylbenz(a)anthracene

71002 Group 1 15-PAH

71002 Group 1 16-PAH

71002 Group 1 16-PAH with HAPs in 7-PAH group removed

72002 Group 2 1-Methylphenanthrene

72002 Group 2 1-Methylpyrene

77002 Group 7 2-Nitrofluorene

72002 Group 2 2-Chloronaphthalene

72002 Group 2 2-Methylnaphthalene

74002 Group 4 3-Methylcholanthrene

75002 Group 5 5-Methylchrysene

74002 Group 4 6-Nitrochrysene

73002 Group 3 7,12-Dimethylbenz[a]anthracene

78002 Group 8 7-PAH

72002 Group 2 9-Methylbenz(a)anthracene

72002 Group 2 Acenaphthene

72002 Group 2 Acenaphthylene

72002 Group 2 Anthracene

76002 Group 6 Benzo[j]fluoranthene

76002 Group 6 Benz[a]anthracene

72002 Group 2 Benzo(a)fluoranthene

72002 Group 2 Benzo(c)phenanthrene

72002 Group 2 Benzo(g,h,i)fluoranthene

75002 Group 5 Benzo[a]pyrene(7-PAH)

76002 Group 6 Benzo[b]fluoranthene

76002 Group 6 Benzo[b+k]fluoranthene

72002 Group 2 Benzo[e]pyrene

72002 Group 2 Benzo[g,h,i,]perylene

76002 Group 6 Benzo[k]fluoranthene

72002 Group 2 Benzofluoranthenes

77002 Group 7 Chrysene

71002 Group 1 Coal Tar

75002 Group 5 Dibenzo[a,e]Pyrene

75002 Group 5 Dibenzo[a,h]anthracene

74002 Group 4 Dibenzo[a,h]pyrene

74002 Group 4 Dibenzo[a,i]pyrene

76002 Group 6 Dibenzo[a,j]acridine

71002 Group 1 Extractable Organic Matter

72002 Group 2 Fluoranthene

72002 Group 2 Fluorene

76002 Group 6 Indeno[1,2,3-c,d]pyrene

72002 Group 2 Methylanthracene

72002 Group 2 Methylbenzopyrene

75002 Group 5 Methylchrysene

72002 Group 2 PeryleneGroup
Code Group Name Description of Pollutant

72002 Group 2 Phenanthrene

71002 Group 1 Polycyclic Organic Matter

72002 Group 2 Pyrene

71002 Group 1 Total PAH