United States

Environmental Protection

Agency

Air and Radiation EPA420-R-02-029

November 2002

Technical Description of the

Toxics Module for

MOBILE6.2 and Guidance on

Its Use for Emission

Inventory Preparation

 Printed on Recycled Paper
EPA420-R-02-029

November 2002

Technical Description of the Toxics Module for

MOBILE6.2 and Guidance on Its Use for

Emission Inventory Preparation

Rich Cook

Edward L. Glover

Assessment and Standards Division

Office of Transportation and Air Quality

U.S. Environmental Protection Agency

NOTICE

This technical report does not necessarily represent final EPA decisions or positions.

It is intended to present technical analysis of issues using data that are currently available.

The purpose in the release of such reports is to facilitate the exchange of

technical information and to inform the public of technical developments which

may form the basis for a final EPA decision, position, or regulatory action.
Table of Contents

1.0 Background..........................................................................................................................1

2.0 Calculation of Toxic Emission Rates...................................................................................2

2.1 Exhaust Emissions for Benzene, 1,3-Butadiene, Formaldehyde, Acetaldehyde, 

and MTBE................................................................................................................2

2.2 Exhaust Emissions for Acrolein.............................................................................11

2.3 Evaporative Emissions for Benzene and MTBE.....................................................12

2.4 User Defined Air Toxic Pollutants.........................................................................12

3.0 Input Parameter Data...........................................................................................................13

3.1 Sources of Fuel Parameter Data for Modeling Base Years.....................................14

3.1.1. The Alliance of Automobile Manufacturers North American 

Gasoline and Diesel Fuel Survey................................................................14

3.1.2. TRW Petroleum Technologies Survey.......................................................15

3.1.3. Reformulated Gasoline Surveys.................................................................15

3.2 Weighting Fuel Parameter Data from Surveys.......................................................16

3.3 Projecting Fuel Parameter Data to Future Years.....................................................17

3.4 Fuel Parameter Data from Recent EPA Toxic Emissions Modeling......................17

4.0 Results of the MOBILE6.2 Model......................................................................................18

4.1 Comparison of Calendar Year Fleet Average Emission Factors to 

MOBTOX5b Emission Factors from 1999 Study...................................................18

4.2 Comparison of MOBILE6.2 and MOBTOX5b Results by Vehicle Class 

and Model Year......................................................................................................21

5.0 References..........................................................................................................................26
Acronyms

ETBE = Ethyl tertiary butyl ether

ETOH = Ethanol

FTP = Federal Test Procedure

HAP = Hazardous Air Pollutant

MOBTOX = EPA’s first highway vehicle toxic emission factor model, used in a 1993

study

MOBTOX5b = EPA’s revised highway vehicle toxic emission factor model, used in several

EPA assessments, beginning in 1999

MOBILE = EPA’s emission factor model for HC, CO, and NOx. PM and toxics are being

added to the most recent version, MOBILE6

MTBE = Methyl tertiary butyl ether

NEI = National Emissions Inventory

NSATA = National-Scale Air Toxics Assessment

TAME = Tertiary amine methyl ether

TOG = Total organic gases

UC = Unified Cycle
1

1.0 Background

This document describes the methodology used to estimate air toxic emission rates in the

toxics module for MOBILE6 (MOBILE6.2), describes the sources of data used, and provides

users with guidance on how to obtain data required as input parameters for the model. The

document also compares some MOBILE6.2 results to results using a previous highway mobile

source toxics emission factor model, MOBTOX5b.

EPA has developed two previous toxic emission factor models for highway mobile

sources. These models were developed primarily for internal assessment purposes and neither

were officially released. However, both were released in draft form for use outside of EPA. The

first model, MOBTOX, was developed as part of an assessment of toxic emissions, exposure,

and risk, released in 1993 as the Motor Vehicle-Related Air Toxics Study.1 This model applied

toxic fractions on a technology group basis to total organic gas (TOG) gram per mile emission

factors to calculate air toxic emission factors. The TOG emission factors were derived from a

version of MOBILE4.1 modified to account for control programs mandated by the Clean Air Act

Amendments of 1990. Using MOBTOX, average nationwide in-use toxic emission factors could

be estimated for benzene, 1,3-butadiene, formaldehyde, and acetaldehyde, for a number of

evaluation years and possible control scenarios. 

Several years later, EPA developed a new toxic emission factor model, MOBTOX5b.2, 3, 4

The model was used in several EPA assessments, including the Regulatory Impact Analysis for

the Tier 2/Gasoline Sulfur Final Rule,5 the Regulatory Impact Analysis for the 2007 DieselSulfur Rule, 6

 the Technical Support Document for the Mobile Source Air Toxics Rule,7 and the

1996 National Toxics Inventory and National Scale Air Toxics Assessment.8, 9 MOBTOX5b

includes MOBILE6 model enhancements and represents a substantial improvement over the

preliminary version used in the 1993 study. The model has the capability to account for

differences in exhaust toxic fractions of TOG between normal and high emitting vehicles in

calculating emission rates. Moreover, the model accounts for the impacts of aggressive driving

and air conditioning usage on toxics. The impacts of fuel reformulation programs and changes in

vehicle emission control technology can also be addressed with the model. The model accounts

for the impacts of specific fuel parameters included in the Complex Model for reformulated

gasoline and a draft fuel effects model for MTBE.10, 11 Finally, whereas separate runs had to be

done for each toxic with the first version of MOBTOX, MOBTOX5b allows the user to model

benzene, formaldehyde, acetaldehyde, 1,3-butadiene, and MTBE in one run. Unfortunately, the

input structure of MOBTOX5b is quite complicated and the model is difficult to use. This is

because the model consists of several separate software tools that are not fully integrated into the

MOBILE framework. 

 Combining the air toxic and MOBILE models is a recommendation of the National

Academy of Science Research Council’s review of MOBILE.12 MOBILE6.2 fulfills this need,

simplifies the modeling process, and provides a single, consistent interface for modeling vehicle

pollutants. The MOBILE6 toxics module fully integrates the calculation of highway vehicle air
2

toxic emission factors for benzene, 1,3-butadiene, formaldehyde, acetaldehyde, acrolein, and

MTBE into the modeling framework. It also integrates toxic emissions data and algorithms from

EPA’s Complex Model for Reformulated Gasoline. Moreover, the model can estimate emissions

of other hazardous air pollutants (HAPs) based on user provided information.

2.0 Calculation of Toxic Emission Rates

MOBILE6.2 explicitly estimates emissions for the following compounds:

1) Benzene – A known human carcinogen that causes leukemia and other blood disorders

2) 1,3-Butadiene – Causes excess incidence of leukemia in humans, and also a variety of

reproductive and developmental effects in mice and rats

3) Formaldehyde – A likely human carcinogen that causes nasal tumors in rats, and is a

respiratory irritant

4) Acetaldehyde – A likely human carcinogen that causes nasal tumors in rats, and is a

respiratory irritant

5) Acrolein – A respiratory tract irritant

6) MTBE – Causes kidney lesions, swelling around the eyes and increased prostration in

rats. It is also associated with tumors of kidneys and testes in male rats and liver tumors

in female mice

The above compounds, except for MTBE, dominate risk from mobile sources, based on

results of the recent National-Scale Air Toxics Assessment.8 Benzene and MTBE are found in

both exhaust and evaporative emissions; the others are constituents of exhaust only. Emission

factors are reported according to whether they are exhaust, crankcase, diurnal, hot soak, running

loss, resting loss or refueling loss emissions. MOBILE6.2 also distinguishes between exhaust

start and running emissions for some light duty vehicle classes. Emissions are reported by

vehicle class for the 28 vehicle types included in MOBILE6 (Table 2.1). MOBILE6.2 also has a

command (ADDITIONAL HAPS) which allows the user to enter emission factors or air toxic to

TOG ratios for additional air toxic pollutants. This command is described in more detail in

Section 2.4.

2.1 Exhaust Emissions for Benzene, 1,3-Butadiene, Formaldehyde, Acetaldehyde, and

MTBE

The exhaust component of the toxics module multiplies the air toxic to TOG ratio by the

MOBILE6.2 TOG (or volatile organic compound, VOC, for some technology groups) estimates

to produce an air toxic emission estimate in MOBILE6.2. For light-duty gasoline vehicles, the
3

Table 2.1. MOBILE6 Vehicle Classifications

Number Abbreviation Description

1 LDGV Light-Duty Gasoline Vehicles (Passenger Cars)

2 LDGT1 Light-Duty Gasoline Trucks 1 (0-6,000 lbs. GVWR, 0-3,750 lbs. LVW)

3 LDGT2 Light-Duty Gasoline Trucks 2 (0-6,001 lbs. GVWR, 3,751-5750 lbs. LVW)

4 LDGT3 Light-Duty Gasoline Trucks 3 (6,001-8500 lbs. GVWR, 0-5750 lbs. ALVW)

5 LDGT4 Light-Duty Gasoline Trucks 4 (6,001-8500 lbs. GVWR, 5,751 lbs. and greater A LVW)

6 HDGV2b Class 2b Heavy-Duty Gasoline Vehicles (8501-10,000 lbs. GVWR)

7 HDGV3 Class 3 Heavy-Duty Gasoline Vehicles (10,001-14,000 lbs. GVWR)

8 HDGV4 Class 4 Heavy-Duty Gasoline Vehicles (14,001-16,000 lbs. GVWR)

9 HDGV5 Class 5 Heavy-Duty Gasoline Vehicles (16,001-19,500 lbs. GVWR)

10 HDGV6 Class 6 Heavy-Duty Gasoline Vehicles (19,501-26,000 lbs. GVWR)

11 HDGV7 Class 7 Heavy-Duty Gasoline Vehicles (26,001-33,000 lbs. GVWR)

12 HDGV8a Class 8a Heavy-Duty Gasoline Vehicles (33,001-60,000 lbs. GVWR)

13 HDGV8b Class 8b Heavy-Duty Gasoline Vehicles (>60,000 lbs. GVWR)

14 LDDV Light-Duty Diesel Vehicles (Passenger Cars)

15 LDDT12 Light-Duty Diesel Trucks 1and 2 (0-6,000 lbs. GVWR)

16 HDDV2b Class 2b Heavy-Duty Diesel Vehicles (8501-10,000 lbs. GVWR)

17 HDDV3 Class 3 Heavy-Duty Diesel Vehicles (10,001-14,000 lbs. GVWR)

18 HDDV4 Class 4 Heavy-Duty Diesel Vehicles (14,001-16,000 lbs. GVWR)

19 HDDV5 Class 5 Heavy-Duty Diesel Vehicles (16,001-19,500 lbs. GVWR)

20 HDDV6 Class 6 Heavy-Duty Diesel Vehicles (19,501-26,000 lbs. GVWR)

21 HDDV7 Class 7 Heavy-Duty Diesel Vehicles (26,001-33,000 lbs. GVWR)

22 HDDV8a Class 8a Heavy-Duty Diesel Vehicles (33,001-60,000 lbs. GVWR)

23 HDDV8b Class 8b Heavy-Duty Diesel Vehicles (>60,000 lbs. GVWR)

24 MC Motorcycles (Gasoline)

25 HDGB Gasoline Buses (School, Transit and Urban)

26 HDDBT Diesel Transit and Urban Buses

27 HDDBS Diesel School Buses

28 LDDT34 Light-Duty Diesel Trucks 3 and 4 (6,001-8,500 lbs. GVWR)

product is then multiplied by an off-cycle adjustment factor, explained in more detail below, 

which accounts for the difference in toxic fractions between Federal Test Procedure (FTP) and

Unified Cycle (UC) operation. Mathematically, it is represented by:

Ratio = g/mi Toxic from Air Toxic Module / g/mi TOG from Air Toxic Module (1)

Final Toxic Emission Factor = Ratio * TOG emissions from MOBILE6*ADJTOX UC/FTP (2)

Toxic to TOG ratios vary by technology group, vehicle type, whether a vehicle is a normal or

high emitter (same definition as MOBILE6), and fuel characteristics. Ratios for individual

technology group/vehicle type/emitter class combinations are determined using a series of

algorithms which calculate the ratios based on fuel parameter inputs. Since toxic emission rates

are a product of toxic to TOG ratios and TOG emission rates, anything that reduces TOG will

also result in toxic emission reductions.
4

Benzene, 1,3-butadiene, formaldehyde, and acetaldehyde exhaust emissions from lightduty gasoline vehicles with three-way or three-way plus oxidation catalysts were estimated using

algorithms developed for the Complex Model for Reformulated Gasoline.10 For MTBE, a draft

fuel effects model based on the Complex Model database was used.11 These algorithms were

also used in MOBTOX5b. It should be noted that the sulfur effects terms in the algorithms were

not used; instead, sulfur impacts on toxic emissions were assumed to be proportional to the sulfur

impacts on total VOC estimated by MOBILE6. The Complex Model algorithms are based on

data from vehicles representing a 1990 model year fleet. Toxic to TOG ratios for advanced

technology vehicles running on a given fuel, such as California low emission (LEV) and Tier 2

vehicles, could be different than ratios based on the fleet in the Complex Model database.

However, test data are far too limited to develop algorithms for advanced technology vehicles. 

Toxic emissions data from a small number of California Low Emission Vehicles13 suggest toxic

to TOG ratios from vehicles are similar to those of vehicles in the Complex Model database, but

additional testing and analysis are needed. 

For benzene, 1,3-butadiene, formaldehyde, and acetaldehyde, the algorithms are based on

about 1800 observations; for MTBE they are based on a nearly 900 observations. These

algorithms are applied by stratifying the light-duty gasoline fleet into ten Technology Groups and

applying the algorithms individually to each group (this is known as the unconsolidated Complex

Model). The ten groups are formed as a combination of fuel system, catalyst type, Air injection

(y/n toggle), EGR, and Normal / High emitter status. These groups are listed in Table 2.2. The

first nine groups represent only normal emitting vehicles (same definition as MOBILE6). The

tenth group represents all of the high emitters, regardless of technology. 

Table 2.2. Technology Groups in the Complex Model for Reformulated Gasoline

Technology Group Definitions

Technology Group Fuel System Catalyst Air Injection EGR

1 PFI 3WAY NO AIR EGR

2 PFI 3WAY NO AIR NO EGR

3 TBI 3WAY NO AIR EGR

4 PFI 3WAY + OX AIR EGR

5 PFI 3WAY AIR EGR

6 TBI 3WAY AIR EGR

7 TBI 3WAY + OX AIR EGR

8 TBI 3WAY NO AIR NO EGR

9 CARB 3WAY + OX AIR EGR

High Emitters ALL ALL ALL ALL

PFI = port fuel Injection, TBI = throttle body injection, CARB = carburetor, 3WAY = three way catalyst, 3WAY +

OX = three way plus oxidation catalyst, ERG = exhaust gas recirculation
5

The Complex Model algorithms can be found in the regulatory impact analysis for the

1993 Reformulated Gasoline Rule.10 Separate toxic ratios are calculated for each of the groups

and weighted together by the fraction of the fleet attributable to each technology group in

MOBILE6. These fractions can be obtained from the MOBILE6 TGS array.14 

For light-duty gasoline vehicles with oxidation catalysts only or no catalysts, toxic to

VOC ratios are determined using algorithms derived from a more limited data set from about 50

vehicles tested on a baseline fuel and a small number tested on reformulated fuels. Data were not

available to develop algorithms for ETBE and TAME blends; thus, the algorithms for ethanol

oxygenated gasoline were used for ETBE blends, and the algorithms for MTBE oxygenated

gasoline were used for MTBE blends. Algorithms for light-duty diesel vehicles and heavy-duty

engines are based on only a few tests. These algorithms for diesel vehicles and engines do not

include any impacts of fuel parameters. Although diesel fuel parameters, such as cetane, do seem

to have an impact on toxics emissions, data are inadequate to quantify them.15 No speciation data

were available for highway motorcycles; thus, algorithms for non-catalyst light-duty vehicles

were used, since most motorcycles in the fleet do not have catalytic converters. The algorithms

for older technology light-duty gasoline, light-duty diesel, and heavy-duty vehicles were also

used in MOBTOX5b and are provided in Table 2.3. The specific studies which comprise the

data set for these algorithms are described in Appendix D of the 1999 document, “Analysis of the

Impacts of Control Programs on Motor Vehicle Toxics Emissions and Exposure in Urban Areas

and Nationwide.”3

For light-duty gasoline vehicles, toxic to TOG ratios developed using the algorithms

described above were also adjusted to account for the impacts of aggressive driving. These

adjustments were applied to start and running emissions, as well as all speeds and roadway types. 

Adjustments to account for aggressive driving were based on analysis of data from vehicles

running on both the Federal Test Procedure (FTP) Cycle, which does not account for aggressive

driving, and the Unified Cycle (UC), which does. The adjustment is applied as shown previously

in equation 2. These adjustments were developed for MOBTOX5b, and are given in Table 2.4. 

The adjustments are based on an analysis of UC and FTP emissions data from 12 vehicles

collected by the California Air Resources Board. Details of the analysis of these data can be

found in Appendix G of the 1999 document, “Analysis of the Impacts of Control Programs on

Motor Vehicle Toxics Emissions and Exposure in Urban Areas and Nationwide.”3

 There are

separate adjustments for normal and high emitters. 
6

Table 2.3 Exhaust Toxic Fraction Equations for LDGV with Oxidation Catalysts, Non-Catalyst LDGV, HDGV, LDDV and HDDV

Vehicle Class/Catalyst

Baseline Gasoline MTBE Gasoline EtOH Gasoline

BenzeneLDGV andLDGT/oxcat

Bz/TOG = (0.8551* (vol. % Bz) +0.12198 * (vol. % Arom.) -1.1626)/100

Bz/TOG = (0.8551* (vol. % Bz) +0.12198 * (vol. % Arom.) -1.1626)/100

Bz/TOG = (0.8551* (vol. % Bz) +0.12198 * (vol. % Arom.) -1.1626)/100

LDGV andLDGT/noncatMC

Bz/TOG = (0.8551* (vol. % Bz) +0.12198 * (vol. % Arom.) -1.1626)/100

Bz/TOG = (0.8551* (vol. % Bz) +0.12198 * (vol. % Arom.) -1.1626)/100

Bz/TOG = (0.8551* (vol. % Bz) +0.12198 * (vol. % Arom.) -1.1626)/100

HDGV/noncat Bz/TOG = (0.8551* (vol. % Bz) +

0.12198 * (vol. % Arom.) -1.1626)/100

Bz/TOG = (0.8551* (vol. % Bz) +0.12198 * (vol. % Arom.) -1.1626)/100

Bz/TOG = (0.8551* (vol. % Bz) +0.12198 * (vol. % Arom.) -1.1626)/100

HDGV/cat Bz/TOG = (1.077 + 0.7732*(volume

% benzene) + 0.0987 * (volume %aromatics - volume % benzene))/100

Bz/TOG = (1.077 + 0.7732*(volume% benzene) + 0.0987 * (volume %aromatics - volume % benzene))/100

Bz/TOG = (1.077 + 0.7732*(volume% benzene) + 0.0987 * (volume %aromatics - volume % benzene))/100

LDDV Bz/TOG = 0.0200
7

Vehicle Class/Catalyst

Baseline Gasoline MTBE Gasoline EtOH Gasoline

LDDT Bz/TOG = 0.0200HDDV Bz/TOG = 0.0105FormaldehydeLDGV andLDGT/oxcatHDGV/cat

Form/TOG = 0.0151 Form/TOG = 0.0151 + ((0.0151 *

1.2082)*(wt % MTBE/2.7))

Form/TOG = 0.0151 + ((0.0151 *0.3350)*(wt % EtOH/3.5))

LDGV andLDGT/noncatMC

Form/TOG = 0.0224 Form/TOG = 0.0224 + ((0.0224 *

0.4336)*(wt % MTBE/2.7))

Form/TOG = 0.0224 + ((0.0224 *0.1034)*(wt % EtOH/3.5))

HDGV/noncat Form/TOG = 0.0347 Form/TOG = 0.0347 + ((0.0347 *

0.1259)*(wt % MTBE/2.7))

Form/TOG = 0.0347 + ((0.0347 *0.1034)*(wt % EtOH/3.5))

LDDV Form/TOG = 0.0386LDDT Form/TOG = 0.0386HDDV Form/TOG = 0.0782
8

Vehicle Class/Catalyst

Baseline Gasoline MTBE Gasoline EtOH Gasoline

AcetaldehydeLDGV andLDGT/oxcatHDGV/cat

Acet/TOG = 0.0047 Acet/TOG = 0.0047 + ((0.0047 *

0.2556)*(wt % MTBE/2.7))

Acet/TOG = 0.0047 + ((0.0047 *2.1074)*(wt % EtOH/3.5))

LDGV andLDGT/noncatMC

Acet/TOG = 0.0060 Acet/TOG = 0.0060 + ((0.0060 *

0.2303)*(wt % MTBE/2.7))

Acet/TOG = 0.0060 + ((0.0060 *1.1445)*(wt % EtOH/3.5))

HDGV/noncat Acet/TOG = 0.0067 Acet/TOG = 0.0067 Acet/TOG = 0.0067 + ((0.0067 *

1.1445)*(wt % EtOH/3.5))

LDDV Acet/TOG = 0.0123LDDT Acet/TOG = 0.0123HDDV Acet/TOG = 0.0288
9

Vehicle Class/Catalyst

Baseline Gasoline MTBE Gasoline EtOH Gasoline

1,3-ButadieneLDGV andLDGT/oxcat

Buta/TOG = 0.0044 Buta/TOG = 0.0044 + ((0.0044 * -

0.2227)*(wt % MTBE/2.7))

Buta/TOG = 0.0044 + ((0.0044* -0.2804)*(wt % EtOH/3.5))

LDGV andLDGT/noncatMC

Buta/TOG = 0.0092 Buta/TOG = 0.0092 + ((0.0092 * 

0.1517)*(wt % MTBE/2.7))

Buta/TOG = 0.0092 + ((0.0092 * 0.1233)*(wt % EtOH/3.5))

HDGV/noncat Buta/TOG = 0.0074 Buta/TOG = 0.0074 + ((0.0074 * -

0.2172)*(wt % MTBE/2.7))

Buta/TOG = 0.0074 + ((0.0074 * 0.1233)*(wt % MTBE/2.7))

HDGV/cat Buta/TOG = 0.0029 Buta/TOG = 0.0029 + ((0.0029 * -

0.3233)*(wt % MTBE/2.7))

Buta/TOG = 0.0029 + ((0.0029 * -0.1188)*(wt % EtOH/3.5))

LDDV Buta/TOG = 0.0090LDDT Buta/TOG = 0.0090HDDV Buta/TOG = 0.0061
10

Vehicle Class/Catalyst

Baseline Gasoline MTBE Gasoline EtOH Gasoline

MTBELDGV andLDGT/oxcat

MTBE/TOG = 0.0464*(wt %MTBE/2.7)

LDGV andLDGT/noncatMC

MTBE/TOG = 0.0333*(wt %MTBE/2.7)

HDGV/noncat MTBE/TOG = 0.0209*(wt %

MTBE/2.7)

HDGV/cat MTBE/TOG = 0.0155*(wt %

MTBE/2.7)
11

Table 2.4. Light-Duty Gasoline Vehicle Off-Cycle Adjustments for Toxic/TOG Fractions

Toxic Compound Normal Hydrocarbon Emitter High Hydrocarbon Emitter

Benzene 1.315 1.126

1,3-Butadiene 1.037 0.708

MTBE 0.825 0.965

Formaldehyde 1.163 0.894

Acetaldehyde 1.020 0.919

2.2. Exhaust Emissions for Acrolein

Acrolein emissions were not included in MOBTOX5b, but the pollutant is included

explicitly in MOBILE6.2 because it was identified as a national non-cancer hazard driver in the

the National-Scale Air Toxics Assessment (more than 10% of the U.S. population lives in census

tracts where the typical exposure exceeded the reference concentration for this compound),8 and

because highway mobile sources are a large contributor to the overall inventory in 1996.7

Acrolein fractions of TOG used in the model are the same as those used in the 1996 National

Toxics Inventory. The documentation for that inventory describes the data sources used to

develop them.9

 The fractions used are provided in Table 2.5. They are obtained from vehicles

running on a baseline gasoline or diesel fuel and the model does not account for potential impacts

of fuel reformulation. 

Table 2.5. Acrolein/TOG fractions Used in MOBILE6.2

Vehicle Category Acrolein/TOG Fraction

LDGV 0.0006

LDGT 0.0006

HDGV – Catalyst 0.0005

HDGV – No Catalyst 0.0045

LDDV 0.0035

HDDV 0.0035

MC 0.0006
12

2.3 Evaporative Emissions for Benzene and MTBE

Algorithms from the Complex Model for Reformulated Gasoline and the MTBE draft

fuel effects model were used to developed benzene and MTBE fractions of evaporative TOG.10, 11

A summary of the algorithms used are given in Table 2.6. Since the above two models do not

calculate resting loss emissions, it was assumed that benzene and MTBE fractions for resting loss

were equal to those of diurnal emissions. The algorithms for benzene are based on a proprietary

vapor equilibrium model developed by General Motors. For MTBE, diurnal and hot soak

emission algorithms are based on regression analysis of data from over 100 tests; and the running

loss algorithm is based on data from 6 tests. The refueling emissions algorithm is based on an

analysis done at the Colorado School of Mines, which relates MTBE refueling emissions to

benzene refueling emissions.16 MOBILE6.2 does not estimate crankcase emissions of HAPs due

to a lack of HAP emissions data on this emissions type.

Table 2.6. Evaporative Benzene and MTBE Fraction Equations

from the Complex Model and EPA’s MTBE Model

Pollutant Process Toxic Fraction Equation (Toxic/TOG)

Benzene

Hot Soak

Diurnal

Running

Resting

Refueling

(-0.03420*OXY - 0.080274*RVP + 1.4448)*BNZ/100

(-0.02895*OXY - 0.080274*RVP + 1.3758)*BNZ/100

(-0.03420*OXY - 0.080274*RVP + 1.4448)*BNZ/100

(-0.02895*OXY - 0.080274*RVP + 1.3758)*BNZ/100

(-0.02955*OXY - 0.081507*RVP + 1.3972)*BNZ/100

MTBE

(High)

Hot Soak

Diurnal

Running

Resting

Refueling

(24.205 - 1.746*RVP)*MTBE/1000

(22.198 - 1.746*RVP)*MTBE/1000

(17.8538 - 1.6622*RVP)*MTBE/1000

(22.198 - 1.746*RVP)*MTBE/1000

1.743*MTBE*(-0.02955*OXY - 0.081507*RVP + 1.3972)/100

Note: OXY = wt% oxygen

RVP = Reid vapor pressure in psi

BNZ = vol% benzene

MTBE = vol% MTBE

2.4. User-Defined Air Toxic Pollutants

MOBILE6.2 has a command (ADDITIONAL HAPS) which allows the user to enter

emission factors or air toxic ratios for additional air toxic pollutants. Table 2.7 lists compounds

identified as mobile source air toxics in the 2000 Mobile Source Air Toxics Rule that are not

explicitly modeled by MOBILE6.2 (benzene, ,13-butadiene, formaldehyde, acetaldehyde, MTBE

and acrolein are modeled) or MOBILE6.1 (diesel particulate matter). 

 
13

Table 2.7. List of Mobile Source Air Toxics (MSATs) Not Explicitly Modeled by MOBILE6.1

or MOBILE6.2.

Arsenic Compounds Mercury Compounds

Chromium Compounds Naphthalenea

Dioxin/Furans Nickel Compounds

Ethylbenzenea POMb

n–Hexanea Styrene

Lead Compounds Toluenea

Manganese Compounds Xylenea

a

Found in evaporative as well as exhaust emissions.

b

Polycyclic Organic Matter includes organic compounds with more than one benzene ring, and which have a

boiling point greater than or equal to 100 degrees centigrade. A group of seven polynuclear aromatic

hydrocarbons, which have been identified by EPA as probable human carcinogens, (benz(a)anthracene,

benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, chrysene, dibenz(a,h)anthracene, and

indeno(1,2,3-cd)pyrene) are sometimes used as surrogates for the larger group of POM compounds.

A number of these compounds have an evaporative as well as an exhaust emissions

component. As described in the MOBILE6.2 User’s Guide, emission factors must be input in

milligrams per mile and ratios can be input as fractions of VOC, fractions of TOG, or fractions of

PM. All user-defined inputs for evaporative emissions must be input as ratios. These ratios must

be expressed as milligrams of HAP per gram of VOC, TOG, or PM.

ADDITIONAL HAPS input files were developed for the compounds listed in Table 2.7,

except for dioxins/furans and lead compounds, and used to develop the draft 1999 National

Emissions Inventory (NEI), version 3 (ftp://ftp.epa.gov/EmisInventory/draftnei99ver3/). 17

Sixteen individual POM compounds were included in the files. Because toxic to TOG ratios for

several gaseous HAPs vary between baseline gasoline and gasoline oxygenated with MTBE or

ethanol, separate input files were developed for: 1) baseline gasoline; 2) gasoline oxygenated

with 2% MTBE by weight (e.g., Federal reformulated gasoline); 3) gasoline oxygenated with

2.7% MTBE by weight (e.g., winter oxygenated gasoline); and 4) gasoline oxygenated with 3.5%

ethanol by weight (gasohol). These input files are provided as examples for users in the updated

MOBILE6.2 release.

3.0 Input Parameter Data

MOBILE6.2 requires the following additional fuel parameter inputs which are not

required for estimation of criteria pollutant emissions:
14

GAS AROMATIC% – Aromatic content of gasoline on a percentage of total volume basis

GAS OLEFIN% – Olefin content of gasoline on a percentage of total volume basis

GAS BENZENE% – Benzene content of gasoline on a percentage of total volume basis

E200 – Percentage of vapor a given gasoline produces at 200 degrees F

E300 – Percentage of vapor a given gasoline produces at 300 degrees F

OXYGENATE – Oxygenate type and content of gasoline on a percentage of total volume basis. 

There are four valid oxygenate types in the model:

MTBE – methyl tertiary butyl ether

ETBE – ethyl tertiary butyl ether

ETOH – ethanol

TAME – tertiary amine methyl ether

These are all parameters included in the Complex Model. MOBILE6.2 cannot model air

toxics in a situation where a single fuel contains more than one oxygenate. However, the user

can model multiple fuels for an area which differ in the oxygenate used, using a “market share”

parameter. This is described in more detail in the User’s Guide. Also, if the user selects ETBE

or TAME, MOBILE6 assumes that it is an equal weight percent of MTBE for the purposes of

HC, CO, and NOx calculations.

3.1 Sources of Fuel Parameter Data for Modeling Base Years

There are a number of sources of data on fuel properties from surveys of gasoline at

service stations. Information on these data sources is provided below.

3.1.1. The Alliance of Automobile Manufacturers North American Gasoline and Diesel Fuel

Survey

The Alliance of Automobile Manufacturers samples commercially available gasoline and

diesel fuel throughout the United States, Mexico, and Canada during the summer and winter

seasons.18 In the U.S., three grades of gasoline are sampled – premium unleaded, mid-grade

unleaded, and regular unleaded. Table 3.1 lists the U. S. cities included in the Alliance gasoline

surveys. These surveys are available for purchase on the Alliance of Automobile Manufacturers’

website:

http://store.autoalliance.org/StoreFront.asp
15

Table 3.1. Cities Included in Fuel Surveys Conducted by the Alliance of Automobile

Manufacturers

Albuquerque, NM Fairbanks, AK** Philadelphia, PA

Atlanta, GA Houston, TX* Phoenix, AZ

Billings, MT Kansas City, MO Pittsburgh, PA*

Boston, MA Las Vegas, NV St. Louis, MO

Chicago, IL Los Angeles, CA San Antonio, TX

Cleveland, OH Miami, FL San Francisco, CA

Dallas, TX Minneapolis/ St. Paul, MN Seattle, WA

Denver, CO New Orleans, LA Washington, DC

Detroit, MI New York City, NY

*Data collection initiated in 1994.

**Data collection initiated in 2000.

3.1.2. TRW Petroleum Technologies Survey

TRW Petroleum Technologies (formerly the National Institute for Petroleum and Energy

Research) also samples gasoline from service stations throughout the country during summer and

winter. The TRW Petroleum Technologies surveys include non-reformulated gasoline, gasolinealcohol blends, and reformulated gasolines. Data are reported for 3 grades, for 15 marketing

districts, selected by elevation and location. Table 3.2 lists the marketing districts included in the

surveys. Information on obtaining surveys can be obtained from the following address:

TRW Petroleum Technologies

Attn: Cheryl L. Dickson

P. O. Box 2543

Batlesville, OK 74005

Telephone: (918)338-4419

3.1.3. Reformulated Gasoline Surveys

The U.S. EPA samples gasoline at the pump in reformulated gasoline areas, at least four

times a year, twice during the summer VOC season (6/1-9/15) and twice outside the VOC

season.19 These surveys collect and analyze samples from retail gasoline stations. Mandatory

reformulated gasoline areas outside California are surveyed at least eleven times a year. Some of

the smallest opt-in areas are not surveyed every year. Surveys measure Complex Model

parameters plus T50 and T90, except that surveys in the federal RFG areas in California are for 
16

Table 3.2. Districts Included in TRW Petroleum Technologies Gasoline Surveys

District States

1 (Northeast) Connecticut, Massachusetts, New Jersey, New York,

Pennsylvania, Rhode Island

2 (Mid-Atlantic Coast) Washington, DC, Maryland, Virginia

3 (Southeast) Alabama, Arkansas, Georgia, Louisiana, North Carolina,

South Carolina, Tennessee

4 (Florida)

5 (North Central) Northern Illinois, Michigan, Minnesota, Wisconsin

6 (Ohio Valley) Indiana, Kentucky, West Virginia, Ohio 

7 (Central and Upper Plains) North Dakota, South Dakota, Nebraska, Kansas, Iowa,

Missouri, Southern Illinois

8 (Oklahoma and East Texas)

9 (North Mountain States) Montana, Wyoming, Eastern Washington, Eastern Oregon

10 (Central Mountain States) Colorado, Utah

11 (New Mexico, West Texas)

12 (West Southwest) Arizona, Southern Nevada, Southeastern CA

13 (Pacific Northwest) Western Washington, Western Oregon

14 (North California and North

Nevada)

15 (South California)

oxygenates only. Prior to 1998, the surveys reported only total oxygen and oxygenate content,

benzene content, aromatics content and Reid vapor pressure (RVP). These data are available at

the following website:

http://www.epa.gov/otaq/regs/fuels/rfg/properf/perfmeth.htm

3.2 Weighting Fuel Parameter Data from Surveys

For most modeling, it will be necessary to develop composite fuel parameters based on

the mix of regular, mid-grade, and premium gasoline. Such data can be found at the State level
17

in the Petroleum Marketing Annual reports, published by the Energy Information Administration, 

Office of Oil and Gas, Department of Energy.20 These documents can be found at the following

website:

http://www.eia.doe.gov/oil_gas/petroleum/data_publications/petroleum_marketing_annual/pma_

historical.html

Also, many areas of the Midwest sell both baseline gasoline and gasohol. Information on

baseline and gasohol sales volumes at the State level is compiled by the U.S. Department of

Transportation, Federal Highway Administration, Office of Highway Policy Information.21 The

website where this information can be obtained is:

http://www.fhwa.dot.gov/ohim/qffuel.htm

3.3. Projecting Fuel Parameters to Future Years

In order to do toxic emission factor modeling for future years, model users will need to

make a determination of appropriate fuel parameters to use in the modeling. There are three

potential approaches which may be used to do this:

1) Use existing refinery modeling work and apply results to areas being modeled.

2) Employ a consultant to evaluate what fuel changes are likely, based on professional

judgement and experience, or to do new refinery modeling work.

3) If one is modeling an area where a new program has been implemented, look at other

areas of the country where the program has been implemented, and make inferences.

Several refinery modeling studies were done in conjunction with the Tier 2/ Gasoline

Sulfur Final Rulemaking, to evaluate costs of meeting low sulfur standards. These studies were

done by the American Petroleum Institute, the National Petrochemical and Refiners Association,

the Association of International Automobile Manufacturers, and the Department of Energy. 

Results of these studies are summarized Chapter 5 of the Regulatory Impact Analysis for the

rule.5

3.4. Fuel Parameter Data from Recent EPA Toxic Emissions Modeling

In its 1999 assessment of motor vehicle toxic emissions and exposure,3 EPA compiled

fuel summer and winter parameters for 10 urban areas and 15 regions, which were used to

develop emission factors for construction of a nationwide highway mobile source toxics

inventory. Data were compiled for 1990 and 1996 base years, summer and winter. Projections

to 2007 and 2020 were done based on refinery modeling. Methods use to do projections are 
18

described in Appendix J of the 1999 assessment. The parameters used in this modeling are

provided in the Appendix of this guidance document. 

In addition, EPA recently developed county-level fuel parameters for 1990, 1996, and

1999, to use in developing revised inventory estimates for the NEI. These fuel parameters can be

found at the EPA ftp site with draft 1999 NEI, version 3 data:

ftp://ftp.epa.gov/EmisInventory/draftnei99ver3/

4.0 Results of the MOBILE6.2 Model

4.1 Comparison of Calendar Year Fleet Average Emission Factors to MOBTOX5b

Emission Factors from 1999 Study

This section presents some limited results of emission factor modeling using

MOBILE6.2, comparing estimates to those from MOBTOX5b, the predecessor to this model. 

The MOBTOX5b emission factors were obtained from analyses done for the 1999 document,

“Analysis of the Impacts of Control Programs on Motor Vehicle Toxics Emissions and Exposure

in Urban Areas and Nationwide.”3 These emission factors do not include impacts of 2007 heavy

duty standards. The MOBILE6.2 toxic emission factors were developed using the same input

data, again not including impacts of 2007 heavy duty standards. The limited results presented

here are based on modeling for the city of Atlanta. Atlanta does not have a reformulated gasoline

program but does have an inspection and maintenance program. Although absolute emission

levels vary significantly from city to city, depending on type of fuel program, type of inspection

and maintenance program, average temperature and other local parameters, the trends in toxic

emissions are consistent. Thus modeling results for Atlanta are a good illustration of the

directional differences which can be anticipated in changing between the models, provided input

parameters are similar.

Figures 4.1 through 4.4 present fleet average toxic emission factors from MOBTOX5b

and MOBILE6.2, for benzene, 1,3-butadiene, formaldehyde, and acetaldehyde. For all

compounds, MOBILE6.2 estimates higher emission factors in base years, with a convergence in

emission factors by 2020. This trend is primarily a result of changes in the TOG emission rates

used in MOBILE6.2, versus those used in MOBTOX5b. The TOG emission rates in

MOBTOX5b were derived incorporating elements of the MOBILE6 methodology, but significant

revisions to the emission rates were made subsequent to the development of MOBTOX5b and

prior to release of MOBILE6. The difference in underlying TOG emission rates between the two

models are given in Figure 4.5.
19

Figure 4.1. MOBILE6.2 and MOBTOX5b Comparison for 

Benzene (fleet average, exhaust and evaporative)

0

20

40

60

80

100

120

140

1985 1990 1995 2000 2005 2010 2015 2020 2025

Calendar Year

Benzene (mg/mi)

MOBTOX

MOBILE6.2

Figure 4.2. M OBILE6.2 and M OBTOX5b Comparison for 1,3-

Butadiene (fleet average)

0.0

5.0

10.0

15.0

20.0

25.0

1985 1990 1995 2000 2005 2010 2015 2020 2025

Calendar Year

1,3 Butadiene (mg/mi)

MOBTOX

MOBILE6.2
20

Figure 4.3. M OBILE6.2 and M OBTOX5b Comparison for 

Formaldehyde (fleet average)

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

1985 1990 1995 2000 2005 2010 2015 2020 2025

Calendar Year

Formaldehyde (mg/mi)

MOBTOX

MOBILE6.2

Figure 4.4. MOBILE6.2 and MOBTOX5b Comparison for Acetaldehyde 

(fleet average)

0.0

5.0

10.0

15.0

20.0

25.0

1985 1990 1995 2000 2005 2010 2015 2020 2025

Calendar Year

Acetaldehyde (mg/mi)

MOB T OX

MOB ILE6.2
21

Figure 4.5. MOBILE6.2 and MOBTOX5b Comparison for TOG 

Emissions (Exhaust and Evaporative)

0

1000

2000

3000

4000

5000

6000

1985 1990 1995 2000 2005 2010 2015 2020 2025

Calendar Year

Exhaust + Evaporative TOG (mg/mi)

MOBTOX

MOBILE6.2

In base years (around CY 1990), the difference between MOBILE6.2 and MOBTOX5b is

greatest for 1,3-butadiene. This is because during base years, MOBILE6.2 classifies more

vehicles as hydrocarbon high emitters, and the toxic to TOG fraction for 1,3-butadiene is roughly

three times higher than the normal emitter fraction. It should also be noted that MOBILE6.2

projects slightly lower emission factors for formaldehyde and acetaldehyde by 2020. This is

because diesel vehicles emit proportionally larger quantities of carbonyl compounds relative to

TOG, and MOBILE6 projects lower TOG emissions for heavy duty diesel engines, particularly in

future years when benefits of 2007 heavy duty standards are realized.

4.2 Comparison of MOBILE6.2 and MOBTOX5b Results by Vehicle Class and Model

Year

As part of an evaluation of MOBILE6.2 modeling results, Eastern Research Group, Inc.

developed an Excel Workbook which can generate charts which can make MOBILE6.2 versus

MOBTOX5b comparisons for the following cases:

4) Atlanta, Chicago, and Los Angeles

5) 1990, 2007, and 2020

6) Winter and Summer

The workbook allows comparison of exhaust and evaporative toxic and TOG emission factors, as

well as toxic to TOG ratios, for individual vehicles classes. Results are presented by model year
22

for a given calendar year. Since MOBILE6.2 and MOBTOX5b use different classes of vehicles,

the comparisons in Table 4.1 were used.

Table 4.1. Classes of Vehicle Types Compared Between MOBILE6.2 and MOBTOX5b

MOBILE5/ MOBTOX

Vehicle Type

MOBTOX

Vehicle Type

ID Number

MOBILE6

Vehicle Type

MOBILE6 Vehicle

Type ID Number

LDGV 1 LDGV 1

LDGT2 3 LDGT3 4

HDGV 4 HDGV2b 6

LDDV 5 LDDV 14

HDDV 7 HDDV8B 23

Figures 4.6 and 4.7 depict mg/mi emission factors and toxic to TOG ratios, respectively,

for light-duty gasoline vehicle exhaust benzene in Atlanta, summer, 2007, by model year. 

MOBILE6.2 emission factors for early 1980's model years are about three times greater than

MOBTOX5b, while there is convergence for later model years. Benzene to TOG ratios are also

somewhat higher for earlier model years, but the difference is not as great as the difference in

emission factors. Thus, it can be concluded that differences in TOG emission rates for earlier

model years account for most of the difference in benzene emission rates (Figure 4.8).

Figure 4.6. Light Duty Gasoline Vehicle mg/mi Benzene Exhaust Emission Factors for Atlanta,

Summer, 2007.
23

Figure 4.7. Light Duty Gasoline Vehicle Benzene Exhaust fractions of TOG for Atlanta,

Summer, 2007.

Figure 4.8. Light Duty Gasoline Vehicle Exhaust g/mi TOG for Atlanta, Summer, 2007.
24

A similar trend is seen in benzene evaporative emission rates (Figure 4.9). For heavy

duty diesel vehicles, however, benzene exhaust emission rates estimated using MOBILE6.2 are

lower than MOBTOX5b (Figure 4.10). This is a result of lower TOG emission rates in

MOBILE6.2 for that vehicle class.

The Excel workbook used to make these comparisons for benzene, as well as

comparisons for other HAPs, has been made available along with the release of the document

(file name External_ChartComparisons_20011120.xls). 

Figure 4.9. Light Duty Gasoline Vehicle Evaporative Benzene mg/mi for Atlanta, Summer,

2007.
25

Figure 4.10. Heavy Duty Diesel Vehicle Exhaust Benzene mg/mi for Atlanta, Summer, 2007.
26

1. EPA. 1993. Motor Vehicle-Related Air Toxics Study. Office of Mobile Sources, Ann Arbor,

MI. Report No. EPA 420-R-93-005, April. http://www.epa.gov/otaq/toxics.htm

2. Cook, R., P. Brodowicz, D. Brzezinski, P. Heirigs, and S. Kishan. 1998. Analysis of In-Use

Motor Vehicle Toxic Emissions Using a New Emission Factor Model, MOBTOX5b. Presented

at AWMA Specialty Conference, Emission Inventory: Living in a Global Environment,

December 8-10, 1998.

3. EPA. 1999. Analysis of the Impacts of Control Programs on Motor Vehicle Toxics Emissions

and Exposure in Urban Areas and Nationwide. Prepared for U. S. EPA, Office of Transportation

and Air Quality, by Sierra Research, Inc., and Radian International Corporation/Eastern Research

Group. Report No. EPA 420 –R-99-029/030. http://www.epa.gov/otaq/regs/toxics/r99029.pdf

4. Cook, R., P. Brodowicz, P. Heirigs, S. Kishan, and M. Weatherby. 2000. Assessment of

Emissions and Exposure from Selected Motor Vehicle Air Toxics. Paper No. 77, Presented at

93rd Annual AWMA Conference, Salt Lake City, UT, June 18-22, 2000.

5. EPA. 1999. Regulatory Impact Analysis - Control of Air Pollution from New Motor

Vehicles: Tier 2 Motor Vehicle Emissions Standards and Gasoline Sulfur Control. Report No.

EPA420-R-99-023, December 1999. 

http://www.epa.gov/otaq/regs/ld-hwy/tier-2/frm/ria/r99023.pdf

6. EPA. 2000. Regulatory Impact Analysis: Heavy-Duty Engine and Vehicle Standards and

Highway Diesel Fuel Sulfur Control Requirements. Report No. EPA420-R-00-026, December

2000. http://www.epa.gov/otaq/diesel.htm

7. EPA. 2000. Technical Support Document. Control of Hazardous Air Pollutants from Motor

Vehicles and Motor Vehicle Fuels. EPA Office of Transportation and Air Quality, December

2000. Report No. EPA-420-R-00-023. http://www.epa.gov/otaq/regs/toxics/r00023.pdf

8. EPA. 2002. National-Scale Air Toxics Assessment for 1996.

http://www.epa.gov/ttn/atw/nata/

9. Eastern Research Group. 2000a. Documentation for the 1996 Base Year National Toxics

Inventory for Onroad Sources. Prepared for U. S. EPA, Emission Factor and Inventory Group,

Office of Air Quality Planning and Standards, June 2, 2000. http://www.epa.gov/ttn/chief/nti/

10. EPA. 1993. Final Regulatory Impact Analysis for Reformulated Gasoline. December 13,

1993. http://www.epa.gov/otaq/regs/fuels/rfg/ (ria.zip)

5.0 References
27

11. Wyborny, L. 1998. Methyl Tertiary Butyl Ether (MTBE) Emissions from Passenger Cars. 

Draft Technical Report. U. S. Environmental Protection Agency, Office of Mobile Sources. 

April, 1998.

12. National Research Council. 2000. Modeling Mobile Source Emissions. National Academy

Press, Washington, DC. http://www.nap.edu/books/0309070880/html/

13. Coordinating Research Council. 1997. Test Program to Determine Fuel Sulfur Effect on

Emissions from California Low-Emission Vehicles. Project E-42.

14. EPA. 1998. Emission Control Technology Distributions: Current and Projected Use of

Emission Control Technology in Light and Heavy Duty Engines. EPA Report No. 420-98-013,

MOBILE6 Document No. M6.FLT.008. http://www.epa.gov/otaq/models/mobile6/m6flt008.pdf

15. EPA. 2001. Stategies and Issues in Correlating Diesel Fuel Properties with Emissions: Staff

Discussion Document. EPA Report No. 420-P-01-001. 

http://www.epa.gov/otaq/models/analysis/p01001.pdf

16. Grabowski, Michael S., Mowery, Deborah L., McClelland, John W.; Draft Report: 

Microenvironment and Source Apportionment Analysis of Toxics Exposure from Conventional

and Oxygenated Motor Fuels;” Colorado School of Mines, September 1997.

17. EPA. 2002. Draft 1999 National Emissions Inventory (NEI), Version 3.

(ftp://ftp.epa.gov/EmisInventory/draftnei99ver3/).

18. Alliance of Automobile Manufacturers. North American Fuel Surveys. 

http://store.autoalliance.org/StoreFront.asp

19. EPA. Information on Reformulated Gasoline (RFG) Properties and Emissions Performance

by Area and Season. http://www.epa.gov/otaq/regs/fuels/rfg/properf/perfmeth.htm

20. Energy Information Administration. Petroleum Marketing Annual Reports. 

http://www.eia.doe.gov/oil_gas/petroleum/data_publications/petroleum_marketing_annual/pma_

historical.html

21. Federal Highway Administration. Highway Statistics: Motor Fuel. 

http://www.fhwa.dot.gov/ohim/qffuel.htm
 Appendix -- 1990 Baseline Fuel Specifications

Area Abbrev. Year Season RVP, psi Aromatics Olefins Benzene % Sulfur E200 % E300 % MTBE % ETBE % Atlanta AT 1990 Summer 8.5 27.9 10.5 1.16 344 40.7 79.0 0.0 0.0 Atlanta AT 1990 Winter 12.5 26.2 14.4 1.49 267 49.1 82.4 0.0 0.0 Chicago CH 1990 Summer 8.7 28.8 8.6 1.35 512 47.2 78.6 0.0 0.0 Chicago CH 1990 Winter 13.7 23.0 9.1 1.69 450 54.4 82.6 0.0 0.0 Denver DN 1990 Summer 8.3 24.8 12.2 1.41 375 45.1 79.4 0.0 0.0 Denver DN 1990 Winter 12.1 19.3 12.8 1.23 272 62.0 85.5 11.6 0.0 Houston HS 1990 Summer 8.3 30.2 10.9 1.36 375 46.7 79.4 0.5 0.0 Houston HS 1990 Winter 12.8 23.0 14.4 1.22 454 52.4 80.2 0.0 0.0 Minneapolis MN 1990 Summer 9.5 29.8 8.3 1.69 422 45.9 78.9 0.0 0.0 Minneapolis MN 1990 Winter 13.2 24.9 9.3 1.86 701 56.0 81.6 0.0 0.0 New York NY 1990 Summer 8.3 31.9 13.9 1.08 367 43.1 78.8 2.4 0.0 New York NY 1990 Winter 13.3 26.4 16.7 1.55 274 49.5 81.8 0.0 0.0 Philadelphia PA 1990 Summer 8.4 29.2 13.7 0.86 371 43.6 79.0 0.0 0.0 Philadelphia PA 1990 Winter 13.9 23.5 13.2 1.63 206 50.5 82.9 0.0 0.0 Phoenix PX 1990 Summer 8.1 33.0 5.9 2.15 123 41.1 78.5 0.0 0.0 Phoenix PX 1990 Winter 10.9 26.4 5.6 1.88 157 56.5 82.9 11.4 0.0 Spokane SP 1990 Summer 8.6 21.0 8.0 1.36 739 46.6 82.6 0.0 0.0 Spokane SP 1990 Winter 13.1 19.2 10.3 1.58 698 51.1 84.9 0.0 0.0 St. Louis SL 1990 Summer 8.8 28.9 8.9 1.11 372 45.2 78.9 0.0 0.0 St. Louis SL 1990 Winter 13.2 22.0 11.4 1.71 319 54.0 82.7 0.0 0.0 Western WA/OR - Win 95/96 WA 1990 Summer 9.4 29.0 10.0 2.34 449 43.5 81.0 1.8 0.0 Western WA/OR - Win 95/96 WA 1990 Winter 12.9 30.9 8.2 2.47 314 49.7 83.7 0.5 0.0 Western WA/OR - Win 96/97 WB 1990 Summer 9.4 29.0 10.0 2.34 449 43.5 81.0 1.8 0.0 Western WA/OR - Win 96/97 WB 1990 Winter 12.9 30.9 8.2 2.47 314 49.7 83.7 0.5 0.0 Northern California CN 1990 Summer 8.3 29.9 11.5 2.17 104 41.8 82.2 0.0 0.0 Northern California CN 1990 Winter 12.4 29.9 9.6 2.14 135 49.3 84.3 0.5 0.0 Southern California CS 1990 Summer 8.2 29.1 7.6 2.12 172 40.8 80.8 2.8 0.0 Southern California CS 1990 Winter 11.3 29.8 8.6 1.81 205 45.9 82.6 0.5 0.0 ID/MT/WY ID 1990 Summer 9.3 24.6 9.9 1.98 565 47.5 84.1 0.2 0.0 ID/MT/WY ID 1990 Winter 13.0 22.5 13.7 1.71 681 53.6 86.5 0.5 0.0 UT/NM/NV UT 1990 Summer 8.7 23.7 11.0 1.97 235 44.6 82.8 1.3 0.0 UT/NM/NV UT 1990 Winter 13.0 23.5 13.5 2.13 159 56.3 87.4 0.0 0.0 ND/SD/NE/IA/KS/Western MO ND 1990 Summer 8.8 26.6 9.6 1.50 328 47.4 81.3 0.7 0.0 ND/SD/NE/IA/KS/Western MO ND 1990 Winter 13.3 21.0 10.8 1.29 307 55.3 84.6 0.8 0.0 AR/MS/AL/SC/Northern LA SE 1990 Summer 8.6 28.8 12.8 1.62 363 43.0 79.5 1.5 0.0 AR/MS/AL/SC/Northern LA SE 1990 Winter 12.3 25.6 16.9 1.47 328 50.0 81.6 1.2 0.0 Florida FL 1990 Summer 9.2 31.6 9.0 1.40 363 44.1 79.2 1.5 0.0 Florida FL 1990 Winter 12.2 26.0 17.7 1.25 372 48.9 80.3 1.2 0.0 Northeast-NoRFG NN 1990 Summer 8.8 29.7 13.7 1.77 332 42.5 80.4 1.1 0.0 Northeast-NoRFG NN 1990 Winter 13.5 26.5 17.3 1.42 343 51.6 82.9 1.2 0.0 Northeast-RFG NR 1990 Summer 8.8 29.7 13.7 1.77 332 42.5 80.4 1.1 0.0 Northeast-RFG NR 1990 Winter 13.5 26.5 17.3 1.42 343 51.6 82.9 1.2 0.0 Ohio Valley-NoRFG ON 1990 Summer 9.7 26.8 10.5 1.59 383 46.8 80.3 1.3 0.0 Ohio Valley-NoRFG ON 1990 Winter 14.1 24.9 11.1 1.56 333 55.6 82.6 0.9 0.0 Ohio Valley-RFG OR 1990 Summer 9.7 26.8 10.5 1.59 383 46.8 80.3 1.3 0.0 Ohio Valley-RFG OR 1990 Winter 14.1 24.9 11.1 1.56 333 55.6 82.6 0.9 0.0 Northern MI/WI MI 1990 Summer 9.4 27.1 8.5 1.57 363 49.2 80.8 2.5 0.0 Northern MI/WI MI 1990 Winter 14.0 24.5 9.6 1.36 352 55.8 83.4 5.4 0.0 West Texas WT 1990 Summer 8.0 28.6 9.6 1.83 289 45.3 81.4 2.4 0.0 West Texas WT 1990 Winter 11.7 27.2 14.6 1.75 362 49.2 82.8 5.2 0.0 
 Appendix -- 1996 Baseline Fuel Specifications

Area Abbrev. Year Season RVP, psi Aromatics Olefins Benzene % Sulfur E200 % E300 % MTBE % ETBE Atlanta AT 1996 Summer 7.2 32.1 11.2 0.87 343 36.9 79.8 0.7 Atlanta AT 1996 Winter 12.4 24.8 13.0 0.77 447 51.2 82.7 0.3 Chicago CH 1996 Summer 7.9 26.0 9.7 0.96 492 50.2 80.8 0.0 Chicago CH 1996 Winter 14.0 22.4 7.8 0.80 523 58.0 83.9 0.0 Denver DN 1996 Summer 8.8 27.1 8.8 1.33 296 50.1 83.1 0.0 Denver DN 1996 Winter 13.6 21.9 9.2 0.94 350 62.1 88.1 0.0 Houston HS 1996 Summer 7.1 27.4 13.0 0.71 261 47.8 79.8 9.8 Houston HS 1996 Winter 12.8 21.1 12.8 0.70 224 59.9 83.8 7.9 Minneapolis MN 1996 Summer 9.6 28.2 7.3 1.81 121 59.4 84.6 0.0 Minneapolis MN 1996 Winter 14.9 23.4 5.3 1.65 70 62.3 89.1 0.0 New York NY 1996 Summer 8.0 28.6 17.1 0.51 231 49.8 81.5 10.6 New York NY 1996 Winter 13.2 23.3 16.6 0.47 267 57.5 85.7 14.5 Philadelphia PA 1996 Summer 7.9 29.0 12.3 0.80 367 51.2 81.8 11.3 Philadelphia PA 1996 Winter 13.5 25.4 10.2 0.63 337 59.3 85.9 8.8 Phoenix PX 1996 Summer 6.8 36.1 6.8 1.07 118 45.7 76.2 0.8 Phoenix PX 1996 Winter 8.7 34.3 7.1 1.40 216 50.2 82.6 0.0 Spokane SP 1996 Summer 8.7 28.5 8.3 1.32 412 45.0 81.4 0.0 Spokane SP 1996 Winter 14.8 18.6 6.9 0.97 350 59.8 87.1 0.0 St. Louis SL 1996 Summer 6.8 29.9 12.0 0.70 492 39.0 78.8 0.0 St. Louis SL 1996 Winter 13.6 23.8 11.4 0.89 535 52.7 82.6 0.0 Western WA/OR - Win 95/96 WA 1996 Summer 8.0 35.7 6.7 2.17 256 44.0 82.4 0.1 Western WA/OR - Win 95/96 WA 1996 Winter 13.6 27.5 6.3 1.81 342 58.8 84.5 0.0 Western WA/OR - Win 96/97 WB 1996 Summer 8.0 35.7 6.7 2.17 256 44.0 82.4 0.1 Western WA/OR - Win 96/97 WB 1996 Winter 13.4 29.4 5.8 1.81 345 52.7 84.0 0.0 Northern California CN 1996 Summer 6.9 24.4 3.5 0.56 26 49.3 89.9 9.1 Northern California CN 1996 Winter 10.5 20.1 2.1 0.52 30 54.4 90.8 10.5 Southern California CS 1996 Summer 7.0 20.7 4.3 0.52 10 51.0 86.8 11.0 Southern California CS 1996 Winter 10.6 17.7 3.5 0.57 31 56.3 88.6 11.6 ID/MT/WY ID 1996 Summer 8.5 28.3 8.1 1.64 318 46.8 84.6 0.5 ID/MT/WY ID 1996 Winter 13.5 22.8 6.4 1.40 252 53.7 84.6 0.5 UT/NM/NV UT 1996 Summer 8.0 30.7 10.6 1.75 207 45.2 83.6 1.1 UT/NM/NV UT 1996 Winter 14.4 20.4 8.3 1.14 106 72.2 85.2 0.0 ND/SD/NE/IA/KS/Western MO ND 1996 Summer 8.3 29.0 8.0 1.33 229 45.4 81.8 0.1 ND/SD/NE/IA/KS/Western MO ND 1996 Winter 13.4 22.4 6.8 1.12 224 56.0 85.0 0.4 AR/MS/AL/SC/Northern LA SE 1996 Summer 7.7 30.7 13.2 0.84 349 38.8 78.1 0.5 AR/MS/AL/SC/Northern LA SE 1996 Winter 12.2 24.5 13.0 0.81 271 50.5 82.3 0.4 Florida FL 1996 Summer 7.6 33.6 10.1 0.79 280 40.3 79.4 0.5 Florida FL 1996 Winter 12.1 24.6 12.8 0.82 289 50.5 82.7 0.4 Northeast-NoRFG NN 1996 Summer 8.6 28.1 12.4 1.03 308 43.2 80.7 1.5 Northeast-NoRFG NN 1996 Winter 13.2 23.8 16.2 0.73 222 52.2 83.3 0.8 Northeast-RFG NR 1996 Summer 7.9 24.7 11.7 0.65 234 50.5 82.4 10.9 Northeast-RFG NR 1996 Winter 12.5 19.7 9.6 0.66 265 59.1 87.0 10.5 Ohio Valley-NoRFG ON 1996 Summer 8.7 30.2 10.4 1.24 334 45.3 80.3 0.9 Ohio Valley-NoRFG ON 1996 Winter 14.1 25.5 8.8 1.04 310 54.0 82.6 0.4 Ohio Valley-RFG OR 1996 Summer 7.8 27.3 8.1 0.99 300 45.5 81.1 9.5 Ohio Valley-RFG OR 1996 Winter 12.9 18.9 8.8 0.97 355 59.4 88.4 10.0 Northern MI/WI MI 1996 Summer 8.5 28.4 9.1 1.32 277 49.0 80.9 0.5 Northern MI/WI MI 1996 Winter 14.0 25.3 8.4 1.46 206 57.6 83.1 0.2 West Texas WT 1996 Summer 8.0 30.1 9.7 1.48 263 41.5 81.6 0.2 West Texas WT 1996 Winter 11.8 25.8 8.1 1.21 361 47.3 83.7 0.0 
 Appendix -- 2007/2020 30 ppm Sulfur Fuel Specifications

Area Abbrev. Year Season Scenario RVP, psi Aromatic Olefins Benzene Sulfur E200 % E300 % MTBE % ETBE Atlanta AT 2007 Summer 30 ppm 7.0 30.9 8.9 0.87 30 38.1 80.2 1.7 0Atlanta AT 2007 Winter 30 ppm 12.4 24.0 11.4 0.77 30 50.8 82.7 0.6 0Chicago CH 2007 Summer 30 ppm 6.6 24.1 6.2 0.93 30 51.2 82.7 0.0 13Chicago CH 2007 Winter 30 ppm 14.0 17.6 2.9 0.80 30 60.1 87.3 0.0 0Denver DN 2007 Summer 30 ppm 8.8 26.1 7.0 1.33 30 51.3 83.5 0.0 0Denver DN 2007 Winter 30 ppm 13.6 21.2 8.0 0.94 30 61.7 88.1 0.0 0Houston HS 2007 Summer 30 ppm 6.7 26.8 9.7 0.78 30 48.5 82.5 11.2 0Houston HS 2007 Winter 30 ppm 12.8 19.7 5.0 0.67 30 56.5 86.4 10.6 0Minneapolis MN 2007 Summer 30 ppm 9.6 27.2 5.8 1.81 30 60.6 85.1 0.0 0Minneapolis MN 2007 Winter 30 ppm 14.9 22.7 4.7 1.65 30 61.9 89.1 0.0 0New York NY 2007 Summer 30 ppm 6.8 25.8 11.9 0.59 30 49.9 83.8 11.2 0New York NY 2007 Winter 30 ppm 13.2 19.3 5.8 0.53 30 58.1 88.0 14.6 0Philadelphia PA 2007 Summer 30 ppm 6.7 25.0 10.3 0.65 30 51.1 84.1 11.8 0Philadelphia PA 2007 Winter 30 ppm 13.5 21.0 5.2 0.62 30 56.5 87.6 11.2 0Phoenix PX 2007 Summer 30 ppm 7.0 22.0 4.0 0.80 30 50.0 92.0 0.0 0Phoenix PX 2007 Winter 30 ppm 10.6 17.7 3.5 0.57 30 56.3 88.6 0.0 0Spokane SP 2007 Summer 30 ppm 8.7 27.5 6.6 1.32 30 46.2 81.8 0.0 0Spokane SP 2007 Winter 30 ppm 14.8 17.9 6.0 0.96 30 59.8 87.2 0.0 0St. Louis SL 2007 Summer 30 ppm 6.4 28.8 11.3 0.72 30 45.0 79.6 0.0 13St. Louis SL 2007 Winter 30 ppm 13.6 20.7 4.9 0.89 30 52.5 84.7 0.0 0Western Washington/Oregon WA 2007 Summer 30 ppm 8.0 34.5 5.3 2.17 30 45.2 82.8 0.0 0Western Washington/Oregon WA 2007 Winter 30 ppm 13.5 27.6 5.3 1.81 30 55.4 84.2 0.0 0Western Washington/Oregon WB 2007 Summer 30 ppm 8.0 34.5 5.3 2.17 30 45.2 82.8 0.0 0Western Washington/Oregon WB 2007 Winter 30 ppm 13.5 27.6 5.3 1.81 30 55.4 84.2 0.0 0Northern California CN 2007 Summer 30 ppm 7.0 22.0 4.0 0.80 30 50.0 92.0 0.0 0Northern California CN 2007 Winter 30 ppm 10.5 20.1 2.1 0.52 30 54.4 90.8 0.0 0Southern California CS 2007 Summer 30 ppm 7.0 22.0 4.0 0.80 30 50.0 92.0 0.0 0Southern California CS 2007 Winter 30 ppm 10.6 17.7 3.5 0.57 30 56.3 88.6 0.0 0Idaho/Montana/Wyoming ID 2007 Summer 30 ppm 8.5 27.3 6.5 1.64 30 48.0 85.0 1.1 0Idaho/Montana/Wyoming ID 2007 Winter 30 ppm 13.5 22.1 5.6 1.40 30 53.3 84.6 0.6 0Utah/New Mexico/Nevada UT 2007 Summer 30 ppm 8.0 29.6 8.5 1.75 30 46.4 84.0 2.2 0Utah/New Mexico/Nevada UT 2007 Winter 30 ppm 14.4 19.8 7.2 1.14 30 71.7 85.2 0.0 0ND/SD/NE/IA/KS/Western MO ND 2007 Summer 30 ppm 8.3 28.0 6.4 1.33 30 46.6 82.2 0.0 0ND/SD/NE/IA/KS/Western MO ND 2007 Winter 30 ppm 13.4 21.7 6.0 1.12 30 55.6 85.0 0.6 0AR/MS/AL/SC/Northern LA SE 2007 Summer 30 ppm 7.7 29.6 10.5 0.84 30 40.0 78.5 1.1 0AR/MS/AL/SC/Northern LA SE 2007 Winter 30 ppm 12.2 23.7 11.3 0.81 30 50.1 82.3 0.6 0Florida FL 2007 Summer 30 ppm 7.6 32.4 8.1 0.79 30 41.5 79.8 1.1 0Florida FL 2007 Winter 30 ppm 12.1 23.8 11.2 0.82 30 50.1 82.7 0.6 0Northeastern states - non RFG NN 2007 Summer 30 ppm 8.6 27.1 9.9 1.03 30 44.4 81.1 3.4 0Northeastern states - non RFG NN 2007 Winter 30 ppm 13.2 23.1 14.1 0.73 30 51.8 83.3 0.6 0Northeastern states- with RFG NR 2007 Summer 30 ppm 6.7 24.0 11.0 0.67 30 50.8 83.2 11.2 0Northeastern states- with RFG NR 2007 Winter 30 ppm 12.5 18.2 4.8 0.66 30 59.6 89.7 10.6 0Ohio Valley - non-RFG ON 2007 Summer 30 ppm 8.7 29.1 8.3 1.24 30 46.5 80.7 1.7 0Ohio Valley - non-RFG ON 2007 Winter 30 ppm 14.1 24.7 7.7 1.04 30 53.6 82.6 0.6 0Ohio Valley - with RFG OR 2007 Summer 30 ppm 6.5 27.1 7.6 1.02 30 45.6 81.9 9.5 0Ohio Valley - with RFG OR 2007 Winter 30 ppm 12.9 17.4 4.4 0.97 30 59.9 91.1 10.1 0Northern MI/WI/MN MI 2007 Summer 30 ppm 8.5 27.4 7.3 1.32 30 50.2 81.3 1.1 0Northern MI/WI/MN MI 2007 Winter 30 ppm 14.0 24.5 7.3 1.46 30 57.2 83.1 0.0 0West Texas WT 2007 Summer 30 ppm 8.0 29.1 7.8 1.48 30 42.7 82.0 0.6 0West Texas WT 2007 Winter 30 ppm 11.8 24.9 7.1 1.21 30 46.8 83.7 0.0 0