1

MEMORANDUM

To: Toxics Rule docket, number EPA-HQ-OAR-2009-0234

From: Madeleine Strum, Emission Inventory and Analysis Group

Marc Houyoux, group leader Emission Inventory and Analysis Group

Subject: Emissions Overview: Hazardous Air Pollutants in Support of the Proposed Toxics Rule

Date: March 15, 2011

1 Introduction

The purpose of this document is to summarize the mercury (Hg) and non-Hg Hazardous Air 

Pollutants (HAPs) emissions associated with the proposed Toxics Rule. This information includes both 

background on these pollutants as well as emissions totals from several emissions cases developed for the 

proposed Toxics Rule.

2 Mercury

Mercury is an element. There is a fixed amount of it in the world. As long as it is bound up, for 

example in coal, it cannot affect people or the environment. Once it is released, for example via the 

combustion process, it enters the environment and becomes available for chemical conversion. Once 

emitted, Hg remains in the environment and can bioaccumulate in organisms or be remitted through natural 

processes. Mercury is emitted through natural and anthropogenic processes and previously deposited Hg

from either process may be re-emitted. The majority of natural Hg emissions arise from volcanoes, 

geothermal activity, Hg-enriched topsoil, oceans/lakes, and vegetation. The category of natural Hg

emissions may or may not include biomass burning, due to the difficulty in determining whether biomass 

burning events are started by anthropogenic or natural causes. Generally, natural Hg emissions are 95 

percent elemental mercury (Hg0), and as a result have more impact on the global pool of Hg than on 

deposition in the region of the emissions; however, the emissions from wildfires have a greater percentage of 

particulate mercury (HgP) (15 percent).

The categories for anthropogenic Hg emissions include the combustion of fossil-fuels, cement 

production, waste incineration, metals production, and other industrial processes. Anthropogenic Hg 

emissions consist of Hg0, HgP, and divalent gaseous mercury (Hg+2).

Mercury re-emissions include previously deposited Hg originating from both natural and 

anthropogenic sources. At this time, it is not possible to determine the original source of previously 

deposited Hg, i.e., whether its source is natural emissions or re-emissions from previously deposited 

anthropogenic Hg.1,2,3 Current publications on this topic estimate that half of re-emitted Hg originates from 

anthropogenic sources.4,5

 

1

 Lindberg, S., Bullock, R., Ebinghaus, R., Engstrom, D., Feng, X., Fitzgerald, W., et al. (2007). A Synthesis of Progress and 

Uncertainties in Attributing the Sources of Mercury in Deposition. Ambio, 36(1), 19-33.

2

 Lohman, K., Seigneur, C., Gustin, M., & Lindberg, S. (2008). Sensitivity of the global atmospheric cycle of mercury to 

emissions. Applied Geochemistry, 23(3), 454-466.

3

 Seigneur, C., Vijayaraghavan, K., Lohman, K., Karamchandani, P., & Scott, C. (2004). Global Source Attribution for Mercury 

Speciation in the United States. Environmental Science and Technology(38), 555-569.

4

 Mason, R., Pirrone, N., & Mason, R. P. (2009). Mercury emissions from natural processes and their importance in the global 

mercury cycle. In Mercury Fate and Transport in the Global Atmosphere (pp. 173-191): Springer U.S.

5

 Selin, N. E., Jacob, D. J., Park, R. J., Yantosca, R. M., Strode, S., Jaeglé, L., et al. (2007). Chemical cycling and deposition of 

atmospheric mercury: Global constraints from observations. J. Geophys. Res, 112, 1071-1077.
2

Current estimates of total global Hg emissions based on a 2005 inventory range from 7,300 to 8,300 

tons per year (tpy).

6,7

 The United Nations Environment Programme (UNEP) estimates of global Hg 

emissions for 2005 are somewhat lower, at 5,600 metric tpy8,9(which is about 6,200 tpy). Global 

anthropogenic Hg emissions, excluding biomass burning, have been estimated by many researchers. 

UNEP‟s estimate (2005) is approximately 2,100 tpy (with a range of 1,300 tpy to 3,300 tpy)10 and the 2005 

estimate by Pirrone, et al. is approximately 2,600 tpy. Global fossil-fuel fired power plants total 

approximately 500 to 900 tpy, a large fraction (25 to 35 percent) of the total global anthropogenic 

emissions.11,12 The U.S. contribution to global anthropogenic emissions has declined from 10 percent in 

1990 to 5 percent in 200513 due to reductions in U.S. emissions and increases in emissions from other 

countries. Although total U.S. anthropogenic Hg has decreased, the electric generating utilities (EGU) sector 

remains the largest contributor to the total. Table 1 below shows the trend of U.S. EGU Hg compared to the 

total U.S. inventory from 1990 through 2016. 

In 1990, U.S. EGU Hg emissions were 59 tons out of a total of 264 tons, and by 1999 U.S. EGU Hg

emissions were 49 out of 115 tons. In 2005, they were 53 tons out of a total of 105 tons. As part of the 

development of the Toxics Rule, EPA completed in 2010 an Information Collection Request (ICR) that 

gathered the latest available emissions data from EGU sources. One hundred eighty-six boilers reported 

emission factors (EFs) for Hg. These data were used to develop industry-wide average emission factors 

(EFs) associated with boiler configuration, which considers combinations of fuel type, boiler type, and 

control devices. The average emission factors were assigned to untested boilers based on configuration. The 

boiler-specific EFs from the test data and the average EFs were applied to the operating data gathered for all 

units (tested and untested). The operating data used for these calculations were the 3-year average capacity

factor for 2007 to 2009 and the boiler maximum heat input. The resultant estimates were used to represent a 

year 2010 EPA estimate of 29 tons of Hg from EGUs. More information on the ICR and the associated 

inventory is available in the Toxics Rule docket (EPA-HQ-OAR-2009-0234). The 2010 estimates reflect the 

U.S. EGU Hg reductions achieved since 1990, which include reductions resulting from the installation of Hg

controls to comply with state Hg-specific rules, voluntary reductions, as well as from the co-benefits of Hg

reductions from control devices installed for the reduction of SO2 and PM as a result of state and federal 

actions, such as New Source Review (NSR) enforcement actions.

 

6 Lindberg, S., Bullock, R., Ebinghaus, R., Engstrom, D., Feng, X., Fitzgerald, W., et al. (2007). A Synthesis of Progress and 

Uncertainties in Attributing the Sources of Mercury in Deposition. Ambio, 36(1), 19–33.

7

Pirrone, N., Cinnirella, S., Feng, X., Finkelman, R. B., Friedli, H. R., Leaner, J., et al. (2010). Global mercury emissions to the 

atmosphere from anthropogenic and natural sources. Atmospheric Chemistry and Physics Discussions, 10(2), 4719-4752.

8

 UNEP (United Nations Environment Programme), Chemicals Branch, 2008. The Global Atmospheric Mercury 

Assessment:Sources, Emissions and Transport, UNEP Chemicals, Geneva. 

9 The 5,600 metric ton estimate is from the Figure on page 37 of the report. The report also provides ranges in the executive 

summary.

10 Study on Mercury Sources and Emissions and Analysis of the Cost and Effectiveness of Control Measures “UNEP Paragraph 29 

study”, UNEP (DTIE)/Hg/INC.2/4. November, 2010.

11 Pirrone, N., Cinnirella, S., Feng, X., Finkelman, R. B., Friedli, H. R., Leaner, J., et al. (2010). Global mercury emissions to the 

atmosphere from anthropogenic and natural sources. Atmospheric Chemistry and Physics Discussions, 10(2), 4719-4752.

12 Study on Mercury Sources and Emissions and Analysis of the Cost and Effectiveness of Control Measures “UNEP Paragraph 29 

study”, UNEP (DTIE)/Hg/INC.2/4. November, 2010.

13 U.S. anthropogenic emissions of 105 tons in 2005 (Table 1) divided by global anthropogenic emissions of 2,100 tons (UNEP 

value for global anthropogenic emissions, stated above) is 5%.
3

Table 1: U.S. anthropogenic Hg emissions trends for U.S. EGUs.

1990

(tons)

1999

(tons)

2005

(tons)

20101

(tons)

Final 2016 Base Case2

(tons)

U.S. EGUs 59 49 53 29 29

Non-EGU Anthropogenic

U.S. Mercury 205 66 52 Not Available3 35

Total U.S. Anthropogenic 

Mercury 264 115 105 Not Available3 64

Percent of U.S. Anthropogenic Mercury Emissions from EGUs

1990 1999 2005 2010 2016

22% 43% 50% Not 

Available3 45%

1. We believe the estimate of the current level of Hg emissions based on the 2010 ICR database may 

underestimate total EGU Hg emissions due to targeting of the 2010 ICR on the best performing EGUs.

2. The 2016 base case scenario represents predicted emissions including known Federal measures for all 

sectors. It reflects projected economic changes and fuel usage for the EGU and mobile sectors. Note that 

the projected future year inventory used for this analysis is generally representative of several years 

around 2016 such as 2015. The term “Final” is used to indicate that the EGUs were projected utilizing 

the final version of the IPM version 4.10 developed for the Proposed Toxics Rule as opposed to the 

Interim version. “Base” indicates that these are the projected emissions in absence of the Proposed 

Toxics Rule policy. 

3. Information on recent U.S. EGU emissions was obtained using an Information Collection Request for 

EGUs only. This same information is not available for other sources, which were not covered by the 

Information Collection Request. 

Table 1 above shows past U.S. emissions of Hg as well as future emission projections to the year 

2016. The Integrated Planning Model (IPM) was used to estimate future-year Hg emissions for U.S. 

EGUs.14 More information on IPM is available in the “Documentation Supplement for EPA Base Case 

v.4.10 PTR – Updates for Proposed Toxics Rule” which can be found in the Toxics Rule docket (EPA-HQOAR-2009-0234).

Below, Table 2 provides the projections for non-EGU emission sources that include expected future 

reductions from existing and proposed regulations for HAPs that were finalized or are expected to be 

finalized prior to this proposal. These regulations include Portland Cement; Industrial, Commercial and 

Institutional Boilers and Process Heaters; Gold Ore Mining and Production, Electric Arc Furnaces, 

Hazardous Waste Incineration, and Mercury Cell Chlor-alkali facilities. The projections also include the 

replacement of a smelter and a pulp and paper plant, which will result in the elimination of Hg emissions, 

along with other known plant closures. This projection shows that U.S. EGU emissions will continue to 

comprise a significant, dominant portion of the total U.S. anthropogenic inventory in 2016. In 2016, U.S. EGU 

Hg is projected to be 29 tons out of a total of 64 tons. More information on the non-EGU projections of Hg is 

available in the Emission Inventory Technical Support Document (TSD) for the proposed Toxics Rule.

 

14

 IPM is a multi-regional, dynamic, deterministic linear program model of the U.S. power sector that determines the least cost 

solution to meeting a set of environmental constraints while still meeting specified electric demand. For more detail on IPM see: 

http://www.epa.gov/airmarkets/progsregs/epa-ipm/index.html
4

Table 2: Anthropogenic Hg emissions and projections in the Continental U.S.

Category

2005 

Mercury 

(tons)

2016 

Mercury 

(tons)

Electric Generating Units 53 29

Portland Cement Manufacturing 7.5 1.1

Stainless and Nonstainless Steel Manufacturing: Electric Arc Furnaces 7.0 4.6

Industrial, Commercial, Institutional Boilers & Process Heaters 6.4 4.6

Chemical Manufacturing 3.3 3.3

Hazardous Waste Incineration 3.2 2.1

Mercury Cell Chlor-Alkali Plants 3.1 0.3

Gold Mining 2.5 0.7

Municipal Waste Combustors 2.3 2.3

Sum of other source categories (each of which emits less than 2 tons) 17 16

Total 105 64

3 Non-Hg HAP Emissions

Fossil-fuel fired boilers emit a variety of metal HAP, organic HAP and HAP that are acid gases. Acid gas 

and metal HAP emissions are discussed below.

3.1 Acid Gases

Acid gas emissions from EGUs include hydrogen chloride (HCl), hydrogen fluoride (HF), chlorine 

(Cl2) and hydrogen cyanide (HCn). These pollutants are emitted as a result of fluorine, chlorine, and 

nitrogen components of the fuels. Table 3 shows emissions of certain acid gases from EGUs, based on the 

2010 ICR data by fuel type. Although Cl2 was not included in the data collected from the 2010 ICR, Cl2 gas 

is expected to be emitted at significantly lower amounts than HCl (ratios of HCl-to- Cl2 can be as high as 

200:115). 

Similar to the Hg estimates, the 2010 ICR data for the acid gases included emission factors generated 

from boiler-specific emission tests (acid gas emission factors based on test data were generated for 186 

boilers). Year 2010 estimates are not available for other U.S. anthropogenic emission sources, so the latest 

available complete set of data, 2005, were used to approximate the percentage contribution of EGUs to total 

U.S. anthropogenic emissions. As illustrated by Table 3, U.S. EGUs are estimated to emit the majority of 

HCl and HF nationally. 

 

15

 200:1 is based on testing done at the EPA‟s pilot facility in Research Triangle Park, NC. Personal communication, Nick Hutson

(email to Madeleine Strum from Nick Hutson 01/30/2011 11:16 pm).
5

 Table 3: Summary of acid gas emissions from EGU sources.

Selected Nationwide Acid HAP emissions 

(tons/yr) in 2010 from EGUs

2005 Acid HAP 

Emissions (tons/yr)

from the inventory 

used for the National 

Air Toxics 

Assessment (NATA)1

Percent of U.S. 

Anthropogenic

Emissions from 

EGUs, based on 

the inventory used 

for the 2005 NATA

Coal IGCC2 PC3 Oil Total 2010 

EGU4

Total 

2005

EGU

2005 

NonEGU 

Hydrogen 

Cyanide5 7,678 1 76 107 7,900 1,200 14,000 8%

Hydrogen 

Chloride 105,507 2 72 304 106,000 350,000 78,000 82%

Hydrogen 

Fluoride 36,345 1 8 79 36,000 47,000 28,000 62%

1 2005 NATA: http://www.epa.gov/ttn/atw/nata2005/ EGU emissions were extracted from the total using the MACT code 

field (1808)

2

IGCC = integrated gasification combined cycle

3

 PC = petroleum coke

4 We believe our estimate of the current level of acid gas emissions based on the 2010 ICR database may underestimate 

total EGU emissions due to targeting of the 2010 ICR on the best performing EGUs.

5

 Used cyanide emissions for hydrogen cyanide

3.2 Metal HAP

Metals are emitted primarily because they are present in fuels. Table 4 shows selected metals emitted 

by EGUs and emission estimates based on data from the 2010 ICR. Similar to the Hg and acid gas estimates, 

the 2010 ICR data for the metal HAPs included emission factors generated from boiler-specific emission 

tests (metal emission factors based on test data were generated for 196 boilers). Year 2010 estimates are not 

available for other U.S. anthropogenic emission sources, so the latest available complete set of data, 2005, 

was used to approximate the percentage contribution of EGUs to total U.S. anthropogenic emissions.
6

Table 4: Summary of metal emissions from EGU sources.

Selected Nationwide Metal HAP 

emissions(tons/yr) in 2010 from EGUs

2005 Metal HAP 

Emissions from the 

inventory used for the 

National Air Toxics 

Assessment (NATA)1

Percent of U.S. 

Anthropogenic 

Emissions from 

EGUs, based on the 

inventory used for the 

2005 NATA

Coal IGCC2PC3 Oil

Total 

2010 

EGU4

Total 2005

EGU

2005 NonEGU

Antimony 8 0 0 16 25 19 83 19%

Arsenic 42 0 1 1 43 200 120 62%

Beryllium 2 0 0 0 2 10. 13 44%

Cadmium 3 0 0 0 3 25 38 39%

Chromium 216 0 0 6 222 120 430 22%

Cobalt 11 0 0 8 19 54 60. 47%

Manganese 168 0 0 15 183 270 1800 13%

Nickel 198 0 0 188 387 320 840 28%

Selenium 257 0 0 1 258 580 120 83%

1

2005 NATA: http://www.epa.gov/ttn/atw/nata2005/ EGU emissions were extracted from the total using the MACT code 

field (1808)

2

IGCC = integrated gasification combined cycle

3

PC=petroleum coke

4 We believe our estimate of the current level of metal emissions based on the 2010 ICR database may underestimate total 

EGU metal emissions due to targeting of the 2010 ICR on the best performing EGUs.

As shown by the table, U.S. EGUs are estimated to be a significant source of emissions nationally for 

these metals.

3.3 Expected Impact on Non-Hg HAP Emissions from Existing Clean Air Act (CAA) and Other 

Regulations and Programs

It is expected that acid gas and metal emissions will be reduced in the future due to existing CAA and 

other regulations and programs. Acid gases and metals are emitted by a number of other industries already 

regulated or scheduled for regulation under the National Emissions Standards for Hazardous Air Pollutants 

(NESHAP) or the Risk and Technology Review (RTR) program. In addition, because acid gases respond 

somewhat to the same types of controls used for SO2, it is expected that acid gas emissions will be reduced at 

both EGU and non-EGU sources as a result of national, state, and local control programs to control SO2. 

Likewise, metals respond to the same types of controls used for PM, and as a result it is expected that metal 

emissions will be reduced at both EGU and non-EGU sources due to national, state, and local control programs 

to control direct PM.

4. Hg and non-Hg HAP Emissions Used for the Quantitative Risk Characterizations to Inform the 

Appropriate and Necessary Finding

This section summarizes the emissions used in the national scale assessments conducted to inform the 

appropriate and necessary finding. It also includes the 2010 ICR data, which is cited above and was used for 

site-specific case studies conducted to evaluate inhalation risks of U.S. EGU non-Hg HAP emissions. The

emissions used for the national scale efforts are described in more detail in the two emission inventory 

technical support documents associated with this rule: (1) the 2005 version 4.1 Platform TSD and (2) the 
7

Emission Inventory TSD for the proposed Toxics Rule. These documents and the IPM results are available in 

the Toxics Rule docket. More information on the emissions used for the case studies can be found in the 

memorandum entitled “Non-Hg Case Study Chronic Inhalation Risk Assessment for the Utility MACT 

„Appropriate and Necessary‟ Analysis, Memorandum to Docket EPA-HQ-OAR-2009-0234”.

The national scale mercury risk analysis is based on modeling mercury deposition associated with 

2005 U.S. EGU mercury emissions and on 2016 projected mercury emissions before implementation of 

federally mandated U.S. EGU mercury emissions controls. The emission sources and the basis for the 

analyses described in this section are listed in Table 5. The 2005 base-year emissions case is used for air 

quality modeling of the 2005 base year and contains emissions of criteria pollutants, Hg, HCl, and Cl2 from 

all source categories. All emissions except Hg come from the 2005 version 4.1 modeling platform, which is 

derived from the 2005 National Emissions Inventory (NEI). 2005 Hg emissions for all sources come from 

the 2005 National Air Toxics Assessment (NATA) inventory, a revised version16 of the 2005 NEI, which 

was further revised in this effort for non-EGU point and nonpoint sources based on data collected from the 

NESHAP for industrial, commercial and institutional boilers (a.k.a. the Boiler MACT). The 2010 ICR case 

contains emissions only for U.S. EGUs, and the Hg, HCl, and metal emissions in this inventory are based on 

the 2010 ICR data. 

The interim 2016 base projected emissions were developed for use in modeling based on the latest 

available projection techniques and account for emissions reductions of all modeled pollutants from Federal 

measures. The interim 2016 policy case projected emissions are an interim version of the expected 

emissions from EGUs after reductions associated with the Toxics Rule. The interim 2016 EGU emissions 

for both the base and Toxics Rule policy cases were created using an interim version of the IPM because the 

modeling needed to be completed in advance of the final IPM revisions associated with the Toxics Rule.

The non-EGU source emissions were created for the interim 2016 base projected emissions, and these are 

described in the Emission Inventory TSD for the Toxics Rule. These emissions were used for all other 2016 

emission cases listed in Table 5.

After IPM was finalized and all policy decisions made for the proposed Toxics Rule, the resulting 

emissions are labeled as the final 2016 base and policy cases. The final IPM emissions are cited in the 

preamble for the Toxics Rule and in any summaries stating the final 2016 emissions associated with the rule 

generally. Due to timing considerations, the final base and policy case emissions were not used in the 

modeling.

 

16

 Mercury revisions for NATA primarily affected non-EGU sources such as cement kilns and hazardous waste combustors.
8

Table 5: Emission sources and basis for current and future-year emissions inventories.

Emissions 

Case Pollutants Sector Emissions source

2005 base year Criteria 

pollutants, 

hydrogen 

chloride, and 

chlorine

EGU

Non-EGU point

Non-point

Mobile

2005 emissions from the version 4.1 

modeling platform, derived from the 2005 

National Emission Inventory (NEI) data

Hg EGU

Mobile

2005 National Air Toxics Assessment 

(NATA) data

Non-EGU point

Non-point

2005 NATA data, adjusted to account for 

Boiler MACT ICR data

2010 ICR 

Emissions

Mercury, 

hydrogen 

chloride, and 

metals

EGU 2010 Utility MACT ICR: EGU emissions 

inventory based on unit-specific emission 

factors for tested units and average emission 

factors for untested units.

Interim 2016 

Base Case 

projections

Criteria 

pollutants, 

mercury and 

hydrogen 

chloride

EGU Interim IPM v.4.10, including the Transport 

Rule Proposal

Non-EGU point

Nonpoint

Mobile

Emissions from the version 4.1 modeling 

platform: projected 2005 emissions to 

account for all known national rules, 

consent decrees, and plant closures

Interim 2016 

Policy Case 

projections

Criteria 

pollutants, 

mercury and 

hydrogen

chloride

EGU Interim IPM v.4.10, including the Transport 

Rule Proposal and interim Toxics Rule 

Proposal

Non-EGU point

Nonpoint

Same as interim 2016 base projections

Final 2016 

Base Case 

projections

Criteria 

pollutants, 

mercury and 

hydrogen 

chloride 

EGU IPM v.4.10, including the Transport Rule 

Proposal

Non-EGU point

Nonpoint

Mobile

Same as interim 2016 base projections

Final 2016 

Policy Case 

projections

Criteria 

pollutants, 

mercury and 

hydrogen 

chloride 

EGU IPM v.4.10, including the Transport Rule 

Proposal and Toxics Rule Proposal

Non-EGU point

Nonpoint

Same as interim 2016 base projections

Table 6 summarizes the Hg and HCl emissions for the anthropogenic sources of these emissions 

across the various cases. The 2005 base case includes 105 tons of Hg and 430,000 tons of HCl from all 

sources, of which 53 tons of Hg and 350,000 tons of HCl are from EGUs. The 2010 ICR shows the EGU Hg 

and HCl totals are lower than in 2005, at 29 tons and 106,000 tons respectively. The interim 2016 base total 

Hg emissions from all sources are 64 tons and HCl emissions are 140,000 tons, with 29 tons of Hg and 

74,000 tons of HCl from EGUs. For the interim Toxics Rule policy case, total Hg was estimated to be 42 

tons, with 6.8 tons from EGUs. For HCl, the interim Toxics Rule policy case shows a total of 75,000 tons 

from all sources with EGU emissions emitting 8,800 tons. The final Toxics Rule policy case for Hg from all 
9

sources is 42 tons with EGUs contributing 6.4 tons. For HCl, total emissions are 77,000 tons with EGUs 

contributing 6,600 tons.

Table 6. Summary of mercury and HCl emissions for emissions cases.

Hg(0)

(tons)

Hg(2+)

(tons)

Hg(p)

(tons)

Total Hg 

(tons)

Hydrogen 

chloride 

(tons)

2005 Base Case Emissions (tons)

EGU *30 21 1.6 53 350,000

NonEGU Point 30 11 6.2 46 49,000

Nonpoint 3.1 1.06 0.65 4.8 29,000

Mobile 0.79 0.29 0.13 1.2

All sources 64 33 8.5 105 430,000

2010 ICR Emissions (tons)

EGU 29 106,000

Interim 2016 base case projections (tons)

EGU**21.1 6.9 0.67 28.7 74,000

NonEGU Point 16.9 7.9 4.4 29.2 38,000

Nonpoint 3.1 1.06 0.65 4.8 29,000

Mobile 0.79 0.29 0.13 1.2

All sources 42 16 5.9 64 140,000

Interim 2016 policy case projections (tons)

EGU**4.8 1.6 0.36 6.8 8,800

NonEGU Point 17 7.9 4.4 29 38,000

Nonpoint 3.1 1.06 0.65 4.8 29,000

Mobile 0.79 0.29 0.13 1.2

All sources 26 11 5.6 42 75,000

Final 2016 base case projections (tons)

EGU 21 6.8 0.78 29 74,000

NonEGU Point 17 7.9 4.4 29 41,000**

Nonpoint 3.1 1.06 0.65 4.8 29,000

Mobile 0.79 0.29 0.13 1.2

All sources 42 16 5.8 64 140,000

Final 2016 policy projections (tons)

EGU 4.7 1.4 0.26 6.4 6,600

NonEGU Point 17 7.9 4.4 29 41,000**

Nonpoint 3.1 1.06 0.65 4.8 29,000

Mobile 0.79 0.29 0.13 1.2

All sources 26 11 5.4 42 77,000
10

* For this table, the EGU Sector is defined as follows: (1) For all pollutants other than mercury (Hg): 2005 NEI v2 

point source EGUs mapped to the Integrated Planning Model (IPM) model using the National Electric Energy 

Database System (NEEDS) 2006 version 4.10 database. A few revisions were made to the 2005 NEI v2 annual 

emission estimates as discussed in the 2005-based, Version 4.1 platform document. (2) For Hg: 6/18/2010 version 

of the inventory used for the 2005 National Air Toxics Assessment (NATA) mapped to IPM using NEEDS version 

4.10. The NATA inventory is an update to the 2005 NEI v2 and was divided into EGU and non-EGU sectors 

consistent with the other pollutants. We additionally removed Hg from sources from the NESHAP for Industrial, 

Commercial, and Institutional Boilers and Process Heaters (aka “Boiler MACT”) Information Collection Request 

(ICR) database because we included these emissions in the non-EGU sector. For more information, see the 2005-

based Platform Documentation, version 4.1.

** EGU Sector for 2016 is consistent with the 2005 base case discussed above. The future year emissions were 

generated by the Interim version of IPM4.10 and adjustments were made to remove Hg associated with the Boiler 

MACT ICR (which is accounted for in the Non-EGU sector), and to apply the impact of the final Boiler MACT for 

the other pollutants. For more information, see the Technical Support Document for the Proposed Toxics Rule, 

Emissions Inventories.

***NonEGU Point for the Final base and policy case projections are computed as 37,549 plus emissions for units 

< 25 megawatts

To summarize that table for EGUs only, Table 7 lists only the EGU emissions totals for the various 

cases. It also includes the average percent of divalent gaseous and particulate Hg for the EGUs in each case. 

As can be seen the divalent gaseous Hg ranges from 20% to 40% of the total Hg and the average particulate 

Hg ranges from 2 to 5% of total. 

Table7: EGU emissions of Hg and HCl for emissions cases.

Hg(0)

(tons)

Hg(2+)

(tons)

Hg(p)

(tons)

Total Hg 

(tons)

Hydrogen 

chloride 

(tons)

Hg(2+)

Percent of 

total Hg

Hg(p)

Percent of 

total Hg

2005 Base Case 

Emissions 30 21 1.6 53 350,000 40% 3%

2010 ICR Emissions N/A* N/A N/A 29 106,000

Interim 2016 base 

case projections 21.1 6.9 0.67 28.7 74,000 24% 2%

Interim 2016 Toxics 

Rule policy case 

projections

4.8 1.6 0.36 6.8 8,800 24% 5%

Final 2016 base case 

projections 21 6.8 0.78 29 74,400 23% 3%

Final 2016 Toxics 

Rule policy case 

projections 

4.7 1.4 0.26 6.4 6,600 22% 4%

*

Speciation data were not collected for Hg in the 2010 ICR