[Federal Register Volume 72, Number 103 (Wednesday, May 30, 2007)]
[Proposed Rules]
[Pages 30168-30207]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E7-9706]



  Federal Register / Vol. 72, No. 103 / Wednesday, May 30, 2007 / 
Proposed Rules  

[[Page 30168]]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 82

[EPA-HQ-OAR-2002-0064; FRL-8316-7]
RIN 2060-AK26


Protection of Stratospheric Ozone: Listing of Substitutes for 
Ozone-Depleting Substances--n-Propyl Bromide in Adhesives, Coatings, 
and Aerosols

AGENCY: Environmental Protection Agency.

ACTION: Notice of Proposed Rulemaking.

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SUMMARY: Pursuant to the U.S. Environmental Protection Agency's (EPA or 
``we'') Significant New Alternatives Policy (SNAP) program, this action 
proposes to list n-propyl bromide (nPB) as an unacceptable substitute 
for methyl chloroform, chlorofluorocarbon (CFC)-113, and 
hydrochlorofluorocarbon (HCFC)-141b when used in adhesives or in 
aerosol solvents because nPB in these end uses poses unacceptable risks 
to human health when compared with other substitutes that are 
available. In addition, EPA takes comment on alternate options that 
would find nPB acceptable subject to use conditions in adhesives or in 
aerosol solvents. This action also proposes to list nPB as acceptable, 
subject to use conditions, as a substitute for methyl chloroform, CFC-
113, and hydrochlorofluorocarbon (HCFC)-141b in the coatings end use. 
This proposal supersedes EPA's proposal of June 3, 2003 on the 
acceptability of nPB as a substitute for ozone-depleting substances for 
aerosols and adhesives.

DATES: Comments must be received in writing by July 30, 2007. Under the 
Paperwork Reduction Act, comments on the information collection 
provisions must be received by the Office of Management and Budget 
(OMB) on or before June 29, 2007. Any person interested in requesting a 
public hearing, must submit such request on or before June 29, 2007. If 
a public hearing is requested, a separate notice will be published 
announcing the date and time of the public hearing and the comment 
period will be extended until 30 days after the public hearing to allow 
rebuttal and supplementary information regarding any material presented 
at the public hearing. Inquiries regarding a public hearing should be 
directed to the contact person listed below.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
OAR-2002-0064, by one of the following methods:
     http://www.regulations.gov. Follow the on-line 
instructions for submitting comments.
     E-mail: [email protected].
     Mail: Air and Radiation Docket, Environmental Protection 
Agency, Mailcode 6102T, 1200 Pennsylvania Ave., NW., Washington DC 
20460, Attention Docket ID No. EPA-HQ-OAR-2002-0064. In addition, 
please mail a copy of your comments on the information collection 
provisions to the Office of Information and Regulatory Affairs, Office 
of Management and Budget (OMB), Attn: Desk Officer for EPA, 725 17th 
St., NW., Washington, DC 20503.
     Hand Delivery: EPA Docket Center, (EPA/DC) EPA West, Room 
3334, 1301 Constitution Ave., NW., Washington, DC, Attention Docket ID 
No. EPA-HQ-OAR-2002-0064. Such deliveries are only accepted during the 
Docket's normal hours of operation, and special arrangements should be 
made for deliveries of boxed information.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-
2002-0064. 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 www.regulations.gov 
or e-mail. The http://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 instructions on submitting comments, go to 
Section I.B. of the SUPPLEMENTARY INFORMATION section of this document.
    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, i.e., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, is not placed on the Internet and will be 
publicly available only in hard copy form. Publicly available docket 
materials are available either electronically in http://www.regulations.gov or in hard copy at the Air and Radiation Docket, 
EPA/DC, EPA West, Room 3334, 1301 Constitution Ave., 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 
Air and Radiation Docket is (202) 566-1742.

FOR FURTHER INFORMATION CONTACT: Margaret Sheppard, Stratospheric 
Protection Division, Office of Atmospheric Programs, Mail Code 6205J, 
Environmental Protection Agency, 1200 Pennsylvania Ave., NW., 
Washington, DC 20460; telephone number (202) 343-9163; fax number (202) 
343-2362 e-mail address: [email protected]. Notices and 
rulemakings under the SNAP program are available on EPA's Stratospheric 
Ozone World Wide Web site at http://www.epa.gov/ozone/snap/regs.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. General Information
    A. Does this action apply to me?
    B. What should I consider as I prepare my comments for EPA?
    C. What acronyms and abbreviations are used in the preamble?
II. How does the Significant New Alternatives Policy (SNAP) program 
work?
    A. What are the statutory requirements and authority for the 
SNAP program?
    B. How do the regulations for the SNAP program work?
    C. Where can I get additional information about the SNAP 
program?
III. What is EPA proposing today?
    A. What is n-propyl bromide?
    B. What industrial end uses are included in our proposed 
decision?
    C. What is the proposed text for EPA's listing decisions?
    D. What does an unacceptability determination on adhesives and 
aerosols mean?
    E. What is the scope of the proposed determination for coatings?

[[Page 30169]]

IV. What criteria did EPA consider in preparing this proposal?
    A. Availability of Alternatives to Ozone-Depleting Substances
    B. Impacts on the Atmosphere and Local Air Quality
    C. Ecosystem and Other Environmental Impacts
    D. Flammability and Fire Safety
    E. Health impacts and exposure
V. How did EPA assess impacts on human health?
    A. Newly Available Exposure Data
    B. Newly Available Data on Health Effects
    C. Evaluation of Acceptable Exposure Levels for the Workplace
    D. Other Analyses of nPB Toxicity
    E. Community Exposure Guideline
VI. What listing is EPA proposing for each end use, and why?
    A. Aerosol Solvents
    B. Adhesives
    C. Coatings
VII. What other regulatory options did EPA consider?
    A. Alternative Option for Comment: Acceptable With Use 
Conditions Requiring Exposure Limit and Monitoring
    B. Regulatory Options Where nPB Would Be Acceptable With Use 
Conditions Requiring Specific Equipment
VIII. What are the anticipated costs of this regulation to the 
regulated community?
IX. How do the decisions for EPA's June 2003 proposal compare to 
those for this proposal?
X. How can I use nPB as safely as possible?
XI. 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 and Safety Risks
    H. Executive Order 13211: Actions That Significantly Affect 
Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act
XII. References

I. General Information

A. Does this action apply to me?

    This proposed rule would regulate the use of n-propyl bromide as an 
aerosol solvent and as a carrier solvent in adhesives and coatings. 
Businesses in these end uses that currently might be using nPB, or 
might want to use it in the future, include:
     Businesses that manufacture electronics or computer 
equipment.
     Businesses that require a high level of cleanliness in 
removing oil, grease, or wax, such as for aerospace applications or for 
manufacture of optical equipment.
     Foam fabricators that glue pieces of polyurethane foam 
together or foam cushion manufacturers that glue fabric around a 
cushion.
     Furniture manufacturers that use adhesive to attach wood 
parts to floors, tables and counter tops.
     A company that manufactures ammunition for the U.S. 
Department of Defense. Regulated entities may include:

  Table 1.--Potentially Regulated Entities, by North American Industrial Classification System (NAICS) Code or
                                                    Subsector
----------------------------------------------------------------------------------------------------------------
                                                 NAICS code or
                   Category                        subsector            Description of regulated entities
----------------------------------------------------------------------------------------------------------------
Industry......................................             331  Primary Metal Manufacturing.
Industry......................................             332  Fabricated Metal Product Manufacturing.
Industry/Military.............................          332992  Small Arms Ammunition Manufacturing.
Industry......................................             333  Machinery Manufacturing.
Industry......................................             334  Computer and Electronic Product Manufacturing.
Industry......................................             335  Equipment Appliance, and Component
                                                                 Manufacturing.
Industry......................................             336  Transportation Equipment Manufacturing.
Industry......................................             337  Furniture and Related Product Manufacturing.
Industry......................................             339  Miscellaneous Manufacturing.
Industry......................................          326150  Urethane and Other Foam Product (except
                                                                 Polystyrene) Manufacturing.
----------------------------------------------------------------------------------------------------------------

    This table is not intended to be exhaustive, but rather a guide 
regarding entities likely to be regulated by this action. If you have 
any questions about whether this action applies to a particular entity, 
consult the person listed in the preceding section, FOR FURTHER 
INFORMATION CONTACT.

B. What should I consider as I prepare my comments for EPA?

    1. Submitting Confidential Business Information (CBI). Do not 
submit this information to EPA through www.regulations.gov or e-mail. 
Clearly mark the part or all of the information that you claim to be 
CBI. For CBI information in a disk or CD ROM that you mail to EPA, 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. Information so marked will not be 
disclosed except in accordance with procedures set forth in 40 CFR part 
2.
    2. Tips for Preparing Your Comments. When submitting comments, 
remember to:
     Identify the rulemaking by docket number and other 
identifying information (subject heading, Federal Register (FR) date 
and page number).
     Follow directions--The agency may ask you to respond to 
specific questions or organize comments by referencing a Code of 
Federal Regulations (CFR) part or section number.
     Explain why you agree or disagree; suggest alternatives 
and substitute language for your requested changes.
     Describe any assumptions and provide any technical 
information and/or data that you used.
     If you estimate potential costs or burdens, explain how 
you arrived at your estimate in sufficient detail to allow for it to be 
reproduced.
     Provide specific examples to illustrate your concerns, and 
suggest alternatives.
     Explain your views as clearly as possible, avoiding the 
use of profanity or personal threats.
     Make sure to submit your comments by the comment period 
deadline identified.

C. What acronyms and abbreviations are used in the preamble?

    Below is a list of acronyms and abbreviations used in this 
document.

8-hr--eight hour
ACGIH--American Conference of Governmental Industrial Hygienists
AEL--acceptable exposure limit

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ASTM--American Society for Testing and Materials
BMD--benchmark dose
BMDL--benchmark dose lowerbound, the lower 95%-confidence level 
bound on the dose/exposure associated with the benchmark response
BSOC--Brominated Solvents Consortium
CAA--Clean Air Act
CAS Reg. No--Chemical Abstracts Service Registry Identification 
Number
CBI--Confidential Business Information
CEG--community exposure guideline
CERHR--Center for the Evaluation of Risks to Human Reproduction
CFC-113--the ozone-depleting chemical 1,1,2-trifluoro-1,2,2-
trichloroethane, C2Cl3F3, CAS Reg. 
No. 76-13-1
CFC--chlorofluorocarbon
cfm--cubic feet per minute
CFR--Code of Federal Regulations
CNS--central nervous system
DNA--deoxyribonucleic acid
EDSTAC--The Endocrine Disruptor Screening and Testing Advisory 
Committee
EPA--the United States Environmental Protection Agency
FR--Federal Register
GWP--global warming potential
HCFC-141b--the ozone-depleting chemical 1,1-dichloro-1-fluoroethane, 
CAS Reg. No. 1717-00-6
HCFC-225ca/cb--the commercial mixture of the two ozone-depleting 
chemicals 3,3-dichloro-1,1,1,2,2-pentafluoropropane, CAS Reg. No. 
422-56-0 and 1,3-dichloro-1,1,2,2,3-pentafluoropropane, CAS Reg. No. 
507-55-1
HCFC--hydrochlorofluorocarbon
HEC--human equivalent concentration
HFC-245fa--the chemical 1,1,3,3,3-pentafluoropropane, CAS Reg. No. 
460-73-1
HFC-365mfc--the chemical 1,1,1,3,3-pentafluorobutane, CAS Reg. No. 
405-58-6
HFC-4310mee--the chemical 1,1,1,2,3,4,4,5,5,5-decafluoropentane, CAS 
Reg. No. 138495-42-8
HFC--hydrofluorocarbon
HFE--hydrofluoroether
HHE--health hazard evaluation
ICF--ICF Consulting
ICR--Information Collection Request
iPB--isopropyl bromide, C3H7Br, CAS Reg. No. 
75-26-3, an isomer of n-propyl bromide; also called 2-bromopropane 
or 2-BP
Koc--organic carbon partition coefficient, for 
determining the tendency of a chemical to bind to organic carbon in 
soil
LC50--the concentration at which 50% of test animals die
LOAEL--Lowest Observed Adverse Effect Level
Log Kow--logarithm of the octanol-water partition 
coefficient, for determining the tendency of a chemical to 
accumulate in lipids or fats instead of remaining dissolved in water
mg/l--milligrams per liter
MSDS--Material Safety Data Sheet
NAICS--North American Industrial Classification System
NIOSH--National Institute for Occupational Safety and Health
NOAEL--No Observed Adverse Effect Level
NOEL--No Observed Effect Level
nPB--ln-propyl bromide, C3H7Br, CAS Reg. No. 
106-94-5; also called 1-bromopropane or 1-BP
NPRM--Notice of Proposed Rulemaking
NTP--National Toxicology Program
NTTAA--National Technology Transfer and Advancement Act
ODP--ozone depletion potential
ODS--ozone-depleting substance
OEHHA--Office of Environmental Health Hazard Assessment of the 
California Environmental Protection Agency
OMB--U.S. Office of Management and Budget
OSHA--the United States Occupational Safety and Health 
Administration
PCBTF--parachlorobenzotrifluoride, CAS Reg. No. 98-56-6
PEL--Permissible Exposure Limit ppm-parts per million
RCRA--Resource Conservation and Recovery Act
RFA--Regulatory Flexibility Act
RfC--reference concentration
SIP--state implementation plan
SNAP--Significant New Alternatives Policy
TCA--the ozone-depleting chemical 1,1,1-trichloroethane, CAS Reg. 
No. 71-55-6; also called methyl chloroform, MCF, or 1,1,1
TCE--the chemical 1,1,2-trichloroethene, CAS Reg. No. 79-01-6, 
C2Cl3H; also call trichloroethylene
TERA--Toxicological Excellence for Risk Assessment
TLV--Threshold Limit Value(tm)
TSCA--Toxic Substances Control Act
TWA--time-weighted average
UMRA--Unfunded Mandates Reform Act
U.S.C.--United States Code
VMSs--volatile methyl siloxanes
VOC--volatile organic compound

II. How does the Significant New Alternatives Policy (SNAP) program 
work?

A. What are the statutory requirements and authority for the SNAP 
program?

    Section 612 of the Clean Air Act (CAA) authorizes EPA to develop a 
program for evaluating alternatives to ozone-depleting substances, 
referred to as the Significant New Alternatives Policy (SNAP) program. 
The major provisions of section 612 are:
     Rulemaking--Section 612(c) requires EPA to promulgate 
rules making it unlawful to replace any class I (chlorofluorocarbon, 
halon, carbon tetrachloride, methyl chloroform, and 
hydrobromofluorocarbon) or class II (hydrochlorofluorocarbon) substance 
with any substitute that the Administrator determines may present 
adverse effects to human health or the environment where the 
Administrator has identified an alternative that (1) reduces the 
overall risk to human health and the environment, and (2) is currently 
or potentially available.
     Listing of Unacceptable/Acceptable Substitutes--Section 
612(c) also requires EPA to publish a list of the substitutes 
unacceptable for specific uses. We must publish a corresponding list of 
acceptable alternatives for specific uses.
     Petition Process--Section 612(d) grants the right to any 
person to petition EPA to add a substitute to or delete a substitute 
from the lists published in accordance with section 612(c). EPA has 90 
days to grant or deny a petition. Where the Agency grants the petition, 
we must publish the revised lists within an additional six months.
     90-day Notification--Section 612(e) requires EPA to 
require any person who produces a chemical substitute for a class I 
substance to notify the Agency not less than 90 days before new or 
existing chemicals are introduced into interstate commerce for 
significant new uses as substitutes for a class I substance. The 
producer must also provide the Agency with the producer's health and 
safety studies on such substitutes.
     Outreach--Section 612(b)(1) states that the Administrator 
shall seek to maximize the use of federal research facilities and 
resources to assist users of class I and II substances in identifying 
and developing alternatives to the use of such substances in key 
commercial applications.
     Clearinghouse--Section 612(b)(4) requires the Agency to 
set up a public clearinghouse of alternative chemicals, product 
substitutes, and alternative manufacturing processes that are available 
for products and manufacturing processes which use class I and II 
substances.

B. How do the regulations for the SNAP program work?

    On March 18, 1994, EPA published the original rulemaking (59 FR 
13044) that described the process for administering the SNAP program 
and issued the first acceptability lists for substitutes in the major 
industrial use sectors. These sectors include: Refrigeration and air 
conditioning; foam blowing; solvents cleaning; fire suppression and 
explosion protection; sterilants; aerosols; adhesives, coatings and 
inks; and tobacco expansion. These sectors comprise the principal 
industrial sectors that historically consumed large volumes of ozone-
depleting substances.
    Anyone who plans to market or produce a substitute for an ozone-
depleting substance (ODS) in one of the eight major industrial use 
sectors must provide the Agency with health and safety studies on the 
substitute at least 90 days before introducing it into

[[Page 30171]]

interstate commerce for significant new use as an alternative. This 
requirement applies to the person planning to introduce the substitute 
into interstate commerce, typically chemical manufacturers, but may 
also include importers, formulators or end-users when they are 
responsible for introducing a substitute into commerce.
    The Agency has identified four possible decision categories for 
substitutes: Acceptable; acceptable subject to use conditions; 
acceptable subject to narrowed use limits; and unacceptable. Use 
conditions and narrowed use limits are both considered ``use 
restrictions'' and are explained below. Substitutes that are deemed 
acceptable with no use restrictions (no use conditions or narrowed use 
limits) can be used for all applications within the relevant sector 
end-use. Substitutes that are acceptable subject to use restrictions 
may be used only in accordance with those restrictions. It is illegal 
to replace an ODS with a substitute listed as unacceptable.
    After reviewing a substitute, the Agency may make a determination 
that a substitute is acceptable only if certain conditions of use are 
met to minimize risks to human health and the environment. We describe 
such substitutes as ``acceptable subject to use conditions.'' If you 
use these substitutes without meeting the associated use conditions, 
you use these substitutes in an unacceptable manner and you could be 
subject to enforcement for violation of section 612 of the Clean Air 
Act.
    For some substitutes, the Agency may permit a narrowed range of use 
within a sector. For example, we may limit the use of a substitute to 
certain end-uses or specific applications within an industry sector or 
may require a user to demonstrate that no other acceptable end uses are 
available for their specific application. We describe these substitutes 
as ``acceptable subject to narrowed use limits.'' If you use a 
substitute that is acceptable subject to narrowed use limits, but use 
it in applications and end-uses which are not consistent with the 
narrowed use limit, you are using these substitutes in an unacceptable 
manner and you could be subject to enforcement for violation of section 
612 of the Clean Air Act.
    The Agency publishes its SNAP program decisions in the Federal 
Register. For those substitutes that are deemed acceptable subject to 
use restrictions (use conditions and/or narrowed use limits), or for 
substitutes deemed unacceptable, we first publish these decisions as 
proposals to allow the public opportunity to comment, and we publish 
final decisions as final rulemakings. In contrast, we publish 
substitutes that are deemed acceptable with no restrictions in 
``notices of acceptability,'' rather than as proposed and final rules. 
As described in the rule implementing the SNAP program (59 FR 13044), 
we do not believe that rulemaking procedures are necessary to list 
alternatives that are acceptable without restrictions because such 
listings neither impose any sanction nor prevent anyone from using a 
substitute.
    Many SNAP listings include ``comments'' or ``further information.'' 
These statements provide additional information on substitutes that we 
determine are unacceptable, acceptable subject to narrowed use limits, 
or acceptable subject to use conditions. Since this additional 
information is not part of the regulatory decision, these statements 
are not binding for use of the substitute under the SNAP program. 
However, regulatory requirements listed in this column are binding 
under other programs. The further information does not necessarily 
include all other legal obligations pertaining to the use of the 
substitute. However, we encourage users of substitutes to apply all 
statements in the ``Further Information'' column in their use of these 
substitutes. In many instances, the information simply refers to sound 
operating practices that have already been identified in existing 
industry and/or building-code standards. Thus, many of the comments, if 
adopted, would not require the affected industry to make significant 
changes in existing operating practices.

C. Where can I get additional information about the SNAP program?

    For copies of the comprehensive SNAP lists of substitutes or 
additional information on SNAP, look at EPA's Ozone Depletion World 
Wide Web site at http://www.epa.gov/ozone/snap/lists/index.html. For 
more information on the Agency's process for administering the SNAP 
program or criteria for evaluation of substitutes, refer to the SNAP 
final rulemaking published in the Federal Register on March 18, 1994 
(59 FR 13044), codified at Code of Federal Regulations at 40 CFR part 
82, subpart G. You can find a complete chronology of SNAP decisions and 
the appropriate Federal Register citations at http://www.epa.gov/ozone/snap/chron.html.

III. What is EPA proposing today?

    In this action, EPA proposes to list n-propyl bromide (nPB) as (1) 
unacceptable for use as a substitute for CFC-113,\1\ methyl chloroform 
\2\ and HCFC-141b \3\ in the adhesive and aerosol solvent end uses; and 
(2) acceptable subject to use conditions (limited to coatings at 
facilities that, as of May 30, 2007, have provided EPA with information 
demonstrating their ability to maintain acceptable workplace exposures) 
as a substitute for methyl chloroform, CFC-113, and HCFC-141b in the 
coatings end use. This Notice of Proposed Rulemaking (NPRM) supersedes 
the NPRM published on June 3, 2003 (68 FR 33284) for aerosol solvents 
and adhesives.
---------------------------------------------------------------------------

    \1\ CFC-113 is also referred to as Freon-113, or 1,1,2-
trifluoro-1,2,2-trichloroethane. Its CAS Reg. No. is 76-13-1.
    \2\ Methyl chloroform is also referred to as 1,1,1-
trichloroethane, TCA, MCF, or 1,1,1. Its CAS Reg. No. is 71-55-6.
    \3\ HCFC-141b is also referred to as 1,1-dichloro-1-
fluoroethane. Its CAS Reg. No. is 1717-00-6.
---------------------------------------------------------------------------

A. What is n-propyl bromide?

    n-propyl bromide (nPB), also called 1-bromopropane, is a non-
flammable organic solvent with a strong odor. Its chemical formula is 
C3H7Br. Its identification number in Chemical 
Abstracts Service's registry (CAS Reg. No.) is 106-94-5. nPB is used to 
remove wax, oil, and grease from electronics, metal, and other 
materials. It also is used as a carrier solvent in adhesives. Some 
brand names of products using nPB are: Abzol[supreg], EnSolv[supreg], 
and Solvon[supreg] cleaners; Pow-R-Wash[supreg] NR Contact Cleaner, 
Superkleen Flux Remover 2311 and LPS NoFlash NU Electro Contact Cleaner 
aerosols; and Whisper Spray and Fire Retardant Soft Seam 6460 
adhesives.

B. What industrial end uses are included in our proposed decision?

    This proposal addresses the use of n-propyl bromide in the aerosol 
solvent end use of the aerosol sector and the adhesives and coatings 
end uses in the adhesives, coatings, and inks sector as discussed 
below. EPA is issuing a decision on the use of nPB in metals, 
electronics, and precision cleaning in a separate final rule. EPA has 
insufficient information for ruling on other end uses or sectors where 
nPB might be used (e.g., inks, foam blowing, fire suppression).
1. Aerosol Solvents
    We understand that nPB is being used as an aerosol solvent in:
     Lubricants, coatings, or cleaning fluids for electrical or 
electronic equipment;
    Lubricants, coatings, or cleaning fluids for aircraft maintenance; 
or

[[Page 30172]]

     Spinnerrette lubricants and cleaning sprays used in the 
production of synthetic fibers.
2. Adhesives
    Types of adhesives covered under the SNAP program are those that 
formerly used methyl chloroform, specifically, adhesives for laminates, 
flexible foam, hardwood floors, tire patches, and metal to rubber 
adhesives. Of these applications, nPB-based adhesives have been used 
most widely in spray adhesives used in manufacture of foam cushions, 
and to a lesser degree in laminate adhesives.
3. Coatings
    The SNAP program regulates the use of carrier solvents in durable 
coatings, including paints, varnishes, and aerospace coatings (59 FR 
13118). The SNAP program currently does not regulate carrier solvents 
in lubricant coatings, such as silicone coatings used on medical 
equipment (59 FR 13119). Methyl chloroform has been used as a carrier 
solvent in coatings, and to a much lesser degree, HCFC-141b also has 
been a carrier solvent. This rule responds to a submission from a 
facility that is substituting methyl chloroform with nPB as an 
ammunition coating (sealant).

C. What is the proposed text for EPA's listing decisions?

    In the proposed regulatory text at the end of this document, you 
will find our proposed decisions for those end uses for which we have 
proposed nPB as unacceptable or acceptable subject to use conditions. 
The proposed conditions listed in the ``Use Conditions'' column would 
be enforceable while information contained in the ``Further 
Information'' column of those tables provides additional 
recommendations on the safe use of nPB. Our proposed decisions for each 
end use are summarized below in tables 2 through 4.

Proposed Listings

                              Table 2.--Aerosols Proposed Unacceptable Substitutes
----------------------------------------------------------------------------------------------------------------
              End Use                       Substitute                 Decision           Further information
----------------------------------------------------------------------------------------------------------------
Aerosol solvents..................  n-propyl bromide (nPB) as   Unacceptable.........  EPA finds unacceptable
                                     a substitute for CFC-113,                          risks to human health in
                                     HCFC-141b, and methyl                              this end use compared to
                                     chloroform.                                        other available
                                                                                        alternatives. nPB, also
                                                                                        known as 1-bromopropane,
                                                                                        is Number 106-94-5 in
                                                                                        the CAS Registry.
----------------------------------------------------------------------------------------------------------------


                    Table 3.--Adhesives, Coatings, and Inks Proposed Unacceptable Substitutes
----------------------------------------------------------------------------------------------------------------
              Enduse                        Substitute                 Decision           Further information
----------------------------------------------------------------------------------------------------------------
Adhesives.........................  n-propyl bromide (nPB) as   Unacceptable.........  EPA finds unacceptable
                                     a substitute for CFC-113,                          risks to human health in
                                     HCFC-141b, and methyl                              this end use compared to
                                     chloroform.                                        other available
                                                                                        alternatives. nPB, also
                                                                                        known as 1-bromopropane,
                                                                                        is Number 106-94-5 in
                                                                                        the CAS Registry.
----------------------------------------------------------------------------------------------------------------


   Table 4.--Adhesives, Coatings, and Inks Substitutes That Are Proposed Acceptable Subject to Use Conditions
----------------------------------------------------------------------------------------------------------------
       End Use             Substitute            Decision            Use conditions        Further information
----------------------------------------------------------------------------------------------------------------
Coatings............  n-propyl bromide     Acceptable subject   Use is limited to        EPA recommends the use
                       (nPB) as a           to use conditions.   coatings facilities      of personal protective
                       substitute for                            that, as of May 30,      equipment, including
                       methyl chloroform,                        2007, have provided      chemical goggles,
                       CFC-113, and HCFC-                        EPA information          flexible laminate
                       141b.                                     demonstrating their      protective gloves and
                                                                 ability to maintain      chemical-resistant
                                                                 acceptable workplace     clothing.
                                                                 exposures.              EPA expects that all
                                                                                          users of nPB would
                                                                                          comply with any final
                                                                                          Permissible Exposure
                                                                                          Limit that the
                                                                                          Occupational Safety
                                                                                          and Health
                                                                                          Administration issues
                                                                                          in the future under 42
                                                                                          U.S.C. 7610(a).
                                                                                         nPB, also known as 1-
                                                                                          bromopropane, is
                                                                                          Number 106-94-5 in the
                                                                                          CAS Registry.
----------------------------------------------------------------------------------------------------------------
Note: As of May 30, 2007, the Lake City Army Ammunition Plant is the only facility using nPB in coatings that
  has provided information to EPA that meets this condition.

D. What does an unacceptability determination on adhesives and aerosols 
mean?

    In this action, EPA is proposing to find nPB unacceptable as a 
substitute for methyl chloroform, CFC-113, and HCFC-141b for use as a 
carrier solvent in adhesives and as an aerosol solvent. If this 
proposal were to become final, it would be illegal to use nPB or blends 
of nPB and other solvents in adhesives or in aerosol solvent 
formulations as a substitute for ozone-depleting substances.

E. What is the scope of the proposed determination for coatings?

    We propose to list nPB as an acceptable substitute, subject to use 
conditions, for methyl chloroform, CFC-113, and HCFC-141b in coatings 
for facilities that, as of May 30, 2007, have

[[Page 30173]]

provided EPA information demonstrating their ability to maintain 
acceptable workplace exposures. EPA has received a petition to allow 
use of nPB for the ammunition coating application at Lake City Army 
Ammunition Plant. This is the only coatings application or facility for 
which EPA has exposure and usage data demonstrating an ability to 
maintain workplace exposure levels below even the minimum level of the 
range of exposures that EPA is considering to be potentially acceptable 
(i.e., 17 to 30 ppm) (see section IV.E for an evaluation of the health 
risks associated with nPB). If other facilities are interested in using 
nPB as a substitute for methyl chloroform, CFC-113, or HCFC-141b in 
their coatings application, or if a person wishes to market nPB for 
such use, then the interested party would need to make a submission 
under the SNAP program.

IV. What criteria did EPA consider in preparing this proposal?

    In the original rule implementing the SNAP program (March 18, 1994; 
59 FR 13044, at 40 CFR 82.180(a)(7)), the Agency identified the 
criteria we use in determining whether a substitute is acceptable or 
unacceptable as a replacement for class I or II compounds:
    (i) Atmospheric effects and related health and environmental 
impacts;
    [e.g., ozone depletion potential]
    (ii) General population risks from ambient exposure to compounds 
with direct toxicity and to increased ground-level ozone;
    (iii) Ecosystem risks [e.g., bioaccumulation, impacts on surface 
and groundwater];
    (iv) Occupational risks;
    (v) Consumer risks;
    (vi) Flammability; and
    (vii) Cost and availability of the substitute.
    In this review, EPA considered all the criteria above. However, n-
propyl bromide is used in industrial applications such as electronics 
cleaning or spray adhesives used in foam fabrication. In those consumer 
products made using nPB, such as a piece of furniture or a computer, 
the nPB would have evaporated long before a consumer would purchase the 
item. Therefore, we believe there is no consumer exposure risk to 
evaluate in the end uses we evaluated for this rule.
    Section 612(c) of the Clean Air Act directs EPA to publish a list 
of replacement substances (``substitutes'') for class I and class II 
ozone depleting substances based on whether the Administrator 
determines they are safe (when compared with other currently or 
potentially available substitutes) for specific uses or are to be 
prohibited for specific uses. EPA must compare the risks to human 
health and the environment of a substitute to the risks associated with 
other substitutes that are currently or potentially available. In 
addition, EPA also considers whether the substitute for class I and 
class II ODSs ``reduces the overall risk to human health and the 
environment'' compared to the ODSs being replaced. Our evaluation is 
based on the end use; for example, we compared nPB as a carrier solvent 
in adhesives to other available or potentially available adhesive 
alternatives.
    Although EPA does not judge the effectiveness of an alternative for 
purposes of determining whether it is acceptable, we consider 
effectiveness when determining whether alternatives that pose less risk 
are available in a particular application within an end use. There are 
a wide variety of acceptable alternatives listed for aerosol solvents, 
but not all may be appropriate for a specific application because of 
differences in materials compatibility, flammability, degree of 
cleanliness required, local environmental requirements, and other 
factors.
    EPA evaluated each of the criteria separately and then considered 
overall risk to human health and the environment in comparison to other 
available or potentially available alternatives. We concluded that 
overall, environmental risks were not sufficient to find nPB 
unacceptable in any of the evaluated end uses. However, the overall 
risks to human health, and particularly the risks to worker health, are 
sufficiently high in the adhesive and aerosol solvent end uses to 
warrant our proposal to find nPB unacceptable.

A. Availability of Alternatives to Ozone-Depleting Substances

    Other alternatives are available in each end use considered in this 
proposal. Examples of other available alternatives for aerosol solvents 
that have already been found acceptable or acceptable subject to use 
conditions under the SNAP program include water-based formulations, 
alcohols, ketones, esters, ethers, terpenes, HCFC-141b, HCFC-225ca/cb, 
hydrofluoroethers (HFEs), hydrofluorocarbon (HFC)-4310mee, HFC-365mfc, 
HFC-245fa, hydrocarbons, trans-1,2-dichloroethylene, methylene 
chloride, trichloroethylene \4\ (TCE), perchloroethylene \5\, and 
parachlorobenzotrifluoride (PCBTF). Of these, hydrocarbons, alcohols, 
blends of trans-1,2-dichloroethylene and HFEs or HFCs, and HCFC-225ca/
cb are most likely to be used in the same applications as nPB. nPB is 
already commercially available in aerosols. Its use is primarily for 
electrical contact cleaning, with some use for benchtop cleaning 
applications (Williams, 2005).
---------------------------------------------------------------------------

    \4\ Also called trichlorethene or TCE, 
C2Cl3H, CAS Reg. No. 79-01-6.
    \5\ Also called PERC, tetrachloroethylene, or tetrachloroethene, 
C2Cl4, CAS Reg. No. 127-18-4.
---------------------------------------------------------------------------

    Many alternatives are also available for use in adhesives, 
coatings, and inks: Water-based formulations, high solid formulations, 
alcohols, ketones, esters, ethers, terpenes, HFEs, hydrocarbons, trans-
1,2-dichloroethylene, chlorinated solvents, PCBTF, and a number of 
alternative technologies (e.g., powder, hot melt, thermoplastic plasma 
spray, radiation-cured, moisture-cured, chemical-cured, and reactive 
liquid). Of these, the alternative adhesives most likely to be used in 
the same applications as nPB are water-based formulations, adhesives 
with methylene chloride, and flammable adhesives with acetone (IRTA, 
2000). nPB is already used in adhesives, and particularly in foam 
fabrication and in constructing seating for aircraft (IRTA, 2000; 
Seilheimer, 2001).
    To our knowledge, nPB is potentially available as a carrier solvent 
in coatings, but has not yet been commercialized, except for use by one 
facility, the Lake City Army Ammunition Plant. The Lake City Army 
Ammunition Plant evaluated twenty-nine carrier solvent alternatives to 
methyl chloroform and determined that nPB is the only satisfactory 
alternative for their application given the current process at that 
facility (Harper, 2005).

B. Impacts on the Atmosphere and Local Air Quality

    As discussed in the June, 2003 proposal, nPB emissions from the 
continental United States are estimated to have an ozone depletion 
potential (ODP) of approximately 0.013-0.018, (Wuebbles, 2002), lower 
than that of the ozone depletion potential of the substances that nPB 
would replace--CFC-113 (ODP = 1.0), and methyl chloroform and HCFC-141b 
(ODPs = 0.12) (WMO, 2002). Some other acceptable alternatives for these 
ODSs also have low ODPs. For example, HCFC-225ca/cb has an ODP of 0.02-
0.03 (WMO, 2002) and is acceptable as an aerosol solvent. There are 
other acceptable solvents for aerosols, adhesives, and coatings that 
essentially have no ODP--aqueous cleaners, HFEs, HFC-4310mee, HFC-
365mfc, HFC-245fa, hydrocarbons, volatile methyl siloxanes (VMSs), 
methylene chloride, TCE, perchloroethylene, and PCBTF.

[[Page 30174]]

Based on this information, we do not believe the use of nPB within the 
U.S., and within the end-uses reviewed in this rulemaking, poses a 
significantly greater risk to the ozone layer than other available 
substitutes.
    Comments on the June 2003 NPRM expressed concern that other 
countries, particularly those in equatorial regions, might assume that 
nPB does not pose a danger to the stratospheric ozone layer if the U.S. 
EPA's SNAP program finds nPB acceptable (Linnell, 2003; Steminiski, 
2003). Because the ODP for nPB is higher when used in the tropics,\6\ 
we recognize the concerns raised by these commenters. However, EPA is 
regulating use in the U.S. and cannot dictate actions taken by other 
countries. We believe the more appropriate forum to address this 
concern is through the Parties to the Montreal Protocol. At the most 
recent Meeting of the Parties, the Parties made the following decision 
with regard to n-propyl bromide, in order to ``allow Parties to 
consider further steps regarding n-propyl bromide, in the light of 
available alternatives'' (Decision XVIII/11):
---------------------------------------------------------------------------

    \6\ nPB emissions in the tropics have an ODP of 0.071 to 0.100; 
the portions of the U.S. outside the continental U.S., such as 
Alaska, Hawaii, Guam, and the U.S. Virgin Islands, contain less than 
1 percent of the U.S.'s businesses in industries that could use nPB. 
Thus, their potential impact on the ozone layer must be 
significantly less than that of the already low impact from nPB 
emissions in the continental U.S. (U.S. Economic Census, 2002a 
through f).
---------------------------------------------------------------------------

    1. To request the Scientific Assessment Panel to update existing 
information on the ozone depletion potential of n-propyl bromide, 
including ozone depleting potential depending on the location of the 
emissions and the season in the hemisphere at that location;
    2. To request the Technology and Economic Assessment Panel to 
continue its assessment of global emissions of n-propyl bromide, * * * 
paying particular attention to:
    (a) Obtaining more complete data on production and uses of n-propyl 
bromide as well as emissions of n-propyl bromide from those sources;
    (b) Providing further information on the technological and 
economical availability of alternatives for the different use 
categories of n-propyl bromide and information on the toxicity of and 
regulations on the substitutes for n-propyl bromide;
    (c) Presenting information on the ozone depletion potential of the 
substances for which n-propyl bromide is used as a replacement;
    3. To request that the Technology and Economic Assessment Panel 
prepare a report on the assessment referred to in paragraph 1 in time 
for the twenty-seventh meeting of the Open-ended Working Group for the 
consideration of the Nineteenth Meeting of the Parties. (MOP 18, 2006)
    The global warming potential (GWP) index is a means of quantifying 
the potential integrated climate forcing of various greenhouse gases 
relative to carbon dioxide. Earlier data found a direct 100-year 
integrated GWP (100yr GWP) for nPB of 0.31 (Atmospheric and 
Environmental Research, Inc., 1995). More recent analysis that 
considers both the direct and the indirect GWP of nPB found a 100-yr 
GWP of 1.57 (ICF, 2003a; ICF, 2006a). In either case, the GWP for nPB 
is comparable to or below that of previously approved substitutes in 
these end uses.
    Use of nPB may be controlled as a volatile organic compound (VOC) 
under state implementation plans (SIPs) developed to attain the 
National Ambient Air Quality Standards for ground-level ozone, which is 
a respiratory irritant. Users located in ozone nonattainment areas may 
need to consider using a substitute for cleaning that is not a VOC or 
if they choose to use a substitute that is a VOC, they may need to 
control emissions in accordance with the SIP. Companies have petitioned 
EPA, requesting that we exempt nPB from regulation as a VOC. However, 
unless and until EPA issues a final rulemaking exempting a compound 
from the definition of VOC and states change their SIPs to exclude such 
a compound from regulation, that compound is still regulated as a VOC. 
Other acceptable ODS-substitute solvents that are VOCs for state air 
quality planning purposes include most oxygenated solvents such as 
alcohols, ketones, esters, and ethers; hydrocarbons and terpenes; 
trichloroethylene; trans-1,2-dichloroethylene; monochlorotoluenes; and 
benzotrifluoride. Some VOC-exempt solvents that are acceptable ODS 
substitutes include HFC-245fa, HCFC-225ca/cb, HFC-365mfc and HFC-
4310mee for aerosol solvents, and methylene chloride, 
perchloroethylene, HFE-7100, HFE-7200, PCBTF, acetone, and methyl 
acetate for aerosol solvents, adhesives, and coatings.

C. Ecosystem and Other Environmental Impacts

    EPA considered the possible impacts of nPB if it were to pollute 
soil or water as a waste and compared these impacts to screening 
criteria developed by the Endocrine Disruptor Screening and Testing 
Advisory Committee (EDSTAC, 1998) (see Table 5). Available data on the 
organic carbon partition coefficient (Koc), the breakdown 
processes in water and hydrolysis half-life, and the volatilization 
half-life indicate that nPB is less persistent in the environment than 
many solvents and would be of low to moderate concern for movement in 
soil. Based on the LC50, the acute concentration at which 
50% of tested animals die, nPB's toxicity to aquatic life is moderate, 
being less than that for some acceptable cleaners (for example, 
trichloroethylene, hexane, d-limonene, and possibly some aqueous 
cleaners) and greater than that for some others (methylene chloride, 
acetone, isopropyl alcohol, and some other aqueous cleaners). The 
LC50 for nPB is 67 milligrams per liter (mg/l), which is 
greater and thus less toxic than an LC50 of 10 mg/l, one of 
EPA's criteria for listing under the Toxics Release Inventory (US EPA, 
1992; ICF, 2004a). Based on its relatively low bioconcentration factor 
and log Kow value (logarithm of the octanol-water partition 
coefficient), nPB is not prone to bioaccumulation. Table 5 summarizes 
information on environmental impacts of nPB; trans-1,2-
dichloroethylene, a commonly-used solvent in blends for aerosol 
solvents, precision cleaning, and electronics cleaning; acetone, a 
commonly-used carrier solvent in adhesives; trichloroethylene, a 
solvent used for metals, electronics, and precision cleaning that could 
potentially be used in aerosol or adhesive end-uses; and methyl 
chloroform, an ODS that nPB would replace.

[[Page 30175]]



                                    Table 5.--Ecosystem and Other Environmental Properties of nPB and Other Solvents
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                   Description of                         Value for trans-
            Property                environmental       Value for nPB       1,2-dichloro-     Value for acetone        Value for        Value for methyl
                                      property                                ethylene                             trichloroethylene       chloroform
--------------------------------------------------------------------------------------------------------------------------------------------------------
Koc, organic-carbon partition    Degree to which a   330 (Source: ICF,   32 to 49 (Source:   5.4 (Source:        106 to 460 (Source:   152 (Source: U.S.
 coefficient.                     substance tends     2004a).             ATSDR, 1996).       ATSDR, 1994).       ATSDR, 1997).         EPA, 1994a).
                                  to stick to soil
                                  or move in soil.
                                  Lower values (<
                                  300)\*\ indicate
                                  great soil
                                  mobility; values
                                  of 300 to 500
                                  indicate moderate
                                  mobility in soil.
Break down in water............  Mechanism and       Hydrolysis is       Photolytic          Biodegradation is   Volatilization and    Volatilization
                                  speed with which    significant.        decomposition,      most significant    biodegradation most   most
                                  a compound breaks   Hydrolysis half-    dechlorination      form of breakdown   significant, with     significant;
                                  down in the         life of 26 days     and                 (Source: ATSDR,     hydrolysis            biodegradation
                                  environment.        (Source: ICF,       biodegradation      1994).              relatively            and hydrolysis
                                  (Hydrolysis half-   2004a).             are significant;                        insignificant.        also occur
                                  life values > 25                        hydrolysis not                          Hydrolysis half-      (Source: ATSDR,
                                  weeks\*\ are of                         significant                             life of 10.7 to 30    2004).
                                  concern.).                              (Source: ATSDR,                         months (Source:
                                                                          1996).                                  ATSDR, 1997).
Volatilization half-life from    Tendency to         3.4 hours-4.4 days  3 to 6.2 hours      7.8 to 18 hours     3.4 hours to 18 days  Hours to weeks
 surface waters.                  volatilize and      (Source: ICF,       (Source: ATSDR,     (Source: ATSDR,     (Source: ATSDR,       (Source: U.S.
                                  pass from water     2004a).             1996).              1994).              1997).                EPA, 1994a).
                                  into the air.
LC50 (96 hours) for fathead      Concentration at    67 mg/L (Source:    108 mg/L (Source:   7280 to 8120 mg/L   40.7 to 66.8 mg/L     52.8 to 105 mg/L
 minnows.                         which 50% of        Geiger, 1988).      U.S. EPA, 1980).    (Source: Fisher     (Source: NPS, 1997).  (Source: U.S.
                                  animals die from                                            Scientific, 2001).                        EPA, 1994a).
                                  toxicity after
                                  exposure for 4
                                  days.
log Kow........................  Logarithm of the    2.10 (Source: ICF,  -0.48 (Source:      -0.24 (Source:      2.38 (Source:         2.50 (Source:
                                  octanol/water       2004a).             LaGrega et al.,     LaGrega et al.,     LaGrega et al.,       LaGrega et al.,
                                  partition                               2001, p. 1119).     2001, p. 1117).     2001, p. 1127).       2001, p. 1127).
                                  coefficient, a
                                  measure of
                                  tendency to
                                  accumulate in
                                  fat. Log Kow
                                  values >3 \;*\
                                  indicate high
                                  tendency to
                                  accumulate.
Bioconcentration factor........  High factors        23 (Source: HSDB,   5 to 23 (Source:    <1 (Source: ATSDR,  10 to 100 (Source:    <9 (Source: U.S.
                                  (>1000)\*\          2004).              ATSDR, 1996).       1994).              ATSDR, 1997).         EPA, 1994a).
                                  indicate strong
                                  tendency for fish
                                  to absorb the
                                  chemical from
                                  water into body
                                  tissues.
--------------------------------------------------------------------------------------------------------------------------------------------------------
\*\Criteria from EDSTAC, 1998.

    nPB is not currently regulated as a hazardous air pollutant and is 
not listed as a hazardous waste under the Resource Conservation and 
Recovery Act (RCRA). nPB is not required to be reported as part of the 
Toxic Release Inventory under Title III of the Superfund Amendments and 
Reauthorization Act. Despite this, large amounts of nPB might be 
harmful if disposed of in water. We recommend that users dispose of nPB 
as they would dispose of any spent halogenated solvent (F001 waste 
under RCRA). Users should not dump nPB into water, and should dispose 
of it by incineration. We conclude that nPB does not pose a 
significantly greater risk to the environment than other available 
alternatives, and that the use of nPB within the U.S. should not be 
prohibited under the SNAP program on the basis of its environmental 
impacts.

D. Flammability and Fire Safety

    A number of commenters on the June 2003 proposal provided 
additional information on the flammability of nPB using standard test 
methods for determining flash point, such as the American Society for 
Testing and Materials (ASTM) D 92 open cup, ASTM D56 Tag closed cup, 
and ASTM D93 Pensky-Martens closed cup methods (BSOC, 2000; Miller, 
2003; Morford, 2003a, 2003b, and 2003c;

[[Page 30176]]

Shubkin, 2003; Weiss Cohen, 2003). We agree with the commenters that by 
these standard test methods, nPB displayed no flash point. Thus under 
standard test conditions, nPB is not flammable, and it should not be 
flammable under normal use conditions. With its low potential for 
flammability, nPB is comparable to chlorinated solvents, HCFCs, HFEs, 
HFC-245fa, HFC-4310mee, and aqueous cleaners, and is less flammable 
than many acceptable substitutes, such as ketones, alcohols, terpenes, 
and hydrocarbons. nPB exhibits lower and upper flammability limits of 
approximately 3% to 8% (BSOC, 2000). A number of other solvents that 
are typically considered to be non-flammable also have flammability 
limits (for example, methylene chloride, HCFC-141b, and methyl 
chloroform). If the concentration of vapor of such a solvent falls 
between the upper and lower flammability limits, it could catch fire in 
presence of a flame. Such a situation is unusual, but users should take 
appropriate precautions in cases where the concentration of vapor could 
fall between the flammability limits.

E. Health Impacts and Exposure

    In evaluating potential human health impacts of nPB used as a 
substitute for ozone-depleting substances, EPA considered impacts on 
both exposed workers and on the general population. Using the same 
approach finalized in the original SNAP rulemaking, EPA evaluated the 
available toxicity data using EPA guidelines to develop health-based 
criteria to characterize human health risks (US EPA, 1994b. Inhalation 
Reference Concentration Guidelines; U.S. EPA, 1991. Guidelines for 
Developmental Toxicity Risk Assessment; U.S. EPA, 1995a. Benchmark Dose 
guidelines; U.S. EPA, 1996. Guidelines for Reproductive Toxicity Risk 
Assessment).
    To assess human health risks, EPA followed the four basic steps of 
risk assessment outlined by the National Academy of Sciences: hazard 
identification, dose-response relationship, exposure assessment, and 
risk characterization (NAS, 1983). First, EPA examined available 
studies on nPB's effects. Second, EPA considered the acceptable 
exposure levels for evaluating worker exposure and a community exposure 
guideline (CEG) for evaluating exposure to the general population based 
upon inhalation exposure. Third, EPA compared the acceptable exposure 
levels and CEG to available exposure data and projections of exposure 
levels to assess exposure, including new exposure data available since 
publication of the June 2003 NPRM. Finally, EPA decided whether there 
was sufficient evidence indicating that nPB could be used as safely as 
other alternatives available in a particular end use.
Authority To Set an Acceptable Exposure Limit
    Two commenters on the June 2003 NPRM said that EPA has no 
jurisdiction to develop any acceptable exposure limit (AEL) designed to 
be applicable to a workplace environment and that only the Occupational 
Safety and Health Administration (OSHA) has that authority (Stelljes, 
2003; Morford, 2003d). In contrast, another commenter said that EPA has 
the authority to set an AEL for nPB under section 612 of the Clean Air 
Act, has done so in the past for other chemicals (e.g., HFC-4310mee, 
HCFC-225ca/cb), and should require the AEL as a use condition (Risotto, 
2003).
    EPA believes it has the authority to calculate exposure limits for 
the workplace under section 612. Section 612(c) specifically states 
that

The Administrator shall issue regulations: providing that it shall 
be unlawful to replace any class I or class II substance with any 
substitute substance which the Administrator determines may present 
adverse effects to human health or the environment, where the 
Administrator has identified an alternative to such replacement 
that--
    (1) reduces the overall risk to human health and the 
environment; and
    (2) is currently or potentially available.

Thus, we must compare the risks to human health and the environment of 
a substitute to the risks associated with other substitutes that are 
currently or potentially available, as required by the Clean Air Act. 
In order to compare risks to human health, EPA performs quantitative 
risk assessments on different chemicals comparing exposure data and 
exposure limits, following the process described above by the National 
Academies of Science (NAS, 1983) and as described in the preamble to 
the original final SNAP rule (March 18, 1994; 59 FR 13066). Because 
most humans who are exposed to nPB are exposed in the workplace, the 
appropriate exposure data and exposure limits to protect human health 
must include workplace exposure data and acceptable exposure limits for 
the workplace. Because there is wide disparity in acceptable exposure 
limits for nPB developed by industry, ranging from 5 ppm to 100 ppm 
(Albemarle, 2003; Chemtura, 2006; Docket A-2001-07, item II-D-19; 
Enviro Tech International, 2006; Farr, 2003; Great Lakes Chemical 
Company, 2001), and because there is not a Permissible Exposure Limit 
for nPB set by the Occupational Safety and Health Administration, EPA 
believes it is appropriate to independently evaluate the human health 
risks associated with use of nPB in the workplace. Similarly, EPA has 
developed a community exposure guideline to assess the human health 
effects of nPB exposure to the general public.
Skin Notation
    Several commenters on the June 2003 proposal stated that a skin 
notation for nPB is appropriate, while another commenter agreed with 
EPA's proposal that no skin notation was necessary (Smith, 2003; HESIS, 
2003; Werner, 2003, Weiss Cohen, 2003). Rat studies indicate that 
dermal exposure to nPB results in neither appreciable absorption 
through the skin (RTI, 2005) nor systemic toxicity (Elf Atochem, 1995). 
Unlike methyl chloride and dichlorvos, which are absorbed through the 
skin and could contribute to systemic toxicity (ACGIH, 1991), EPA is 
not proposing to include a skin notation for nPB in the information 
provided to users associated with this rulemaking because of the 
relatively low level of absorption. The American Conference of 
Governmental Industrial Hygienists (ACGIH) provides no skin notation in 
its documentation for threshold limit values (TLVs) for several 
solvents, including nPB (ACGIH, 2005), methylene chloride, and 
perchloroethylene, and there is no evidence that absorption through the 
skin is greater for nPB than for the other halogenated compounds. 
Further, including a statement giving advice about how to reduce skin 
exposure in the ``Further Information'' column of listings is likely to 
be more informative to workers than a skin notation.
    Given the possibility that some nPB can be absorbed through the 
skin in humans, and that the solvent can irritate the skin, EPA 
encourages users to wear protective clothing and flexible laminate 
gloves when using nPB and encourages vendors to include such 
precautions in their Material Safety Data Sheets (MSDSs). EPA requests 
comment on whether it would be useful, in lieu of a skin notation to 
add the following statement in the ``further information'' column of 
each end use where we find nPB acceptable with restrictions: ``EPA 
recommends the use of personal protective equipment, including chemical 
goggles, flexible laminate protective gloves and chemical-resistant 
clothing, when using nPB.''
    EPA also considered the potential health effects of contamination 
of nPB formulations with isopropyl bromide

[[Page 30177]]

(iPB).\7\ In the June 2003 proposed rule, we proposed as a use 
condition that nPB formulations contain no more than 0.05% iPB by 
weight. One commenter opposed the proposed use condition, stating that 
it places an undue legal burden on end users, rather than the 
manufacturers of raw materials, that it would not benefit worker 
safety, and that the nPB industry has worked to reduce iPB content 
below 0.05% (Morford, 2003e). We agree that industry has met this 
contamination limit for several years without regulation. Furthermore, 
EPA agrees that if users are exposed to nPB concentrations no higher 
than the highest potentially acceptable concentration (30 ppm), a 
worker's exposure to iPB will be sufficiently low to avoid adverse 
effects. Therefore, this proposed rule does not include a use condition 
limiting iPB content in nPB formulations.
---------------------------------------------------------------------------

    \7\ iPB is also referred to as 2-bromopropane, 2-propyl bromide, 
or 2-BP. Its CAS registry number is 75-26-3.
---------------------------------------------------------------------------

1. Workplace Risks
    In the June 2003 NPRM, EPA proposed that an exposure limit of 25 
ppm would be protective of a range of effects observed in animal and 
human studies, including reproductive and developmental toxicity, 
neurotoxicity, and hepatotoxicity. Reduction of sperm motility in rats, 
noted across multiple studies at relatively low exposures, was 
determined to be the most sensitive effect. The Agency derived an 
exposure limit of 18 ppm from a dose response relationship in male rat 
offspring (``F1 generation'') whose parents were exposed to nPB from 
prior to mating through birth and weaning of the litters (WIL, 2001). 
We then proposed to adjust this value upwards to 25 ppm based on 
principles of risk management, consistent with one of the original 
``Guiding Principles'' of the SNAP program (59 FR 13046, March 18, 
1994). As we discussed in the June 2003 NPRM, EPA noted that adhesives 
users should be able to achieve an AEL of 25 ppm and that 25 ppm was 
between the level based on the most sensitive endpoint (sperm motility 
in the F1 offspring generation at 18 ppm) and the second most sensitive 
endpoint (sperm motility in the F0 parental generation at 30 ppm). 
Following SNAP program principles, we noted that ``a slight adjustment 
of the AEL may be warranted after applying judgment based on the 
available data and after considering alternative derivations'' (69 FR 
33295). Because the animals were exposed to nPB for some time periods 
that would not occur during actual occupational exposure, we stated 
further that ``18 ppm is a reasonable but possibly conservative 
starting point, and that exposure to 25 ppm would not pose 
substantially greater risks, while still falling below an upper bound 
on the occupation[al] exposure limit.''
    Since the 2003 proposal, the Agency has reviewed both information 
available at the time of the 2003 NPRM related to the health risks 
associated with nPB use, as well as more recent case studies of nPB 
exposures and effects in the workplace, newly published toxicological 
studies, comments to the June 2003 NPRM, including new risk assessments 
on nPB, and a new threshold limit value (TLV) issued by ACGIH.
    OSHA has not developed a permissible exposure limit (PEL) for nPB 
that EPA could use to evaluate toxicity risks from workplace exposure. 
The ACGIH, an independent organization with expertise in industrial 
hygiene and toxicology, has developed a final workplace exposure limit 
of 10 ppm (ACGIH, 2005); however, as discussed below, EPA has concerns 
about the documentation and basis of ACGIH's derivation.
    The Agency reconsidered which exposure levels are likely to protect 
against various health effects, based on review of all available 
information. We summarize benchmark dose data for a number of endpoints 
found in these analyses in Table 6 below. We examined these data to 
assess the acceptability of nPB use in the aerosol solvent, adhesive 
and coatings end uses reviewed in this proposed rule. These data 
indicate that, once uncertainty factors are applied consistent with EPA 
guidelines, the lowest levels for acceptable exposures would be derived 
for reproductive effects.\8\ The data indicate that levels sufficient 
to protect against male reproductive effects (e.g., reduced sperm 
motility) would be in a range from 18 to 30 ppm,\9\ in the range of 17 
to 22 ppm to protect against female reproductive effects (e.g., number 
and length of estrous cycles), and at approximately 20 ppm for effects 
related to reproductive success (live litter size).
---------------------------------------------------------------------------

    \8\ By EPA guidelines, we would apply an uncertainty factor of -
10, or approximately 3, for differences between species for all 
health effects. We would also apply an uncertainty factor of 
[radic]10 (3) for variability within the working population for 
reproductive and developmental effects, because, among other 
reasons, these conditions would not necessarily screen out an 
individual from being able to work, unlike for liver or nervous 
system effects. Therefore, for reproductive and developmental 
effects, we use a composite uncertainty factor of 10. See further 
discussion of uncertainty factors in section V.C. below.
    \9\ Based on WIL, 2001, as analyzed in ICF, 2002. The equivalent 
values based upon Stelljes and Wood's (2004) analysis of WIL, 2001 
would be slightly lower, from 16 to 28 ppm.

                        Table 6.--Summary of Endpoints Using Benchmark Response Modeling
----------------------------------------------------------------------------------------------------------------
                                                                                                      Human
                                                                                Benchmark  dose     equivalent
                Endpoint a                                 Study                   lowerbound     concentration
                                                                                (BMDL) b  (ppm)   (HEC) c  (ppm)
----------------------------------------------------------------------------------------------------------------
                                                 Liver Effects d
----------------------------------------------------------------------------------------------------------------
Liver vacuolation in males (F1 offspring    WIL, 2001 as analyzed in ICF, 2002              110              116
 generation).
Liver vacuolation in males (F0 parent       WIL, 2001 as analyzed in ICF, 2002              143              150
 generation).
Liver vacuolation.........................  ClinTrials, 1997b as analyzed in                226              170
                                             ICF, 2002 and Stelljes & Wood,
                                             2004.
----------------------------------------------------------------------------------------------------------------
                                           Reproductive Effects--Male
----------------------------------------------------------------------------------------------------------------
Sperm motility (F1 offspring generation)..  WIL, 2001 as analyzed in ICF, 2002              169              177
                                            WIL, 2001 as analyzed in Stelljes               156              164
                                             & Wood, 2004.
Sperm motility (F0 parent generation).....  WIL, 2001 as analyzed in ICF, 2002              282              296
                                            WIL, 2001 as analyzed in Stelljes               263              276
                                             & Wood, 2004.
Prostate weight (F0 parent generation)....  WIL, 2001 as analyzed in TERA,                  190              200
                                             2004.

[[Page 30178]]

 
Sperm count...............................  Ichihara et al., 2000b as analyzed              232              325
                                             in Stelljes & Wood, 2004.
Sperm deformities (F0 parent generation)..  WIL, 2001 as analyzed in Stelljes               296              311
                                             & Wood, 2004.
----------------------------------------------------------------------------------------------------------------
                                          Reproductive Effects--Female
----------------------------------------------------------------------------------------------------------------
Number of estrus cycles during a 3 week     WIL, 2001 as analyzed in ICF, 2006              162              170
 period (F0 parent generation).             WIL, 2001 as analyzed in ICF, 2006              208              218
Estrous cycle length (F1 offspring          WIL, 2001 as analyzed in TERA,                  400              420
 generation) d.                              2004.
Estrous cycle length (F0 parent             WIL, 2001 as analyzed in TERA,                  210              220
 generation) e.                              2004.
No estrous cycle incidence (F1 offspring    WIL, 2001 as analyzed in TERA,                  180              189
 generation).                                2004.
No estrous cycle incidence (F0 parent       WIL, 2001 as analyzed in TERA,                  480              504
 generation).                                2004.
----------------------------------------------------------------------------------------------------------------
                                   Reproductive Effects--Reproductive Success
----------------------------------------------------------------------------------------------------------------
Decreased live litter size (F1 offspring    WIL, 2001 as analyzed in TERA,                  190              200
 generation).                                2004.
Decreased live litter size (F2 offspring    WIL, 2001 as analyzed in TERA,                  170              179
 generation).                                2004.
Pup weight gain, post-natal days 21 to 28   WIL, 2001 as analyzed in TERA,                  180              189
 (F1 offspring generation).                  2004.
----------------------------------------------------------------------------------------------------------------
                                              Developmental Effects
----------------------------------------------------------------------------------------------------------------
Fetal body weight.........................  WIL, 2001 as analyzed in TERA,                  310              326
                                             2004.
Fetal body weight.........................  WIL, 2001 as analyzed in CERHR,                 305              320
                                             2002a.
----------------------------------------------------------------------------------------------------------------
                                             Nervous System Effects
----------------------------------------------------------------------------------------------------------------
Hindlimb strength.........................  Ichihara et al, 2000a as analyzed               214             300
                                             in Stelljes and Wood, 2004.
----------------------------------------------------------------------------------------------------------------
 a Unless explicitly stated, data are from a parental generation. Of the studies analyzed, only the WIL, 2001
  study has multiple generations to be analyzed.
 b The benchmark response value represents a specified level of excess risk above a control response.
 c When considering workplace exposures, the human equivalent concentration is the BMDL, adjusted to apply to a
  40-hour work week in which workers are exposed for 8 hours a day for five days per week. Animals in the WIL,
  2001 study were exposed for 6 hours a day, 7 days a week. Animals in the Ichihara, 2000a and 2000b studies
  were exposed for 8 hours a day, 7 days a week. Animals in the ClinTrials, 1997b study were exposed for 6 hours
  a day, 5 days a week.
 d After applying an uncertainty factor of 3 for animal to human extrapolation, acceptable levels of exposure to
  protect against liver effects would be in the range of 39 to 57 ppm.
 e Omits data from those animals that have stopped estrous cycling altogether (TERA, 2004).

2. General Population Risks
    EPA used a community exposure guideline of 1 ppm to assess 
potential risks to the general population living near a facility using 
nPB (see section V.E below). Of the end uses covered in this rule, use 
of nPB-based adhesives would result in the highest exposure levels, and 
so, we first examined general population exposure from adhesives. ICF 
Consulting modeled inhalation exposure to nPB to people living near a 
plant using nPB-based adhesives in several scenarios using the Agency's 
SCREEN3 model (US EPA, 1995b). Based on this modeling, EPA found that 
the exposure to individuals in the general population was below the 
community exposure guideline. The analysis indicates that nPB is no 
greater a hazard to the general population than other acceptable 
solvents under the SNAP program. For further discussion, see the risk 
screen for nPB (ICF, 2006a).
    Representatives from a state environmental agency and from a 
potential user of nPB have asked EPA whether we had developed a 
reference concentration (RfC). We clarify that the community exposure 
guideline is a value developed by the SNAP program for our risk 
assessment of nPB following EPA's RfC Guidelines. However, it is not a 
formal RfC developed by EPA's National Center for Environmental 
Assessment and is not in IRIS. At this time, EPA does not have plans to 
issue an official RfC for nPB.

V. How did EPA assess impacts on human health?

A. Newly Available Exposure Data

    Since publication of the June 2003 NPRM, EPA has received 
additional information on exposure levels in each end use discussed in 
this proposal.
    In the adhesives end use, we considered new exposure modeling based 
on information from site visits to facilities using spray adhesives 
(ICF, 2006a). These data predicted that:
     At average rates of ventilation and adhesive application, 
average workplace exposures would be approximately 60 ppm.
     Average adhesive application rates and poor ventilation 
rates resulted in average exposures of approximately 250 ppm.
     High (90th percentile) adhesive application rates and 
average ventilation rates resulted in average exposures of 
approximately 600 ppm.
     In the worst case scenario with high adhesive application 
rates and poor ventilation, average workplace exposures would be as 
high as 2530 ppm.
    We compared the modeled data in the four exposure scenarios to 
measured exposure data in three health hazard evaluations by the 
National Institute for Occupational Safety and Health (NIOSH) (NIOSH 
2002a, 2002b, 2003a).

[[Page 30179]]

Our understanding is that North Carolina OSHA received complaints from 
workers and requested that NIOSH evaluate health hazards at these three 
facilities. NIOSH found average exposure levels of 68 ppm, 116 ppm, 127 
ppm, and 195 ppm for sprayers actively using the adhesive prior to 
installation of state-of-the-art ventilation systems (NIOSH 2002a, 
2002b, 2003a). The plant with an average exposure level of 68 ppm for 
sprayers (9 samples) had an average exposure level comparable to the 
average concentration of 60 ppm in the modeling scenario with average 
adhesive rates and average ventilation levels. The other plants with 
average exposure levels of 116 to 127 ppm (20 samples), and of 195 ppm 
(36 samples) for sprayers had exposure levels between the average 
modeled exposure for a facility with average adhesive application rates 
and average ventilation (60 ppm) and the average modeled exposure for a 
facility with average adhesive application rates and poor ventilation 
(250 ppm). Based on this comparison, EPA believes the modeled exposure 
levels are a reasonable predictor of actual exposure based on current 
industry practice in the adhesive end use.
    In the aerosol solvent end use, we received a study on workplace 
exposure levels of nPB-based aerosols from a commenter (Linnell, 2003). 
This study was performed to simulate typical exposure levels in a 
number of situations where nPB might be used in the workplace while 
using different types of ventilation equipment, rather than using data 
from current industry users of nPB-based aerosols in their actual 
manufacturing or maintenance processes. As discussed below in section 
VI.A., we are concerned that the exposure data and ventilation levels 
in this study may not be representative of use of nPB-based aerosols in 
industry. Personal breathing zone samples taken from the collars of 
workers showed 8-hour time-weighted average (TWA) exposures of 5.5, 13, 
and 32 ppm for workers using 310 g of nPB from a spray can \10\ 
(Linnell, 2003). The two higher exposure levels occurred in the absence 
of any local or regional ventilation; the use of both local and 
regional ventilation equipment with ventilation levels around 1900 
ft3/min was associated with the lowest exposure level. 
Short-term exposures of 370, 1,100 and 2,100 ppm taken from a room with 
regional ventilation at 640 cubic feet per minute (cfm), when averaged 
over an 8-hour period, resulted in exposures of 12, 34, and 66 ppm 
(Linnell, 2003). EPA considers the highest of these 8-hour values, 66 
ppm, not to be representative of worker exposure from inhalation 
because the measurement was taken from the worker's wrist, rather than 
from his breathing zone. Another short-term exposure value of 190 ppm, 
taken from a vented booth with local ventilation at 472 cfm, in 
addition to the regional ventilation of 640 cfm, resulted in an 8-hour 
exposure of 6 ppm. Similar measurements were made in another study we 
considered in developing the June 2003 NPRM: Eight hour (8-hr) TWA 
exposures of 11.3, 15.1, 17.0, and 30.2 ppm with regional ventilation 
of 300 cubic feet per minute from a fan for the entire room 
(Confidential submission, 1998).
---------------------------------------------------------------------------

    \10\ Unlike samples measured directly in the breathing zone, 
area samples measured in the study are not considered representative 
of actual exposure and are not discussed here. Short-term 
measurements taken over 15 minutes from personal samplers, although 
in some cases extremely high, are not discussed in detail here 
because available toxicity information does not indicate need for a 
short-term exposure limit for nPB in addition to the 8-hr TWA limit 
(ACGIH, 2005; ERG, 2004). Additional information on these other 
samples is in the occupational exposure assessment for aerosols in 
the risk screen for nPB (ICF, 2006a).
---------------------------------------------------------------------------

    Another commenter submitted information on aerosol exposures for a 
number of other available alternative aerosols (Werner, 2003). While 
these data do not include nPB, based on the properties of aerosol 
solvents, we believe it is reasonable to compare concentrations of 
these different chemicals to potential nPB exposures. The study 
compared concentrations of eight different chemicals that are 
acceptable under the SNAP program in aerosol formulations: HFE-7100, 
HFE-7200, trans-1,2-dichloroethylene, HCFC-225ca and -225cb, acetone, 
pentane, and HFC-134a. In this study, with ventilation of only 48 cfm, 
8-hr TWA exposure from the different chemicals varied from 35.5 ppm to 
194.0 ppm,\11\ below the recommended exposure levels for these 
particular chemicals (ICF, 2006a) but above the range of exposure 
levels that EPA would consider acceptable for nPB.
---------------------------------------------------------------------------

    \11\ These measurements can be converted to estimates of nPB 
exposure by multiplying the measured concentration of the alternate 
chemical by the molecular weight of the same alternate chemical and 
dividing this by the molecular weight of nPB, 123. After performing 
this calculation, the equivalent exposure levels for nPB vary from 
29.5 ppm to 394.4 ppm.
---------------------------------------------------------------------------

    In addition, we considered new information from modeling of nPB 
exposures (ICF, 2006a). The modeling examined exposure levels that 
would be expected at ventilation levels of 450 cfm, 625 cfm, and 1350 
ppm, considering the molecular weight of the compound and the 
composition of different aerosol blends. EPA's SNAP program has 
previously used these same levels to calculate potential aerosol 
exposures, based upon exposure levels expected during benchtop 
cleaning. In a space with an air exchange rate of 450 ft3/
minute or less,\12\ EPA's modeling predicts 8-hour average exposure of 
approximately 16 to 17 ppm if a user sprays 450 g of nPB (approximately 
1 lb),\13\ and corresponding higher exposure values at higher spray 
rates (e.g., 33 ppm if the amount of nPB sprayed is 900 g) (ICF, 
2006a). Exposure values were predicted to be lower at higher 
ventilation rates.
---------------------------------------------------------------------------

    \12\ This corresponds roughly to a regional or room fan at low 
levels or natural air currents in an open area. Confined areas would 
have even lower air exchange rates with higher exposure levels.
    \13\ We consider use of 1000 g/day to be the high end of typical 
use, based on the setup of one of the exposure studies (Confidential 
Submission, 1998). The typical aerosol solvent user in the 
electronics industry uses a can per day (Williams, 2005). This is 
comparable to or slightly less than the spray rate assumed in the 
modeling.
---------------------------------------------------------------------------

    Since the June 2003 NPRM, EPA received a new submission for nPB in 
coatings (Lake City Army Ammunition Plant, 2003). The Lake City Army 
Ammunition Plant provided data on workplace exposure to nPB (Lake City 
Army Ammunition Plant, 2004). The mean exposure at this facility was 
3.7 ppm. Out of 31 samples taken, 25 (approximately 80%) were below 5 
ppm. Only one of 31 samples had an exposure level above 10 ppm, and 
that exposure value was approximately 21 ppm.

B. Newly Available Data on Health Effects

    Since publication of the June 2003 NPRM, EPA has examined 
additional occupational (Table 7) and animal (Table 8) studies that 
have become available:

[[Page 30180]]



                              Table 7.--Recent Studies on nPB Occupational Exposure
----------------------------------------------------------------------------------------------------------------
                                  Sample size/
          Case Study               population       Exposure data        Observations             Remarks
----------------------------------------------------------------------------------------------------------------
Beck and Caravati, 2003.......  6 foam cushion    Exposure during   Lower leg weakness     Small sample size
                                 factory workers   30-40 hr/wk for   accompanied by pain    studied. Possible
                                 (gluers).         a 3-month         and difficulty with    interference or
                                                   period.           standing and           synergistic effects
                                                   Exposure          walking, numbness of   from other adhesive
                                                   measured in one   legs and feet,         ingredients (1,2-
                                                   day was a mean    hyperreflexia and      epoxybutane and
                                                   of 130 ppm        hypertonicity of       styrene-butadiene).
                                                   (range, 91-176    lower extremities,
                                                   ppm).             dizziness and
                                                                     shortness of breath,
                                                                     and peripheral
                                                                     neurotoxicity.
                                                                     Measured serum
                                                                     bromide levels were
                                                                     elevated, range 44-
                                                                     170 mg/dL.
Majersik et al., 2004;          6 foam cushion    5-8 hr/day for    Subacute onset of      Follow-up to Beck and
 Majersik et al., 2005 *.        factory workers   at least 2        lower extremity        Caravati (2003).
                                 (gluers).         years with mean   pain, difficulty       Chronic nPB exposure
                                                   air               walking, and high      associated with
                                                   concentration     serum bromide levels   incapacitating
                                                   of 130 ppm on     in blood. Neurotoxic   neurotoxic syndrome.
                                                   last day of       symptoms persisted     Initial report from
                                                   study.            for at least 2 years   Utah OSHA indicated
                                                   Measurements      after exposure ended.  erroneously that
                                                   taken over 9                             workers were not
                                                   hours                                    spraying while
                                                   (equivalent to                           measurements were
                                                   92-127 ppm with                          taken. In fact,
                                                   mean of 108 ppm                          adhesives were being
                                                   for an 8-hour                            sprayed and fans
                                                   TWA).                                    were being used only
                                                                                            for portions of the
                                                                                            day that
                                                                                            measurements were
                                                                                            taken, making
                                                                                            measurements likely
                                                                                            to be representative
                                                                                            of conditions during
                                                                                            the past several
                                                                                            months at the plant.
Ichihara et al., 2004a........  37 chemical       12 hour shifts    Mucosal irritation     Inadequate exposure
                                 plant workers     over 2-day        (nose, throat),        characterization and
                                 (24 males and     period, mean      headache, dizziness,   exposure to other
                                 13 females).      concentration     constipation,          potential toxicants,
                                                   of 82 ppm         intoxication, and      small sample size,
                                                   (range, 0-170     feeling light-headed   and no appropriate
                                                   ppm).             or heavy-headed.       control group.
                                                                     Four female workers    Healthy worker
                                                                     complained of          effect possible,
                                                                     disruption or          where more sensitive
                                                                     cessation of           workers left the
                                                                     menstruation. No       factory between 1996
                                                                     severe chronic         and 1999.
                                                                     symptoms of
                                                                     neurological damage
                                                                     at less than 170
                                                                     ppm. Several workers
                                                                     had hemoglobin and
                                                                     hematocrit values
                                                                     outside of the
                                                                     normal range and
                                                                     were diagnosed with
                                                                     mild anemia; most of
                                                                     these cases also
                                                                     showed signs of iron
                                                                     deficiency.
Ichihara et al., 2004b........  27 female         1-day exposure    Responses indicated    No long-term exposure
                                 chemical plant    period, range     anxiety, fatigue,      measurements, small
                                 workers (23 age   of exposure,      confusion, tension,    sample size; lack of
                                 matched with 23   0.34-49 ppm.      and depression.        controls for age,
                                 females from a                      Changes in menstrual   height, and body-
                                 beer factory                        status but not         weight. Low B
                                 control group).                     statistically          vitamin levels in
                                                                     significant. Effects   normal range in some
                                                                     on peripheral and      workers but
                                                                     central nervous        researchers
                                                                     system--diminished     concluded this did
                                                                     vibration sensation    not cause observed
                                                                     of the foot;           neurological
                                                                     significantly longer   effects.
                                                                     distal latency in      Additionally, the
                                                                     the tibial nerve;      study did not
                                                                     decreased values in    indicate any
                                                                     sensory nerve          significant
                                                                     conduction velocity    differences in the
                                                                     in the sural nerve;    prevalence of
                                                                     and lower scores on    menstrual cycle
                                                                     memory and             abnormalities.
                                                                     perceptual tests. No
                                                                     comparable effects
                                                                     seen in control
                                                                     group.
Nemhauser, 2005 *.............  Foam cushion      In 1999 study,    Higher exposure to     Small sample sizes
                                 factory workers   16 workers        nPB and dose-          studied with
                                 (gluers) in       exposed to mean   dependent              moderate worker
                                 North Carolina.   air               relationship among     participation.
                                                   concentration     those who reported     Healthy worker
                                                   of 116 ppm, and   anxiety, headache,     effect likely
                                                   12 sprayers       and ataxia. No         occurred: Those that
                                                   exposed to mean   reproductive           had most significant
                                                   concentration     abnormalities          health effects had
                                                   of 108 ppm with   reported in medical    already removed
                                                   range of 58 to    survey for men or      themselves from
                                                   254 ppm. In       women. Semen           workplace by the
                                                   2001 study, 13    analysis found no      time of the study.
                                                   workers exposed   differences between    No arsenic found at
                                                   to nPB mean air   exposed and            the plant.
                                                   concentration     unexposed workers.     Neurotoxic effects
                                                   of 46 ppm and                            caused by nPB. See
                                                   12 sprayers                              related Health
                                                   were exposed to                          Hazard Evaluation
                                                   mean                                     (HHE): NIOSH, 2003a.
                                                   concentration
                                                   of 101 ppm,
                                                   with range of
                                                   38 to 281 ppm.
NIOSH, 2003a..................  16 workers in     1999 Initial      Most workers exposed   Arsenic was not
                                 1999              Site Visit:       to nPB levels > 25     attributed to
                                 evaluation; 13    Geometric mean    ppm. Exposure          occupational
                                 workers in 2001   nPB               concentrations lower   exposure. The
                                 follow-up         concentration     in 2001 than 1999,     National Institute
                                 evaluation.       (from personal    but difference not     for Occupational
                                                   samples), 81.2    statistically          Safety and Health
                                                   (range, 18-254    significant.           (NIOSH) stated that
                                                   ppm); 2001        Headache, anxiety,     neurological
                                                   follow-up:        feeling drunk          symptoms may have
                                                   Geometric mean,   associated with nPB    been related to
                                                   81.2 ppm          exposure.              excess exposure to
                                                   (range, 7-281     Hematological          nPB, but that no
                                                   ppm).             endpoints unaffected   other effects could
                                                                     in exposed group. No   conclusively be
                                                                     correlation of nPB     related to nPB
                                                                     exposure with sperm    exposure.
                                                                     or semen indices or
                                                                     with neurological
                                                                     abnormalities.

[[Page 30181]]

 
Raymond and Ford, 2005 *......  4 foam cushion    Exposure study    Dizziness, numbness,   Small sample size,
                                 factory workers   conducted 9       ocular symptoms,       possible confounding
                                 (gluers) in       months after      lower extremity        effect from arsenic.
                                 North Carolina.   index patient     weakness and
                                                   became ill        unsteady gait,
                                                   indicated         weakness,
                                                   workers exposed   hypesthesia, and
                                                   to mean nPB air   ataxic gait in all
                                                   concentration     four workers.
                                                   of 116 ppm. 4     Symptoms decreased
                                                   workers exposed   over time but after
                                                   for 2-3 weeks     six years, at least
                                                   before initial    one worker re-
                                                   symptoms          exposed twice at
                                                   detected.         other furniture
                                                                     plants; one or more
                                                                     still suffer from
                                                                     ataxia.
Toraason et al., 2006.........  41 and 22 foam    1-3 days up to 8  No statistically       Authors find limited
                                 cushion factory   hrs per day,      significant            evidence that nPB
                                 workers           with              differences in DNA     poses a ``small
                                 (gluers) at 2     concentrations    damage with worker's   risk'' for DNA
                                 facilities.       of 0.2-271 ppm    nPB exposure. In       damage.
                                                   at facility A,    vitro results showed
                                                   4-27 ppm at       nPB increased DNA
                                                   facility B.       damage.
----------------------------------------------------------------------------------------------------------------
* Presentation at North American Congress of Clinical Toxicology on September 14, 2005.


                                                     Table 8.--Recent Animal Studies of nPB Effects
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                      Population/sample
             Citation                       size                Exposure                    Observations                           Comments
--------------------------------------------------------------------------------------------------------------------------------------------------------
Fueta et al., 2002................  24 male Wistar rats   6 hr/day, 5 day/wk    No apparent morphological defects    Only one exposure concentration was
                                     (12 control, 12       for 8 weeks at 700    in the brain.                        used (which is higher than the
                                     exposed).             ppm.                                                       level already associated with
                                                                                                                      other toxic effects in rodents
                                                                                                                      [400 ppm]) and a shorter exposure
                                                                                                                      duration (8 weeks) was used than
                                                                                                                      the other subchronic studies that
                                                                                                                      have shown effects (13 weeks).
Fueta et al., 2004................  58 male Wistar rats   6 hr/day, 5 day/wk    No apparent morphological defects    Unclear how nPB and/or its
                                     (29 experimental      for 4 to 8 weeks,     in the brain. Chronic inhalation     metabolites directly act on
                                     and 29 in control     700 ppm.              changes brain enzyme levels and      receptors or channels in the
                                     group).                                     electrical activity that is          brain.
                                                                                 reversible after exposure.
Furuhashi et al., 2006............  80 Wistar rats (pups  (1) 8 hr/day (4 hr,   (1) At 800 ppm: most rat offspring   Authors concluded that exposure to
                                     and their dams).      followed by 2.5-hr    died within 2 days of birth or in    nPB during pregnancy and lactation
                                                           rest period,          utero;. body weights of dams         adversely affects growth and
                                                           followed by 4 hr      significantly lower, organ weights   survival of offspring. Low numbers
                                                           exposure), 7 day/wk   of offspring significantly lower     of offspring in 400- and 800-ppm
                                                           during gestation      after weaning at 800 ppm in males,   exposure groups prevent
                                                           and nursing at 0,     and 800 and 400 ppm in females.      statistical testing
                                                           100, 400, 800 ppm     Most sperm and estrous indicators   EPA comments: Study design
                                                           in first experiment.  did not differ among the groups,     inconsistent with guidelines for
                                                          (2) Dams exposed       although the rate of sperm arrival   developmental studies, so
                                                           (800 ppm) during      to the cauda epididymis was          comparisons to previous studies
                                                           gestation (Group      significantly lower in the 400 ppm   are difficult. The mechanism for
                                                           A), offspring not     group. Inconsistent or no changes    the adverse effects observed is
                                                           exposed during        in biochemical indicators.           not known (e.g., indirect exposure
                                                           nursing. Offspring   (2) Second experiment No difference   through milk, changes in nursing
                                                           of Group (B) of       in body weights and pregnancy        behavior, changes in milk
                                                           unexposed dams were   endpoints between exposed (800       production, exposure in utero,
                                                           nursed by exposed     ppm) and unexposed dams. Live        changes in the intrauterine
                                                           dams. Offspring in    offspring at birth, survival         environment)
                                                           control groups C      rates, body weights, significantly
                                                           and D not exposed.    decreased, number of dead
                                                                                 offspring, significantly increased
                                                                                 in 800-ppm groups.
Honma et al., 2003................  Fisher 344 male rats  8 hr/day, 7day/wk     3 week exposure to greater than 50   Neurological effects shown to be
                                                           for three weeks       ppm temporarily increased            transient and reversible at >= 200
                                                           exposed to 0, 10,     locomotor activity and ambulatory    ppm (Ichihara et al., 2000) or
                                                           50, 200 or 1000 ppm   and rearing behaviors in male rats.  absent after 28 days of exposure
                                                           (5 rats/dosage and                                         at concentrations >= 400 ppm
                                                           5 different tests).                                        (ClinTrials, 1997a) or after 90
                                                                                                                      days of exposure at concentrations
                                                                                                                      up to 600 ppm (ClinTrials, 1997b)
                                                                                                                      in other studies. Human studies
                                                                                                                      are limited by co-exposures and
                                                                                                                      poor estimates of exposure
                                                                                                                      concentrations. Thus, EPA is not
                                                                                                                      using this endpoint as the basis
                                                                                                                      of an AEL.

[[Page 30182]]

 
Ishidao et al., 2002..............  30 male Wistar rats.  6 hr/day, 5 day/wk    nPB is metabolized rapidly in the    Exposure levels are higher than in
                                                           with test groups      rat following exposures to nPB at    some other studies and are much
                                                           (10/dose) exposed     concentrations >= 700 ppm for at     higher than concentrations seen in
                                                           to 700 ppm for 4      least 3 weeks.                       the workplace. nPB metabolism
                                                           and 12 weeks and                                           appears to be different following
                                                           1500 ppm for 3 and                                         multiple exposures as compared to
                                                           4 weeks.                                                   acute exposures (see RTI, 2005;
                                                                                                                      ICF, 2006b).
NTP, 2003.........................  Female and male       0, 62.5, 125, 250,    Early mortality in mice at 500 ppm   Unpublished study. Conclusions
                                     B6C3F1 mice and       500 (rats and         accompanied by liver and lung cell   drawn from a review of raw data
                                     Fischer 344 rats.     mice), 1000 (rats)    degeneration and cytoplasmic         from the National Toxicology
                                                           ppm for 90 days.      vacuolization. Cytoplasmic           Program (NTP) Web site. In
                                                                                 vacuolization also in rat liver      general, the severity of effects
                                                                                 cells >= 250 ppm (males) and >=      (in non-reproductive organs) is
                                                                                 500 ppm (females), with increased    slightly higher at lower
                                                                                 severity at higher doses. No         concentrations in male rats than
                                                                                 adverse central nervous system       in females.
                                                                                 (CNS) effects or histopathology
                                                                                 reported.
RTI, 2005/Garner et al., 2006.....  Female and male       Exposure via several  nPB cleared by mice after 48 hours   The study authors concluded that:
                                     B6C3F1mice and        injection routes      as follows: 45% as volatiles in      nPB administered via
                                     Fisher 344N rats,     (intraperitoneal,     the breath, 28% as CO2 in the        intraperitoneal injection or
                                     four to six animals   intravenous,          breath, 26% in urine, <3% in         inhalation is eliminated mostly
                                     in each test trial.   cannuliz-ation),      feces, and 2% retained in the        through the breath, with urine as
                                                           inhalation, and       body. Distribution was similar in    a secondary path.
                                                           dermal. Injection     male rats, although amounts in       Metabolism of nPB appears
                                                           conducted via bolus   urine and volatiles in breath were   to be primarily through cytochrome
                                                           dosing at 5, 20, or   higher in mice. At higher doses,     P450 enzymes (CYP2E1),
                                                           100 mg/kg body        the amount of nPB excreted in        particularly in mice; glutathione
                                                           weight. Inhalation    urine and as CO2 decreased, with a   conjugation still plays an
                                                           concentrations of     much greater change in rats          important role in rats.
                                                           70, 240, 800, and     compared to mice.                    At high concentrations,
                                                           2700 ppm              After pretreatment with a    female rats may have a decreased
                                                           administered in a     cytochrome P450 inhibitor, a         capacity to metabolize nPB
                                                           single acute          decrease in nPB cleared as CO2       compared to male rats.
                                                           exposure. A dose of   (80%) and urine (40%);               nPB decreases glutathione
                                                           96 mg/kg was          pretreatment with a glutathione      levels in the liver after a one-
                                                           applied to a shaved   inhibitor reduced nPB cleared as     time exposure to nPB at
                                                           area on the backs     CO2 by 10% and urine by 4%.          concentrations as low as 70 ppm.
                                                           of six male rats      The Vmax, a measure of the   nPB is not appreciably
                                                           with a non-           maximum initial rate of an enzyme-   absorbed (~3-27%) in rats
                                                           occlusive charcoal    catalysed reaction, is 0.227 for     following dermal application.
                                                           filter covering       male rats, 0.143 for female rats,   EPA agrees with these points,
                                                           (that is, one that    0.329 for male mice and 0.234 for    except we found that gender
                                                           does not prevent      female mice. Half-lives were         differences were only apparent in
                                                           evaporation).         comparable between males and         rats at very high concentrations
                                                                                 females at <= 800 ppm.               (2700 ppm and greater). We also
                                                                                 For rats exposed to nPB      note that:
                                                                                 through skin, 37% of the dose was    Inhalation tests were only
                                                                                 excreted in volatiles, 1.2 % in      one-time exposures at very high
                                                                                 urine, 1.7% as CO2, and 35.7% was    concentrations (240 to 2700 ppm),
                                                                                 on the applicators or in the skin    and thus, are not comparable to
                                                                                 washes. Only 0.32% remained in       long-term dosing at the lower
                                                                                 tissues. Airborne concentrations     levels expected in the workplace.
                                                                                 of nPB in the chamber were 4 to 10   Results of dermal testing
                                                                                 ppm after dosing.                    are not conclusive because of
                                                                                                                      potential for inhalation exposure.
Sohn et al., 2002.................  40 male and 40        6 hr/day, 5 day/wk    No effects on mortality, activity,   The differences between the various
                                     female Sprague-       for 13 weeks, test    weight gain, food consumption,       studies may be due to variability
                                     Dawley rats.          groups (10/sex/       urinalysis, or histological          in exposure methodology and
                                                           dose) were exposed    effects in the brains and spinal     achieved concentrations of nPB.
                                                           to 0, 200, 500 or     cords.
                                                           1250 ppm.
Stump, 2005*......................  125 female/125 male   Both test groups of   Decreased litter size at 250 and     Reproductive effects seen in both
                                     rats in first         25 male rats/ 25      500 ppm in both generations.         rat sexes which is a strong signal
                                     generation and 100    female rats exposed   Decreased fertility at 100 and 250   of reproductive toxicity potential
                                     female/100 male       to 0, 100, 200,       ppm in offspring generation.         in humans. The author considers
                                     rats in offspring     250, 500 and 750     Complete infertility at 750 ppm....   100 ppm to be a lowest observed
                                     generation.           ppm nPB for 10                                             adverse effect level (LOAEL). This
                                                           weeks.                                                     is a presentation of data from
                                                                                                                      WIL, 2001.
Wang et al., 2003.................  36 male Wistar rats.  8 hr/day, 5 day/wk    Decrease in creatine kinase in the   Small study size. No behavioral
                                                           for 12 weeks, test    spinal cord (17% at >= 200 ppm)      changes or physical symptoms were
                                                           groups ( 9 rats)      and brain (15-28% at >= 400 ppm)     observed in the animals, so the
                                                           were exposed to 0,    at 200, 400, and 800 ppm. No         toxicological relevance of the
                                                           200, 400 or 800 ppm.  physical or behavioral changes       decrease in creatine kinase is
                                                                                 observed.                            questionable.
Yamada et al., 2003...............  40 female Wistar      8 hr/day, 7 day/wk    All rats at 800 ppm became           Data suggest that nPB is affecting
                                     rats.                 with test groups (9/  seriously ill after 7 weeks of       the maturation of ovarian
                                                           dose) exposed to 0,   exposure. Significant decrease in    follicles. A no observed adverse
                                                           200, 400, or 800      antral follicles at >= 200 ppm,      effect level (NOAEL) of 200 ppm is
                                                           ppm for 12 weeks.     and a decrease in the number of      identified with a LOAEL of 400 ppm
                                                                                 female rats exhibiting regular       for the changes in estrus cycles.
                                                                                 estrous cycles in 400-ppm females
                                                                                 during 7-9 weeks of exposure and
                                                                                 at 2-3 weeks at the 800-ppm dose.
--------------------------------------------------------------------------------------------------------------------------------------------------------
* Presentation at North American Congress of Clinical Toxicology on September 14, 2005


[[Page 30183]]

     In general, the recent animal studies collectively show a 
range of effects associated with nPB exposure that are qualitatively 
consistent with previously published findings. (Exceptions to this are 
the negative results regarding central nervous system toxicity in the 
NTP (2003) study and the Sohn (2002) study on rats.) Some general 
conclusions we draw from the new studies include:
     Case reports of nPB exposure in the workplace indicate 
that severe, possibly irreversible, neurological effects may occur at 
sustained concentrations of approximately 100 ppm or greater (Beck and 
Caravati, 2003; Majersik et al, 2004; Majersik et al., 2005; Ichihara 
et al., 2002a; Miller, 2005; Raymond and Ford, 2005). In other cases, 
similar or higher concentrations up to 170 ppm caused less severe 
nervous system effects (Nemhauser, 2005; NIOSH, 2003a; Ichihara, 
2004a). Some neurological effects occurred in workers at levels of less 
than 50 ppm (Ichihara et al., 2004b). Because of design and 
methodological limitations, such as small numbers of subjects and 
limited exposure information, these studies do not provide a sufficient 
quantitative basis to derive an acceptable exposure limit.
     Data on female rats indicate that nPB affects the 
maturation of ovarian follicles and the ovarian cycle (Yamada et al., 
2003), consistent with previously reviewed data (WIL , 2001; Sekiguchi 
et al., 2002).
     Some data on occupation exposure suggest that workers 
exposed to nPB may have experienced menstrual disorders (Ichihara et 
al., 2002; Ichihara et al., 2004b). However, the data are not 
statistically significant and are not sufficient to conclude that nPB 
exposure caused these female reproductive effects.
     Data on DNA damage in workers exposed to nPB was not 
statistically significant (Toraason et al., 2006).
     Metabolic data on mice and rats indicate some species 
differences. Metabolism of nPB appears to be primarily through 
cytochrome P450 enzymes, particularly in mice; glutathione conjugation 
also plays a role, and a bigger role for rats than for mice (RTI, 
2005).
     New data from toxicological studies on nervous system 
effects remain inconsistent and equivocal concerning the level at which 
nervous system effects occur (Fueta et al., 2002; Fueta et al., 2004; 
Honma et al., 2003; Ishidao et al., 2002, NTP, 2003; Sohn et al. 2002, 
Wang et al., 2003).
    A number of commenters on the June 2003 NPRM suggested that EPA 
should consider neurotoxicity as the endpoint in deriving an AEL for 
nPB (Linnell, 2003; Werner, 2003; Rusch and Bernhardt, 2003, Rusch, 
2003). In particular, they requested that EPA consider the study 
conducted by Wang (2003) and epidemiological data on neurotoxic effects 
of nPB. As discussed above, the data on neurotoxic effects of nPB on 
workers are limited and are not sufficient to determine acceptable 
levels of exposure. In the study on rats by Wang et. al. (2003), 
measurements found a decrease in enzymes in the spinal cord and brain 
at 200, 400, and 800 ppm, but the animals displayed no physical or 
behavioral changes. Because of the lack of physical symptoms or 
behavioral changes, EPA does not believe that the decrease in enzyme 
levels in the central nervous system are toxicologically relevant. 
Other studies examining neurological effects of nPB showed those 
effects to be transient and reversible at and above 200 ppm (Ichihara 
et al., 2000a). Exposures of 200 ppm and above for three weeks had no 
effect on memory, learning function, or coordination of limbs (Honma, 
2003); the effect of spontaneous locomotor activity seen in this study 
at 50 ppm and above was not considered adverse by the authors. In other 
studies, neurological effects were absent after extended periods of 
exposure-after 28 days of exposure at concentrations > 400 ppm 
(ClinTrials, 1997a) and after 90 days of exposure at concentrations up 
to 600 ppm (ClinTrials, 1997b). Thus, although neurological effects 
have been associated with nPB exposure, the data are currently 
insufficient to quantify and determine acceptable exposure levels based 
on this endpoint.
    One commenter on the June 2003 NPRM requested that EPA evaluate a 
study by Yamada et al. (2003), a study published just prior to the June 
2003 NPRM. In response to the comment, EPA reexamined Yamada et al., 
2003 and re-evaluated the literature (Ichihara et al., 1999, 2002, 
2004a,b; Sekiguchi, 2002, Yamada et al., 2003; WIL, 2001) to assess 
potential reproductive toxicity in females (ICF, 2006a, Att. A). A peer 
review of these effects is in the public docket (ICF, 2004b). Multiple 
benchmark analyses found a statistically significant decrease in the 
number of estrous cycles and increase in estrous cycle length 
associated with nPB exposure, consistent with other reproductive 
endpoints, namely reductions in sperm motility, decreased live litter 
size, and change in prostate weight (ICF, 2002a; ICF, 2006a; Stelljes 
and Wood, 2004; TERA, 2004).
    Reproductive effects are seen in males, females, and offspring, and 
in different generations of the two-generation study (WIL, 2000). They 
also are consistent with results seen in one-generation reproductive 
studies, such as Ichihara et al. (2000b) and Yamada (2003). See Table 6 
above in section IV.E.1. for a more complete list of the different 
health effects. EPA believes that the preponderance of the data 
indicate that exposure levels sufficient to protect against male 
reproductive effects (e.g., reduced sperm motility) would be in a range 
from 18 to 30 ppm, in the range of 17 to 22 ppm to protect against 
female reproductive effects (e.g., number and length of estrous 
cycles), and at approximately 20 ppm for effects related to 
reproductive success (live litter size). We have not determined what 
specific level within those ranges (an overall range of 17 to 30 ppm) 
is most appropriate for evaluating whether a substitute may be used 
safely and consider these exposure levels to be potentially acceptable. 
Therefore, we assessed the acceptability of nPB by considering whether 
it could be used safely in the three end-uses. For end-uses with 
likelihood of exposures above the range we are considering, while 
following typical industry practices, we are proposing an 
unacceptability determination. For end-uses that as their normal 
practice meet exposure levels below the range we are considering, we 
are proposing an acceptability determination. It is not necessary for 
100% of exposure data for an end use to be above or below the range of 
17 to 30 ppm in order to make a determination on the acceptability of 
an end use because there may be occasional cases that are not following 
common industry practices. Unusual events would not indicate the 
industry's likelihood of keeping exposures at safe levels, and thus, 
should not be the determining factor in our decision. Rather, we 
consider the overall likelihood that typical industry use would 
consistently result in acceptably low or unacceptably high exposures.
    In the June 2003 NPRM, EPA used a BMDL of 169 ppm as a point of 
departure for developing an AEL. Some commenters stated that data from 
the F1 generation is inappropriate for calculating occupational 
exposure, citing statements from toxicologists, such as, ``occupational 
exposure involves adults only.'' They also stated that EPA has not 
required this for other chemicals and that the resulting value is more 
conservative than what is normal and appropriate for industrial 
toxicology (Morford, 2003f, Ruckriegel, 2003). Others stated that sperm 
motility effects on the F1 generation are appropriate to consider 
(Risotto, 2003; Farr, 2003), particularly because of the

[[Page 30184]]

potential for in utero effects and because of the consistent presence 
of these reproductive effects in both generations and at multiple 
levels. EPA acknowledges that using data from the F1 offspring 
generation may be conservative because the pups in the F1 generation 
were exposed to nPB between weaning and sexual maturity (WIL, 2001). 
During occupational exposure, this period of exposure would not occur 
because children under age 16 are not allowed to work in industrial 
settings. However, EPA believes that because of the potential for in 
utero effects that would only be seen in the offspring generation, 
looking only at the F0 parental generation could underestimate the 
adverse health impacts of a chemical. Therefore, we believe it is 
appropriate to consider effects seen in both the F0 parental generation 
and the F1 offspring generation. Further, effects on sperm motility in 
the parental and offspring generations are seen at levels generally 
consistent with multiple reproductive effects seen in both generations 
and both sexes exposed to nPB, such as estrous cycle length, lack of 
estrous cycling, the number of estrous cycles in a given period of 
time, fertility indices, and the number of live pup births (TERA, 2004; 
ICF, 2006a; SLR International, 2001). Therefore, we believe that the 
available data indicate that in order to protect against adverse 
reproductive effects, an exposure level within the range of 17 to 30 
ppm, would potentially be acceptable. We would reach the same proposed 
decisions of unacceptability based upon data from the F0 generation.

C. Evaluation of Acceptable Exposure Levels for the Workplace

    To calculate acceptable exposure levels for nPB, EPA uses standard 
risk assessment methods delineated in Agency guidance (U.S. EPA, 1994b) 
in evaluating data, choosing a benchmark dose level or a NOAEL, and 
making the adjustments and uncertainty factors prescribed to account 
for differences in the duration of exposure and in sensitivity between 
and within species.
Adjustment for Occupational Exposure Pattern
    To account for differences between the exposure pattern used in the 
WIL study (6 hours per day for 7 days per week) when compared to a 
typical workweek of 8 hours per day and 5 days a week, a ``human 
equivalent concentration'' (HEC) is first calculated by adjusting the 
benchmark dose level:

(BMDL in ppm x 6 hours/8 hours) x 7 days/5 days = HEC (ppm)

HECs for the major health endpoints are shown in Table 6 above in 
section IV.E.1.
Uncertainty Factors

    According to EPA risk assessment guidance for reference 
concentrations (RfC) (EPA 1994a), uncertainty factors of up to 10 may 
be applied to the HEC for each of the following conditions:
    (1) Data from animal studies are used to estimate effects on 
humans;
    (2) Data on healthy people or animals are adjusted to account for 
variations in sensitivity among members of the human population (inter-
individual variability);
    (3) Data from subchronic studies are used to provide estimates for 
chronic exposure;
    (4) Studies that only provide a LOAEL rather than a NOAEL or 
benchmark dose; or
    (5) An incomplete database of toxicity information exists for the 
chemical.
    EPA believes that two uncertainty factors are appropriate for this 
database to account for that: (1) Physiological differences between 
humans and rats; and (2) variability within the working population. The 
rationale for the use of these two uncertainty factors is described 
below.
    EPA RfC guidelines state that an uncertainty factor of 10 may be 
used for potential differences between study animals and humans. This 
factor of 10 consists in turn of two uncertainty factors of 3--the 
first to account for differences in pharmacodynamics \14\ and the 
second to account for differences in pharmacokinetics \15\ between the 
study of animal and humans. (The value of three is the square root of 
10 rounded to one digit, with 10 representing an order of magnitude 
(EPA,1994a). In practice, EPA uses the square root of 10 when there are 
two or four uncertainty factors of 3, yielding a total uncertainty 
factor of 10 or 100, and we use a value of 3 when multiplying by an 
uncertainty factor of 10). By EPA RfC guidelines (U.S. EPA, 1994b), no 
adjustment for differences in pharmacokinetics is necessary in this 
instance because the blood/air partition coefficient \16\ for nPB in 
the human (7.1) is less than in the rat (11.7), indicating that the 
delivered dose of nPB into the bloodstream in rats is slightly higher 
than in humans. Consistent with Appendix J of EPA's RfC guidelines for 
an inhaled compound that exerts its effects through the bloodstream, 
EPA applies an uncertainty factor of 1 for pharmacokinetics.
---------------------------------------------------------------------------

    \14\ Pharmacodynamics refers to the biochemical and 
physiological effects of chemicals in the body and the mechanism of 
their actions.
    \15\ Pharmacokinetics refers to the activity or fate of 
chemicals in the body, including the processes of absorption, 
distribution, localization in tissues, biotransformation, and 
excretion.
    \16\ The blood/air partition coefficient is the ratio of a 
chemical's concentration between blood and air when at equilibrium.
---------------------------------------------------------------------------

However, EPA recognizes that the lack of an uncertainty adjustment for 
pharmacokinetic differences between animals and humans rests on a 
default approach applied to category 3 gases described in Appendix J of 
its guidelines for deriving an inhalation RfC. This default approach 
assumes that nPB's toxicokinetics follow a model in which: (1) The 
toxicity is directly related to the inhaled parent compound in the 
arterial blood, and (2) the critical metabolic pathways scale across 
species, with respect to body weight, in the same way as the 
ventilation rate. Given the hypothesized metabolic pathways for nPB 
(ICF, 2002a; CERHR, 2002a), it is plausible that toxicity in rats may 
be related to a reactive metabolite in the target tissue rather than 
the blood level of the parent compound. EPA is not aware of any 
quantitative data on nPB metabolism in humans, or evidence implicating 
the biologically active agent or mode of action. Some commenters on the 
June 2003 NPRM stated that EPA should use an uncertainty factor of 1 or 
2 to extrapolate from animals to humans (Weiss Cohen, 2003), while 
others suggested uncertainty factors of 2 or 3 for pharmacokinetics, or 
an overall uncertainty factor of 10 for rat to human extrapolation 
because of a lack of information on the metabolism and mode of action 
of nPB and because the rat is an insensitive model for effects on male 
reproduction in humans (Werner, 2003; Rusch and Bernhardt, 2003). 
Commenters provided no data to indicate that (1) the toxicity is not 
directly related to the inhaled parent compound in the arterial blood, 
or (2) the critical metabolic pathways do not scale across species, 
with respect to body weight, in the same way as the ventilation rate. 
Recent studies provide additional data regarding metabolism of nPB in 
rats and mice (RTI, 2005), but data on human metabolism are still 
lacking.
    One analysis of these metabolic data suggested that mice are less 
sensitive to the effects of nPB than rats and hypothesized that humans 
would also be less sensitive than rats (Stelljes, 2005). However, this 
analysis makes numerous assumptions about toxic nPB metabolites and 
metabolic activation pathways that have not been confirmed by 
experimental data. A review of this

[[Page 30185]]

analysis is available in the public docket (ICF, 2006c). Despite the 
difference in metabolic pathways for nPB in mice and rats (RTI, 2005), 
EPA finds no significant species-specific differences in toxicity exist 
between rats and mice at inhaled concentrations <500 ppm for 13 weeks 
(NTP, 2003; ICF, 2006b). These metabolic and subchronic inhalation 
studies conducted under the National Toxicology Program did not 
specifically examine for reproductive toxicity or nPB metabolism in 
target organs that control reproductive function. In summary, there are 
little available data about the metabolic activation or reactive 
metabolites responsible for reproductive toxicity in rodents. 
Similarly, for nPB, there is little information available about 
differences and similarities between rodents and humans. Given this 
circumstance, EPA assumes, in the absence of evidence to the contrary, 
that nPB toxicity is directly related to the inhaled parent compound in 
the arterial blood and that the critical metabolic pathways scale 
across species in a manner similar to the ventilation rate. Therefore, 
the Agency is proposing to apply an uncertainty factor of 1 to account 
for interspecies differences in pharmacokinetics.
    EPA requests additional data and comment from the public on the 
pharmacokinetics, metabolism, and mode of action of nPB that will help 
determine whether an interspecies uncertainty factor greater than the 
default value of 1 is warranted to account for pharmacokinetics. If 
data become available indicating that nPB does not conform to the 
constraints assumed by the default pharmacokinetic model in the RfC 
guidelines, we would revise our risk assessment for nPB as necessary, 
and apply an uncertainty factor for pharmacokinetics consistent with 
the RfC guidelines in extrapolating from animal to humans. Depending on 
the resulting difference in the acceptable exposure levels, we would 
also revise our acceptability determinations accordingly. Given the 
available data on the blood/air partition coefficient and EPA RfC 
guidance in the absence of other information, EPA is applying the same 
rationale used for other compounds reviewed under EPA's SNAP program 
with a comparable amount of data where an uncertainty factor of 1 for 
pharmacokinetics was applied. To account for uncertainty in 
pharmacodynamics of nPB, EPA is applying the default uncertainty factor 
of 3. This follows the procedures in EPA's RfC guidelines for 
situations where there are no data to compare pharmacodynamics in rats 
versus humans (U.S. EPA, 1994b). Recently published data on humans and 
rodents do not decrease the uncertainty regarding the pharmacodynamics 
of nPB; therefore, modification of the uncertainty factor of 3 for 
differences between species is not justified.
    One commenter stated that EPA did not cite any data that describes 
the size, condition, or very existence of a subpopulation of men 
especially sensitive to the effects of nPB. In addition, this commenter 
asserted that sensitive populations are not traditionally considered 
when deriving an occupational exposure limit, and that EPA has never 
mentioned a concern with sensitive subpopulations in previous SNAP 
reviews.
    EPA disagrees with the comments. There are preexisting reproductive 
conditions as well as significant variability in fertility among 
otherwise healthy adults in the workplace. Women over age 35 and men 
over age 40 have fertility rates up to three times lower than those of 
people in their twenties, with effects on the ovarian cycle and on 
sperm motility as major factors changing with increasing age for women 
and men, respectively (Dunson et al., 2002). Adding damage from other 
factors, such as smoking or occupation exposure to chemicals such as 
nPB, therefore, can potentially harm an individual's ability to 
reproduce further (Dunson, et al. 2002). In addition, we note that EPA 
has used uncertainty factors in the past to protect sensitive 
subpopulations on other chemicals reviewed under the SNAP program 
(e.g., trifluoroiodomethane at 69 FR 58907, October 1, 2004). For 
deriving AELs from health endpoints such as liver effects and 
neurotoxicity, the SNAP program typically has assigned an uncertainty 
factor of 1 for sensitive subpopulations because we assume that 
individuals who are especially susceptible to these effects will have 
greater difficulty working than most people. However, there is no 
connection between the ability to reproduce and the ability to work in 
the industrial sectors discussed in this rule. Thus, we find it 
appropriate to apply an uncertainty factor greater than 1 for 
reproductive effects.
    Some commenters on the June 2003 NPRM said that an uncertainty 
factor of 1 is appropriate for variability within the working 
population because sensitive subpopulations will not be present in the 
working population (Stelljes, 2003, Morford, 2003f). Other commenters 
stated that there will be very little difference in variability between 
the worker population and the general population and that it is unclear 
why EPA selected an uncertainty factor of 3 instead of 10 (Werner, 
2003). Commenters suggested uncertainty factors for variability in the 
working population of 1, 2, and 5 (Stelljes, 2003; Weiss Cohen, 2003; 
Werner, 2003).
    EPA's RfC guidelines recommend an uncertainty factor of 10 to 
account for intraspecies variability within the general population. 
However, in deriving an acceptable exposure limit, EPA's focus is on 
worker exposure, which excludes some particularly vulnerable 
populations, such as children, most adolescents, and the elderly. Thus, 
we believe that a full uncertainty factor of 10, as for the general 
population, may be higher than necessary to protect workers. However, 
because of variability in reproductive function due to factors present 
among workers, such as aging, smoking, and sexually transmitted 
disease, and because there is no screening of workers that would make 
workers more likely to have healthy reproductive systems than non-
workers of the same age, we believe than an uncertainty factor of 1 is 
not sufficiently protective. Under EPA guidelines, 3 is a default value 
for an uncertainty factor where there is indication that a value less 
than an order of magnitude (10) but greater than one is appropriate, 
and where the available data are not sufficiently quantified to select 
a specific value. Therefore, EPA is again proposing to assign an 
uncertainty factor of 3 to account for difference between individuals 
in the working population.
    The uncertainty factors of 3 for animal-human extrapolation and 3 
for variability within the human working population (each representing 
the square root of ten, half an order of magnitude) yield a composite 
uncertainty factor of 10. This factor was applied to all HECs derived 
from reproductive studies summarized in Table 6 in section IV.E.1 
above. The resultant values are higher than the value that would have 
been obtained had EPA used the TLV of 10 ppm developed by the ACGIH. 
EPA believes that the benchmark dose approach more accurately 
characterizes the observed effects and provides a more robust 
utilization of the data.

D. Other Analyses of nPB Toxicity

Analyses Reviewed During Preparation of June 2003 NPRM
    One commenter on the June 2003 NPRM stated that documents by Drs. 
Doull, Rozman, Stelljes, Murray, Rodricks, and the KS Crump Group were 
not acknowledged (Morford, 2003f, g, and h). EPA specifically mentioned

[[Page 30186]]

and responded to the occupational exposure limit recommendations from 
Drs. Rozman, Doull, and Stelljes in the preamble to the June 2003 NPRM 
at 68 FR 33298-33299. In addition, EPA included more detailed written 
responses to these derivations and the evaluation by Dr. Rodricks in 
the online docket prior to proposal (EPA-HQ-OAR-2002-0064-0017, -0018, 
and -0019). We considered these documents in preparation of the June 
2003 proposal as well as this proposal.
    In general, we disagree that the neurotoxicity endpoint selected by 
Drs. Rozman and Doull is the most appropriate endpoint for setting an 
AEL and we agree with Dr. Stelljes that sperm motility in the F1 
offspring generation of the WIL, 2001 2-generation study is an 
appropriate endpoint. We agree with a number of these documents that 
data from the F1 generation may be conservative because workplace 
exposure would not include exposure to the F1 animals during the four-
week period from weaning to sexual maturity. However, EPA believes that 
because of the potential for in utero effects that would only be seen 
in the offspring generation, looking only at the F0 parental generation 
could underestimate the adverse health impacts of a chemical. 
Therefore, it was appropriate for us to consider effects seen in both 
the F0 parental generation and the F1 offspring generation. Further, 
effects on sperm motility in the parental and offspring generations are 
seen at levels generally consistent with multiple reproductive effects 
seen in both generations and both sexes exposed to nPB, such as estrous 
cycle length, lack of estrous cycling, the number of estrous cycles in 
a 3-week period, and the number of live pup births (TERA, 2004; ICF, 
2006a; SLR International, 2001; Stelljes and Wood, 2004). We believe 
that the document from the K. S. Crump group, a survey of the ratio of 
points of departure to TLVs set by the ACGIH, is not relevant now that 
the ACGIH has issued a TLV specifically for nPB. ACGIH appears to set 
an AEL for nPB that is a factor of 10 lower than the endpoint cited as 
lowest (100 ppm for effects on pup weight) (ACGIH, 2005). Thus, ACGIH 
has used an approach for nPB consistent with the total uncertainty 
factor of 10 assigned by EPA. In general, we find that these documents 
submitted by the commenter assigned uncertainty factors in a manner 
inconsistent with EPA guidance. This would result in a higher AEL than 
we would determine following the approach EPA has used on other 
chemicals, as well as an AEL that in our view would not sufficiently 
protect human health from nPB's effects because of multiple sources of 
uncertainty in available data (e.g., variability within the working 
population, differences between animals and humans in how nPB affects 
the reproductive system).
    Since the 2003 NPRM, a number of reviews of nPB toxicity have been 
issued, several of which include recommendations for occupational 
exposure limits. CERHR, 2003a and 2004a are similar to CERHR, 2002a, 
the expert panel report for nPB for the Center for the Evaluation of 
Risks to Human Reproduction (CERHR). CERHR, 2003b and 2004b are similar 
to CERHR, 2002b, the CERHR expert panel's report for iPB. These 
documents discuss the usefulness of data in available studies for 
assessing nPB's health impacts and establish No Observed Adverse 
Concentration levels of 100 ppm for both male and female reproductive 
effects in animals, but do not derive an AEL. Rozman and Doull, 2005 
derived an AEL of 25 ppm for nPB based on neurotoxicity, using more 
recent information than Rozman and Doull, 2002.
    The Stelljes and Wood (2004) analysis is similar in its results to 
SLR International (2001), a study by the same authors. EPA previously 
reviewed SLR International, 2001 in developing the June 2003 NPRM. Both 
studies by Stelljes and Wood concluded with a recommended AEL of 156 
ppm, based on male reproductive effects and uncertainty factors of 1 in 
driving the AEL. Stelljes (2005) reviews RTI's 2005 study on metabolism 
of nPB in mice and rats and other literature and speculates that humans 
should be less sensitive to nPB than either mice or rats based on 
differences in metabolite production. Stelljes (2005) recommends that 
no uncertainty factor is required to extrapolate from animals to humans 
and that an uncertainty factor of no more than 2 is appropriate to 
account for differences within the working population. All of these 
documents assigned uncertainty factors in a manner that is not 
sufficiently supported by the available data and that is inconsistent 
with EPA's guidance. For example, Stelljes (2005) discusses metabolic 
data in rats and mice from RTI, 2005 and concludes that on this basis, 
the uncertainty factor for extrapolation from animals to humans should 
be 1. However, the metabolic data relate to pharmacokinetics--the 
activity of chemicals in the body--and do not address EPA's proposed 
uncertainty factor of 3 related to pharmacodynamics (the biochemical 
and physiological effects of chemicals in the body and the mechanism of 
their actions). Using the AEL from one of these documents would result 
in a higher, less protective AEL than we would determine following the 
approach EPA has used for other chemicals under the SNAP program and 
would not consider multiple sources of uncertainty in health effects 
(i.e., variability within the working population and differences 
between animals and humans in how nPB affects the reproductive system). 
Thus, we are concerned that the AELs based on these documents would not 
be sufficiently protective and would result in an inappropriate 
acceptability decision. Detailed reviews of these documents are 
available in the public docket.
    Toxicological Excellence in Risk Assessment (TERA), 2004 reviews 
other AEL derivations for nPB, performs a benchmark dose (BMD) 
analysis, and recommends an AEL of 20 ppm based on live litter size. 
This analysis is consistent with EPA guidance for BMD modeling and for 
assigning uncertainty factors. A review of this document is available 
in the public docket (ICF, 2004c).
    ICF (2004b, 2006a) derived an AEL for nPB based upon female 
reproductive effects. ICF (2004b, 2006a) discussed the relevant 
literature (Ichihara et al., 1999, 2002, 2004a, 2004b; Sekiguchi, 2002; 
Yamada et al., 2003; WIL, 2001) and calculated mean estrous cycle 
length and the mean number of estrous cycles occurring during a three-
week period at different exposure levels in the WIL, 2001 2-generation 
study. ICF (2004b, 2006a) found statistically significant reductions in 
the number of estrous cycles in a three-week period, both including and 
excluding females that had stopped their estrous cycles, at 250, 500, 
and 750 ppm in the F0 parental generation and at 500 and 750 ppm in the 
F1 generation. ICF (2004b, 2006a) conducted BMD modeling and calculated 
BMDL values of the number of estrous cycles in a three-week period that 
varied from 102 to 208 ppm, depending upon the model used and the 
benchmark criteria selected. All data were calculated based on the mean 
reductions in estrous cycle number calculated from the WIL, 2001 study. 
Values were calculated for the F0 generation; the number of data for 
the F1 generation was too small for statistical analysis. The BMDLs 
that ICF calculated for the number of estrous cycles in a three-week 
period were 162 ppm and 208 ppm, depending on the benchmark response 
criteria (10% change in response vs. one standard

[[Page 30187]]

deviation) and using a linear-heterogeneous model.
    The California Environmental Protection Agency's Office of 
Environmental Health Hazard Assessment (OEHHA) listed both nPB and iPB 
as reproductive toxins on the basis of developmental, male 
reproductive, and female reproductive toxicity under the State's Safe 
Drinking Water and Toxic Enforcement Act of 1986, also known as 
Proposition 65 (OEHHA, 2006). Under this law, California is required to 
list chemicals known to be carcinogenic or to be reproductive toxins 
and to update that list at least annually.
    The American Conference of Government Industrial Hygienists (ACGIH) 
issued a recommended Threshold Limit ValueTM (TLV) of 10 ppm 
(time-weighted average) for nPB (ACGIH, 2005). ACGIH summarized 
numerous studies showing different effects of nPB and identified no 
observed effect levels (NOELs) of 200 ppm for hepatotoxicity 
(ClinTrials, 1997b) and less than 100 ppm for developmental toxicity, 
as evidenced by decreased fetal weight (Huntingdon Life Sciences, 
2001).
    OSHA has not developed a permissible exposure limit (PEL) for nPB 
that EPA could use to evaluate toxicity risks \17\ from workplace 
exposure. In prior SNAP reviews, EPA has used ACGIH TLVs where 
available in assessing a chemical's risks and determining its 
acceptability if OSHA has not set a PEL. ACGIH is recognized as an 
independent, scientifically knowledgeable organization with expertise 
in issues of toxicity and industrial hygiene. However, in this case, 
EPA believes that ACGIH's TLV for nPB of 10 ppm has significant 
limitations as a reliable basis for an acceptable exposure limit, 
especially given the availability of other, more comprehensive analyses 
described in this proposal. First, according to the authors of the 
Huntingdon Life Sciences study, the decrease in fetal weight was an 
artifact of sampling procedure that biased the data (test animals were 
only sacrificed at the end of the day rather than at random). The CERHR 
expert panel excluded ``aberrantly low'' fetal weights from one litter 
in this study and calculated a BMDL greater than 300 ppm for this 
endpoint after removing those outlier data (CERHR, 2002a, 2003a, and 
2004a). TERA calculated a similar BMDL when analyzing the same data set 
(TERA, 2004). Further, the reference list in the documentation on the 
TLV indicates that ACGIH did not review and evaluate all the studies 
available prior to the development of the recommended exposure limit. 
For example, key supporting articles that reported disruption of 
estrous cycles (Yamada et al., 2003 and Sekiguchi et al., 2002) were 
not discussed in the TLV documentation. Further, ACGIH did not provide 
sufficient reasoning for the selection of the chosen endpoint over 
others (e.g., reproductive toxicity and/or neurotoxicity). The lack of 
discussion of applied uncertainty factors also prevents a determination 
of how ACGIH arrived at a TLV of 10 ppm. In summary, EPA is not basing 
its proposed acceptability determination for nPB on the ACGIH TLV 
because: (1) Other scientists evaluating the database for nPB did not 
find the reduced pup weight to be the most sensitive endpoint; (2) 
benchmark dose (BMD) analysis of the reduced pup weight data (CERHR, 
2002a; TERA, 2004) results in a higher BMDL (roughly 300 ppm) than 
those for reproductive effects; and (3) ACGIH may not have reviewed the 
complete body of literature as several studies discussing neurotoxicity 
and female reproductive effects were omitted from the list of 
references. A number of reviews of this document are available in the 
public docket (ICF, 2004d; O'Malley, 2004).
---------------------------------------------------------------------------

    \17\ Vendors of nPB-based products have recommended a wide range 
of exposure limits, from 5 ppm to 100 ppm (Albemarle, 2003; 
Chemtura, 2006; Docket A-2001-07, item II-D-19; Enviro Tech 
International, 2006; Farr, 2003; Great Lakes Chemical Company, 
2001).
---------------------------------------------------------------------------

    We note that, even if EPA had selected the ACGIH TLV as our basis 
for assessing the risks of nPB, we would have proposed the same 
determinations. In the specific coatings application that we propose to 
find acceptable subject to use conditions at the Lake City Army 
Ammunition Plant, exposure data showed an ability to meet an exposure 
level of 10 ppm, with the vast majority of measurements below that 
value. Thirty-four of 35 samples had concentrations below 10 ppm, and 
the mean concentration for the plant was less than 4 ppm (Lake City 
Army Ammunition Plant, 2004). For the aerosol and adhesive end uses, it 
would be even more difficult to achieve an exposure level of 10 ppm 
than to achieve a level in the range that EPA is considering (17 to 30 
ppm). Thus, we would have proposed the same decisions for nPB of 
acceptable, subject to use conditions for coatings and unacceptable for 
aerosols and adhesives using the ACGIH's TLV of 10 ppm to assess health 
risks. Despite some flaws in its derivation, the TLV of 10 ppm is less 
than two-fold lower than the low end of the range of acceptable 
exposure levels based on the most sensitive reproductive endpoints. 
This small difference is well within the uncertainty required to 
extrapolate a benchmark dose from an experimental study in rats to an 
occupational exposure limit in humans.

E. Community Exposure Guideline

    In this proposal, EPA is using a community exposure guideline (CEG) 
of 1 ppm to evaluate potential health risks among populations living 
near facilities using nPB. This community exposure guideline is an 
estimate of a continuous inhalation exposure (averaged over 24 hours 
per day, 7 days per week) to the general public (including sensitive 
subgroups) that is likely to be without an appreciable risk of adverse 
health effects during a lifetime.
    Based on EPA risk assessment guidelines (US EPA, 1994b), the CEG 
was derived using the lowest BMDL from effects listed in Table 6 as the 
point of departure (110 ppm for vacuolation in the liver of animals in 
the F1 generation of WIL, 2001). The HEC was calculated as follows:

110 ppm x (6 hours exposure in study/24 hours avg time) x (7 days/7 
days) = 28 ppm

    EPA used an uncertainty factor of 3 for extrapolation from animals 
to humans, as discussed above in section VI.A, and an uncertainty 
factor of 10 for variability within the general population, consistent 
with EPA's RfC guidelines. Dividing the HEC of 28 ppm by 30 yields a 
community exposure guideline of approximately 1 ppm. If we had used 
sperm motility (HEC of 42 ppm based on a BMDL of 169 ppm) or number of 
estrous cycles (HEC of 40 ppm based on a BMDL of 162 ppm) as starting 
points, we would calculate the same approximate CEG value. We note 
that, following RfC guidelines, EPA's community exposure guideline 
includes a number of conservative assumptions, including exposure 
adjustments to protect an individual exposed for up to 24 hours a day 
for 70 years (U.S. EPA, 1994b, p. 1-5).
    EPA evaluated general population exposure using EPA's SCREEN3 (U.S. 
EPA, 1995b) air dispersion model to assess the likely maximum 
concentration of nPB from single sources.\18\ EPA used data collected 
from

[[Page 30188]]

actual facilities (Swanson, 2002) to characterize two scenarios: (1) A 
typical large, high-use adhesive application facility where the closest 
resident is 100 meters away; and (2) a smaller facility with average-
use adhesive application in an urban area, where the nearest resident 
is only 3 meters away. The results indicated that modeled exposures in 
either scenario did not exceed the CEG of 1 ppm. The highest exposure 
modeled was 0.24 ppm at a distance of 3 meters away from the source in 
the urban scenario, while most other exposures were at least an order 
of magnitude lower (ICF, 2003; ICF, 2006a). Because the community 
exposure guideline was not exceeded for any of the exposure scenarios 
in this conservative screening approach, EPA has concluded that nPB 
exposure to populations living close to facilities using nPB is not a 
concern for purposes of determining the acceptability of nPB under the 
SNAP program.
---------------------------------------------------------------------------

    \18\ We performed the modeling for a facility using nPB-based 
adhesives because the nPB emissions from this type of facility were 
expected to be higher than those from facilities using nPB for other 
end uses. Thus, if a facility using adhesives would not result in 
emissions exceeding the CEG, facilities using nPB in aerosols or in 
metals, electronics, or precision cleaning also would not result in 
emissions exceeding the CEG.
---------------------------------------------------------------------------

VI. What listing is EPA proposing for each end use, and why?

    In this rule, EPA is proposing to find nPB unacceptable in adhesive 
and aerosol solvent end uses, and acceptable subject to use conditions 
in the coatings end use. The proposed listings, summarized in Table 9, 
are intended to allow the use of nPB where it does not pose a human 
health risk significantly greater than other substitutes and prohibit 
nPB's use where nPB exposure cannot be maintained, or is unlikely to be 
maintained, at even the highest level considered in this proposal 
(i.e., 30 ppm). We also are taking comment on an alternate approach of 
finding nPB acceptable subject to use conditions in the above end uses 
(see Section VII.A).

           Table 9.--Proposed Decisions by End Use and Sector
------------------------------------------------------------------------
                                                      And our proposed
 For nPB in this sector and    Our proposal is to    alternate approach
          end use:                list nPB as:               is:
------------------------------------------------------------------------
Aerosols:
    Aerosol solvents........  Unacceptable........  Acceptable, subject
                                                     to use
                                                     conditions.\2\
Adhesives, Coatings, and
 Inks:
    Coatings................  Acceptable, subject   Acceptable, subject
                               to use conditions     to use
                               \1\.                  conditions.\2\
    Adhesives...............  Unacceptable........  Acceptable, subject
                                                     to use
                                                     conditions.\2\
------------------------------------------------------------------------
\1\ Use of nPB in this end use is limited to coatings at facilities
  that, as of May 30, 2007, have provided EPA information demonstrating
  their ability to maintain acceptable workplace exposures (i.e., the
  Lake City Army Ammunition Plant).
\2\ Use conditions would include proposed requirements that users must
  (1) meet an exposure limit of 20 ppm on an eight-hour time-weighted
  average, (2) monitor workers' exposure to nPB using a personal
  breathing zone sampler on an eight-hour time-weighted average
  initially and periodically (every 6 months or longer, depending on the
  concentration during initial monitoring), and (3) keep records of the
  worker exposure data on site at the facility for at least three years
  from the date of the measurement.

A. Aerosol Solvents

    In this rule, EPA proposes to find nPB unacceptable in the aerosol 
solvent end use. There are a number of aerosol solvent alternatives 
that do not pose any risk for ozone depletion or for ground level smog 
formation.\19\ EPA's greatest concern with nPB-based aerosols is that 
users of nPB as an aerosol solvent cannot reliably maintain exposures 
at sufficiently low levels to ensure that workers are protected. This 
finding is based on measured exposure data and model estimations 
indicating the likelihood of elevated concentrations associated with 
nPB-based aerosols given typical ventilation conditions. A number of 
other acceptable solvent alternatives are available that can be used at 
exposure levels below their respective acceptable exposure limits.
---------------------------------------------------------------------------

    \19\ Smog, also known as ground-level ozone, is produced from 
emissions of volatile organic compounds that react under certain 
conditions of temperature and light.
---------------------------------------------------------------------------

    Ventilation conditions are an important consideration in evaluating 
potential risks within this end-use category. ``Benchtop cleaning'' of 
individual parts, which is feasible under exhaust hoods or in spray 
booths with adequate ventilation, comprises 25% or less of the market 
involving ODS substitutes for aerosols (U.S. EPA, 2004). According to 
industry information and several commenters, the majority of the market 
for nPB-based aerosols involves in-place applications requiring a 
portable aerosol, such as cleaning energized electrical contacts and 
switches, maintenance in underground mines, or cleaning active elevator 
motors (CSMA, 1998; U.S. EPA, 2004; Williams, 2005). These applications 
often occur in tightly confined spaces where it is not feasible to 
install ventilation equipment or remove parts to ventilated areas 
(CSMA, 1998; Linnell, 2003; Werner, 2003). Other acceptable 
substitutes, such as blends of HFEs or HFCs and trans-dichloroethylene, 
are available in these end uses. One commenter also suggested that a 
user of an nPB-based aerosol will assume that they are being provided 
with a product that offers similar margins of safety as the product 
being replaced (i.e., HCFC-141b) and therefore can be used under the 
same conditions (Werner, 2003).
    The likelihood that nPB aerosol solvents would be used in poorly 
ventilated spaces is of particular concern given the likelihood of 
elevated exposure levels. The exposure data from aerosol solvent use 
are extremely limited. These data are from simulations of a number of 
situations where nPB might be used, such as benchtop cleaning of 
electronics and cleaning automotive brakes, rather than data from 
facilities currently using nPB in manufacturing or maintenance 
processes. Thus, the available exposure data may not be representative 
of ventilation levels normally used with nPB-based aerosols and may not 
adequately represent exposure levels during in-place cleaning, 
industry's most common application for nPB-based aerosols. The 
distribution of exposure levels in the seven samples ranging from 5.5 
to 32 ppm corresponded to the range of ventilation rates reported--0, 
300, 640, and 1900 cfm--with the highest ventilation rate resulting in 
the lowest exposure levels and the lower ventilation levels resulting 
in the values above 30 ppm. The ventilation rate most consistent with 
use in a confined space for in-place cleaning, 0 cfm, resulted in half 
the exposures (one of two) exceeding 30 ppm. The highest ventilation 
rate, 1900 cfm, occurred at a vented booth, which would not be feasible 
to install for in-place cleaning applications--the majority of 
applications for nPB-based aerosols. The middle ventilation rates of 
300 and 640 cfm occurred during use of a fan for an entire room 
(regional ventilation), as might be expected for benchtop cleaning 
(Confidential submission, 1998), but not for in-place cleaning in 
confined spaces. In modeling nPB exposure from aerosol solvent use at a 
low ventilation rate of

[[Page 30189]]

450 cfm, a level that might be expected during benchtop cleaning, 8-
hour average concentrations of 16.5 to 33 ppm are predicted, depending 
on the amount of nPB used (ICF, 2006a). Exposure levels for confined 
spaces with even lower ventilation rates, as we would expect for in-
place cleaning, would be even higher, likely exceeding the high end of 
the range that EPA is considering. Short-term exposures of 370 and 
1,100 ppm taken from workers' collars in a room with regional 
ventilation at 640 cfm, when averaged over an 8-hour period, resulted 
in exposure levels of 12 and 34 ppm. These exposures occurred as a 
result of using nPB over a period up to 15 minutes, so it is likely 
that users would have greater exposure than 30 ppm if they used nPB for 
longer than 15 minutes per day, as with multiple uses. The available 
data sets have a small sample size, may not be representative of in-
place cleaning in confined spaces, and do not provide EPA with 
convincing data that nPB is likely be used safely, at exposure levels 
at or below the highest level in the range we are considering for 
evaluation of acceptability.
    EPA is concerned that many, and perhaps most, uses of nPB aerosol 
solvents result in a high probability of exposures at or above even the 
upper end of the range of exposures that the Agency is considering to 
be potentially acceptable. EPA is aware of no data on ventilation 
levels demonstrating that most users of aerosol solvents, or of nPB in 
particular, would use aerosols in locations with sufficiently high 
ventilation levels to protect human health (e.g., 1900 cfm or greater). 
We request data on worker exposure levels, typical ventilation rates, 
and patterns for usage of nPB-based aerosols, considering both benchtop 
and in-place use.
    EPA has found numerous other aerosol solvents acceptable. These 
aerosol solvents can be used safely in a manner consistent with their 
respective acceptable exposure limits. This is highlighted in a study 
comparing concentrations of eight different chemicals that are 
acceptable under the SNAP program in aerosol formulations: HFE-7100, 
HFE-7200, trans-1,2-dichloroethylene, HCFC-225ca and -225cb, acetone, 
pentane, and HFC-134a. In this study, with ventilation of only 48 cfm, 
8-hr TWA exposure from the different chemicals varied from 35.5 ppm to 
194.0 ppm, and all chemicals met their respective recommended exposure 
levels (ICF, 2006a). As discussed above in section V.A, when these 
concentrations are adjusted for the chemicals' respective molecular 
weights, they would correspond to nPB concentrations of 29.5 to 394.4 
ppm, which is at or above even the highest level the Agency would 
consider acceptable. The ventilation level in this study is closer to 
what we would expect in a confined space where fans or vents cannot be 
installed, as for in-place cleaning. Based on these considerations, the 
Agency believes that nPB used as an aerosol solvent would impose 
significantly more risk to human health than other alternatives 
available for this end use.

B. Adhesives

    EPA proposes to find nPB unacceptable in the adhesive end use. As 
for aerosol solvents, we found that some alternative adhesive 
formulations could reduce particular environmental risks more than nPB, 
such as generation of ground level ``smog'' or ozone depletion 
potential. However, we find the greatest concern in this end use is 
with nPB's human health effects. We propose to find nPB unacceptable in 
adhesives because it poses significantly greater risk to human health 
as compared to other available alternatives in this end use.
    In the June 2003 NPRM, we initially proposed to find nPB acceptable 
in adhesives based on the SNAP program principle that ``EPA does not 
intend to restrict a substitute if it poses only marginally greater 
risk than another substitute * * *. The Agency also does not want to 
intercede in the market's choice of available substitutes, unless a 
substitute has been proposed or is being used that is clearly more 
harmful to human health and the environment than other alternatives.'' 
(68 FR 33294, citing the original March 18, 1994 SNAP rule at 59 FR 
13046). At the time of the proposal, we considered data from NIOSH 
monitoring and health hazard evaluations for three facilities using 
nPB-based adhesives. At two of the three facilities, NIOSH worked 
together with the companies to install state-of-the-art ventilation 
equipment. Looking at exposure data from all workers after ventilation 
improvements, we believed it would be possible for facilities to meet 
the proposed AEL of 25 ppm (68 FR 33294).
     One public commenter suggested that EPA should reconsider 
whether industrial exposures consistently occur and/or can be 
controlled to a level at or below 25 ppm (Werner, 2003). We reevaluated 
the exposure data for the two plants that had improved their 
ventilation, focusing on exposure to the workers that receive the 
highest exposures because they directly spray the nPB-based adhesive. 
We found that, even in the best case, a substantial number of workers 
spraying nPB-based adhesives would be exposed above the highest level 
in the range we are considering.
     NIOSH investigators initially reported that mean exposures 
to nPB ranged from 60 to 381 ppm (8-hour time weighted averages) at 
three different foam-fabrication facilities using nPB-based adhesives 
(NIOSH, 2000a, 2000b, 2001, 2002a, 2002b, 2003a). In one facility, 
average (mean) nPB exposures were reduced from 169 ppm to 19 ppm, 
following installation of ventilation equipment (NIOSH, 2000b). 
Although use of spray booths at this facility reduced the average 
exposure level to 19.4 ppm for all workers, the majority of the 
sprayers directly using nPB-based adhesives still would be exposed at 
unacceptably high levels. Out of fourteen sprayers at the Custom 
Products facility:
     Six, or 43% of sprayers, would be exposed to more than 30 
ppm.
     Nine, or 64% of sprayers, would be exposed to more than 25 
ppm.
     Ten, or 71% of sprayers, would be exposed to more than 20 
ppm.
     Eleven, or 79% of sprayers, would be exposed to more than 
15 ppm.
     Thirteen, or 93% of sprayers, would be exposed to more 
than 10 ppm.
    At another facility using nPB-based adhesives, the average exposure 
was reduced from 58 pm to 19 ppm after the company installed 
ventilation recommended by NIOSH (NIOSH, 2001). Data on exposure for 
sprayers found fewer individuals receiving high exposures than at the 
facility monitored in NIOSH (2000b), but 65% (22 of 34) of exposure 
samples for sprayers were higher than 15 ppm, 33% (11 of 34) were 
higher than 20 ppm and 15% (5 of 34) were higher than 25 ppm after 
improving ventilation.
    Overall, 42% of sprayers in these two facilities using nPB-based 
adhesives were exposed to concentrations of nPB greater than 20 ppm (21 
of 48 workers) and 23% (14 of 48 workers) were exposed to more than 25 
ppm, even after installing state-of-the-art ventilation with assistance 
from NIOSH. Sprayers had significantly higher individual exposures than 
workers who did not work directly with the nPB-based adhesive.
    In response to public comment and additional information available 
to EPA since the June 2003 NPRM, we now propose that use of nPB-based 
adhesives poses significantly higher risks to human health than other 
available adhesives. Since the June 2003 NPRM, there have been a number 
of reports of

[[Page 30190]]

workers working with nPB-based adhesives that have suffered adverse, 
persistent neurological effects that resulted in hospitalization (Beck 
and Caravati, 2003, and Majersik et al., 2004, 2005; Calhoun County, 
2005; Miller, 2005; Raymond and Ford, 2005). Based on data from actual 
facilities using adhesives, it is estimated that a facility using nPB 
with average adhesive application rates and average ventilation rates 
would have exposure levels of approximately 60 ppm on an 8-hr time-
weighted average (ICF, 2006a). Modeling of exposures at high adhesive 
application rates and average or lower ventilation rates resulted in 
exposures of approximately 250 to 2530 ppm (ICF, 2006a). We believe 
these modeling results show that most adhesive users would exceed 
acceptable exposure levels by significant margins and that it is 
unlikely that adhesive users would be able to use nPB safely.
    Considering the exposure data for nPB-based adhesives, we believe 
it is unlikely that, even with improved ventilation, adhesive users 
could reduce exposures to acceptable levels on a consistent basis. In 
the best case seen, a facility with low to average initial exposure 
levels was able to reduce exposures to the middle of the range EPA is 
considering after extensive assistance from NIOSH in installing state-
of-the-art ventilation. We expect that many facilities will begin with 
higher exposure levels and will not have the same level of assistance 
to improve ventilation, thus making it unlikely that they would achieve 
acceptable exposures. Given the information above, we are concerned 
that nPB-based adhesives cannot be reliably used in a manner that 
protects human health. We request comment and further data on whether 
it is feasible to use nPB-based adhesives with worker exposure levels 
consistently at or below any of the values in the range of exposure 
levels that EPA is considering potentially acceptable (i.e., 17 to 30 
ppm).
    The available information indicates that all acceptable carrier 
solvents in adhesives other than nPB have projected or actual exposure 
less than the appropriate workplace exposure limit EPA used in finding 
those substitutes acceptable. Examples of other carrier solvents 
currently used in adhesives and acceptable under the SNAP Program 
include hydrocarbon solvents, acetone, methylene chloride, and water. 
EPA finds that there are other available alternatives that pose 
significantly less risk to human health and the environment compared to 
nPB in the adhesives end use.
    During the public comment period on the June 2003 NPRM, one 
commenter representing the adhesives industry stated that there are 
some small but critical applications that require nonflammability and 
high solvency (Collatz, 2003). The commenter did not specify what those 
applications are, and whether there was information showing that other 
types of adhesives, such as those using water, flammable solvents, or 
methylene chloride, are technically infeasible in these applications. 
We request comment and data on whether there are any unique 
applications in the adhesives end use for which there are no 
technically feasible alternatives other than nPB and thus, for which 
nPB should be allowed. If so, and if determined that nPB should be 
unacceptable except where no other substitutes are feasible, we would 
consider finding nPB acceptable subject to narrowed use limits, with 
requirements for each end user to perform a demonstration that there 
are no other technically feasible alternatives for their particular 
site, to install local exhaust ventilation equipment designed to reduce 
exposures to acceptable levels and to perform worker exposure 
monitoring. Alternatively, if there was sufficient information provided 
during the public comment period showing that there are applications in 
which nPB can be safely used, we would consider finding nPB acceptable 
in adhesives, subject to use conditions requiring installation of local 
exhaust ventilation and worker exposure monitoring. This would allow 
for use of nPB in any applications where it may be used safely if any 
such applications exist.

C. Coatings

    We are proposing to find nPB acceptable, subject to use conditions, 
for facilities that, as of May 30, 2007, have provided EPA information 
demonstrating their ability to maintain workplace exposure levels below 
even the minimum level of the range of exposures that EPA is 
considering to be potentially acceptable (i.e., 17 to 30 ppm). The SNAP 
submission with information on coatings was made for a single facility 
and EPA is unaware of anyone else interested in using nPB in this end 
use. Therefore, there are currently no analyses indicating whether nPB 
would pose significantly greater risks in any coating applications 
other than this facility. Workplace exposure levels to nPB from 
ammunition sealant at Lake City Army Ammunition Plant ranged from less 
than 1 ppm up to 21 ppm on an eight-hour time-weighted average. Thirty-
four of 35 samples had concentrations below 10 ppm, and the mean 
concentration for the plant was less than 4 ppm (Lake City Army 
Ammunition Plant, 2004). The vast majority of measurements show worker 
exposure well below the lowest level in the range of exposures that EPA 
is considering. Thus, we believe that nPB can be used as safely as 
other acceptable solvents used at their acceptable exposure limits 
under the conditions at this facility.
    Other acceptable substitutes for ozone-depleting substances in 
coatings, in general, include oxygenated solvents, hydrocarbon 
solvents, terpenes, hydrofluoroethers 7100 and 7200, benzotrifluorides 
(include parachlorobenzotrifluoride), monochlorotoluenes, trans-1,2-
dichloroethylene, chlorinated solvents, water-based formulations, and 
high-solids formulations. In the particular application for ammunition 
coatings, the submitter evaluated a large number of alternatives and 
found that n-propyl bromide was the only one of 29 solvents tested that 
could meet performance specifications at this facility (Harper, 2005). 
Thus, it is not clear that there are other substitutes available for 
this specific application, and exposure data show that in this specific 
application, nPB can be used in a way that does not pose significantly 
greater risks to human health compared to other acceptable substitutes 
in the coatings end use.

VII. What other regulatory options did EPA consider?

    EPA considered several different options, but we prefer the 
approach proposed in this rule. We also take comment on the options 
discussed below.

A. Alternate Option for Comment: Acceptable With Use Conditions 
Requiring Exposure Limit and Monitoring

    We also take comment on a proposed alternate approach in which nPB 
would be acceptable subject to use conditions in all the end uses 
addressed in this action. Under this alternate approach, users would 
meet an exposure limit, monitor exposure of workers using nPB, and keep 
records to demonstrate compliance with these requirements. For purposes 
of this alternative proposal, we selected 20 ppm to use as an exposure 
limit above which use would be unacceptable, and 10 ppm as an action 
level that allows reduced exposure monitoring, for the reasons 
discussed below in section VII.A.1, ``Use Conditions and Their 
Rationale.'' However, we are soliciting comment on whether a different 
exposure level within the 17 to 30 ppm range should

[[Page 30191]]

be selected. The following requirements would apply at each facility 
where nPB is used:
Exposure Limit
    The owner or operator would be required to ensure that workers 
using nPB are exposed to no more than 20 ppm on an 8-hour time-weighted 
average. The exposure limit could be met through engineering controls 
(e.g., ventilation equipment), work practices, or reduced use of nPB.
Initial Worker Exposure Monitoring
    For each facility where nPB is used, the owner or operator of the 
facility would be required to ensure that personal breathing zone air 
samples of each nPB user's exposure would be collected on an eight-
hour, time-weighted average initially within 90 days after a final rule 
becomes effective. Monitoring measurements may be taken with an organic 
chemical monitoring badge on the collar or a tube filled with charcoal 
on the collar.
Periodic Exposure Monitoring
    (1) The owner or operator of the facility would be required to 
ensure that personal breathing zone air samples of user exposure are 
collected periodically on an eight-hour, time-weighted average 
depending on the results of the most recent set of exposure data. A 
monitoring program could be instituted by the company or by the nPB 
supplier for that facility. Periodic sampling requirements would be 
based on the most recent monitoring results, as follows:

  Table 10.--Alternative Approach Exposure Levels and Periodic Exposure
                               Monitoring
------------------------------------------------------------------------
If exposure measurements for nPB are at
              this level:                  Then the owner or operator:
------------------------------------------------------------------------
all measurements at or below 10 ppm....  is not required to perform
                                          periodic exposure monitoring.
all measurements at or below 20 ppm,     must take personal breathing
 with some measurements above 10 ppm.     zone samples again at least
                                          once in the next six months.
at least one measurement above 20 ppm..  must stop using nPB in the
                                          application exceeding the
                                          exposure limit until exposure
                                          data show that 20 ppm can be
                                          consistently met in the vast
                                          majority of cases.
unknown, in cases of new workplace       must take personal breathing
 conditions increasing exposure or new    zone samples as a test before
 applications of nPB.                     using nPB in new industrial
                                          applications or conditions, or
                                          within 7 days of an emergency
                                          caused by a leak, rupture or
                                          breakdown, and use this value
                                          to determine the next time
                                          monitoring is required.
------------------------------------------------------------------------

    (2) For periodic monitoring, the owner or operator would be allowed 
either to monitor each nPB user's exposure, or to monitor exposure of a 
representative nPB user in each job classification in a work area 
during every work shift, where the monitored nPB user is expected to 
have the highest exposure.
    (3) The owner or operator would be allowed to discontinue the 
periodic 8-hour TWA monitoring for nPB users at the facility where at 
least two consecutive sets of measurements taken at least seven days 
apart are below 10 ppm.
Monitoring for New Conditions or Applications
    Whenever there is a change in workplace conditions that may 
increase exposure or whenever a new application of nPB is introduced, 
the owner or operator would be required to take personal breathing zone 
samples accounting for all nPB users as a test before using nPB in 
manufacturing or repair. These could be either samples for each nPB 
user or samples representing each job classification in a work area 
during a work shift, so long as the samples are based on the user with 
the likely highest exposure. Examples of changes in workplace 
conditions that may increase exposure include changes in production, 
process control equipment, or work practices, or a leak, rupture, or 
other breakdown.\20\ Examples of introduction of a new application of 
nPB include aerosol contact cleaning in a location with regional 
ventilation or natural ventilation, where previous measurements were 
carried out on workers in a location with local ventilation. If the 
change occurs because of an unpredictable emergency, then the owner or 
operator would need to ensure exposure monitoring takes place within 7 
days of the change.
---------------------------------------------------------------------------

    \20\ See 29 CFR 1910.1052(d)(4)(i).
---------------------------------------------------------------------------

Sampling Methods and Accuracy
    Exposure samples would be required to be analyzed either by NIOSH 
method 1003 for halogenated hydrocarbons or method 1025 for 1-
bromopropane and 2-bromopropane or by another method that is accurate 
to 25% at the 95 percent confidence level.
Recordkeeping Requirements
    The owner or operator of the facility would be required to keep 
records of the monitored exposure data at the facility for at least 
three years from the date the measurements were taken for purposes of 
this rule. These records would be required to be made available in the 
event of a facility inspection or a request for the data by EPA. Note 
that the EPA's recordkeeping requirement does not affect OSHA's 
standard on access to employee exposure and medical records, which 
requires retaining any exposure records for at least 30 years (29 CFR 
1910.1020(d)(ii)).
    The regulatory listings by end-use under this alternate approach 
that the Agency requests comment on would be as follows:

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[[Page 30193]]


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[[Page 30194]]

1. Use Conditions and Their Rationale
    The major provisions of the use conditions and the related issues 
that EPA considered in developing the alternate approach that we are 
taking comment on are as follows:
    Exposure limit. A requirement to meet a workplace exposure limit 
would be an interim measure to ensure that nPB will be used safely 
until OSHA issues a final permissible exposure limit (PEL) under the 
Occupational Safety and Health Act. In the event that OSHA issues a 
final PEL, it would supersede EPA's exposure limit. EPA is specifically 
deferring to OSHA, and has no intention to assume responsibility to 
displace OSHA's authority under Public Law 91-596. EPA's exposure limit 
would not pre-empt the authority of OSHA to take regulatory or 
enforcement action with respect to exposure to this substance. This is 
made clear by the Clean Air Act under which EPA would promulgate this 
regulation (Subchapter VI--Stratospheric Ozone Protection), which 
provides at 42 U.S.C. 7610 in pertinent part: ``* * * this chapter 
[Chapter 85--Air Pollution Prevention] shall not be construed as 
superseding or limiting the authorities, under any other provision of 
law, of the Administrator or any other Federal officer, department, or 
agency.'' By issuing an exposure limit for nPB, EPA's intention would 
be to fill existing regulatory gaps during the interim period of 
substitution away from ozone-depleting compounds and provide the needed 
margin of protection for human health and the environment until OSHA 
develops other regulatory controls or standards under appropriate 
authorities.
    As discussed above in section IV.E.1, EPA is considering exposures 
within the range of 17 to 30 ppm as potentially acceptable in order to 
determine whether nPB may be used safely in each end use. For purposes 
of having a clear compliance target under this alternative approach for 
public comment, we are using 20 ppm as the exposure limit above which 
use would be unacceptable. We chose this value because we expect it to 
be protective against the reproductive and developmental effects 
identified previously (live litter size, sperm motility, estrous 
cycles). Worker exposure monitoring. The worker exposure monitoring 
requirements under the use conditions in the alternate approach were 
modeled after OSHA's requirements for monitoring for methylene 
chloride. 29 CFR 1910.1052(d). We expect that the regulated community 
would be familiar with this approach and there might be fewer changes 
for regulated businesses if OSHA later were to establish a workplace 
standard for nPB. Because the exposure limit would be an 8-hr TWA value 
that is derived from studies that measured exposure via inhalation, the 
proposed use conditions require the owner or operator to monitor 8-hr 
TWA values that measure workers' exposure in the breathing zone (e.g., 
samples from a worker's collar). We are not proposing to monitor short-
term exposures because acute, short-term exposures of nPB are not of 
significant health concern, so long as long-term exposures are below 
the 8-hour TWA limit or potentially acceptable exposure levels (ERG, 
2004).
    Option for monitoring representative set of workers. Personal 
breath zone samples could be taken either from each worker using nPB or 
from a representative \21\ set of exposed workers expected to have the 
highest exposure. Allowing exposure monitoring from representative 
workers using nPB, rather than requiring separate monitoring for each 
individual using nPB, would reduce overall compliance burden, while 
still detecting any exposure levels in excess of the exposure limit and 
avoiding underestimates of exposure.
---------------------------------------------------------------------------

    \21\ In its methylene chloride standard, OSHA defined 
representative sampling as follows: ``The employer has taken one or 
more personal breathing zone air samples for at least one employee 
in each job classification in a work area during every work shift, 
and the employee sampled is expected to have the highest * * * 
exposure.'' (29 CFR 1910.1052(d)(1)(ii)(A)).
---------------------------------------------------------------------------

    Initial monitoring. Users already using nPB would need to undergo 
exposure monitoring no later than 90 days after the date the final rule 
becomes effective. A user that has never used nPB before would need to 
perform initial monitoring before beginning to use nPB in the 
facility's industrial applications.
    Periodic monitoring. Monitoring would have to be performed 
periodically on a schedule based on the results of the most recent set 
of exposure monitoring data. Monitoring from workers' personal 
breathing zone would be required during the next six months if an 
initial measurement finds exposure levels between the action level \22\ 
and the 8-hour TWA exposure limit. No periodic monitoring would be 
required if initial measurements are below the action level. The action 
level would be the value that is half the exposure limit, in this case 
10 ppm. OSHA standards also set an action level of half the PEL.
---------------------------------------------------------------------------

    \22\ The action level is the exposure level that is half the 8-
hour TWA exposure limit. In this case, the action level would be10 
ppm.
---------------------------------------------------------------------------

    Under the alternate approach, monitoring would no longer be 
required where the most recent exposure monitoring data found all 
worker exposures at or below 10 ppm. OSHA rules also reduce monitoring 
requirements for exposures below the action level because if measured 
values are that low, it is unlikely that any measurement will exceed 
the PEL unless a major change to the process occurs.
    Monitoring for changes in workplace conditions or nPB use. New 
monitoring would be required if an event occurs that would make the 
most recent set of monitoring data no longer representative. EPA would 
expect that the owner or operator would plan new applications of nPB or 
changes to control equipment or work practices and would perform a test 
for worker exposure levels before using nPB on a regular basis in that 
application. In the case of an emergency, such as a breakdown of 
ventilation equipment or a leak, we would expect exposure monitoring to 
be performed as soon as possible, and no later than 7 days after the 
change in workplace conditions. This period is intended to give an 
owner or operator time to locate and purchase exposure monitoring 
equipment in an emergency where the equipment may not already be 
available at the facility.
    Monitoring method and accuracy. We take comment on the use of NIOSH 
methods 1003 and 1025 (NIOSH, 2003b and c) for analyzing nPB exposure 
under the proposed alternate approach. Several of the studies that 
supplied EPA with exposure data used this method and they are 
standardized methods prepared by NIOSH, a recognized authority on 
industrial hygiene. In addition, we would allow other methods that are 
accurate to  25% at the 95 percent confidence level. Based 
on the accuracy of available methods, most OSHA standards require 
exposure monitoring accurate to 25% at the 95 percent confidence level, 
as in the methylene chloride standard (29 CFR 1910.1052(d)(1)(iii)(A)) 
and other OSHA standards.
    Recordkeeping requirements. We would require that users keep 
records of the worker exposure data for three years from the date the 
measurement is taken.\23\ This would provide information allowing EPA 
to determine if facilities are complying with the exposure limit and if 
workers exposed to nPB are sufficiently protected.
---------------------------------------------------------------------------

    \23\ OSHA's standard on access to employee exposure and medical 
records requires retaining exposure records for at least 30 years 
(29 CFR 1910.1020(d)(ii)), and these requirements would not be 
affected by this regulation.
---------------------------------------------------------------------------

    Responsibility for meeting requirements. Under the alternate 
approach, the owner or operator of a

[[Page 30195]]

facility using nPB would be responsible for meeting the rule's use 
conditions.
2. Advantages and Disadvantages of the Alternate Approach
    Setting use conditions that require users to meet an exposure limit 
and to monitor and keep records to demonstrate achieving the limit 
would protect the health of nPB users while giving industry more 
flexibility and more options for ODS substitutes, compared to finding 
nPB unacceptable. This could be especially useful for users of HCFC-
141b as an aerosol solvent that are seeking an effective ODS 
substitute. If there were any situations in which other available 
alternatives did not provide as good performance, nPB would still be 
available as an option, provided the use conditions could be met. The 
monitoring requirements would encourage good industrial hygiene and 
safe use of nPB.
    Considering the list of use conditions above, we believe that 
setting use conditions requiring an exposure limit, worker exposure 
monitoring, and recordkeeping would be complex and potentially 
confusing. Requiring users to meet the exposure limit, although 
providing greater potential flexibility, also would provide less 
certainty about how to comply. A user could spend considerable time and 
expense trying to meet the exposure limit, only to find that it is not 
achievable.
    Given the limited circumstances under which we expect aerosol and 
adhesive users could meet an acceptable exposure limit and given the 
availability of other, less toxic alternatives in both of these end 
uses, EPA's preferred option is to find nPB unacceptable in aerosols 
and adhesives. Further, considering that without regulatory 
requirements, the users of nPB at the Lake City Army Ammunition Plant 
have been operating with the vast majority of exposure levels below 17 
ppm, the low end of the range of exposures that EPA is considering to 
be potentially acceptable (Lake City Army Ammunition Plant, 2004), it 
appears unnecessary to require an exposure limit in that application.

B. Regulatory Options Where nPB Would Be Acceptable With Use Conditions 
Requiring Specific Equipment

    We considered use conditions for the adhesive and aerosol solvent 
end uses that would reduce the human health risks of using nPB by 
reducing exposure levels with requirements for installation and use of 
ventilation equipment. We also offer for comment use conditions that 
would require aerosol dispensing equipment that would reduce exposure 
levels and that would allow use of aerosol blends with reduced amounts 
of nPB to maintain acceptable exposure levels.
1. Aerosols
    For the aerosol solvent end use, EPA considered proposing a 
requirement for installation of ventilation equipment. Such a use 
condition would need to specify and define which kinds of ventilation 
equipment would be necessary. For example, because one study on 
exposure levels found that exposure levels reliably fell in or below 
the range that EPA is considering (i.e., 17 to 30 ppm) only where both 
local exhaust ventilation and regional ventilation equipment were used, 
a possible requirement would be for installation of both local exhaust 
ventilation and regional ventilation. We would define local exhaust 
ventilation as ventilation that removes vapors from a specific work 
location using ducts and fans. We would define regional ventilation as 
ventilation that moves air around in a large working area, such as one 
or more fans used for an entire room. A problem with requiring the type 
of ventilation equipment that all facilities must use is that it still 
might not provide enough ventilation in some situations and in other 
situations may be unnecessary to meet an exposure limit.
    Another approach for aerosols we considered was to require a 
specific level of ventilation. Possible criteria for the level of 
ventilation would be the air flow rate, in cubic feet per minute (cfm) 
or cubic meters per second, or the face velocity at the location where 
a user would work, in feet per minute (fpm) or meters per second face 
velocity. Based on both modeling and exposure data from one study (ICF, 
2006a; Linnel, 2003), an appropriate air flow rate for nPB-based 
aerosols would be greater than 1900 cfm and an appropriate face 
velocity would be 170 fpm. Alternatively, we considered requiring that 
facilities meet the guidelines for face velocity in spray booths from 
the ACGIH Ventilation Manual, in the range of 100 to 150 fpm, depending 
on the specific type of booth (ACGIH, 2002).
    These options would appear to provide greater flexibility for 
industry compared to finding nPB unacceptable in aerosol solvents. 
However, our understanding is that in most aerosol applications, it 
might not be feasible to install adequate ventilation, and thus, to 
reduce human health risks. In the case of benchtop cleaning or 
degreasing, such as during rework of individual parts that are not yet 
sufficiently clean, it is possible to transport the part to a hood or 
spray booth to provide sufficient ventilation. However, for 
applications that require in-place cleaning such as cleaning energized 
electrical contacts and switches, maintenance in underground mines, or 
cleaning hot elevator motors, it is not feasible to install ventilation 
equipment in place or to remove the parts for cleaning in ventilation 
equipment (CSMA, 1998; Linnell, 2003). Information available to EPA 
shows that benchtop cleaning is perhaps 25% or less of the market for 
the ODS being replaced in aerosols (US EPA, 2004) and that electrical 
contact cleaning makes up the vast majority of the market for nPB-based 
aerosols (Williams, 2005); thus, we expect that necessary ventilation 
cannot be installed in most aerosol applications for nPB. It would be 
difficult to explain and potentially confusing for users that an 
aerosol product may be used for cleaning in one location in a facility, 
but not in another, particularly when the ODS being substituted for 
could be used in all locations at safe exposure levels. Further, it 
would be difficult for EPA to enforce use conditions on ventilation 
equipment, because aerosols are portable and can easily be used outside 
of the ventilation equipment. Other acceptable substitutes, such as 
blends of HFEs or HFCs and trans-dichloroethylene, are available in 
these end uses.
    Another option that the Agency considered is finding nPB acceptable 
as an aerosol solvent, subject to the use condition that the aerosol 
product must be dispensed from a device or a system that is capable of 
maintaining acceptable exposure levels. The Agency is aware of at least 
two remote dispensing systems that could potentially mitigate exposures 
when used with low-pressure aerosols (Micro Care's Trigger 
GripTM and Miller Stephenson's Cobra[supreg] Solvent Spray 
Cleaning Brush). Vendor data indicates that each aerosol can may last 
twice as long when using a remote dispensing system, compared to 
standard aerosol usage, indicating the ability to halve average 
exposure levels and reduce total solvent use (Micro Care, 2006). 
However, these types of systems would only be practical for benchtop 
cleaning, and not electrical contact cleaning, which comprises the 
majority of nPB aerosol use. The Agency requests comment on the 
viability and enforceability of a use condition requiring aerosol 
dispensing systems or other mitigation devices that could provide 
sufficient performance while

[[Page 30196]]

ensuring acceptable workplace exposure levels of nPB.
    Finally, the Agency considered another option by which the use of 
nPB would be acceptable in aerosol solvent uses, subject to the 
condition that users may only use blends of no more than fifty percent 
nPB and the remainder being propellants and other solvents, with 
manufacturer's recommended exposure guidelines for compounds other than 
nPB being no lower than 100 ppm. Based on exposure modeling performed 
on simulations of several commercial blends of nPB and another compound 
with a higher exposure limit (HFC-365mfc), it appears that users should 
be able to maintain exposures reliably below the range that EPA is 
considering for acceptability (i.e., 17 to 30 ppm) when using a blend 
containing no more than fifty percent nPB by weight at the ventilation 
levels modeled (ICF, 2006a). We note that the modeling does not 
consider the possibility that a user might need to use more of a blend 
with less nPB, since nPB is more aggressive than many other solvents 
used in aerosols. It also does not address exposure levels in confined 
spaces as might occur during in-place cleaning with aerosols. We 
request comment and relevant, empirical data on the 8-hour TWA 
exposures that can be reliably attained when using blends containing 
50% or less of nPB by weight. In order to make this option enforceable, 
EPA would require users to keep records of nPB-containing aerosol 
blends they purchase, including the MSDS or other documentation of the 
proportion of nPB in the blend they use. We request comment on whether 
this is a feasible, enforceable option and whether it would provide 
useful flexibility to industry while ensuring adequate health 
protection.
2. Adhesives
    EPA also considered use conditions for ventilation equipment or for 
specific ventilation levels for use of nPB-based adhesives. However, to 
date, we have found no study that demonstrates a ventilation option 
that could consistently achieve even the highest level within the range 
that EPA is considering for acceptability when using spray adhesives. 
Even with state-of-the-art ventilation equipment installed with the 
expert assistance of NIOSH, adhesives users were not able to lower 
exposure limits sufficient to protect the vast majority of their 
workers. Modeling of different levels of adhesive usage and 
ventilation, based on conditions at different facilities indicates that 
air flow rates would need to be more than 100,000 cfm. Even this high 
air flow rate might not be sufficient, since an air flow rate of 28,500 
cfm resulted in exposure levels of 3.5 to 35 times an acceptable 
exposure level, depending on the amount of adhesive used (ICF, 2006a, 
Att. D). Less toxic substitutes such as water-based adhesives and 
acetone-based adhesives are available in this end use.

VIII. What are the anticipated costs of this regulation to the 
regulated community?

    As part of our rulemaking process, EPA estimated potential economic 
impacts of this proposed regulation. In our analysis, we assumed that 
capital costs are annualized over 15 years or less using a discount 
rate for determining net present value of 7.0%. Because the use 
condition for coatings still permits nPB's use in the only known 
coatings application using nPB, we find no additional cost to the user 
community from this regulatory provision. We found that if this 
proposed rule were to become final, the cost to the user community of 
the unacceptability determinations, which are regulatory prohibitions 
on the use of nPB in adhesives and aerosols, would be in the range of 
$2.3 to $6.7 million per year for adhesive users and $36.3 to 39.7 
million per year for aerosol users.
    EPA also estimated the cost to the user community of the use 
conditions in the proposed alternate approach for aerosols, adhesives, 
and coatings. The requirements for users to meet an acceptable exposure 
limit and to perform exposure monitoring would be in the range of $42.3 
to 67.5 million per year. The upper end of the range of estimated 
impacts assumes laboratory grade ventilation for aerosols, which we 
expect to be significantly more expensive than standard industrial fume 
hoods or spray booths (approximately $10,000 compared to $1,000 for 
each hood). For coatings, use of nPB is limited to a single facility 
that already performs workplace exposure monitoring, and thus, no new 
costs would be incurred. For aerosols and adhesives, we assumed the 
installation of fume hoods or spray booths, the use of personal 
protective equipment, and monitoring for 1.9 to 2.0 times per year on 
average. Using these assumptions, we calculated the cost of the use 
conditions in the proposed alternate approach at $18.0 to 24.0 million 
for adhesive users, and $24.3 to 43.5 million for aerosol users. The 
estimated cost of the use conditions does not consider that some users 
could choose to switch to other alternatives at a lower cost.
    Estimated costs of the proposed regulation and proposed alternate 
approach are summarized in Table 13. For more detailed information, see 
section XIII.C. below and EPA's analysis in the docket (US EPA, 2006).

                  Table 13.--Estimated Costs of Regulatory Options EPA is Providing for Comment
----------------------------------------------------------------------------------------------------------------
                                                                                                 Annual cost of
       Sector or end use          Requirements under    Annual cost of     Requirements under       alternate
                                    proposed rule        proposed rule    alternate  approach       approach
----------------------------------------------------------------------------------------------------------------
Aerosol Solvents..............  Cease use of nPB and   $36.3 to 39.7     Achieve 20 ppm;        $24.3 to 43.5
                                 switch to a            million.          exposure monitoring    million.
                                 different ODS                            one or two times per
                                 substitute.                              year; Recordkeeping.
Coatings......................  Decision applies to    None............  Achieve 20 ppm;        None.
                                 use nPB in coatings                      exposure monitoring,
                                 at facilities that,                      one or two times per
                                 as of May 30, 2007,                      year; recordkeeping.
                                 have provided EPA
                                 information
                                 demonstrating their
                                 ability to maintain
                                 acceptable workplace
                                 exposures.
Adhesives.....................  Cease use of nPB and   $2.3 to 6.7       Achieve 20 ppm;        $18.0 to 24.0
                                 switch to a            million.          exposure monitoring,   million.
                                 different ODS                            one or two times per
                                 substitute.                              year; recordkeeping.
                               ---------------------------------------------------------------------------------
    Total.....................  .....................  $38.6 to 46.4     .....................  $42.3 to 67.5
                                                        million.                                 million.
----------------------------------------------------------------------------------------------------------------


[[Page 30197]]

IX. How do the decisions for EPA's June 2003 proposal compare to those 
for this proposal?

    Table 14 compares the acceptability determination and evidence 
cited in the June 2003 proposal and this proposal.

           Table 14.--n-Propyl Bromide Acceptability Decision
------------------------------------------------------------------------
                                                      Current proposed
      Proposed decision        2003 proposed rule      rule--preferred
                                                          proposal
------------------------------------------------------------------------
Industrial End Use 1: Aerosol Solvents.        to a Use Condition
                               (Limiting use to
                               nPB formulations
                               containing no more
                               than 0.05% by
                               weight isopropyl
                               bromide; AEL of 25
                               ppm \1\ on 8-hr TWA
                               recommended.
Industrial End Use 2: Adhesives.               to a Use Condition
                               (Limiting use to
                               nPB formulations
                               containing no more
                               than 0.05% by
                               weight isopropyl
                               bromide; AEL of 25
                               ppm \1\ on 8-hr TWA
                               recommended.
Industrial End Use 3: Coatings.                                      to Use Conditions
                                                     (Decision limited
                                                     to coatings at
                                                     facilities that, as
                                                     of May 30, 2007,
                                                     have provided EPA
                                                     information
                                                     demonstrating their
                                                     ability to maintain
                                                     acceptable
                                                     workplace
                                                     exposures.\2\
------------------------------------------------------------------------
\1\ Proposed acceptable exposure limit of 25 ppm adjust upward from
  value of 18 ppm based upon nPB's effect on sperm motility from
  evaluation of the WIL 2001 Study ``An Inhalation Two-Generation
  Reproductive Toxicity Study of 1-Bromopropane in Rats.''
(a) ICF, 2001. ''Brief Discussion of the BMD Approach: Overview of its
  Purpose, Methods, Advantages, and Disadvantages.'' Prepared for U.S.
  EPA.
(b) ICF, 2002a. ''Risk Screen for Use of N Propyl Bromide.'' Prepared
  for U.S. EPA, May, 2002.
(c) ICF, 2002b. Comments on the NTP-Center for the Evaluation of Risks
  to Human Reproduction, Final Report on 1-Bromopropane. Cover Letter
  Dated 5/9/02.
Also, evaluation of documents by CERHR (2002a, b), Doull and Rozman
  (2001), Rodricks (2002), Rozman and Doull (2002), SLR International
  (2001), and others.
\2\ For purposes of this proposal, EPA is considering levels within the
  range of 17-30 ppm based on the following information on nPB's health
  effects for purposes of determining acceptability: estrous cycle
  length at 17 to 22 ppm, live litter size at 20 ppm, and sperm motility
  at 18 to 30 ppm from evaluation of the WIL 2001 Study ``An Inhalation
  Two-Generation Reproductive Toxicity Study of 1-Bromopropane in Rats''
  and confirmed by comparison with other studies. Also, considers
  evaluation of documents by Stelljes and Wood (2004); TERA (2004); ICF,
  2006a; ACGIH (2005); Rozman and Doull (2005); Stelljes (2005); and
  others.

X. How can I use nPB as safely as possible?

    Below are actions that will help nPB users minimize exposure 
levels:
All end uses
     All users of nPB should wear appropriate personal 
protective equipment, including chemical goggles, flexible laminate 
protective gloves (e.g., Viton, Silvershield) and chemical-resistant 
clothing. Special care should be taken to avoid contact with the skin 
since nPB, like many halogenated solvents, can be absorbed through the 
skin. Refer to OSHA's standard for the selection and use of Personal 
Protective Equipment, 29 CFR 1910.132.
     Limit worker exposure to solvents to minimize any 
potential adverse health effects. Workers should avoid staying for long 
periods of time in areas near where they have been using the solvent. 
Where possible, shorten the period during each day when a worker is 
exposed. Where respiratory protection is necessary to limit worker 
exposures, respirators must be selected and used in accordance with 
OSHA's Respiratory Protection standard, 29 CFR 1910.134.
     Use less solvent, or use a different solvent, either alone 
or in a mixture with nPB.
     Follow all recommended safety precautions specified in the 
manufacturer's MSDS.
     Workers should receive safety training and education that 
includes potential health effects of exposure to nPB, covering 
information included on the appropriate MSDSs, as required by OSHA's 
Hazard Communication Standard (29 CFR 1910.1200).
     Request a confidential consultation from your State 
government on all aspects of occupational safety and health. You can 
contact the appropriate state agency that participates in OSHA's 
consultation program. These contacts are on OSHA's web site at  http://www.osha.gov/oshdir/consult.html. For further information on OSHA's 
confidential consultancy program, visit OSHA's web page at http://www.osha.gov/html/consultation.html.
     Use the employee exposure monitoring programs and product 
stewardship programs where offered by manufacturers and formulators of 
nPB-based products.
     If the manufacturer or formulator of your nPB-based 
product does not have an exposure monitoring program, we recommend that 
you start your own exposure monitoring program, and/or request a 
confidential consultation from your State government. A medical 
monitoring program should be established for the early detection and 
prevention of acute and chronic effects of exposure to nPB. The 
workers' physician(s) should be given information about the adverse 
health effects of exposure to nPB and the workers' potential for 
exposure.
Spray applications
     For spray applications (e.g., aerosols), consider your 
available options, and if using nPB, use sufficient ventilation to 
reduce exposure to maintain acceptable exposure levels.
     For ventilation, we recommend that you follow the design 
guidelines for ventilation in ACGIH's Industrial Ventilation: A Manual 
of Recommended Practice (ACGIH, 2002). In particular, the guidelines in 
Chapter 10.75 are appropriate for spray booths, and the

[[Page 30198]]

guidelines in Chapter 10.35 are appropriate for laboratory hoods.
     The ACGIH Ventilation Manual recommends a minimum flow 
rate of 150 cubic feet per minute (cfm) for each sq-ft of opening for a 
small booth with at least 4 sq-ft of open face area. This equates to an 
average face velocity of 150 ft/min. For a large booth, the recommended 
face velocity is 100 ft/min for walk-in booths and 100 to 150 ft/min 
for a large spray booth where the operator works outside. In general, 
the opening should be kept as small as possible to accommodate the 
work-pieces, generally 12 inches wider and taller than the largest 
piece of work. If all spraying is not directed towards the back of the 
booth or the booth is too shallow for the size of the pieces being 
sprayed or if disruptive air currents are present at the face of the 
booth, a greater flow of air will be needed.
We note that these steps are useful for reducing exposure to any 
industrial solvent, and not just nPB.

XI. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review

    Under Executive Order (EO) 12866 (58 FR 51735, October 4, 1993), 
this action is a ``significant regulatory action.'' It raises novel 
legal or policy issues arising out of legal mandates, the President's 
priorities, or the principles set forth in the Executive Order. 
Accordingly, EPA submitted this action to the Office of Management and 
Budget (OMB) for review under EO 12866 and any changes made in response 
to OMB recommendations have been documented in the docket for this 
action.
    In addition, EPA prepared an analysis of the potential costs and 
benefits associated with this action. This analysis is contained in the 
document ``Analysis of Economic Impacts of Proposed nPB Rule on 
Aerosols and Adhesives.'' A copy of the analysis is available in the 
docket for this action (Ref. EPA-HQ-OAR-2002-0064) and the analysis is 
briefly summarized here. EPA estimates the total costs of the proposed 
rule to between $38.6 and 46.4 million per year.

B. Paperwork Reduction Act

    The information collection requirements in this proposed rule have 
been submitted for approval to the Office of Management and Budget 
(OMB) under the Paperwork Reduction Act, 44 U.S.C. 3501 et seq. The 
Information Collection Request (ICR) document prepared by EPA has been 
assigned EPA ICR number 2224.01.
    If the provisions of this proposed rule become final (i.e., if the 
proposed regulatory language at the end of this document is finalized), 
there would be no new information collection burden. This proposed rule 
contains no new requirements for reporting or recordkeeping. OMB has 
previously approved the information collection requirements contained 
in the existing regulations in subpart G of 40 CFR part 82 under the 
provisions of the Paperwork Reduction Act, 44 U.S.C. 3501 et seq. and 
has assigned OMB control number 2060-0226 (EPA ICR No. 1596.06). This 
ICR included five types of respondent reporting and record-keeping 
activities pursuant to SNAP regulations: Submission of a SNAP petition, 
filing a SNAP/Toxic Substance Control Act (TSCA) Addendum, notification 
for test marketing activity, record-keeping for substitutes acceptable 
subject to use restrictions, and record-keeping for small volume uses.
    However, if EPA were to finalize the proposed alternate approach 
described in section VII.A of this preamble, users of nPB would have an 
information collection burden from exposure monitoring and 
recordkeeping. Under the proposed alternate approach, users of nPB 
would be required to monitor worker exposure initially and periodically 
(usually every 6 months) and keep records of these exposure data at the 
facility for at least three years from the date the samples were taken. 
This data is necessary to ensure that users of nPB are meeting the 
regulatory use conditions. If the data indicates that the use condition 
is not being met, it could be used by EPA or citizens in an enforcement 
action against the facility. These data would be considered available 
to the public and would not be considered confidential.
    The estimated burden of recordkeeping for the entire regulated 
community under the proposed alternate approach is as much as $7.0 
million and 13,170 hours per year. The estimated recordkeeping burden 
for a typical user is $96 and 0.18 hours per worker per monitoring 
event. We estimate approximately 1.9 monitoring events per year per 
worker, assuming that roughly 90% of exposed workers must be monitored 
every six months and 10% must be monitored once annually. We estimate 
that up to 35,000 workers would be monitored for exposure to nPB. Costs 
under the proposed alternate approach include the annual cost of 
purchasing passive organic exposure monitoring badges, the annual cost 
of services for analyzing the resulting exposure, and the annual cost 
of reviewing and filing the data up to 2 times per year.
    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 are listed in 40 CFR part 9 and 48 CFR chapter 15.
    To comment on the Agency's need for this information, the accuracy 
of the provided burden estimates, and any suggested methods for 
minimizing respondent burden, including through the use of automated 
collection techniques, EPA has established a public docket for this 
rule, which includes this ICR, under Docket ID number EPA-HQ-OAR-2002-
0064. Submit any comments related to the ICR for this proposed rule to 
EPA and OMB. See Addresses section at the beginning of this notice for 
where to submit comments to EPA. Send comments to OMB at the Office of 
Information and Regulatory Affairs, Office of Management and Budget, 
725 17th St., NW., Washington, DC 20503, marked ``Attention: Desk 
Officer for EPA.'' Include the ICR number in any correspondence. Since 
OMB is required to make a decision concerning the ICR between 30 and 60 
days after May 30, 2007, a comment to OMB is best assured of having its 
full effect if OMB receives it by June 29, 2007. The final rule will 
respond to any OMB or public comments on the information collection 
requirements contained in this proposal.

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

[[Page 30199]]

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. The RFA provides default definitions for 
each type of small entity. Small entities are defined as: (1) A small 
business as defined by the Small Business Administration's (SBA) 
regulations at 13 CFR 121.201; (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. 
However, the RFA also authorizes an agency to use alternate definitions 
for each category of small entity, ``which are appropriate to the 
activities of the agency'' after proposing the alternate definition(s) 
in the Federal Register and taking comment. 5 U.S.C. 601(3)-(5). In 
addition, to establish an alternate small business definition, agencies 
must consult with SBA's Office of Advocacy.
    EPA proposed an alternate definition for regulatory flexibility 
analyses under the RFA for rules related to the use of nPB as an 
alternative to ozone-depleting substances (ODS) in metals, precision, 
and electronics cleaning, adhesives, and aerosol solvents in the June 
2003 NPRM (68 FR 33309, June 3, 2003). EPA established this final 
definition under section 601(3) of the RFA when we promulgated the 
final rule on the acceptable use of nPB in metals, precision, and 
electronics cleaning in the Rules and Regulations section of today's 
Federal Register. For purposes of assessing the economic impacts of 
this proposed rule on small entities, EPA defined ``small business'' as 
a small business with less than 500 employees, rather than use the 
individual SBA size standards for the numerous NAICS subsectors and 
codes. We believe that no small governments or small organizations are 
affected by this rule. EPA chose to use the alternate definition to 
simplify the economic analysis. This approach slightly reduced the 
number of small businesses included in our analysis and slightly 
increased the percentage of small businesses for whom the analysis 
indicated the use of nPB in accordance with this proposed rule may have 
an economically significant impact. Furthermore, this size standard was 
set by the Small Business Administration for all NAICS codes for 
businesses using nPB-based adhesives, one of the end uses that would be 
affected by this rule.
    After considering the economic impacts of this proposed rule on 
small entities, I certify that this action will not have a significant 
economic impact on a substantial number of small entities. This rule 
proposes to list nPB as an unacceptable substitute for ODS in aerosols 
and adhesives. EPA has analyzed the economic impacts of switching from 
nPB to other alternative aerosol solvents or adhesives. EPA estimates 
that up to 3,380 small industrial end users currently use nPB in the 
end uses addressed by this proposed rule and thus could be subject to 
the regulatory impacts of this rule. This number includes approximately 
3,100 users of nPB-based aerosol solvents, and 280 users of nPB-based 
adhesives. Considering the regulatory impacts on adhesive and aerosol 
users that must switch to other alternatives, we found that up to 258 
(8%) of small businesses would experience impacts of 1% or greater of 
annual sales and no small businesses would experience impacts of 3% or 
greater of annual sales. Based on the relatively small number and low 
percentage of small businesses that would experience significant 
economic impacts, EPA concludes that this rule would not have a 
significant economic impact on a substantial number of small entities.
    In the case of coatings uses, our understanding is that only a 
single facility, the Lake City Army Ammunition Plant, is currently 
using coatings with nPB as the carrier solvent, and this facility could 
continue to use nPB following its current practices. Therefore, we 
consider there to be no economic impact of this rule on coatings users 
and have not done further analysis for this end use.
    Types of businesses that would be subject to this proposed rule 
include:
     Manufacturers of computers and electronic equipment that 
clean with nPB cleaning solvents (NAICS subsector 334).
     Manufacturers of appliances, electrical equipment, and 
components that require oil, grease, and solder flux to be cleaned off 
(NAICS subsection 335).
     Manufacturers of transportation equipment, such as 
aerospace equipment that requires cleaning either in a tank or with 
aerosols, or aircraft seating, which is assembled using adhesives 
containing nPB as a carrier solvent; and ship or boat builders applying 
adhesives with nPB (NAICS subsector 336).
     Manufacturers of furniture, including various kinds of 
furniture with cushions and countertops assembled using adhesives 
containing nPB as a carrier solvent (NAICS subsector 337).
     Foam fabricators, who assemble foam cushions or sponges 
using adhesives containing nPB as a carrier solvent (NAICS code 
326150).
    In order to consider the resources that affected small businesses 
have available to operate and to respond to the proposed regulatory 
requirements, EPA compared the cost of meeting the proposed regulatory 
requirements to small businesses' annual sales. In our analysis for 
this proposed rule, we used the average value of shipments for the 
products manufactured by the end user as a proxy for sales or revenues, 
since these data are readily available from the U.S. Department of 
Commerce. The following tables display the average value of shipments 
for different sizes of business and different NAICS subsectors or codes 
in the affected industrial sectors. EPA then used data from these 
sources to determine the potential economic impacts of this proposed 
rule on small businesses.

   Table 15.--Average Value of Shipments in NAICS Subsectors Using Aerosol Solvents, by Number of Employees at
                                                    Business
----------------------------------------------------------------------------------------------------------------
                                                            Average value of shipments per business ($) by NAICS
                                                                               subsector code
                                                           -----------------------------------------------------
              Number of employees at business                                  335, electrical
                                                              334, computer      equipment,           336,
                                                             and electronic    appliance, and    transportation
                                                                products        component mfg       equipment
----------------------------------------------------------------------------------------------------------------
1 to 4 employees..........................................           345,007           315,772           412,460
5 to 9 employees..........................................         1,317,238         1,243,065         1,414,384
10 to 19 employees........................................         2,566,913         2,483,327         2,573,352

[[Page 30200]]

 
20 to 49 employees........................................         5,672,245         5,389,945         5,738,739
50 to 99 employees........................................        12,951,836        12,650,236        12,735,583
100 to 249 employees......................................        31,258,875        31,290,638        34,256,544
250 to 499 employees......................................        84,270,454        77,279,974        86,911,454
Avg. value ship small businesses in sub-sector............         8,261,788         9,539,205        11,029,561
Avg. value ship all businesses in subsector...............        20,810,094        13,417,905        45,029,773
Avg. value shipments subset small businesses using nPB....        11,246,045        12,066,562        13,422,547
----------------------------------------------------------------------------------------------------------------


        Table 16.--Average Value of Shipments in NAICS Categories Using nPB as a Carrier Solvent in Adhesives, by Number of Employees at Business
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                          Average value of shipments per small business ($) by NAICS sub sector
                                                               -----------------------------------------------------------------------------------------
                                                                                                         326150,
                Number of employees at business                      337121,        337110, wood      urethane and      336360, motor     337124, metal
                                                                   upholstered     kitchen cabinet     other foam      vehicle seating      household
                                                                    household     and counter tops  products (except    and interior        furniture
                                                                    furniture                         polystyrene)          trim
--------------------------------------------------------------------------------------------------------------------------------------------------------
1 to 4 employees..............................................           234,345           156,833           496,318           425,863           187,950
5 to 9 employees..............................................           963,021           622,744         1,305,183         1,728,132           903,393
10 to 19 employees............................................         1,771,416         1,141,119         3,152,283         3,082,486         1,431,480
20 to 49 employees............................................         3,653,623         2,619,197         6,615,331         5,508,370         3,538,684
50 to 99 employees............................................         8,089,968         7,386,365        13,281,000        14,088,500         7,547,536
100 to 249 employees..........................................        17,502,175        17,151,091        31,524,872        44,310,286        19,821,719
250 to 499 employees..........................................        40,250,813        55,982,674        64,119,800       123,803,610              d(1)
Avg. Small Businesses in Sub sector...........................         3,588,297         1,150,768        10,472,992        12,542,725         3,141,720
Avg. ALL Businesses in Sub sector.............................         5,490,101         1,475,602        11,110,822        44,808,573         5,239,747
Avg. Subset Small Businesses using nPB........................        11,519,540         5,999,622        18,950,068        12,019,847        20,401,301
--------------------------------------------------------------------------------------------------------------------------------------------------------
\(1)\ ``d'' designates ``Data withheld to avoid disclosing data of individual companies; data are included in higher level totals.'' The average value
  of shipments for businesses estimates those values marked with ``d,'' and thus may be overestimated or underestimated.

    This proposed rule would list nPB as unacceptable for use in 
adhesives and aerosols. The available alternatives identified include 
adhesive formulations based on water, methylene chloride, or flammable 
solvents such as acetone and aerosol formulations of flammable 
solvents, combustible solvents, blends of trans-dichloroethylene and 
HFEs or HFCs, and HCFC-225ca/cb. We considered various aspects of the 
cost of switching to other alternatives, including the cost of meeting 
OSHA requirements and the cost of the alternative adhesive. We 
specifically request public comment on the assumptions and costs used 
in EPA's analysis (US EPA, 2007).
    We estimate that up to 9 small businesses using nPB-based 
adhesives, or roughly 3% of the 280 or so small businesses that use 
nPB-based adhesives, would experience a cost increase (i.e., an impact) 
of greater than 1.0% of annual sales, and no small businesses would 
experience an impact of greater than 3% of annual sales if this 
proposed rule became final. For small businesses using nPB-based 
aerosols, we estimate that approximately 249 would experience a cost 
increase of greater than 1.0% of annual sales. This equates to roughly 
8% of the 3100 or so small businesses currently using nPB-based aerosol 
solvents. No small businesses using aerosols would experience an impact 
of greater than 3% of annual sales. Approximately eight percent of all 
3380 or so small businesses choosing to use nPB in these end uses would 
experience an impact of greater than 1.0% of annual sales and no small 
businesses would experience an impact of greater than 3.0% of annual 
sales. Because of the small total number and small percentage of 
affected businesses that would experience an impact of greater than 
either 1.0% or 3.0% of annual sales, EPA does not consider this 
proposed rule to have a significant economic impact on a substantial 
number of small businesses.
    We also analyzed the potential small business impacts of the 
proposed alternate approach. Under the proposed alternate approach, 
users would have to: (1) Meet an exposure level of 20 ppm on an eight-
hour time-weighted average, (2) monitor workers' exposure to nPB using 
a personal breathing zone sampler on an eight-hour time-weighted 
average initially and periodically (every 6 months or longer, depending 
on the concentration during initial monitoring), and (3) keep records 
of the worker exposure data on site at the facility for at least three 
years from the date of the measurement. We assume that the cost of 
following the proposed alternate approach is the cost of installing 
ventilation for aerosols and adhesives or emission controls for solvent 
cleaning, the cost of using personal protective equipment, and the cost 
of monitoring worker exposure. Approximately 67 to 387 aerosol solvent 
users (2 to 13 percent), 25 to 54 adhesive users (9 to 19 percent), and 
2.6 to 12.6 percent of all 3380 or so small businesses would experience 
impacts of greater than 1% of annual sales if they chose to use nPB 
subject to the proposed use conditions rather than switching to another 
ODS substitute.

[[Page 30201]]

Four to nine users of nPB-based adhesives, or less than 1% of all small 
businesses affected by this proposal, would experience impacts of 3% or 
greater of annual sales under the proposed alternate approach. Based on 
this analysis, the proposed alternate approach would not create a 
significant adverse economic impact on a substantial number of small 
entities.
    Although this proposed rule would not have a significant economic 
impact on a substantial number of small entities if it became final, 
EPA nonetheless has tried to reduce the impact of this rule on small 
entities. Before selecting preferred the regulatory option in this 
proposed rule, we considered a number of regulatory options, such as:
     Placing a narrowed use limit on the use of nPB in 
adhesives and aerosols that would allow its use only in those cases 
where alternatives are technically infeasible due to performance or 
safety issues. This would have required testing, recordkeeping, and 
some installation of capital equipment.
     Requiring that when nPB is used in adhesives or aerosols, 
it must be used with local ventilation equipment and personal 
protective equipment. This would have required further installation of 
capital equipment, without necessarily protecting workers as thoroughly 
as a required acceptable exposure limit or requiring a switch to 
another alternative.
     Prohibiting the use of nPB in all end uses.
     Retaining the previously proposed requirement for a limit 
on iPB content in nPB formulations.

The costs of a number of these options are included in EPA's analysis 
(US EPA, 2006; U.S. EPA, 2007).
    In developing our regulatory options, we considered information we 
learned from contacting small businesses using or selling nPB. EPA 
staff visited the site of a small business using nPB for cleaning 
electronics. We contacted several fabricators of foam cushions that 
have used adhesives containing nPB. We participated in meetings with a 
number of adhesive manufacturers and users of adhesives in furniture 
construction. We developed a fact sheet and updated our program Web 
site to inform small businesses about the proposed rule and to request 
their comments.
    We continue to be interested in the potential impacts of the 
proposed rule 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 
effects 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 this rule 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 the 
private sector in any one year. This proposed rule does not affect 
State, local, or tribal governments. The enforceable requirements of 
the rule for the private sector affect a number of end users in 
manufacturing. The estimated cost of the proposed requirements for the 
private sector is approximately $38.6 to 46.4 million per year, and the 
proposed alternate approach would cost the private sector approximately 
$ 42.3 to 67.5 million per year. Therefore, the impact of this rule on 
the private sector is less than $100 million per year. Thus, this rule 
is not subject to the requirements of sections 202 and 205 of the UMRA. 
EPA has determined that this rule contains no regulatory requirements 
that might significantly or uniquely affect small governments. This 
regulation applies directly to facilities that use these substances and 
not to governmental entities.

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 rule 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. This regulation applies directly 
to facilities that use these substances and not to governmental 
entities. Thus, Executive Order 13132 does not apply to this rule.

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 6, 2000), 
requires EPA to develop an accountable process to ensure ``meaningful 
and timely input by tribal officials in the development of regulatory 
policies that have tribal implications.'' ``Policies that have tribal 
implications'' is defined in the Executive Order to include regulations 
that have ``substantial direct effects on one or more Indian tribes, on 
the relationship between the Federal government and the Indian tribes, 
or on the distribution of power and responsibilities between the 
Federal government and Indian tribes.''
    This proposed rule does not have tribal implications. It will not 
have substantial direct effects on tribal governments, on the 
relationship between the Federal government and Indian tribes, or on 
the distribution of power and responsibilities between the

[[Page 30202]]

Federal government and Indian tribes, as specified in Executive Order 
13175.
    This proposed rule would not significantly or uniquely affect the 
communities of Indian tribal governments, because this regulation 
applies directly to facilities that use these substances and not to 
governmental entities. Thus, Executive Order 13175 does not apply to 
this proposed rule.

G. Executive Order 13045: Protection of Children From Environmental 
Health 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. The exposure limits and 
acceptability listings in this proposed rule apply to the workplace. 
These are areas where we expect adults are more likely to be present 
than children, and thus, the agents do not put children at risk 
disproportionately.
    The public is invited to submit or identify peer-reviewed studies 
and data, of which the agency may not be aware, that assessed results 
of early life exposure to nPB.

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

    This rule is not a ``significant energy action'' as defined in 
Executive Order 13211, ``Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use'' (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. This action would 
impact manufacturing of various metal, electronic, medical, and optical 
products cleaned with solvents containing nPB and products made with 
adhesives containing nPB. Further, we have concluded that this rule is 
not likely to have any adverse energy effects.

I. National Technology Transfer and Advancement Act

    As noted in the proposed rule, Section 12(d) of the National 
Technology Transfer and Advancement Act of 1995 (``NTTAA''), Public Law 
104-113, section 12(d) (15 U.S.C. 272 note) directs EPA to use 
voluntary consensus standards in its regulatory activities unless to do 
so would be inconsistent with applicable law or otherwise impractical. 
Voluntary consensus standards are technical standards (e.g., materials 
specifications, test methods, sampling procedures, and business 
practices) that are developed or adopted by voluntary consensus 
standards bodies. The NTTAA directs EPA to provide Congress, through 
OMB, explanations when the Agency decides not to use available and 
applicable voluntary consensus standards.
    This action does not involved technical standards. Therefore, EPA 
did not consider the use of any voluntary consensus standards. We note 
that the American Conference of Governmental Industrial Hygienists 
(ACGIH), although it sets voluntary standards, is not a voluntary 
consensus standards body. Therefore, use of an acceptable exposure 
limit from the ACGIH is not subject to the NTTAA.

XII. References

    The documents below are referenced in the preamble. All documents 
are located in the Air Docket at the address listed in section I.B.1 at 
the beginning of this document. Unless specified otherwise, all 
documents are available electronically through the Federal Docket 
Management System, Docket  EPA-HQ-OAR-2002-0064. Some specific 
items are available only in hard copy in dockets A-2001-07 or A-92-42 
(legacy docket numbers for SNAP nPB rule and for SNAP program and 
submissions). Numbers listed after the reference indicate the docket 
and item numbers.

Availability

Harper, 2005. Telephone call from M. Sheppard, EPA to Dr. S. Harper, 
ATK. Re: Availability of other methyl chloroform substitutes for the 
Lake City Army Ammunition Plant. October 11, 2005. (EPA-HQ-OAR-2002-
0064-0150)
IRTA, 2000. Alternative Adhesive Technologies in the Foam Furniture 
and Bedding Industries: A Cleaner Technologies Substitution 
Assessment, Cost and Performance Evaluation. Michael Morris and Katy 
Wolf, Institute for Research and Technical Assistance. Prepared for 
the U.S. EPA Office of Pollution Prevention Technology, June 2000. 
(A-2001-07, II-D-70)
Seilheimer, 2001. Telephone Log of April 4, 2001 call between 
Margaret Sheppard, EPA, and Bob Seilheimer, Imperial Adhesives. (A-
2001-07, II-B-5)
Williams, 2005. Notes on conversation of Ed Williams, Technical 
Manager, LPS Laboratories, and Margaret Sheppard, EPA. November 3, 
2005 (EPA-HQ-OAR-2002-0064-0198)

Impacts on the Atmosphere, Local Air Quality, and Other Environmental 
Impacts

Atmospheric and Environmental Research, Inc., 1995. Estimates of the 
Atmospheric Lifetime, Global Warming Potential and Ozone Depletion 
Potential of n-Propyl Bromide. Independent study prepared for 
Albemarle Corporation. (A-2001-07, II-D-17)
ATSDR, 1994. Toxicological Profile For Acetone. Agency for Toxic 
Substances and Disease Registry. May, 1994. Available at http://www.atsdr.cdc.gov/toxprofiles/tp21-c5.pdf (EPA-HQ-OAR-2002-0064-
0118)
ATSDR, 1996. Toxicological Profile For 1,2-Dichloroethene. Agency 
for Toxic Substances and Disease Registry. August, 1996. Available 
at http://www.atsdr.cdc.gov/toxprofiles/tp87-c5.pdf (EPA-HQ-OAR-
2002-0064-0113)
ATSDR, 1997. Toxicological Profile For Trichloroethylene. Agency for 
Toxic Substances and Disease Registry. September, 1997. Available 
athttp://www.atsdr.cdc.gov/toxprofiles/tp19-c5.pdf (EPA-HQ-OAR-2002-
0064-0123)
ATSDR, 2004. Draft Toxicological Profile For 1,1,1-Trichloroethane. 
Agency for Toxic Substances and Disease Registry. September, 2004. 
Updated draft for comment. Available at http://www.atsdr.cdc.gov/toxprofiles/tp70-c6.pdf (EPA-HQ-OAR-2002-0064-0132)
EDSTAC, 1998. Final Report of the Endocrine Disruptor Screening and 
Testing Advisory Committee. August, 1998. (EPA-HQ-OAR-2002-0064-
0136)
Fisher Scientific, 2001. Material Safety Data Sheet for acetone. 
Updated March 19, 2001. Available at  http://www.mhatt.aps.anl.gov/dohn/msds/acetone.html (EPA-HQ-OAR-2002-0064-0129)
Geiger et al., 1998. Geiger, D.L., Call, D.J., and Brooke, L.T. 
1988. Acute Toxicities of Organic Chemicals to Fathead Minnows 
(Pimephales promelas), Vol. 4. In: Center for Lake Superior 
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U.S. EPA, 1996. Guidelines for Reproductive Toxicity Risk 
Assessment. U.S. Environmental Protection Agency, Risk Assessment 
Forum, Washington, DC, 630/R-96/009, 1996. (EPA-HQ-OAR-2002-0064-
0109)
Wang et al., 2003. H. Wang, G. Ichihara, H. Ito, K. Kato, J. Kitoh, 
T. Yamada, X. Yu, S. Tsuboi, Y. Moriyama, and Y. Takeuchi. 2003. 
``Dose-Dependant Biochemical Changes in RateCentral Nervous System 
after 12-Week Exposure to 1-Bromopropane'' NeuroToxicology 24: 199-
206 (EPA-HQ-OAR-2002-0064-0088)
Werner, 2003. Comments from 3M on nPB proposed rule. (EPA-HQ-OAR-
2002-0064-0058).

[[Page 30206]]

WIL, 2001. WIL Research Laboratories. ``An inhalation two-generation 
reproductive toxicity study of 1-bromopropane in rats.'' Sponsored 
by the Brominated Solvent Consortium. May 24, 2001. (A-2001-07, II-
D-10)
Yamada T. et al., 2003. Exposure to 1-Bromopropane Causes Ovarian 
Dysfunction in Rats. Toxicol Sci 71:96-103 (EPA-HQ-OAR-2002-0064-
0097)

Listings for Each End Use

Beck and Caravati, 2003. Full citation above for ``Human Health'' 
section.
Calhoun County, 2005. Summary of Court Case against Franklin 
Technologies and Mid-South Adhesive Company in Calhoun County, MS. 
(EPA-HQ-OAR-2002-0064-0217)
Collatz, 2003. Comment entitled ``Addition of n-Propyl-Bromide to 
the Significant New Alternatives Policy (SNAP) List'' submitted by 
Mark Collatz, Director of Government Relations, The Adhesive and 
Sealant Council, Inc. 04-Aug-2003. (EPA-HQ-OAR-2002-0064-0066)
Confidential submission, 1998. Full citation above in ``Human 
Health'' section.
CSMA, 1998. Letter with attachments from J. DiFazio, Chemical 
Specialties Manufacturers Association to C. Newberg, EPA Re: 
Maintaining the Current Exemption under Section 610 of the Clean Air 
Act for Use of HCFC-141b in Electronic Cleaning and Aircraft 
Maintenance. September 10, 1998. (EPA-HQ-OAR-2002-0064-0153)
Harper, 2005. Full citation above for ``Availability'' section.
ICF, 2006a. Full citation above for section on ``Impacts on the 
atmosphere, local air quality, and other environmental impacts''.
Lake City Army Ammunition Plant, 2004. Full citation above in 
``Human Health''section.
Linnell, 2003. Comments from the Electronics Industry Alliance. (IV-
D-25/EPA-HQ-OAR-2002-0064 items -0043, -0044, and -0045)
Majersik et al., 2004. Full citation above for ``Human Health'' 
section.
Majersik et al, 2005. Full citation above for ``Human Health'' 
section.
Miller, 2005. Full citation above for ``Human Health'' section.
NIOSH, 2000a. U.S. Dept. of Health and Human Services, Letter to 
Marx Industries, Inc., February 1, 2000. Re: results of nPB exposure 
assessment survey conducted Nov. 16-17, 1999. (A-2001-07, II-D-7)
NIOSH, 2000b. U.S. Dept. of Health and Human Services, Letter to 
Custom Products Inc., December 21, 2000. Re: results of nPB exposure 
assessment survey conducted Nov. 16, 2000. (HHE Report 98-0153) (A-
2001-07, II-D-8)
NIOSH, 2001. U.S. Dept. of Health and Human Services, Letter to STN 
Cushion Company, March 7, 2001. Re: Results of nPB exposure 
assessment survey conducted November 14, 2000. (A-2001-07, II-D-9)
NIOSH, 2002a. Full citation above in ``Human Health'' section.
NIOSH, 2002b. Full citation above in ``Human Health'' section.
NIOSH, 2003a. NIOSH Health Hazard Evaluation Report 99-
0260-2906 Marx Industries, Inc. Sawmills, NC Available online at 
http://www.cdc.gov/niosh/hhe/reports/pdfs/1999-0260-2906.pdf. (EPA-
HQ-OAR-2002-0064-0094)
Raymond and Ford, 2005. Full citation above for ``Human Health'' 
section.
U.S. EPA, 2004. U.S. EPA Solvent Market Report: The U.S. Solvent 
Cleaning Industry and the Transition to Non Ozone Depleting 
Substances. Prepared for U.S. Environmental Protection Agency, 
Significant New Alternatives Policy (SNAP) Program by ICF 
Consulting. September 2004. (EPA-HQ-OAR-2002-0064-0106)
Werner, 2003. Full citation above for ``Human Health'' section.
Williams, 2005. Full citation above for ``Availability'' section.

What other options did EPA consider?

ACGIH, 2002. Industrial Ventilation: A Manual of Recommended 
Practice 23rd Edition. American Conference of Governmental 
Industrial Hygienists, Cincinnati, Ohio Available online at http://www.acgih.org.
CSMA, 1999. Full citation above for ``Decisions for Each Sector and 
End Use'' section.
Ensolv, 2006. Material Safety Data Sheet for Ensolv Solvents. Enviro 
Tech International. February, 2006. (EPA-HQ-OAR-2002-0064-0143)
ERG, 2004. Analysis of Health and Environmental Impacts of ODS 
Substitutes--Evaluating the need to set a short-term exposure or 
ceiling limit for n-propyl bromide. ERG. June 8, 2004.
ICF, 2006a. Full citation above for section on ``Impacts on the 
atmosphere, local air quality, and other environmental impacts''.
Lake City Army Ammunition Plant, 2004. Full citation above for 
``Decisions for Each Sector and End Use'' section.
Linnell, 2003. Full citation above for ``Ozone Depletion Potential 
and Other Environmental Impacts'' section.
Micro Care, 2006. Web page for Micro Care Corporation on the Trigger 
GripTM Dispensing System. URL at http://www.microcare.com/products/PDF/PS-05T_G.html, last update January 
19, 2006. Also see http://www.microcare.com/images/PDF-CSP-Allied%20Worker%20Exposures.pdf.
NIOSH, 2000a. U.S. Dept. of Health and Human Services, Letter to 
Marx Industries, Inc., February 1, 2000. Re: Results of nPB exposure 
assessment survey conducted Nov. 16-17, 1999. (A-2001-07, II-D-7)
NIOSH, 2002a. NIOSH Health Hazard Evaluation Report: HETA  
98-0153-2883; Custom Products, Inc.; Mooresville, NC. National 
Institute for Occupational Safety and Health. November 2002. 
Available online at http://www.cdc.gov/niosh/hhe/reports/pdfs/1998-0153-2883.pdf. (EPA-HQ-OAR-2002-0064-0093)
NIOSH. 2002b. NIOSH Health Hazard Evaluation Report: HETA 
2000-0410-2891; STN Cushion Company; Thomasville, NC. 
National Institute for Occupational Safety and Health. August 2002. 
Available online at http://www.cdc.gov/niosh/hhe/reports/pdfs/2000-0410-2891.pdf. (A-2001-07, II-A-31)
NIOSH, 2003a. NIOSH Health Hazard Evaluation Report 99-
0260-2906 Marx Industries, Inc. Sawmills, NC Available online at 
http://www.cdc.gov/niosh/hhe/reports/pdfs/1999-0260-2906.pdf. (EPA-
HQ-OAR-2002-0064-0094)
NIOSH, 2003b. Method 1025 for 1- and 2-Bromopropane. NIOSH Manual of 
Analytical Methods, 4th Edition, March 15, 2003. (EPA-HQ-OAR-2002-
0064-0173)
NIOSH, 2003c. Method 1003 for Halogenated Hydrocarbons. NIOSH Manual 
of Analytical Methods, 4th Edition, March 15, 2003. (EPA-HQ-OAR-
2002-0064-0134)
Williams, 2005. Full citation above for ``Availability'' section.

What are the anticipated costs of this regulation to the regulated 
community?

U.S. EPA, 2006. Analysis of Economic Impacts of nPB Rulemaking. 
2006.

Comparison of EPA's June 2003 Proposal and This Proposal

ACGIH, 2005. Full citation above for ``Human Health'' section.
CERHR, 2002a. Full citation above for ``Human Health'' section.
CERHR, 2002b. Full citation above for ``Human Health'' section.
Doull and Rozman, 2001. Derivation of an Occupational Exposure Limit 
for n-Propyl Bromide, prepared by John Doull, PhD., M.D., and Karl 
K. Rozman, PhD., D.A.B.T. submitted by Envirotech International, 
Inc. (A-2001-07, II-D-14)
ICF, 2001. Brief Discussion of the BMD Approach: Overview of its 
Purpose, Methods, Advantages, and Disadvantages. Prepared for U.S. 
EPA. (A-2001-07, II-A-52)
ICF, 2002a. Full citation above for ``Human Health'' section.
ICF, 2002b. Comments on the NTP-Center for the Evaluation of Risks 
to Human Reproduction, Final Report on 1-Bromopropane. Cover Letter 
Dated 5/9/02. (EPA-HQ-OAR-2002-0064-0013)
ICF, 2006a. Full citation above for section on ``Impacts on the 
atmosphere, local air quality, and other environmental impacts''.
Rodricks, 2002. Full citation above for ``Human Health'' section.
Rozman and Doull, 2002. Full citation above for ``Human Health'' 
section.
Rozman and Doull, 2005. Full citation above for ``Human Health'' 
section.
SLR International, 2001. Full citation above for ``Human Health'' 
section.
Stelljes and Wood, 2004. Full citation above for ``Human Health'' 
section.
Stelljes, ME. 2005. Full citation above for ``Human Health'' 
section.

[[Page 30207]]

TERA, 2004. Full citation above for ``Human Health'' section.
WIL, 2001. Full citation above for ``Human Health'' section.

How can I use nPB as safely as possible?

ACGIH, 2002. Full citation above for ``What other options did EPA 
consider'' section.

Statutory and Executive Order Reviews

U.S. EPA, 2006. Analysis of Economic Impacts of nPB Rulemaking. 
2006.
U.S. EPA, 2007. Analysis of Economic Impacts of Proposed nPB Rule 
for Aerosols and Adhesives. 2007.

List of Subjects in 40 CFR Part 82

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Reporting and recordkeeping requirements.

    Dated: May 15, 2007.
Stephen L. Johnson,
Administrator.
    For the reasons set out in the preamble, 40 CFR part 82 is proposed 
to be amended as follows:

PART 82--PROTECTION OF STRATOSPHERIC OZONE

    1. The authority citation for Part 82 continues to read as follows:

    Authority: 42 U.S.C. 7414, 7601, 7671--7671q.

    2. Subpart G is amended by adding Appendix S to read as follows:

Subpart G--Significant New Alternatives Policy Program

* * * * *

Appendix S to Subpart G--Substitutes Subject to Use Restrictions and 
Unacceptable Substitutes

    Listed in the May 30, 2007 final rule.

                                       Aerosols--Unacceptable Substitutes
----------------------------------------------------------------------------------------------------------------
              End use                       Substitute                 Decision           Further information
----------------------------------------------------------------------------------------------------------------
Aerosol solvents..................  n-propyl bromide (nPB) as   Unacceptable.........  EPA finds unacceptable
                                     a substitute for CFC-113,                          risks to human health in
                                     HCFC-141b, and methyl                              this end use compared to
                                     chloroform.                                        other available
                                                                                        alternatives. nPB, also
                                                                                        known as 1-bromopropane,
                                                                                        is Number 106-94-5 in
                                                                                        the CAS Registry.
----------------------------------------------------------------------------------------------------------------


            Adhesives, Coatings, and Inks--Substitutes That Are Acceptable Subject to Use Conditions
----------------------------------------------------------------------------------------------------------------
       End use             Substitute            Decision            Use conditions        Further information
----------------------------------------------------------------------------------------------------------------
Coatings              n-propyl bromide     Acceptable subject   Use is limited to        EPA recommends the use
                       (nPB) as a           to use conditions.   coatings at facilities   of personal protective
                       substitute for                            that, as of May 30,      equipment, including
                       methyl chloroform,                        2007, have provided      chemical goggles,
                       CFC-113, and HCFC-                        EPA information          flexible laminate
                       141b.                                     demonstrating            protective gloves and
                                                                 acceptable workplace     chemical-resistant
                                                                 exposures.               clothing.
                                                                                         EPA expects that all
                                                                                          users of nPB would
                                                                                          comply with any final
                                                                                          Permissible Exposure
                                                                                          Limit that the
                                                                                          Occupational Safety
                                                                                          and Health
                                                                                          Administration issues
                                                                                          in the future under 42
                                                                                          U.S.C. 7610(a).
                                                                                         nPB, also known as 1-
                                                                                          brompropane, is Number
                                                                                          106-94-5 in the CAS
                                                                                          Registry.
----------------------------------------------------------------------------------------------------------------
As of May 30, 2007, the Lake City Army Ammunition Plant is the only facility using nPB in coatings that has
  provided information to EPA that meets this condition.


                             Adhesives, Coatings, and Inks--Unacceptable Substitutes
----------------------------------------------------------------------------------------------------------------
              End use                       Substitute                 Decision           Further information
----------------------------------------------------------------------------------------------------------------
Adhesives.........................  n-propyl bromide (nPB) as   Unacceptable.........  EPA finds unacceptable
                                     a substitute for CFC-113,                          risks to human health in
                                     HCFC-141b, and methyl                              this end use compared to
                                     chloroform.                                        other available
                                                                                        alternatives. nPB, also
                                                                                        known as 1-bromopropane,
                                                                                        is Number 106-94-5 in
                                                                                        the CAS Registry.
----------------------------------------------------------------------------------------------------------------

 [FR Doc. E7-9706 Filed 5-29-07; 8:45 am]
BILLING CODE 6560-50-P