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 the 

1999 and 2002 NEI emissions are speciated into individual POM compounds. Second, doublecounting of POM groups from individual stacks 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 Assessment 

POM 

GROUP 

Code 

Group Name Description of Group URE * B

71002 Group 1: Contains unspeciated POM; no URE 5.5 x 10-5

Assum

assume

in NA

fro

72002 Group 2 Contains individual POM; no URE 5.5 x 10-5 Assum

for uns

73002 Group 3 

Contains individual POM; 

 UREs between: 

5 x 10-2 < URE < 5 x 10-1

1 x 10-1 M

(1

74002 Group 4 

Contains individual POM; 

 UREs between: 

5 x 10-3 < URE < 5 x 10-2

1 x 10-2 M

(1

75002 Group 5 

Contains individual POM; 

 UREs between: 

5 x 10-4 < URE < 5 x 10-3

1 x 10-3 M

(e

76002 Group 6 

Contains individual POM; 

 UREs between: 

5 x 10-5 < URE <5 x 10-4

1 x 10-4 M

(0

77002 Group 7 

Contains individual POM; 

 UREs between: 

5 x 10-6 < URE < 5 x 10-5

1 x 10-5 M

(0.

78002 Group 8 Contains HAPs reported as “7-PAH” 2 x 10-4

Used U

( 

* These UREs are based on the potency of Benzo-a-pyrene (BaP). Each group represents a different percent of the BaP group 1 has a URE of 5.5 x 10-5 which 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 Perylene 
Group 

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