Document ID: EPA-HQ-OAR-2007-0211-0001
Agency: epa
Document Type: Proposed Rule
Title: National Emission Standards for Hazardous Air Pollutant Emissions: Group I Polymers and Resins (Polysulfide Rubber Production, Ethylene Propylene Rubber Production, Butyl Rubber Production, Neoprene Production); National Emission Standards for Hazardous Air Pollutants for Epoxy Resins Production and Non-Nylon Polyamides Production; National Emission Standards for Hazardous Air Pollutants for Sourc
Posted Date: 2007-12-12T05:00Z

[Federal Register: December 12, 2007 (Volume 72, Number 238)]
[Proposed Rules]               
[Page 70543-70558]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr12de07-13]                         

[[Page 70543]]

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2007-0211; FRL-8505-1]
RIN 2060-AO16

 
National Emission Standards for Hazardous Air Pollutant 
Emissions: Group I Polymers and Resins (Polysulfide Rubber Production, 
Ethylene Propylene Rubber Production, Butyl Rubber Production, Neoprene 
Production); National Emission Standards for Hazardous Air Pollutants 
for Epoxy Resins Production and Non-Nylon Polyamides Production; 
National Emission Standards for Hazardous Air Pollutants for Source 
Categories: Generic Maximum Achievable Control Technology Standards 
(Acetal Resins Production and Hydrogen Fluoride Production)

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

-----------------------------------------------------------------------

SUMMARY: This proposed rule requests public comment on the residual 
risk and technology reviews for eight industrial source categories 
regulated by four national emission standards for hazardous air 
pollutants (HAP). The eight industrial source categories and the four 
national emission standards are listed in Table 3 of this preamble. The 
underlying national emission standards that are under review in this 
action limit and control HAP.
    We are proposing that no revisions to the national emission 
standards regulating the eight source categories listed in Table 3 of 
this preamble are required at this time under section 112(f)(2) or 
112(d)(6) of the Clean Air Act.

DATES: Comments. Comments must be received on or before February 11, 
2008.
    Public Hearing. If anyone contacts EPA requesting to speak at a 
public hearing by December 27, 2007, a public hearing will be held on 
January 11, 2008.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
OAR-2007-0211, by one of the following methods:
     http://www.regulations.gov. Follow the on-line instructions for 

submitting comments.
     E-mail: a-and-r-Docket@epa.gov.
     Fax: (202) 566-1741.
     Mail: U.S. Postal Service, send comments to: EPA Docket 
Center (2822T), Docket ID No. EPA-HQ-OAR-2007-0211, 1200 Pennsylvania 
Avenue, NW., Washington, DC 20460. Please include a total of two 
copies.
     Hand Delivery: In person or by courier, deliver comments 
to: EPA Docket Center (2822T), EPA West Building, Room 3334, 1301 
Constitution Ave., NW., Washington, DC 20004. Such deliveries are only 
accepted during the Docket's normal hours of operation, and special 
arrangements should be made for deliveries of boxed information. Please 
include a total of two copies.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-
2007-0211. If commenting on the data in the Risk and Technology Review 
(RTR) database, please format your comments as described in section III 
and IV of this preamble. EPA's policy is that all comments received 
will be included in the public docket without change and may be made 
available online at http://www.regulations.gov, including any personal 

information provided, unless the comment includes information claimed 
to be confidential business information (CBI) or other information 
whose disclosure is restricted by statute. Do not submit information 
that you consider to be CBI or otherwise protected through 
http://www.regulations.gov or e-mail. The www.regulations.gov Web site is an 

``anonymous access'' system, which means EPA will not know your 
identity or contact information unless you provide it in the body of 
your comment. If you send an e-mail comment directly to EPA without 
going through http://www.regulations.gov, your e-mail address will be 

automatically captured and included as part of the comment that is 
placed in the public docket and made available on the Internet. If you 
submit an electronic comment, EPA recommends that you include your name 
and other contact information in the body of your comment and with any 
disk or CD-ROM you submit. If EPA cannot read your comment due to 
technical difficulties and cannot contact you for clarification, EPA 
may not be able to consider your comment. Electronic files should avoid 
the use of special characters, any form of encryption, and be free of 
any defects or viruses. For additional information about EPA's public 
docket visit the EPA Docket Center homepage at http://www.epa.gov/epahome/dockets.htm
.

    Docket: All documents in the docket are listed in the 
http://www.regulations.gov index. Although listed in the index, some 

information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, will be publicly available only in hard copy. 
Publicly available docket materials are available either electronically 
in http://www.regulations.gov or in hard copy at the EPA Docket Center, Docket 

ID No. EPA-HQ-OAR-2007-0211, EPA West Building, Room 3334, 1301 
Constitution Avenue, NW., Washington, DC. The Public Reading Room is 
open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding 
legal holidays. The telephone number for the Public Reading Room is 
(202) 566-1744, and the telephone number for the EPA Docket Center is 
(202) 566-1742.

FOR FURTHER INFORMATION CONTACT: For questions about this proposed 
action, contact Ms. Mary Tom Kissell, Office of Air Quality Planning 
and Standards, Sector Policies and Programs Division, Coatings and 
Chemicals Group (E143-01), U.S. Environmental Protection Agency, 
Research Triangle Park, NC 27711; telephone number: (919) 541-4516; fax 
number: (919) 685-3219; and e-mail address: kissell.mary@epa.gov. For 
specific information regarding the modeling methodology, contact Ms. 
Elaine Manning, Office and Air Quality Planning and Standards, Health 
and Environmental Impacts Division, Sector Based Assessment Group 
(C539-02), U.S. Environmental Protection Agency, Research Triangle 
Park, NC 27711; telephone number: (919) 541-5499; fax number: (919) 
541-0840; and e-mail address: manning.elaine@epa.gov. For information 
about the applicability of these four national emission standards for 
hazardous air pollutants (NESHAP) to a particular entity, contact the 
appropriate person listed in Table 1 to this preamble.

Table 1.--List of EPA Contacts for Group I Polymers and Resins, Group II
  Polymers and Resins, Acetal Resins Production, and Hydrogen Fluoride
                               Production
------------------------------------------------------------------------
         NESHAP for:            OECA Contact \1\      OAQPS Contact \2\
------------------------------------------------------------------------
Polymers and Resins, Group I  Scott Throwe (202)    David Markwordt
                               564-7013,             (919) 541-0837,
                               throwe.scott@epa.go   markwordt.david@epa

                               v.                    .gov.

[[Page 70544]]

Polymers and Resins, Group    Scott Throwe (202)    Randy McDonald (919)
 II.                           564-7013,             541-5402,
                               throwe.scott@epa.go  mcdonald.randy@epa.

                               v.                    ov.
Acetal Resins Production....  Marcia Mia (202) 564- David Markwordt
                               7042,                 (919) 541-0837,
                               mia.marcia@epa.gov  markwordt.david@epa..

                                                     gov.
Hydrogen Fluoride Production  Marcia Mia (202) 564- Bill Neuffer (919)
                               7042,                 541-5435,
                               mia.marcia@epa.gov   Neuffer.bill@epa.go.

                                                     v.
------------------------------------------------------------------------
\1\ OECA stands for the EPA's Office of Enforcement and Compliance
  Assurance.
\2\ OAQPS stands for EPA's Office of Air Quality Planning and Standards.

SUPPLEMENTARY INFORMATION: Regulated Entities. The eight regulated 
industrial source categories that are the subject of today's proposal 
are listed in Table 2 to this preamble. Table 2 is not intended to be 
exhaustive, but rather provides a guide for readers regarding entities 
likely to be affected by the proposed action for the source categories 
listed. These standards, and any changes considered in this rulemaking, 
would be directly applicable to sources as a Federal program. Thus, 
Federal, State, local, and tribal government entities are not affected 
by this proposed rule. The regulated categories affected by this action 
include:

         Table 2.--NESHAP for Eight Industrial Source Categories
------------------------------------------------------------------------
                Category                  NAICS \1\ Code   MACT \2\ Code
------------------------------------------------------------------------
Butyl Rubber Production.................          325212            1307
Ethylene-Propylene Rubber Production....          325212            1313
Polysulfide Rubber Production...........          325212            1332
Neoprene Production.....................          325212            1320
Epoxy Resins Production.................          325211            1312
Non-nylon Polyamides Production.........          325211            1322
Acetal Resins Production................          325211            1301
Hydrogen Fluoride Production............          325120            1409
------------------------------------------------------------------------
\1\ North American Industry Classification System.
\2\ Maximum Achievable Control Technology.

    To determine whether your facility would be affected, you should 
examine the applicability criteria in the appropriate NESHAP. If you 
have any questions regarding the applicability of any of these NESHAP, 
please contact the appropriate person listed in Table 1 of this 
preamble in the preceding FOR FURTHER INFORMATION CONTACT section.
    Submitting Comments/CBI. Direct your comments to Docket ID No. EPA-
HQ-OAR-2007-0211. If commenting on changes to the RTR database, please 
submit your comments in the format described in sections III and IV of 
this preamble. Do not submit CBI to EPA through http://www.regulations.gov or 

e-mail. Instead, send or deliver information identified as CBI only to 
the following address: Mr. Roberto Morales, OAQPS Document Control 
Officer (C404-02), U.S. Environmental Protection Agency, Office of Air 
Quality Planning and Standards, Research Triangle Park, NC 27711, 
Attention Docket ID No. EPA-HQ-OAR-2007-0211. Clearly mark the part or 
all of the information that you claim to be CBI. For CBI information on 
a disk or CD-ROM that you mail to Mr. Morales, mark the outside of the 
disk or CD-ROM as CBI and then identify electronically within the disk 
or CD-ROM the specific information that is claimed as CBI.
    In addition to one complete version of the comment that includes 
information claimed as CBI, a copy of the comment that does not contain 
the information claimed as CBI must be submitted for inclusion in the 
public docket. If you submit a CD-ROM or disc that does not contain 
CBI, mark the outside of the disk or CD-ROM clearly that it does not 
contain CBI. Information not marked as CBI will be included in the 
public docket and EPA's electronic public docket without prior notice.
    If you have any questions about CBI or the procedures for claiming 
CBI, please consult the person identified in the FOR FURTHER 
INFORMATION CONTACT section. Information marked as CBI will not be 
disclosed except in accordance with procedures set forth in 40 CFR part 
2.
    Worldwide Web (WWW). In addition to being available in the docket, 
an electronic copy of today's proposed action will also be available on 
the WWW through the Technology Transfer Network (TTN). Following 
signature, a copy of the proposed action will be posted on the TTN(s 
policy and guidance page for newly proposed or promulgated rules at the 
following address: http://www.epa.gov/ttn/oarpg/. The TTN provides 

information and technology exchange in various areas of air pollution 
control.
    As discussed in more detail in sections III and IV of this 
preamble, additional information is available on the Risk and 
Technology Review Phase II webpage at http://www.epa.gov/ttn/atw/rrisk/rtrpg.html.
 This information includes source category descriptions and 

detailed emissions and other data that were used as inputs to the risk 
assessments.
    Public Hearing. If a public hearing is held, it will begin at 10 
a.m. and will be held at EPA's campus in Research Triangle Park, North 
Carolina, or at an alternate facility nearby. Persons interested in 
presenting oral testimony or inquiring as to whether a public hearing 
is to be held should contact Ms. Mary Tom Kissell, Office of Air 
Quality Planning and Standards, Sector Policies and Programs Division, 
Coatings and Chemicals Group (E143-01), U.S. Environmental Protection 
Agency, Research Triangle Park, NC 27711; telephone number: (919) 541-
4516.
    Outline. The information presented in this preamble is organized as 
follows:

I. Background

[[Page 70545]]

    A. What is the statutory authority for this action?
    B. Overview of the Four NESHAP
    C. How did we estimate risk posed by the eight source 
categories?
    D. What are the conclusions of the risk review?
    E. What are the conclusions of the technology review?
II. Proposed Action
III. How do I access and review the facility-specific data?
IV. How do I submit suggested data corrections?
V. Statutory and Executive Order Reviews
    A. Executive Order 12866, Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132, Federalism
    F. Executive Order 13175, Consultation and Coordination With 
Indian Tribal Governments
    G. Executive Order 13045, Protection of Children From 
Environmental Health Risks and Safety Risks
    H. Executive Order 13211, Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act
    J. Executive Order 12898, Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations

I. Background

A. What is the statutory authority for this action?

    Section 112 of the Clean Air Act (CAA) establishes a comprehensive 
regulatory process to address emissions of hazardous air pollutants 
(HAP) from stationary sources. In accordance with CAA section 112(c), 
EPA identifies categories and subcategories of major sources that emit 
one or more of the HAP listed in CAA section 112(b). CAA section 112(d) 
then calls for EPA to promulgate national technology-based emission 
standards for each listed category or subcategory of sources. For 
``major sources'' that emit or have the potential to emit any single 
HAP at a rate of 10 tons or more per year or any combination of HAP at 
a rate of 25 tons or more per year, these technology-based standards 
must reflect the maximum reductions of HAP achievable (after 
considering cost, energy requirements, and non-air health and 
environmental impacts) and are commonly referred to as maximum 
achievable control technology (MACT) standards. The source categories 
listed in Table 3 to this preamble are eight source categories for 
which we have promulgated MACT standards.
    In what we refer to as the technology review, CAA section 112(d)(6) 
then requires EPA to review the CAA section 112(d) technology-based 
standards and to revise them ``as necessary, taking into account 
developments in practices, processes, and control technologies,'' no 
less frequently than every 8 years. If we conclude a revision is 
necessary, we must revise the standards.
    The residual risk review is described in section 112(f) of the CAA. 
CAA section 112(f)(2) requires us to promulgate standards for each 
category or subcategory of CAA section 112(d) sources ``if promulgation 
of such standards is required in order to provide an ample margin of 
safety to protect public health * * * or to prevent, taking into 
consideration costs, energy, safety, and other relevant factors, an 
adverse environmental effect.\1\ If standards promulgated pursuant to 
CAA section 112(d) and applicable to a category or subcategory of 
source emitting a pollutant (or pollutants) classified as a known, 
probable or possible human carcinogen do not reduce lifetime excess 
cancer risks to the individual most exposed to emissions from a source 
in the category or subcategory to less than 1-in-1 million, the 
Administrator shall promulgate standards under this subsection'' for 
the source category (or subcategory). EPA's framework for making ample 
margin of safety determinations under CAA section 112(f)(2) is provided 
in the Benzene NESHAP (54 FR 38044, September 14, 1989) and was 
codified by Congress in CAA section 112(f)(2)(B).
---------------------------------------------------------------------------

    \1\ Adverse environmental effect is defined in CAA section 
112(a)(7) as any significant and widespread adverse effect, which 
may reasonably be anticipated, to wildlife, aquatic life, or other 
natural resources, including adverse impacts on populations of 
endangered or threatened species or significant degradation of 
environmental quality over broad areas.
---------------------------------------------------------------------------

B. Overview of the Four NESHAP

    The eight industrial source categories and four NESHAP that are the 
subject of today's proposal are listed in Table 3 to this preamble. 
NESHAP limit and control HAP that are known or suspected to cause 
cancer or have other serious human health or environmental effects. The 
NESHAP for these eight source categories generally required 
implementation of technologies such as steam strippers and 
incineration.

    Table 3.--List of National Emission Standards for Hazardous Air Pollutants (NESHAP) and Industrial Source
                                     Categories Affected by Today's Proposal
----------------------------------------------------------------------------------------------------------------
                                    Source categories
         Title of NESHAP           affected by today's    Promulgated rule     Compliance     NESHAP as referred
                                         proposal            reference            date       to in this preamble
----------------------------------------------------------------------------------------------------------------
NESHAP for Group I Polymers and    Polysulfide Rubber   61 FR 46905 (09/05/      07/31/1997  Polymers and Resins
 Resins\1\.                         Production.          1996).                               I.
                                   Ethylene Propylene
                                    Rubber Production.
                                   Butyl Rubber
                                    Production.
                                   Neoprene Production
NESHAP for Epoxy Resins            Epoxy Resins         60 FR 12670 (03/08/      03/03/1998  Polymers and Resins
 Production and Non-nylon           Production.          1995).                               II.
 Polyamides Production.            Non-nylon
                                    Polyamides
                                    Production..
NESHAP for GMACT\2\..............  Acetal Resins        64 FR 34853 (06/29/      06/29/2002  GMACT.
                                    Production.          1999).
                                   Hydrogen Fluoride
                                    Production..
----------------------------------------------------------------------------------------------------------------
\1\ The Polymers and Resins I NESHAP regulates nine source categories. We are performing the residual risk and
  technology review for four of them in this proposal. We will address the remaining five source categories in a
  separate risk and technology review rulemaking.
\2\ The source categories subject to the standards in the GMACT NESHAP are Acetal Resins Production and Hydrogen
  Fluoride Production.

[[Page 70546]]

1. Polymers and Resins I
    The Polymers and Resins I NESHAP applies to major sources and 
regulates HAP emissions from nine source categories. In today's 
proposal, we address four of the Polymer and Resins I sources 
categories--Polysulfide Rubber Production, Ethylene Propylene Rubber 
Production, Butyl Rubber Production, and Neoprene Production. HAP 
emissions from these processes can be released from storage tanks, 
process vents, equipment leaks, and wastewater operations.
    These four source categories involve the production of elastomers 
(i.e., synthetic rubber). An elastomer is a synthetic polymeric 
material that can stretch at least twice its original length and then 
return rapidly to approximately its original length when released. 
Elastomers have long, flexible, chainlike molecules that are able to 
undergo rapid rotation (i.e., flex) as a result of thermal agitation. 
Elastomers are produced via a polymerization process, in which monomers 
undergo intermolecular chemical bonds to form an insoluble, three-
dimensional network (i.e., a polymer). Generally, the production of 
elastomers entails four processes: (1) Raw material (i.e., solvent) 
storage and refining; (2) polymer formation in a reactor (either via 
the solution process, where monomers are dissolved in an organic 
solvent, or the emulsion process, where monomers are dispersed in water 
using a soap solution); (3) stripping and material recovery; and (4) 
finishing (i.e., blending, aging, coagulation, washing, and drying 
processes).
    a. Polysulfide Rubber Production. Polysulfide rubber is a synthetic 
rubber produced by the reaction of sodium sulfide and p-dichlorobenzene 
(1,4-dichlorobenzene) at an elevated temperature in a polar solvent. 
Polysulfide rubber is resilient, resistant to solvents, and has low 
temperature flexibility, facilitating its use in seals, caulks, 
automotive parts, rubber molds for casting sculpture, and other 
products.
    During the development of the NESHAP, we identified one polysulfide 
rubber production facility as a major source and subject to the 
Polymers and Resins I NESHAP. This facility consisted of raw material 
storage vessels and was designated as a major source because it was co-
located with another source. This polysulfide facility has been 
dismantled and we are not aware of any other facilities currently 
subject to the NESHAP. (Even though no polysulfide rubber facilities 
are currently in operation, we completed a risk analysis based on the 
available information on this facility as of 2002.) The only HAP 
reported for this category in the 2002 National Emissions Inventory 
(NEI) was methylene diphenyl diisocyanate.
    b. Ethylene Propylene Rubber Production. Ethylene propylene 
elastomer is an elastomer prepared from ethylene and propylene 
monomers. Common uses for these elastomers include radiator and heater 
hoses, weather stripping, door and window seals for cars, construction 
plastics blending, wire and cable insulation and jackets, and single-
ply roofing membranes.
    We believe five ethylene propylene rubber production facilities are 
currently subject to the Polymers and Resins I NESHAP. Hexane, which is 
the HAP used as the solvent at three of the plants, accounts for the 
majority of the HAP emissions from these facilities (over 95 percent of 
the total HAP emissions by mass). These facilities also reported 
relatively small emissions of ethyl chloride, ethylene glycol, and 
hydrogen chloride. Two facilities do not use hexane in their processes. 
One facility uses toluene instead of hexane as a solvent and the other 
facility uses a gas-phase process where methanol is the only HAP 
emitted.
    c. Butyl Rubber Production. The Butyl Rubber Production source 
category includes any facility that manufactures copolymers of 
isobutylene and isoprene. Butyl rubber is very impermeable to common 
gases and resists oxidation. A specialty group of butyl rubbers are 
halogenated butyl rubbers, which are produced commercially by 
dissolving butyl rubber in hydrocarbon solvent and contacting the 
solution with gaseous or liquid elemental halogens such as chlorine or 
bromine. Halogenated butyl rubber resists aging to a higher degree than 
the nonhalogenated type and is more compatible with other types of 
rubber. Uses for butyl rubber include tires, tubes, and tire products; 
automotive mechanical goods; adhesives, caulks, and sealants; and 
pharmaceutical uses.
    We believe two butyl rubber production facilities are currently 
subject to the Polymers and Resins I NESHAP. The primary HAP emitted 
from butyl rubber production facilities are methyl chloride (53 percent 
of the total HAP emissions by mass) and hydrochloric acid (34 percent). 
Hexane is also emitted from the production of halobutyl rubber, and it 
makes up around 13 percent of the total HAP emissions from the 
category.
    d. Neoprene Production. Neoprene is a polymer of chloroprene. 
Neoprene was originally developed as an oil-resistant substitute for 
natural rubber, and its properties allow its use in a wide variety of 
applications including wetsuits, gaskets and seals, hoses and tubing, 
plumbing fixtures, adhesives, and other products.
    We believe that one neoprene production facility is currently 
subject to the Polymers and Resins I NESHAP. The primary HAP emitted by 
production are chloroprene and toluene, with chloroprene accounting for 
over 80 percent of the total emissions.
2. Polymers and Resins II
    The Polymers and Resins II NESHAP applies to major sources and 
regulates HAP emissions from two source categories--epoxy resins 
production and non-nylon polyamides production. HAP emissions from 
these source categories can be released from storage tanks, process 
vents, equipment leaks, and wastewater operations.
    a. Epoxy Resins Production. The Epoxy Resins Production source 
category generates HAP emissions from the manufacture of basic liquid 
epoxy resins used in the production of glues, adhesives, plastic parts, 
and surface coatings. This source category does not include specialty 
or modified epoxy resins.
    We believe three epoxy resins production facilities are currently 
subject to the Polymers and Resins II NESHAP. The HAP emitted in the 
greatest quantity by mass from these facilities are epichlorohydrin 
(referred to by its synonym 1-chloro-2,3-epoxypropane in the NEI and in 
the accompanying emissions summary table) and chlorobenzene. The total 
emissions for these two HAP account for approximately 87 percent of the 
total HAP mass emitted by the facilities regulated by the NESHAP. 
Epichlorohydrin is emitted in the greatest quantity and is reported as 
an emission of all three facilities. Other HAP such as phenol, xylenes, 
ethyl benzene, propylene dichloride, allyl chloride, 1,3-
dichloropropene, glycol ethers, methyl chloride, toluene, acrolein, 
benzyl chloride, and ethyl acrylate are emitted in smaller quantities. 
All the other HAP are reported as emissions by only one or two of the 
facilities.
    b. Non-nylon Polyamides Production. The Non-nylon Polyamides 
Production source category generates HAP emissions from the manufacture 
of epichlorohydrin cross-linked non-nylon polyamides used primarily by 
the paper industry as an additive to paper products. Natural polymers, 
such as those contained in paper products, have

[[Page 70547]]

little cross-linking, which allows their fibers to change position or 
separate completely when in contact with water. The addition of 
epichlorohydrin cross-linked non-nylon polyamides to these polymers 
causes the formation of a stable polymeric web among the natural 
fibers. Because the polymeric web holds the fibers in place even in the 
presence of water, epichlorohydrin cross-linked non-nylon polyamides 
are also referred to as wet-strength resins.
    We believe four non-nylon polyamides production facilities are 
currently subject to the Polymers and Resins II NESHAP. Epichlorohydrin 
(64 percent) and hydrochloric acid (36 percent) are the only HAP 
emitted from this category.
3. GMACT--Acetal Resins Production
    The GMACT set national emission standards for certain source 
categories consisting of five or fewer facilities. The basic purpose of 
the GMACT approach was to use public and private sector resources 
efficiently, and to promote regulatory consistency and predictability 
in the MACT standards development.
    Emission sources from acetal resin production include storage 
vessels that hold process feed materials, process vents, process 
wastewater treatment systems, and equipment leaks from compressors, 
agitators, pressure relief devices, sampling connection systems, 
valves, connectors, and instrumentation systems. The storage vessels 
associated with acetal resin production are primarily used for storage 
of solvents. Back end process vent emissions occur from reactor units, 
mixing vessels, solvent recovery operations, and other operations.
    Acetal resins are characterized by the use of formaldehyde in the 
polymerization process to manufacture homopolymers or copolymers of 
alternating oxymethylene units. Acetal resins, also known as 
polyoxymethylenes, polyacetals, or aldehyde resins, are a type of 
plastic possessing relatively high strength and rigidity without being 
brittle. They have good frictional properties and are resistant to 
moisture, heat, fatigue, and solvents. Acetal resins are used as parts 
in a variety of industrial applications, e.g., gears, bearings, 
bushings, and various other moving parts in appliances and machines, 
and in a range of consumer products, e.g., automotive door handles, 
seat belt components, plumbing fixtures, shaver cartridges, zippers, 
and gas tank caps.
    We believe three facilities are currently subject to the acetal 
resins production provisions in the GMACT. The primary HAP emitted by 
acetal resin production are formaldehyde and methanol, which make up 92 
percent of the total HAP emissions by mass.
4. GMACT--Hydrogen Fluoride Production
    The Hydrogen Fluoride Production source category includes any 
facility engaged in the production and recovery of hydrogen fluoride by 
reacting calcium fluoride with sulfuric acid. Potential sources of HAP 
emissions at hydrogen fluoride production facilities include: Process 
vents on hydrogen fluoride recovery and refining equipment, storage 
vessels used to store hydrogen fluoride, bulk loading of tank trucks 
and tank rail cars, leaks from hydrogen fluoride handling equipment, 
and reaction kiln seal leaks. The only HAP emitted from the processes 
in this source category is hydrogen fluoride. We believe two facilities 
are currently subject to the hydrogen fluoride production provisions in 
the GMACT.

C. How did we estimate risk posed by the eight source categories?

    To support the proposed decisions presented in today's notice, EPA 
conducted an inhalation risk assessment \2\ that provided estimates of 
maximum individual cancer risk, cancer risk distribution within the 
exposed populations, cancer incidence, hazard indices for chronic 
exposures to HAP with non-cancer health effects, and hazard quotients 
(HQ) for acute exposures to HAP with non-cancer health effects. The 
risk assessment consisted of six primary activities: (1) Establishing 
the nature and magnitude of emissions from the sources of interest, (2) 
identifying the emissions release characteristics (e.g., stack 
parameters), (3) conducting dispersion modeling to estimate the 
concentrations of HAP in ambient air, (4) estimating long-term and 
short-term inhalation exposures to individuals residing within 50 km of 
the modeled sources, (5) estimating individual and population-level 
risks using the exposure estimates and quantitative dose-response 
information, and (6) characterizing risk. In general the risk 
assessment followed a tiered, iterative approach, beginning with a 
conservative screening-level analysis and, where the screening analysis 
indicated the potential for non-negligible risks, following that with 
more refined analyses. The following sections summarize the results of 
these efforts.
---------------------------------------------------------------------------

    \2\ For more information on the risk assessment inputs and 
models, see ``Residual Risk Assessment for Eight Source 
Categories,'' available in the docket.
---------------------------------------------------------------------------

1. Emissions Data
    For the Ethylene Propylene Rubber Production, Butyl Rubber 
Production, Neoprene Production, Epoxy Resins Production, and Non-nylon 
Polyamides Production source categories, we relied primarily on 
emissions data and emissions release characteristic data we collected 
directly from industry. We reviewed these data and consider them to be 
the best emissions and emissions release characteristic data available 
for these five source categories.
    For the remaining three source categories, Polysulfide Rubber 
Production, Acetal Resins Production, and Hydrogen Fluoride Production, 
we relied primarily on data in the 2002 NEI Final Inventory,\3\ Version 
1 (made publicly available on February 26, 2006). For the Polysulfide 
Rubber source category, the data in the 2002 NEI were used without 
further investigation because the only facility in the source category 
closed in 2002. For the Acetal Resins and Hydrogen Fluoride source 
categories, the 2002 NEI data were supplemented with information from 
industry and, for one hydrogen fluoride facility, with information from 
the State permitting agency.
---------------------------------------------------------------------------

    \3\ The National Emission Inventory (NEI) is a database that 
contains information about sources that emit criteria air pollutants 
and their precursors, and HAP. The database includes estimates of 
annual air pollutant emissions from point, nonpoint, and mobile 
sources in the 50 States, the District of Columbia, Puerto Rico, and 
the Virgin Islands. EPA collects this information and releases an 
updated version of the NEI database every 3 years.
---------------------------------------------------------------------------

    In response to an advanced notice of proposed rulemaking \4\ we 
published on March 29, 2007, we received comments on emissions data and 
emissions release characteristics data for an acetal resins production 
facility, two ethylene propylene production facilities, and a neoprene 
production facility. We will include these comments in the docket for 
this proposal (docket ID EPA-HQ-OAR-2007-0211) and will evaluate them 
with other comments we receive in response to today's proposal. The 
data files for the eight source categories, which are posted on the RTR 
webpage and are described in Section III of this preamble, will include 
the new data provided by the commenters.
---------------------------------------------------------------------------

    \4\ Risk and Technology Review, Phase II, Group 2 at 72 FR 
29287.
---------------------------------------------------------------------------

    Emissions data and emissions release characteristics data for these 
eight source categories are documented in the docket in ``Documentation 
of Emissions Data and Emissions Release

[[Page 70548]]

Characteristics Data Used for the RTR Group 1.'' We specifically 
request comment on whether the facilities listed in our emissions data 
set accurately reflect the universe of sources within the source 
categories. For example, are there records remaining in the data set 
that are not part of the relevant source category or any missing 
emissions data that should be included for the relevant source 
category?
2. Risk Assessment
    Both long-term and short-term inhalation exposure concentrations 
and health risk from each of the eight source categories addressed in 
today's proposal were estimated using the Human Exposure Model 
(Community and Sector HEM-3 version 1.1.0). The HEM-3 model performs 
three main operations: Dispersion modeling, estimation of population 
exposure, and estimation of human health risks. The dispersion model 
used by HEM-3 is AERMOD, which is one of EPA's preferred models for 
assessing pollutant concentrations from industrial facilities.\5\
---------------------------------------------------------------------------

    \5\ Environmental Protection Agency. Revision to the Guideline 
on Air Quality Models: Adoption of a Preferred General Purpose (Flat 
and Complex Terrain) Dispersion Model and Other Revisions (70 FR 
68218). November 9, 2005.
---------------------------------------------------------------------------

    To perform the dispersion modeling and to develop the preliminary 
risk estimates, HEM-3 draws on three data libraries. The first is a 
library of meteorological data, which are used for dispersion 
calculations. This library includes 1 year of hourly surface and upper 
air observations for 130 meteorological stations, selected to provide 
thorough coverage of the U.S. and Puerto Rico. A second library of U.S. 
Census Bureau census block internal point locations and populations 
provides the basis of human exposure calculations (Census, 2000). In 
addition, the census library includes the elevation and controlling 
hill height for each census block, which are also used in dispersion 
calculations. A third library of pollutant unit risk factors and other 
health benchmarks is used to estimate health risks. These risk factors 
and health benchmarks are the latest values recommended by EPA for HAP 
and other toxic air pollutants, and are discussed in more detail below. 
These values are available at http://www.epa.gov/ttn/atw/toxsource/summary.html
.

    The risk assessment for chronic exposures used the estimated annual 
average ambient air concentration of each HAP emitted by each source 
for which we have emissions data in the source category at each nearby 
census block \6\ centroid as a surrogate for the chronic inhalation 
exposure concentration for all the people who reside in that census 
block. We calculated the maximum individual risk for each facility as 
the risk associated with a lifetime (70-year) exposure to the maximum 
concentration at the centroid of an inhabited census block. Individual 
cancer risks were calculated as the lifetime exposure to the ambient 
concentration of each HAP multiplied by its Unit Risk Estimate (URE); 
total cancer risks were the sum of the risks of each carcinogenic HAP 
(including known, probable, and possible carcinogens) emitted by the 
modeled source. Air concentrations of HAP from sources other than the 
modeled source were not estimated. Total cancer incidence and the 
distribution of individual cancer risks across the population within 50 
kilometers of any source were also estimated as part of these 
assessments by summing individual risks. We are using 50 kilometers to 
be consistent with both the analysis supporting the 1989 Benzene NESHAP 
(54 FR 38044) and the limitations of Gaussian dispersion modeling.
---------------------------------------------------------------------------

    \6\ A typical census block is comprised of approximately 40 
people or about 10 households.
---------------------------------------------------------------------------

    To assess risk of noncancer health effects from chronic exposures, 
we summed the HQ for each HAP that affects a common target organ system 
to obtain the hazard index (HI) for that target organ system (or target 
organ-specific hazard index, TOSHI), where the HQ is the estimated 
exposure divided by the chronic reference level (e.g., the U.S. EPA 
Reference Concentration (RfC) which is provided through the Integrated 
Risk Information System (IRIS)).
    Health protective screening estimates of acute exposures and risks 
were also evaluated for each HAP at any location off-site of each 
facility (i.e., not just the census block centroids) assuming the 
combination of a peak (hourly) emission rate and hourly dispersion 
conditions for the 1991 calendar year that would tend to maximize 
exposure. In each case, acute HQ were calculated using best available 
short-term health indices. We assumed that 10 times the average annual 
hourly emission rate represented a health protective emissions estimate 
to evaluate acute exposures and risks for these initial screens. The 
factor of 10 is intended to cover routinely variable emissions and 
startup, shutdown, and malfunction emissions. We chose to use a factor 
of 10 based on: (1) Engineering judgment, and (2) a review of short-
term emissions data that compared hourly and annual emissions data for 
volatile organic compounds for all facilities in a heavily-
industrialized 4-county area (Harris, Galveston, Chambers, and Brazoria 
Counties, TX) over an 11-month time period in 2001.\7\ Most peak 
emission events were less than twice the annual average hourly emission 
rate and the highest peak emission event was 8.5 times the annual 
average hourly emission rate. We request comment on the interpretation 
of these data and the appropriateness of using a factor of 10 times the 
average annual hourly emission rate in these acute exposure screening 
assessments.
---------------------------------------------------------------------------

    \7\ See http://www.tceq.state.tx.us/compliance/field_ops/eer/index.html
 or docket to access the source of these data.

---------------------------------------------------------------------------

    In cases where acute HQ values from the screening step were less 
than or equal to one, acute impacts were deemed negligible and no 
further analysis was performed. In the cases where an acute HQ from the 
screening step was greater than one, site-specific data were sought to 
develop a more refined estimate of the potential for acute impacts of 
concern. These data refinements included using a better representation 
of the peak-to-mean hourly emissions ratio (instead of using the 
default factor of 10) and using the site-specific facility layout to 
distinguish facility property from an area where the public could be 
exposed. The screening analysis resulted in an HQ less than or equal to 
one for all of the source categories except Acetal Resins Production 
and Hydrogen Fluoride Production. The specific refinements used for 
acetal resins production and hydrogen fluoride production are described 
in the results section for the two source categories.
    We engaged in a consultation with a panel from the Science Advisory 
Board (SAB) on the ``Risk and Technology Review (RTR) Assessment Plan'' 
in December of 2006. The results of this consultation were transmitted 
to us in June 2007 in a letter from the SAB which also contained a 
summary listing of the key messages from the panel. The letter is 
available from the docket and from http://www.epa.gov/sab/pdf/sab-07-003_response_04-20-07.pdf.
 In developing the risk assessments for the 

eight source categories covered by this proposal, we followed the RTR 
Assessment Plan, addressing the key recommendations from the panel, 
where appropriate and relevant to these assessments, but not the 
individual recommendations from each panel member. Our responses to 
each of the SAB's key recommendations are summarized in an appendix to 
the

[[Page 70549]]

``Residual Risk Assessment for Eight Source Categories,'' available in 
the docket.
3. Noncancer Inhalation Reference Values
    The most appropriate noncancer inhalation reference values for 
chronic durations in the Residual Risk Program are in order of 
preference: (1) The RfC which is provided through the IRIS; (2) the 
Agency for Toxic Substances and Disease Registry Chronic Minimal Risk 
Levels; or (3) California Office of Environment and Human Health 
Assessment's chronic Reference Exposure Level (REL).
    No such hierarchy was developed for acute noncancer reference 
values. Instead, we use acute inhalation values from multiple sources 
because the various assessments are based on methods that are different 
enough to render them not directly comparable, nor does any one set of 
reference values provide coverage across the majority of chemicals. We 
looked to reference values developed for other purposes, such as 
Reference Exposure Levels (REL), Acute Exposure Guideline Levels 
(AEGLs), and Emergency Response Planning Guideline (ERPGs).
    The acute REL (http://www.oehha.ca.gov/air/pdf/acuterel.pdf) is 

defined as the concentration level at or below which no adverse health 
effects are anticipated for a specified exposure duration. The REL 
incorporates factors to address data gaps, uncertainty, and to protect 
the most sensitive individuals in the population, and exceeding the REL 
does not automatically indicate an adverse health impact.
    The AEGL-1 is ``the airborne concentration (expressed as ppm or mg/
m\3\) of a substance above which it is predicted that the general 
population, including susceptible individuals, could experience notable 
discomfort, irritation, or certain asymptomatic nonsensory effects.'' 
The AEGL values are designed to be applicable to the general 
population, including sensitive subgroups; however, as stated in the 
AEGL guidelines and the definitions, ``it is recognized that certain 
individuals, subject to unique and idiosyncratic responses, could 
experience effects at concentrations below the corresponding AEGL.'' 
The National Research Council states that ``[t]he primary purpose of 
the AEGL program and the NAC/AEGL Committee is to develop guideline 
levels for once-in-a-lifetime, short-term exposures to airborne 
concentrations of acutely toxic, high-priority chemicals.'' \8\
---------------------------------------------------------------------------

    \8\ See Standing Operating Procedures for Developing Acute 
Exposure Guideline Levels for Hazardous Chemicals (2001, National 
Academies Press, Washington, DC, page 21, PURPOSE AND OBJECTIVES OF 
THE AEGL PROGRAM AND THE NAC/AEGL COMMITTEE; http://books.nap.edu/openbook.php?record_id=10122&page=21
).

---------------------------------------------------------------------------

    The ERPG-1, developed specifically for emergency response 
situations, is the maximum airborne concentration below which it is 
believed that nearly all individuals could be exposed for up to 1 hour 
without experiencing other than mild transient adverse health effects 
or perceiving a clearly defined, objectionable odor. The ERPG 
documentation also states that ``in all populations there are 
hypersensitive individuals who will show adverse responses at exposure 
concentrations far below levels where most individuals normally would 
respond.''
    The AEGL and ERPG values include three levels of severity generally 
referred to as mild, severe, and lethal. In contrast, the REL 
represents an exposure at which no adverse effects are expected. For 
many chemicals (e.g., ethylene oxide and phosgene) the available 
information does not allow development of a mild effect AEGL or ERPG. 
AEGL and ERPG values are usually established at higher exposure levels 
than Acute California REL reference values. Exceedances of REL, AEGL, 
or ERPG values in the context of a residual risk assessment should be 
interpreted on a case-by-case basis.
4. Consideration of Actual and Allowable Emissions
    Generally, the emissions values in our data set represent actual 
emission levels. We discussed the use of both allowable and actual 
emissions in the final Coke Oven Batteries residual risk rule (70 FR 
19998-19999, April 15, 2005) and in the proposed and final Hazardous 
Organic NESHAP (HON) residual risk rules (71 FR 34428, June 14, 2006, 
and 71 FR 76603, December 21, 2006, respectively). In those previous 
actions, we noted that modeling the allowable levels of emissions 
(i.e., the highest emission levels that could be emitted while still 
complying with the MACT requirements) is inherently reasonable since 
they reflect the maximum level sources could emit and still comply with 
national emission standards. But we also explained that it is 
reasonable to consider actual emissions, where such data are available, 
in both steps of the Benzene NESHAP analysis. Doing so avoids 
overestimating emissions and their associated health risks and accounts 
for how sources typically strive to perform better than required by 
standards to allow for process variability and to prevent exceeding 
standards due to emissions increases on individual days. Failure to 
consider these data in risk assessments, we said, would unrealistically 
inflate actual risk levels. 71 FR at 76609.
    For the eight source categories addressed in this package, we do 
not have information regarding allowable emissions. This is similar to 
the circumstance we faced in the HON. In the preamble to the HON 
proposed rule, we acknowledged that there is some uncertainty regarding 
the difference between actual and allowable emissions. We also 
explained in the HON preamble that it was not possible to estimate 
allowable emissions for all emission points from the available 
information, but that for equipment leaks, which represent the most 
significant impact on cancer risk at HON facilities, the actual and 
allowable emissions are likely the same. We further concluded that 
there was no evidence of substantial overcontrol, such that actual 
emissions would not be a reasonable approximation of allowable 
emissions, and that there was no evidence that the sources subject to 
the HON could make changes that would result in a substantial increase 
of emissions, and thus risk, while still complying with the MACT. 
Therefore, we concluded for the HON final rule that basing the analysis 
on actual emissions provided an acceptable method for determining the 
remaining risks to public health and the environment after application 
of the MACT standards.
    The production processes for polymers and resins use the same 
process equipment and air pollution control equipment as HON processes. 
Thus, we believe we can draw the same conclusions for polysulfide 
rubber production, ethylene propylene rubber production, butyl rubber 
production, neoprene rubber production, epoxy resins production, non-
nylon polyamides production, and acetal resins as we did for the HON--
that estimating risk using actual emissions will reasonably reflect the 
risk after application of the relevant MACT standards.
    For the Hydrogen Fluoride Production source category, we expect 
actual and allowable emissions to be similar, if not the same. Hydrogen 
fluoride facilities employed stringent controls prior to the 
development of the MACT standards (we based the MACT standards on these 
pre-MACT controls) and we have no

[[Page 70550]]

reason to believe control performance will decline.
    We believe the differences between actual and allowable emissions 
are likely insignificant for these eight source categories and that 
using the actual emission levels results in a reasonable approximation 
of the allowable emissions. Therefore, we conclude that the risk 
assessment results using actual emissions closely approximate those for 
an assessment using allowable emissions and that the difference would 
not be likely to substantially affect the estimated risk associated 
with exposure to HAP emitted by any of the eight source categories. 
Nevertheless, if commenters have data that demonstrate that allowable 
emissions could be higher or lower than actual emissions for these 
eight source categories we request the submission of this data.
5. Adverse Environmental Effects Assessment
    None of the eight source categories emit persistent or 
bioaccumulative HAP; therefore, EPA's assessment of environmental 
effects evaluated only non-persistent and non-bioaccumulative HAP.\9\ 
For animal populations, the potential for significant direct adverse 
environmental effects due to non-persistent and non-bioaccumulative HAP 
was evaluated implicitly by checking for exceedances of any human 
health inhalation dose-response limit values near the assessed 
facilities. \10\ Because these values generally reflect the inclusion 
of uncertainty factors \11\ (often 100 or 1,000), the human threshold 
values are generally believed to be significantly lower than any levels 
which have been shown to cause an adverse effect in an exposed animal. 
Therefore, if the maximum inhalation hazard in an ecosystem is below 
the level of concern for humans, we have concluded that, in general, 
environmental receptors should be at little risk of adverse effects due 
to airborne exposures.
---------------------------------------------------------------------------

    \9\ Persistent and bioaccumulative HAP are those which persist 
in the environment and which also may bioaccumulate or biomagnify in 
food chains.
    \10\ While environmental effects thresholds are often available 
for HAP in water and soil, very few are available for direct 
airborne exposures.
    \11\ The uncertainty factors account for various data 
methodological uncertainties, for example, most inhalation dose-
response limit values are derived from studies of laboratory 
animals.
---------------------------------------------------------------------------

    One possible exception is pollutants that may directly impact 
various species of vegetation. For the seven polymers and resins 
production source categories affected by today's proposal, we have no 
scientific data, informal observations or other information that would 
indicate any concern for adverse environmental effects of HAP on 
vegetation at the expected air concentrations.
    For the two facilities in the Hydrogen Fluoride Production source 
category (both of which emit hydrogen fluoride), we have some general 
information on the possible effects of hydrogen fluoride on vegetation 
at ambient concentrations well below the California chronic REL value 
of 14 microgram per cubic meter ([mu]g/m\3\). In separate and unrelated 
studies, air concentrations of hydrogen fluoride greater than about 1 
[mu]g/m\3\ have been shown to adversely affect specific sensitive plant 
species. \12\ We note that responses to hydrogen fluoride are highly 
variable among plant species and responses may be influenced by co-
exposures to other air pollutants. In this particular case, the maximum 
chronic ambient concentration estimated in the vicinity of the hydrogen 
fluoride production facilities was about 1.5 [mu]g/m\3\, meaning that 
concentrations of hydrogen fluoride in all areas other than the maximum 
point are lower than 1.5 [mu]g/m\3\, and perhaps substantially lower as 
the distance from the point of release increases. Because the 
spatially-averaged hydrogen fluoride concentration within several 
kilometers of each facility is likely well below 1 [mu]g/m\3\, we are 
led to the conclusion that any significant and widespread adverse 
environmental effects on plants due to hydrogen fluoride emissions are 
unlikely. Further, we have no information suggesting that there are 
currently observed adverse impacts of hydrogen fluoride emissions on 
plants surrounding the two facilities.
---------------------------------------------------------------------------

    \12\ 1 [mu]g/m\3\ was the lowest concentration for which adverse 
effects were observed in the most sensitive flora for which data 
exists. We note that the studies were limited to certain species and 
1 [mu]g/m\3\ cannot be interpreted as an appropriate or definitive 
concentration level for all plant species. (See ``List of References 
for Effects of Hydrogen Fluoride on Vegetation'' in docket.)
---------------------------------------------------------------------------

6. Uncertainties in Risk Assessments
    Uncertainty and the potential for bias are inherent in all risk 
assessments, including those performed for the eight source categories 
affected by today's proposal. We reduced some of these uncertainties by 
developing a new emissions data set, the RTR database, that is based on 
the NEI, but that includes more accurate replacement or supplemental 
data for the specific facilities in these eight source categories.
    Although uncertainty exists, we believe the risk assessments 
performed for the eight source categories most likely overestimate the 
potential for risks due to the conservative (i.e., health-protective) 
assessment approach. Because these health protective risk assessments 
indicate little, if any, potential for significant risk, we believe 
they support our proposed decision not to issue residual risk standards 
for these eight source categories. A brief discussion of the 
uncertainties in the emissions data set, dispersion modeling, 
inhalation exposure estimates, and dose-response relationships is 
presented in this section of the preamble. A fuller discussion of these 
uncertainties is discussed in both the ``Residual Risk Assessment for 
Eight Source Categories'' (July 2007) and the ``Risk and Technology 
Review (RTR) Assessment Plan'' (November 2006), both of which are 
available in the docket.
    a. Uncertainties in the RTR Emissions Database. Although the 
development of the RTR database involved quality assurance/quality 
control processes, the accuracy of emissions values will vary depending 
on the source of the data present, incomplete or missing data, errors 
in estimating emissions values, and other factors. The emission values 
considered in this analysis are annual totals that do not reflect 
actual fluctuations during the course of a year (2002) or variations 
from year to year. These annual emissions estimates do not consider 
operations such as startup/shutdown and malfunctions. The estimates of 
health protective short-term emission rates for the screening 
assessment were based on a health-protective default assumption 
applicable to these source categories (10 times the annual rate). More 
refined estimates were used for source categories where the screening 
estimates did not ``screen out'' all sources and more specific 
information was available.
    Facilities in some of the seven polymers and resins source 
categories emit chlorinated compounds and use incineration devices, 
creating the possibility for the formation of polychlorinated dioxins. 
However, we have no test reports or measurements, conducted by 
manufacturers or anyone else, indicating the presence of dioxins in the 
emissions from any of these source categories and EPA's dioxins 
inventory \13\ does not specifically link

[[Page 70551]]

dioxins emissions to any of these source categories. Furthermore, in 
our judgment, it is improbable that dioxins are emitted in measurable 
amounts from the seven polymers and resins source categories, 
especially given the low quantity of particulate matter present. 
Therefore, we did not consider dioxins in our assessment of the seven 
polymers and resins production source categories. Because no 
chlorinated compounds are emitted from the hydrogen fluoride production 
source category, we believe there is no possibility for dioxins to be 
emitted and we did not consider dioxins in our assessment of the source 
category.
---------------------------------------------------------------------------

    \13\ An Inventory of Sources and Environmental Releases of 
Dioxin-Like Compounds in the United States for the Years 1987, 1995, 
and 2000. (EPA/600/P-03/002f, Final Report, November 2006). The 
dioxins inventory (http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=159286
) classifies ``rubber manufacturing'' as 

an unquantifiable dioxins emission source. A source was defined as 
unquantifiable if dioxins releases were possible, but the data were 
inadequate to support even rudimentary calculations of emissions. 
Furthermore, the process could be very different from the polymers 
and resins processes of concern in this proposal.
---------------------------------------------------------------------------

    Overall we believe that the emissions data considered in this 
assessment are the most accurate available representation of the eight 
source categories for the stated purpose. Nevertheless, we request 
comment on our emissions data set in general, and specifically on our 
approach to short-term emissions estimates and on the potential for 
dioxins emissions from the facilities in the seven polymers and resins 
production source categories affected by today's proposal.
    b. Uncertainties in Dispersion Modeling. While the analysis 
employed EPA's suggested regulatory dispersion model, AERMOD, there is 
uncertainty in ambient concentration estimates associated with EPA's 
choice and application of the model. Where possible, model options 
(e.g., rural/urban, plume depletion, chemistry) were selected as to 
provide an overestimate of ambient air concentrations. However, because 
of practicality and data limitation reasons, some factors (e.g., 
meteorology, building downwash) have the potential in some situations 
to overestimate or underestimate ambient impacts. For example, 
meteorological data were taken from a single year (1991), and facility 
locations can be a significant distance from the site where these data 
were taken. Despite these uncertainties, we believe that at off-site 
locations and census block centroids, the approach considered in the 
dispersion modeling analysis should generally yield overestimates of 
ambient concentrations.
    c. Uncertainties in Inhalation Exposure. The effects of human 
mobility on exposures were not included in the assessment. 
Specifically, short-term mobility and long-term mobility\14\ between 
census blocks in the modeling domain was not considered. As a result, 
this simplification will likely bias the assessment toward 
overestimating the highest exposures. In addition, the assessment 
predicted the chronic exposures at the centroid of each populated 
census block as surrogates for the exposure concentrations for all 
people living in that block. (On average census blocks are populated by 
approximately 40 people.) Using the census block centroid to predict 
chronic exposures tends to overpredict exposures for people in the 
census block who live further from the facility and underpredict 
exposures for people in the census block who live closer to the 
facility. Thus, in general, using the census block centroid to predict 
chronic exposures leads to a potential understatement or overstatement 
of maximum impact and an unbiased estimate of average risk and 
incidence.
---------------------------------------------------------------------------

    \14\ Short-term mobility is movement from one microenvironment 
to another over the course of hours or days. Long-term mobility is 
movement from one residence to another over the course of a 
lifetime.
---------------------------------------------------------------------------

    The assessments evaluate the cancer inhalation risks associated 
with pollutant exposures over a 70-year period, the assumed lifetime of 
individuals. In reality, both the length of time that modeled emissions 
sources at facilities actually operate (i.e., more or less than 70 
years), and the domestic growth or decline of the modeled industry 
(i.e., the increase or decrease in the number or size of U.S. 
facilities), will influence the risks posed by a given source category. 
Depending on the characteristics of the industry, these factors may 
result in an overestimate (or possibly an underestimate in the extreme 
case where a facility maintains or increases its emission levels beyond 
70 years and residents live beyond 70 years at the same location) both 
in individual risk levels and in the total estimated number of cancer 
cases. Annual cancer incidence estimates from exposures to emissions 
from these sources would not be affected by uncertainty in the length 
of time emissions sources operate.
    The exposure estimates used in these analyses assume chronic 
exposures to ambient levels of pollutants. Because most people spend 
the majority of their time indoors, actual exposures may not be the 
same, depending on characteristics of the pollutants modeled. For many 
HAP, indoor levels are roughly equivalent to ambient levels, but for 
very reactive pollutants or larger particles, these levels are 
typically lower. This factor has the potential to result in an 
overstatement of 25 to 30 percent of exposures.\15\
---------------------------------------------------------------------------

    \15\ National-Scale Air Toxics Assessment for 1996. (EPA 453/R-
01-003; January 2001; page 85.)
---------------------------------------------------------------------------

    In addition to the uncertainties highlighted above, there are 
several factors specific to the acute exposure assessment that need to 
be highlighted. The accuracy of an acute inhalation exposure assessment 
depends on the joint occurrence of independent factors that may vary 
greatly, such as hourly emissions rates, meteorology, and human 
activity patterns. In this assessment, we assume that individuals 
remain for one hour at the point of maximum ambient concentration as 
determined by the co-occurrence of peak emissions and worst-case 
meteorological conditions. These assumptions would tend to overestimate 
actual exposures since it is unlikely that a person would be located at 
the point of maximum exposure during the time of worst-case impact.
    d. Uncertainties in Dose-Response Relationships. These assessments 
use toxicological dose-response values typically extrapolated from 
high-dose animal exposure or occupational exposures, to estimate risk. 
Consistent with EPA guidance, RfCs are developed by using order-of-
magnitude factors to account for uncertainties in developing values 
protective of sensitive subpopulations. Most of the URE in this 
assessment were developed using linear low-dose extrapolation. Risks 
could be overestimated if the true dose-response relationship (which is 
usually unknown) is sublinear and underestimated when the dose-response 
curve is actually superlinear. Impacts have been extrapolated from 
short-duration, high-dose animal or occupational exposures to longer 
durations and lower doses, using uncertain interspecies scaling 
methods. In general, EPA considers these URE's to be upper bound 
estimates based on the method of extrapolation, meaning they represent 
a plausible upper limit to the true value. (Note that this is usually 
not a true statistical confidence limit.) The true risk is therefore 
likely to be less, could be as low as zero, but also could be greater. 
As previously noted, benzene cancer risks were estimated from the 
reported URE range, which is considered to be based on maximum 
likelihood exposure and risk estimates.
    Some HAP have no dose-response values for cancer, chronic non-
cancer, and/or acute effects. Therefore, an understatement of risk for 
certain HAP at environmental exposure levels is possible if there are 
no health effects reference values available on which to

[[Page 70552]]

base an assessment of health risk. Additionally, some chronic dose-
response values used in the assessments for these 8 source categories 
are currently under EPA IRIS review (e.g., formaldehyde and methanol) 
and revised assessments may determine that these HAP are more or less 
potent than currently thought. We will consider the outcome of new 
assessments and reevaluate residual risk if application of new dose-
response values indicates the potential for unacceptable risks to human 
health and/or the environment.
    e. Uncertainties in the Adverse Environmental Effects Assessment. 
As previously discussed, we generally believe that when exposure levels 
are not anticipated to adversely affect human health, they also are not 
anticipated to adversely affect the environment. However, we recognize 
that this may not be the case for all HAP. Hydrogen fluoride in the air 
has the potential to adversely affect plant tissues, having been 
associated with necrosis (lesions) in plants and reduced plant growth 
and productivity. Determining the effects of hydrogen fluoride on 
vegetation is complicated by the high degree of variability among plant 
species in the extent of uptake and response to atmospheric hydrogen 
fluoride, and by co-exposure to other atmospheric pollutants, such as 
sulfur dioxide, that influences the impacts of hydrogen fluoride. (For 
references concerning the effects of hydrogen fluoride on plants, see 
docket item ``List of References for Effects of Hydrogen Fluoride on 
Vegetation''.)
    EPA requests comment on this issue, including: Submissions of any 
data that should be considered; observations, if any, of impacts on 
vegetation near the two facilities in the hydrogen fluoride production 
source category; and suggestions of how EPA should assess the potential 
for adverse environmental effects as defined in CAA section 
112(a)(7).\16\
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    \16\ CAA section 112(a)(7) defines ``adverse environmental 
effect'' as meaning ``any significant and widespread adverse effect, 
which may reasonably be anticipated, to wildlife, aquatic life, or 
other natural resources, including adverse impacts on populations of 
endangered or threatened species or significant degradation of 
environmental quality over broad areas.
---------------------------------------------------------------------------

D. What are the conclusions of the risk review?

    The human health risks estimated for the eight source categories 
are summarized in this section of the preamble. Details of the 
assessment are located in the docket, especially see ``How to Reproduce 
Modeling of Group 1 Source Categories'' (May 2007). We believe that our 
assessment covers all potential health risks associated with HAP 
emissions from the eight source categories affected by today's 
proposal. We further believe that the reported emissions are consistent 
with the expected constituents and amounts for these source categories. 
The sections below provide more detailed discussions about the human 
health risk assessment results for each of the eight source categories.

                 Table 4.--Summary of Estimated Inhalation Risks for the Eight Source Categories
----------------------------------------------------------------------------------------------------------------
                                                  Maximum
                                                 individual       Estimated                        Maximum off-
                                 Number of    cancer risk (in   annual cancer   Max. HI \3\ and   site acute HQ
       Source category         facilities\1\   a million) \2\   incidence and     HAP of most    and HAP of most
                                              and HAP of most    HAP of most        concern        \4\ concern
                                                  concern          concern
----------------------------------------------------------------------------------------------------------------
Polysulfide Rubber                         1  0 \6\..........  0 \6\..........  < 0.01 (MDI \5\)  0.0004\AEGL\	
 Production.                                                                                      \1\ (MDI\4\).
Ethylene Propylene Rubber                  5  0 \6\..........  0 \6\..........  0.5 (hexane)...  0.3\REL\
 Production.                                                                                      (toluene).
Butyl Rubber Production.....               2  0 \6\..........  0 \6\..........  0.2 (methyl      0.1AEGL	2(methy
                                                                                 chloride).       l chloride
                                                                                                  \7\).
Neoprene Production.........               1  0 \6\..........  0 \6\..........  0.8              0.4\REL\
                                                                                 (chloroprene).   (toluene).
Epoxy Resins Production.....               3  0.1              0.00002          0.1              0.6\REL\
                                               (epichlorohydr   (epichlorohydr   (epichlorohydr   (epichlorohydr
                                               in).             in).             in).             in).
Non-nylon Polyamides                       4  0.4              0.00003          0.3              0.2\REL\
 Production.                                   (epichlorohydr   (epichlorohydr   (epichlorohydr   (epichlorohydr
                                               in).             in).             in).             in).
Acetal Resins Production....               3  0.3 (allyl       0.00004 (allyl   0.2 (chlorine).  1.7\REL\
                                               chloride).       chloride).                        (formaldehyde)
                                                                                                  .
Hydrogen Fluoride Production               2  0 \6\..........  0 \6\..........  < 0.01            0.3\REL\
                                                                                 (hydrofluoric    (hydrofluoric
                                                                                 acid).           acid).
----------------------------------------------------------------------------------------------------------------
\1\ Number of facilities believed to be in the source category and used in the risk analysis.
\2\ Maximum individual excess lifetime cancer risk.
\3\ Maximum hazard index (HI) is maximum respiratory HI for all except two source categories. Maximum HI for
  butyl rubber production is based on neurological effects. Maximum HI for hydrogen fluoride production is based
  on skeletal effects.
\4\ The maximum estimated acute exposure concentration was divided by available short-term threshold values to
  develop an array of hazard quotient (HQ) values. These include RELs and AEGL-1 and AEGL-2 values. The acute
  REL is an exposure that is not likely to cause adverse effects in a human population, including sensitive
  subgroups, exposed to that concentration for one hour on an intermittent basis. AEGL-1 is the airborne
  concentration (expressed as ppm or mg/m\3\) of a substance above which it is predicted that the general
  population, including susceptible individuals, could experience notable discomfort, irritation, or certain
  asymptomatic nonsensory effects. However, the effects are not disabling and are transient and reversible upon
  cessation of exposure. AEGL-2 is the airborne concentration (expressed as ppm or mg/m3) of a substance above
  which it is predicted that the general population, including susceptible individuals, could experience
  irreversible or other serious, long-lasting adverse health effects or an impaired ability to escape.
\5\ MDI is methylene diphenyl diisocyanate.
\6\ No HAP which are known, probable, or possible human carcinogens.
\7\ For methyl chloride, REL and AEGL-1 were not available.

    As shown in Table 4, we estimate that the residual risk remaining 
from HAP emissions from these eight source categories affected by 
today's proposal do not pose cancer risks equal to or greater than 1-
in-1 million to the individual most exposed, do not result in 
meaningful rates of cancer incidence, and do not result in a concern 
regarding either chronic or acute noncancer health effects for the 
individual most exposed.
    No chronic inhalation human health thresholds were exceeded at 
ecological receptors for any of the eight source

[[Page 70553]]

categories; therefore, we believe there is low potential for adverse 
environmental effects due to direct airborne exposures. We also believe 
that there is no potential for an adverse effect on threatened or 
endangered species or on their critical habitat within the meaning of 
50 CFR 402.13(a) because our screening analyses indicate no potential 
for any adverse ecological impacts. Thus, we conclude that a 
consultation with the Fish and Wildlife Service is not necessary for 
any of the eight source categories.
    Human health multipathway risks were determined not to be a concern 
for the eight source categories addressed in today's proposal due to 
the absence of persistent and bioaccumulative (PB) \17\ HAP emissions 
at all of these sources. The lack of PB HAP emissions also provides 
assurance that there will be no potential for adverse ecological 
effects due to indirect ecological exposures (i.e., exposures resulting 
from the deposition of PB HAP from the atmosphere).
---------------------------------------------------------------------------

    \17\ Persistent and bioaccumulative (PB) HAP are the list of 14 
HAP that have the ability to persist in the environment for long 
periods of time and may also have the ability to build up in the 
food chain to levels that are harmful to human health and the 
environment.
---------------------------------------------------------------------------

1. Polymers and Resins I--Polysulfide Rubber Production
    The only HAP emitted by the Polysulfide Rubber Production source 
category in 2002 was 4,4'-methylene diphenyl diisocyanate (MDI), whose 
carcinogenic potential was evaluated in EPA's IRIS in 1998, and 
characterized as ``cannot be determined, but for which there is 
suggestive evidence that raises concern for carcinogenic effects.''
    The maximum chronic noncancer TOSHI associated with emissions from 
polysulfide rubber production is less than 0.01, indicating that 
chronic noncancer risks are negligible. Further, our analysis, based on 
available information, indicates this source category poses no 
potential for adverse environmental impacts. Combining these results 
with the lack of information on potential cancer risks and the 
additional fact that no sources in this category are currently in 
operation, we conclude that there is no reason to modify the existing 
standard.
2. Polymers and Resins I--Ethylene Propylene Rubber Production
    Because none of the HAP emitted are known, probable, or possible 
human carcinogens, we currently believe there are no cancer risks 
associated with exposures to the HAP emissions from this source 
category. The maximum chronic noncancer TOSHI value associated with 
emissions from ethylene propylene rubber production is 0.5. No adverse 
noncancer health effects associated with the modeled acute or chronic 
inhalation exposures are expected from the Ethylene Propylene Rubber 
Production source category. Our analysis, based on available 
information, indicates this source category poses no potential for 
adverse environmental impacts.
3. Polymers and Resins I--Butyl Rubber Production
    Because none of the HAP emitted are known, probable, or possible 
human carcinogens, we currently believe there are no cancer risks 
associated with exposures to the HAP emissions from this source 
category. The maximum chronic noncancer TOSHI value associated with 
emissions from butyl rubber production is 0.2. We saw no exceedances of 
any available acute thresholds. Our analysis, based on available 
information, indicates this source category poses no potential for 
adverse environmental impacts.
    A source of uncertainty unique to this source category is the lack 
of certain acute dose-response values (REL and AEGL) for methyl 
chloride. Since the only acute dose-response value available is for 
methyl chloride is the ERPG2 \18\ value which doesn't account for 
possible mild transient effects, there is some uncertainty regarding 
the conclusion that there are no possible acute impacts of concern.
---------------------------------------------------------------------------

    \18\ ERPG-2 is the maximum airborne concentration below which it 
is believed that nearly all individuals could be exposed for up to 1 
hour without experiencing or developing irreversible or other 
serious health effects or symptoms which could impair an 
individual's ability to take protective action.
---------------------------------------------------------------------------

4. Polymers and Resins I--Neoprene Production
    Because none of the HAP emitted are known, probable, or possible 
human carcinogens, we currently believe there are no cancer risks 
associated with exposures to the HAP emissions from this source 
category. The maximum chronic noncancer TOSHI value associated with 
emissions from neoprene production is 0.8. There are no expected 
adverse noncancer health effects associated with the modeled acute or 
chronic inhalation exposures from the Neoprene Production source 
category. Our analysis, based on available information, indicates this 
source category poses no potential for adverse environmental impacts.
5. Polymers and Resins II--Epoxy Resins Production
    All lifetime cancer risks associated with emissions from the three 
epoxy resins production facilities are estimated to be less than 1-in-1 
million. The highest maximum lifetime individual cancer risk was 
estimated at 0.1-in-1 million. The total estimated cancer incidence 
from these facilities is 0.00002 excess cancer cases per year. The 
maximum chronic noncancer TOSHI value associated with emissions from 
epoxy resins production is 0.1. We saw no exceedances of any available 
acute thresholds. Our analysis, based on available information, 
indicates this source category poses no potential for adverse 
environmental impacts.
6. Polymers and Resins II--Non-Nylon Polyamides Production
    All lifetime cancer risks associated with emissions from the four 
non-nylon polyamides production facilities are estimated to be less 
than 1-in-1 million. The highest maximum lifetime individual cancer 
risk was estimated at 0.4-in-1 million. The total estimated cancer 
incidence from these facilities is 0.00003 excess cancer cases per 
year. The maximum chronic noncancer TOSHI value associated with 
emissions from non-nylon polyamides production is 0.3. There are no 
expected adverse noncancer health effects associated with the modeled 
acute or chronic exposures from the neoprene production source 
category. Our analysis, based on available information, indicates this 
source category poses no potential for adverse environmental impacts.
7. GMACT--Acetal Resins Production
    All lifetime cancer risks associated with emissions from the three 
acetal resins production facilities are estimated to be less than 1-in-
1 million. The highest maximum lifetime individual cancer risk was 
estimated at 0.3-in-1 million. The total estimated cancer incidence 
from these facilities is 0.00004 excess cancer cases per year. The 
maximum chronic noncancer TOSHI value associated with emissions from 
acetal resins production is 0.2. Our analysis, based on available 
information, indicates this source category poses no potential for 
adverse environmental impacts.
    The initial screening assessment for acute impacts suggested that 
short-term formaldehyde concentrations at the three modeled facilities 
could exceed acute thresholds if worst-case meteorological conditions 
are present and if maximum hourly emissions of formaldehyde exceed the 
average hourly

[[Page 70554]]

emission rate by a factor of 10. One of the facilities showed potential 
exceedances of the REL only, and two facilities showed potential 
exceedances of both the REL and the AEGL-1. Therefore, we performed 
further site-specific analysis and mapped the screening results as a 
series of concentration isopleths overlaid against the aerial 
photograph of the facility in question. The results of this exercise 
for the first facility were that the isopleths that exceeded the REL 
did not extend off the facility site. Therefore, acute exposures to HAP 
emitted by this facility are not expected to pose any public health 
concerns. We further refined the assessments using better site-specific 
data for the other two facilities. Discussions with a plant engineer 
for one facility revealed that the acetal resins processes operate 
continuously and that a reasonable worst-case emissions multiplier 
would be 1.5 instead of our default multiplier of 10. We performed more 
refined modeling (AERMOD) for these two facilities using the emissions 
multiplier of 1.5. The results for the second facility indicated no 
potential for exceeding the AEGL-1 and showed that the potential for 
exceedances of the REL did not extend off-site, except for a small 
extension over a river to the north of the facility. The maximum off-
site REL HQ corresponding to these locations is 1.7 (HQ = 0.14 using 
the AEGL-1). The analysis showed that meteorological conditions 
resulting in exceedances of the REL may occur up to 2 hours per year 
along the river. We believe the potential for adverse acute health 
effects surrounding this facility is low. The results for the third 
facility showed potential for exceeding the REL in an area immediately 
adjacent to the facility along a roadway. The maximum off-site HQ for 
this facility is 1.6 for the REL (HQ = 0.13 using the AEGL-1). The 
analysis showed that meteorological conditions resulting in exceedances 
of the REL may occur up to 46 hours per year along the roadway. 
Additionally, the third facility reports that current actual emissions 
for this facility are significantly less than those used for this 
assessment because one of the higher emission sources listed for this 
facility in the 2002 NEI data has been shut down. Based on this new 
information, we believe that the actual projected maximum off-site HQ 
for this facility is less than 1.0. We request interpretation and 
comment on this as well as any additional data regarding the potential 
acute impacts of these facilities.
    A source of uncertainty that is unique to this source category is 
associated with annual emissions of HAP and the relationship between 
annual emissions and maximum hourly emissions. One facility reports 
emissions of benzene and allyl chloride, which are two relatively toxic 
HAP not expected to be emitted from this source category. Since the 
risk assessment shows allyl chloride to be the cancer risk driver for 
the source category, this indicates a potential overestimate of the 
cancer risks
8. GMACT--Hydrogen Fluoride Production
    Because hydrogen fluoride, the only HAP emitted from the source 
category, is not a known, probable, or possible human carcinogen, we 
currently believe there are no cancer risks associated with exposures 
to the HAP emissions from this source category. The maximum chronic 
noncancer TOSHI value associated with emissions from hydrogen fluoride 
production is less than 0.01.
    The initial screening assessment for acute impacts suggests that 
short-term hydrofluoric acid concentrations at the two modeled 
facilities could exceed acute thresholds if worst-case meteorological 
conditions are present and if maximum hourly emissions of hydrofluoric 
acid exceed the average hourly emission rate by a factor of 10. Since 
one of the facilities showed potential exceedances of the REL only, and 
one facility showed potential exceedances of both the REL and the AEGL-
1, we performed additional site specific assessments. We contacted the 
permitting agency and a process engineer at one of the facilities to 
gather additional source specific information. Based on discussions 
with the permitting agency and the process engineer, we determined that 
these facilities operate continuously and that the peak hourly 
emissions are not expected to exceed twice the hourly average. By 
adjusting the short-term emission rate to more accurately represent the 
true facility operating conditions (from 10 to 2), no offsite impacts 
above the REL were predicted from the first facility. For the second 
facility that exceeded both the REL and AEGL-1, we remodeled using the 
AERMOD model to more accurately predict the worst case acute impacts. 
By adjusting the short-term emission rate to more accurately represent 
facility operating conditions (from 10 to 2), exceedances of the REL 
and AEGL-1 were predicted to occur within the facility property 
boundary, but not offsite.
    A source of uncertainty unique to this source category involves the 
adequacy of our screening for potential adverse environmental effects 
for the pollutant hydrogen fluoride, as discussed in section I.C.6.e of 
this preamble. Indeed, there is a significant lack of scientific 
understanding and assessment methodologies for such potential adverse 
environmental effects. However, we believe acute and chronic noncancer 
assessment results (maximum chronic TOSHI less than 0.01 and maximum 
acute HQ of 0.3 for REL and 0.09 for AGEL-1) support our conclusion 
that no adverse environmental impacts are expected for this source 
category.

E. What are the conclusions of the technology review?

    For seven of the source categories affected by today's proposal 
(all except the Hydrogen Fluoride Production source category), we 
relied on the technology review conducted for the HON, which did not 
identify any significant developments in practices, processes, or 
control technologies since promulgation of the original HON standards 
in 1994.\19\ These seven source categories are similar to those under 
the HON because they use the same kinds of process and pollution 
control equipment and are subject to similar control requirements.\20\ 
For the seven HON-like source categories affected by today's proposal, 
we conclude that imposing additional controls under any control option 
would achieve, at best, minimal emission and risk reductions. 
Furthermore, elimination of all HAP, if it were possible, from all 
seven of these source categories combined would reduce estimated cancer 
incidence by less than 0.0002 cases per year. For HAP with available 
dose-response values, the maximum HI for these facilities are all below 
one and the cancer risks are all below 1-in-1 million.
---------------------------------------------------------------------------

    \19\ Discussed in the proposed and final HON residual risk 
preambles (71 FR 34428, June 14, 2006, and 71 FR 76603, December 21, 
2006, respectively).
    \20\ Process equipment, pollution control equipment, and control 
requirements are summarized in the proposal BID.
---------------------------------------------------------------------------

    Elimination of all HAP \21\ emissions from the Hydrogen Fluoride 
source category, if it were possible, would reduce HAP emissions by 8 
tons per year and would not affect cancer incidence, which is 0 
(hydrogen fluoride is not a known, probable, or possible human 
carcinogens). The noncancer risk is low (the maximum HI is less than 
0.01 with the current level of emissions achieved by the GMACT)

[[Page 70555]]

and further emissions reductions would provide insignificant, if any, 
health benefits. In addition, all hydrogen fluoride emissions are from 
control device vents equipped with control devices that achieve 99 
percent reductions. Improvements in hydrogen fluoride controls are not 
feasible.
---------------------------------------------------------------------------

    \21\ Hydrogen fluoride is the only HAP emitted from the Hydrogen 
Fluoride source category.
---------------------------------------------------------------------------

    We conclude that the existing MACT standards effectively address 
HAP emissions for all eight source categories: Cancer risks and 
incidence to humans, chronic and acute exposure noncancer risks to 
humans, and adverse environmental effects from these facilities are 
insignificant based on available health benchmarks, and no advancements 
in practices, processes, or control technology that make additional 
controls cost-effective are known.

II. Proposed Action

    Section 112(f) of the CAA requires that EPA promulgate standards 
for a category if promulgation of such standards is required to provide 
an ample margin of safety to protect public health or to prevent, 
taking into consideration costs, energy, safety, and other relevant 
factors, an adverse environmental effect. The approach we use is that 
set forth in the preamble to the Benzene NESHAP. First we exclusively 
evaluate health risk measures and information in determining whether 
risks are acceptable. Second, we may consider costs and other factors 
in deciding whether further emission reductions are necessary to 
protect public health with an ample margin of safety. The Benzene 
NESHAP preamble explained that in protecting public health with an 
ample margin of safety under CAA section 112, EPA strives to provide 
maximum feasible protection against risks to health from HAP by 
protecting the greatest number of persons possible to an individual 
lifetime risk level no higher than approximately 1-in-1 million.
    EPA is not required to promulgate standards for a source category 
under section 112(f) if public health is protected with an ample margin 
of safety and adverse environmental effects are prevented. For the 
eight source categories that are the subject of today's notice, we have 
concluded (based on the results of risk assessments) that the existing 
MACT standards protect public health with an ample margin of safety and 
prevent an adverse environmental effect. In making this conclusion, we 
determined that the source categories addressed in today's proposal 
that emit one or more HAP which are known or potential carcinogens pose 
cancer risks less than or equal to 1-in-1 million to the individual 
most exposed. In addition, we also determined that emissions from these 
source categories result in chronic noncancer target organ-specific HI 
less than or equal to 1 for the individual most exposed, are unlikely 
to result in health effects under acute scenarios and are not 
anticipated to pose any significant and widespread adverse 
environmental effects. In reaching this conclusion, we did not consider 
costs.
    Furthermore, as explained in section I.E. of this preamble, there 
have been no significant developments in practices, processes, or 
control technologies since promulgation of the MACT standards. Because 
there have been no such significant developments and because public 
health is protected with an ample margin of safety, we conclude that no 
further revisions to the standards affected by today's proposal are 
needed under section 112(d)(6) of the CAA.
    Therefore, we propose no revisions to the standards for the eight 
source categories: Butyl Rubber Production, Ethylene-Propylene Rubber 
Production, Polysulfide Rubber Production, Neoprene Production, Epoxy 
Resins Production, Ethylene-Propylene Rubber Production, Acetal Resins 
Production, and Hydrogen Fluoride Production.

III. How do I access and review the facility-specific data?

    The facility-specific data for each source category are available 
for download on the RTR webpage at http://www.epa.gov/ttn/atw/rrisk/rtrpg.html.
 The eight source categories affected by today's proposal 

are referred to as Group 1 of RTR Phase 2. These data files include 
detailed information for each emissions release point at each facility 
in the source category. For large integrated facilities with multiple 
processes representing multiple source categories, it is often 
difficult to clearly distinguish the source category to which each 
emission point belongs. For this reason, the data available for 
download for each source category include all emission points for each 
facility in the source category, though only the emission points marked 
as belonging to the specific source category in question were included 
in the analysis for that source category.
    The data files for each source category must be downloaded from the 
RTR Web page to be viewed (http://www.epa.gov/ttn/atw/rrisk/rtrpg.html
). These are Microsoft[supreg] Access files, which require 

Microsoft[supreg] Access to be viewed (if you do not have 
Microsoft[supreg] Access, contact us by e-mail at RTR@epa.gov). Each 
file contains the following information from the NEI for each facility 
in the source category:

----------------------------------------------------------------------------------------------------------------
              Facility data                                            Emissions data
----------------------------------------------------------------------------------------------------------------
EPA Region...............................  Pollutant Code.
Tribal Code..............................  Pollutant Code Description.
Tribe Name...............................  HAP Category Name.
State Abbreviation.......................  Emissions (TPY).
County Name..............................  MACT Code.
State County FIPS........................  MACT Source Category Name.
NEI Site ID..............................  MACT Flag.
Facility Name............................  MACT Compliance Status Code.
Location Address.........................  SCC Code.
City Name................................  SCC Code Description.
 State Name..............................  Emission Unit ID.
Zip Code.................................  Process ID.
Facility Registry........................  Emission Release Point ID.
State Facility Identifier................  Emission Release Point Type Code.
SIC Code.................................  Emission Release Point Type.
SIC Code Description.....................  Stack Default Flag.
NAICS Code...............................  Stack Default Flag Description.
Facility Category Code...................  Stack height.

[[Page 70556]]

Facility Category........................  Exit Gas Temperature.
                                           Stack Diameter.
                                           Exit Gas Velocity.
                                           Exit Gas Flow Rate.
                                           Fugitive Length.
                                           Fugitive Width.
                                           Fugitive Angle.
                                           Longitude.
                                           Latitude.
                                           Location Default Flag.
                                           Data Source Code.
                                           Data Source Description.
                                           HAP Emissions Performance Level Code.
                                           HAP Emissions Performance Level Description.
                                           Start Date.
                                           End Date.
----------------------------------------------------------------------------------------------------------------

More information on these NEI data fields can be found in the NEI 
documentation at http://www.epa.gov/ttn/chief/net/2002inventory.html#documentation
.

IV. How do I submit suggested data corrections?

    If you believe that the data are not representative or are 
inaccurate, please identify the data in question, provide your reason 
for concern, and provide improved data if available. When submitting 
data, we ask that you provide documentation of the basis for the 
revised values to support any suggested changes.
    To submit comments on the data downloaded from the RTR Web page, 
complete the following steps:
    1. Within this downloaded file, enter suggested revisions in the 
data fields appropriate for that information. The data fields that may 
be revised include the following:

----------------------------------------------------------------------------------------------------------------
              Facility data                                            Emissions data
----------------------------------------------------------------------------------------------------------------
REVISED Tribal Code......................  REVISED Emissions (TPY).
REVISED County Name......................  Emissions Calculation Method Code.
REVISED Facility Name....................  REVISED MACT Code.
REVISED Location Address.................  REVISED SCC Code.
REVISED City Name........................  REVISED Emission Release Point Type.
REVISED State Name.......................  REVISED Start Date.
REVISED Zip Code.........................  REVISED End Date.
REVISED Facility Registry Identifier.....  Revised Pollutant Code.
REVISED Facility Category Code...........  REVISED Stack height.
                                           REVISED Exit Gas Temperature.
                                           REVISED Stack Diameter.
                                           REVISED Exit Gas Velocity.
                                           REVISED Exit Gas Flow Rate.
                                           REVISED Longitude.
                                           REVISED Latitude.
                                           REVISED HAP Emissions Performance Level.
----------------------------------------------------------------------------------------------------------------

    2. Fill in the following commenter information fields for each 
suggested revision:
     Commenter Name.
     Commenter Organization.
     Commenter E-Mail Address.
     Commenter Phone Number.
     Revision Comments.
    3. Gather documentation for any suggested emissions revisions 
(e.g., performance test reports, material balance calculations, etc.).
    4. Send the entire downloaded file with suggested revisions in 
Microsoft([reg]) Access format and all accompanying documentation to 
Docket ID No. EPA-HQ-OAR-2007-0211 (through one of the methods 
described in the ADDRESSES section of this preamble). To answer 
questions on navigating through the data and to help expedite review of 
the revisions, it would also be helpful to submit revisions to EPA 
directly at RTR@epa.gov in addition to submitting them to the docket.
    5. If you are providing comments on a facility with multiple source 
categories, you need only submit one file for that facility, which 
should contain all suggested changes for all source categories at that 
facility.
    We strongly urge that all data revision comments be submitted in 
the form of updated Microsoft([reg]) Access files, which are provided 
on the http://www.epa.gov/ttn/atw/rrisk/rtrpg.html webpage. Data in the 

form of written descriptions or other electronic file formats will be 
difficult for EPA to translate into the necessary format in a timely 
manner.

V. Statutory and Executive Order Reviews

A. Executive Order 12866, Regulatory Planning and Review

    Under Executive Order 12866 (58 FR 51735, October 4, 1993), this 
action is a ``significant regulatory action.'' This action is a 
significant regulatory action because it raises novel legal and policy 
issues. Accordingly, EPA submitted this action to the Office of 
Management and Budget (OMB) for review under Executive Order 12866 and 
any changes made in response to OMB recommendations have been

[[Page 70557]]

documented in the docket for this action.

B. Paperwork Reduction Act

    This action does not impose any new information collection burden. 
This action is proposing no changes to the existing regulations 
affecting the eight source categories affected by today's proposal and 
will impose no additional information collection burden.
    Burden means the total time, effort, or financial resources 
expended by persons to generate, maintain, retain, or disclose or 
provide information to or for a Federal agency. This includes the time 
needed to review instructions; develop, acquire, install, and utilize 
technology and systems for the purposes of collecting, validating, and 
verifying information, processing and maintaining information, and 
disclosing and providing information; adjust the existing ways to 
comply with any previously applicable instructions and requirements; 
train personnel to be able to respond to a collection of information; 
search data sources; complete and review the collection of information; 
and transmit or otherwise disclose the information.
    An agency may not conduct or sponsor, and a person is not required 
to respond to a collection of information unless it displays a 
currently valid OMB control number. The OMB control numbers for EPA's 
regulations in 40 CFR are listed in 40 CFR part 9.

C. Regulatory Flexibility Act

    The Regulatory Flexibility Act (RFA) generally requires an agency 
to prepare a regulatory flexibility analysis of any rule subject to 
notice and comment rulemaking requirements under the Administrative 
Procedure Act or any other statute unless the agency certifies that the 
rule will not have a significant economic impact on a substantial 
number of small entities. Small entities include small businesses, 
small organizations, and small governmental jurisdictions.
    For purposes of assessing the impact of today's proposed action on 
small entities, small entity is defined as: (1) A small business whose 
parent company has fewer than 750 to 1,000 employees, depending on the 
size definition for the affected NAICS code (as defined by Small 
Business Administration size standards); (2) a small governmental 
jurisdiction that is a government of a city, county, town, school 
district, or special district with a population of less than 50,000; 
and (3) a small organization that is any not-for-profit enterprise 
which is independently owned and operated and is not dominant in its 
field.
    After considering the economic impact of today's proposed action on 
small entities, we certify that this action will not have a significant 
economic impact on a substantial number of small entities. The proposed 
action will not impose any requirements on small entities. We are 
proposing no further action at this time to revise the NESHAP. Today's 
proposed action requests public comments on the residual risk and 
technology review.
    We continue to be interested in the potential impacts of the 
proposed action on small entities and welcome comments on issues 
related to such impacts.

D. Unfunded Mandates Reform Act

    Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), Public 
Law 104-4, establishes requirements for Federal agencies to assess the 
effect of their regulatory actions on State, local, and tribal 
governments and the private sector. Under section 202 of the UMRA, EPA 
generally must prepare a written statement, including a cost-benefit 
analysis, for proposed and final rules with ``Federal mandates'' that 
may result in expenditures to State, local, and tribal governments, in 
the aggregate, or to the private sector, of $100 million or more in any 
one year. Before promulgating an EPA rule for which a written statement 
is needed, section 205 of the UMRA generally requires EPA to identify 
and consider a reasonable number of regulatory alternatives and adopt 
the least costly, most cost-effective, or least burdensome alternative 
that achieves the objectives of the rule. The provisions of section 205 
do not apply when they are inconsistent with applicable law. Moreover, 
section 205 allows EPA to adopt an alternative other than the least 
costly, most cost-effective, or least burdensome alternative if the 
Administrator publishes with the final rule an explanation why that 
alternative was not adopted. Before EPA establishes any regulatory 
requirements that may significantly or uniquely affect small 
governments, including tribal governments, it must have developed under 
section 203 of the UMRA a small government agency plan. The plan must 
provide for notifying potentially affected small governments, enabling 
officials of affected small governments to have meaningful and timely 
input in the development of EPA regulatory proposals with significant 
Federal intergovernmental mandates, and informing, educating, and 
advising small governments on compliance with the regulatory 
requirements.
    EPA has determined that the proposed action does not contain a 
Federal mandate that may result in expenditures of $100 million or more 
for State, local, and tribal governments in the aggregate, or to the 
private sector in any one year. The rule imposes no enforceable duty on 
State, local, or tribal governments, or the private sector. Thus, 
today's proposed action is not subject to the requirements of sections 
202 and 205 of the UMRA.
    In addition, EPA has determined that the proposed action contains 
no regulatory requirements that might significantly or uniquely affect 
small governments, because it contains no requirements that apply to 
such governments or impose obligations upon them.

E. Executive Order 13132, Federalism

    Executive Order 13132, entitled ``Federalism'' (64 FR 43255, August 
10, 1999), requires EPA to develop an accountable process to ensure 
``meaningful and timely input by State and local officials in the 
development of regulatory policies that have federalism implications.'' 
``Policies that have federalism implications'' is defined in the 
Executive Order to include regulations that have ``substantial direct 
effects on the States, on the relationship between the national 
government and the States, or on the distribution of power and 
responsibilities among the various levels of government.''
    This proposed action does not have federalism implications. It will 
not have substantial direct effects on the States, on the relationship 
between the national government and the States, or on the distribution 
of power and responsibilities among the various levels of government, 
as specified in Executive Order 13132. Thus, Executive Order 13132 does 
not apply to this proposed action.
    In the spirit of Executive Order 13132, and consistent with EPA 
policy to promote communications between EPA and State and local 
governments, EPA specifically solicits comment on this proposed action 
from State and local officials.

F. Executive Order 13175, Consultation and Coordination with Indian 
Tribal Governments

    Executive Order 13175, entitled ``Consultation and Coordination 
with Indian Tribal Governments'' (65 FR 67249, November 9, 2000), 
requires EPA to develop an accountable process to ensure ``meaningful 
and timely input by tribal officials in the development of

[[Page 70558]]

regulatory policies that have tribal implications.'' This proposed 
action does not have tribal implications as specified in Executive 
Order 13175. It will not have substantial direct effect on tribal 
governments, on the relationship between the Federal government and 
Indian tribes, or on the distribution of power and responsibilities 
between the Federal government and Indian tribes, as specified in 
Executive Order 13175. Thus, Executive Order 13175 does not apply to 
this proposed action.
    EPA specifically solicits additional comment on this proposed rule 
from tribal officials.

G. Executive Order 13045, Protection of Children From Environmental 
Health Risks and Safety Risks

    Executive Order 13045, ``Protection of Children from Environmental 
Health Risks and Safety Risks'' (62 FR 19885, April 23, 1997) applies 
to any rule that: (1) Is determined to be ``economically significant'' 
as defined under Executive Order 12866, and (2) concerns an 
environmental health or safety risk that EPA has reason to believe may 
have a disproportionate effect on children. If the regulatory action 
meets both criteria, the Agency must evaluate the environmental health 
or safety effects of the planned rule on children, and explain why the 
planned regulation is preferable to other potentially effective and 
reasonably feasible alternatives considered by the Agency.
    This proposed rule is not subject to the Executive Order because it 
is not economically significant as defined in Executive Order 12866, 
and because the Agency does not have reason to believe the 
environmental health or safety risks addressed by this action present a 
disproportionate risk to children because EPA's risk assessment 
demonstrates that the existing regulations are health protective.

H. Executive Order 13211, Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use

    This proposed rule is not a ``significant energy action'' as 
defined in Executive Order 13211 (66 FR 28355, May 22, 2001) because it 
is not likely to have a significant adverse effect on the supply, 
distribution, or use of energy. Further, we have concluded that this 
proposed rule is not likely to have any adverse energy effects.

I. National Technology Transfer and Advancement Act

    Section 12(d) of the National Technology Transfer and Advancement 
Act of 1995 (NTTAA), Public Law No. 104-113, 12(d) (15 U.S.C. 272 note) 
directs EPA to use voluntary consensus standards (VCS) in its 
regulatory activities, unless to do so would be inconsistent with 
applicable law or otherwise impractical. VCS are technical standards 
(e.g., materials specifications, test methods, sampling procedures, and 
business practices) that are developed or adopted by VCS bodies. The 
NTTAA directs EPA to provide Congress, through OMB, explanations when 
the Agency decides not to use available and applicable VCS.
    The proposed action does not involve technical standards. 
Therefore, EPA is not considering the use of any VCS. EPA welcomes 
comments on this aspect of the proposed rulemaking and, specifically, 
invites the public to identify potentially applicable VCS and to 
explain why such standards should be used in this proposed action.

J. Executive Order 12898: Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Populations

    Executive Order 12898 (59 FR 7629, February 16, 1994) establishes 
Federal executive policy on environmental justice. Its main provision 
directs Federal agencies, to the greatest extent practicable and 
permitted by law, to make environmental justice part of their mission 
by identifying and addressing, as appropriate, disproportionately high 
and adverse human health or environmental effects of their programs, 
policies, and activities on minority populations and low-income 
populations in the United States.
    EPA has determined that this proposed rule will not have 
disproportionately high and adverse human health or environmental 
effects on minority or low-income populations because it does not 
affect the level of protection provided to human health or the 
environment. This proposed rule would not relax the control measures on 
sources regulated by the rule and, therefore, would not cause emissions 
increases from these sources.

List of Subjects for 40 CFR Part 63

    Environmental protection, Administrative practice and procedures, 
Air pollution control, Hazardous substances, Intergovernmental 
relations, Reporting and recordkeeping requirements.

    Dated: December 6, 2007.
Stephen L. Johnson,
Administrator.
[FR Doc. E7-24076 Filed 12-11-07; 8:45 am]

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