From:    "Higgins, Cortney" <Cortney_Higgins@omb.eop.gov>                                                                                         

To:    Keith Barnett/RTP/USEPA/US@EPA                                                                                                           

Cc:    Charlotte Bertrand/DC/USEPA/US@EPA                                                                                                       

Date:       08/05/2010 10:53 AM                                                                                                                      

Subject:    Redline Comments on PC preamble                                                                                                          

Hi Keith,

Attached are redline comments on the PC preamble – these comments are in the  

(d)(4) section and the discussion of GHG regulations.

Please let me know if you have any questions.

Regards,

Cortney

(See attached file: RedlineComments_0805_PCPreamble.pdf)
Page 71 of 435

adverse health effects due to concurrent exposure to other HAPs 

with similar biological endpoints, from either the same or other 

source categories, where the concentration of the threshold 

pollutant emitted from the given source category is below the 

threshold; the potential impacts on ecosystems of releases of 

the pollutant; and reductions in criteria pollutant emissions 

and other co-benefits that would be achieved via the MACT 

standard – the decisive factor here. Each of these factors is 

directly relevant to the health and environmental outcomes at 

which section 112 of the Clean Air Act is fundamentally aimed. 

If EPA does determine that it is appropriate to set a standard 

based on a health threshold, we must develop emission standards 

that will ensure the public will not be exposed to levels of the 

pertinent HAP in excess of the health threshold, with an ample 

margin of safety. 

Since any emission standard under section 112(d)(4) must 

consider the established health threshold level, with an ample 

margin of safety, in this rulemaking EPA has considered the 

adverse health effects of the HAP acid gases, beginning with 

HCl. Research indicates that HCl is associated with chronic 

respiratory toxicity. In the case of HCl, this means that 

chronic inhalation of HCl can cause tissue damage in humans. 

Among other things, it is corrosive to mucous membranes and can 

cause damage to eyes, nose, throat, and the upper respiratory 
Page 72 of 435

tract as well as pulmonary edema, bronchitis, gastritis, and 

dermatitis. Considering this respiratory toxicity, EPA has 

established a chronic reference concentration (RfC) for the 

inhalation of HCl of 20 μg/m3. An RfC is defined as an estimate 

(with uncertainty spanning perhaps an order of magnitude) of a 

continuous inhalation exposure to the human population 

(including sensitive subgroups25) that is likely to be without an 

appreciable risk of deleterious effects during a lifetime. The 

development of the RfC for HCl reflected data only on its 

chronic respiratory toxicity. The IRIS health assessment 

evaluated chronic non-cancer risks and did not include an 

evaluation of carcinogenic effects (on which there are very 

limited studies). As a reference value for a single pollutant, 

RfCs do not reflect any potential cumulative or synergistic 

effects of an individual’s exposure to multiple HAPs or to a 

combination of HAPs and criteria pollutants. Similarly, an RfC 

evaluation does not focus on potential environmental impacts.

With respect to the potential health effects of HCl, we 

know the following: 

1. Chronic exposure to concentrations at or below the RfC 

is not expected to cause chronic respiratory effects; 

 

25 “Sensitive subgroups” may refer to particular life stages, 

such as children or the elderly, or to those with particular 

medical conditions, such as asthmatics.

Comment [A1]: Please provide 

citations (footnote is fine and 

link to IRIS file) 

Comment [A2]: Not sure this is true.

The RfC setting process looks at 

all the potential adverse effects 

and then picks the one of greatest 

concern (eg effects at lowest 

level) to protect against all 

effects. Thus suggest deleting this 

as the RfC is protective of all the 

endpoints. 

Comment [A3]: The RfC is for chronic 

effects, thus it wouldn’t include 

acute exposure. 

Deleted: It did not take into account 

effects associated with acute 

exposure, and, in this situation, t

Deleted: did not evaluate the 

potential carcinogenicity of HCl 

Deleted: the 

Deleted: also did not

Deleted: As the RfC calculation 

focused on health effects, it did 

not take into account the potential 

environmental impacts of HCl.
Page 73 of 435

2. Little research has been conducted on its 

carcinogenicity. The one occupational study of which 

we are aware found no evidence of carcinogenicity; 

3. There is a significant body of scientific literature 

addressing the health effects of acute exposure to HCl 

(California Office of Health Hazard Assessment, 2008. 

Acute Toxicity Summary for Hydrogen Chloride, 

http://www.oehha.ca.gov/air/hot_spots/2008/AppendixD2_

final.pdf#page=112 EPA, 2001). However, we currently 

lack information on the peak short-term emissions of 

HCl from cement kilns which might allow us to 

determine whether a chronic health-based emission 

standard for HCl would ensure that acute exposures 

will not pose health concerns. 

4. We are aware of no studies explicitly addressing the 

toxicity of mixtures of HCl with other respiratory 

irritants. However, many of the other HAPs (and 

criteria pollutants) emitted by cement kilns also are 

respiratory irritants, and in the absence of 

information on interactions, EPA assumes an additive 

cumulative effect (Supplementary Guidance for 

Conducting Health Risk Assessment of Chemical 

Mixtures. 

Comment [A4]: Do we know of any 

cases where the acute exposure 

level is less than the chronic 

level? Typically the chronic value 

is more protective than the acute 

value and we would expect the same 

here so if we actually consider the 

science we know that at a minimum 

the chronic value would be 

protective for acute exposures. In 

fact it would be a conservative 

value. Thus please revise using 

what we know about the exposure 

sciences and health effects. 
Page 74 of 435

http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=20

533). 

Cement kilns also emit other acid gases along with HCl, 

including chlorine (Cl2), HCN and hydrogen fluoride (HF), 

all of which are HAPs. Like HCl, these HAP gases have 

established chronic health thresholds below which they 

are not expected to pose any significant risk of chronic 

respiratory effects, have no evidence to suggest that 

they may pose carcinogenic effects, and have an 

established body of literature regarding acute 

respiratory health effects. They are also controlled 

during the process of controlling HCl emissions from 

cement kilns using a wet scrubber. As such, their health 

impacts must be taken into account when considering a 

health-based emission limit for HCl. 

In the 2006 final rule, EPA did not set any standard for 

HCl.26 The Agency reasoned that no further control was necessary 

for Portland cement emissions of HCl because HCl is a “health 

threshold pollutant” and human health is protected with an ample 

margin of safety at current HCl emission levels. 71 FR at 

 

26 Although the decision not to set a standard in 2006 was based 

on the authority of section 112(d)(4), we note that the statute 

in fact states: “the Administrator may consider such threshold 

level, with an ample margin of safety, when establishing 

emission standards under this subsection.” Section 112(d)(4), 

emphasis added.
Page 75 of 435

76527. Underlying this conclusion was EPA’s analysis of a 

tiered screening study of dispersion modeling of cement 

facilities’ worst-case and actual HCl emissions. This study was 

conducted by the Portland Cement Association for about twothirds of operating U.S. cement plants. Dispersion modeling 

results were evaluated against the RfC for HCl.27 The screening 

analysis involved making conservative assumptions regarding HCl 

emission concentrations and plants’ operating conditions 

(greater concentrations than known to be emitted and perpetual 

operation at maximum capacity). All plants in the analysis, 

with five exceptions, had HCl levels well below a Hazard 

Quotient (HQ) level of 1.0, the ratio of exposure (or modeled 

concentration) to the health reference value or threshold level. 

The remaining five plants in the analysis had HQ levels greater 

than 1.0 assuming maximum emissions, but less than 1.0 when 

their actual emissions were used in the dispersion models. Id. 

at 76528-29. 

At proposal of these amendments, recognizing that the 2006 

determination was deficient, if for no other reason because it 

failed to establish any emission standard whatever, EPA 

 

27 In the previous study EPA also evaluated dispersion modeling 

results against an acute exposure guideline level (AEGL) below 

which acute effects would not be expected to occur. However, 

even given the uncertainties mentioned for short term HCl 

emissions, that analysis indicated that chronic effects would be 

of the most concern.
Page 76 of 435

conducted its own analysis to determine what numerical standard 

for HCl would be necessary to at least assure that, for the 

sources in the controlled category or subcategory, persons 

exposed to emissions of HCl would not experience the adverse 

health effects on which the threshold is based. In order to 

determine this level, in the proposed rule we conducted a risk 

analysis of the same 68 facilities analyzed by PCA using a 

screening level dispersion model (AERSCREEN). Using site 

specific stack parameters and conservative meteorological 

conditions (taken from the PCA analysis), the AERSCREEN modeling 

predicted the highest long term ground level concentration 

surrounding each facility. The results of this analysis 

indicated that an HCl emission limit of 23 ppmv or less (an 

order of magnitude higher than the MACT standard) would result 

in no exceedances of the RfC for HCl for any of the facilities 

assessed.28 

Based on further consideration, EPA now believes that the 

2006 PCA study and analysis have several serious deficiencies. 

First of all, not all cement plants were evaluated (the PCA 

study covered about two thirds of the plants in the source 

category), and among those not evaluated were cement plants with 

 

28 Derivation of a Health-Based Stack Gas Concentration Limit for 

HCl in Support of the National Emission Standards for Hazardous 

Air Pollutants from the Portland Cement Manufacturing Industry, 

April 10, 2009.

Comment [A5]: Not sure what exactly 

constitutes a serious deficiency. 

Is the concern that the facilities 

are not representative of potential 

worst case. If so, please be more 

clear. 
Page 77 of 435

the most likelihood of posing risk at ground level from HCl 

emissions due to use of positive pressure baghouses with 

monovents or multiple short stacks. Secondly, the analysis did 

not consider the impacts of the co-emitted acid gases, an 

important consideration in determining an ample margin of 

safety. In addition, no data were provided, nor do we have 

data, on other pollutants in the vicinity of these cement 

facilities, or background concentration data for HCl to 

determine cumulative impacts of HCl emissions for these 

facilities.29 EPA’s analysis of 2009 could not improve on the 

PCA study, given the lack of robust emissions data for Cl2, HF, 

and HCN, and the lack of any additional data for the cement 

kilns not included in the original study. As a result, EPA 

cannot ensure that the resulting derivation of 23 ppmv as a 

possible health-based emission standard for HCl would result in 

chronic ambient levels of acid gases that would not pose 

significant health risks. EPA has not received any data since 

proposal that would allow us to extend that analysis to cover 

all acid gases and all facilities. 

 

29 It should be noted that large amounts of site-specific 

information both on kiln operation and local meteorological 

information is needed to obtain meaningful results from 

AERSCREEN and other dispersion models. This information is in 

the ready possession of the industrial sources themselves, but 

for unknown reasons, was not provided by industry to EPA either 

as part of the 2006 PCA analysis or in response to subsequent 

data solicitations by EPA.

Comment [A6]: Has EPA asked for 

this? 
Page 78 of 435

In addition to potential health impacts, EPA has evaluated 

the potential for environmental impacts when considering whether 

to exercise discretion under section 112(d)(4). When HCl gas 

encounters water in the atmosphere, it forms an acidic solution 

of HCl. In areas where the deposition of acids derived from 

emissions of sulfur and nitrogen oxides are causing aquatic 

and/or terrestrial acidification, with accompanying ecological 

impacts, the deposition of HCl could exacerbate these impacts. 

Being mindful of the explicit legislative history, and in 

keeping with past EPA practice, it is appropriate to consider 

potential adverse environmental effects in addition to adverse 

health effects when setting an emission standard for HCl under 

section 112(d)(4). The co-emissions of HF, HCN, and Cl2 from 

cement kilns could serve to further aggravate these 

environmental acidification impacts impacts but at this time EPA 

has no data to support this claim. 

Although the PCA analysis did not include an assessment of 

potential environmental effects, for the 2006 final Portland 

cement rule, EPA conducted its own analysis of potential effects 

of cement kilns’ HCl emissions to wildlife, aquatic life, and 

other natural resources. The Agency concluded at the time that 

acute and chronic exposures to expected HCl concentration around 

cement kilns are not expected to result in adverse environmental 
Page 125 of 435

73 FR at 34,084. These concerns were specifically related to 

the Prevention of Significant Deterioration and title V 

permitting programs and the unmanageable permitting burden that 

we anticipated would arise should GHGs become subject to these 

programs as a result of regulation under the Act. 

Since that time, we have issued regulations for GHG 

emissions under the CAA through the light duty vehicle rule (75 

FR 25324, (May 7, 2010)) and have finalized the greenhouse gas 

“tailoring” rule (75 FR 31514 (June 3, 2010)) and the Johnson 

memo Reconsideration (75 FR 17004 (April 2, 2010)). As a result 

of these actions, as of January 2, 2011, GHGs will become 

"subject to regulation" under the Act. Accordingly, the Agency 

has now finalized a framework addressing the concerns that were 

the basis of our decision not to propose standards of 

performance for GHG emissions from this industry at the time we 

proposed this 8-year review action. 

Today’s final rule does not include a standard of 

performance for GHG. There are two reasons for this. First, we 

did not propose such a standard. Promulgating such a standard 

without providing opportunity to comment on it would not be a 

logical outgrowth of the proposal and would, accordingly, 

violate the norms of notice and comment rulemaking. Second, we 

do not yet have adequate information about GHG emissions and 

control strategies for the Portland cement industry. This 

Comment [A7]: How does this 

statement comport with the 

statements below about emissions 

and that there are cost-effective 

GHG controls for cement kilns? 
Page 126 of 435

information forms the basis of standards of performance, which 

must take into account achievability and cost of such controls. 

This is not the end of the matter. To the contrary, based 

on our current knowledge we believe that it may be appropriate 

for the Agency to set a standard of performance for GHGs. We 

have historically declined to propose standards for a pollutant 

where it is emitting in low amounts or where we determined that 

a BDT analysis would result in no control. National Lime 

Assoc’n v. EPA, 627 F.2d at 426. Based on current information 

we do not believe such circumstances are present here. Without 

prejudging the outcome of a future regulatory process, we note 

the following considerations. 

First, Portland cement is one of the largest stationary 

source categories of GHG emissions, ranking as the third highest 

U.S. source of CO2 emissions. Second, based on our initial 

evaluation it appears that there are cost-effective control 

strategies for this source category that would provide an 

appropriate basis for establishing a standard of performance for 

GHG emissions. See 73 FR 44491, July 30, 2008. These control 

strategies include, for example, energy efficiency measures, 

reductions in cement clinker content, and raw materials 

substitution. There may be other cost-effective controls as 

well. 

Comment [A8]: Please explain what is meant by 

this? The FR notice points to a report titled “U.S. 

EPA (2008), Air Pollution Controls and 

Efficiency Improvement Measures for Cement Kiln. 

Final Report.” – where can the reader find this? 

Comment [A9]: Would these changes 

also reduce HAP?