MOVES2010b: 

Additional Toxics Added to MOVES
Assessment and Standards Division

Office of Transportation and Air Quality

U.S. Environmental Protection Agency

MOVES2010b: 

Additional Toxics Added to MOVES

EPA-420-B-12-029a

May 2012
3 

Table of Contents 

Table of Contents

1. Introduction................................................................................................................. 4

2. Gasoline Vehicles and Trucks ......................................................................................... 7

2.1. Exhaust .................................................................................................................. 7

2.1.1. Gaseous Hydrocarbons ...................................................................................... 7

2.1.2. Polycyclic Aromatic Hydrocarbons .................................................................... 8

2.1.3. Metals............................................................................................................... 9

2.1.4. Dioxins and Furans........................................................................................... 11

2.2. Evaporative and Permeation ............................................................................... 12

3. Diesel Vehicles and Trucks........................................................................................... 14

3.1. Exhaust ................................................................................................................ 14

3.1.1. Gaseous Hydrocarbons .................................................................................... 14

3.1.2. Polycyclic Aromatic Hydrocarbons .................................................................. 16

3.1.3. Metals............................................................................................................. 18

3.1.4. Dioxins........................................................................................................... 18

3.2. Evaporative .......................................................................................................... 19

Appendix A
4 

1. Introduction

The previous version of MOVES, MOVES 2010a, estimated emissions for only a limited 

number of air toxics from highway vehicles, including benzene, 1,3-butadiene, formaldehyde, 

acetaldehyde, acrolein, naphthalene, and ethanol.1 Furthermore, estimation of air toxic 

emissions was done largely by relying on algorithms carried over from MOBILE6.22 and the 

National Mobile Inventory Model (NMIM).3 Exceptions included addition of toxic to 

hydrocarbon ratios for ethanol. 

For benzene, 1,3-butadiene, formaldehyde and acetaldehyde from light duty gasoline 

vehicles and trucks, algorithms calculated toxic to VOC ratios using fuel parameters. These 

algorithms were derived from U. S. EPA’s Complex Model for Reformulated Gasoline, 

developed in the early 1990’s for the Federal Reformulated Gasoline Rule.4 MOVES 2010b 

continues to rely on these algorithms for exhaust and non-permeation evaporative emissions. 

Acrolein, naphthalene and ethanol were estimated using simple toxic to VOC ratios. Ratios for 

ethanol and non-permeation evaporative emissions of naphthalene are the same for gasoline 

vehicles in this version of the model, but ratios for exhaust naphthalene have been updated. 

Acrolein ratios are the same for light-duty gasoline vehicles in both versions of the model; 

however, acrolein ratios for heavy-duty gasoline vehicles differed from light-duty gasoline 

vehicles in MOVES210a, while in MOVES2010b, the ratios for heavy-duty gasoline vehicles are 

the same as light-duty gasoline ratios. Algorithms for diesel vehicles have all been updated. 

None of the other toxics estimated using EPA’s National Mobile Inventory Model 

(NMIM) were included in draft MOVES2010a. However, these HAPs have all been added to 

MOVES2010b. In NMIM, for other light duty gasoline toxics, and for all toxics from other 

vehicle and engine types, the algorithms took one of three forms: toxic to VOC ratios (for 

gaseous HAPs), toxic to PM ratios (PAHs), and basic emission rates (metals).5

 In 

MOVES2010b, the same approach is used, except for PAHs. PAH mass emissions are 

apportioned into the gas and particle phase, and gas phase PAHs are estimated using toxic/VOC 

ratios and particle phase PAHs were estimated using toxic to OC2.5 (organic carbon less than 2.5 

microns) ratios.

The algorithms in NMIM were developed over 10 years ago. More recent data are now 

available, representing more modern vehicles and engines, and fuels more representative of what 

is currently being sold. For many vehicle types, data used to develop algorithms were also very 

limited, and quality of estimates can be enhanced by addition of more data. U. S. EPA has 

analyzed more recent data, reflecting advanced emission control technology and modern fuels, 

and added more data for older technology vehicles to enhance the quality of emission rate 

estimates. 

MOVES2010b includes all air toxic pollutants in the National Emission Inventory (NEI) and 

National Air Toxics Assessment (NATA) that are emitted by mobile sources. This list of 

pollutants is provided in Table 1.1. These pollutants are organized into four categories: 

1) Gaseous hydrocarbons 
5 

2) Polycyclic aromatic hydrocarbons (PAHs) – These hydrocarbons which contain fused 

aromatic rings can be found in the gas phase, particle phase, or both, depending on 

properties of the compound, particle characteristics, and atmospheric condtions 

3) Dioxins and furans – polychlorinated organic compounds which are persistent and 

bioaccumulative 

4) Metals

The pollutant “xylenes” represents the sum of emissions from three isomers of xylene -- oxylene, m-xylene, and p-xylene. MOVES also reports three forms of mercury – elemental 

gaseous, divalent gaseous (a reactive form) and particulate phase. Moreover, arsenic is reported 

as the total mass of all organic and inorganic arsenic compounds. However, emissions data for 

mobile sources all come from measurements of elemental arsenic mass.

Table 1. Air toxics included in MOVES 2011, along with MOVES PollutantID numbers and 

NEI pollutant codes. 

Pollutant

MOVES 

Pollutant ID CAS Number

Gaseous Hydrocarbons

1,3-Butadiene 24 106990

2,2,4-Trimethylpentane 40 540841

Acetaldehyde 26 75070

Acrolein 27 107028

Benzene 20 71432

Ethanol 21 64175

Ethyl Benzene 41 100414

Formaldehyde 25 50000

Hexane 42 110543

Methyl Tert Butyl Ether (MTBE) 22 1634044

Propionaldehyde 43 123386

Styrene 44 100425

Toluene 45 108883

Xylenes 46 1330207

PAHs

Acenaphthene particle 70 83329

Acenaphthylene particle 71 208968

Anthracene particle 72 120127

Benz(a)anthracene particle 73 56553

Benzo(a)pyrene particle 74 50328

Benzo(b)fluoranthene particle 75 205992

Benzo(g,h,i)perylene particle 76 191242

Benzo(k)fluoranthene particle 77 207089

Chrysene particle 78 218019

Dibenzo(a,h)anthracene particle 68 53703

Fluoranthene particle 69 206440
6 

Pollutant

MOVES 

Pollutant ID CAS Number

Fluorene particle 81 86737

Indeno(1,2,3,c,d)pyrene particle 82 193395

Naphthalene particle 23 91203

Phenanthrene particle 83 85018

Pyrene particle 84 129000

Acenaphthene gas 170 83329

Acenaphthylene gas 171 208968

Anthracene gas 172 120127

Benz(a)anthracene gas 173 56553

Benzo(a)pyrene gas 174 50328

Benzo(b)fluoranthene gas 175 205992

Benzo(g,h,i)perylene gas 176 191242

Benzo(k)fluoranthene gas 177 207089

Chrysene gas 178 218019

Dibenzo(a,h)anthracene gas 168 53703

Fluoranthene gas 169 206440

Fluorene gas 181 86737

Indeno(1,2,3,c,d)pyrene gas 182 193395

Naphthalene gas 185 91203

Phenanthrene gas 183 85018

Pyrene gas 184 129000

Dioxins and Furans

2,3,7,8-Tetrachlorodibenzo-p-Dioxin 142 17466016

1,2,3,7,8-Pentachlorodibenzo-pDioxin 135 40321764 

1,2,3,4,7,8-Hexachlorodibenzo-pDioxin 134 39227286

1,2,3,6,7,8-Hexachlorodibenzo-pDioxin 141 57653857

1,2,3,7,8,9-Hexachlorodibenzo-pDioxin 130 19408743 

1,2,3,4,6,7,8-Heptachlorodibenzo-pDioxin 144 35822469

Octachlorodibenzo-p-dioxin 131 3268879

2,3,7,8-Tetrachlorodibenzofuran 136 51207319

1,2,3,4,6,7,8-

Heptachlorodibenzofuran 144 67562394

1,2,3,4,7,8,9-

Heptachlorodibenzofuran 137 55673897 

1,2,3,4,7,8-Hexachlorodibenzofuran 145 70648269

1,2,3,6,7,8-Hexachlorodibenzofuran 144 57117449

1,2,3,7,8,9-Hexachlorodibenzofuran 146 72918219
7 

Pollutant

MOVES 

Pollutant ID CAS Number

1,2,3,7,8-Pentachlorodibenzofuran 135 57117416

2,3,4,6,7,8-Hexachlorodibenzofuran 143 60851345

2,3,4,7,8-Pentachlorodibenzofuran 138 57117314

Octachlorodibenzofuran 133 39001020

Metals

Mercury (elemental gaseous) 60 200

Mercury (divalent gaseous) 61 201

Mercury (particulate) 62 202

Arsenic compounds 63 93

Chromium (Cr3+) 64 16065831

Chromium (Cr6+) 65 18540299

Manganese Compounds 66 7439965

Nickel Compounds 67 7440020

This document provides data methodologies and sources for gasoline vehicles and trucks 

running on E0, E10 and MTBE blends, and diesel vehicles and trucks. Toxics inputs for 

MOVES do not vary by temperature or operating mode. Ambient temperature also affects these 

ratios, but we assumed toxic emission of gaseous toxics and PAHs change proportionally with 

VOC and PM as temperature varies. In general, data are inadequate to account for temperature 

effects on toxic to VOC and toxic to PM ratios. Emission rates for metals are assumed to be 

independent of operating mode and temperature; very little data exist to account for impacts of 

these parameters.

2. Gasoline Vehicles and Trucks

2.1. Exhaust 

2.1.1. Gaseous Hydrocarbons 

MOVES 2010b provides the capability to model toxic emissions from vehicles running 

on gasoline, E10, and MTBE blends. E10 is defined as fuel containing ethanol which is greater 

than or equal to 5% by volume or ETBE greater than or equal to 5% by volume. For additional 

HAPs, the same toxic to VOC ratios are used for MTBE blends and E0. For 2003 and earlier 

vehicles, toxic to VOC ratios for E0 an E10 were developed by Sierra Research6 using estimates 

from EPA’s SPECIATE 4.2 database (Table 2). Ratios for LDG vehicles were used for all 

gasoline vehicle classes. 
8 

Table 2. Toxic to VOC ratios for selected air toxics from Tier 1 and earlier gasoline vehicles and 

trucks. 

pollutant

Name E0 E10

2,2,4-Trimethylpentane 0.01823 0.01849

Ethyl Benzene 0.02147 0.01932

Hexane 0.01570 0.01593

Propionaldehyde 0.00086 0.00086 

Styrene 0.00108 0.00097

Toluene 0.09619 0.08657

Xylene 0.07814 0.07032

For 2004 and later vehicles running on E0 and E10, ratios for additional gaseous HAPs 

for E0 and E10 were obtained from Phase 1 of the EPAct test program. These profiles were 

based on tests from 3 vehicles.7

 Toxic to VOC ratios for E10 are used in MOVES for all 

gasoline above 5% ethanol by volume. Ratios are provided in Table 3. 

Table 3. Toxic to VOC ratios for selected air toxics from Tier 2 gasoline vehicles and trucks

pollutant

Name E0 E10

2,2,4-Trimethylpentane 0.03188 0.01227 

Ethyl Benzene 0.01683 0.01660

Hexane 0.00279 0.02911

Propionaldehyde 0.00122 0.00054

Styrene 0.00085 0.00083

Toluene 0.07542 0.07440

Xylene 0.06127 0.06047 

2.1.2. Polycyclic Aromatic Hydrocarbons

As mentioned previously, in the NMIM model8, PAH emissions were estimated as ratios 

to PM. This approach was used, even though PAHs are found in the gas, semi-volatile and 

particle phase, because there is generally reasonable correlation between PAH and PM 

emissions.9, 10 However, for MOVES 2010b, PAH mass emissions are apportioned into the gas 

and particle phase, and gas phase PAHs are estimated using toxic/VOC ratios and particle phase 

PAHs were estimated using toxic to OC2.5 (organic carbon less than 2.5 microns) ratios. 

Although partitioning of PAHs into the gas and particle phases depends on concentration, 

temperature and other factors, MOVES applies one set of allocation factors under all conditions 

in order to streamline data processing. These allocation factors were developed by Sierra 

Research11 using estimates from EPA’s SPECIATE 4.2 database12 and information on 
9 

compounds’ physical and chemical properties. Table 4 provides molecular weights and 

allocation factors. The allocations from SPECIATE were based on medium duty diesel engine 

data.13 Using PAH and VOC emissions data from Norbeck et al. (1998)14 and the allocation 

factors in Table 4, the toxic/VOC ratios in Table 5 were developed. Norbeck et al. data were 

also used to develop toxic/PM10 ratios. These ratios were then converted to toxic/OC2.5 ratios for 

start and running operation. These conversions were made using assumptions that 90% of PM10

is PM2.5

15, 87.3% of running PM2.5 is OC, and 66.6% of start PM2.5 is OC. OC percentages of 

PM2.5 were obtained from MOVES runs. PAH to VOC and PAH to OC2.5 ratios do not vary 

between E0 and E10 fuels.

2.1.3. Metals

Metals emissions can result from trace level contamination of fuel and engine oil, as well 

attrition from exhaust emission components. MOVES estimates metal emissions using gram per 

mile emission factors. Emission factors for metals remain unchanged from the values used in 

NMIM (Table 6). Emission factors for chromium, magnesium and nickel are obtained 

from a paper by Ball, 1997.16 Eighteen percent of chromium was assumed to be hexavalent, 

based on combustion data from stationary combustion turbines that burn diesel fuel.17 Emission 

factors for mercury were obtained from a 2005 EPA test program. Documentation describing 

development of these emission factors can be found in Appendix A. Emission factors for arsenic 

were developed from data reported for tunnel tests.18 Metal emission rates do not vary among 

fuel types.

Table 4. PAH gas/particle phase allocation factors

PAH Species

Molecular

Weight

Allocation Fraction

PM Phase Gaseous Phase

Acenapthene 154 0 1

Acenaphthylene 152 0 1

Anthracene 178 0.466 0.534

Benz(a)anthracene 228 0.723 0.277

Benzo(a)pyrene 252 1 0

Benzo(b)fluoranthene 252 1 0

Benzo(g,h,i)perylene 276 0.773 0.227

Benzo(k)fluoranthene 252 1 0

Chrysene 228 0.823 0.177

Dibenzo(a,h)anthracene 278 1 0

Fluoranthene 202 0.516 0.484

Fluorene 166 0.215 0.785

Indeno(1,2,3-cd)pyrene 276 1 0

Phenanthrene 178 0.335 0.665

Pyrene 202 0.552 0.448
10 

Table 5. PAH/VOC and PAH/PM ratios for gasoline vehicles and trucks. 

Table 6. Metal emission factors for gasoline vehicles and trucks.

Pollutant Emission Rate (g/mi)

Chromium 6+ 8.9x10-7

Chromium 3+ 4.1x10-6

Manganese 1.7x10-6

Nickel 3.6x10-6

Elemental Gas Phase Hg 1.1x10-7

Reactive Gas Phase Hg 9.9x10-9

Particulate Hg 4.0x10-10

Arsenic 2.3x10-6

PAH

Start 

Fraction of 

OC2.5

Running 

Fraction of 

OC2.5

Fraction of 

VOC

Benzo(a)anthracene 0.0001237 0.0000944 0.0000007

Benzo(a)pyrene 0.0001711 0.0001306 0.0000000

Benzo(b)fluoranthene 0.0002032 0.0001551 0.0000000

Benzo(k)fluoranthene 0.0002032 0.0001551 0.0000000

Chrysene 0.0001408 0.0001075 0.0000005

Dibenz(a,h)anthracene 0.0000000 0.0000000 0.0000000

Indeno(1,2,3-

cd)pyrene 0.0001283 0.0000979 0.0000000

Acenaphthene 0.0000000 0.0000000 0.0000185

Acenaphthalene 0.0000000 0.0000000 0.0001040

Anthracene 0.0006577 0.0005020 0.0000114

Benzo(ghi)perylene 0.0003306 0.0002524 0.0000015

Fluoranthene 0.0007834 0.0005980 0.0000111

Fluorene 0.0005425 0.0004141 0.0000300

Naphthalene 0.0000000 0.0000000 0.0022928

Phenanthrene 0.0014184 0.0010827 0.0000427

Pyrene 0.0011450 0.0008740 0.0000141
11 

2.1.4. Dioxins and Furans 

MOVES estimates emissions for 17 dioxin and furan congeners (Table 7). The emissions 

are estimated using mg/mile emission factors. These emission factors were obtained from EPA’s 

dioxin assessment.19 They do not vary among fuel types. 

Table 7. Dioxin emission factors for gasoline vehicles.

Pollutant Mg/mi

2,3,7,8-TCDD TEQ 8.27E-10

1,2,3,7,8-Pentachlorodibenzo-p-Dioxin 3.70E-10

1,2,3,4,7,8-Hexachlorodibenzo-p-Dioxin 3.87E-10

1,2,3,6,7,8-Hexachlorodibenzo-p-Dioxin 7.92E-10

1,2,3,7,8,9-Hexachlorodibenzo-p-Dioxin 4.93E-10

1,2,3,4,6,7,8-Heptachlorodibenzo-pDioxin 5.95E-09

Octachlorodibenzo-p-dioxin 4.70E-08

2,3,7,8-Tetrachlorodibenzofuran 2.76E-09

1,2,3,7,8-Pentachlorodibenzofuran 1.32E-09

2,3,4,7,8-Pentachlorodibenzofuran 9.68E-10

1,2,3,4,7,8-Hexachlorodibenzofuran 1.09E-09

1,2,3,6,7,8-Hexachlorodibenzofuran 1.16E-09

1,2,3,7,8,9-Hexachlorodibenzofuran 3.17E-10

2,3,4,6,7,8-Hexachlorodibenzofuran 1.36E-09

1,2,3,4,6,7,8-Heptachlorodibenzofuran 1.21E-08

1,2,3,4,7,8,9-Heptachlorodibenzofuran 3.87E-10

Octachlorodibenzofuran 1.37E-08
12 

2.2. Evaporative and Permeation 

Toxic to VOC ratios for evaporative non-permeation emissions of benzene, MTBE, 

ethanol and naphthalene remain unchanged from those in MOVES2010a. In summary, benzene

and MTBE ratios are estimated using algorithms originally developed for MOBILE 6.2. 

However, evaporative emissions processes for MOVES differ from those in MOBILE6.2. Thus, 

algorithms for hot soak in MOBILE6.2 are used for vapor venting and refueling vapor loss in 

MOVES, and algorithms for running loss are used for fuel leaks and refueling spillage loss 

(Table 8). Ratios for naphthalene and ethanol are given in Table 9. 

Ratios for the additional air toxics found in evaporative non-permeation emissions (2,2,4-

trimethylpentane, ethyl benzene, hexane, propionaldehyde, toluene and xylenes) were obtained 

from profiles developed for EPA by Environ Corporation, using data from the Auto/Oil test 

program conducted in the early 1990’s.20 These ratios are also given in Table 9. For all 

pollutants except benzene, ratios are the same for all types of non-permeation evaporative 

emissions. The ratios for 10% ethanol are used for all fuels with greater than or equal to 5% 

ethanol and less than 12%. 

Table 8. Toxic/VOC algorithms for benzene and MTBE gasoline vehicle evaporative emissions. 

Polluta

nt

Process Toxic Fraction Equation (Toxic/VOC)

Benzene

Vapor Venting/Refueling 

Vapor

Fuel Leaks/Spillage

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

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

MTBE

Vapor Venting/Refueling 

Vapor

Fuel Leaks/Spillage

(24.205 - 1.746*RVP)*MTBE/1000

(17.8538 - 1.6622*RVP)*MTBE/1000

 

Note: OXY = wt% oxygen 

RVP = Reid vapor pressure in psi 

BNZ = vol% benzene 

MTBE = vol% MTBE
13 

Table 9. Evaporative Toxic/VOC ratios for other toxics from gasoline vehicles (Auto/Oil). 

Pollutant E0 E10

Ethanol 0.00000 0.11896

Naphthalene 0.00040 0.00040

2,2,4-Trimethylpentane 0.01984 0.03354

Ethyl Benzene 0.02521 0.01721

Hexane 0.02217 0.02536

Toluene 0.09643 0.14336

Xylene 0.07999 0.06423

The composition of permeation emissions differs significantly from other types of 

evaporative emissions. Work to better characterize these permeation emissions was recently 

conducted for the Coordinating Research Council.21,22 These data were used to develop the toxic 

to VOC ratios in Table 10. Data from the CRC E-65 study22

were used for ethanol, while data 

from the CRC E-77-2b study were used for the rest of the air toxics in Table 10.21 For the CRC 

E-77-2b study, data from 3-day diurnal tests on vehicles meeting Tier 1 and near zero 

evaporative emission standards were used. Toxic to VOC ratios for E0 and E10 were estimated 

by averaging data from gasolines of different RVPs. 

Toxic to VOC ratios for benzene, MTBE, and naphthalene are not found in Table 10. For 

benzene, the diurnal emissions algorithm from MOBILE6.2 was used instead, since this 

algorithm accounts for impacts of changing oxygenate, RVP and fuel benzene levels. However, 

the CRC E-65 study suggests that the ratio of benzene from permeation to total VOC is about 

1.77 times higher than the ratio associated with evaporation.23 Thus the diurnal emissions 

algorithm was multiplied by 1.77. This algorithm is:

1.77[(-0.02895*OXY - 0.080274*RVP + 1.3758)*BNZ/100] 

In the absence of data on permeation emissions for MTBE, the resting loss algorithm from 

MOBILE6.2 was used: 

(22.198-1.746RVP)*MTBE/1000 

For naphthalene, the toxic to VOC ratio for non-permeation evaporative emissions was also 

applied to permeation. 
14 

Table 10. Gasoline vehicle permeation toxic/VOC ratios for air toxics except benzene, 

naphthalene and MTBE (CRC E-65 and E-77-2b). 

Pollutant E0 E10

2,2,4-Trimethylpentane 0.036 0.024

Ethyl Benzene 0.003 0.001

Hexane 0.050 0.065

Toluene 0.110 0.101

Xylene 0.016 0.011

Ethanol 0.333

3. Diesel Vehicles and Trucks

Toxic/VOC ratios, PAH/VOC ratios, PAH/PM ratios and metal emission factors were 

developed for exhaust emissions from heavy-duty diesel vehicles and applied to all diesel vehicle 

categories. There are no separate emission ratios or factors for diesel engines running on 

biodiesel fuels or synthetic diesel fuels, due to very limited data. 

3.1. Exhaust 

3.1.1. Gaseous Hydrocarbons 

The composition of VOCs for heavy-duty diesel engines without model year 2007 and 

later emission controls versus those engines with such controls vary significantly. Thus, we 

developed one set of toxic to VOC ratios for pre-2007 diesel engines and another set for 2007 

and later engines. Since extended idle emissions associated with auxiliary power units (APUs) 

are not subject to 2007 standards, toxic to VOC ratios for pre-2007 diesel engines were used for 

them. Since light-duty diesels comprise a very small portion of the fleet, the same ratios were 

applied to all diesel vehicle classes to streamline modeling. 

EPA relied on a database compiled for the Coordinating Research Council (CRC E-75) 

and National Renewable Energy Laboratory (NREL) to develop toxic to VOC ratios for pre2007 engines.24 This database was developed from a literature survey and included data from 13 

different studies. The studies included in this database were conducted in a number of different 

countries, included heavy-duty and light-duty engines, a variety of diesel and biodiesel fuels, and 

a number of different operating modes and cycles. For 2,2,4-trimethylpentane, hexane, 

propionaldehyde, and toluene, toxic to VOC ratios developed by Sierra Research from CRC E75 data were used. The methodology they used to develop ratios is described in detail in their 

technical report. Data from tests using non-conventional diesel fuel (Fischer-Tropsch, bioDiesel, 

ethanol-Diesel blends, emulsified fuel, European blends, and other obvious research fuels) were 

excluded, as were data from non-heavy duty engines. The ratios are provided in Table 11. 

Toxic to VOC ratios for benzene, 1,3-butadiene, formaldehyde, acetaldehyde, acrolein, 

naphthalene, ethylbenzene, styrene and xylenes were developed by EPA from the E-75 database. 
15 

We relied on United States data from heavy-duty diesel engines running on conventional diesel 

fuels, collected on test-cycles representative of real world operation. Some studies measured 

emissions over distance, while other studies measure emissions relative to brake horsepower. 

For studies which measured emissions relative to distance, we calculated mean emissions per 

mile for toxics and VOC, then calculated a ratio of toxics to VOC. For studies which measured 

emissions relative to brake horsepower hour, we calculated mean emissions per brake 

horsepower hour for toxics and VOC, then calculated a second ratio of toxics to VOC. We then 

calculated a composite ratio using sample size to weight the two ratios. The resulting ratios are 

provided in Table 11. 

For 2007 and later heavy-duty diesels, and 2004 and later light-duty diesels which meet Tier 2 

vehicle standards, advanced emission controls change the composition of VOCs. For these 

engines, we relied on speciated emissions data from the Advanced Collaborative Emissions 

Study (ACES), directed by the Health Effects Institute and Coordinating Research Council, with 

participation from a range of government and private sector sponsors.25 Detailed emissions data 

from the study were provided to EPA at the request of the Coordinating Research Council. 

The data were collected on four engines on several test cycles with low sulfur diesel fuel. EPA 

used data from a 16-hour transient cycle. Toxic to VOC ratios obtained from the ACES data are 

provided in Table 12. 

Table 11. Toxic to VOC Ratios for pre-2007 diesel engines (CRC E-75). 

Pollutant Toxic/VOC

1,3-Butadiene 0.002918

2,2,4-Trimethylpentane 0.001808

Acetaldehyde 0.035559

Acrolein 0.006622

Benzene 0.007835

Ethyl Benzene 0.002655

Formaldehyde 0.078225

Hexane 0.00197

Propionaldehyde 0.00468

Styrene 0.001312

Toluene 0.00433

Xylenes 0.003784
16 

Table 12. Toxic to VOC Ratios for 2007 and later diesel engines. 

Pollutant Toxic/VOC

1,3-Butadiene 0.00080

2,2,4-Trimethylpentane 0.00782

Acetaldehyde 0.06934

Acrolein 0.00999

Benzene 0.01291

Ethyl Benzene 0.00627

Formaldehyde 0.21744

Hexane 0.00541

Propionaldehyde 0.00314

Styrene 0.00000

Toluene 0.02999

Xylenes 0.03800

3.1.2. Polycyclic Aromatic Hydrocarbons

As with gasoline vehicles, PAH mass emissions from diesel engines were apportioned 

into the gas and particle phase, using a single set of allocation factors for all conditions. Gas 

phase PAHs were estimated using toxic/VOC ratios and particle phase PAHs were estimated 

using toxic to OC2.5 ratios. Toxic to VOC and toxic to PM2.5 ratios for pre-2007 diesel engines 

were developed by EPA from the E-75 database. Toxic to PM2.5 ratios were converted to toxic 

to OC2.5 ratios using OC2.5 to PM2.5 percentages from MOVES. We relied on United States data 

from heavy-duty diesel engines running on conventional diesel fuels, collected on test-cycles 

representative of real world operation. It should be noted that for some PAHs, there were 

substantially more data than for others; thus the level of confidence in emission factors varies 

among individual compounds. For instance, while data from 66 tests were available for 

acenaphthene, data from only two tests were available for dibenz(a,h)anthracene. Table 13

provides VOC and PM ratios for PAHs from these older technology engines. 

 For 2007 and later diesels, advanced emission controls change the composition and 

reduce the total mass of PAHs. For these engines, we relied on speciated emissions data from 

the ACES study. Table 14 provides VOC and OC2.5 ratios for PAHs from these newer 

technology engines.
17 

Table 13. PAH/VOC and PAH/ OC2.5 ratios for pre-2007 diesel engines. 

PAH

Start 

Fraction of 

OC2.5

Running 

Fraction of 

OC2.5

Fraction of 

HC

Benzo(a)anthracene 0.0002100 0.0005806 0.0000445

Benzo(a)pyrene 0.0000789 0.0002180 0.0000000

Benzo(b)fluoranthene 0.0000234 0.0000648 0.0000000

Benzo(k)fluoranthene 0.0000033 0.0000091 0.0000000

Chrysene 0.0001327 0.0003667 0.0000235

Dibenz(a,h)anthracene 0.0000032 0.0000087 0.0000000

Indeno(1,2,3-

cd)pyrene

0.0000060 0.0000166

0.0000000

Acenaphthene 0.0000000 0.0000000 0.0003210

Acenaphthalene 0.0000000 0.0000000 0.0005009

Anthracene 0.0001058 0.0002924 0.0002353

Benzo(ghi)perylene 0.0000038 0.0000104 0.0000276

Fluoranthene 0.0004058 0.0011217 0.0006108

Fluorene 0.0001818 0.0005025 0.0005914

Naphthalene 0.0000000 0.0000000 0.0090464

Phenanthrene 0.0004187 0.0011574 0.0019446

Pyrene 0.0005865 0.0016213 0.0007577

Table 14. PAH/VOC and PAH/PM ratios for 2007 and later diesel engines.

PAH

Start 

Fraction of 

OC2.5

Running 

Fraction of 

OC2.5

Fraction of 

HC

Benzo(a)anthracene 0.0000015 0.0000010 0.0000003

Benzo(a)pyrene 0.0000061 0.0000042 0.0000000

Benzo(b)fluoranthene 0.0000026 0.0000018 0.0000000

Benzo(k)fluoranthene 0.0000026 0.0000018 0.0000000

Chrysene 0.0000046 0.0000031 0.0000005

Dibenz(a,h)anthracene 0.0000018 0.0000013 0.0000000

Indeno(1,2,3-cd)pyrene 0.0000009 0.0000006 0.0000000

Acenaphthene 0.0000000 0.0000000 0.0000526

Acenaphthalene 0.0000000 0.0000000 0.0000853

Anthracene 0.0000488 0.0000334 0.0000304

Benzo(ghi)perylene 0.0000004 0.0000003 0.0000002

Fluoranthene 0.0000896 0.0000613 0.0000457

Fluorene 0.0000990 0.0000677 0.0001963

Naphthalene 0.0000000 0.0000000 0.0163278

Phenanthrene 0.0007886 0.0005395 0.0008507

Pyrene 0.0000859 0.0000588 0.0000379
18 

3.1.3. Metals

Emissions factors for chromium, magnesium, and nickel from pre-2007 diesels were based 

on data from the CRC E-75 test program. Emission factors for 2007 and later diesels are from 

the ACES test program. Emission factors for mercury and arsenic were obtained from the same 

2005 EPA test program and tunnel study as the gasoline vehicle emission factors. They do not 

vary with emission control technology. Table 15 provides metal emission factors for heavy duty 

engines.

Table 15. Metal emission factors for diesel vehicles and trucks.

3.1.4. Dioxins 

MOVES estimates emissions for 17 dioxin and furan congeners (Table 16). The 

emissions are estimated using mg/mile emission factors. These emission factors were obtained 

from EPA’s dioxin assessment.26 

Pollutant Pre-2007 

Emission Rate (g/mi) 

2007 and Later 

Emission Rate (g/mi) 

Chromium 3+ 5.6x10-6 1.6x10-6

Chromium 6+ 1.2x10-6 3.4x10-7

Manganese 8.0x10-6 5.5x10-7

Nickel 1.4x10-5 6.5x10-7

Elemental Gas Phase Hg 6.2x10-9 6.2x10-9

Reactive Gas Phase Hg 3.2x10-9 3.2x10-9

Particulate Hg 1.6x10-9 1.6x10-9

Arsenic 2.3x10-6 2.3x10-6
19 

Table 16. Dioxin/furan emission factors for diesel vehicles and trucks.

3.2. Evaporative 

MOVES estimates evaporative emissions associated with spillage for diesel vehicles. 

Since there are no speciated emissions of diesel spillage emissions, we developed toxic to VOC 

ratios based on a diesel headspace profile, profile number 4547 from the SPECIATE database. 

These ratios are provided in Table 17. 

Table 17. Toxic to VOC ratios for diesel spillage emissions.

Pollutant Toxic/VOC

2,2,4-Trimethylpentane 0.00974

Ethyl Benzene 0.00324

Hexane 0.01076

Toluene 0.01419

Xylene 0.01222

Benzene 0.00410

 

Pollutant Mg/mi

2,3,7,8-TCDD TEQ 5.52E-08

1,2,3,7,8-Pentachlorodibenzo-p-Dioxin 4.67E-08

1,2,3,4,7,8-Hexachlorodibenzo-p-Dioxin 6.57E-08

1,2,3,6,7,8-Hexachlorodibenzo-p-Dioxin 1.29E-08

1,2,3,7,8,9-Hexachlorodibenzo-p-Dioxin 2.37E-07

1,2,3,4,6,7,8-Heptachlorodibenzo-pDioxin 1.55E-06

Octachlorodibenzo-p-dioxin 7.14E-06

2,3,7,8-Tetrachlorodibenzofuran 1.39E-07

1,2,3,7,8-Pentachlorodibenzofuran 5.55E-08

2,3,4,7,8-Pentachlorodibenzofuran 1.23E-07

1,2,3,4,7,8-Hexachlorodibenzofuran 2.08E-07

1,2,3,6,7,8-Hexachlorodibenzofuran 9.47E-08

1,2,3,7,8,9-Hexachlorodibenzofuran 5.51E-08

2,3,4,6,7,8-Hexachlorodibenzofuran 1.37E-07

1,2,3,4,6,7,8-Heptachlorodibenzofuran 4.30E-07

1,2,3,4,7,8,9-Heptachlorodibenzofuran 4.89E-08

Octachlorodibenzofuran 4.91E-07
20 

 

1

 U. S. EPA. 2010. Motor Vehicle Emission Simulator (MOVES) 2010: User Guide. Report 

No. EPA-420-B-09-041. Available at http://www.epa.gov/otaq/models/moves/420b09041.pdf. 

2

 U. S. EPA. 2004. MOBILE6 Vehicle Emissions Model. Available at 

http://www.epa.gov/otaq/m6.htm. 

3

 Michaels, H.; Brzezinski, D.; Cook, R. EPA’s National Mobile Inventory Model (NMIM), A 

Consolidated Emissions Modeling System for MOBILE6 and NONROAD; EPA-420-R-05-003, 

U. S. Environmental Protection Agency, Office of Transportation and Air Quality, Assessment 

and Standards Division, Ann Arbor, MI, 2005. (Available at 

http://www.epa.gov/otaq/nmim.htm).

4

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

1993. Available at http://www.epa.gov/otaq/regs/fuels/rfg/

 

5

 Michaels, H., Brzezinski, D., Cook, R. 2005. EPA’s National Mobile Inventory Model 

(NMIM), A Consolidated Emissions Modeling System for MOBILE6 and NONROAD. U. S. 

EPA, Office of Transportation and Air Quality, Assessment and Standards Division, Ann Arbor, 

MI, March 2005; Report No. EPA-420-R-05-003. Available at 

http://www.epa.gov/otaq/nmim.htm. 

6

Sierra Research, 2010. Development of Emission Rates for the MOVES Model. Prepared for 

the U. S. Environmental Protection Agency by Sierra Research, Sacramento, CA, July 2, 2010. 

Sierra Research Report No. SR2010-07-01. 

7 U. S. EPA. 2009. Exhaust Emission Profiles for EPA SPECIATE Database: Energy Policy Act 

(EPAct) Low-Level Ethanol Fuel Blends and Tier 2 Light-Duty Vehicles. Assessment and 

Standards Division, Office of Transportation and Air Quality. Report No. EPA-420-R-09-002. 

8

 Michaels, H., Brzezinski, D., Cook, R. 2005. EPA’s National Mobile Inventory Model 

(NMIM), A Consolidated Emissions Modeling System for MOBILE6 and NONROAD. U. S. 

EPA, Office of Transportation and Air Quality, Assessment and Standards Division, Ann Arbor, 

MI, March 2005; Report No. EPA-420-R-05-003. Available at 

http://www.epa.gov/otaq/nmim.htm. 

9

 Watson, J. D., E. Fujita, J. C. Chow, and B. Zielinska. 1998. Northern Front Range Air Quality 

Study. Desert Research Institute. See Table 4.4-4, page 4-41. 

10 U. S. EPA, 2001. Revised Methodology and Emission Factors for Estimating Mobile Source 

PAH Emissions in the National Toxics Inventory. Memorandum from Rich Cook and Joseph 

Somers, Office of Transportation and Air Quality, to Laurel Driver, Office of Air Quality 

Planning and Standards, June 11, 2001. 
21 

 11Sierra Research, 2010. Development of Emission Rates for the MOVES Model. Prepared for 

the U. S. Environmental Protection Agency by Sierra Research, Sacramento, CA, July 2, 2010. 

Sierra Research Report No. SR2010-07-01. 

12U.S. EPA, 2009. SPECIATE 4.2 Speciation Database Development Documentation, Office of 

Research and Development. Report No. EPA/600-R-09/038, June 2009. 

13 Schauer, J.J., M.J. Kleeman, G.R. Cass, and B.R.T. Simoneit. Measurement of Emissions 

from Air Pollution Sources, 2. C1-C30 Organic Compounds from Medium Duty Diesel Trucks. 

Environmental Science and Technology, vol. 33, no. 10, pp. 1578-1587, 1999. 

14 Norbeck, J. M., T. D. Durbin, and T. J. Truex. 1998. Measurement of Primary Particulate 

Matter Emissions from Light Duty Motor Vehicles. Prepared by College of Engineering, Center 

for Environmental Research and Technology, University of California, for Coordinating 

Research Council and South Coast Air Quality Management District. See Tables 16 and 17. 

15 U. S. EPA. 2009. Development of Emission Rates for Light-Duty Vehicles in the Motor 

Vehicle Emissions Simulator: Draft Report. Assessment and Standards Division, Office of 

Transportation and Air Quality, Ann Arbor, MI, August 2009. Report No. EPA-420-P-09-002. 

http://www.epa.gov/otaq/models/moves/techdocs/420p09002.pdf

16 Ball, James C. Emission Rates and Elemental Composition of Particles Collected From 1995 

Ford Vehicles Using the Urban Dynamometer Driving Schedule, the Highway Fuel Economy 

Test, and the USO6 Driving Cycle. 97FL-376. Society of Automotive Engineers, Inc. 1997. 

17 Taylor, M. Memorandum: Revised HAP Emission Factors for Stationary Combustion 

Turbines, Prepared by Alpha-Gamma Technologies, Inc for Sims Roy, EPA OAQPS ESD 

Combustion Group. August, 2003.Docket ID: OAR-2002-0060-0649. 

Access via http://www.regulations.gov

18 Schauer, J. J., Lough, G. C., Shafer M. M., Christensen W. F., Arndt, M. F., DeMinter, J.T., 

Park, J-S. 2006, Characterization of Metals Emitted from Motor Vehicles. 

Health Effects Institute Research Report Number 133, available at:

http://pubs.healtheffects.org/

19 U. S. EPA. Draft Final Assessment: Exposure and Human Health Reassessment of 2,3,7,8- 

Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds. Volume 2: Sources of DioxinLike Compounds in the United States. Office of Research and Development, National Center for 

Environmental Assessment, Washington, D.C. Report No. EPA/600/P-00/001Bb, September 

2000. 

20C.E. Lindhjem, Emission Profiles for EPA SPECIATE Database, EPA Contract No. EP-C-06-

094, Work Assignment No. 1-7, ENVIRON International Corporation, January 31, 2008. 

21Southwest Research Institute. 2009. Evaporative Emissions Breakdown Including Permeation 

Effects and Diurnal Emissions on Aging Enhanced Evaporative Emissions Certified Vehicles 
22 

 

(CRC E-77-2b). Prepared by Harold M. Haskew and Thomas F. Liberty, Harold Haskew and 

Associates, Inc.; submitted to U. S. EPA, December, 2009. Available at www.crcao.org. 

22 Haskew, H. M., Liberty, T. F., and McClement, D. 2004. Fuel Permeation from Automotive 

Systems. Prepared for the Coordinating Research Council by Harold Haskew and Associates 

and Automotive Testing Laboratories, Inc. September 2004. CRC Project No. E-65. 

http://www.crcao.com. 23

24 Hsu ,Y., and Mullen, M. 2007. Compilation of Diesel Emissions Speciation Data. Prepared 

by E. H. Pechan and Associates for the Coordinating Research Council. CRC Contract No. E75, October, 2007. Available at www.crcao.org. 

25Khalek, I., Bougher, T., and Merritt, P. M. 2009. Phase 1 of the Advanced Collaborative 

Emissions Study. Prepared by Southwest Research Institute for the Coordinating Research 

Council and the Health Effects Institute, June 2009. Available at www.crcao.org. 

26 U. S. EPA. Draft Final Assessment: Exposure and Human Health Reassessment of 2,3,7,8- 

Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds. Volume 2: Sources of DioxinLike Compounds in the United States. Office of Research and Development, National Center for 

Environmental Assessment, Washington, D.C. Report No. EPA/600/P-00/001Bb, September

2000. 
Appendix A: Documentation of Development of Motor Vehicle 

Emission Factors for Mercury
A-2 

Calculation of Mercury Emission Factors from Vehicle Tests 

In 2005, the National Exposure Research Laboratory (NERL) of the EPA collected 

mercury samples in the raw exhaust from 14 light-duty gasoline vehicles and two heavy-duty 

diesel vehicles. The work plan for this project includes details of the methods used that are not 

reproduced here including quality assurance and quality control for Hg collection and analysis. 

This information can be obtained from EPA upon request. Briefly, mercury and regulated 

pollutant data were collected during two sets of three consecutive LA92 drive cycles for each 

vehicle. The morning set of LA92 cycles began with one ‘cold start’ and the afternoon set of 

three LA92 cycles began with a ‘hot start’. The intake air was prefiltered through charcoal to 

greatly reduce background mercury concentrations going into the vehicle intake. Separate 

sampling lines were used for gas and particle mercury species. Samples analyzed for mercury 

were drawn from raw exhaust at a constant flow rate and fixed dilution. Carbon dioxide 

measurements were also taken in the exhaust stream where mercury samples were collected.

Mercury samples were collected in raw exhaust since previous data suggested that 

mercury levels might be sufficiently low to challenge mercury detection limits. This sampling 

method imposed a challenge in calculating emission factors since it assumes that the exhaust 

flow rate from the vehicle is constant. Calculation of exhaust flow and how this was applied to 

the development of mercury emission factors is described below. 

Evaporative losses of mercury from motor vehicles and loss of mercury during refueling 

were not measured and therefore not included in the National Emissions Inventory. The 

emission of mercury from these evaporative sources is expected to be small compared with the 

combustion exhaust emissions of mercury from mobile sources. 

A description of the vehicles tested for which data were used in developing emission 

factors is provided in Table 1. The data collected from these vehicles in diluted exhaust in the 

constant volume sampler (CVS) included total hydrocarbon (THC), carbon dioxide (CO2), 

nitrogen oxides (NOx), methane (CH4), and carbon monoxide (CO). In raw, undiluted exhaust, 

data collected included elemental and total gas-phase mercury, particulate mercury and CO2. 

Gas-phase mercury was also measured in the intake air. Total air flow and standard temperature 

and pressure-corrected flows for all the sampling systems were measured. The data streams had 

different reporting frequencies, all due to the nature of the instrumentation. The dilute 

measurement of the standard emission gases (THC, CO2, NOx, CH4, and CO), CVS flows, and 

vehicle speed were reported at 1 Hertz. The gas-phase mercury samples were analyzed at 2.5 

minute intervals and particle-phase mercury samples were collected cumulatively for the 

duration of three consecutive LA92 cycles. Gas-phase elemental mercury in the engine intake 

air was measured in 5 minute intervals. 
A-3 

Table 1. Vehicles tested for Mercury Emissions

Model 

Year Make Model Fuel Type Odometer Cylinders Displacement

2005 MERCURY

GRAND MARQUIS 

LS Gasoline 9,953 8 4.6

2005 FORD

MUSTANG 

CONVERTIBLE Gasoline 5,424 6 4 

2003 SATURN L 200 Gasoline 29,667 4 2.2

2002 HONDA ACCORD EX Gasoline 51,824 4 2.3

2001 HONDA ACCORD EX Gasoline 88,611 4 2.3

2001 CHRYSLER PT CRUISER Gasoline 54,010 4 2.4

2000 CHEVROLET SUBURBAN Gasoline 39,787 8 6 

2000 JEEP CHEROKEE SPORT Gasoline 48,468 6 4

1999 FORD F250 XLT Diesel 113,897 8 7.3

1999 FORD F250 XLT SD Diesel 109,429 8 7.3

1998 HONDA CIVIC DX Gasoline 204,983 4 1.6

1994 CHEVROLET SILVERADO Gasoline 129,521 8 5.7

1992 CHEVROLET S10 BLAZER Gasoline 162,249 6 4.3

1991 HONDA ACCORD EX Gasoline 143,289 4 2.2

1987 CHRYSLER FIFTH AVENUE Gasoline 72,573 8 5.2

1984 FORD F150 PICKUP Gasoline 36,727 8 5.8

Exhaust flow was integrated at the same reporting frequency as the mercury exhaust 

values for a particular test and then used to calculate total, elemental, and reactive gas-phase 

mercury mass emissions. The intake air mercury values were typically collected at half the 

frequency of the mercury exhaust values. There is precedent in accepting background values 

measurements at less frequent intervals and using them to correct exhaust measured values that 

are reported at higher frequencies. The particulate matter measurements were filter-based, testlevel measurements and were reported in that manner.

Calculation of Emission Rates 

The data for regulated pollutants and mercury were time-aligned; however, emissions 

data were not attributed to vehicle specific power as the data are not to be used in modal 

emissions modeling at this time. Emission rates were calculated separately for elemental gasphase mercury, reactive gas-phase mercury and particulate mercury. Elemental gas-phase 

mercury in the exhaust was corrected for the intake air concentration of elemental mercury. To 

estimate the gas-phase mercury concentration in dilute exhaust from the measured mercury in 

raw exhaust, the dilution factor was applied. For light-duty gasoline vehicles, the dilution factor 

equation found in 40 CFR 90.426 (d) was used: 

Dilution factor = 13.4 / ([CO2%] + ([THC, ppm] + [CO, ppm])* 0.0001) 

Exhaust flow = (CVS flow / dilution factor) 
A-4 

Exhaust flow calculation was initiated when the analytical equipment indicated that the 

dilute exhaust CO2 concentration was greater than the background CO2 concentration. 

To calculate exhaust flow for the diesel vehicles, the dilution factor was calculated by 

simply dividing CO2 in the raw exhaust by CO2 in the CVS. This method was used because 

diesel engines operate across a very wide range of fuel to air mixtures and the CFR method 

described above was not appropriate.

Determination of Reactive Gas Mercury Mass in Exhaust 

Reactive gas mercury (RGM) was calculated by subtracting elemental gas-phase mercury 

measurements from total gas-phase mercury measurements. RGM values were typically small 

and therefore influenced by the variability in the elemental mercury measurements. Negative 

RGM values for a given measurement period were observed. Values for which there was not a 

positive RGM measurement were treated as non-detects and were nulled in the aggregation of 

RGM values for the test. The measurement uncertainty for gas-phase elemental mercury was 

estimated from quantitative recovery of injections of known amounts of mercury into the 

sampling system. The uncertainty in measuring elemental mercury was applied to the total gasphase and elemental gas-phase measurements to determine when the RGM value was above the 

measurement uncertainty. Values within the measurement uncertainty were not included in the 

emission factor calculation. 

Calculating Weighted Emission Test Results

Highway vehicle tests used the California Air Resource Board’s LA92, a more aggressive 

chassis dynamometer test similar in concept to the Federal Federal Test Procedure’s (FTP) 

UDDS or LA4. Like the FTP, the LA92 includes a cold start, a hot start, and a hot stabilized 

phase using identical drive schedules for the starts and for the stabilized phase. It was, therefore, 

considered appropriate to follow the precedent of calculating a weighted emission factor 

(representing cold start and hot start driving) for each vehicle in the same manner as the FTP, 

using the equation below for each test (a test consisting of all six LA92 cycles performed on each 

vehicle).

We summed the gas-phase mercury mass emissions for the first phase (300 seconds) of 

the morning test and last phase (1,135 seconds) of the individual LA92 drive schedules for all the 

tests (e.g., ‘hot stabilized emissions’), divided by the total distance covered in these phases and 

multiplied by 0.43. We also summed the sum of the mass gas-phase mercury emissions of the 

first phase of the afternoon test and last phase (1,135 seconds) of all the tests, divided by the total 

distance covered in these phases and multiplied by 0.57. The two terms were summed to 

calculate a test level emission rate for each of the gasoline powered vehicles.

Equation used to calculate test-level emission rates:

Grams/mile emission factor = 0.43*(C + R)/( Cm + Rm) + 0.57*(H+R)/( Hm + Rm) 

Where:
A-5 

C = mercury mass collected in the first 300 seconds of the first morning 

test (‘cold start’)

Cm = distance covered by the cold start

R = mercury mass collected in the last 1,135 seconds of all six cycles of 

the LA92 (‘hot stabilized’) 

Rm = cumulative distance covered by all six cycles of the LA92 (‘hot 

stabilized ’)

H = mercury mass collected in the first 300 seconds of the first afternoon 

test (‘hot start’)

Hm = distance covered by the hot start

It should be noted that the ‘hot start’ in the afternoon typically occurred after the vehicle 

had been off for at least 1 hour, making this start closer to a ‘cold start’ than ‘hot start’. Since 

the true cold start emissions were slightly higher than hot start emissions, it is expected that this 

approach would bias the emission factors high by a small amount. 

Particulate mercury emissions could not be apportioned into modes of operation in 

similar manner because filters were collected across all three LA92 cycles and could not be 

parsed into the three phases. A test-level emission rate was calculated by multiplying the 

morning particulate mercury emission rate by 0.43 and the afternoon particulate mercury 

emission rate by 0.57 and adding the two values together. 

The average of emission factors across vehicles was calculated for each form of mercury 

and is reported in Table 2. A simple average was used since the data did not suggest that 

mercury concentrations varied by vehicle age, mileage, displacement or other factors. 

Mercury emission factors for on-road diesel engines were obtained from the first 715 

seconds of the morning and afternoon tests on the Ford F250 XLT SD; data from the second 

diesel vehicle could not be used. The first 715 seconds is approximately half of the first of the 

three LA92 drive cycles that made up a single test. The truncation of the test was due to sample 

flow problems in the mercury sampling manifold due to particulate matter restricting flow across 

the particulate matter filters. Graphical analysis of exhaust flow indicated that at they appeared 

nominal during the first LA92 cycle. It was decided that only using data collected before 715 

seconds into both tests provided the most reliable data.
A-6 

Table 2. Mercury Emission Factors from Mobile Sources 

Source Category Pollutant Pollutant 

Code

Emission 

Factor

Units

Gasoline motor 

vehicles

Elemental gasphase mercury200 1.1E-07 grams/mile

Reactive gasphase mercury201 9.9E-09 grams/mile

Particulate 

mercury

202 4.0E-10 grams/mile

Diesel motor 

vehicles

Elemental gasphase mercury200 6.2E-09 grams/mile

Reactive gasphase mercury201 3.2E-09 grams/mile

Particulate 

mercury

202 1.6E-09 grams/mile

Gasoline nonroad

engines

Elemental gasphase mercury200 1.8E-06 grams/gallon

Reactive gasphase mercury201 1.7E-07 grams/gallon

Particulate 

mercury

202 6.9E-09 grams/gallon

Diesel nonroad 

engines

Elemental gasphase mercury200 1.2E-07 grams/gallon

Reactive gasphase mercury201 6.2E-08 grams/gallon

Particulate 

mercury

202 3.2E-08 grams/gallon