American Forest & 

Paper Association 

Boiler MACT 

Information

February 2011 
Table of Contents 

Agenda 

Position Paper on Boiler MACT Regulations.......................................Tab 1 

Legal Arguments for Reasonable Boiler MACT Limits...........................Tab 1 

EPA’s “MACT” Standard for Industrial Boilers Must Be Based on the 

Performance of Real Boilers............................................................Tab 2 

Source By Source Approach............................................................Tab 2 

Additional Comments on Boiler MACT Pollutant by Pollutant Approach 

and Effects of Multiple Emissions Controls.........................................Tab 2 

HBCA Crosswalk..........................................................................Tab 3 

EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments..........Tab 3 

Tier I HBEL Lookup Tables.............................................................Tab 3 

Non-Hazardous Solid Materials Rule................................................Tab 4 

International Emission Limits for Industrial Boilers................................Tab 5 

Boiler MACT and Benefit Claims......................................................Tab 6 

Selected Quotes from Governors on Boiler MACT...............................Tab 7 

Senate Boiler MACT letter to 

The Honorable Lisa Jackson, EPA Administrator.................................Tab 7 

Association Boiler MACT letter to The Honorable Lisa Jackson, EPA 

Administrator................................................................................................Tab 8

2 of 106
TAB 1 

3 of 106
January 2011  Page 1 

Position Paper on Boiler MACT Regulations

Background: 

Although most boilers already are well controlled for key pollutants, EPA is in the process 

of reissuing the Boiler MACT1

 rules to require 99% of boilers to do much more. We 

anticipate that solid fuel-fired boilers (like those that burn coal) will be heavily impacted. 

But even boilers using relatively clean fuels like biomass, hydrogen, clean process gas or 

other gaseous fuels will be subject to ultra-low emission levels which will be extremely 

expensive to meet if they can be met at all. 

The Boiler MACT sets emission limits for hazardous air pollutants. On June 4th, EPA 

proposed new rules for industrial, commercial and institutional boilers using fossil fuels 

and biomass to address concerns raised about the original rule in recent court decisions. 

EPA is under a court order to finalize the Boiler MACT rules by February 21, 2011. 

The Boiler MACT rules would require installation of up to four different air pollution control 

devices that will conflict with other existing control requirements. Due to the methodology 

EPA is using, the Boiler MACT emission limits would be extremely stringent, often 

approaching levels that can barely be detected. 

During this current economic crisis, these rules would impose an unsustainable regulatory 

burden if finalized as proposed. The capital cost for all manufacturing could be $21 

billion, plus billions more in annual costs and no other country in the world as a set of 

standard as stringent jeopardizing our global competitiveness. A wide range of 

manufacturers and the jobs they sustain would be severely harmed, as well as 

municipalities, universities, hospitals, federal facilities and others. 

Possible Solutions At Hand: 

EPA can use newly submitted and existing data to revise its proposed rules to protect air 

quality and target investments strategically, preventing severe job losses and tens of 

billions of dollars in unnecessary regulatory costs. 

EPA should set standards based on what real-world sources actually can achieve. 

Instead, EPA is proposing a pollutant-by-pollutant approach based on the best performers 

for each of five separate pollutants. This results in a set of standards based on a 

 

1

 The “Boiler MACT” is a rulemaking under the Clean Air Act Amendments of 1990. The statute requires 

that EPA regulate hazardous air pollutants from emission sources, including boilers, using maximum 

achievable control technology (“MACT”). Boilers use various fuels at industrial, commercial and 

institutional facilities to generate steam, heat, and/or electricity to power manufacturing. In addition to 

Boiler MACT, EPA is finalizing three related rules: Boiler GACT (Generally Achievable Control 

Technology for boilers at smaller sites); the Commercial and Industrial Solid Waste Incinerator (CISWI) 

rule (setting limits for non-hazardous solid waste incinerators); and the definition of Non-Hazardous 

Secondary Materials (a Resource Conservation Recovery Act rule determining which materials are 

wastes and thus covered under the CISWI rule when burned). 

4 of 106
January 2011  Page 2 

hypothetical boiler that can somehow simultaneously achieve the greatest reductions for 

each separate pollutant. This is like mandating a best-performing car that simultaneously 

is the best in fuel efficiency, passenger capacity, acceleration, towing capacity and safety. 

Some facilities that have recently upgraded their boilers or built new ones with the latest 

technology do not meet the proposed standards. Under the statute, 12% of boilers 

should be able to meet the standards with little or no additional effort, but under the 

proposed rule, less than 1% can comply without further controls. The tremendous 

diversity of boiler types, fuels used, operating conditions and products made justify 

“source-based” floor setting. 

EPA should provide alternative health-based emissions limitations for qualifying 

low-level emissions. A practical, health oriented standard for threshold pollutants like 

hydrogen chloride and manganese would allow sources to demonstrate that their 

emissions of these compounds do not pose a public health concern. Section 112(d)(4) of 

the Clean Air Act expressly contemplates the use of such a standard, which can be 

implemented at each facility without compromising public health protection. EPA has 

argued that reductions of other pollutants not covered by the MACT program (“cobenefits”) justify not using this authority, but that is contrary to the law. EPA should not 

add unnecessary stringency to the rule in a misguided effort to control non-HAP 

emissions that are better regulated under other parts of the Clean Air Act. EPA should 

make the health threshold standard an integral part of its final rule. 

EPA should expand the use of work practice standards to all gas-fired boilers. EPA 

appropriately used its authority under 112(h) to set work practices for natural gas fired 

boilers. These units are very clean burning, indeed they are so low that the emissions are 

extremely difficult and uneconomical to measure. It is critical to both preserve the 

proposed work practice and to expand the universe of gas fired boilers covered by work 

practices to other clean burning gases. EPA could avoid the increase in emissions (e.g., 

NOx and CO2) and energy use that would result from the numerous control technologies 

required with no guarantee of actually achieving the emission limits. 

In the related rule defining “Non-Hazardous Secondary Materials,” EPA should 

reaffirm that many secondary materials including biomass residuals are fuels and 

not wastes. The statute and related case law allow EPA to classify these materials as 

fuels if they are not discarded, are treated as valuable commodities, and are burned for 

energy recovery. Failure to encourage these alternative and often renewable fuels will 

result in more materials being landfilled and increase use of fossil fuels. 

EPA should use representative data in setting the standards and should factor into 

the MACT the variability in operations, fuels, designs and testing performance 

across the many types of boilers. There is insufficient latitude for variability among the 

extremely diverse universe of units and fuels used. Boilers burning significant amounts of 

biomass with coal and other solid fuels are inappropriately treated as coal boilers for 

pollutants that are combustion by-products. EPA has a large amount of data from recent 

testing and data requests as well as that submitted during the comment period to 

supplement its record of the last 15 years. They should examine these data using 

different analytical methods to derive defensible limits that are achievable in actual 

5 of 106
January 2011  Page 3 

operation for both existing and new units. To do otherwise leaves many companies in a 

position where the only way they can comply with the regulation is to stop operating. 

EPA should base the standards on the emissions of the best performing 12% of 

sources, rather than the “best of the best.” In its Phase II emissions testing program, 

EPA targeted only those sources that were the best performers. Then when EPA went to 

select the top 12% for setting the MACT floors, it assumed that this data set was 

representative of the full range of operations. In other words, EPA cherry picked the data 

and based the standards on the “best of the best” rather than the 12% best performing 

sources in the entire source category. The result is arbitrary because it is based on a 

skewed data set that by design is not representative of the full range of sources in the 

source category. Proposed emission limits are close to the detection limit of test methods

and far beyond what normal best performing units can achieve. In fact, pollution control 

vendors and manufacturers of new boilers are questioning whether the limits are 

achievable. Thus, EPA is setting the stage for an over-reaching regulation that is legally 

vulnerable for ignoring the practical capabilities of combustion units and controls. 

In the related “Boiler GACT” rule for smaller boilers, EPA should set work 

practices, not emissions limits, for area source biomass, coal and oil boilers. EPA 

has the discretion either not to regulate CO emissions from biomass and oil fired boilers 

at smaller facilities OR to choose to set a work practice standard based on section 

112(d)(5). The database EPA relies on for the GACT standards is so poor that the limits 

end up being even more stringent than those for major sources. In addition, EPA has not 

shown that emissions of polycyclic organic matter (POM)2 from biomass or oil combustion 

is part of the 90% of sources identified in the urban air toxics program as needing 

reductions. 

Summary: 

1. EPA should set limits based on the overall performance of actual sources, not on a 

hypothetical boiler that does not exist in the real world. 

2. EPA should include a health threshold standard in the final Boiler MACT rule to 

target environmental investments where there is a real need. 

3. EPA should finalize work practice standards for natural gas and refinery gas and 

expand their use to all gas-fired boilers and emission controls. 

4. EPA should narrowly define solid waste in the related rule on the definition of NonHazardous Secondary Materials. 

5. EPA should set standards that reflect the variability in the operations of true best 

performing boilers due to fuels, operations, designs and testing differences. 

6. EPA should base the standards on the best performing 12% of sources, rather 

than the “best of the best.” 

7. EPA should establish work practices for smaller biomass, coal and oil fired boilers 

in the related Boiler GACT rule. 

 

2

 CO is the surrogate for POM. 

6 of 106
Legal Arguments for Reasonable Boiler MACT Limits

A. The “pollutant by pollutant” approach to determining MACT is not 

appropriate because it results in standards that do not reflect the 

performance of the best performing boilers. 

• The proposed Boiler MACT standards are based on pollutant-by-pollutant 

analyses that rely on a different set of best performing sources for each separate 

HAP standard.1 In other words, EPA has “cherry picked” the best data in setting 

each standard, without regard for the sources from which the data come. 

• The statute unambiguously directs EPA to set standards based on the overall 

performance of sources. Sections 112(d)(1), (2), and (3) specify that emissions 

standards must be established based on the performance of “sources” in the 

category or subcategory and that EPA’s discretion in setting standards for such 

units is limited to distinguishing among classes, types, and sizes of sources. 

These provisions make clear that standards must be based on actual sources, 

and cannot be the product of pollutant-by-pollutant parsing that results in a set of 

composite standards that do not necessarily reflect the overall performance of 

any actual source. Congress provided express limits on EPA’s authority to parse 

units and sources for purposes of setting standards under § 112 and that express 

authority does not allow EPA to “distinguish” units and sources by individual 

pollutant as is proposed in this rule. Sierra Club v. EPA, 551 F.3d 1019, 1028 

(D.C. Cir. 2008). 

• EPA’s database shows that very few units (six) are best performers for all 

pollutants and thus it could not have reasonably concluded that the proposed 

standards reflect the performance of actual sources. 

B. EPA should establish health-based emissions limitations for acid 

gases and manganese under § 112(d)(4). 

• Section 112(d)(4) authorizes EPA to set health-based emissions limitations and 

is a powerful tool that enables EPA to match the stringency of a HAP emissions 

limitation to the level determined necessary to fully protect human health 

• In formulating § 112(d)(4), Congress recognized that, “For some pollutants a 

MACT emissions limitation may be far more stringent than is necessary to protect 

public health and the environment.” 2 As a result, § 112(d)(4) was provided as an 

alternative standard setting mechanism for HAPs “where health thresholds are 

well-established ... and the pollutant presents no risk of other adverse health 

effects, including cancer....”3

 

1 See, e.g., 75 Fed. Reg. 32019 (“For each pollutant, we calculated the MACT floor for a subcategory of 

sources by ranking all the available emissions data from units within the subcategory from lowest 

emissions to highest emissions, and then taking the numerical average of the test results from the best 

performing (lowest emitting) 12 percent of sources.”). 

2

 S. Rep. No. 101-228 (1990) at 171. 

3 Id. 

7 of 106
• EPA acknowledges its authority under § 112(d)(4) but proposes not to establish 

any health-based emissions limitations “[g]iven the limitations of the currently 

available information (i.e., the HAP mix where boilers are located, and the 

cumulative health impacts from co-located sources), the environmental effects of 

HCl, and the significant co-benefits of setting a conventional MACT standard for 

HCl.”4 

• Ample scientific information supports a determination that HCl, chlorine, 

hydrogen fluoride, hydrogen cyanide, and manganese are threshold pollutants, 

and thus, are eligible to be regulated under § 112(d)(4). In addition, the Agency 

has the technical tools and significant factual support for establishing healthbased emissions limitations for these HAPs that would provide the requisite 

ample margin of safety to health and the environment. 

• From a legal standpoint, the statute makes clear that criteria pollutant co-benefits 

associated with the proposed MACT standards may not be considered in 

deciding whether to establish § 112(d)(4) health-based emissions limitations. 

Also, EPA has failed to explain why the health-based emissions limitations it 

established in the 2004 Industrial Boiler MACT and the justification provided for 

those limitations should now be reversed. 

C. EPA inappropriately relies on emissions data from the “best of the 

best” in determining the existing source MACT floors. 

• The relative lack of data is a fundamental problem because EPA construes the 

statute as requiring it to set existing source MACT floors based on the top 

performing 12% of sources for which it has data for the larger source categories 

and subcategories. Less data means the pool from which the top 12% is drawn 

is smaller and, therefore, the actual number of sources used to determine the 

MACT floor is smaller. 

• The bulk of the information on which EPA’s relied in developing the proposed 

standards was collected by way of a § 114 information request that required 

testing of specified best performing units for specified pollutants. In this way, EPA 

artificially limited the pool of data from which it drew its top 12% best performing 

sources. The result is fatally arbitrary because EPA’s sampling approach for Phase 

II created a dataset that is not representative of sources for which the data is being 

used to infer emissions. 

• Instead of using emissions data from the “best of the best,” EPA should simply use 

emissions data from the “best” units in each subcategory. 

D. EPA must adopt a work practice standard for dioxins/furans. 

• The proposed dioxin/furan emission standards are so low and the detection limits 

of dioxin and furan isomers are so variable that many boilers are likely to exceed 

the proposed emission limits for dioxin/furans even though the tests show that all 

the isomers are present below the detection limits. Thus, imposing a dioxin/furan 

 

4

 75 Fed. Reg. at 32032. 

8 of 106
emissions limitation on industrial boilers would be arbitrary and capricious 

because the method of demonstrating compliance would not reliably distinguish 

compliant boilers from noncompliant boilers. 

• In this situation, EPA has ample authority to prescribe a work practice standard 

instead of a numeric emissions limit. Section 112(h)(2)(B) authorizes EPA to 

establish work practice standards when “the application of measurement 

methodology to a particular class of sources is not practicable due to 

technological and economic limitations.” 

• In any event, the § 112 HAP list includes only the named compounds 

dibenzofuran (CAS #132649) and 2,3,7,8 Tetrachlorodibenzo-p-dioxin (CAS 

#1746016). Therefore, if EPA decides to adopt numeric standards, the 

standards must be specific to these compounds. EPA has no authority to 

regulate under § 112 the generic chemical categories of “dioxins” and “furans.” 

E. The proposed rule fails to adequately account for variability in 

emissions that reasonably is expected from the top performing 

sources. 

• EPA has improperly developed a CO standard that boilers must meet at all times 

based on 3-run stack tests that fail to properly characterize the highly variable 

nature of CO emissions in solid fueled boilers. EPA has used only 3-run stack 

test data, which represents only a small and unrepresentative snapshot in time 

captured during the best operating conditions, to set emission limits for a 

pollutant that is highly variable. 

• EPA makes a similar mistake with regard to its proposal not to set a separate 

standard for periods of startup, shutdown, and malfunction. The emissions data 

on which the standards are based do not, in fact, reflect or adequately 

accommodate emissions from periods of startup, shutdown, or malfunction. 

• EPA proposes to use the 99 percent upper predictive limit (“UPL”) to 

accommodate and reflect variability in the operation of the best performers in 

calculating the MACT floor. The use of the 99 percent UPL calculated on only a 

small number of sources in a subcategory does not adequately capture variability 

or serve to predict the MACT floor level achievable by the top performers. 

• Instead of using the UPL, EPA should use the upper tolerance limit (“UTL”), 

which is meant for use in situations where the available data does not represent 

the entire population. In addition, since the proposed 99% confidence interval is 

applied to all 5 HAPs, the combined probability of achieving the set of limits 

drops to 95%, which is inappropriately low when facilities must be in compliance 

100% of the time. . 

F. The emissions database includes numerous fundamental flaws that 

compromise the MACT floor analysis that is based on these data. 

• EPA’s failure to provide adequate time for an appropriate assessment of the data 

violates the Agency’s obligation to provide a full and fair opportunity for public 

comment on the proposed rule. Within these severe time constraints, we 

9 of 106
conducted a spot check of approximately 100 stack test reports which revealed 

numerous data errors – many of which, if corrected, would have a material 

impact on the stringency of EPA’s calculated MACT floors and associated 

proposed standards. 

10 of 106
Boiler GACT Legal Arguments

A. EPA Has Not Justified The Need To Regulate Area Source Industrial 

Boilers In Order To Satisfy § 112(c)(6). 

• EPA’s MACT proposal for the § 112(c)(6) pollutants is flawed because the 

Agency provides no basis for its assertion that mercury (Hg) and polycyclic 

organic matter (POM) must be regulated under this standard in order to satisfy 

the requirement that 90% of nationwide emissions of these pollutants must be 

regulated under § 112 standards. In 1998, when EPA published the list of source 

categories that must be regulated to meet the § 112(c)(6) 90% control 

requirement, the Agency did not draw firm conclusions as to whether any area 

source categories needed to be regulated. 

• Moreover, § 112(c)(6) does not obligate EPA to regulate in order to provide “an 

anticipated margin to ensure that the obligations under CAA section 112(c)(6) are 

met.” EPA has either exceeded the 90% standard or not. When the facts show 

that the 90% standard is met, EPA has satisfied its § 112(c)(6) obligation. 

• When the facts are not sufficient for EPA to reliably draw conclusions, EPA’s 

obligation is to seek the additional information necessary to determine whether 

additional regulations are needed to meet the 90% standard. EPA’s obligation to 

provide record support for its regulatory decisions is turned on its head by the 

assertion that the lack of facts or uncertainty as to the available information 

justifies additional regulation under § 112(c) (6). 

B. Even If EPA Needed To Regulate Area Source Industrial Boilers To Meet 

§ 112(c)(6), It Would Not Be Required To Adopt MACT Standards. 

• CAA § 112(d)(5) authorizes EPA in most cases to set standards for area sources 

using “generally available control technologies or management practices” (i.e., 

“GACT”) rather than “MACT.” Section 112(d)(5) provides, “With respect to 

categories and subcategories of area sources listed pursuant to [§ 112(c)], the 

Administrator may, in lieu of the authorities provided in [§ 112(d)] ... elect to 

promulgate standards or requirements applicable to sources in such categories 

or subcategories which provide for the use of generally available control 

technologies or management practices by such sources.” In other words, EPA 

may establish “GACT” standards for area sources rather than “MACT” standards 

under § 112(d). 

• EPA takes the position in the proposal that it cannot use GACT to regulate HAP 

emissions from area source categories that are subject to § 112(c)(6). This 

11 of 106
position ignores the language in § 112(d)(5) that defines the scope of the 

Agency’s authority to use GACT. Section 112(d)(5) expressly states that EPA is 

authorized to use GACT “[w]ith respect to categories and subcategories of area 

sources listed pursuant to [§ 112(c)].” 

• A fundamental problem with EPA’s position is that it ignores the language in § 

112(d)(5) authorizing EPA to use the GACT method “in lieu of” the § 112(d)(2) 

MACT procedure. EPA itself has observed that the term “in lieu of” is commonly 

understood to mean “in place thereof” and, thus, has previously correctly 

concluded that, “CAA section 112(d)(5) authorizes EPA to promulgate standards 

under CAA section 112(d)(5) that provide for the use of generally available 

control technologies or management practices (GACT), instead of issuing MACT 

standards pursuant to CAA section 112(d)(2) and (d)(3).”5

 

• In short, the statute plainly says that the requirement to set a standard under § 

112(d)(2) can be satisfied by using the alternative GACT procedure specified in § 

112(d)(5). As a result, setting GACT under § 112(d)(5) meets the §112(c)(6) 

requirement to regulate under § 112(d)(2). 

C. The GACT Standard For Area Source Industrial Boilers Should Consist 

Of Management Or Work Practices Rather Than Numeric Emissions 

Limitations. 

• In situations where the use of GACT is authorized (as it is here), § 112(d)(5) on 

its face authorizes EPA to establish “standards or requirements .... which provide 

for the use of generally available control technologies or management practices.” 

(Emphasis added). In other words, when setting standards based on GACT, 

EPA is expressly authorized to establish work practices instead of emissions 

limitations. 

• There is no need under the express terms of § 112(d)(5) for EPA to make a 

showing under § 112(h) in order to set management or work practice standards. 

This interpretation is supported by the legislative history of § 1126

 and is reflected 

in numerous existing GACT standards.7

 5

 73 Fed. Reg. 1916,1920-1921 (Jan. 10, 2008).

6 See, S. Rep. No. 101-228, 101st Cong. 1st sess. 171-172 (GACT is to encompass “methods, 

practices and techniques which are commercially available and appropriate for application by the sources 

in the category ....”). 

7 See, e.g., 72 Fed. Reg. 16636, 16639 et seq. (Apr. 4, 2007) (describing methods of determining 

GACT for 7 area source categories). 

12 of 106
TAB 2

13 of 106
Privileged and Confidential 

Attorney Work Product 

- 1 - 

EPA’s “MACT” Standard for Industrial Boilers Must 

Be Based on the Performance of Real Boilers 

EPA’s proposed “MACT” standard for industrial boilers would set extraordinarily stringent 

emissions limits – limits that are far stricter than needed to protect health and the environment. 

This rule will cost companies billions of dollars and will create a strong incentive for companies 

to shift their manufacturing operations and the jobs that go with them overseas. 

EPA has many choices as to how it sets the standard. The Agency has deliberately chosen to 

forego alternative approaches that would protect health and the environment at far less cost. 

EPA can and must change its course. 

How does the air toxics program work? The purpose of § 112 of the Clean Air Act is to 

eliminate undue risk from emissions of hazardous air pollutants. Congress intended to 

accomplish this goal through a carefully designed two step process. The first step – the so-called 

“MACT” standards – requires EPA to set emissions limits from a given category of sources (in 

this case industrial boilers) at the level no less stringent than what is already is being achieved by 

the better-controlled source or sources in the category. EPA may make the standard more 

stringent than this “floor” level, but must prove that the more stringent standard is justified. In 

short, EPA must figure out who is doing a good job of controlling HAPs and require all other 

similar sources to do the same or better. 

In the second step, which must be accomplished within 8 years after a MACT standard is set, 

EPA must determine whether there is unacceptable remaining risk to health or the environment. 

If such risk exists, EPA must strengthen the MACT standard to eliminate the undue risk. 

Industrial boilers emit several types of hazardous air pollutants (“HAPs”). Section 112 requires 

EPA to set emissions limits for each of them. Therefore, the industrial boiler MACT “standard” 

actually will be comprised of a collection of several separate emissions limits. 

What’s the biggest problem with EPA’s chosen method of setting this standard? Under 

EPA’s proposed method of setting the standard – the “pollutant-by-pollutant” approach – EPA 

identifies a different set of best-performing boilers for each of the pollutant-specific emissions 

limits. So, for example, boilers A, B, and C might be the best performing with regard to mercury 

emissions, while boilers D, E, and F are best performing for hydrogen chloride emissions. In 

other words, EPA “cherry picks” the best data in setting each standard, without regard for the 

fact that a different collection of boilers are the best performers for each pollutant. 

The result is a composite set of standards that, taken together, reflect the characteristics of 

hypothetical best performing boilers that simultaneously achieve the greatest reductions for all

HAPs. However, such standards fail to reflect the performance achieved by the actual best 

performing boilers. For industrial boilers, this “franken-plant” approach would cause the 

standards to be so stringent that they could not be achieved by many boilers – which stands in 

sharp contrast to the clear Congressional direction for EPA to set “maximum achievable control 

technology” standards. 

14 of 106
Privileged and Confidential 

Attorney Work Product 

- 2 - 

By analogy, the Clean Air Act requires EPA to determine the “most valuable player,” and set 

standards based on what that player actually accomplished on the field. Instead, EPA has 

constructed a hypothetical MVP comprised of Player A’s batting average, Player B’s fielding 

performance, and Player C’s impeccable pitching. However much we might like to see a single 

player with such talents, the reality is that the MVP will be pretty good at most skills, but not the 

best at all of them. The same is true of industrial boilers. 

What can and should EPA do to fix its flawed approach? EPA should set the industrial boiler 

MACT based on the overall performance of actual boilers, rather than creating a composite 

reflecting the performance of super-boilers that do not actually exist. Under an actual-boiler 

approach, EPA would identify the “MVP” boilers – i.e., those that are the best performing when 

considering all HAPs – and then set the individual HAP emissions limits based on the 

performance achieved by these boilers. This method guarantees that the collection of emissions 

limits that make up the MACT standard is based on the actual performance of real boilers. 

What does the Clean Air Act say? The CAA unambiguously directs EPA to set standards 

based on the overall performance of sources. Sections 112(d)(1), (2), and (3) specify that 

emissions standards must be established based on the performance of “sources” in the category 

or subcategory and that EPA’s discretion in setting standards for such units is limited to 

distinguishing among classes, types, and sizes of sources. These provisions make clear that 

standards must be based on actual sources, and cannot be the product of pollutant-by-pollutant 

parsing that results in a set of composite standards that do not necessarily reflect the overall 

performance of any actual source. Congress provided express limits on EPA’s authority to parse 

units and sources for purposes of setting standards under § 112 and that express authority does 

not allow EPA to “distinguish” units and sources by individual pollutant as is proposed in this 

rule. Sierra Club v. EPA, 551 F.3d 1019, 1028 (D.C. Cir. 2008). 

EPA mistakenly believes the CAA is not so clear. Not surprisingly, EPA asserts that “section 

112(d)(3) does not mandate a total facility approach” and that “[a] reasonable interpretation of 

section 112(d)(3) is that MACT floors may be established on a HAP-by-HAP basis.” 75 Fed. 

Reg. 54970, 54998 (Sept. 9, 2010). But, even if § 112 were ambiguous (which it is not), EPA 

has improperly exercised its discretion in this rule. EPA has not shown or attempted to show that 

the proposed standards reflect the performance of any actual boilers and has not determined 

whether the suite of proposed emissions limitations is practicable. This failure to investigate a 

fundamental aspect of the proposed rule renders the rule arbitrary and capricious. EPA’s 

database shows that very few units are best performers for more than one pollutant, which clearly 

indicates that the proposed standards reflect the performance of exceedingly few actual boilers. 

Notably, EPA has expressed concern that the source-approach “likely yields least common 

denominator floors – that is floors reflecting mediocre or no control, rather than performance 

which is the average of what best performers have achieved.” 75 Fed. Reg. at 54999. But, this is 

a hypothetical concern that would not be realized for industrial boilers. Commenters on EPA’s 

proposed rule submitted analyses proving that the source-based approach produces stringent 

standards that would result in steep reductions in HAP emissions from industrial boilers. 

15 of 106
Source by Source Approach 

for Boiler MACT

November 30, 2010

16 of 106
Source by Source Approach

• Current MACT floors are set based on pollutant 

by pollutant approach, resulting in a different set 

of top performing boilers for each pollutant.

• We looked at setting MACT limits using a source 

approach instead.

• Due to small number of boilers that had data for 

all 5 pollutants proposed to be regulated, we did 

an analysis instead for boilers that had data for 

the 3 “fuel based HAP.”

17 of 106
Methods

• ERG MACT Floor Memo Appendix C-2 was used to separate boilers 

that had data for Mercury, HCl and PM.

• The lowest test was used as presented in Appendix C-2 in order to 

have the same rankings as the EPA’s pollutant by pollutant 

approach.

• Each boiler was ranked by each pollutant (Mercury, HCl and PM) 

then an average ranking was taken.

• The Top 12% of this final average ranking was taken and used in 

source by source floor calculations.

• We then used all of the run by run data for these boilers to calculate 

a 99UPL for Mercury, HCl, and PM.

• Fuel Variability Factors followed the same guidelines as described in 

pages 7-9 and Appendices A-1a, A-1b, A-2a and A2b in ERG MACT 

Floor Memo.

18 of 106
Boiler Changes We Made

• WIGPGreenBay2818 B10 - Wastepaper Sludge-Fired Boiler 10 that 

is incorrectly categorized by EPA as liquid instead of biomass.

• GAGPSRMRiincon EU BO02 and WIGPGreenBay2818 B29 -

Fluidized Bed Boiler #9 that burn petcoke but had been incorrectly 

categorized as coke oven gas boilers

• LAShellChemicaGeismar Furnace F-S801is incorrectly categorized 

by EPA as Gas 2 instead of Liquid.

• We used test data as-is, so results subject to change based on QA 

of test data and any changes to results based on detection limit recalculation, etc.

19 of 106
Biomass Source by Source

• 57 boilers had test data for all 3 fuel based HAP.

• Top 12% is 7 boilers.

• Calculated fuel variability factors where data 

available.

• Top ranked boiler is OR Flakeboard Eugene, 

which burns primarily natural gas with 15-20% 

biomass, so this boiler is not representative. 

Used AR Potlatch Forest Warren boiler (100% 

biomass) instead for new source MACT.

20 of 106
Biomass Floor Units

FacilityID CombustorID _common 

Mercury 

Rank

HCl 

Rank

PM 

Rank

Summed 

Rank

ORFlakeboardEugene Boiler-2 2 16 3 21

MESDWarrenSomerset No2 Power Boiler 3 3 17 23

ARPotlatchForestWarren Wellons Boiler 24 1 4 29

GAGPMadisonPly 800 Wood Waste Boiler 23 4 5 32

MEBoralexStratton Boiler #1 13 6 14 33

FLUSSugarCorp Boiler No. 7 1 26 18 45

IDPotlatch PB-1 CE 31 2 12 45

21 of 106
Biomass Results

Biomass Boilers

Proposed 

MACT 

Limit

Source 

Approach 

UPL

Source Approach 

Limit With 

Variability

Proposed New 

Source MACT

Source-based 

New Source 

Limit

Mercury (Hg) 9.E-07 2.E-06 3.E-06 2.E-07 7.E-07

Hydrogen Chloride (HCl) 0.006 0.02 0.04 0.004 0.004

Particulate Matter 

(filterable) 0.02 0.05 0.008 0.050

22 of 106
Coal Source by Source Floor 

Boilers

• 202 total boilers with data available for all 

3 pollutants.

• 12% is 25 boilers.

• Existing and new limits have fuel variability 

info factored in.

23 of 106
FacilityID CombustorID _common Hg Rank HCl Rank PM Rank Summed Rank

IAArchersDanielsMidlandDesMoines Asea Boiler #1 2 7 1 10

VAUniversityofVirginia 7103-1-01R 18 9 4 31

WIGPGreenBay2818 B29 - Fluidized Bed Boiler #9 17 8 7 32

IARoquetteAmerica

Circulating Fluidized Bed Boiler 

(121) 3 2 35 40

TNEastman_NO_CBIDATA Boiler 30 36 4 19 59

INPurdueUniverisity Boiler 5 4 40 18 62

SCCogenSouth B001 - Main Boiler 6 3 55 64

AKDoyonUtilities_AK 4 15 34 17 66

MENewPage-Rumford Cogen#6 13 60 12 85

MENewPage-Rumford Cogen#7 14 61 13 88

IDAmalgamatedSugarCoTwinFalls S-B1 11 59 23 93

AKDoyonUtilities_AK 7 33 33 30 96

IDTASCONampa Babcock and Wilcox (B&W) #1 41 16 46 103

IAUofIowa EP7 Boiler 11 1 77 27 105

IDTASCONampa Babcock and Wilcox (B&W) #2 42 17 47 106

VASmurfitStoneWestpt PB08 37 11 61 109

WINewPageBiron B24 100 10 11 121

TNEastman_NO_CBIDATA Boiler 31 87 12 26 125

INTateLyleSagamore 31B1 24 48 56 128

INSABICInnovativePlastics 01-001 BW1 Boiler 49 66 14 129

INSABICInnovativePlastics 01-001 BW2 Boiler 50 67 15 132

PAPHGlatfelter PB5 51 74 8 133

OKGPMuskogeeMill B-3 25 83 34 142

IAMuscatinePowerandWater Unit 7 80 20 45 145

MIPharma&Upjohn1180 Boiler 3 73 23 49 145

24 of 106
Coal Source by Source Approach 

Results

Coal Boilers

Proposed 

MACT Limit

Source 

Approach 

UPL

Source 

Approach 

Limit With 

Variability

Proposed 

New 

Source 

MACT

Source 

New 

Source 

Limit

Mercury (Hg) 3E-06 6E-06 2E-05 2E-06 1E-06

Hydrogen Chloride 

(HCl) 0.02 0.06 0.09 6E-05 5E-04

Particulate Matter 

(filterable) 0.02 0.04 0.001 0.001

25 of 106
Liquid Source by Source Floor 

Boilers

• 13 boilers with data available for all 3 

pollutants, took top 5 boilers for floor 

calculations.

• After examining data for this floor, Mercury 

run by run data for TN Invista Chattanooga 

EU003 - Vaporizer#2 was not available in 

the database (ERG used fuel data instead 

of stack test data), so fuel data was used 

to calculate the Mercury limit. 

26 of 106
Liquid Source by Source

FacilityID CombustorID_common

Hg 

Rank

HCl 

Rank

PM 

Rank

Summed 

Rank

LAShellChemicaGeismar Furnace F-S801 5 1 1 7

SCMilliken-Dewey D30 6 2 4 12

MNGPDuluth EU33Boiler#3 1 7 6 14

TNInvistaChattanooga EU003-Vaporizer#2 12 3 5 20

MEFPLEnergyWyman Unit#5 2 6 12 20

27 of 106
Liquid Source by Source Approach 

Limits

Liquid Boilers Proposed MACT Limit Source Approach Limit

Proposed New 

Source MACT

Source-based 

Approach New 

Source MACT

Mercury (Hg) 4E-06 5E-06 3E-07 2E-07

Hydrogen Chloride (HCl) 9E-04 1E-03 4E-04 1E-04

Particulate Matter (filterable) 0.004 0.2 0.002 0.01

No fuel variability data available.

28 of 106
Gas 2 Source by Source Floor 

Boilers

Only 4 boilers with data available for all 3 pollutants, so all boilers were in floor. 

No fuel variability data available.

FacilityID CombustorID_common Hg Rank HCl Rank PM Rank Sum

INTateLyleSagamore 21B501 2 1 2 5

SCBMWManufacturingCo HB03 1 4 1 6

MDSeverstalSparrows 1BLR(No.1Boiler) 3 2 3 8

WVMountainStateCarbonFollansbee S1 4 3 4 11

29 of 106
Gas 2 Source by Source Approach 

Limits

Gas 2 Boilers

Proposed MACT 

Limit Source Approach Limit

Proposed New Source 

MACT

Source-based 

Approach New Source 

MACT

Mercury (Hg) 2E-07 7E-06 2E-07 3E-07

Hydrogen Chloride (HCl) 3E-06 0.003 3E-06 4E-04

Particulate Matter (filterable) 0.05 0.01 0.003 0.005

30 of 106
Additional Comments on Boiler MACT Pollutant by Pollutant Approach 

and Effects of Multiple Emissions Controls 

The proposed MACT standards for industrial boilers and process heaters are based on 

pollutant-by-pollutant analyses that rely on a different set of best performing sources for 

each separate HAP standard. The result is a set of standards that reflect the performance 

of a hypothetical set of non-existent best performing sources that simultaneously achieve 

the greatest emission reductions for each HAP or surrogate rather than the actual 

performance of one or more real sources with a specific set of emissions controls. The 

purpose of this review is to evaluate if the limits being considered for Boiler MACT 

would, in some cases, necessitate installation of combinations of emission controls that 

may have adverse effects on each other. In other words, the presence of one control 

technology could prevent a second control technology from operating at optimum 

performance. In many cases, the installation of additional controls will also result in 

increased emissions of criteria pollutants and greenhouse gases (GHG). 

The table below summarizes the control interactions discussed in this document. 

Control Device Interactions and Concerns with Additional Controls 

CO Catalyst following 

other control devices for 

reducing CO and organic 

HAPs 

• For solid fuels, the CO catalyst must be placed after other 

controls removing particulate and sulfur to avoid poisoning 

catalyst and converting sulfur dioxide to SO3. Since higher 

temperatures are necessary to control HAPs than CO, this will 

likely require reheating of flue gas using additional fossil fuel in 

order to achieve the proper catalyst operating temperature, 

resulting in additional emissions of criteria pollutants and GHG. 

• Use of a catalyst will result in conversion of NO to NO2, which 

will adversely affect compliance with NO2 NAAQS. 

Sorbent injection to 

control HCl in boilers 

equipped with dry ESPs 

Presence of SO3 in flue gas improves PM collection efficiency of 

ESPs by lowering ash resistivity and also improves dioxin capture. 

If sorbent injection is used prior to the ESP for acid gas control to 

achieve Boiler MACT HCl limits, the sorbent will also capture SO3

and result in higher PM and dioxin emissions. 

CO catalyst followed by 

carbon injection 

CO Catalyst will oxidize fuel sulfur to SO3, which inhibits the ability 

of activated carbon to adsorb mercury. 

CO versus NOx control Reducing NOx emissions will result in higher CO emissions, 

reducing CO emissions will result in higher NOx emissions. 

Retrofit installation of 

multiple control devices 

• Adding multiple control devices to a boiler will increase the 

pressure drop through the system and require additional 

electricity to run the system, resulting in reduced boiler efficiency 

and additional emissions of criteria pollutants and GHG. 

• Retrofit installation of multiple controls could enhance the 

conditions that favor formation of dioxin. 

Sorbent injection prior to 

PM control device 

• Injection of sorbent to control HAPs prior to a PM control device 

will increase PM emissions over baseline. 

• Flyash may no longer be eligible for re-use and may have to be 

landfilled. 

31 of 106
1. CO Catalyst operation vs. NO2 and GHG emissions 

CO oxidation catalysts are likely to be deactivated by certain metals that are present in 

the flue gas produced from the combustion of solid fuels. These metals may poison the 

catalyst or mask the active sites on the catalyst material, rendering them ineffective. In 

addition, oxidation catalysts are very efficient at converting SO2 to SO3, which would 

have a detrimental effect on downstream heat recovery surfaces, and could produce a 

visible sulfuric acid plume. Therefore, the oxidation catalyst would have to be placed 

downstream of the particulate controls and SO2/acid gasscrubbers. Note that emissions 

of NO will also be oxidized to NO2, which may adversely affect a source’s compliance 

with the NO2 NAAQS. 

The flue gas temperature leaving particulate and acid gas control devices is typically well 

below the minimum effective operating temperature of the oxidation catalyst. While CO 

catalysts are effective at oxidizing CO at temperatures of 450-750°F, experience has 

shown that they need to be operated at much higher operating temperatures to actually 

achieve volatile HAP control (600-750°F). In order to reduce HAPs and CO, it would 

therefore be necessary to install a duct burner to reheat the flue gas by several hundred 

degrees to the necessary temperature. The additional fossil fuel that would be consumed 

by the duct burner would produce a dramatic decrease in the overall boiler efficiency. 

The duct burner would also produce increased emissions of GHG and criteria pollutants 

such as NOx, SO2, and particulate. 

2. Acid Gas Removal vs. Particulate and Dioxin Control 

The presence of SO3 in flue gas has been shown to significantly improve the collection 

efficiency of electrostatic precipitators (ESP) by lowering the resistivity of the fly ash. 

Since most of the chlorinated dioxins are attached to the particulate matter, the dioxin 

capture in the ESP would also be enhanced by the presence of SO3. However, a likely 

strategy for controlling HCl emissions (also required by Boiler MACT) is to inject 

sorbent to achieve acid gas control. These sorbents would also remove SO3 from the flue 

gas, which results in higher resistivity of the fly ash, and reduced ESP collection 

efficiency. Therefore, sorbent injection for HCl control could negatively impact the 

effectiveness of dioxin controls for boilers burning sulfur-containing fuels. 

3. Effect of Fuel Sulfur and Chloride on Mercury and HCl Emissions Control 

Fuels with high sulfur or chloride contents form oxidized forms of mercury which are 

more easily captured in particulate control devices and scrubbers. Boilers burning fuels 

with low sulfur and chloride contents emit higher fractions of mercury in its elemental 

form, which is harder to capture. When burning fuels containing mercury with fuels 

containing sulfur (e.g., biomass with TDF, oil, or coal), mercuric sulfate is formed, which 

is a particulate and can be captured in a fabric filter or electrostatic precipitator. 

However, when fuels such as biomass and natural gas with low mercury contents are 

burned without sulfur-containing fuels, elemental mercury is the primary emission and is 

not captured in a fabric filter. 

32 of 106
A primary control for Hg emissions involves the injection of activated carbon into the 

flue gas. The activated carbon oxidizes the mercury on the active sites on the carbon 

particles. The oxidized form of Hg can then either be recovered by the particulate control 

equipment, or by a scrubber (oxidized Hg is soluble). The oxidation reactions only occur 

at temperatures below about 350oF. 

The use of activated carbon injection for Hg control is negatively affected by the 

presence of sulfur trioxide (SO3). While the majority of the sulfur in fuel is converted to 

SO2, a small amount is converted to SO3. SO3 occupies the active sites on the carbon, 

taking away those sites from the Hg. Even a few parts per million of SO3 can have a 

significant negative impact on the Hg removal that is achieved by activated carbon 

injection. Additionally, other control devices, such as CO oxidation catalyst or SCR NOx

reduction catalyst, will convert an additional percentage of the SO2 to SO3, resulting in 

reduced Hg removal. 

There is a large body of research which has documented that during combustion there is a 

complex interaction between fuel chlorine, alkali metal, and sulfur content that 

determines the amount of hydrochloric acid that is finally produced. When fuels 

containing chlorine and alkali metals are burned, HCl and alkali chlorides are formed. 

During such combustion, the ratio of HCl and alkali chloride is determined primarily by 

the combustion temperature. Higher combustion temperatures generally cause lower HCl 

formation. However, when fuel sulfur is converted to SO2 during combustion, it reacts 

with alkali chloride to release HCl.  

Activated carbon injection is not as effective on units firing solid fuels with low levels of 

halogenated compounds. The solution on these units has been to inject a brominated 

compound with the carbon. Units equipped with scrubbers capture the resulting oxidized 

Hg and any excess bromine. Since the corrosivity of HBr is much greater than that of 

HCl, it is likely that HBr will create problems for the structural materials associated with 

the scrubber. 

4. Conflict of Lower CO vs. Higher NOx and other Pollutants 

The minimization of excess oxygen in boiler applications is a key feature for maximizing 

boiler efficiency. A boiler’s efficiency is affected by the amount of combustion air that is 

present, and the difference between the ambient temperature and the stack exhaust 

temperature. The more air that is heated up through the combustion process, the more 

heat is lost to the atmosphere, causing the boiler to be less efficient. A less efficient 

boiler will require more fuel to be fired to produce a given amount of steam, resulting in 

higher operating costs and higher GHG emissions. 

Minimizing the level of excess oxygen is a primary strategy for reducing NOx emissions 

from a boiler. The NOx formation mechanisms are dependent upon the temperatures in 

the flame zone, and the amount of nitrogen in the fuel. Reducing the level of excess 

oxygen reduces the adiabatic flame temperature, which reduces the rate at which the 

33 of 106
nitrogen in the combustion air and fuel forms NOx. Consequently, when low oxygen 

levels are maintained in the combustion air, less thermal NOx is produced. Similarly, if 

there is less oxygen present, nitrogen is less likely to be oxidized (and more likely to 

form diatomic nitrogen). This reduces both the amount of thermal NOx, and the fuel NOx

(NOx that is formed by the release of fuel-bound nitrogen). Therefore, increasing the 

level of excess oxygen to reduce the CO level will result in higher NOx emissions. 

Low NOx burner designs for gas-fired boiler applications manipulate the stoichiometry 

within the flame to minimize NOx formation. These designs establish a fuel-rich zone for 

the initial phase of combustion, and then add air at a later stage in the outer regions of the 

flame. In the initial phase, there is not sufficient oxygen available to form significant 

amounts of NOx, and in the secondary phase, the flame is much cooler, which also 

inhibits NOx formation. However, these burners often operate with CO emissions up to 

10 ppmvd in the upper part of the load range. At mid loads, the CO begins to increase 

near 50 ppmvd, and at low loads, it may exceed 100 ppmvd. These low-NOx burners will 

not be able to achieve CO emissions as low as 2 ppmvd. Drawbacks to the use of CO 

catalysts to achieve these ultra low CO levels were discussed above, and API has 

submitted extensive comments on why ultra low CO levels are not necessary to achieve 

low HAP levels. 

Data reviewed by the National Council of Air and Stream Improvement for biomass 

boilers indicates that boilers with higher carbon content in their fly ash will achieve some 

mercury and acid gas control. Operation of boilers under conditions meant to minimize 

CO will reduce the carbon content of the fly ash and reduce the inherent minimization of 

mercury and HCl. 

5. Loss of Boiler Efficiency due to Installation of Emissions Controls, and 

Implications for PSD and GHG Increases 

Boiler efficiency may be defined in a number of ways, but it is essentially the net amount 

of energy that may be extracted from the process, as a fraction of the gross energy input. 

There are a number of ways in which emission controls produce a negative impact on 

boiler efficiency. The most common of these is the increased backpressure created by the 

addition of control technologies that lie in the path of the flue gas. These include catalyst 

beds (e.g., for CO or NOx control), and baghouses (for particulate control). To overcome 

the increased backpressure, the combustion air fan requires more power to deliver the 

same amount of air. Thus, more energy is required to produce the same amount of steam, 

resulting in higher fuel consumption, and increases in emissions of GHG and other 

combustion-related pollutants. 

Similarly, pollutant controls for acid gas, mercury, or dioxins involve the injection of 

chemicals into the flue gas stream. The injection equipment consumes electricity that 

reduces efficiency. Some of these technologies require injection of a wet sorbent, for 

which water is the carrier fluid. The water vaporizes, and in doing so acts as a heat sink, 

and decreases the boiler efficiency. As a result, more energy is required to produce the 

34 of 106
same amount of steam, again resulting in higher fuel consumption and increases in 

emissions of GHG and other combustion-related pollutants. 

As stated previously, CO oxidation catalysts require a specific temperature window to 

operate effectively. Due to space and operational concerns, many boilers would have to 

install oxidation catalyst downstream of their existing pollution control equipment. In 

these cases, a duct burner will be required to reheat the flue gas. The additional fuel used 

would increase emissions of GHG, and other combustion-related PSD pollutants. 

The use of activated carbon for Hg removal may be problematic for boilers equipped with 

an ESP. The presence of SO3 is often critical to the successful operation of an ESP. 

Therefore, adding chemicals to remove the SO3 in the flue gas will result in less 

particulate control for the ESP. The increased carbon in the particulate has also been 

shown to alter the resistivity of the fly ash, causing arcing in the ESP, and reducing the 

overall control efficiency. If the boiler is equipped with a hot-side ESP for particulate 

control, carbon injection may not successfully remove Hg because the flue gas 

temperature in the ESP is too high for Hg oxidation to have occurred (>350oF). 

Injection of activated carbon for Hg control has a number of ancillary adverse 

environmental impacts. The increased amount of carbon in the fly ash causes it to be 

unsuitable for use in other applications (e.g., cement), so a facility that has an activated 

carbon injection system for Hg control will be required to send its fly ash to a landfill. 

The carbon that is injected into the flue gas also represents and increase in the inlet 

loading to the particulate control device. It may be necessary to install additional 

particulate control equipment (such as a fabric filter) downstream of the existing 

particulate control device to adequately control emissions. Therefore, a unit that met the 

MACT PM emission limit could still have to install additional PM control equipment to 

offset the effect of the Hg control strategy. 

In addition, as more emission controls are added, they tend to increase the backpressure 

of moving the flue gas through the system, and out the stack. The increased backpressure 

results in less gas volume flow for a given fan capacity. Boilers that add multiple 

emission controls will either have to accept a reduction in the rated steam production 

capacity, or will have to increase their fuel usage and possibly fan capacity to produce the 

same amount of steam, further reducing their efficiency. 

Many boilers are located in boilerhouses that have little available space for additional 

controls. Retrofit of new controls on these boilers may require major structural changes 

to the buildings in which they are located. In many cases, the flue gas leaving the boiler 

must be diverted to a piece of control equipment located to one side (or even at 

elevation), and then ducted back to the original flue gas path. The additional ducting 

further increases the backpressure on the boiler. 

Chlorinated dioxins are formed in boilers as a result of reactions between 

chlorine/chlorinated compounds and products of incomplete combustion in a temperature 

range from 750oF down to 400oF. One strategy for controlling dioxin emissions is to 

35 of 106
minimize the time that the flue gas occupies this temperature window. Adding additional 

control devices may lengthen the amount of time gases spend in this temperature window 

and increase the opportunity for dioxin formation. In addition, retrofit of pollution 

controls could adversely affect the flow patterns in the duct, and the resulting poor 

mixing of the combustion gases could also contribute to dioxin formation. 

36 of 106
TAB 3 

37 of 106
Page 1 of 5

HBCA Crosswalk

The numbered questions are the Specific Requests for Comments/Data questions from the “HBCA

Comments Requested 5‐10” document.

The bulleted responses (blue font) are from the “AFPA Boiler MACT Comments 08‐23‐10” document,

with page numbers included for reference.

1) Peak short‐term emissions of HCl from boilers – Note: comment/data is not specifically requested,

but this is a point raised in the p. 132 lead‐in, associated with EPA concerns about acute exposure

• Peak short term emissions can be estimated using the maximum hourly fuel use and either a

95th percentile of stack test or fuel analysis data.     [pg. 169]

• HCl is typically an acute exposure concern, but the chronic RfC is typically the limiting factor in

exposure assessments.               [pg. 154]

• Once acid gases are emitted from a stack, they have a short life in the atmosphere, due to high

solubility and reactivity and concentrations decrease rapidly with distance from the source.

           [pg. 149]

2) Facility‐specific information:  emissions, plant configurations, and fence‐line characteristics.  Needed

to enable EPA to develop model plants for the 11 subcategories, in order to conduct dispersion

modeling

• A health protective HBEL under CAA 112(d)(4) could take a number of forms. For example, a

tiered approach could be developed where a conservative look‐up table provides HCl equivalent

emission rate thresholds for various source‐receptor combinations. If the look‐up table is not

viable, then site‐specific modeling following established U.S. EPA risk assessment guidance could

be performed to establish an appropriate HBEL. For example, detailed dispersion modeling using

source specific stack parameters, distance to fenceline, and receptor locations could be used to

establish appropriate HBELs.                             [pg. 149]

• Example lookup tables are provided in Appendix H.    

3) Whether appropriate to establish health‐based thresholds for all acid gases, or for one acid gas as a

surrogate

3⁄4If for all acid gases:  for each, EPA would need to be able to conclude there is a health threshold, no

scientific evidence of carcinogenicity, and emission standard uses best available science to consider

possibility of toxicologic interactions with the other emitted gases

3⁄4If for one acid gas as a surrogate:  also define the mechanism proposed to determine the

appropriate surrogate

38 of 106
Page 2 of 5

3⁄4If for one acid gas as a surrogate:  must demonstrate, based on the knowledge of the effectiveness

of scrubbers for controlling each of the acid gases, that the surrogate emission standard ensures

that ambient levels of each of the other acid gases do not exceed their respective chronic health

thresholds

• HCl, other acid gases and some metal HAPs, such as Mn qualify as threshold pollutants.

Supporting evidence includes identification of a threshold dose below which adverse effects do

not occur, lack of evidence for carcinogenicity, and consideration of toxicological interactions

among acid gases and potential for additive effects. Demonstration of a common mode of

action amongst the various HAPs would support the notion of applying a single 112(d)(4)

standard for acid gases.                  [pg. 152]

• Both acute and chronic exposure to HCl, Cl2, and HF affect the respiratory system and the

pollutants cause respiratory irritation by similar mechanisms of action. However, the primary

chronic toxicity effect for HF (skeletal fluorosis) occurs at lower doses than the reported

respiratory effects.  Therefore, it is recommended that a combined acute HBEL for HCl, Cl2, and

HF and a combined chronic HBEL for HCl and Cl2 be established, but a separate chronic HBEL for

HF is recommended.                 [pg. 162]

• HCN has a completely different mechanism of action than HCl and HF.  Therefore, establishment

of a single acute HBEL for HCN is recommended.  Mn has a completely different mechanism of

action from HCN and affects a different target organ than HCl and HF, so establishment of a

separate chronic HBEL for Mn is indicated as well.         [pg. 162]

4) Whether there would be an additive affect if individual section 112(d)(4) standards are set for each

acid gas, and if so, how to simulate that affect.

• Because it is acknowledged that some of the HAPs subject to HBELs may have overlapping

health effects, the concept of the Target Organ Specific Hazard Index (TOSHI) following U.S. EPA

Guidance may be appropriate in some instances. The hazard index concept inherently assumes

that potential health effects due to simultaneous exposure are additive. This method was

applied in the 2004 Boiler MACT HBCA where the effects of Cl2 and HCl were assumed to be

additive by computing HCl toxic equivalent emissions.  Adding the health effects is appropriate

for the acute health effects of the primary HAP acid gases from solid fuel industrial boilers, HCl,

Cl2, and HF, and adding chronic effects of HCl and Cl2 is also appropriate...(i.e., an HCl acid gas

toxicity‐weighted short‐term emission rate can be defined as the emission rate of HCl + the

emission rate of Cl2 x Threshold of HCl /Threshold of Cl2 + the emission rate of HF x Threshold of

HCl /Threshold of HF).                                                                                                                                                                 

                                                                                                                                                                [pg. 163]

5) Comment on use of the hazard index (HI) approach, as described in EPA’s “Guideline for the health

risk assessment of chemical mixtures” and whether there are any other approaches to address such

additive effects.

• With the Target Organ Specific Hazard Index (TOSHI), the potential for health consequences for

various HAPs with similar types of health effects are assumed to be additive. Toxicological

studies for HCl and HF indicate that they have the same mode of action. Given that HCl and HF

concentrations are simultaneously present in flue gas, it may be appropriate to consider acute

39 of 106
Page 3 of 5

and chronic effects of these two HAPs collectively in evaluating peak short term (e.g., 1‐hour)

and long‐term (e.g., annual average) exposure concentrations. This concept could be readily

incorporated by computing a toxicity weighted emission rate of HCl that accounts for HCl and HF

emissions and their corresponding health effects benchmarks. We note that EPA’s suggestion in

the 2010 proposed rule that HF and HCN could materially contribute to health risk runs directly

counter to the statement that the agency made in the preamble to the 2004 Boiler MACT Final

Rule (69 FR 55244) when it stated that its research indicated that health risks from HF and HCN

emissions from boilers are considered to be insignificant.                                      [pg. 148]

6) Whether EPA should consider the affected sources (boilers) by themselves, or whether it should

consider all HAP emissions at the facility when developing a standard.  

• CAA Section 112(d)(f) does not express any intent that emissions from other types of sources at

a facility or background concentrations should be considered in a cumulative fashion with

emissions from permitted source. Evaluation of the acid gas impacts from all regulated boilers at

a facility will, in most cases, address virtually all of the irritant gas hazard. With the possible

exception of some types of chemical production and metallurgical facilities, nearly all of the

industrial emissions of HCl (and other acid gases) at industrial facilities are associated with

boilers. As such, computing an acid gas TOSHI associated with boiler emissions represents the

acid gas risk for the entire facility.             [pg. 149]

• The language of CAA Section 112(d)(4) indicates that only the potential threshold effects from

the MACT source should be considered.           [pg. 165]

7) How to consider the potential interactions of acid gases with other emitted respiratory irritants at

these types of locations.  Actual data requested, or, if no data is available, then comment on

whether such a demo could be made using a bounding calculation.

• The comments discuss cumulative exposure concerns for each compound.   As HCl, Cl2, and HF

affect the same acute target organ system and HCl and Cl2 affect the same chronic target organ

system, the effects of these compounds could potentially be additive.  Because HCN has a

different mode of action than HCl, Cl2, and HF, its effects would not be additive.  [pp. 152‐158]

8) Whether EPA should consider HAP emissions from neighboring facilities, and if so, what the

geographic scope of such consideration should be.  EPA notes consideration also could be based on

“average” or “high end” ambient levels of respiratory irritants seen in recent monitoring data or

modeled estimates, since site‐specific data might not be available on all respiratory irritants.

• Once acid gases are emitted from a stack, they have a short atmospheric half‐life due to high

solubility and reactivity, and as such, concentrations decrease rapidly with distance from a

source. Thus, it would be a very unusual circumstance if impacts from multiple facilities would

overlap in a cumulative layer cake fashion. This is confirmed by ambient measurement studies in

source‐rich urban areas, which have shown that HCl concentrations are very low, typically less

than 5% of the 20 μg/m3 Reference Concentration (RfC). In coastal areas, most of the airborne

HCl is attributable to the contribution of air‐sea interaction. Natural coastal deposition of HCl is

also reflected in data from EPA’s National Acid Deposition Network, which indicates that there is

no spatial correlation between deposition and major combustion sources.                        [pg. 148]

40 of 106
Page 4 of 5

• Even if this were applicable under CAA 112(d)(4), dispersion modeling shows that maximum

impact short‐term and annual average concentrations of non‐reactive pollutants associated with

boiler emissions generally occur within 1 km and fall off rapidly with distance.  This limits the

range at which appreciable concentrations of these gases are transported.  Because acid gases

are highly soluble, react with ammonia the ambient air, and are rapidly deposited through wet

and dry deposition, the range of ground‐level concentrations is much more limited than for non‐

reactive pollutants.  Therefore, unless there are boilers at an immediately adjacent facility, it is

highly unlikely that impacts would overlap to the extent that it would materially affect the HBEL.  

                     [pg. 166]

• There is no evidence that background concentrations of HCl are at appreciable levels from a

public health perspective.   A limited number of ambient measurement studies have shown that

ambient concentrations, even in highly urbanized areas, are very low.  A long‐term

measurement study of ambient acid gas concentrations in New York City (Bari et al 2003)

indicates an average of about 0.5 μg/m3

, which is only 2.5% of the chronic RfC (Reference

Concentration).  Thus, there is little basis for adjusting the HBEL to adjust for background

concentrations of acid HAP gases.  A study of HCl emissions and impacts from utility boilers

(Harkov 1999) concludes that, even in the vicinity of major sources of HCl, ambient

concentrations are very low.             [pp. 166‐167]

9) How to appropriately simulate all reasonable facility/exposure situations (e.g., using worst‐case

facility emissions coupled with worst‐case population proximity, average emissions and population,

or 90th percentile emissions and population).  Simulation could be based on sequential examination

of the facilities or could use screening or bounding methodologies.  Seeking comment on these and

other approaches.

• Realistic, yet conservative, HAP emission rate assumptions should be used in determining

compliance with HBELs under 112(d)(4) rather than across‐the‐board worst‐case assumptions

because using worst‐case emission assumptions will materially overestimate both chronic and

acute risk. Although care must be taken in estimating emissions, for the HAPs under

consideration, standardized methods could be established to develop suitably conservative

emission estimates based either on fuel data or emission tests.   A conservative analysis would

assume maximum emission rates of each pollutant occur simultaneously at worst‐case

dispersion conditions.                           [pp. 168‐169]

• As previously stated, we do not believe it is appropriate to consider sources other than the

facility’s boilers in the analysis.

10) Comments are sought on all conclusions in this section, which would include its final segment

discussing co‐benefits.

• EPA asserts that Congress acknowledged the possibility that MACT standards would result in

collateral non‐HAP emissions reductions and, therefore, that “the Agency may consider such

benefits as a factor in determining whether to exercise its discretion under section 112(d)(4).”

41 of 106
Page 5 of 5

Consideration of non‐HAP collateral emissions reductions is impermissible in setting MACT

standards. Section 112(d)(2) provides an express list of factors that EPA may consider in setting

§ 112(d) standards – including “the cost of achieving such emission reduction, and any non‐air

quality health and environmental impacts and energy requirements.” This list does not allow

consideration of non‐HAP air quality benefits, such as the co‐benefits of reducing PM2.5

emissions. This restriction is an unambiguous command that EPA should not consider non‐HAP

air quality benefits in setting standards under § 112(d). More fundamentally, the CAA clearly

distinguishes regulation of HAPs from criteria pollutants.  NAAQS are already in place for all

relevant criteria pollutants, so only HAPs should be considered under MACT.  In terms of

biomass, there are no associated SO2 reductions to claim.          [pp. 145‐147]

42 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 1 

I. Health-Based Emission Limits Should be Incorporated into the 

Rule 

A. Introduction 

In the Industrial Boiler MACT proposal, EPA acknowledges its authority under 

§ 112(d)(4) to establish a health-based emissions limitation (“HBEL”) for threshold 

pollutants in lieu of a MACT emissions limitation. However, the Agency proposes not to 

establish any HBEL “[g]iven the limitations of the currently available information (i.e., the 

HAP mix where boilers are located, and the cumulative health impacts from co-located 

sources), the environmental effects of HCl, and the significant co-benefits of setting a 

conventional MACT standard for HCl.” Draft at 140. Nevertheless, EPA asks for 

comment on a wide range of issues related to the justification for setting HBELs and the 

method by which they should be set. 

i. There are several compelling reasons for setting HBELs 

for HCl and manganese in the Industrial Boiler MACT. 

Section 112(d)(4) is a powerful tool that enables EPA to match the stringency of a HAP 

emissions limitation to the level determined necessary to fully protect human health. As 

a result, the standard is no more stringent and no less stringent than needed to get the 

job done. 

As EPA explains in the proposed rule, § 112(d) generally requires MACT emissions 

limitations to be set at a level that reflects the performance of the better performing 

sources in the given source category or subcategory. Section 112(d)(4) provides an 

alternative to this basic approach for pollutants for which a health threshold has been 

established. For such pollutants, § 112(d)(4) authorizes EPA to “consider such 

threshold levels, with an ample margin of safety, when establishing emission standards” 

under § 112(d). 

The default technology-based method of setting MACT standards is a cookie cutter 

approach that can and does result in HAP emissions limitations that go well beyond 

what is needed to protect the public from HAP emissions. The clear purpose of § 

112(d)(4) is to prevent this from happening. The legislative history of § 112(d)(4) is 

abundantly clear on this point. In formulating § 112(d)(4), Congress recognized that, 

“For some pollutants a MACT emissions limitation may be far more stringent than is 

necessary to protect public health and the environment.” 1 As a result, § 112(d)(4) was 

provided as an alternative standard setting mechanism for HAPs “where health 

 1

 S. Rep. No. 101-228 (1990) at 171. 

43 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 2 

thresholds are well-established ... and the pollutant presents no risk of other adverse 

health effects, including cancer....”2

When the first Industrial Boiler MACT was promulgated in 2004, it included healthbased emissions limitations for HCl and manganese. Under both of these standards, a 

site-specific risk assessment had to be conducted to prove that emissions from the site 

were low enough that human health would be protected, with an ample margin of safety. 

Actual emissions testing of all affected emissions points was required to verify the 

emissions rates used in the risk assessment. All relevant site parameters were required 

to be recorded in the site’s Title V operating permit to provide assurance over time that 

public health would be adequately protected.3

In short, these health-based emissions limitations were rigorous standards that 

demanded accountability. They were a winner for the Agency and the public because 

public health would have been protected with an ample margin of safety. At the same 

time these standards were a winner for affected sources because the standards would 

not have blindly required emissions to be reduced far below the levels needed to assure 

that the public was protected. It was estimated at the time that these health- based 

standards would have saved over $2 billion in compliance costs, as compared to the 

technology-based standards that otherwise would have applied. 

The first Industrial Boiler MACT was overturned by the D.C. Circuit, but on grounds 

unrelated to the health- based emissions limitations. Notably, in defending the healthbased emissions limitations, the Department of Justice concluded that, “Environmental 

Petitioners’ claim that the statute precludes EPA from establishing alternative standards 

for threshold pollutants (which petitioners mischaracterize as an exemption) is 

meritless.”4

Giving full consideration to the use of health-based standards is particularly important in 

the wake of the series of decisions from the D.C. Circuit that have progressively limited 

EPA’s discretion to make common-sense decisions when setting MACT standards 

under § 112. EPA’s authority to set health- based standards under § 112(d)(4) is 

unassailable. For appropriate HAPs and where the relevant facts substantiate its use, 

EPA can set health-based standards with full confidence that they will survive judicial 

review. 

 2 Id. 3 See, generally, 69 Fed. Reg. 55218, 55227-55228 (Sept. 13, 2004). 

4

 Final Brief For Respondent United States Environmental Protection Agency, D.C. Cir. Case No. 

04-1385 (Dec. 4, 2006) at 53-54. 

44 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 3 

ii. In light of the exceedingly stringent proposed MACT 

emissions limitations for HCl and metals (including 

manganese), it is arbitrary and capricious for EPA not to 

develop HBELs for these pollutants. 

While EPA has discretion in deciding whether to set HBELs under § 112(d)(4), the 

Agency cannot be arbitrary and capricious in making such a decision. The proposed 

HCl and PM emissions limitations for all types of industrial boilers are exceedingly 

stringent. Affected sources will have to spend tens of millions of dollars in order to meet 

the standards and, as even EPA predicts, a significant number of existing units simply 

will not be able to meet the standards and will be required to shut down. In addition, the 

work that EPA performed in support of the HBELs included in the 2004 rule 

demonstrates that the proposed standards are far more stringent than needed to assure 

the protection of public health with an ample margin of safety. The costs and burdens 

on affected sources and the degree of control needed to provide adequate health and 

environmental protection are both key factors that should be considered by the Agency 

in deciding whether to adopt HBELs in the Industrial Boiler MACT. 

In the proposed rule, EPA completely ignores these factors. The Agency’s discussion 

of HBELs includes no assessment whatsoever of the costs that might be avoided by 

adopting HBELs for HCl or manganese. As to potential effects on health or 

environment, EPA simply raises implementation questions and asserts a lack of 

information to resolve the questions. Such an approach is facially inadequate in light of 

the extensive policy, scientific, and technical assessment developed in support of the 

HBELs in the 2004 Industrial Boiler MACT standard. 

In short, EPA’s failure to fully consider key factors that are relevant to making an 

informed decision as to whether HBELs should be adopted is arbitrary and capricious. 

iii. EPA has failed to provide a rational basis for ignoring and 

contradicting the findings made in support of the HBELs 

included in the 2004 Industrial Boiler MACT rule. 

EPA asserts in the proposed rule that its decision not to propose HBELs “is not contrary 

to EPA’s prior decisions where we found it appropriate to exercise the discretion to 

invoke the authority in section 112(d)(4) for HCl, since the circumstances in this case 

differ from previous considerations.” Draft at 140. In contrast to “other source 

categories for which EPA has exercised its authority under section 112(d)(4),” EPA 

explains that boilers and process heaters are more likely to be co-located with other 

HAP sources and are often located in heavily populated urban areas where many other 

HAP sources exist. Id. at 140-141. The Agency concludes that, “These factors make 

45 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 4 

an analysis of the health impact of emissions from these sources on the exposed 

population significantly more complex than for many other source categories, and 

therefore make it more difficult to establish an ample margin of safety.” Id. at 141. 

These assertions are astonishing in that they fail to reflect the fact that the industrial 

boiler source category is one of the few categories where EPA has previously “found it 

appropriate to exercise the discretion to invoke the authority in section 112(d)(4).” As a 

result, EPA has already drawn conclusions as to how to deal with possible co-location 

with other HAP sources and how to appropriately consider HAP emissions from other 

nearby sources. These are not issues of first impression generally or in the specific 

context of industrial boilers and process heaters. The questions have been asked and 

answered in the context of notice and comment rulemaking for the industrial boiler and 

process heater source category. 

Thus, EPA is mistaken in asserting that its decision not to propose HBELs is “not 

contrary to EPA’s prior decisions.” The decision not to propose HBELs is flatly 

inconsistent with EPA’s prior determination that HBELs are appropriate and justified for 

the industrial boiler and process heater source category. EPA’s failure to acknowledge 

its prior determination and failure to explain why it has raised as questions issues that 

previously were resolved (such as how to consider co-located HAP sources and nearby 

HAP sources) render its decision not to propose HBELs arbitrary and capricious. 

iv. The co-benefits of collateral non-HAP emissions 

reductions cannot be used to justify a decision not to 

adopt HBELs. 

EPA explains in the proposal that “it considered the fact that setting conventional MACT 

standards for HCl as well as PM (as a surrogate for metals including manganese) would 

result in significant reductions in emissions of other pollutants, most notably SO2, noncondensable PM, and other non-HAP acid gases (e.g., hydrogen bromide) and would 

likely also result in additional reductions in emissions of mercury and other HAP metals 

(e.g., selenium).” Draft at 139. The Agency notes in particular that its belief that the 

rule will result in the reduction of up to 340,000 tons per year of SO2, which it 

characterizes as “substantial reductions with substantial health benefits.” Id. EPA 

asserts that Congress acknowledged the possibility that MACT standards would result 

in collateral non-HAP emissions reductions and, therefore, that “the Agency may 

consider such benefits as a factor in determining whether to exercise its discretion 

under section 112(d)(4).” Id. at 140. 

EPA is mistaken. Consideration of non-HAP collateral emissions reductions is 

impermissible in setting MACT standards. Section 112(d)(2) provides an express list of 

46 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 5 

factors that EPA may consider in setting § 112(d) standards – including “the cost of 

achieving such emission reduction, and any non-air quality health and environmental 

impacts and energy requirements.” This list does not allow consideration of non-HAP 

air quality benefits, such as the co-benefits of reducing PM2.5 emissions. This restriction 

is an unambiguous command that EPA should not consider non-HAP air quality benefits 

in setting standards under § 112(d). 

More fundamentally, the CAA clearly distinguishes regulation of HAPs from criteria 

pollutants. Section 112 “prohibits the addition of any criteria pollutant to ‘the list’ of 

HAPs, with a single exception for certain precursor pollutants not relevant to this case. 

This prohibition extends of necessity not only to rules that literally list a criteria pollutant 

as a HAP but also to any rule that in effect treats a criteria pollutant as a HAP.” National 

Lime Ass’n v. U.S. EPA, 233 F.3d 625, 638 (D.C. Cir. 2000). 

By basing its rejection of the health-based approach for Boiler MACT on the co-benefits 

of criteria pollutant reduction, EPA is “in effect” unlawfully treating a criteria pollutant as 

a HAP. EPA’s action here is not the simple use of a criteria pollutant as a surrogate for 

a HAP, which courts have upheld as long as EPA proves the scientific underpinning of 

the surrogate relationship. Id. Rather, EPA argues directly that it is the reduction in 

criteria pollutant emissions that causes it to reject the health-based approach. This 

EPA cannot do.5 

EPA’s sole support for its “collateral benefits” theory is legislative history -- the Senate 

Report that accompanied Senate Bill 1630 in 1989. But the D.C. Circuit rejected 

precisely the same argument in National Lime. In that case, EPA supported its 

argument regarding particulate matter as a surrogate for HAP metals by referring to the 

same Senate Report discussed above. The court rejected EPA’s argument, noting that 

the Senate Report referred to an earlier version of the statute that was ultimately not 

enacted, and hence was irrelevant: 

The final statute, by contrast, unqualifiedly prohibits listing a criteria 

pollutant as a HAP, that is, regardless of the reason. Because the 

comment in the Senate Report regarding PM and metals was made before 

the blanket prohibition upon regulating PM as a HAP was added to the 

statute, the report is irrelevant to our construction of 7412(b)(2) as 

enacted. 

 5

 Moreover, criteria pollutants from boilers are strictly regulated elsewhere under the Clean Air 

Act through New Source Performance Standards and other provisions of the Act. 

47 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 6 

National Lime at 638. Similarly here, EPA cannot use the language of a Senate Report 

that did not reflect the language of the statute as enacted to support its co-benefits 

theory and rejection of the health-based approach. 

Moreover, even if it were relevant, the language in the Senate Report cited by EPA 

appears to address only area-source GACT standards under Section 112(d)(5), and 

therefore is not relevant to interpretation of MACT standards under Section 112(d)(2) or 

the health- based alternative under Section 112(d)(4). And, in the final analysis, “it is 

the statute, and not the Committee Report, which is the authoritative expression of the 

law.” City of Chicago v. Env. Defense Fund, 511 U.S. 328, 337 (1994). Here, the 

statute clearly provides that MACT standards may address only HAPs, not criteria 

pollutants. See National Lime Ass’n at 638. 

But, even if it were not unambiguously prohibited, consideration of non-HAP air quality 

benefits under § 112(d)(4) would be unreasonable. National Ambient Air Quality 

Standards (“NAAQS”) are in place for all relevant pollutants, including ozone, SO2, and 

PM. A MACT standard is a very imprecise tool for helping to attain and maintain such 

NAAQS because it imposes across-the-board requirements in circumstances where 

tailored solutions are needed. Each area has its own unique mix of sources and it own 

particular needs in terms of what reductions are needed and where such reductions 

should be achieved. SIP-based air quality programs provide the needed flexibility to 

design a program that effectively addresses local air quality needs. MACT standards 

are an unreasonably blunt instrument for dealing with non-HAP air quality issues. 

Lastly, emissions of SO2 from unit burning biomass are very low when compared to 

other fuels. The AP-42 emission factor for wood combustion is 0.025 lb/mmBTU and 

AF&PA’s experience with biomass units is that SO2 emissions are routinely much lower 

than this emission factor. NCASI also has completed research (NCASI Technical 

Bulletin 640, Sulfur Capture in Combination Bark Boilers, and Special Report 09-02, 

Sulfur Capture in Combination Bark Boilers – An Update) that demonstrates that even 

when sulfur containing fuels are burned with biomass, a significant portion of sulfur is 

captured by the alkaline wood ash.6 Thus, even if EPA could consider co-benefits of 

non-HAP reductions in developing standards under § 112, the nominal co-benefits of 

reducing SO2 emissions from biomass units would not outweigh the other advantages of 

establishing a health- based emissions limitation for HCl. 

 6

 These 2 documents are available to NCASI members and can be made available to EPA staff 

upon request. 

48 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 7 

B. Technical Assessment 

The purpose of this provision of the CAA is to allow EPA to focus more stringent MACT 

controls on non-threshold HAPs (those that could pose some level of adverse health 

effects at any non-zero concentration) than HAPs with thresholds, for which the level of 

incremental concentration from a source could pose potential health consequences. By 

providing a special provision for threshold HAPs that likely pose little or no potential 

adverse health effects, the CAA allows EPA to consider limiting the burden on regulated 

sources with HAP emissions that pose little or no health hazard. Some of the HAPs 

targeted by the Boiler MACT, such as the acid gases, hydrogen chloride (HCl), chlorine 

(Cl2), hydrogen fluoride (HF) and hydrogen cyanide (HCN), as well as metals such as 

manganese (Mn) meet the requirements for classification as threshold pollutants. 

Therefore, if the associated incremental ambient concentrations of these threshold 

pollutants as a result of emissions from a regulated source are sufficiently low, they 

would qualify for alternative MACT provisions under 112(d)(4). 

Section 112(d)(4) does not specify how EPA should “consider threshold levels, with an 

ample margin of safety” in developing alternative MACT requirements. In the Pulp and 

Paper MACT and in the 2004 Boiler MACT, EPA maintained that that application of this 

CAA section is met if the incremental exposure concentration from subject MACT 

sources at a facility is less than established health effects thresholds. The “margin of 

safety” is built into the means by which: 

• Emissions and associated exposure concentrations are characterized; 

• Health effects thresholds are derived; and 

• Dispersion models estimate exposure. 

CAA Section 112(d)(4) does not apply to HAPs from other source categories at a facility 

or background concentrations, as the CAA explicitly directs EPA to address residual 

issues subsequent to the initial MACT setting process under CAA Section 112(f)(c). 

HCl typically comprises about 80% or more of acid gas emissions from boilers, with 

20% or less comprised of HF. In terms of developing Health-Based Emission Limits 

(HBEL), it is appropriate to consider EPA’s concept of Target Organ Specific Hazard 

Index (TOSHI), where the potential for health consequences for various HAPs with 

similar types of health effects are assumed to be additive. Toxicological studies for HCl 

and HF indicate that they have the same mode of action as irritant acid gases. Given 

that HCl and HF concentrations are simultaneously present in flue gas, it may be 

appropriate to consider acute and chronic effects of these two HAPs collectively in 

evaluating peak short term (e.g., 1-hour) and long-term (e.g., annual average) exposure 

concentrations. This concept could be readily incorporated by computing a toxicityweighted emission rate of HCl that accounts for HCl and HF emissions and their 

corresponding health effects benchmarks. 

We noted that EPA’s suggestion in the 2010 proposed rule that HF and HCN could 

materially contribute to health risk runs directly counter to the following statement that 

49 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 8 

the agency made in the preamble to the 2004 Boiler MACT Final Rule (69 FR 55244) 

when it stated that its research indicated that health risks from HF and HCN emissions 

from boilers are considered to be insignificant. 

“Facilities attempting to utilize the health-based compliance alternative for HCl will 

not be required to evaluate emissions of other inorganic HAP except for chlorine. We 

conducted an assessment of boiler emissions and determined that, of the acid gas 

HAP controlled by scrubbing technology, chlorine is responsible for the great 

majority of risk and HCl is responsible for the next largest portion of the total risk. 

The contributions of other HAP, including hydrogen fluoride, to the total risk were 

negligible. Therefore, facilities attempting to demonstrate eligibility for the healthbased compliance alternative for HCl, either by conducting a lookup table analysis or 

by conducting a site specific compliance demonstration, must include emission rates 

of chlorine and HCl from their boilers. We do not expect hydrogen cyanide emissions 

from boilers covered under the final rule.” 

If EPA has conducted new research that refutes this former finding, it is imperative that 

this research be brought to light. 

As noted, the language of CAA Section 112(d)(f) does not express any intent that 

emissions from other types of sources at a facility or background concentrations should 

be considered in a cumulative fashion with emissions from permitted source. 

Evaluation of the acid gas impacts from all regulated boilers at a facility will, in most 

cases, address virtually all of the irritant gas hazard. With the possible exception of 

some types of chemical production and metallurgical facilities, nearly all of the industrial 

emissions of HCl (and other acid gases) at industrial facilities are associated with 

boilers. As such, computing an acid gas TOSHI associated with boiler emissions only 

under CAA 112(d)(4) represents the acid gas risk for the entire facility. Once acid 

gases are emitted from a stack, they have a short atmospheric half-life due to high 

solubility and reactivity, and as such, concentrations decrease rapidly with distance from 

a source. Thus, it would be a very unusual circumstance if impacts from multiple 

facilities would overlap in a cumulative layer cake fashion. This is confirmed by ambient 

measurement studies in source-rich urban areas, which have shown that HCl 

concentrations are very low, typically less than 5% of the 20 μg/m3

 Reference 

Concentration (RfC). In coastal areas, most of the airborne HCl is attributable to the 

contribution of air-sea interaction. Natural coastal deposition of HCl is also reflected in 

data from EPA’s National Acid Deposition Network, which indicates that there is no 

spatial correlation between deposition and major combustion sources. 

A health protective HBEL under CAA 112(d)(4) could take a number of forms. For 

example, a tiered approach could be developed where a conservative look-up table 

provides HCl equivalent emission rate thresholds for various source-receptor 

combinations. If the look-up table is not viable, then site-specific modeling following 

established U.S. EPA risk assessment guidance could be performed to establish an 

50 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 9 

appropriate HBEL. For example, detailed dispersion modeling using source specific 

stack parameters and receptor locations could be used to establish appropriate HBELs. 

Variability in emissions could be addressed by consideration of variability in fuel 

consumption and fuel content. A robust statistical method could be applied to assure 

conservatism with a reasonable level of certainty, such as the 95th percentile commonly 

applied by EPA. Alternatively, limits for HCl and other pollutants established in air 

permits could be proposed for use in lieu of establishing separate HBELs. 

In the proposed rulemaking, EPA concluded that the information available at this time is 

insufficient to establish health-based emission standards for HCl or the other acid 

gases. In the 2004 Boiler MACT EPA concluded that HCl was a threshold pollutant for 

which CAA Section 112(d)(4) should be applied and there are many other historical 

precedents where EPA has considered HCl a threshold pollutant. Some of those 

precedents include: 1) National mission Standards for Hazardous Air Pollutants: Final 

Standards for Hazardous Air Pollutants for Hazardous Waste Combustors (Phase I 

Final Replacement Standards and Phase II); Final Rule; 2) National Emission 

Standards For Hazardous Air Pollutants; Proposed Standards For Hazardous Air 

Pollutants From Chemical Recovery Combustion Sources At Kraft, Soda, Sulfite, And 

Stand-Alone Semichemical Pulp Mills; 3) National Emission Standards for Hazardous 

Air Pollutants From the Portland Cement Manufacturing Industry; Proposed Rule; 4) 

National Emission Standards for Hazardous Air Pollutants: Chlorine and Hydrochloric 

Acid Emissions From Chlorine Production. 

Thus, the recent change in EPA’s position appears not to be based on changes in the 

underlying scientific evidence since 2004 but rather a shift in policy. In this proposed 

rulemaking, EPA interprets section 112(d)(4) to allow additional factors beyond any 

established health threshold, such as cumulative and ecological effects, to be weighed 

in making a judgment whether to set a standard for a specific pollutant based on the 

threshold. This interpretation of the CAA represents a significant and unexplained 

departure from previous MACT rulemakings and from EPA's prior decision to adopt 

health based emissions limitation in the 2004 industrial boiler MACT rule. The Agency 

has made a 180 degree turn that is not supported by the record and not scientifically 

justified. 

A. Basis for HBELs under CAA Section 112(d) in the Industrial 

Boiler MACT 

CAA 112(d) enables EPA to establish alternative MACT standards by applying 

provisions such as the HBEL to avoid unnecessary regulation for HAPs that do not pose 

a health risk. In 2004, EPA determined that two HAPs commonly emitted from solid fuel 

industrial boilers, hydrogen chloride (HCl) and manganese (Mn), are threshold 

pollutants that do not pose a significant health risk at a potentially large proportion of 

51 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 10 

regulated sources. If it can be demonstrated that health benchmarks are met for these 

HAPs, emission controls for these materials are not deemed to be necessary. 

Similar considerations for addressing HCl as a threshold pollutant have been included in 

1) National Emission Standards for Hazardous Air Pollutants: Final Standards for 

Hazardous Air Pollutants for Hazardous Waste Combustors (Phase I Final Replacement 

Standards and Phase II); Final Rule; 2) National Emission Standards For Hazardous Air 

Pollutants; Proposed Standards For Hazardous Air Pollutants From Chemical Recovery 

Combustion Sources At Kraft, Soda, Sulfite, And Stand-Alone Semichemical Pulp Mills; 

3) National Emission Standards for Hazardous Air Pollutants From the Portland Cement 

Manufacturing Industry; and 4) National Emission Standards for Hazardous Air 

Pollutants: Chlorine and Hydrochloric Acid Emissions From Chlorine Production. In the 

absence of specific scientific evidence to the contrary, it has historically been EPA’s 

policy to classify non-carcinogenic effects as threshold effects, as demonstrated in the 

above rulemakings. 

The logic provided by EPA in developing the 2004 HBCA was a direct interpretation of 

112(d)(4). In summary: 

• Hydrogen chloride is the chief acid gas HAP from solid fuel combustion and 

emissions are related to chloride and chlorine content in fuel. Hydrogen 

chloride and chlorine are threshold HAPs with associated similar effects and 

established Reference Concentrations (RfC), such that the combined 

inhalation risk of these HAPs can be considered collectively. 

• Manganese is a threshold HAP metal, which is a chief risk driver for woodfired boilers. The 2004 Boiler MACT included emission standards for Total 

Selected Metals (TSM), of which manganese was a component. The HBCA 

would exempt manganese from the TSM calculation. 

• 112(d)(4) was interpreted to require that all MACT boilers (i.e., from the same 

MACT source category) at a single facility not significantly contribute to risk. 

It does not require risk evaluation of other HAPs with different types of health 

effects or contribution from other sources or background concentrations, as 

presently suggested in the proposed rule. In 2004, EPA stated the basis for 

this determination in response to comments that cumulative risks should be 

evaluated under the HBCA. EPA responded that 112(d)(4) does not indicate 

that a risk assessment should be undertaken, but simply that the threshold 

level of a particular HAP should be considered and that it is appropriate to 

consider cumulative risk under 112(f), which requires the evaluation of 

residual risk after the implementation of MACT standards. Section 

112(f)(1)(c) states that EPA will address “actual health effects with respect 

to persons living in the vicinity of sources, any available epidemiological 

or other health studies, risks presented by background concentrations of 

hazardous air pollutants” in the residual risk assessments. 

52 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 11 

Rather than this direct interpretation of the CAA 112(d)(4) applied by EPA in 2004, the 

preamble to the 2010 proposed Boiler MACT repeatedly cites congressional intent, 

suggesting expanding the consideration of threshold level to other tangential issues 

such as MACT HAP controls also reducing criteria pollutant and ecological benefits of 

controls. Although such objectives may appear to be meritorious from an overall 

environmental protection perspective, there is no indication from the language of 

112(d)(4) that other factors besides human health effects of specific threshold HAPs are 

intended to be considered. 

B. Acid Gas HAPs (HCl, Cl2, HF, HCN) and Mn Qualify Threshold 

HAPs with Established Thresholds 

HCl, other acid gases and some metal HAPs, such as Mn qualify as threshold pollutants 

and, therefore, they should be considered under section 112(d)(4). Supporting 

evidence includes identification of a threshold dose below which adverse effects do not 

occur, lack of evidence for carcinogenicity and consideration of toxicological interactions 

among acid gases and potential for additive effects. In addition, demonstration of a 

common mode of action amongst the various HAPs would support the notion of 

applying a single 112(d)(4) standard for acid gases. 

Table 1 summarizes data on threshold doses for HCl, Cl2, hydrogen cyanide (HCN), HF, 

and Mn. Information supporting the existence of health effects thresholds for each HAP 

is provided below along with a discussion of whether the HAPs have similar modes of 

action. 

53 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 12 

1. Hydrogen Chloride (HCl) 

Critical Target Organ

The critical target organ for acute toxicity of HCl is the upper respiratory system (sore 

throat, nasal discharge), lower respiratory system (pulmonary function, cough, chest 

pain), and eyes. The target organ for chronic toxicity is also the respiratory system. 

Mechanism of Action 

On contact with moisture, HCl dissociates almost completely. The hydrogen ions 

combine with water to form hydronium ions (H3O+

), which can cleave organic molecules 

and cause cell death. Thus, the adverse effects associated with HCl exposure are due 

to direct contact irritation of tissues at the portal of entry and persistent cellular injury in 

the affected tissue. 

Evidence of Threshold

An acute threshold has been established. A chronic threshold has not been 

established. However, data on chronic toxicity of HCl are very limited and all studies 

located in the literature have used the Lowest Observed Adverse Effect Level (LOAEL) 

as the lowest dose in the dosing regimen. Therefore, the failure to identify a chronic 

54 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 13 

threshold is not an indication that no threshold exists, but rather an indication that data 

on chronic effects from HCl are very limited. HCl is typically an acute exposure concern 

but the chronic RfC is usually limiting in exposure assessments. However, controlling 

short-term peak exposures naturally has the dual benefit of also reducing long-term 

exposures. In addition to the general lack of toxicological studies suggesting that HCl 

could be a potential carcinogen (see below), the listing of health thresholds for HCl by 

the Environmental Protection Agency (EPA), Agency for Toxic Substance Disease 

Registry (ATSDR), California EPA, and the World Health Organization in the public 

domain has established that HCl is a threshold pollutant. 

 

Evidence of Carcinogenicity 

No pre-neoplastic or neoplastic nasal lesions were observed in a 128-week inhalation 

study with SD male rats at 10 ppm HCl gas. No evidence of treatment related 

carcinogenicity was observed in other animal studies performed by inhalation, oral or 

dermal administration. In humans, no association between HCl exposure and tumor 

incidence has been observed. 

Cumulative Exposure

There is little evidence that the general public is exposed routinely to measurable 

quantities of gaseous chlorine and/or HCl. Even the HCl produced during the 

combustion of fossil fuels or the incineration of solid waste apparently lasts too short a 

time in the un-reacted state to pose a significant health risk (IPCS, 1982). However, 

HCl does affect the same target organ system (respiratory system) as hydrogen fluoride 

(HF) and, therefore, it is possible that the effects of HCl and HF could be additive. 

2. Chlorine (Cl2) 

Critical Target Organ

The critical target organ for the acute toxicity of Cl2 is the upper respiratory system 

(transient respiratory irritation), lower respiratory system (slight alterations in pulmonary 

function tests), and the eyes. The target organ for chronic toxicity is also the respiratory 

system. 

Mechanism of Action

Cl2 is a strong oxidizer that hydrolyzes in water forming HCl and hypochlorous acid. Cl2

gas has been shown to be 33 times more potent as a sensory irritant in mice than HCl 

(Barrow et al. 1977), The assumption is that products of the reaction of Cl2 with water are 

able to interact with functional groups in components from cells in the respiratory 

epithelium. At low concentrations, only sensory receptors are affected, triggering only 

changes in respiratory dynamics, but higher concentrations produce frank tissue damage 

due to disruption of cellular components (ATSDR, 2007). 

55 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 14 

Evidence of Threshold

The effects of acute-exposure to Cl2 have been well characterized in humans and 

animals. Collectively, the results suggest that brief exposures to concentrations of Cl2 less 

than 0.5 ppm do not cause sensory irritation or significant alterations in pulmonary 

function tests, but exposure to 1 ppm or greater can induce transient respiratory and eye 

irritation and slight alterations in pulmonary function tests (Anglen 1981; D’Alessandro et 

al. 1996; Rotman et al. 1983; Schins et al. 2000; Shusterman et al. 1998, 2003). There is 

no information regarding chronic-duration exposure of the general population to chlorine 

because this type of exposure occurs only in occupational settings. There are few studies 

of chronically exposed workers that were not also subjected to acute episodes of high 

exposure or “gassing” incidents. However, a chronic threshold based on nasal lesions 

has been established in monkeys (Klonne et al. 1987). 

Evidence of Carcinogenicity 

No studies on the carcinogenic effects of Cl2 in humans and only a few animal studies 

were located in the literature. All of the animal carcinogenicity studies listed on the 

Chemical Carcinogenesis Research Information System were negative and no positive 

studies were listed on the Carcinogenic Potency Project at 

http://potency.berkeley.edu/chemicalsummary.html. Co-carcinogenic properties (i.e., 

some studies suggest that Cl2 can promote the carcinogenicity of other compounds) of 

Cl2 in animals have been examined, but the results are mixed, with one study resulting in 

cancer in a single mouse and another study causing a 40% decrease in the number of 

skin cancers in initiated mice. Study results on genotoxicity of Cl2 have also been mixed. 

Neither, the EPA, the International Agency for Research on Cancer (IARC), or the 

Department of Health and Human Services (DHHS) have classified Cl2 gas as to its 

carcinogenicity. Although EPA has not developed a formal evaluation of the potential for 

Cl2 carcinogenicity, the evaluation by the International Agency for Research on Cancer 

stated that there was inadequate evidence for carcinogenicity in humans or experimental 

animals and thus concluded that Cl2 is not classifiable as to its carcinogenicity to humans. 

Other rules (e.g., Final Standards for Hazardous Air Pollutants for Hazardous Waste 

Combustors (Phase I Final Replacement Standards and Phase II); Final Rule; 2) National 

Emission Standards For Hazardous Air Pollutants) have evaluated Cl2 only with regard to 

non-cancer effects. In the absence of specific scientific evidence to the contrary, it has 

been EPA’s policy to classify non-carcinogenic effects as threshold effects. 

Cumulative Exposure

56 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 15 

There is little evidence that the general public is exposed routinely to measurable 

quantities of gaseous Cl2. However, Cl2 does affect the same acute target organ 

system (respiratory system) as HCl and hydrogen fluoride (HF) and the same chronic 

target organ system (respiratory system) as HCl, Therefore, it is possible that the acute 

effects of Cl2, HCl and HF could be additive and the chronic effects of Cl2 and HCl could 

also potentially be additive. 

3. Hydrogen Cyanide (HCN) 

Critical Target Organ 

The Central Nervous System (CNS) is the target organ for the acute health effects 

associated with HCN. The critical target organ for the chronic health effects of HCN is 

also the CNS, but long-term exposure can also affect thyroid function (CalEPA, 2008b). 

Mechanism of Action 

The mode of action of HCN toxicity is cytochrome oxidase inhibition, which prevents 

cellular utilization of oxygen. The cyanide ion blocks oxidative respiration, causing 

failure of oxygen usage with tissue hypoxia leading to metabolic acidosis. 

Evidence of Threshold 

 An acute threshold has been established. A chronic threshold in humans has not been 

established. Data on chronic toxicity of HCN in humans (and animals) is very limited. 

However, a subacute inhalation NOAEL for HCN has been established in rabbits 

(CalEPA, 2008b). In addition to the lack of evidence that HCN is a potential carcinogen 

(see below), the listing of health thresholds for HCN by California EPA (CalEPA, 2008b) 

and many other organizations (e.g., Agency for Toxic Substance Registry [ATSDR], 

World Health Organization [WHO], National Institute of Public Health and the 

Environment, Bilthoven (The Netherlands), etc.) in the public domain has established 

HCN as a threshold pollutant. 

Evidence of Carcinogenicity

Out of 20 mutagenicity studies summarized on the Chemical Carcinogenesis Research 

Information System (CCRIS) for sodium cyanide, there was not a single positive result 

(CCRIS, 2010). Therefore, available data indicate that HCN does not have mutagenic 

properties and is not considered to be a carcinogen. Free CN is not classifiable as to 

human carcinogenicity (IRIS, 2010). 

Cumulative Exposure

HCN has a completely different mechanism of action than the other two acid gases on 

which comments have been requested (i.e., HCl and HF) and affects a different target 

organ system. While several studies indicate that chronic exposure of workers to low 

concentrations of cyanide can cause respiratory, cardiovascular, and thyroid effects, the 

acute effect on the CNS system occurs at lower concentrations than those at which the 

57 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 16 

portal of entry (respiratory) effects occur. Because HCN has a different mode of action 

than HCl and HF, it is not a candidate for a limit that addresses the combined effects of 

multiple acid gases. 

4. Hydrogen Fluoride (HF) 

Critical Target Organ 

The critical target organ for acute health effects of HF is the upper respiratory system 

(irritation), with symptoms such as coughing, choking, and chills, followed by pulmonary 

edema, which may occur with cough, chest tightness, rales, and cyanosis after an 

asymptomatic period of one to two days (CalEPA, 2008a). The critical chronic target 

organs include bone and teeth (skeletal/dental fluorosis), as well as the upper 

respiratory system (pulmonary hemorrhage) (CalEPA, 2008b). 

Mechanism of Action The acute respiratory effects of HF are the result of dehydration 

and corrosion of tissues mediated by free hydrogen ions (CalEPA, 2008a). The 

respiratory system is also listed as one of the critical target organs for chronic toxic 

effects of HF; however, respiratory effects result from higher exposure levels than 

required for fluorosis (Hodge and Smith, 1977). Presumably, direct contact irritation of 

tissues at the portal of entry and persistent cellular injury in the affected tissue are 

responsible for the chronic respiratory effects of HF. In addition, the dissociated fluoride 

ion is also capable of complexing certain bivalent cations, primarily calcium and 

magnesium, which interferes with calcium metabolism and causes cell destruction 

(CalEPA, 2008b) and fluorosis upon chronic exposure. Skeletal fluorosis is considered 

to be the critical target organ for chronic exposure since this effect is seen at lower 

concentrations than the respiratory system effects. 

Evidence of Threshold 

Both acute and chronic threshold doses have been established. In addition, since lower 

doses of fluoride have a beneficial or nutritional effect, a threshold type of response for 

adverse effects is clearly expected (CalEPA, 2008b). In addition to the general lack of 

evidence that HF is a carcinogen in humans (see discussion below), the listing of health 

thresholds for HF by California EPA (CalEPA, 2008b) and many other organizations 

(e.g., Agency for Toxic Substance Registry [ATSDR], World Health Organization 

[WHO], etc.) in the public domain has established HF as a threshold pollutant. 

Carcinogenicity

Several authors have suggested the potential mutagenicity of HF or sodium fluoride, 

although EPA and National Research Council have concluded that the mutagenicity of 

HF in man has not been demonstrated (EPA, 1998). According to the National 

Toxicology Program, "the preponderance of evidence" from laboratory in vitro (i.e., cell 

culture) studies indicate that fluoride is a mutagenic compound in laboratory studies. 

Some substances that are shown to be mutagens in laboratory studies, are also 

carcinogens. In some cases, “the overall significance of the in vitro fluoride 

transformation data are subject to question" (NRC, 1993) because the cells used in 

58 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 17 

some of the laboratory studies are unusually sensitive to the induction of transformation. 

In addition, the concentrations of fluoride causing mutagenic damage in the in vitro

studies is higher than the concentrations found in human blood. More importantly, no 

specific epidemiological evidence is available for evaluation of the potential 

carcinogenicity of HF or other fluoride compounds in humans. Increased rates of 

cancer have been reported in workers in several industries involving exposure to 

mixtures containing fluorides, but fluoride could not be specifically implicated as the 

cause of the cancer in any of these studies (EPA, 1998). The potential carcinogenic 

potential of fluorides in drinking water has also been investigated. The International 

Agency for Research on Cancer (IARC) concluded that when differences in 

demographics, degree of industrialization, and other social factors are accounted for, 

the studies provide no evidence that an increase in the level fluorides in drinking water 

is associated with an increase in cancer mortality (EPA, 1998). Therefore, there is a 

lack of evidence to suggest that HF or other fluoride compounds are carcinogenic. 

5. Manganese (MN) 

Critical Acute Target Organ

Mn toxicity has been reported through occupational (e.g. welder) and dietary 

overexposure and is evidenced primarily in the Central Nervous System, although lung, 

cardiac, liver, reproductive and fetal toxicity have been noted. The CNS is considered 

the critical target organ for the chronic toxicity of Mn (Crossgrove and Zheng, 2004). No 

information on acute toxicity of Mn could be located in the open scientific literature.

Mechanism of Action

Mn neurotoxicity results from an accumulation of the metal in brain tissue and results in 

a progressive disorder of the extrapyramidal system which is similar to Parkinson’s 

disease. In order for Mn to distribute from blood into brain tissue, it must cross either the 

blood–brain barrier (BBB) or the blood–cerebrospinal fluid barrier (BCB). Brain import, 

with no evidence of export, would lead to brain Mn accumulation and neurotoxicity. The 

mechanism for the neurodegenerative damage specific to select brain regions is not 

clearly understood. Disturbances in iron homeostasis and the valence state of Mn have 

been implicated as key factors in contributing to Mn toxicity (Crossgrove and Zheng, 

2004). 

Evidence of a Threshold 

Lower doses of Mn have a beneficial or nutritional effects, therefore, a threshold type of 

response for adverse effects is clearly expected. There is debate about where the 

threshold for Manganese falls, but several studies in the last two decades provide for 

determination of No Observed Adverse Effect Levels (NOAELs) for chronic neurological 

effects in workers. In addition to the lack of evidence that Mn is a carcinogen (see 

discussion below), the listing of health thresholds for Manganese by EPA, California 

EPA (CalEPA, 2008b) and the Agency for Toxic Substance Registry (ATSDR) in the 

public domain has established Manganese as a threshold pollutant. 

59 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 18 

Evidence of Carcinogenicity

Mn is listed in IRIS as Classification D (not classifiable as to human carcinogenicity) 

(IRIS, 2010). Although there are some mixed results, there are little data to suggest 

that inorganic Mn is carcinogenic. 

C. Summary and Conclusions Regarding Threshold Pollutant 

Determination 

1. Evidence for Thresholds 

Hydrogen Chloride (HCl) 

Based on the limited negative carcinogenicity data, and on knowledge of how chlorine 

reacts in the body, its likely mechanism of action, and its consideration as a threshold 

pollutant in numerous other rulemakings, HCl is presumptively considered to be a 

threshold pollutant. 

Chlorine (Cl2) 

Based on the thresholds established for Cl2, the lack of evidence for carcinogenicity, it’s 

likely mechanism of action, and it’s consideration as a threshold pollutant in numerous 

other rulemakings, Cl2 is presumptively considered to be a threshold pollutant. 

Hydrogen Cyanide (HCN) 

Based on the thresholds established for HCN, the lack of evidence for carcinogenity, 

and knowledge of how HCN reacts in the body, HCN is considered to be a threshold 

pollutant. 

Hydrogen Fluoride (HF) 

Based on the thresholds that have been established and lack of reliable data suggesting 

that HF is carcinogenic, HF is presumptively considered to be a threshold pollutant. 

Manganese (Mn) 

Lower doses of Mn have a beneficial or nutritional effects, therefore, a threshold type of 

response for adverse effects is clearly expected. In addition to the lack of evidence that 

Mn is a carcinogen (see discussion below), the listing of health thresholds for 

Manganese by EPA, California EPA (CalEPA, 2008b) and the Agency for Toxic 

Substance Registry (ATSDR) in the public domain has established Manganese as a 

threshold pollutant. 

2. Proposed Toxicity Factors and Margins of Safety 

Hydrogen Chloride (HCl) 

60 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 19 

It is proposed that the California EPA (CalEPA) acute Reference Exposure Level (REL) 

be established as the acute threshold dose and that the EPA RfC be established as the 

chronic threshold dose. The human studies on which the California acute REL is based 

were done with asthmatics, which represent a sensitive human subpopulation. Also, the 

chronic EPA RfC has a cumulative uncertainty factor of 300 (10 for extrapolation from a 

LOAEL to a NOAEL, 3 for interspecies variability, and 10 for intraspecies variability) 

built into it. Therefore, both the acute and chronic threshold values recommended for 

HCl provide an ample margin of safety for use in establishing emission standards under 

CAA112(d)(4). 

Chlorine (Cl2) 

It is proposed that the Agency for Toxic Substances and Disease Registry (ATSDR) 

acute Minimal Risk Levels (MRL) be established as the acute threshold dose. The 

acute no-observed-adverse-effect level (NOAEL) of 0.5 ppm was adjusted to account 

for continuous exposure (0.5 ppm x 8 hours/24 hours = 0.2 ppm). Although sensitive 

individuals were tested in some of the studies, an uncertainty factor of 3 was used to 

account for sensitive populations to arrive at the acute-duration inhalation MRL of 0.07 

ppm (0.2 ppm/3). It is also proposed that the ATSDR chronic MRL be established as 

the chronic threshold dose. An uncertainty factor of 30 (3 for extrapolation from 

animals to humans with dosimetric adjustment and 10 for human variability) was applied 

to the lower 95% confidence limit predicted exposure concentration associated with a 

10% extra risk to arrive at the chronic-duration inhalation MRL of 0.00005 ppm for Cl2. 

Therefore, both the acute and chronic threshold values recommended for Cl2 provide an 

ample margin of safety for use in establishing emission standards under CAA 112(d)(4). 

Hydrogen Cyanide (HCN) 

It is proposed that the California EPA (CalEPA) acute Reference Exposure Level (REL) 

be established as the acute threshold dose and that the EPA RfC be established as the 

chronic threshold dose. The California acute REL has a cumulative uncertainty factor of 

100 (10 for interspecies variability and 10 for intraspecies variability) built into it. In 

addition, the acute studies were done on primates, which represent the species most 

similar to man, thereby reducing uncertainty regarding toxic response. Also, the chronic 

EPA RfC has a cumulative uncertainty factor of 1000. A factor of 10 is used for 

sensitive human subpopulations, a factor of 10 is used for the lack of a NOAEL, and 

partial factors of 3 each are used for deficiencies in the database (lack of chronic and 

multigenerational reproduction studies) and for less than chronic duration. Therefore, 

both the acute and chronic threshold values recommended for HCN provide an ample 

margin of safety for use in establishing emission standards under CAA112(d)(4). 

Hydrogen Fluoride (HF) 

It is proposed that the CalEPA acute and chronic RELs be established as threshold 

doses for HF. Both the acute and chronic California RELs for HF incorporate a 

cumulative uncertainty factor of 10 to account for variability in human responses 

61 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 20 

(intraspecies variability) to inhalation exposure to HF. While this safety factor is not as 

large as some, both threshold values are judged to provide an ample margin of safety 

for use in establishing emission standards under CAA112(d)(4) since the studies were 

conducted in human populations, thereby eliminating much of the uncertainty regarding 

toxic responses. The chronic REL in particular is judged to be amply conservative 

because the human population consisted of fertilizer plant workers who were no doubt 

exposed to many other chemicals simultaneously. 

Manganese (Mn) 

No acute toxicity criteria for Mn were located in the open scientific literature. It is 

proposed that the EPA RfC be established as the chronic threshold dose. The chronic 

EPA RfC has a cumulative uncertainty factor of 1000. This uncertainty factor reflects 10 

to protect sensitive individuals, 10 for use of a LOAEL, and 10 for database limitations 

reflecting both the less-than-chronic periods of exposure and the lack of developmental 

data, as well as potential but unquantified differences in the toxicity of different forms of 

Mn. Therefore, the chronic threshold value recommended for Mn provides an ample 

margin of safety for use in establishing emission standards under CAA112(d). 

3. Health Effects Thresholds to be used for CAA112(d)(4) 

Emission Standards 

Both acute and chronic exposure to HCl, Cl2 and HF affect the respiratory system and 

the pollutants cause respiratory irritation by similar mechanisms of action (direct contact 

irritation of tissues at the portal of entry and persistent cellular injury in the affected 

tissue). However, the critical effect on which the chronic toxicity criterion for HF is 

based is skeletal fluorosis, which occurs at lower doses than the reported respiratory 

effects (Hodge and Smith, 1977). Therefore, it is recommended that a combined acute 

HBEL for HCl, Cl2, and HF and a combined chronic HBEL for HCl and Cl2 be 

established. However, a separate chronic 112(d)(4) HBEL for HF is recommended. 

While chronic exposure of workers to low concentrations of cyanide can cause 

respiratory symptoms, effects on the CNS system occur at lower concentrations than 

those at which the portal of entry (respiratory) effects occur. In addition, HCN has a 

completely different mechanism of action than HCl and HF. Therefore, HCN is not a 

good candidate for inclusion if a combined acid gas standard is derived. Therefore, 

establishment of a single acute 112(d)(4) HBEL for HCN is recommended. Although the 

critical target organ for Mn is the CNS, Mn has a completely different mechanism of 

action from HCN. Since Mn has a different mechanism of action from HCN and affects 

a different target organ than HCl and HF, establishment of a separate chronic 112(d)(4) 

HBEL for Mn is indicated as well. 

62 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 21 

4. How HBELs can be implemented under CAA Section 112(d)(4) 

EPA has a great deal of latitude in exploring other ways to “consider threshold levels 

with ample margin of safety”. Even though the MACT are primarily technology-based 

standards, the intent of section 112(d)(4) is to allow flexibility for EPA to establish 

special provisions for threshold HAPs that do not contribute significant health risk. Here 

we provide a conceptual model of how an HBEL could be incorporated into the Boiler 

MACT. 

Following the approach of the Health Based Compliance Alternative of the 2004 Boiler 

MACT rule, HBELs could either be established through conservatively-derived look-up 

tables (Tier 1 HBEL) or a facility could develop a site-specific HBEL based on modeling 

following EPA guidance (EPA, 2004) (Tier 2 HBEL). A facility would need to certify 

through fuel analysis or source testing that its boiler emissions meet the corresponding 

HBEL. Alternatively, limits for HCl and other pollutants that are already established in a 

facility’s air permit could be used in lieu of HBELs. 

Toxicity Considerations in Developing HBELs 

Because it is acknowledged that some of the HAPs subject to HBELs may have 

overlapping health effects, rather than considering only individual HAP exposure, the 

concept of Target Organ Specific Hazard Index (TOSHI) following U.S. EPA Guidance 

(EPA 2004) may be appropriate in some instances. The hazard index concept 

inherently assumes that potential health effects due to simultaneous exposure are 

additive. [This method was applied in the 2004 Boiler MACT HBCA where the effects of 

Cl2 and HCl were assumed to be additive by computing HCl toxic equivalent emissions. 

Although not elaborated in these comments, it is inherently assumed, that this same or 

similar approach for combining effects of Cl2 and HCl effects is appropriate.] As noted 

above, adding the health effects is appropriate for the acute health effects of the primary 

HAP acid gases from solid fuel industrial boilers, HCl, Cl2.and HF, and adding chronic 

effects of HCl and Cl2 is also appropriate. For instance, following the TOSHI concept, 

the development of acute HBELs for acid gases can consider combined emissions of 

HCl, Cl2and HF, and development of chronic HBELs can consider combined emissions 

HCl and Cl2 based on toxicity weighted emissions. In this case, an HCl acid gas 

toxicity-weighted short-term emission rate can be defined as the emission rate of HCl + 

the emission rate of Cl2 x Threshold of HCl /Threshold of Cl2 + the emission rate of HF x 

Threshold of HCl /Threshold of HF. 

Establishment of separate chronic 112(d)(4) HBEL for HF and HCN is supported since 

the critical effect/target organ on which the chronic toxicity criteria are based is different 

for the two acid gases and the mechanism of action is different as well. Because Mn 

63 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 22 

health effects and mechanisms of action can be differentiated from other HAPs, HBELs 

for Mn should be established independently. 

Tier 1 HBELs – Based on Physical Parameters using Look-up Tables

The HBELs could take the form of a limited number of alternative HAP emissions limits 

that would be based on simple physical parameters related to dispersion. These limits 

would be set in such a way that there would be no health effects due to inhalation of 

specified threshold HAPs such as acid gases (primarily hydrogen chloride) and metals 

such as Mn. 

EPA could develop Tier 1 HBELs based on screening-level dispersion modeling that 

conservatively relates maximum off-site concentrations associated with all Boiler MACT 

sources at a facility. A separate HBEL would apply to each facility based on the 

combination of physical stack parameters from each subject boiler. 

The physical parameters incorporated into the screening-level modeling used to 

develop the tables should include the basic parameters that govern the dispersion and 

are. These include: 

• Source characteristics, such as stack height and building height for each MACT 

source; 

• Distance to property line; 

• Maximum height of on-site structures; 

• Presence of highest nearby terrain (e.g., within 5 km). 

Tier 1 HBELs look-up tables would account for various combinations of these physical 

parameters. Because the look-up tables are based on screening-level dispersion 

models, such as SCREEN3 or AERSCREEN, that are designed to be conservative, this 

would provide the “ample margin of safety” as required by 112(d)(4). Thus, EPA can 

assure that compliance with the Tier 1 HBELs will mean that actual concentrations to 

which the public could be exposed are below established health effects threshold levels. 

The screening modeling that EPA would use to develop Tier 1 HBELs may address 

both chronic (annual average) and acute (maximum 1-hour) threshold effects, as 

appropriate. The determination of whether HBELs are appropriate for acute effects, 

chronic effects or both types of effects depends on whether an acute or chronic effect 

for a threshold HAP is universally demonstrated to be more limiting. EPA may 

conclude, as it did in 2004, that protection against chronic health effects will inherently 

safeguard against acute health effects. An example of the possible structure of Tier 1 

HBEL look-up tables is provided in Appendix H to these comments. 

64 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 23 

Tier 2 HBELs – Based on Site-specific Dispersion Modeling 

If facility boiler emissions exceed the conservatively derived Tier 1 HBELs or if the 

regulatory agency judges that the physical layout or dispersion environment of the site 

make it inappropriate to apply the Tier 1 HBEL look-up tables, a facility would conduct 

site-specific dispersion modeling. Site specific modeling would use source specific 

stack parameters and apply EPA’s state-of-the-science dispersion model AERMOD with 

five years of representative meteorological data. Model receptors could be placed at 

the boundary and in a specified grid representing off-site locations out to 5 km or could 

use site-specific receptor locations such as have been previously established for 

ambient air quality modeling. 

In this modeling, the combined impact of the specific HBEL HAPs would be modeled for 

the appropriate averaging times (1-hour for acute and annual average for chronic) and 

compared to established health effects benchmarks, such as those provided in Section 

B, Table 1 of these comments. As noted, to address acute effects of acid gases, it is 

appropriate to add the hazard quotients (HQ) (modeled concentration divided by health 

effects threshold) for HCl, Cl2, and HF to compute a hazard index (HI) for acute 

respiratory effects. A HI < 1.0 indicates that there is no incremental health effect. To 

address chronic effects of acid gases, it is appropriate to add the HQs (modeled 

concentration divided by health effects threshold) for HCl and Cl2 to compute a hazard 

index (HI) for chronic respiratory effects. As noted, for chronic effects of HF, HCN and 

Mn it is appropriate to evaluate threshold effects separately for each pollutant. To 

establish HBELs for each boiler, the facility would use the modeling to determine the 

combination of peak 1-hour and annual average emission rates that result in a HI or HQ 

of 1.0. Thus, if emissions from each subject boiler are less than these site-specific 

HBELs it will be assured that exposure will not exceed health effects thresholds as 

required under CAA Section 112(d)(4). 

D. Consideration of Overlapping Impacts of and Background HAPs 

for HCl 

Among the reasons cited by EPA for not proposing the HBEL for HCl in the 2010 Boiler 

MACT rule is the belief that impacts from other sources at the same facility or nearby 

facilities may need to be considered in evaluating risk. As noted above, the language of 

CAA Section 112(d)(4) indicates that only the potential threshold health effects from the 

MACT source should be considered. Furthermore combined risk sources from various 

MACT categories should be considered under the residual risk program, after MACT 

standards have been promulgated and implemented. However, even if an HBEL 

analysis were to consider these cumulative exposures, the effect would be minimal 

65 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 24 

because the evidence indicates that the potential incremental risk added as a result of 

overlapping plumes is very small. 

The chief acid gas HAPs emitted from most industrial boilers are chiefly HCl (since most 

elemental chlorine in fuel is converted to HCl during combustion) and HF. A review of 

TRI 2008 data (excluding EGUs, chemical plants, and metal mining) indicates that 

77.3% of acid HAP gas emissions are HCl, 22.4 % are HF and only 0.3% are HCN. As 

noted, the threshold effects of acid gases are dissimilar to other HAPs and, therefore, 

these can be considered separately from other HAPs using EPA’s TOSHI concept. At 

most types of industrial facilities that have substantial emissions of acid gases, solid fuel 

boilers subject to the boiler MACT (or other MACT such as the Hazardous Waste 

Combustor MACT) are the only significant source of these emissions. Because it is 

unlikely that there would be a substantial contribution of acid gas HAP emissions that 

are not regulated under the boiler MACT at most facilities, it should not generally be 

necessary to consider non boiler MACT sources in establishing HBELs. 

Another consideration potentially affecting HBEL development is whether boiler MACT 

source impacts from nearby facilities overlap. Even if this were applicable under CAA 

112(d)(4), dispersion modeling shows that maximum impact short-term and annual 

average concentrations of non-reactive pollutants associated with boiler emissions 

generally occur within 1 km and fall off rapidly with distance. This limits the range at 

which appreciable concentrations of these gases are transported. Because acid gases 

are highly soluble, react with ammonia the ambient air, and are rapidly deposited 

through wet and dry deposition, the range of ground-level concentrations is much more 

limited than for non-reactive pollutants. Therefore, unless there are boilers at an 

immediately adjacent facility, it is highly unlikely that impacts would overlap to the extent 

that it would materially affect the HBEL. 

There is no evidence that background concentrations of HCl are at appreciable levels 

from a public health perspective. A limited number of ambient measurement studies 

have shown that ambient concentrations, even in highly urbanized areas, are very low. 

A long-term measurement study of ambient acid gas concentrations in New York City 

(Bari et al 2003) indicates an average of about 0.5 μg/m3

, which is only 2.5% of the 

chronic RfC (Reference Concentration). Thus, there is little basis for adjusting the 

HBEL to adjust for background concentrations of acid HAP gases. 

A study of HCl emissions and impacts from utility boilers (Harkov 1999) concludes that, 

even in the vicinity of major sources of HCl, ambient concentrations are very low. This 

report states: 

66 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 25 

“In the atmosphere, HCl is fairly short-lived...since it is very soluble and reacts 

readily with ammonia (NH3) or alkaline cations such as Ca or K to form chloride 

salts. Therefore, even though the mass of HCl emitted may be substantial, the 

actual impacts of these emissions may not be significant. For example, data 

from the National Atmospheric Deposition Program (NADP 1998) National 

Trends Network deposition monitoring network over the years indicates that 

chloride ion deposition is strongly influenced by sea salts, rather than simply 

point sources of HCl emissions... EPA did not identify exceedances of any HCl 

health-based standards in the health risk studies reported in the Utility HAP 

Report (EPA 1998a).” 

The conclusion is that evaluation of non-boiler MACT, multiple facility and background 

do not need to be considered in establishing HBELs for acid HAP gases. 

Another assertion in the proposed Boiler MACT rule is that control of HCl emissions 

from solid fuel boilers will reduce acidic deposition. A map of chloride deposition in 

1997 (from Harkov, 1999) illustrates that there is no correlation between chloride 

deposition and distance from coal fired power plants in the Ohio Valley or industrial 

areas in the Midwest but is instead is related to the influence of sea salt, especially in 

the Pacific Northwest, New England and Southern Atlantic and Gulf coasts. Thus, there 

is no indication that HCl deposition from major point source emissions contribute 

materially to chloride deposition or acidification. 

 

67 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 26 

E. Realistic but Suitably Conservative Emission Rate Assumptions 

Can be Used to Estimate Compliance with Acute and Chronic 

HBELs 

In establishing compliance with HBELs, a facility will need to estimate upper-limit shortterm emissions to assess acute threshold health effects and annual average emissions 

to assess chronic threshold effects. Realistic, yet conservative, HAP emission rate 

assumptions should be used in determining compliance with HBELs under 112(d)(4) 

rather than across-the-board worst-case assumptions because using worst-case 

emission assumptions will materially overestimate both chronic and acute risk. EPA 

contends that a reason not to include a risk option such as HBEL is that there is lack of 

available data for HAP emissions from boiler sources. Although care must be taken in 

estimating emissions, for the HAPs under consideration, standardized methods could 

be established to develop suitably conservative emission estimates based either on fuel 

data or emission tests. 

If fuel testing is used, emissions for HCl, Cl2, HF, and Mn may be conservatively 

estimated based on knowledge of fuel type, measured fuel concentrations and use rate, 

assuming 100% of the HAP is released to the atmosphere. If source testing is used it 

will automatically account for a degree of HAP removal through bottom ash, and 

68 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 27 

emission controls. Because it is recognized that a single fuel sample or source test may 

not be representative of the long-term average, multiple fuel samples taken over an 

established period could be required. If a boiler has variable fuel sources,(e.g., coal 

from different mines or various types of wood), a number of samples from each source 

type would also be required. The variability of emissions would then be used following 

standardized data analysis methods to estimate the 95th percentile average emission 

factor to be used in the chronic HBEL compliance determination and combined with 

permitted annual fuel use. To account for short-term (hour-by hour) fluctuations the 

maximum hourly fuel use could be applied, along with a statistical estimate of the 95th

percentile concentration for each HAP to estimate emissions for the acute HBEL. 

This method of evaluating short-term fluctuations is highly conservative because the 

modeling used to develop the HBELs implicitly assumes that a source continuously 

emits each HAP at its 95th percentile maximum emission rate and that the worst-case 

emissions occur concurrently with worst-case dispersion conditions (Paine and Heinold 

2010). The degree to which this highly conservative assumption affects HBEL 

certification depends on whether the acute HBEL or the chronic HBEL is limiting. 

A similar procedure can be applied based on source test data. In the case where 

emission controls are in-place, the source could have the option of measuring 

uncontrolled or controlled emissions. If emission controls are used during the source 

test, additional parameters related to the control device would need to me monitored. 

F. References for HBEL comments: 

ATSDR, 2008. Toxicological Profile for Manganese. 

http://www.atsdr.cdc.gov/ToxProfiles/tp151.pdf. 

Bari, A., V. Ferraro, L. Wilson, D, Luttinger, L. Husain, 2003, Measurements of Gaseous 

HONO, HNO3, SO2, HCl, NH3, Particulate Sulfate and PM2.5 in New York, NY, Atmos. 

Environ. 37, 2825-2835. 

CalEPA, 2008a. California Environmental Protection Agency. Office of Environmental 

Health and Hazard Assessment. Appendix D.2 Acute RELs and toxicity summaries 

using the previous version of the Hot Spots Risk Assessment guidelines (OEHHA 

1999). http://www.oehha.ca.gov/air/allrels.html. 

CalEPA, 2008b. California Environmental Protection Agency. Office of Environmental 

Health and Hazard Assessment. Appendix D.3 Chronic RELs and toxicity summaries 

using the previous version of the Hot Spots Risk Assessment guidelines (OEHHA 

1999). http://www.oehha.ca.gov/air/allrels.html. 

CalEPA, 2008c. California Environmental Protection Agency. Office of Environmental 

Health and Hazard Assessment. Appendix D. Individual Acute, 8-Hour, and Chronic 

Reference Exposure Level Summaries http://www.oehha.ca.gov/air/allrels.html. 

69 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 28 

CCRIS. Chemical Carcinogenesis Research Information System. 

http://toxnet.nlm.nih.gov/cgi-bin/sis/search. 

Crossgrove, J. and Zheng, W., 2004. Review Article Manganese toxicity upon 

overexposure. NMR Biomed. 2004;17:544–553 Published online in Wiley InterScience 

(www.interscience.wiley.com). DOI:10.1002/nbm.931. 

Harkov, Ronald, 1999. Hydrogen Chloride (HCl) Emissions from Maryland Utility 

Boilers, Maryland Department of Natural Resources Maryland Power Plant Research 

Program, June. 

IPCS, 1982. International Programme On Chemical Safety. Environmental Health 

Criteria 21 Chlorine and Hydrogen Chloride. 

http://www.inchem.org/documents/ehc/ehc/ehc21.htm#SubSectionNumber:6.2.4. 

National Atmospheric Deposition Program (NRSP-3)/National Trends Network. 1998. 

NADP Program Office, Illinois State Water Survey, 2204 Griffith Drive., Champaign, IL. 

EPA, 1998. Summary Review of Health Effects Associated with Hydrogen Fluoride and 

Related Compounds. Health Issue Assessment. EPA600/8-89/002F. December, 1998. 

EPA. 1998a. Study of Hazardous Air Pollutant Emissions from Electric Utility 

Steam Generating Units-Final Report to Congress. EPA-453/R-98-004a. 

EPA, 2004. Air Toxics Risk Assessment Reference Library: Volume 2 Facility-Specific 

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

Standards (EPA-453-K-04-001B) http://www.epa.gov/ttn/fera/risk_atra_vol2.html, April. 

EPA, 2004a. National Emission Standards for Hazardous Air Pollutants for 

Industrial/Commercial/Institutional Boilers and Process Heaters: Final Rule 

EPA, 2004b. National Emission Standards for Hazardous Air Pollutants for 

Industrial/Commercial/Institutional Boilers and Process Heaters: Final Rule 

EPA, 2005. National Emission Standards for Hazardous Air Pollutants: Final Standards 

for Hazardous Air Pollutants for Hazardous Waste Combustors 

EPA, 2010. National Emission Standards for Hazardous Air Pollutants for Major 

Sources: Industrial, Commercial, and Institutional Boilers and Process heaters; 

Proposed Rule. 

Hodge, H.C. and Smith, F.A.: Occupational Fluoride Exposure. J. Occup. Med. 19:12–

39 (1977). 

HSDB, 2010. Hazardous Substance Databank. http://toxnet.nlm.nih.gov/cgibin/sis/htmlgen?HSDB. 

70 of 106
EPA–HQ–OAR–2002-0058 – HBEL Section of AF&PA comments 

August 23, 2010 

Page 29 

IPCS, 1982. International Programme On Chemical Safety. Environmental Health 

Criteria 21 Chlorine and HCl. 

http://www.inchem.org/documents/ehc/ehc/ehc21.htm#SubSectionNumber:6.2.4. 

IRIS, 2010. Integrated Risk Information System. http://toxnet.nlm.nih.gov/cgibin/sis/htmlgen?IRIS. 

Paine, R. and D. Heinold. Consideration of Emissions Variability in Modeling Short-Term 

Concentrations. Paper 751, presented at the 103rd Annual Conference and Exhibition of 

the Air & Waste Management Association, Calgary, Alberta, Canada. (2010). 

Santamaria, A.B. 2008. Manganese exposure, essentiality & toxicity Indian J Med Res 

128: 484-500. 

71 of 106
Appendix H – Tier I HBEL Lookup Tables 

Example Instructions for the Application of Tier 1 HBEL Look-up Tables that 

account for stack height, property boundary distance, building height and terrain 

1. Compute HAP Emissions for each MACT boiler unit at a facility. 

2. Determine the minimum stack height and distance to property boundary among 

MACT boilers. 

3. Perform Good Engineering Practice (GEP) Stack Height analysis following EPA 

guidance. Compare GEP height to each boiler stack height. 

4. If one or more boilers is less than GEP height, divide GEP stack height by 2.5 to 

determine effective building height to be applied in the table. 

5. Use stack height, building height and boundary distance to determine HBEL 

value from Table Xa. 

6. If all stack heights are above highest terrain within 5 km: Tier 1 HBEL = HBEL 

from Table Xa. If one or more stack heights are below highest terrain within 5 

km, proceed to step 7. 

7. Determine closest distance to terrain that is at or above minimum stack height. 

8. Look-up HBEL-b from Table Xb 

9. Tier 1 HBEL = lesser of HBEL from Table Xa and HBEL from Table Xb

72 of 106
Table Xa HAP1 HBEL (lb/hr) (according to stack height, boundary distance and building height) 

Distance to Property Boundary (m) 

Stack Height Effective 0 50 100 150 200 250 500 1000 1500 2000 3000 5000 

Building (m) Height 

(m) 5 NA 115 115 115 115 115 115 114 287 373 373 373 373 

10 NA 189 189 189 189 189 189 195 328 433 433 433 433 

20 8 386 386 386 386 386 386 386 425 580 603 603 603 

30 12 396 396 396 396 396 396 396 436 596 691 808 817 

30 20 307 307 307 307 307 307 307 338 462 535 626 632 

30 30 251 251 251 251 251 251 251 276 377 437 511 516 

40 16 408 408 408 408 408 408 408 448 613 716 832 966 

40 20 365 365 365 365 365 365 365 401 549 640 744 864 

40 30 298 298 298 298 298 298 298 327 448 523 608 705 

40 40 258 258 258 258 258 258 258 283 388 453 526 611 

50 20 421 421 421 421 421 421 421 461 631 746 858 1003 

50 30 344 344 344 344 344 344 344 376 515 609 701 819 

50 40 298 298 298 298 298 298 298 326 446 528 607 709 

50 50 267 267 267 267 267 267 267 291 399 472 543 634 

60 24 436 436 436 436 436 436 436 473 649 779 885 1043 

60 30 390 390 390 390 390 390 390 423 580 696 792 933 

60 40 337 337 337 337 337 337 337 367 503 603 686 808 

60 60 275 275 275 275 275 275 275 299 410 492 560 660 

70 28 450 450 450 450 450 450 450 487 667 814 912 1087 

70 40 377 377 377 377 377 377 377 407 558 681 763 910 

70 50 337 337 337 337 337 337 337 364 499 609 683 814 

70 70 285 285 285 285 285 285 285 308 422 515 577 688 

80 32 466 466 466 466 466 466 466 500 686 850 941 1135 

80 40 416 416 416 416 416 416 416 447 613 760 842 1015 

80 60 340 340 340 340 340 340 340 365 501 621 687 829 

80 80 294 294 294 294 294 294 294 316 434 537 595 718 

100 40 498 498 498 498 498 498 498 527 724 917 1001 1241 

100 60 406 406 406 406 406 406 406 431 591 749 817 1014 

100 80 352 352 352 352 352 352 352 373 512 648 708 878 

100 100 315 315 315 315 315 315 315 334 458 580 633 785 

200 80 677 677 677 677 677 677 677 682 920 1167 1390 1925 

200 100 606 606 606 606 606 606 606 610 823 1044 1244 1721 

200 150 495 495 495 495 495 495 495 498 672 852 1015 1406 

200 200 428 428 428 428 428 428 428 432 582 738 879 1217 

Table Xb HAP1 HBEL (lb/hr) (according to stack height and distance to elevated terrain) 

Distance to Off-site Terrain Above Stack Top (m)

Stack Height 50 100 150 200 250 500 1000 1500 2000 3000 5000 

(m) 5 57 57 57 57 57 57 144 187 187 187 187 

10 94 94 94 94 94 98 164 216 216 216 216 

20 193 193 193 193 193 193 213 290 301 301 301 

30 198 198 198 198 198 198 198 218 298 345 404 

40 204 204 204 204 204 204 204 224 307 358 416 

50 211 211 211 211 211 211 211 230 316 373 429 

60 218 218 218 218 218 218 218 237 325 389 443 

70 225 225 225 225 225 225 225 243 334 407 456 

80 233 233 233 233 233 233 233 250 343 425 470 

100 249 249 249 249 249 249 249 264 362 459 501 

200 339 339 339 339 339 339 339 341 460 584 695 

73 of 106
TAB 4 

74 of 106
January 20, 2011

Non-Hazardous Solid Materials Rule 

As our nation struggles to recover from the recession and the unemployment rate lingers at 

historic levels, non-hazardous solid waste rules that are central to Clean Air Act rules 

covering boilers could be unsustainable for U.S. manufacturing and the high-paying jobs it 

provides. Greater flexibility is needed to avoid unintended consequences. 

Background: 

As EPA develops rules for boilers, the Agency must also determine which combusted 

materials are fuels and which are solid wastes. Fuels may be burned in regulated boilers 

under the Boiler Maximum Achievable Control Technology (MACT) but solid waste must be 

burned in units regulated under another, more onerous and stigmatizing provision of the 

Clean Air Act (section 129 for Commercial and Industrial Solid Waste Incinerators -- CISWI). 

EPA is using its authority under the Resource Conservation and Recovery Act (RCRA) to 

make decisions about which materials are solid wastes and which are not. 

As energy costs rise and the nation moves towards alternative fuels, boiler owners continue 

to evaluate materials that can substitute for traditional fossil fuels. Materials that were once 

considered expendable, such as used tires, are now being routinely used as energy sources. 

Other materials, such as biomass residues from the manufacture of lumber, wood panels and 

paper making, have always been considered valuable commodities – whether used in 

production processes or for their fuel value. Many of these materials when burned are 

carbon-neutral. 

Boiler owners do not want their combustion units to be classified as solid waste incinerators 

because of the stigma associated with burning wastes. The public has a very negative view 

of waste incinerators and fights their permitting in their towns. Mills are likely to stop using 

non-traditional fuels rather than have to cope with the millions in added costs associated with 

CISWI regulations and public opposition. Collection and processing of these residuals 

creates jobs that will be lost if EPA doesn’t retain these materials as fuels. 

EPA appears to be taking a very narrow view of which materials are fuels and which are solid 

wastes. EPA has legal authority under RCRA, supported by numerous court decisions, to 

classify a wide range of materials as non-wastes and thus appropriately regulated under 

Boiler MACT. 

Policy Position: 

AF&PA supports the broadest definition of secondary materials as fuels eligible to be burned 

in boilers. This approach reduces our dependence on foreign oil, relies on a renewable 

resource and increases the use of carbon-neutral fuels – all national priorities. Furthermore, 

increasing the use of non-traditional fuels keeps energy costs down which enhances 

competitiveness while protecting and creating jobs. AF&PA is prepared to work with the EPA 

to protect both public health and jobs while using the flexibility of RCRA to come up with 

workable policies. 

75 of 106
TAB 5

76 of 106
1 

Summary of International Emission Limits for Industrial Boilers

December 2010 

Key Findings

Environmental regulatory programs vary across the globe. Each country has a unique set 

of laws and procedures to implement and ultimately enforce these requirements. 

Programs aimed at protecting air quality have evolved substantially over the last several 

decades in the United States and the rest of the world. At the same time, economies have 

changed dramatically with globalization and the increasingly competitive world 

marketplace. The rise of imports into the U.S. and the decline of exports raise significant 

concerns about the sustainability of the U.S. manufacturing sector and the jobs it 

supports. This document summarizes available information on air emissions standards 

for boilers in various countries and regions, such as the European Union, New Zealand, 

Australia, Canada, China, India, South Korea, Brazil, and South Africa. 

Of the countries examined in this review, the proposed EPA limits under the Industrial 

Boiler Maximum Achievable Control Technology (Boiler MACT) rule would be the 

most stringent limits on emissions from boilers from a number of perspectives. First, the 

U.S. has the only legislation that regulates 187 hazardous air pollutants (HAPs). This 

includes the five categories of emissions regulated by the Boiler MACT rules proposed 

by the U.S. Environmental Protection Agency (EPA): metallic HAPs whose surrogate is 

particulate matter (PM); acid gases such as hydrochloric acid (HCl); mercury (Hg); 

organic HAPs whose control surrogate is carbon monoxide (CO); and dioxin/furans. 

The European Union regulates some of these pollutants, but their program does not 

directly regulate mercury emission limits from boilers. The EU regulates only CO and 

PM from gas-fired boilers, not other HAPs. Other countries typically limit only PM 

emissions from boilers, and typically do not regulate emissions from gas-fired boilers. 

Those countries that have PM emission limits are concerned with the fine PM health 

concerns, not metallic HAPs per se (for which PM is a surrogate in EPA’s Boiler MACT 

proposal), with the possible exception of the transboundary pollution directive in the EU. 

Second, the U.S. and the EU have the tightest emission limits for boilers and have the 

only limits for gas-fired boilers. Additionally, the U.S. and EU are alone in having a 

focus on existing units. Although emissions limits in the EU are comparable to those in 

the proposed Boiler MACT, EU Directives have significantly more flexibility 

incorporated into them, such as the ability to include site-specific factors when 

establishing pollutant limits in permits, and the exclusion of periods of start-up, shutdown 

and malfunction (SSM) in determining compliance with emissions limits. The EU 

guidelines for establishing emission limits are based on what available combinations of 

control technologies are generally capable of achieving, not based on what a hypothetical 

best performing boiler could achieve on a pollutant-by-pollutant basis, which EPA uses 

to set its MACT standards. Furthermore, the enforcement system in the U.S. is unique in 

its litigious nature, role of citizen suits, inflexibility in remedies if standards or even 

77 of 106
2 

paperwork requirements are not met, implementation timeframes and significant 

penalties. 

Table ES1 summarizes emissions limits for countries included in this review. The table 

makes clear that EPA’s proposed Boiler MACT is the most strict boiler regulation of all 

the countries reviewed. This raises serious concern that, if finalized in its current form, 

EPA’s proposed Boiler MACT rule would create an unlevel playing field for U.S. 

manufacturers compared with their international competition. 

ES1. Summary of Regulated Compounds 

Country PM HCl Hg CO Dioxin/Furan 

European Union = - N = - 

New Zealand - N N N N 

Australia - N N N N 

Canada N N N N N 

China - N N N N 

India - N - N N 

South Korea - N N N N 

South Africa - N N N N 

Brazil - N N - N 

Russian Federation - N N N N 

Dominica - N N - N 

Indonesia - N N N N 

Jamaica - N N N N 

Japan - N N N N 

Malaysia - N N N N 

Thailand - N N N N 

Republic of Trinidad and Tobago - N N N N 

Tasmania - N N N N 

Turkey - N N N N 

Vietnam - N N N N 

 

“-“ means less stringent than U.S. 

“=” means comparable limit to U.S. 

“N” means not regulated 

78 of 106
3 

Compendium of Competitor Nation Clean Air Standards 

The following is a more detailed analysis of a dozen combustion source air emissions 

standards for key competitors of U.S. manufacturing. 

European Union 

The Integrated Pollution Prevention and Control (IPPC) Directive, promulgated in 

November 2010, sets more stringent limits for boilers specifically.1,2 The limits in this 

directive are summarized in Table 3.3

 Compliance is required for new sources by 2012 

and for existing sources by 2016, unless the source will shut down by 2023. 

Table 3. Emissions limits for dust for existing boilers using solid or liquid fuels with the 

exception of gas turbines and gas engines 

Total Rated 

Thermal 

Input 

Coal and 

Lignite Biomass and Peat Liquid Fuels 

mg/Nm3 mg/Nm3 lb/MMBtua mg/Nm3 lb/MMBtua

50-100 30 30 0.017 30 0.016 

100-300 25 20 0.011 25 0.013 

> 300 20 20 0.011 20 0.011 a

 Conversion from mg/Nm3 to lb/MMBtu for assumes biomass f factor of 9600 dscf/MMBtu liquid f factor 

of 9190 dscf/MMBtu. 

These values are comparable to the U.S. EPA’s proposed existing source MACT limits 

for biomass and coal boilers (0.02 lb/MMBtu), but higher than the proposed new source 

biomass boiler PM limits (0.008 lb/MMBtu), much higher than the proposed new source 

coal boiler PM limits (0.001 lb/MMBtu), and higher than the proposed existing and new 

liquid boiler PM limits (0.004 lb/MMBtu existing and 0.002 lb/MMBtu new). 

Table 4. Emissions limits for dust for new boilers using solid or liquid fuels with the 

exception of gas turbines and gas engines 

Total Rated Thermal Input 

(MW) 

Emissions limit 

(mg/Nm3) (lb/MMBtu) 

50 - 300 20 0.011 

> 300 10 0.006 

> 300 for biomass and peat 20 0.011 

The directive also contains a provision that strengthens the role of best available 

technology (BAT) in establishing emission limit values in permits. Specifically, the 

 

1

 Directive 2008/1/EC of the European Parliament and of the Council 15 January 2008 concerning 

integrated pollution prevention and control. Janurary 15, 2008. LINK. Accessed September 27, 2010. 

2

 Council of the European Union. Interinstitutional file 2007/0286 (COD). Proposal for a Directive of the 

European Parliament and of the Council on industrial emissions (integrated pollution prevention and 

control) (recast) – Outcome of the European Parliament’s second reading. July 12, 2010. 3

 All emissions limit values are calculated at 273.15 K, 101.3 kPa, and after correction for water vapor 

content at an oxygen content of 6% for solid fuels, 3% for combustion plants other than gas turbines and 

gas engines using liquid and gaseous fuels. 

79 of 106
4 

directive states that the permit granting body (competent authority) may set emission 

limit values (ELV) that differ from the emission levels associated with BAT values in 

terms of values, time periods, and reference conditions in the event that geography or 

technical considerations render achieving BAT disproportionately expensive considering 

the environmental benefits. Ultimately, however, emissions monitoring must 

demonstrate that emissions do not exceed BAT. 

Additionally, the directive contains the following provisions that render it more flexible 

than the U.S. EPA proposed Boiler MACT. 

• If applying an emission level associated with BAT will be overly expensive 

compared to the environmental benefits, competent authorities should be able to 

set limits that deviate from the BAT emission limits values based on well-defined 

criteria. The emissions levels in the directive, though, can not be exceeded. 

• If an operator is testing a promising new pollution control technique, the 

competent authority should grant temporary deviations from emissions levels 

based on BAT. 

• Within 24 hours of a malfunction, a combustion plant should cease operation or 

use low-polluting fuels. Unabated operation should not exceed 120 hours in a 12-

month period. If there is an overriding need for energy or the possibility of 

avoiding an overall emissions increase through operating another combustion 

plant to meet that need, the competent authority can grant a deviation from the 

emissions limits. 

• Member states can allow coverage of two or more partial or whole installations 

under one permit. Each entity under a permit must comply with the Directive’s 

requirements. 

• Emission limits based on BAT should not prescribe the use of any one particular 

technology to meet those limits. 

• Compliance with the emission limit values is considered achieved if none of the 

arithmetic averages of readings taken over a 24-hour period exceed the limit. The 

averaging period does not include times of start up, shutdown, and malfunction 

(SSM). Therefore, European installations are not penalized for emitting at levels 

higher than those in the Directive during times of SSM. 

The large combustion plant directive BREF4

 contains a chapter on combustion techniques 

for biomass and peat. Table 5 contains the emission limit values (ELV) that the chapter 

specifies beyond PM. 

 

4

 European Commission Joint Research Center. Integrated Pollution Prevention and Control Reference 

Document on Best Available Techniques for Large Combustion Plants. July 2006. 

http://eippcb.jrc.ec.europa.eu/reference/brefdownload/download_LCP.cfm. Accessed October 11, 2010. 

80 of 106
5 

Table 5. Emission Limit Values from Large Combustion Plant BREF and in the Proposed 

Boiler MACT 

Pollutant Emission Limit 

Value Emission Limit Value U.S. EPA Proposed Values 

Carbon Monoxide 50-250 mg/Nm3 40 – 200 ppmv at 7% 

O2

40 – 560 ppmv at 

7% O2

Hydrogen Fluoride 

and Hydrogen 

Chlorideb

< 25 mg/Nm3 0.014 lb/MMBtua 0.004 – 0.006 

lb/MMBtu 

Ammonia 5 mg/Nm3 0.003 lb/MMBtua N/A 

Dioxins and Furansc 0.1 mg/Nm3 9.47E+04 ng/dscm 0.0003 - 0.003 

ng/dscm 

a Conversion from mg/Nm3 to lb/MMBtu assumes biomass f factor of 9,600 dscf/MMBtu. 

b Additional values are established for combustion plants using straw as a fuel. 

c Conversion from Nm3

 to dscm assumes 1 Nm3 = 1.056 dscm. 

The range of ELV for carbon monoxide is comparable to U.S. EPA proposed limits. The 

U.S. EPA proposed standards for hydrogen chloride and dioxin are much tighter than 

those proposed in the EU. 

An agreement on the long-range transboundary air pollution from heavy metals in the EU 

limits particulate matter (as a proxy for heavy metals, including mercury) to 50 mg/m3

(0.028 lb/MMBtu assuming a biomass f factor of 9,600 dscf/MMBtu) from combustion 

installations with a net rated thermal input exceeding 50 MW.5

 This limit is less stringent 

than that in the IPPC Directive. 

Individual permit limits can be different from those in the BAT and/or directive as 

discussed above. For example, one French pulp and paper mill has the following 

emissions limits in its permit, which was issued in 2009.6 The ELVs for this plant that 

are established for pollutants the Boiler MACT regulates are in Table 6. 

Table 6. Emission Limit Values for French Pulp and Paper Mill 

Pollutant Emissions Limit Unit 

PM – Filt 0.04 lb/MMBtu 

Mercury 4.5 E-05 lb/MMBtu 

CO 230 ppm @ 3% O2

Of these limits, the CO limit is more stringent than the proposed EPA limit (560 ppm @ 

3% O2). 

Further, individual countries interpret each directive and can set different emissions 

limits. Germany has set the PM emission limits in Table 7 for installations generating 

 

5

 2001/379/EC: Council Decision of 4 April 2001 on the approval, on behalf of the European Community, 

of the Protocol to the 1979 Convention on Long-Range Transboundary Air Pollution on Heavy Metals. 

6

 Email from Glenn Rives, International Paper to Amy Marshall, URS dated October 15, 2010. 

81 of 106
6 

electricity through the combustion of coal, coke, coal briquettes, peat briquettes, fuel 

peat, or untreated wood with a rated thermal input of less than 50 MW.7

Table 7. PM Emission Limits from Combustion of Solid Fuels in Germany 

Rated Thermal Input Emission Limits 

(mg/m3) (lb/MMBtu)a

≥ 5 MW 20 mg/m3 0.011 

≤ 5 MW 50 mg/m3 0.028 

< 2.5 MW using exclusively untreated wood 100 mg/m3 0.055 a

 Assuming a biomass f factor of 9,600 dscf/MMBtu. 

The German regulation also limits CO emissions to 0.15 g/m3 (0.083 lb/MMBtu). If the 

furnace has a rated thermal input below 2.5 MW, the emission standard applies only to 

normal operating conditions (e.g., not during SSM). Further, when untreated wood is 

used, organic substances, measured as total carbon, should not exceed a limit of 10 

mg/m3, which is significantly higher than the proposed emissions levels in the Boiler 

MACT. 

If straw or similar plant matter is used, the PM emissions limit is 20 mg/m3 (0.011 

lb/MMBtu) for installations with rated thermal inputs above 1 MW. For installations 

with thermal input below 1 MW, a limit of 50 mg/m3 (0.028 lb/MMBtu) applies. 

Carbon monoxide emissions must be below 0.25 mg/m3 (0.0001 lb/MMBtu). The 

organic substance emissions limit is 50 mg/m3

 (0.028 lb/MMBtu). 

Existing sources must comply with these limits within eight years after the legislation 

became effective. 

These emission standards are in line with those in the IPPC Directive for installations 

with rated thermal input exceeding 5 MW. Germany, however, limits emissions from 

smaller installations than the EU-wide Directive. 

Luxembourg develops permits based on the strongest local regulations and on the 

German TA –Luft.10 The emissions limit on CO from fuel oil-fired boilers is 100 mg/m3

or 87 ppmv.8

 The corresponding limit for CO in the boiler MACT is 1 ppmv. 

New Zealand

Historically, PM emissions limits in New Zealand for PM were 250 mg/m3

 (0.139 

lb/MMBtu assuming a biomass f factor of 9600 dscf/MMBtu) for new boilers and 500 

mg/m3

 (0.278 lb/MMBtu) for existing boilers. Currently, a limit of 125 mg/m3 (0.069 

lb/MMBtu) is typical for new boilers.9 One report, however, indicates that there have 

 

7

 First General Administrative Regulation Pertaining to the Federal Imission Control Act (Technical 

Instructions on Air Quality Control – TA Luft). July 30, 2002. 

8

 Email from Alan Turner, DuPont to John deRuyter, DuPont, dated November 2, 2010. 

9

 Email from Rhys Kevern, URS to Amy Marshall, URS dated September 24, 2010. 

82 of 106
7 

been limits on TSP for boilers, but not generally PM10.

10 It seems in general, however, 

that limits on new installations are determined on a case-by-case basis.11 These limits are 

much higher than the proposed U.S. EPA Boiler MACT limits. 

Australia

In New South Wales state of Australia, in-stack concentrations of pollutants are subject to 

limits.12 The limit depends on the age of the equipment/facility, which determines into 

which group the equipment/facility falls. The following two tables lay out both the 

groupings and the emissions limits. 

Table 8. New South Wales emitting facility groupings13

Group Year of commencement 

1 Before 1972 

2 1972-1979 

3 1979-1986 

4 1987-1997 

5 1997-2005 

6 After 2005 

Table 9. Limits for solid particle (total) emissions14 for any activity or plant using a liquid 

or solid standard fuel or a non-standard fuel 

Group Limit (mg/m3

) Limit 

(lb/MMBtu)* 

1 400 0.222 

2, 3, or 4 250 0.139 

5 100 0.056 

6 50 0.028 

* Assuming a biomass f factor of 9600 dscf/MMBtu.

 

10 Environment Ltd. Improving PM10 Emission Factors from Industrial Boilers in New Zealand – Stage 1. 

July 2008. http://www.niwa.co.nz/__data/assets/pdf_file/0009/96093/Wilton-et-al-2008.pdf. Accessed 

September 27, 2010.

11 New Zealand Ministry for the Environment. Good Practice Guide for Assessing Discharges to Air from 

Industry. June 2008. http://www.mfe.govt.nz/publications/air/assessing-discharges-air-industryjun08/assessing-discharges-air-industry-jun08.pdf. Accessed September 27, 2010. 

12 Email from Rhys Watson, URS to Amy Marshall, URS dated September 24, 2010. 

13 New South Whales Government. 

http://www.legislation.nsw.gov.au/maintop/view/inforce/subordleg+428+2010+cd+0+N. Accessed 

September 27, 2010. 

14 New South Whales Government. 

http://www.legislation.nsw.gov.au/maintop/view/inforce/subordleg+428+2010+cd+0+N. Accessed 

September 27, 2010. 

83 of 106
8 

Victoria State’s State Environment Protection Policy regulates industrial air emissions 

including those from boilers.15 It depends on site-specific factors but there are indicatorspecific maximum emission limits for new and existing stationary sources. If the boiler 

meets receptor limits, the generic limits are generally met. The emissions limit for total 

particulate matter emissions from stationary sources in Victoria are 0.5 g/m3 (0.278 

lb/MMBtu assuming a biomass f factor of 9600 dscf/MMBtu).16 In air quality control 

regions, that limit drops to 0.25 g/m3

 (0.139 lb/MMBtu). 

The Group 6 emission rate is slightly higher than the U.S. EPA’s proposed existing 

source MACT limits for biomass and coal boilers, but quite a bit higher than the proposed 

new source biomass and coal boiler PM limits. 

Canada 

Canada does not have national limits on PM emissions from boilers. In Ontario, sulfur 

fuel content is limited to one percent.17

China

China implemented Environmental Protection Law in 1989. This Law contains the 

following (Tables 10 and 11) limits for controlled and uncontrolled boilers that are coalfired.18 The limits were converted to lb/MMBtu assuming that similar limits would apply 

to biomass-fired boilers. 

Table 10. China mainland emission limits for controlled boilers 

Boiler Type Applicable 

Area 

Emission Standard 

(mg/m3

)*** 

Emission Standard 

(lb/MMBtu)*** 

Period I** Period 

II** Period I** Period II** 

Natural 

Circulation 

(< 0.7 MW 

(1 t/h)) 

Zone 1 100 80 0.055 0.044 

Zone 2,3* 150 120 0.083 0.066 

Other Boilers 

Zone 1* 100 80 0.055 0.044 

Zone 2* 250 200 0.138 0.110 

Zone 3* 350 250 0.193 0.138 

 

15 Email from Timothy Routley, URS to Amy Marshall, URS dated September 24, 2010. 

16 Victoria Government. Environment Protection Act of 1970. State Environmental Protection Policy (Air 

Quality Management). 

http://epanote2.epa.vic.gov.au/EPA/Publications.nsf/d85500a0d7f5f07b4a2565d1002268f3/249fd0306cb8a

9d5ca256b43007ba829/$FILE/829.pdf. Accessed September 27, 2010. 

17 Government of Ontario. http://www.canlii.org/en/on/laws/regu/rro-1990-reg-338/latest/rro-1990-reg338.html. Accessed September 27, 2010. 18 IEA Clean Coal Center. http://www.iea-coal.org.uk/site/ieacoal/databases/worldwide-emissionstandards/china-volume-2?. Accessed September 27, 2010. 

84 of 106
9 

* Zones are defined in China’s ‘Air Quality Standards (GB 3095-1996) 

** Emission limit values for period I apply to boilers that began operation before December 31, 

2000, including boilers that were extended or modernized after December 31, 2000. 

*** Assuming a biomass f factor of 9,600 dscf/MMBtu. 

These limits and the limits in Table 8 below are higher than the proposed US EPA Boiler 

MACT limits. 

Table 11. China mainland emission standards from coal-fired boilers without emission 

controls 

Boiler Type 

Ash 

Content of 

Coal (as 

received 

%) 

Emission Standard 

(mg/m3) 

Emission Standard 

(lb/MMBtu)** 

Period I* Period 

II* Period I* Period II* 

Layer 

Combustion 

Stoker 

Boiler 

Natural 

Circulation 

(< 0.7 MW 

(1 t/h)) 

 150 120 0.092 0.073 

Other 

Boilers 

(≤2.8 MW 

(4 t/h)) 

≤25% 1,800 1,600 1.10 0.98 

≥25% 2,000 1,800 1.22 1.10 

Other 

Boilers 

(>2.8 MW 

(4 t/h)) 

≤25% 2,000 1,800 1.22 1.10 

≥25% 2,200 2,000 1.34 1.22 

Fluidized 

Bed 

Combusting 

(FBC) 

Boiler 

Circulating 

FBC 

Boiler 

 15,000 15,000 9.16 9.16 

Other FBC 

Boiler 20,000 18,000 12.21 10.99 

Spreader 

Stoker 

Boiler 

 5,000 5,000 3.05 3.05 

* Emission limit values for period I apply to boilers that began operation before December 31, 2000, 

including boilers that were extended or modernized after December 31, 2000. 

** Assuming a coal f factor of 9,780 dscf/MMBtu. 

India

The Indian Central Pollution Control Board (CPCB) limits emissions from industrial 

sources. In Part D of the General Environmental Standards, CPCB lays out general 

concentration-based emission standards. For PM, this standard is 150 mg/Nm3 (0.083 

lb/MMBtu assuming a biomass f factor of 9,600 dscf/MMBtu). For mercury, this 

standard is 0.2 mg/m3

 (0.0001 lb/MMBtu assuming a biomass f factor of 9,600 

85 of 106
10 

dscf/MMBtu). Annexure II puts forth specific emissions standards as Tables 12 and 13 

review. 

Table 12. General Emission Standards National PM Emission Standards19,20 

Source Emissions Limit 

(mg/m3

) 

Emissions Limit 

(lb/MMBtu)a

Thermal power plants commissioned before 

1/1/1982 with capacity < 62.5 MW 

350 0.083 

Bagasse-fired step grate 250 0.14 

Horse shoe/pulsating gratec 500b 0.28 

Spreader stokerc 800b 0.44 a Assuming a biomass f factor of 9,600 dscf/MMBtu. 

b

 12% CO2 c

 If more than one boiler is attached to a single stack, the standard is set based on capacity of all boilers 

exhausting to that stack. 

Table 13. National PM Emission Standards for Small Boilers21

Steam Generating 

Capacity (tonnes 

per hour) 

Emissions Limit 

(mg/m3)

Emissions Limit 

(lb/MMBtu)a

<2 1,200 0.66 

≥2 and < 10 800 0.44 

≥10 and < 15 600 0.33 

≥15 150 0.083 a Assuming a biomass f factor of 9,600 dscf/MMBtu.

South Korea

Table 14 contains PM emissions limits for industrial boilers and combustion 

facilities/boilers in South Korea. 

 

19 India Central Pollution Control Board. General Standards. 

http://www.cpcb.nic.in/GeneralStandards.pdf. Accessed October 28, 2010. 20 India Central Pollution Control Board. Standards for Bagasse-Fired Boilers. 

http://www.cpcb.nic.in/Industry-Specific-Standards/Emission/BagasseeFired%20Boilers.pdf. Accessed 

October 28, 2010. 

21 India Central Pollution Control Board. Standards for Small Boilers. http://www.cpcb.nic.in/IndustrySpecific-Standards/Emission/Boiler.pdf. Accessed October 28, 2010. 

86 of 106
11 

Table 14. South Korean Boiler Emission Limits

Pollutant Fuel Installed Time

(1) installed before Jun.30,2001 (mg/m3) (lb/MMBtu)

(2) installed after Jul. 1,2001 20 0.011(1) installed before Jan.31, 2007 40 0.021(2) installed after Feb. 1,2007 20 0.011

1) The standard & facility classification of Korean air regulation had changed from 20102) Upper table shows the stadard of general boiler, except combustion facility/boiler(i.e waste combustion boiler, waste gas combustion facility, etc)3) If other air pollutants except upper table are possibie to emit, those pollutants should be report to governmental office and regulated

4) Liquid fuels use f factor of 9,190 dscf/MMBtu; solid fuels use f factor of 9,600 dscf/MMBtu.

Standard

0.0270.0370.017

5030

0.0280.039

5070

Steam GeneratingCalorie

solid fuel mixture with 

liquid fuels

PM

Capacity

Steam GeneratingCalorieSteam GeneratingCalorie

5ton<Facility<20ton3,095,000<Facility<12,380,000kcal

Steam GeneratingCalorieSteam GeneratingCalorie

Every

<5ton<3,095,000kcal Every

Liquid 

Steam GeneratingCalorie

>20ton>12,380,000kcal

EveryEvery

Steam GeneratingCalorie

<5ton<3,095,000kcal Every 70>150ton>92,850,000kcal20ton<Facility<150ton12,380,000<Facility<92,850,000kcal5ton<Facility<20ton3,095,000<Facility<12,380,000kcal

87 of 106
12 

These limits are an order of magnitude higher than those proposed in the EPA Boiler 

MACT. 

South Africa

South Africa’s Regulations Relating to Listed Activities and Minimum Emission 

Standards limit air emissions from coal-fired power plants. The plant-wide PM 

emissions limit for new plants with capacity exceeding 70 MWh is 20 mg/m3

 (0.011 

lb/MMBtu).22 For existing plants, the PM emissions limit is 75 mg/m3

 (0.041 

lb/MMBtu). (Note that mg/m3 limits are converted to lb/MMBtu assuming a biomass f 

factor of 9,600 dscf/MMBtu.) 

Brazil

Brazilian emission limits for boilers that generate steam are presented in Table 15. 

Table 15. Brazilian Emission Limits for Steam-Generating Boilers 

Pollutant Fuel Thermal Capacity (MW) Installed Time lb/MMBtu OBS

< 10 installed after December 26, 2006 280 mg/Nm3 0.154

10 <= Capacity <= 75 installed after December 26, 2006 230 mg/Nm3 0.130

> 70 installed after December 26, 2006 200 mg/Nm3 0.110

< 10 installed after December 26, 2006 730 mg/Nm3 0.391

10 <= Capacity < 30 installed after December 26, 2006 520 mg/Nm3 0.278

30 <= Capacity < 70 installed after December 26, 2006 260 mg/Nm3 0.139

>= 70 installed after December 26, 2006 130 mg/Nm3 0.070

< 70 installed after December 06, 1990 1500 g/106

 Kcal 0.826

> 70 installed after December 06, 1990 800 g/106

 Kcal 0.441

<= 0,05 installed after December 26, 2006 6500 mg/Nm3 3.58

0,05 < Capacity <= 0,15 installed after December 26, 2006 3250 mg/Nm3 1.79

0,15 < Capacity <= 1,0 installed after December 26, 2006 1700 mg/Nm3 0.935

1,0 < Capacity <= 10,0 installed after December 26, 2006 1300 mg/Nm3 0.715

<= 0,05 installed after December 26, 2006 6500 mg/Nm3 3.48

0,05 < Capacity <= 0,15 installed after December 26, 2006 3250 mg/Nm3 1.74

0,15 < Capacity <= 1,0 installed after December 26, 2006 1700 mg/Nm3 0.910

1,0 < Capacity <= 10,0 installed after December 26, 2006 1300 mg/Nm3 0.696

1) The results should be expressed on a dry basis and corrected to 3% oxygen

2) The results should be expressed on a dry basis and corrected to 8% oxygen

NA: Not Applicable

2

Coal

PM

CO

Standard

Sugar Cane Bagasse

Wood

Wood 2

Sugar Cane Bagasse 2

2

These emission limits are significantly higher than those proposed in the Boiler MACT. 

Russian Federation

The Russian Federation has established PM emissions limits in its general technical 

requirements for boiler plants as summarized in Table 16.23

 

22 IEA Clean Coal Center. http://www.iea-coal.org.uk/site/ieacoal/databases/worldwide-emissionstandards/south-africa?. Accessed September 30, 2010. 23 State Standard of the Russian Federation. Boiler Plants. Thermal and Mechanical Equipment. General 

Technical Requirements GOST P 50831-95. 

88 of 106
13 

Table 16. Russian Federation Limits on PM from Boiler Plants 

Boiler Rating 

Q (MW) 

(boiler steam 

capacity 

(t/hr)) 

Adjusted 

Ash 

Content 

(% x 

kg/MJ) 

Bulk Particulate Concentration in Flue Gas 

Plants built prior to 12/31/00 Plants built after 12/31/00 

(mg/m3)

a

 (lb/MMBtu)b (mg/m3)

a

 (lb/MMBtu)b

≤ 299 

(≤ 420) 

< 0.6 150 0.083 150 0.083 

0.6 – 2.5 150 - 500 0.083 – 0.275 150 - 500 0.083 – 0.275 

> 2.5 500 0.275 500 0.275 

≥ 300 

(≥ 420) 

< 0.6 100 0.055 50 0.028 

0.6 – 2.5 100 – 400 0.055 – 0.220 50 – 150 0.083 

> 2.5 400 0.220 150 0.083 a

 At 0°C, 101.3 kPa, and an air-to-fuel ratio of 1.4. 

b

 Assuming a biomass f factor of 9,600 dscf/MMBtu. 

The Russian Federation also requires that the particulate matter content in the exhaust 

gasses of solid fuel boilers must be documented in the operating specifications for each 

boiler.24 Air dispersion modeling is also typically required to document air quality 

impacts from industrial source groupings. 

Additional Countries

The following countries have PM limits less stringent than those U.S. EPA is 

proposing.25

• Dominica; 

• Indonesia; 

• Jamaica; 

• Japan; 

• Malaysia; 

• Thailand; 

• Republic of Trinidad and Tobago; 

• Tasmania; 

• Turkey; and 

• Vietnam. 

Emission Limits on Gas-Fired Combustion Sources

Of the sources examined in the preparation of this compendium, only the EU IPPC 

directive2 contains limits on combustion sources firing natural gas for any of the 

compounds EPA is proposing to include in the Boiler MACT. A CO limit (100 mg/Nm3

or around 80 ppmv) is mandated for boilers firing natural gas. This limit is significantly 

 

24 State Standard of the Russian Federation. Hot-Water Heated Boilers Capacities from 0.1 to 4.0 MW. 

General Specifications. GOST 30735-2001. 

25 IEA Clean Coal Center. http://www.iea-coal.org.uk/site/ieacoal/databases/worldwide-emissionstandards/worldwide-emission-standards? Accessed September 29, 2010. 

89 of 106
14 

higher than EPA’s proposed CO limit for gas-fired boilers. Combustion plants fired with 

the following fuels are not subject to any CO limit: 

• Blast furnace gas 

• Coke oven gas 

• Low calorific gases from gasification of refinery residues 

• Other gases 

Table 17 contains the EU emission limit values for PM from gas-fired combustion plants. 

These limits are comparable to EPA’s proposed PM limits for new Gas 2 boilers. 

Table 17. PM Emission Limit Values from Gas-Fired Combustion Plants 

Gas Type Emission Limit Value 

(mg/Nm3) (lb/MMBtu) 

In general 5 0.003 

Blast furnace gas 10 0.006 

Gases produced by the steel 

industry which can be used 

elsewhere 

30 0.015 

Conversion from mg/Nm3 to lb/MMBtu assumes natural gas f factor of 8710 dscf/MMBtu. 

The best available technology that must be used to achieve CO emissions limits is 

complete combustion, which can be achieved through good furnace design, monitoring 

and process controls, and maintenance procedures. In highly populated areas, an 

oxidation catalyst may be considered appropriate BAT. For PM, the BAT recommended 

only for refinery or blast furnace gas is to apply pre-treatment measures like fabric filters. 

In summary, the EU limits only CO and PM from gas fired boilers and does not regulate 

other pollutants like HAPs that are included in the proposed Boiler MACT. There are 

different PM limits for gases derived from different sources, and CO emissions are only 

regulated from natural gas combustion. PM control technologies are considered BAT for 

units fired with refinery or blast furnace gas. In general, good combustion practices are 

considered BAT to control CO from gas-fired combustion plants.

90 of 106
15 

United States EPA Proposed Boiler MACT

Table 17. Boiler MACT emission limits as proposed in June 2010. 

Existing Biomass Boilers

Compound 

Original Existing 

MACT Limit 

Proposed 

Rule Units 

PM 0.07 0.02 lb/MMBtu 

HCl 0.09 0.006 lb/MMBtu 

Hg 9E-06 9E-07 lb/MMBtu 

Dioxin (TEQ basis) (no 

limit under original 

MACT) 

Susp burner/Dutch oven 0.03 TEQ ng/dscm @ 7% O2 

Fluidized Bed 0.02 TEQ ng/dscm @ 7% O2 

Fuel Cell 0.02 TEQ ng/dscm @ 7% O2 

Stoker/grate/other 0.004 TEQ ng/dscm @ 7% O2 

Carbon Monoxide (no 

limit under original 

MACT for existing) 

Susp burner/Dutch oven 1010 ppm @ 3% O2 

Fluidized Bed 250 ppm @ 3% O2 

Fuel Cell 270 ppm @ 3% O2 

Stoker/grate/other 560 ppm @ 3% O2 

Existing Coal Boilers

Compound 

Original Existing 

MACT Limit 

Proposed 

Rule Units 

PM 0.07 0.02 lb/MMBtu 

HCl 0.09 0.02 lb/MMBtu 

Hg 9E-06 3E-06 lb/MMBtu 

Dioxin (TEQ basis) (no 

limit under original 

MACT) 

Stoker/grate/other 0.003 TEQ ng/dscm @ 7% O2 

Pulverized Coal 0.004 TEQ ng/dscm @ 7% O2 

Fluidized Bed 0.002 TEQ ng/dscm @ 7% O2 

Carbon Monoxide (no 

limit under original 

MACT for existing) 

Stoker/grate/other 50 ppm @ 3% O2 

Pulverized Coal 90 ppm @ 3% O2 

Fluidized Bed 30 ppm @ 3% O2 

Existing Liquid Fuel Boilers

Compound 

Original Existing 

MACT Limit 

Proposed 

Rule Units 

PM NA 0.004 lb/MMBtu 

HCl NA 9E-04 lb/MMBtu 

Hg NA 4E-06 lb/MMBtu 

Carbon Monoxide NA 1 ppm @ 3% O2 

Dioxin (TEQ basis) NA 0.002 TEQ ng/dscm @ 7% O2 

Existing Units burning gases other than natural gas or refinery gas

Compound 

Original Existing 

MACT Limit 

Proposed 

Rule Units 

PM NA 0.05 lb/MMBtu 

HCl NA 3E-06 lb/MMBtu 

Hg NA 2E-07 lb/MMBtu 

Carbon Monoxide NA 1 ppm @ 3% 

Dioxin (TEQ basis) NA 0.009 TEQ ng/dscm @ 7% O2 

91 of 106
16 

New Biomass Boilers 

Compound 

Original NEW MACT 

Limit 

Proposed 

Rule Units 

PM 0.025 0.008 lb/MMBtu 

HCl 0.02 0.004 lb/MMBtu 

Hg 3E-06 2E-07 lb/MMBtu 

Dioxin (TEQ basis) (no 

limit under original 

MACT) 

Susp burner/Dutch oven 0.03 TEQ ng/dscm @ 7% O2 

Fluidized Bed 0.007 TEQ ng/dscm @ 7% O2 

Fuel Cell 5E-04 TEQ ng/dscm @ 7% O2 

Stoker/grate/other 5E-05 TEQ ng/dscm @ 7% O2 

Carbon Monoxide 

(original new MACT 

limit of 400) 

Susp burner/Dutch oven 1010 ppm @ 3% O2 

Fluidized Bed 40 ppm @ 3% O2 

Fuel Cell 270 ppm @ 3% O2 

Stoker/grate/other 560 ppm @ 3% O2 

New Coal Boilers 

Compound 

Original New MACT 

Limit 

Proposed 

Rule Units 

PM 0.025 0.001 lb/MMBtu 

HCl 0.02 6E-05 lb/MMBtu 

Hg 3E-06 2E-06 lb/MMBtu 

Dioxin (TEQ basis) (no 

limit under original 

MACT) 

Stoker/grate/other 0.003 TEQ ng/dscm @ 7% O2 

Pulverized Coal 0.002 TEQ ng/dscm @ 7% O2 

Fluidized Bed 3E-05 TEQ ng/dscm @ 7% O2 

CO (original new 

MACT limit of 400) 

Stoker/grate/other 7 ppm @ 3% O2 

Pulverized Coal 90 ppm @ 3% O2 

Fluidized Bed 30 ppm @ 3% O2 

New Liquid Fuel Boilers 

Compound 

Original New MACT 

Limit 

Proposed 

Rule Units 

PM new large: 0.03 0.002 lb/MMBtu 

HCl new large: 0.0005 4E-04 lb/MMBtu 

Hg NA 3E-07 lb/MMBtu 

Carbon Monoxide 400 1 ppm @ 3% O2 

Dioxin (TEQ basis) NA 0.002 TEQ ng/dscm @ 7% O2 

New Units designed to burn other gases 

Compound 

Original New MACT 

Limit 

Proposed 

Rule Units 

PM NA 0.003 lb/MMBtu 

HCl NA 3E-06 lb/MMBtu 

Hg NA 2E-07 lb/MMBtu 

Carbon Monoxide 400 1 ppm @ 3% O2 

Dioxin (TEQ basis) NA 0.009 TEQ ng/dscm @ 7% O2 

Some countries have PM emission limits for boilers that are fairly comparable to EPA’s 

proposed existing source PM emission limits for coal and biomass boilers. EPA 

proposed limits for new source biomass boilers, new source coal boilers, and proposed 

existing and new liquid boilers are tighter then those being considered in the EU. In the 

EU, proposed limits on dioxin and hydrogen chloride are above those proposed in the 

92 of 106
17 

U.S. Proposed CO emissions limits are comparable in the U.S. and EU. Other countries, 

including China and India, have promulgated less stringent PM limits for new and 

existing boilers than those in the proposed boiler MACT. 

93 of 106
TAB 6

94 of 106
1

Boiler MACT and Benefit Claims 

Some have argued that for EPA revise its proposed Boiler MACT rule would create a 

threat to public health. However, these concerns fail to consider some important 

factors, where the rule’s MACT benefits can be maintained while reducing costs and 

protecting jobs. 

• MACT is the cornerstone of the air toxic program in Title III of the Clean Air Act 

focused on reducing Hazardous Air Pollutants (HAPs). Yet the only quantified health 

benefits from the Boiler MACT come from reducing emissions of fine particulate 

matter (PM2.5) and PM2.5 precursors such as sulfur dioxide (SO2), rather than 

HAPs. This leads to the claim that for every dollar spent five to twelve dollars in 

health benefits will be realized. EPA needs to focus on the HAP reductions and find 

alternative approaches that can obtain those benefits at far lower cost using the 

flexibility in the law. For example, roughly 70% of the mercury costs come from 

controls on biomass and oil which represent only 5% of the total emissions from 

industrial boilers. 

• The estimated PM2.5 benefits (2,000 to 5,100 premature deaths plus other morbidity 

effects, such as bronchitis and non fatal heart attack); if they are to be believed (see 

comment below), appear to be the same benefits claimed in the 2006 PM2.5 

NAAQS revisions. This approach would be double counting the benefits. 

• The major recommendations for improvements in the proposed rule, such as use of 

the source based approach, greater consideration of variability, and accounting for 

the skewed data set, will lead to standards more stringent than the 2005 limits and 

require billions in new investments but not be unachievable or ultra low. The vast 

majority of the HAP benefits come from reducing emissions from the dirtiest units. 

For example, going from 10 lb/T Btu mercury to 3 lb/T Btu and not all the way to 0.9 

lb/T Btu for biomass boilers will still achieve an emissions reduction from the highest 

emitters at a fraction of the cost and will still preserve most of the 15,000 ton 

estimated reductions, as these are primarily based on emissions reductions from 

coal-fired boilers. 

• The language of Section 112 clearly states that EPA can look at other non-air quality 

benefits like energy use but not other air pollutants like PM and SO2. Thus, it is 

illegal to factor in these “co-benefits” to justify not choosing flexible options like the 

health based emission limit. 

• Efforts to reduce PM and SO2 should be left to the Title I State Implementation Plan 

(SIP) program and not become the rationale for tougher MACT rules, as Congress 

intended. Congress clearly created two distinct programs – one where MACT sets 

nationwide controls for air toxics and a second where controls for pollutants like PM 

and SO2 are targeted to non-attainment areas where air quality problems exist. 

Many boilers are located in areas far from non-attainment areas so the proposed 

MACT would not help these areas reach attainment. In fact, only 4% of the SO2 

95 of 106
2

emissions from paper mills occur in non-attainment areas given our rural based 

industry. This comes after the industry has reduced SO2 emission by 37% since 

1995. 

• Finally on the subject of PM benefits, it is worth pointing out just how uncertain and 

overstated they are based on a careful look at the health science. First, EPA’s most 

recent estimates of risk from exposure to PM2.5 shows less risk than in 1997 when 

EPA issued the standards for the first time. Second, the key studies relied upon by 

EPA fail to explain a “cause and effect” between PM2.5 and health effects. Third, the 

uncertainties in the science are greater now than when the original standards were 

established suggesting that further reductions may be overvalued. Finally, EPA has 

“cherry picked” the results by relying on selected studies showing effects and 

ignoring many others. 

• EPA failed to include any cancer or non-cancer benefits in the Regulatory Impact 

Analysis for Boiler MACT. However, EPA’s assessment of all MACT source 

categories shows that the toxicity weighted cancer emissions from boilers represent 

about 5% of the total and less than 1% of non-cancer toxicity weighted emissions. 

(see EPA OAQPS slide on NEI risks). 

96 of 106
TAB 7 

97 of 106
Selected Quotes from Governors on Boiler MACT

(October 2010) 

Alabama Governor Bob Riley (R) 

“As our state’s unemployment rate hovers around 11 percent, enacting stringent 

federal Boiler MACT rules would jeopardize more good paying jobs across the 

manufacturing sector.” ... “While I support efforts to address serious health 

threats from air emissions, I also believe that regulations can be crafted in a 

balanced way that sustains both the environment and jobs. “ 

Arkansas Governor Mike Beebe (D) 

 

“While I strongly support efforts to address serious health threats from air 

emissions, I feel that where no risk to public health is posed, regulations should 

be crafted in a balanced way that sustains both the environment and jobs. “ 

“We understand that it is often difficult for the EPA to consider and address broad 

environmental effects when dealing with specific media-related rulemaking. 

However, I feel that the time is ripe with this rulemaking to do just that. The EPA 

has promoted the development of alternative energy sournces for a number of 

reason, including the protection of air quality. Unfortunately, when one looks at 

EPA’s specific rulemaking, the impact has been to discourage that very goal. 

This proposed rule is an example.” 

California Governor Arnold Schwarzenegger (R) 

“California has adopted some of the nation’s most ambitious renewable energy 

and greenhouse gas reductions goals and I am concerned that rule changes 

being considered by your agency will undermine the progress we are making.” 

“I know the Obama Administration is working as hard as we are to increase, not 

eliminate, green jobs.” 

“While I support your efforts to adopt national regulations to reduce hazardous air 

pollutants, I have significant concerns that these proposed standards would have 

adverse impact on California’s environment and economy. “ 

Georgia Governor Sonny Perdue (R) 

“Being good stewards of our environment is a principle that is very close to the 

hearts of Georgians and I certainly desire to protect Georgians citizens from 

exposure to harmful compounds. However, the proposed rule is unreasonable 

and will impose serious – perhaps fatal – hardships on significant sectors fo the 

economy just as the first fragile signs of economic recovery begin to emerge. “ 

98 of 106
“I know that we share many of the same concerns of protecting the environment 

and the welfare of our citizens. As you move forward in the process of finalizing 

a Boiler MACT rule, I hope that you will recognize that the welfare of our citizens 

is dependent on many factors, not the least of which is the availability to find 

good jobs, plan for the future, and provide for their families. This will require the 

final Boiler MACT rule to be reasonable and workable.” 

Hawaii Governor Linda Lingle (R) 

“Hawaii, as an island state, relies on the importation and refining of crude oil for 

its electrical generation, transportation, and aviation needs... The proposed rule 

would impose emission standards for liquid fired process heaters and boilers that 

are infeasible for Hawaii’s refineries to meet.” 

Idaho Governor Butch Otter (R) 

“ I am concerned the combination of the depressed economy and all the new 

regulatory burdens proposed by EPA, such as the Green House Gas Tailoring 

rule and the upcoming potential reduction in the ozone standard to name a few, 

could be devestating on Idaho business. I question why EPA is not employing all 

the flexibility of its authoriry.” 

“I urge you to use your discretionary authority under 112(d)(4), as was orginally 

proposed in the 2004 Boiler MACT rule, to provide small business and larger 

industries with the flexibility they need to continue to protect air quality and to 

remain economically healthy for both Idaho and the nation.” 

Maine Governor John Baldacci (D) 

“The proposal concludes that the use of the authority under Section 112(d)(4) of 

the Clean Air Act is discretionary and EPA does not support its use in Boiler 

MACT. I believe that provision reflects Congress’ intent to provide for flexibility 

where there is not a public health threat. In such cases, it makes sense to allow 

that approach in the final rule for threshold substances.” 

“EPA should use a method to set emissions standards that is based on what real 

world best performing units actually can achieve for all the regulated pollutants. 

EPA should not ignore biases in its emissions database, the practical capabilities 

of controls or the variability in operations, fuels and testing performance across 

the many regulated subcategories of boilers.” 

Minnesota Governor Tim Pawlenty (R) 

“The pending regulations would be a blow to these [economic recovery] efforts by 

diverting investments from job creation and economic expansion, particularly for 

99 of 106
manufacturing, the forest products industry, and both small and large 

businesses. Likewise, these rules would impact state and local government 

facilities and higher education institutions.” 

“As you develop a final Boiler MACT rule, please consider an approach that 

fosters economic recovery and job growth balanced with environmental 

protection.” 

Mississippi Governor Haley Barbour (R) 

“Because of the costly control devices that would have to be installed, the 

pending Boiler MACT policy could restrict resources for potential investment and 

hiring, therefore, jeopardizing the future of the manufacturing industry and its 

important role in the state’s economy.” 

North Carolina Governor Bev Perdue (D) 

“North Carolina has been a national leader in addressing serious health threats 

from air emissions. However, our efforts have been grounded in a belief that 

regulations need to be balanced, in order to sustain both the environment and 

our competitive position in the world marketplace, and still maintain jobs for North 

Carolinians. “ 

“I encourage EPA to use a method to set emissions standards based on what 

real world, best performing units actually can achieve for all the regulated 

pollutants... Clearly, EPA should not adopt Boiler MACT standards that 

commercial suppliers of such equipment say are unattainable.” 

Ohio Governor Ted Strickland (D) 

“I ask that the U.S. EPA give appropriate attention to the economic impact of the 

rule on Ohio businessess, including the potential for job loss resulting from such 

large capital investments.”

 

Oregon Governor Ted Kulongoski (D) 

“I ... write to express my concern about a potential unintended consequence of 

the proposed Boiler MACT rule... While these regulations are important to 

protect public health from hazardous air pollutants, I am particularly concerned 

about the impact these regulations could have on our growing renewable energy 

sector. ....because of variability in boiler design and fuel quality, the proposed 

limits may be impracticable for many existing biomass boilers. This could work 

against our goal to expand the use of sustainable biomass as a part of our GHG 

reduction efforts.” 

100 of 106
“As EPA develops a final Boiler MACT rule, I hope you will carefully consider 

sustainable approaches that protect the environment and public health while 

fostering economic recovery and jobs within the bounds of the law.” 

Virginia Governor Bob McDonnell (R) 

“I believe we can all agree that risks to public health should be a principal 

concern when designing such regulations. However, the proposed Boiler MACT 

rule misses the opportunity to avoid controls where certain air emissions are not 

a problem. Instead, it should be redrafted to support a health based approach 

and set standards that reflect the variety of boilers in use and their variable 

performance.” 

“The final Boiler MACT rule needs to be reasonable and workable. As your 

Administration moves toward finalizing this rule, I ask that you make the 

necessary adjustments to protect health of our citizens without threatening their 

livelihoods and the recovery of our economy.” 

Washington Governor Christine Gregoire (D) 

“I write to express my concern that your agency’s proposed rule to establish 

‘maximum achievable control technology’ for industrial, commerical and 

institutional boilers could undermine the progress we are making in Washington 

State with renewable bioenergy. While I strongly support the need for updated 

rules that protect public health from hazardous air pollutants, I believe this can be 

accomplished with attainable technologies and appropriate flexibility to reduce 

economic harm and unitended environmental effects.” 

Wisconsin Governor Jim Doyle (D) 

“The importance of balancing environmental protection with economic vitality has 

been a central theme for my administration during my two-terms as Governor of 

Wisconsin. . . However, I am greatly concerned that the Boiler MACT rule 

currently proposed by your agency [EPA} works against a sustainable future for 

Wisconsin and the nation.” 

“As EPA develops a final Boiler MACT rule, I hope you will consider a balanced 

approach that is sustainable, protects public health and the environment and 

fosters energy independence, economic recovery and jobs.” 

101 of 106
102 of 106
103 of 106
November 11, 2010

The Honorable Lisa Jackson

Administrator

United States Environmental Protection Agency 

Ariel Rios Building 

1200 Pennsylvania Avenue, N. W. 

Washington, DC 20460

Dear Administrator Jackson:

We are writing to express our concerns about the proposed Boiler MACT rule –

the Maximum Achievable Control Technology rule for industrial, commercial and 

institutional boilers and process heaters – and the other associated rules that were 

published on June 4th. As our nation struggles to recover from the current recession, we 

are deeply concerned that the potential impact of pending Clean Air Act regulations 

would be harmful to U.S. manufacturing and the high-paying jobs it provides, as well as 

all sectors of the US economy. Both small and large businesses are vulnerable to 

extremely costly regulatory burdens, as well as municipalities, universities, federal 

facilities, and commercial entities. The flow of capital for new investment and hiring is 

still seriously restricted, and the costs imposed by these regulations as proposed could 

make or break the viability of continued operations. As proposed, the Boiler MACT rule 

alone could impose over twenty billion dollars in capital costs at thousands of facilities 

across the country and billions more in operating costs. 

We support efforts to address significant health threats from air emissions in a 

cost effective manner, and also believe that regulations can be crafted to accomplish

this and still protect jobs and economic growth. Thus, we appreciate your willingness, as 

expressed in your responses to recent Congressional letters, to consider changes to the 

proposed rules and incorporating flexible approaches that appropriately address the 

diversity of boilers, operations, sectors, and fuels that could provide assurance of 

achievability and prevent severe job losses and billions of dollars in unnecessary 

regulatory costs. 

Specifically, we encourage EPA to set standards based on what real-world 

sources actually can achieve. EPA has proposed a pollutant-by-pollutant approach 

based on the “best performers” for each of five separate Hazardous Air Pollutants 

(HAP)/ surrogate emissions categories. This approach had many data and methodology 

problems, and resulted in a set of standards such as those for dioxin, mercury and 

carbon monoxide that cannot be met by even the best performing actual boilers and 

process heaters. 

EPA should finalize work practices for all gas and distillate oil fired units at major 

sources and oil and biomass fired boilers located at area sources to avoid the increase 

104 of 106
in emissions (e.g., NOx and CO2) and energy use that would result from the numerous 

control technologies required to meet the proposed emission limits with no guarantee of 

actually achieving those limits. 

In addition, EPA should provide an alternative health-based emissions approach 

for qualifying low-risk emissions. A practical, health-oriented standard for threshold 

pollutants would allow sources to demonstrate that their emissions of these pollutants 

do not pose a public health concern. Section 112(d)(4) of the Clean Air Act expressly 

contemplates the use of such a standard, which can be implemented at each facility to 

protect public health. 

In the related rule defining “Non-Hazardous Secondary Materials,” EPA should 

reaffirm that many secondary materials including biomass and biomass processing 

residuals are not solid wastes. The statute and related case law allow EPA to classify 

these materials as fuels if they are not discarded, are treated as valuable commodities, 

and are burned for energy recovery. Failure to encourage these alternative and often 

renewable fuels will result in more materials being landfilled and increase use of fossil 

fuels. 

Lastly, EPA should promulgate work practice standards for dioxins/furans in 

Boiler MACT due to the many problems with emissions measurement, lack of 

knowledge of conditions and unit features leading to those emissions, and the inability 

to further control emissions at the already extremely low emission rates shown for these 

units. 

As EPA turns to developing the final Boiler MACT and related rules, we believe it 

is imperative that EPA utilize adequate time and resources to fully evaluate all 

comments and data provided through the public comment process so that a reasonable 

rule can be promulgated. We appreciate your willingness to consider our suggestions. 

Sincerely,

American Chemistry Council

American Coke & Coal Chemicals Institute

American Forest & Paper Association

American Home Furnishings Alliance

American Municipal Power

American Petroleum Institute

American Public Power Association

American Sugar Alliance

American Wood Council

Associated Oregon Industries

Biomass Thermal Energy Council

105 of 106
Brick Industry Association

California Cotton Ginners Association

Composite Panel Association

Corn Refiners Association

Council of Industrial Boiler Owners

Empire States Forest Products Association

Hardwood Federation

Hardwood Manufactures Association

Hardwood Plywood and Veneer Association

Indiana Hardwood Lumbermen's Association

Indiana Manufacturers Association

Industrial Energy Consumers of America

Kentucky Forest Industries Association

Lake States Lumber Association

National Alliance of Forest Owners

National Association of Manufacturers

National Cotton Ginners’ Association

National Hardwood Lumber Association

National Oilseed Processors Association

National Rural Electric Cooperatives Association

National Wood Flooring Association

Northeastern Loggers’ Association

Ohio Manufacturers' Association

Ohio Municipal Electric Association

PA Anthracite Council

Pellet Fuels Institute

Pennsylvania Forest Products Association

Rubber Manufacturers Association

Society of Chemical Manufacturers and Affiliates

Southeastern Lumber Manufacturers Association

Tennessee Chamber of Commerce & Industry

Texas Cotton Ginners’ Association

The Aluminum Association

The State Chamber of Oklahoma

Treated Wood Council

U.S. Chamber of Commerce

Utah Manufacturers Association

Virginia Manufacturers Association

Wisconsin Paper Council

cc: Regina McCarthy, Environmental Protection Agency 

Robert Perciasepe, Environmental Protection Agency 

Cass Sunstein, Office of Management and Budget 

106 of 106