Number range CHAPTER**ENVIRONMENTAL PROTECTION AGENCY**

**40 CFR Part 82**

**\[EPA-HQ-OAR-2002-0064; FRL-xxxx-x\]**

**RIN 2060-AK26**

**Protection of Stratospheric Ozone: Listing of Substitutes for
Ozone-Depleting**

**Substances--n-Propyl Bromide**

**AGENCY: Environmental Protection Agency.**

**ACTION: Notice of Proposed Rulemaking**

**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 acceptable substitute for
methyl chloroform and chlorofluorocarbon (CFC)-113 in the solvent
cleaning sector and 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. We also
recommend that users be exposed to no more than 17 parts per million of
nPB on an eight-hour, time-weighted average. This action also proposes
to list nPB as an unacceptable substitute for methyl chloroform,
CFC-113, and 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. This proposal
supersedes EPA's proposal of June 3, 2003 on the acceptability of nPB as
a substitute for ozone-depleting substances.

EPA is also taking comment on an alternate proposal in which nPB would
be acceptable, subject to use conditions, as a substitute for
ozone-depleting substances. Under that alternate proposal, users would
be allowed to use nPB only if they meet a workplace exposure limit of 17
ppm on an eight-hour time-weighted average, monitor workers' exposure to
nPB with personal breathing zone samples on an eight-hour time-weighted
average, both initially and periodically, and keep records of the worker
exposure data on site at the facility.

**DATES:** Comments must be received in writing by **\[Insert date 60
days after Federal Register publication date\].** Under the Paperwork
Reduction Act, comments on the information collection provisions must be
received by OMB on or before \[*insert date* **\[thirty\]** *days after
date of publication in the* **Federal Register**\]. Any person
interested in requesting a public hearing, must submit such request on
or before \[insert 30 days from date of publication in the Federal
Register\]. 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. Inquires 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](http://www.regulations.gov/). Follow
    the on-line instructions for submitting comments.

-   E-mail: A-And-R-Docket@epa.gov

-   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 B102, 1301
    Constitution Ave., NW, Washington, D.C., 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
    [www.regulations.gov](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
    www.regulations.gov websites 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 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
    [www.regulations.gov](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
    [www.regulations.gov](http://www.regulations.gov/) or in hard copy
    at the Air and Radiation Docket, EPA/DC, EPA West, Room B102, 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) 343-2338, e-mail address:
    sheppard.margaret@epa.gov. Notices and rulemakings under the SNAP
    program are available on EPA's Stratospheric Ozone World Wide Web
    site at www.epa.gov/ozone/snap/regs.

    **SUPPLEMENTARY INFORMATION:**

    Table of Contents

#  {#section .unnumbered}

I. General InformationA. 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. Is EPA listing n--propyl bromide
as an acceptable substitute for ozone-depleting substances?A. What is
EPA proposing today?B. What is n-propyl bromide?C. What industrial end
uses are included in our proposed decision?D. What does an
unacceptability determination on adhesives and aerosols mean?E. What is
the scope of the proposed determination for coatings?F. How would the
use conditions in the alternate proposal work? IV. What criteria did EPA
consider in preparing this proposal? A. Availability B. Impacts on the
atmosphere and local air quality C. Ecosystem and other environmental
impacts D. Flammability and fire safety E. Impact on human healthV. How
did EPA derive the proposed workplace exposure limit and community
exposure guideline used to assess impacts on human health? A. Workplace
exposure limit B. Community exposure guidelineVI. What listing is EPA
proposing for each sector or end use, and why? A. Solvent CleaningB.
Aerosol SolventsC. AdhesivesD. CoatingsVII How did EPA choose the use
conditions in the alternate proposal, and why?

A. Use conditions and their rationale

B. Advantages and disadvantages of the alternate proposal

VIII\. What other options did EPA consider?

A. Regulatory options based on the ACGIH\'s Threshold Limit Value

B. Regulatory options requiring ventilation equipment

XI. 

IX\. What are the anticipated costs of this regulation to the regulated
community?X. Comparison of EPA's June 2003 proposal and this proposalHow
can I use nPB as safely as possible?

XII. 

> Statutory and Executive Order Reviews

A.  
B.  
C.  
D.  
E.  
F.  
G.  
H.  
I.  

#  {#section-1 .unnumbered}

Executive Order 12866: Regulatory Planning and Review Paperwork
Reduction ActRegulatory Flexibility Act (RFA)Unfunded Mandates Reform
ActExecutive Order 13132: FederalismExecutive Order 13175: Consultation
and Coordination with Indian Tribal GovernmentsExecutive Order 13045:
Protection of Children from Environmental Health and Safety Risks
Executive Order 13211: Actions that Significantly Affect Energy Supply,
Distribution, or UseNational Technology Transfer and Advancement Act

XIII. References

      **I. General Information**

      A. Does this action apply to me?

      This proposed rule would regulate the use of n-propyl bromide as a
      solvent used in industrial equipment for metals cleaning,
      electronics cleaning, or precision cleaning, 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 clean metal parts, such as automotive manufacturers,
    machine shops, machinery manufacturers, and electroplaters.

-   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

  ------------------- ------------ -------------------------------------------
  Category            NAICS code   Description of regulated entities
                      or subsector 

  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 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.

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-   Explain your views as clearly as possible, avoiding the use of
    profanity or personal threats.

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-   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

    *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, C~2~Cl~3~F~3~, 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-123*--the ozone-depleting chemical
    1,2-dichloro-1,1,2-trifluoroethane, CAS Reg. No. 306-83-2

    *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, C~3~H~7~Br, CAS Reg. No. 75-26-3, an
    isomer of n-propyl bromide; also called 2-bromopropane or 2-BP

    *K~oc~*--organic carbon partition coefficient, for determining the
    tendency of a chemical to bind to organic carbon in soil

    *LC~50~* --the concentration at which 50% of test animals die

    *LOAEL*--Lowest Observed Adverse Effect Level

    *Log* *K~ow~*--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

    *NESHAP*--National Emission Standard for Hazardous Air Pollutants

    *NIOSH*--National Institute for Occupational Safety and Health

    *NOAEL*--No Observed Adverse Effect Level

    *NOEL*--No Observed Effect Level

    *nPB*--n-propyl bromide, C~3~H~7~Br, 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

    *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,
C~2~Cl~3~H; also call trichloroethylene*TERA*--Toxicological Excellence
for Risk Assessment*TLV*--Threshold Limit Value™

*TSCA*--Toxic Substances Control Act

*TWA*--time-weighted average

*UF*--uncertainty factor

*UMRA*--Unfunded Mandates Reform Act

*U.S.C.*--United States Code

*VMSs*--volatile methyl siloxanes

*VOC*--volatile organic compound

*WEL*--workplace exposure limit

**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]{.underline}--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]{.underline}\--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]{.underline}\--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]{.underline}\--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]{.underline}\--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]{.underline}\--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
    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]{.underline}. 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 either 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]{.underline} 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]{.underline} citations at
    http://www.epa.gov/ozone/snap/chron.html.

    **III. Is EPA listing n--propyl bromide as an acceptable substitute
    for ozone-depleting substances?**

     A. What is EPA proposing today?

    In this action, EPA proposes to list n-propyl bromide (nPB) as (1)
    acceptable for use as a substitute for CFC-113[^1] and methyl
    chloroform[^2] in solvent cleaning in the metals, precision and
    electronics cleaning end uses; (2) unacceptable for use as a
    substitute for CFC-113, methyl chloroform and HCFC-141b[^3] in the
    adhesive and aerosol solvent end uses; and (3) acceptable subject to
    use conditions (limited to coatings at facilities that have provided
    EPA with information as of \[INSERT DATE OF PUBLICATION\]
    demonstrating their ability to meet the recommended workplace
    exposure limit) 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).

    We also are taking comment on an alternate proposal. Under the
    alternate proposal, nPB would be acceptable, subject to use
    conditions, in the metals, electronics, and precision cleaning,
    aerosol solvent, adhesives, and coatings end uses. The use of nPB in
    these end uses would be subject to conditions that users must (1)
    meet a workplace exposure limit of 17 ppm on an eight-hour
    time-weighted average (8-hr TWA), (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.

    B. 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 C~3~H~7~Br.
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®, EnSolv®, and Solvon® cleaners; Pow-R-Wash® 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.

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

1.  Solvent Cleaning

    General metals, precision, and electronics cleaning includes
    cleaning with industrial cleaning equipment such as vapor
    degreasers, in-line cleaning systems, or automated equipment used
    for cleaning below the boiling point. We understand that nPB is use
    primarily for cleaning in vapor degreasers. Manual cleaning, such as
    pail-and-brush, hand wipe, recirculating over-spray
    ("sink-on-a-drum") parts washers, immersion cleaning into dip tanks
    with manual parts handling, and use of squirt bottles, is not
    currently regulated under the SNAP program. However, EPA is
    reviewing whether these applications should be covered under the
    SNAP program, and for now, we do not recommend the use of nPB in
    these applications because of the difficulty of controlling
    emissions to a safe level. EPA also does not regulate the use of
    solvents as carriers for flame retardants, dry cleaning, or paint
    stripping.

> 2\. 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

• Spinnerrette lubricants and cleaning sprays used in the production of
synthetic fibers.

Recently, users of HCFC-141b, in particular, have been considering the
use of nPB as an ODS substitute in these industrial applications.

3.  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.

4.  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 in an ammunition coating (sealant).

    5\. Proposed Text for Listing Decisions

    In the proposed regulatory text at the end of this document, you
    will find our proposed listing decisions for those end uses that
    would be unacceptable or acceptable subject to narrowed use limits.
    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. Although EPA expects nPB
    users to conform to all information included in a final listing, the
    "further information" is not part of the regulatory decision, and
    therefore is not mandatory. Also, there may be other legal
    obligations pertaining to the manufacture, use, handling, and
    disposal of nPB that are not included in the information listed in
    the tables. Our listings of substitutes that are acceptable without
    restriction are not provided in the Code of Federal Regulations
    because they are not regulatory requirements. EPA is proposing to
    find nPB acceptable without restrictions in some end uses, rather
    than issuing the listing in a notice, in order to give the public
    the opportunity to comment on issues that are relevant to all end
    uses. You may find lists of substitutes that are acceptable without
    restrictions on EPA's SNAP web site at
    http://www.epa.gov/ozone/snap/lists/index.html. Our proposed
    decisions and the alternate proposals for each end use are
    summarized below in tables 2 through 8.

    ***PROPOSED LISTINGS***

    Table 2. SOLVENT CLEANING

    PROPOSED ACCEPTABLE SUBSTITUTES

+---------+----------+-------+----------------------------------------+
| End Use | Su       | Dec   | Further Information                    |
|         | bstitute | ision |                                        |
+=========+==========+=======+========================================+
| Metals  | n-propyl | Accep | EPA recommends the use of personal     |
| cl      | bromide  | table | protective equipment, including        |
| eaning, | (nPB) as |       | chemical goggles, flexible laminate    |
| elec    | a        |       | protective gloves and                  |
| tronics | su       |       | chemical-resistant clothing.           |
| cl      | bstitute |       |                                        |
| eaning, | for      |       | EPA expects that all users of nPB will |
| and     | CFC-113  |       | adhere to a voluntary acceptable       |
| pr      | and      |       | exposure limit of 17 parts per million |
| ecision | methyl   |       | (ppm) on an 8-hour time-weighted       |
| c       | ch       |       | average and would comply with any      |
| leaning | loroform |       | final Permissible Exposure Limit that  |
|         |          |       | the Occupational Safety and Health     |
|         |          |       | Administration issues in the future.   |
|         |          |       |                                        |
|         |          |       | nPB, also known as 1-bromopropane, is  |
|         |          |       | Number 106-94-5 in the Chemical        |
|         |          |       | Abstracts Service (CAS) Registry.      |
+---------+----------+-------+----------------------------------------+

Note: In accordance with the limitations provided in Section 310(a) of
the Clean Air Act (42 U.S.C. 7610(a)), nothing in this table shall
affect the Occupational Safety and Health Administrations' authority to
promulgate and enforce standards and other requirements under the
Occupational Safety and Health Act of 1970 (29 U.S.C. 651 et seq.)

Table 3. AEROSOLS

PROPOSED UNACCEPTABLE SUBSTITUTES

  ---------- -------------- -------------- -------------------------------------
  End Use    Substitute     Decision       Further Information

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

Table 4. ADHESIVES, COATINGS, AND INKS

PROPOSED UNACCEPTABLE SUBSTITUTES

  ----------- ---------------- -------------- --------------------------------
  End Use     Substitute       Decision       Further Information

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

Table 5. ADHESIVES, COATINGS, AND INKS

SUBSTITUTES THAT ARE PROPOSED ACCEPTABLE SUBJECT TO USE CONDITIONS

+-----+-------+-------+--------------+--------------------------------+
| End | Subst | Dec   | Use          | Further Information            |
| Use | itute | ision | Conditions   |                                |
+-----+-------+-------+--------------+--------------------------------+
| Co  | n-p   | Accep | Use is       | EPA recommends the use of      |
| ati | ropyl | table | limited to   | personal protective equipment, |
| ngs | br    | su    | coatings at  | including chemical goggles,    |
|     | omide | bject | facilities   | flexible laminate protective   |
|     | (nPB) | to    | that have    | gloves and chemical-resistant  |
|     | as a  | use   | provided EPA | clothing.                      |
|     | subst | condi | information  |                                |
|     | itute | tions | d            | EPA expects that all users of  |
|     | for   |       | emonstrating | nPB will adhere to a voluntary |
|     | m     |       | their        | acceptable exposure limit of   |
|     | ethyl |       | ability to   | 17 ppm on an 8-hour            |
|     | c     |       | meet the     | time-weighted average and      |
|     | hloro |       | recommended  | would comply with any final    |
|     | form, |       | workplace    | Permissible Exposure Limit     |
|     | CFC   |       | exposure     | that the Occupational Safety   |
|     | -113, |       | limit as of  | and Health Administration      |
|     | and   |       | \[INSERT     | issues in the future.          |
|     | HCFC  |       | DATE OF      |                                |
|     | -141b |       | PU           | nPB, also known as             |
|     |       |       | BLICATION\]. | 1-bromopropane, is Number      |
|     |       |       |              | 106-94-5 in the CAS Registry.  |
+-----+-------+-------+--------------+--------------------------------+

Note 1: In accordance with the limitations provided in Section 310(a) of
the Clean Air Act (42 U.S.C. 7610(a)), nothing in this table shall
affect the Occupational Safety and Health Administrations' authority to
promulgate and enforce standards and other requirements under the
Occupational Safety and Health Act of 1970 (29 U.S.C. 651 et seq.)

Note 2: As of \[INSERT DATE OF PUBLICATION\], the Lake City Army
Ammunition Plant is the only facility that has provided information to
EPA demonstrating the facility\'s ability to meet the recommended
workplace exposure limit when using nPB in coatings.

*ALTERNATE PROPOSAL*

Table 6. SOLVENT CLEANING

*Alternate Proposal:* SUBSTITUTES THAT ARE PROPOSED ACCEPTABLE SUBJECT
TO USE CONDITIONS

+----+-----+-----+-------------------------------------+------------+
| E  | S   | De  | Use Conditions                      | Further    |
| nd | ubs | cis |                                     | I          |
| U  | tit | ion |                                     | nformation |
| se | ute |     |                                     |            |
+----+-----+-----+-------------------------------------+------------+
| Me | n-  | A   | 1)  The owner or operator of a      | EPA        |
| ta | pro | cce |     facility must ensure that users | recommends |
| ls | pyl | pta |     of nPB achieve a workplace      | the use of |
| c  | b   | ble |     exposure limit (WEL) of 17 ppm  | personal   |
| le | rom | s   |     on an 8-hour time-weighted      | protective |
| an | ide | ubj |     average.                        | equipment, |
| in | (n  | ect |                                     | including  |
| g, | PB) | to  | 2)  The owner or operator of a      | chemical   |
| e  | as  | use |     facility must ensure that       | goggles,   |
| le | a   | c   |     workers using nPB are monitored | flexible   |
| ct | s   | ond |     for their exposure to nPB using | laminate   |
| ro | ubs | iti |     personal breathing zone samples | protective |
| ni | tit | ons |     on an eight-hour, time-weighted | gloves and |
| cs | ute |     |     average (8-hr TWA) no later     | chemical   |
| c  | for |     |     than 90 days after the          | -resistant |
| le | CF  |     |     effective date of this rule.    | clothing.  |
| an | C-1 |     |                                     | The        |
| in | 13, |     | 3)  If the most recent data from    | American   |
| g, | H   |     |     exposure monitoring shows all   | Conference |
| a  | CFC |     |     personal breathing exposures to | of         |
| nd | -14 |     |     be at or below 8.5 ppm, no      | Go         |
| p  | 1b, |     |     periodic exposure monitoring is | vernmental |
| re | and |     |     required. If the most recent    | Industrial |
| ci | met |     |     data from exposure monitoring   | Hygienists |
| si | hyl |     |     shows all exposures to be at or | recommends |
| on | c   |     |     below 17 ppm, but some above    | a          |
| cl | hlo |     |     8.5 ppm, the owner or operator  | threshold  |
| ea | rof |     |     must take personal breathing    | limit      |
| ni | orm |     |     zone samples for nPB users at   | value of   |
| ng |     |     |     least once during the next six  | 10 ppm.    |
|    |     |     |     months.                         |            |
|    |     |     |                                     | nPB, also  |
|    |     |     | 4)  The owner or operator may       | known as   |
|    |     |     |     discontinue the periodic 8-hour | 1-bro      |
|    |     |     |     TWA monitoring for nPB users at | mopropane, |
|    |     |     |     the facility where at least two | is Number  |
|    |     |     |     consecutive sets of             | 106-94-5   |
|    |     |     |     measurements taken at least     | in the CAS |
|    |     |     |     seven days apart are below 8.5  | Registry.  |
|    |     |     |     ppm.                            |            |
|    |     |     |                                     | Note that  |
|    |     |     | 5)  The owner or operator must      | the        |
|    |     |     |     determine the exposure of each  | Oc         |
|    |     |     |     nPB user by either taking       | cupational |
|    |     |     |     personal breathing zone air     | Safety and |
|    |     |     |     samples of each user\'s         | Health     |
|    |     |     |     exposure or samples that are    | Admi       |
|    |     |     |     representative of each user\'s  | nistration |
|    |     |     |     exposure. The samples are       | (OSHA) may |
|    |     |     |     representative where the owner  | establish  |
|    |     |     |     or operator has taken one or    | a final    |
|    |     |     |     more personal breathing zone    | P          |
|    |     |     |     air samples for at least one    | ermissible |
|    |     |     |     nPB user in each job            | Exposure   |
|    |     |     |     classification in a work area   | Limit      |
|    |     |     |     during every work shift, and    | (PEL)      |
|    |     |     |     the nPB user sampled is         | standard   |
|    |     |     |     expected to have the highest    | in the     |
|    |     |     |     exposure to nPB.                | workplace  |
|    |     |     |                                     | at 29 CFR  |
|    |     |     | 6)  The owner or operator also must | part 1910  |
|    |     |     |     perform exposure monitoring     | under 42   |
|    |     |     |     when a change in workplace      | U.S.C.     |
|    |     |     |     conditions indicates that       | 7610(a).   |
|    |     |     |     employee exposure may have      |            |
|    |     |     |     increased or whenever new       | OSHA's     |
|    |     |     |     applications of nPB are         | standard   |
|    |     |     |     introduced. Perform exposure    | on access  |
|    |     |     |     monitoring before making        | to         |
|    |     |     |     planned changes, and perform    | employee   |
|    |     |     |     monitoring no later than 7 days | exposure   |
|    |     |     |     after an emergency change in    | and        |
|    |     |     |     conditions.                     | medical    |
|    |     |     |                                     | records    |
|    |     |     | 7)  All personal breathing zone     | requires   |
|    |     |     |     samples must be analyzed either | retaining  |
|    |     |     |     by NIOSH method 1003 or 1025 or | exposure   |
|    |     |     |     by another method that is       | records    |
|    |     |     |     accurate to [+]{.underline} 25% | for at     |
|    |     |     |     at a 95 percent confidence      | least 30   |
|    |     |     |     level.                          | years (29  |
|    |     |     |                                     | CFR        |
|    |     |     | 8)  The owner or operator must keep | 1910.102   |
|    |     |     |     records of nPB worker exposure  | 0(d)(ii)). |
|    |     |     |     data at the facility for at     |            |
|    |     |     |     least three years from the date |            |
|    |     |     |     the measurements were taken.    |            |
+----+-----+-----+-------------------------------------+------------+

Note: In accordance with the limitations provided in Section 310(a) of
the Clean Air Act (42 U.S.C. 7610(a)), nothing in this table shall
affect the Occupational Safety and Health Administrations' authority to
promulgate and enforce standards and other requirements under the
Occupational Safety and Health Act of 1970 (29 U.S.C. 651 et seq.)

Table 7. AEROSOLS

*Alternate Proposal:* SUBSTITUTES THAT ARE PROPOSED ACCEPTABLE SUBJECT
TO USE CONDITIONS

+---+-----+-----+--------------------------------------+------------+
| E | S   | De  | Use Conditions                       | Further    |
| n | ubs | cis |                                      | I          |
| d | tit | ion |                                      | nformation |
| U | ute |     |                                      |            |
| s |     |     |                                      |            |
| e |     |     |                                      |            |
+---+-----+-----+--------------------------------------+------------+
| A | n-  | A   | 1)  The owner or operator of a       | EPA        |
| e | pro | cce |     facility must ensure that users  | recommends |
| r | pyl | pta |     of nPB achieve a workplace       | the use of |
| o | b   | ble |     exposure limit (WEL) of 17 ppm   | personal   |
| s | rom | s   |     on an 8-hour time-weighted       | protective |
| o | ide | ubj |     average.                         | equipment, |
| l | (n  | ect |                                      | including  |
| s | PB) | to  | 2)  The owner or operator of a       | chemical   |
| o | as  | use |     facility must ensure that        | goggles,   |
| l | a   | c   |     workers using nPB are monitored  | flexible   |
| v | s   | ond |     for their exposure to nPB using  | laminate   |
| e | ubs | iti |     personal breathing zone samples  | protective |
| n | tit | ons |     on an eight-hour, time-weighted  | gloves and |
| t | ute |     |     average (8-hr TWA) no later than | chemical   |
| s | for |     |     90 days after the effective date | -resistant |
|   | CF  |     |     of this rule.                    | clothing.  |
|   | C-1 |     |                                      | The        |
|   | 13, |     | 3)  If the most recent data from     | American   |
|   | H   |     |     exposure monitoring shows all    | Conference |
|   | CFC |     |     personal breathing exposures to  | of         |
|   | -14 |     |     be at or below 8.5 ppm, no       | Go         |
|   | 1b, |     |     periodic exposure monitoring is  | vernmental |
|   | and |     |     required. If the most recent     | Industrial |
|   | met |     |     data from exposure monitoring    | Hygienists |
|   | hyl |     |     shows all exposures to be at or  | recommends |
|   | c   |     |     below 17 ppm, but some above 8.5 | a          |
|   | hlo |     |     ppm, the owner or operator must  | threshold  |
|   | rof |     |     take personal breathing zone     | limit      |
|   | orm |     |     samples for nPB users at least   | value of   |
|   |     |     |     once during the next six months. | 10 ppm.    |
|   |     |     |                                      |            |
|   |     |     | 4)  The owner or operator may        | nPB, also  |
|   |     |     |     discontinue the periodic 8-hour  | known as   |
|   |     |     |     TWA monitoring for nPB users at  | 1-bro      |
|   |     |     |     the facility where at least two  | mopropane, |
|   |     |     |     consecutive sets of measurements | is Number  |
|   |     |     |     taken at least seven days apart  | 106-94-5   |
|   |     |     |     are below 8.5 ppm.               | in the CAS |
|   |     |     |                                      | Registry.  |
|   |     |     | 5)  The owner or operator must       |            |
|   |     |     |     determine the exposure of each   | Note that  |
|   |     |     |     nPB user by either taking        | the        |
|   |     |     |     personal breathing zone air      | Oc         |
|   |     |     |     samples of each user\'s exposure | cupational |
|   |     |     |     or samples that are              | Safety and |
|   |     |     |     representative of each user\'s   | Health     |
|   |     |     |     exposure. The samples are        | Admi       |
|   |     |     |     representative where the owner   | nistration |
|   |     |     |     or operator has taken one or     | (OSHA) may |
|   |     |     |     more personal breathing zone air | establish  |
|   |     |     |     samples for at least one nPB     | a final    |
|   |     |     |     user in each job classification  | P          |
|   |     |     |     in a work area during every work | ermissible |
|   |     |     |     shift, and the nPB user sampled  | Exposure   |
|   |     |     |     is expected to have the highest  | Limit      |
|   |     |     |     exposure to nPB.                 | (PEL)      |
|   |     |     |                                      | standard   |
|   |     |     | 6)  The owner or operator also must  | in the     |
|   |     |     |     perform exposure monitoring when | workplace  |
|   |     |     |     a change in workplace conditions | at 29 CFR  |
|   |     |     |     indicates that employee exposure | part 1910  |
|   |     |     |     may have increased or whenever   | under 42   |
|   |     |     |     new applications of nPB are      | U.S.C.     |
|   |     |     |     introduced. Perform exposure     | 7610(a).   |
|   |     |     |     monitoring before making planned |            |
|   |     |     |     changes, and perform monitoring  | OSHA's     |
|   |     |     |     no later than 7 days after an    | standard   |
|   |     |     |     emergency change in conditions.  | on access  |
|   |     |     |                                      | to         |
|   |     |     | 7)  All personal breathing zone      | employee   |
|   |     |     |     samples must be analyzed either  | exposure   |
|   |     |     |     by NIOSH method 1003 or 1025 or  | and        |
|   |     |     |     by another method that is        | medical    |
|   |     |     |     accurate to [+]{.underline} 25%  | records    |
|   |     |     |     at a 95 percent confidence       | requires   |
|   |     |     |     level.                           | retaining  |
|   |     |     |                                      | exposure   |
|   |     |     | 8)  The owner or operator must keep  | records    |
|   |     |     |     records of nPB worker exposure   | for at     |
|   |     |     |     data at the facility for at      | least 30   |
|   |     |     |     least three years from the date  | years (29  |
|   |     |     |     the measurements were taken.     | CFR        |
|   |     |     |                                      | 1910.102   |
|   |     |     |                                      | 0(d)(ii)). |
+---+-----+-----+--------------------------------------+------------+

Note: In accordance with the limitations provided in Section 310(a) of
the Clean Air Act (42 U.S.C. 7610(a)), nothing in this table shall
affect the Occupational Safety and Health Administrations' authority to
promulgate and enforce standards and other requirements under the
Occupational Safety and Health Act of 1970 (29 U.S.C. 651 et seq.)

Table 8. ADHESIVES, COATINGS, AND INKS

*Alternate Proposal*: SUBSTITUTES THAT ARE PROPOSED

ACCEPTABLE SUBJECT TO USE CONDITIONS

+----+-----+-----+-------------------------------------+-------------+
| E  | S   | De  | Use Conditions                      | Further     |
| nd | ubs | cis |                                     | Information |
| U  | tit | ion |                                     |             |
| se | ute |     |                                     |             |
+----+-----+-----+-------------------------------------+-------------+
| A  | n-  | A   | 1)  The owner or operator of a      | EPA         |
| dh | pro | cce |     facility must ensure that users | recommends  |
| es | pyl | pta |     of nPB achieve a workplace      | the use of  |
| iv | b   | ble |     exposure limit (WEL) of 17 ppm  | personal    |
| es | rom | s   |     on an 8-hour time-weighted      | protective  |
| a  | ide | ubj |     average.                        | equipment,  |
| nd | (n  | ect |                                     | including   |
| co | PB) | to  | 2)  The owner or operator of a      | chemical    |
| at | as  | use |     facility must ensure that       | goggles,    |
| in | a   | c   |     workers using nPB are monitored | flexible    |
| gs | s   | ond |     for their exposure to nPB using | laminate    |
|    | ubs | iti |     personal breathing zone samples | protective  |
|    | tit | ons |     on an eight-hour, time-weighted | gloves and  |
|    | ute |     |     average (8-hr TWA) no later     | chemica     |
|    | for |     |     than 90 days after the          | l-resistant |
|    | CF  |     |     effective date of this rule.    | clothing.   |
|    | C-1 |     |                                     | The         |
|    | 13, |     | 3)  If the most recent data from    | American    |
|    | H   |     |     exposure monitoring shows all   | Conference  |
|    | CFC |     |     personal breathing exposures to | of          |
|    | -14 |     |     be at or below 8.5 ppm, no      | G           |
|    | 1b, |     |     periodic exposure monitoring is | overnmental |
|    | and |     |     required. If the most recent    | Industrial  |
|    | met |     |     data from exposure monitoring   | Hygienists  |
|    | hyl |     |     shows all exposures to be at or | recommends  |
|    | c   |     |     below 17 ppm, but some above    | a threshold |
|    | hlo |     |     8.5 ppm, the owner or operator  | limit value |
|    | rof |     |     must take personal breathing    | of 10 ppm.  |
|    | orm |     |     zone samples for nPB users at   | nPB, also   |
|    |     |     |     least once during the next six  | known as    |
|    |     |     |     months.                         | 1-br        |
|    |     |     |                                     | omopropane, |
|    |     |     | 4)  The owner or operator may       | is Number   |
|    |     |     |     discontinue the periodic 8-hour | 106-94-5 in |
|    |     |     |     TWA monitoring for nPB users at | the CAS     |
|    |     |     |     the facility where at least two | Registry.   |
|    |     |     |     consecutive sets of             |             |
|    |     |     |     measurements taken at least     | Note that   |
|    |     |     |     seven days apart are below 8.5  | the         |
|    |     |     |     ppm.                            | O           |
|    |     |     |                                     | ccupational |
|    |     |     | 5)  The owner or operator must      | Safety and  |
|    |     |     |     determine the exposure of each  | Health      |
|    |     |     |     nPB user by either taking       | Adm         |
|    |     |     |     personal breathing zone air     | inistration |
|    |     |     |     samples of each user\'s         | (OSHA) may  |
|    |     |     |     exposure or samples that are    | establish a |
|    |     |     |     representative of each user\'s  | final       |
|    |     |     |     exposure. The samples are       | Permissible |
|    |     |     |     representative where the owner  | Exposure    |
|    |     |     |     or operator has taken one or    | Limit (PEL) |
|    |     |     |     more personal breathing zone    | standard in |
|    |     |     |     air samples for at least one    | the         |
|    |     |     |     nPB user in each job            | workplace   |
|    |     |     |     classification in a work area   | at 29 CFR   |
|    |     |     |     during every work shift, and    | part 1910   |
|    |     |     |     the nPB user sampled is         | under 42    |
|    |     |     |     expected to have the highest    | U.S.C.      |
|    |     |     |     exposure to nPB.                | 7610(a).    |
|    |     |     |                                     |             |
|    |     |     | 6)  The owner or operator also must | OSHA's      |
|    |     |     |     perform exposure monitoring     | standard on |
|    |     |     |     when a change in workplace      | access to   |
|    |     |     |     conditions indicates that       | employee    |
|    |     |     |     employee exposure may have      | exposure    |
|    |     |     |     increased or whenever new       | and medical |
|    |     |     |     applications of nPB are         | records     |
|    |     |     |     introduced. Perform exposure    | requires    |
|    |     |     |     monitoring before making        | retaining   |
|    |     |     |     planned changes, and perform    | exposure    |
|    |     |     |     monitoring no later than 7 days | records for |
|    |     |     |     after an emergency change in    | at least 30 |
|    |     |     |     conditions.                     | years (29   |
|    |     |     |                                     | CFR         |
|    |     |     | 7)  All personal breathing zone     | 1910.10     |
|    |     |     |     samples must be analyzed either | 20(d)(ii)). |
|    |     |     |     by NIOSH method 1003 or 1025 or |             |
|    |     |     |     by another method that is       |             |
|    |     |     |     accurate to [+]{.underline} 25% |             |
|    |     |     |     at a 95 percent confidence      |             |
|    |     |     |     level.                          |             |
|    |     |     |                                     |             |
|    |     |     | 8)  The owner or operator must keep |             |
|    |     |     |     records of nPB worker exposure  |             |
|    |     |     |     data at the facility for at     |             |
|    |     |     |     least three years from the date |             |
|    |     |     |     the measurements were taken.    |             |
+----+-----+-----+-------------------------------------+-------------+

Note: In accordance with the limitations provided in Section 310(a) of
the Clean Air Act (42 U.S.C. 7610(a)), nothing in this table shall
affect the Occupational Safety and Health Administrations' authority to
promulgate and enforce standards and other requirements under the
Occupational Safety and Health Act of 1970 (29 U.S.C. 651 et seq.)

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 have provided EPA information demonstrating their
ability to meet the recommended workplace exposure limit as of \[INSERT
DATE OF PUBLICATION\]. EPA has received a petition to allow use 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 meet the recommended
workplace exposure limit when using nPB in coatings. 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.

F.  How would the use conditions in the alternate proposal work?

At each facility where nPB is used, the following requirements would
apply under the alternate proposal:

#### Workplace Exposure Limit {#workplace-exposure-limit .unnumbered}

> The owner or operator would be required to ensure that workers using
> nPB achieve a workplace exposure limit (WEL) of 17 ppm on an 8-hour
> time-weighted average. The exposure limit could be met through
> engineering controls (e.g., ventilation equipment or additional
> cooling coils on a vapor degreaser), work practices, or reduced use of
> nPB.

#### Initial Worker Exposure Monitoring {#initial-worker-exposure-monitoring .unnumbered}

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 {#periodic-exposure-monitoring .unnumbered}

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 9. Exposure Levels and Periodic Exposure Monitoring**
>
> under the Alternate Proposal

  -----------------------------------------------------------------------
  ***If exposure measurements for ***then the owner or operator:***
  nPB are at this level:***       
  ------------------------------- ---------------------------------------
  all measurements at or below    is not required to perform periodic
  8.5 ppm                         exposure monitoring.

  all measurements at or below    must take personal breathing zone
  17.0 ppm, with some             samples again at least once in the next
  measurements above 8.5 ppm      six months.

  at least one measurement above  must stop using nPB in the application
  17.0 ppm                        exceeding the exposure limit until
                                  exposure data show the WEL can be met.

  unknown, in cases of new        must take personal breathing zone
  workplace conditions increasing samples as a test before using nPB in
  exposure or new applications of new industrial applications or
  nPB                             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 8.5 ppm.

#### Monitoring for new conditions or applications {#monitoring-for-new-conditions-or-applications .unnumbered}

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[^4]. 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, or cleaning with an open-top vapor degreaser
when previous measurements were performed on workers using enclosed,
conveyorized cleaning equipment. 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.

##### Sampling methods and accuracy {#sampling-methods-and-accuracy .unnumbered}

> 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 [+]{.underline} 25% at the 95 percent confidence level.

#### Recordkeeping requirements {#recordkeeping-requirements .unnumbered}

> 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 employer would still need to meet 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)).

**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 except for
consumer risks. 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.

The Agency evaluated the criteria set forth at 40 CFR 82.180(a)(7) in
determining whether nPB is an acceptable substitutes for methyl
chloroform, CFC-113, and HCFC-141b in metals, electronics and precision
cleaning, aerosol solvents, adhesives and coatings. The Agency has
determined that the Clean Air Act does not authorize EPA to regulate for
global climate change purposes (Fabricant, 2003). The Agency has not yet
concluded how this determination would affect its consideration of the
global warming potential (GWP) of substitutes under the SNAP program.
Regardless, the global warming potential of nPB is not a determinative
factor in EPA\'s proposed determination. The GWP for nPB is comparable
to or below that of previously approved substitutes in these end uses
(ICF, 2006a).

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 metal cleaning solvent against other available or
potentially available metal cleaning alternatives, and 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 solvent cleaning, but
not all are appropriate for a specific application because of
differences in soils, materials compatibility, degree of cleanliness
required, local environmental requirements, and other factors. For
example, aqueous cleaners are effective cleaners in many situations and
are the substitute of choice for many in the metal cleaning end use.
However, in some specific precision cleaning applications that require a
high degree of cleanliness and that have narrow spaces that may trap
water used in rinsing, aqueous cleaners may not be appropriate and thus
are not available in that specific application.

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

Other alternatives are available in each end use considered in this
proposal. Examples of other available alternatives for metals,
electronics, and precision cleaning that have already been found
acceptable or acceptable subject to use conditions under the SNAP
program include: aqueous cleaners, semi-aqueous cleaners, alcohols,
ketones, esters, ethers, terpenes, HCFC-225ca/cb, hydrofluoroethers
(HFEs), hydrofluorocarbon (HFC)-4310mee, HFC-365mfc,
heptafluorocyclopentane, hydrocarbons, volatile methyl siloxanes (VMSs),
trans-1,2-dichloroethylene, methylene chloride, trichloroethylene[^5]
(TCE), perchloroethylene[^6], parachlorobenzotrifluoride (PCBTF), and
alternative technologies like supercritical fluids, plasma cleaning, and
ultraviolet/ozone cleaning. Some alternatives are unlikely to be used in
particular end uses applications because of constraints such as cleaning
performance, materials compatibility, cost, workplace exposure
requirements, or flammability. For example, no-clean technology is used
in electronics cleaning and not in precision cleaning because of the
need for a high degree of cleanliness in precision cleaning. Of the
available substitutes, aqueous cleaners or solvents for vapor degreasing
such as TCE, blends of alcohols or trans-1,2-dichloroethylene and HFCs
or HFEs, and HCFC-225ca/cb are most likely to be used in the same
applications as nPB. nPB is already commercially available in solvent
cleaning, and is used mostly for vapor degreasing in the electronics and
precision cleaning end uses. (IBSA, 2002)

Many of the same substitutes may be used and are commercially available
in aerosol solvents: water-based formulations, alcohols, ketones,
esters, ethers, terpenes, HCFC-141b, HCFC-225ca/cb, HFEs, HFC-4310mee,
HFC-365mfc, HFC-245fa, hydrocarbons, trans-1,2-dichloroethylene,
chlorinated solvents, and 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).

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).

Based on this information, we conclude that other alternatives are
available in metals, electronics, and precision cleaning, aerosol
solvents and adhesives. Other alternatives are potentially available or
available in coatings, but other alternatives may not be potentially
available for the specific application addressed in today's proposal,
ammunition coatings.

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)[^7],
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 in metals cleaning and
aerosol solvents, and acceptable subject to use conditions in precision
cleaning and electronics cleaning. HCFC-123 has an ODP of 0.02 (WMO,
2002), and is an acceptable substitute in precision cleaning. There are
other acceptable cleaners that essentially have no ODP\--aqueous
cleaners, HFEs, HFC-4310mee, HFC-365mfc, HFC-245fa, hydrocarbons, VMSs,
methylene chloride, TCE, perchloroethylene, and PCBTF. 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). We
recognize the concern that if significant nPB usage were to occur in
equatorial regions, there could be an impact on the ozone layer.
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.

Use of nPB is controlled as a volatile organic compound (VOC) under
state and local regulations to comply with National Ambient Air Quality
Standards for ground-level ozone, which is a respiratory irritant. Users
located in ozone non-attainment 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. 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, 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 for aerosol solvents; HCFC-225ca/cb,
HFC-365mfc and HFC-4310mee for metals electronics, and precision
cleaning and aerosol solvents; and methylene chloride,
perchloroethylene, HFE-7100, HFE-7200, PCBTF, acetone, and methyl
acetate for metals, electronics, and precision cleaning, 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 11). Available data on the organic
carbon partition coefficient (K~oc~), 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 LC~50~,
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). Based on EPA's criteria for listing under
the Toxics Release Inventory, nPB would not be sufficiently toxic to
aquatic life to warrant listing, since the LC~50~ is greater than 10
mg/l (US EPA, 1992). Based on its relatively low bioconcentration factor
and log K~ow~ value, nPB is not prone to bioaccumulation. Table 10
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; and methyl
chloroform, an ODS that nPB would replace.

**Table 10. Ecosystem and Other Environmental Properties of nPB and
Other Solvents**

  -----------------------------------------------------------------------------------------------------------------------------------------
  Property            Description of    Value for nPB  Value for                     Value for acetone Value for           Value for methyl
                      environmental                    trans-1,2-dichloro-ethylene                     trichloroethylene   chloroform
                      property                                                                                             
  ------------------- ----------------- -------------- ----------------------------- ----------------- ------------------- ----------------
  K~oc~,              Degree to which a 330 (Source:   32 to 49 (Source: ATSDR,      5.4 (Source:      106 to 460 (Source: 152 (Source: US
  organic-carbon      substance tends   ICF, 2004a)    1996)                         ATSDR, 1994)      ATSDR, 1997)        EPA, 1994b)
  partition           to stick to soil                                                                                     
  coefficient         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 decomposition,     Biodegrada-tion   Volatilization and  Volatilization
                      speed with which  significant.   dechlorination and            is most           biodegradation most most
                      a compound breaks Hydrolysis     biodegradation are            significant form  significant, with   significant;
                      down in the       half-life of   significant; hydrolysis not   of breakdown      hydrolysis          biodegradation
                      environment.      26 days        significant (Source: ATSDR,   (Source: ATSDR,   relatively          and hydrolysis
                      (Hydrolysis       (Source: ICF,  1996)                         1994)             insignificant.      also occur
                      half-life values  2004a)                                                         Hydrolysis          (Source: ATSDR,
                      \> 25 weeks^\*^                                                                  half-life of 10.7   2004)
                      are of concern.)                                                                 to 30 months        
                                                                                                       (Source: ATSDR,     
                                                                                                       1997)               

  Volatilization      Tendency to       3.4 hours-4.4  3 to 6.2 hours (Source:       7.8 to 18 hours   3.4 hours to 18     hours to weeks
  half-life from      volatilize and    days (Source:  ATSDR, 1996)                  (Source: ATSDR,   days (Source:       (Source: US EPA,
  surface waters      pass from water   ICF, 2004a)                                  1994)             ATSDR, 1997)        1994b)
                      into the air.                                                                                        

  LC~50~ (96 hours)   Concentration at  67 mg/L        108 mg/L (Source: US EPA,     7280 to 8120 mg/L 40.7 to 66.8 mg/L   52.8 to 105 mg/L
  for fathead minnows which 50% of      (Source:       1980)                         (Source: Fisher   (Source: NPS, 1997) (Source: US EPA,
                      animals die from  Geiger, 1988)                                Scientific, 2001)                     1994b)
                      toxicity after                                                                                       
                      exposure for 4                                                                                       
                      days.                                                                                                

  log K~ow~           Logarithm of the  2.10 (Source:  -0.48 (Source: LaGrega et     -0.24 (Source:    2.38 (Source:       2.50 (Source:
                      octanol/water     ICF, 2004a)    al., 2001, p. 1119)           LaGrega et al.,   LaGrega et al.,     LaGrega et al.,
                      partition                                                      2001, p. 1117)    2001, p. 1127)      2001, p. 1127)
                      coefficient, a                                                                                       
                      measure of                                                                                           
                      tendency to                                                                                          
                      accumulate in                                                                                        
                      fat. Log K~ow~                                                                                       
                      values \>3^\*^                                                                                       
                      indicate high                                                                                        
                      tendency to                                                                                          
                      accumulate.                                                                                          

  Bioconcen-tration   High factors      23 (Source:    5 to 23 (Source: ATSDR, 1996) \<1 (Source:      10 to 100 (Source:  \<9 (Source: US
  factor              (\>1000)^\*^      HSDB, 2004)                                  ATSDR, 1994)      ATSDR, 1997)        EPA, 1994b)
                      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 could 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 clearly pose a 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

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, nPB
displayed no flash point (BSOC, 2000; Miller, 2003; Morford, 2003a and
2000b; Shubkin, 2003; Weiss Cohen, 2003). 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. Impact on human health

In evaluating potential human health impacts of nPB, EPA considered
impacts on both exposed workers and on the general population. Using the
same approach commented on and then 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, 1994a. RfC Guidelines; US EPA, 1991. Guidelines for
Developmental Toxicity Risk Assessment; US EPA, 1995b. Benchmark Dose
guidelines; US 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 developed a workplace exposure limit (WEL)
(also known as an acceptable exposure limit \[AEL\]) 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 WEL and CEG to available exposure data and
projections of exposure levels to assess exposure. 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.

1\. Occupational health risks

EPA found that where an 8-hour average workplace exposure level for nPB
of 17 ppm or lower can be maintained, it can be used as safely as other
acceptable solvents at the levels of their occupational exposure limits,
such as Occupational Safety and Health Administration (OSHA) Permissible
Exposure Limits (PELs) or the American Conference of Industrial
Hygienists (ACGIH) Threshold Limit Values™ (TLVs).[^8] However, EPA
found that the ability to meet the recommended nPB workplace exposure
limit (WEL) of 17 ppm (8-hour time weighted average \[TWA\]) varies,
depending on equipment used and the end use. In some uses, users clearly
can meet the WEL (metals, electronics and precision cleaning), while in
other end uses, users may not be able to meet the WEL following current
industry practices (adhesives and aerosols). We discuss the ability to
meet the nPB WEL in each end use below in section VI.

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 ACGIH
provides no skin notation in its TLV documentation for several solvents,
including nPB, methylene chloride, and perchloroethylene, and there is
no evidence that absorption through the skin is greater for nPB than for
the other halogenated compounds. 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 also considered the potential health effects of contamination of nPB
formulations with isopropyl bromide (iPB).[^9] In the June 2003 proposed
rule, we proposed as a use condition that nPB formulations contain no
more than 0.05% iPB by weight. Industry has met this contamination limit
for several years without regulation. Furthermore, EPA believes that if
users are meeting the recommended workplace exposure limit for nPB of 17
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.

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.B below) and determined that community exposures were likely
to be higher for nPB used in adhesives than for nPB used in aerosol
solvents or in metals cleaning, electronics cleaning, or precision
cleaning. EPA modeled inhalation exposure to nPB to people living near a
plant using nPB-based adhesives in several scenarios using the Agency's
SCREEN3 model and 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).

**V. How did EPA derive the proposed workplace exposure limit and
community exposure guideline used to assess impacts on human health?**

This proposal evaluates human health risks using a workplace exposure
limit (WEL) to assess occupational exposure to nPB and a community
exposure guideline (CEG) to assess the general public's exposure to nPB.
EPA proposes to use a WEL of 17 ppm averaged over 8 hours and a CEG of 1
ppm averaged over 24 hours. The derivation of these values is described
below in sections V.A and V.B, respectively. To assess human health
risks in each end use, EPA then compared the WEL to measured and
projected occupational exposures, and the CEG to projections of exposure
to the general public.

> A. Workplace exposure limit

OSHA has not developed a permissible exposure limit (PEL) for nPB that
EPA could use to evaluate toxicity risks from workplace exposure. The
American Conference of Governmental Industrial Hygienists (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. Further, there is a wide
range of exposure limits recommended by nPB vendors (from 5 ppm to 100
ppm). After considering all of the various exposure limits recommended
by industry and governmental organizations, and individual companies and
consultants, and a thorough review of all available data, EPA has
developed a recommended WEL of 17 ppm averaged over eight hours to
assess human health risks and to evaluate the acceptability of nPB in
potential use sectors.

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, and we derived the
recommended exposure limit in the June 2003 NPRM 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 Research Laboratories, 2001). For this proposed rule, we
reviewed both new information and the previously available information
on health effects in developing an exposure limit.

1\. Newly Available Data on Health Effects

Since publication of the June 2003 NPRM, EPA has examined additional
occupational (Table 11) and animal (Table 12) studies that have become
available:

**Table 11**. Recent Studies on nPB Occupational Exposure

  ----------------------------------------------------------------------------------------------
  **Case       **Sample            **Exposure       **Observations**       **Remarks**
  Study**      Size/Population**   Data**                                  
  ------------ ------------------- ---------------- ---------------------- ---------------------
  Beck and     6 foam cushion      Exposure during  Lower leg weakness     Small sample size
  Caravati,    factory workers     30-40 hr/wk for  accompanied by pain    studied. Possible
  2003         (gluers)            a 3-month        and difficulty with    interference or
                                   period. Exposure standing and walking,  synergistic effects
                                   measured in one  numbness of legs and   from other adhesive
                                   day was a mean   feet, hyperreflexia    ingredients
                                   of 130 ppm       and hypertonicity of   (1,2-epoxybutane and
                                   (range, 91-176   lower extremities,     styrene-butadiene).
                                   ppm).            dizziness and          
                                                    shortness of breath,   
                                                    and peripheral         
                                                    neurotoxicity.         
                                                    Measured serum bromide 
                                                    levels were elevated,  
                                                    range 44-170 mg/dL.    

  Majersik et  6 foam cushion      5-8 hr/day for   Subacute onset of      Follow-up to Beck and
  al., 2004;   factory workers     at least 2 years lower extremity pain,  Caravati (2003).
  Majersik et  (gluers)            with mean air    difficulty walking,    Chronic nPB exposure
  al., 2005 \*                     concentration of and high serum bromide associated with
                                   130 ppm on last  levels in blood.       incapacitating
                                   day of study.    Neurotoxic symptoms    neurotoxic syndrome.
                                   Measurements     persisted for at least Initial report from
                                   taken over 9     2 years after exposure Utah OSHA indicated
                                   hours            ended.                 erroneously that
                                   (equivalent to                          workers were not
                                   92-127 ppm with                         spraying while
                                   mean of 108 ppm                         measurements were
                                   for an 8-hour                           taken. In fact,
                                   TWA).                                   adhesives were being
                                                                           sprayed and
                                                                           ventilation equipment
                                                                           was not being used,
                                                                           making measurements
                                                                           likely to be
                                                                           representative of
                                                                           conditions during the
                                                                           past several months
                                                                           at the plant.

  Ichihara et  37 chemical plant   12 hour shifts   Mucosal irritation     Inadequate exposure
  al., 2004a   workers (24 males   over 2-day       (nose, throat),        characterization and
               and 13 females)     period, mean     headache, dizziness,   exposure to other
                                   concentration of constipation,          potential toxicants,
                                   82 ppm (range,   intoxication, and      small sample size,
                                   0-170 ppm)       feeling light-headed   and no appropriate
                                                    or heavy-headed. Four  control group.
                                                    female workers         Healthy worker effect
                                                    complained of          possible, where more
                                                    disruption or          sensitive workers
                                                    cessation of           left the factory
                                                    menstruation. No       between 1996 and
                                                    severe chronic         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  27 female chemical  1-day exposure   Responses indicated    No long-term exposure
  al., 2004b   plant workers (23   period, range of anxiety, fatigue,      measurements, small
               age matched with 23 exposure,        confusion, tension,    sample size; lack of
               females from a beer 0.34-49 ppm      and depression.        controls for age,
               factory control                      Changes in menstrual   height, and
               group)                               status but not         body-weight. Low B
                                                    statistically          vitamin levels in
                                                    significant. Effects   normal range in some
                                                    on peripheral and      workers but
                                                    central nervous system researchers concluded
                                                    ---diminished          this did not cause
                                                    vibration sensation of observed neurological
                                                    the foot;              effects.
                                                    significantly longer   Additionally, the
                                                    distal latency in the  study did not
                                                    tibial nerve;          indicate any
                                                    decreased values in    significant
                                                    sensory nerve          differences in the
                                                    conduction velocity in prevalence of
                                                    the sural nerve; and   menstrual cycle
                                                    lower scores on memory abnormalities.
                                                    and perceptual tests.  
                                                    No comparable effects  
                                                    seen in control group. 

  Nemhauser,   Foam cushion        In 1999 study,   Higher exposure to nPB Small sample sizes
  2005 \*      factory workers     16 workers       and dose-dependent     studied with moderate
               (gluers) in North   exposed to mean  relationship among     worker participation.
               Carolina            air              those who reported     Healthy worker effect
                                   concentration of anxiety, headache, and likely occurred:
                                   116 ppm, and 12  ataxia. No             those that had most
                                   sprayers exposed reproductive           significant health
                                   to mean          abnormalities reported effects had already
                                   concentration of in medical survey for  removed themselves
                                   108 ppm with     men or women. Semen    from workplace by the
                                   range of 58 to   analysis found no      time of the study. No
                                   254 ppm. In 2001 differences between    arsenic found at the
                                   study, 13        exposed and unexposed  plant. Neurotoxic
                                   workers exposed  workers.               effects caused by
                                   to nPB mean air                         nPB. See related
                                   concentration of                        Health Hazard
                                   46 ppm and 12                           Evaluation (HHE):
                                   sprayers were                           NIOSH, 2003a.
                                   exposed to mean                         
                                   concentration of                        
                                   101 ppm, with                           
                                   range of 38 to                          
                                   281 ppm.                                

  NIOSH, 2003a 16 workers in 1999  1999 Initial     Most workers exposed   Arsenic was not
               evaluation; 13      Site Visit:      to \>25 ppm nPB        attributed to
               workers in 2001     geometric mean   levels. Exposure       occupational
               follow-up           nPB              concentrations lower   exposure. The
               evaluation.         concentration    in 2001 than 1999, but National Institute
                                   (from personal   difference not         for Occupational
                                   samples), 81.2   statistically          Safety and Health
                                   (range, 18-254   significant. Headache, (NIOSH) stated that
                                   ppm); 2001       anxiety, feeling drunk neurological symptoms
                                   follow-up:       associated with nPB    may have been related
                                   geometric mean,  exposure.              to excess exposure to
                                   81.2 ppm (range, Hematological          nPB, but that no
                                   7-281 ppm)       endpoints unaffected   other effects could
                                                    in exposed group. No   conclusively be
                                                    correlation of nPB     related to nPB
                                                    exposure with sperm or exposure.
                                                    semen indices or with  
                                                    neurological           
                                                    abnormalities.         

  Raymond and  4 foam cushion      Exposure study   Dizziness, numbness,   Small sample size,
  Ford, 2005\* factory workers     conducted 9      ocular symptoms, lower possible confounding
               (gluers) in North   months after     extremity weakness and effect from arsenic.
               Carolina            index patient    unsteady gait,         
                                   became ill       weakness, hypesthesia, 
                                   indicated        and ataxic gait in all 
                                   workers exposed  four workers. Symptoms 
                                   to mean nPB air  decreased over time    
                                   concentration of but after six years,   
                                   116 ppm. 4       at least one worker    
                                   workers exposed  re-exposed twice at    
                                   for 2-3 weeks    other furniture        
                                   before initial   plants; one or more    
                                   symptoms         still suffer from      
                                   detected.        ataxia.                

  Toraason et   41 and 22 foam     1-3 days up to 8 No statistically       Authors find limited
  al., 2006    cushion factory     hrs per day,     significant            evidence that nPB
               workers (gluers) at with             differences in DNA     poses a "small risk"
               2 facilities        concentrations   damage with worker's   for DNA damage.
                                   of  0.2 -- 271   nPB exposure. In vitro 
                                   ppm at facility  results showed nPB     
                                   A, 4 - 27 ppm at increased DNA damage.  
                                   facility B.                             
  ----------------------------------------------------------------------------------------------

\*Presentation at North American Congress of Clinical Toxicology on
September 14, 2005.

**Table 12. Recent Animal Studies of nPB Effects**

+-----+-------+-----------+------------------+-----------------------+
| **C | **Pop | **E       | **Observations** | **Comments**          |
| ita | ulati | xposure** |                  |                       |
| tio | on/** |           |                  |                       |
| n** |       |           |                  |                       |
|     | **s   |           |                  |                       |
|     | ample |           |                  |                       |
|     | s     |           |                  |                       |
|     | ize** |           |                  |                       |
+=====+=======+===========+==================+=======================+
| Fu  | 24    | 6 hr/day, | No apparent      | Only one exposure     |
| eta | male  | 5 day/wk  | morphological    | concentration was     |
| et  | W     | for 8     | defects in the   | used (which is higher |
| a   | istar | weeks at  | brain.           | than the level        |
| l., | rats  | 700 ppm   |                  | already associated    |
| 2   | (12   |           |                  | with other toxic      |
| 002 | con   |           |                  | effects in rodents    |
|     | trol, |           |                  | \[400 ppm\]) and a    |
|     | 12    |           |                  | shorter exposure      |
|     | exp   |           |                  | duration (8 weeks)    |
|     | osed) |           |                  | was used than the     |
|     |       |           |                  | other subchronic      |
|     |       |           |                  | studies that have     |
|     |       |           |                  | shown effects (13     |
|     |       |           |                  | weeks).               |
+-----+-------+-----------+------------------+-----------------------+
| Fu  | 58    | 6 hr/day, | No apparent      | Unclear how nPB       |
| eta | male  | 5 day/wk  | morphological    | and/or its            |
| et  | W     | for 4 to  | defects in the   | metabolites directly  |
| a   | istar | 8 weeks,, | brain. Chronic   | act on receptors or   |
| l., | rats  | 700 ppm   | inhalation       | channels in the       |
| 2   | (29   |           | changes brain    | brain.                |
| 004 | ex    |           | enzyme levels    |                       |
|     | perim |           | and electrical   |                       |
|     | ental |           | activity that is |                       |
|     | and   |           | reversible after |                       |
|     | 29 in |           | exposure.        |                       |
|     | co    |           |                  |                       |
|     | ntrol |           |                  |                       |
|     | g     |           |                  |                       |
|     | roup) |           |                  |                       |
+-----+-------+-----------+------------------+-----------------------+
|     |       |           |                  |                       |
+-----+-------+-----------+------------------+-----------------------+
| Ho  | F     | 8 hr/day, | 3 week exposure  | Neurological effects  |
| nma | isher | 7day/wk   | to greater than  | shown to be transient |
| et  | 344   | for three | 50 ppm           | and reversible at ≥   |
| a   | male  | weeks     | temporarily      | 200 ppm (Ichihara et  |
| l., | rats  | exposed   | increased        | al., 2000) or absent  |
| 2   |       | to 0, 10, | locomotor        | after 28 days of      |
| 003 |       | 50, 200   | activity and     | exposure at           |
|     |       | or 1000   | ambulatory and   | concentrations ≥ 400  |
|     |       | ppm (5    | rearing          | ppm (ClinTrials,      |
|     |       | ra        | behaviors in     | 1997a) or after 90    |
|     |       | ts/dosage | male rats.       | days of exposure at   |
|     |       | and 5     |                  | concentrations up to  |
|     |       | different |                  | 600 ppm (ClinTrials,  |
|     |       | tests)    |                  | 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 a WEL.             |
+-----+-------+-----------+------------------+-----------------------+
| I   | 30    | 6 hr/day, | nPB is           | Exposure levels are   |
| shi | male  | 5 day/wk  | metabolized      | higher than in some   |
| dao | W     | with test | rapidly in the   | other studies and are |
| et  | istar | groups    | rat following    | much higher than      |
| a   | rats  | (10/dose) | exposures to nPB | concentrations seen   |
| l., |       | exposed   | at               | in the workplace. nPB |
| 2   |       | to 700    | concentrations ≥ | metabolism appears to |
| 002 |       | ppm for 4 | 700 ppm for at   | be different          |
|     |       | and 12    | least 3 weeks.   | following multiple    |
|     |       | weeks and |                  | exposures as compared |
|     |       | 1500 ppm  |                  | to acute exposures    |
|     |       | for 3 and |                  | (see RTI, 2005; ICF,  |
|     |       | 4 weeks   |                  | 2006b).               |
+-----+-------+-----------+------------------+-----------------------+
| N   | F     | 0, 62.5,  | Early mortality  | Unpublished study.    |
| TP, | emale | 125, 250, | in mice at 500   | Conclusions drawn     |
| 2   | and   | 500 (rats | ppm accompanied  | from a review of raw  |
| 003 | male  | and       | by liver and     | data from the         |
|     | B     | mice),    | lung cell        | National Toxicology   |
|     | 6C3F1 | 1000      | degeneration and | Program (NTP) web     |
|     | mice  | (rats)    | cytoplasmic      | site. In general, the |
|     | and   | ppm for   | vacuolization.   | severity of effects   |
|     | Fi    | 90 days   | Cytoplasmic      | (in non-reproductive  |
|     | scher |           | vacuolization    | organs) is slightly   |
|     | 344   |           | also in rat      | higher at lower       |
|     | rats  |           | liver cells ≥    | concentrations in     |
|     |       |           | 250 ppm (males)  | male rats than in     |
|     |       |           | and ≥ 500 ppm    | females.              |
|     |       |           | (females), with  |                       |
|     |       |           | increased        |                       |
|     |       |           | severity at      |                       |
|     |       |           | higher doses. No |                       |
|     |       |           | adverse central  |                       |
|     |       |           | nervous system   |                       |
|     |       |           | (CNS) effects or |                       |
|     |       |           | histopathology   |                       |
|     |       |           | reported.        |                       |
+-----+-------+-----------+------------------+-----------------------+
| R   | F     | Exposure  | nPB cleared by   | RTI concluded that:   |
| TI, | emale | via       | mice after 48    |                       |
| 2   | and   | several   | hours as         | -   nPB administered  |
| 005 | male  | injection | follows: 45% as  |     via               |
|     | B6C3F | routes    | volatiles in the |     intraperitoneal   |
|     | 1mice | (intrape  | breath, 28% as   |     injection or      |
|     | and   | ritoneal, | CO~2~ in the     |     inhalation is     |
|     | F     | int       | breath, 26% in   |     eliminated mostly |
|     | isher | ravenous, | urine, \<3% in   |     through the       |
|     | 344N  | cannuli   | feces, and 2%    |     breath, with      |
|     | rats, | z-ation), | retained in the  |     urine as a        |
|     | four  | in        | body.            |     secondary path.   |
|     | to    | halation, | Distribution was |                       |
|     | six   | and       | similar in male  | -   Metabolism of nPB |
|     | an    | dermal.   | rats, although   |     appears to be     |
|     | imals | Injection | amounts in urine |     primarily through |
|     | in    | conducted | and volatiles in |     cytochrome P450   |
|     | each  | via bolus | breath were      |     enzymes (CYP2E1), |
|     | test  | dosing at | higher in mice.  |     particularly in   |
|     | trial | 5, 20, or | At higher doses, |     mice; glutathione |
|     |       | 100 mg/kg | the amount of    |     conjugation still |
|     |       | body      | nPB excreted in  |     plays an          |
|     |       | weight.   | urine and as     |     important role in |
|     |       | I         | CO~2~ decreased, |     rats.             |
|     |       | nhalation | with a much      |                       |
|     |       | conce     | greater change   | -   At high           |
|     |       | ntrations | in rats compared |     concentrations,   |
|     |       | of 70,    | to mice.         |     female rats may   |
|     |       | 240, 800, |                  |     have a decreased  |
|     |       | and 2700  | -   After        |     capacity to       |
|     |       | ppm       |     pretreatment |     metabolize nPB    |
|     |       | adm       |     with a       |     compared to male  |
|     |       | inistered |     cytochrome   |     rats.             |
|     |       | in a      |     P450         |                       |
|     |       | single    |     inhibitor, a | -   nPB decreases     |
|     |       | acute     |     decrease in  |     glutathione       |
|     |       | exposure. |     nPB cleared  |     levels in the     |
|     |       | A dose of |     as CO~2~     |     liver after a     |
|     |       | 96 mg/kg  |     (80%) and    |     one-time exposure |
|     |       | was       |     urine (40%); |     to nPB at         |
|     |       | applied   |     pretreatment |     concentrations as |
|     |       | to a      |     with a       |     low as 70 ppm.    |
|     |       | shaved    |     glutathione  |                       |
|     |       | area on   |     inhibitor    | -   nPB is not        |
|     |       | the backs |     reduced nPB  |     appreciably       |
|     |       | of six    |     cleared as   |     absorbed          |
|     |       | male rats |     CO~2~ by 10% |     (\~3-27%) in rats |
|     |       | with a    |     and urine by |     following dermal  |
|     |       | non-      |     4%.          |     application.      |
|     |       | occlusive |                  |                       |
|     |       | charcoal  | -   The Vmax, a  | EPA agrees with these |
|     |       | filter    |     measure of   | points, except we     |
|     |       | covering  |     the maximum  | found that gender     |
|     |       | (that is, |     initial rate | differences were only |
|     |       | one that  |     of an        | apparent in rats at   |
|     |       | does not  |                  | very high             |
|     |       | prevent   | enzyme-catalysed | concentrations (2700  |
|     |       | evap      |     reaction, is | ppm and greater). We  |
|     |       | oration). |     0.227 for    | also note that:       |
|     |       |           |     male rats,   |                       |
|     |       |           |     0.143 for    | -   Inhalation tests  |
|     |       |           |     female rats, |     were only         |
|     |       |           |     0.329 for    |     one-time          |
|     |       |           |     male mice    |     exposures at very |
|     |       |           |     and 0.234    |     high              |
|     |       |           |     for female   |     concentrations    |
|     |       |           |     mice.        |     (240 to 2700      |
|     |       |           |     Half-lives   |     ppm), and thus,   |
|     |       |           |     were         |     are not           |
|     |       |           |     comparable   |     comparable to     |
|     |       |           |     between      |     long-term dosing  |
|     |       |           |     males and    |     at the lower      |
|     |       |           |     females at ≤ |     levels expected   |
|     |       |           |     800 ppm.     |     in the workplace. |
|     |       |           |                  |                       |
|     |       |           | -   For rats     | -   Results of dermal |
|     |       |           |     exposed to   |     testing are not   |
|     |       |           |     nPB through  |     conclusive        |
|     |       |           |     skin, 37% of |     because of        |
|     |       |           |     the dose was |     potential for     |
|     |       |           |     excreted in  |     inhalation        |
|     |       |           |     volatiles,   |     exposure.         |
|     |       |           |     1.2 % in     |                       |
|     |       |           |     urine, 1.7%  |                       |
|     |       |           |     as CO~2,~    |                       |
|     |       |           |     and 35.7%    |                       |
|     |       |           |     was on the   |                       |
|     |       |           |     applicators  |                       |
|     |       |           |     or in the    |                       |
|     |       |           |     skin washes. |                       |
|     |       |           |     Only 0.32%   |                       |
|     |       |           |     remained in  |                       |
|     |       |           |     tissues.     |                       |
|     |       |           |     Airborne     |                       |
|     |       |           |                  |                       |
|     |       |           |   concentrations |                       |
|     |       |           |     of nPB in    |                       |
|     |       |           |     the chamber  |                       |
|     |       |           |     were 4 to 10 |                       |
|     |       |           |     ppm after    |                       |
|     |       |           |     dosing.      |                       |
+-----+-------+-----------+------------------+-----------------------+
| S   | 40    | 6 hr/day, | No effects on    | The differences       |
| ohn | male  | 5 day/wk  | mortality,       | between the various   |
| et  | and   | for 13    | activity, weight | studies may be due to |
| a   | 40    | weeks,    | gain, food       | variability in        |
| l., | f     | test      | consumption,     | exposure methodology  |
| 2   | emale | groups    | urinalysis, or   | and achieved          |
| 002 | Spra  | (10/      | histological     | concentrations of     |
|     | gue-D | sex/dose) | effects in the   | nPB.                  |
|     | awley | were      | brains and       |                       |
|     | rats  | exposed   | spinal cords.    |                       |
|     |       | to 0,     |                  |                       |
|     |       | 200, 500  |                  |                       |
|     |       | or 1250   |                  |                       |
|     |       | ppm       |                  |                       |
+-----+-------+-----------+------------------+-----------------------+
| Stu | 125   | Both test | Decreased litter | Reproductive effects  |
| mp, | femal | groups of | size at 250 and  | seen in both rat      |
| 200 | e/125 | 25 male   | 500 ppm in both  | sexes which is a      |
| 5\* | male  | rats/ 25  | generations.     | strong signal of      |
|     | rats  | female    | Decreased        | reproductive toxicity |
|     | in    | rats      | fertility at 100 | potential in humans.  |
|     | first | exposed   | and 250 ppm in   | The author considers  |
|     | gener | to 0,     | offspring        | 100 ppm to be a       |
|     | ation | 100, 200, | generation.\     | lowest observed       |
|     | and   | 250, 500  | Complete         | adverse effect level  |
|     | 100   | and 750   | infertility at   | (LOAEL). This is a    |
|     | femal | ppm nPB   | 750 ppm.         | presentation of data  |
|     | e/100 | for 10    |                  | from WIL, 2001.       |
|     | male  | weeks     |                  |                       |
|     | rats  |           |                  |                       |
|     | in    |           |                  |                       |
|     | offs  |           |                  |                       |
|     | pring |           |                  |                       |
|     | gener |           |                  |                       |
|     | ation |           |                  |                       |
+-----+-------+-----------+------------------+-----------------------+
| W   | 36    | 8 hr/day, | Decrease in      | Small study size. No  |
| ang | male  | 5 day/wk  | creatine kinase  | behavioral changes or |
| et  | W     | for 12    | in the spinal    | physical symptoms     |
| a   | istar | weeks,    | cord (17% at ≥   | were observed in the  |
| l., | rats  | test      | 200 ppm) and     | animals, so the       |
| 2   |       | groups (  | brain (15-28% at | toxicological         |
| 003 |       | 9 rats)   | ≥ 400 ppm) at    | relevance of the      |
|     |       | were      | 200, 400, and    | decrease in creatine  |
|     |       | exposed   | 800 ppm. No      | kinase is             |
|     |       | to 0,     | physical or      | questionable.         |
|     |       | 200, 400  | behavioral       |                       |
|     |       | or 800    | changes          |                       |
|     |       | ppm       | observed.        |                       |
+-----+-------+-----------+------------------+-----------------------+
| Yam | 40    | 8 hr/day, | All rats at 800  | Data suggest that nPB |
| ada | f     | 7 day/wk  | ppm became       | is affecting the      |
| et  | emale | with test | seriously ill    | maturation of ovarian |
| a   | W     | groups    | after 7 weeks of | follicles. A no       |
| l., | istar | (9/dose)  | exposure.        | observed adverse      |
| 2   | rats  | exposed   | Significant      | effect level (NOAEL)  |
| 003 |       | to 0,     | decrease in      | of 200 ppm is         |
|     |       | 200, 400, | antral follicles | identified with a     |
|     |       | or 800    | at ≥ 200 ppm,    | LOAEL of 400 ppm for  |
|     |       | ppm for   | and a decrease   | the changes in estrus |
|     |       | 12 weeks  | in the number of | cycles.               |
|     |       |           | female rats      |                       |
|     |       |           | exhibiting       |                       |
|     |       |           | regular 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

Data collected from actual occupational settings indicate that severe,
possibly irreversible, neurological effects may occur at sustained
concentrations of approximately 100 ppm or greater, with variability in
effects observed in different studies, although in most cases exposures
may have been much higher. For example, in Ichihara et al. (2002a),
doctors performed a health assessment first, and then the exposure
assessment was performed later (Miller, 2005); therefore, the exposure
concentrations measured may not accurately represent the concentrations
that may have induced the observed adverse effects. Because of design
and methodological limitations, such as small numbers of subjects and
limited exposure information, none of these recent studies individually
provide a sufficient quantitative basis to derive a WEL.

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 CNS toxicity in the NTP (2003) study and the Sohn
(2002) study on rats.) In particular, Yamada et al. (2003) reported
estrous cycle[^10] irregularities that Sekiguchi (2002) also noted after
a short-duration exposure, and these effects also were reported in a
multi-generation study (WIL, 2001) in which an increase in estrous cycle
length was observed in animals exposed to nPB at levels of 250-750
ppm.[^11] The expert panel for the Center for the Evaluation of Risks to
Human Reproduction (CERHR, 2002a) concluded, based on the WIL (2001)
findings, that the lowest observed adverse effect level (LOAEL) for
female reproductive effects is 250 ppm and the no observed adverse
effect level (NOAEL) is 100 ppm. However, neither the authors of the WIL
(2001) study nor the expert panel of the CERHR statistically evaluated
the estrous cycle data. At the time of the June 2003 proposal, EPA
stated that while the increase in estrous cycle length in the WIL study
may be a result of nPB exposure, "the effect cannot be conclusively
attributed to exposure without statistical analysis" and because of the
lack of statistically-analyzed data, "this endpoint should not be used
for developing the AEL." (68 FR 33296)

After further reviewing the Yamada et al. (2003) study, published just
prior to the 2003 NPRM, EPA 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). We focused on the WIL study because of the following strengths
described in the June 2003 NPRM: (1) it was conducted in accord with
Good Laboratory Practice procedures and standard test guidelines over
multiple generations; (2) it underwent an independent audit; (3) it
contained a sufficiently large sample size; and (4) the raw data were
provided for detailed statistical analyses.

In WIL (2001), an increase in estrous cycle length was observed in each
exposure group relative to controls prior to mating, and statistically
significant decreases in the number of estrous cycles were observed at
[\>]{.underline}250 ppm in females of the "F0" (parental) generation,
and at 500 ppm in the offspring. In this study, both of these changes
were early biomarkers of reproductive success as the nature and
magnitude of reproductive toxicity increased with increasing dose. For
example, at 500 ppm, females were not having their estrous cycle and
more than half were unable to deliver offspring after mating; all
females exposed to 750 ppm failed to reproduce.

As discussed by ICF (2004b), three external expert reviewers agreed that
the finding of a statistically significant decrease in the number of
estrous cycles and increase in estrous cycle length was a
toxicologically significant finding, particularly when considered
together with other reproductive endpoints (ICF, 2004b). The reviewers
further noted that: (1) there are significant similarities between the
female reproductive systems of humans and rodents; (2) effects on the
ovarian cycle are associated with reduced fertility in both humans and
rats; and (3) changes in estrous cycles in rats have potential human
relevance. EPA Guidelines for Reproductive Risk Assessment (US EPA,
1996) state that "significant evidence that the estrous cycle (or
menstrual cycle in primates) has been disrupted should be considered an
adverse event. Included should be evidence of abnormal cycle length or
pattern, ovulation failure, or abnormal menstruation."

Given the clear relationship between decreasing number of estrous cycles
with increasing dose in WIL (2001), consistent with Yamada et al. (2003)
and with other effects on the female reproductive system, ICF (2005a)
conducted benchmark dose analyses[^12] on the number of estrous cycles
during the 3-week period prior to mating, following 7 weeks of nPB
exposure.[^13] The statistical model that provided the best fit to the
dose-response data yielded a lower-bound benchmark dose level (BMDL) of
162 ppm (ICF, 2006a, Att. A).

This BMDL results in a lower WEL than that calculated using the points
of departure based on other endpoints, such as liver effects, or effects
on the nervous system. We note that there are a variety of reproductive
health effects with BMDLs in the range from 160 to 210 ppm, including:

-   Number of estrous cycles during a 3-week period (F0 generation) at
    162 ppm (ICF, 2006a)

-   Sperm motility (F1 offspring generation) at 169 ppm (ICF, 2002a)

-   Decreased live litter size at 170 ppm (F2 offspring generation) and
    190 ppm (F1 offspring generation) (TERA, 2004; Stelljes and Wood,
    2004)

-   No estrous cycle incidence (F1 offspring generation) at 180 ppm
    (TERA, 2004)

-   Change in prostate weight (F0 parental generation) at 190 ppm (TERA,
    2004)

-   Estrous cycle length (F0 parental generation) at 210 ppm (TERA,
    2004)

These 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., 2000 and Yamada, 2003. Of these
effects, the one occurring at the lowest level, and thus protecting
against all adverse health effects, is the number of estrous cycles
during a 3-week period. Consistent with Agency guidance (US EPA, 1994a),
EPA is using 162 ppm as a "point of departure" to derive the WEL.

> 2\. Derivation of WEL

To calculate the WEL for nPB, EPA uses standard risk assessment methods
delineated in Agency guidance (US EPA, 1994a) 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:

*(162 ppm x 6 hours/8 hours) x 7 days/5days = 170 ppm*

*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 (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
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 other uncertainty
factors). By EPA RfC guidelines (EPA, 1994a), 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.

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 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 (Werner, 2003; Risotto, 2003). Recent studies
provide additional data regarding metabolism of nPB in rats and mice
(RTI, 2005), but data on human metabolism are still lacking.

Despite the difference in metabolic pathways for nPB in mice and rats
(RTI, 2005), no significant species-specific differences in toxicity
exist between rats and mice at inhaled concentrations \<500 ppm for 13
weeks (NTP, 2003; ICF, 2006c). 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 recommended WEL, 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
(UF) 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 (EPA, 1994a). Recently published data on humans and
rodents do not decrease the uncertainty regarding the pharmacodynamics
of nPB; therefore, modification of the UF of 3 for differences between
species is not justified.

EPA is also applying an uncertainty factor of 3 to protect for sensitive
subpopulations and variability in the working population. There are
preexisting reproductive conditions as well as significant variability
in fertility among otherwise healthy women. For example, in a study of
782 couples, Dunson et al. (2002) found that fertility was twice as high
for women ages 19 to 26 years compared to women ages 35 to 39 years, and
that factors other than age (e.g., smoking, sexually transmitted
diseases, occupational exposure) accounted for a three-fold difference
in fertility rates. Since similar sources of variability would be
expected among individuals in the workplace, variability in reproductive
capacity of workers of more than 2-fold and less than 10-fold based on
the finding of Dunson et al. (2002) might be expected. EPA's RfC
guidelines recommend an uncertainty factor of 10 to account for
intraspecies variability within the general population. However, in
developing a WEL, EPA's focus is on worker exposure, which excludes some
particularly vulnerable populations, such as children, most adolescents,
and the elderly. 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.

The uncertainty factors of 3 for animal-human extrapolation and 3 for
variability within the human working population (each representing half
an order of magnitude) yield a composite uncertainty factor of 10. When
the human equivalent concentration of 170 ppm derived above is divided
by a total uncertainty factor of 10, the proposed WEL of 17 ppm results.
This is higher than the value (i.e., 10 ppm) that would have been
obtained had EPA used the NOAEL of 100 ppm for either male or female
reproductive effects in the WIL (2001) study as the point of departure.
This also is higher than 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.
Further, if EPA had used one of the other reproductive endpoints, such
as sperm motility or live litter size, we would have calculated a WEL in
the range of 18 to 22 ppm.

3\. Other Recent Analyses of nPB Toxicity

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. Rozman and Doull,
2005 derived a WEL of 25 ppm for nPB based on neurotoxicity, using more
recent information than Rozman and Doull, 2002.

EPA reviewed Rodricks (2002) in developing its June 2003 NPRM, although
the study was not explicitly mentioned in that preamble. Rodricks (2002)
suggests a WEL of 60 to 88 ppm for nPB, based on male reproductive
effects. The Stelljes and Wood (2004) analysis is similar in its results
to SLR International (2001), a study by the same authors. EPA previously
reviewed both these studies in developing the June 2003 NPRM. Both
studies concluded with a recommended WEL of 156 ppm, based on male
reproductive effects. 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 WEL from one
of these documents would result in a higher, less protective WEL than we
would determine following the approach EPA has used for other chemicals
under the SNAP program and would ignore significant sources of
uncertainty in health effects. In addition, based on our most recent
examination of the health effects of nPB, these documents do not select
the most sensitive endpoint to protect against female reproductive
effects, effects on live litter size, and other adverse health effects.
Thus, we are concerned that the WELs based on these documents are not
sufficiently protective and would result in an inappropriate
acceptability decision. Detailed reviews of these documents are
available in the public docket.

TERA, 2004 reviews other WEL derivations for nPB, performs a benchmark
dose analysis, and recommends a WEL of 20 ppm based on live litter size.
This document is consistent with EPA guidance for benchmark dose
modeling and for assigning uncertainty factors. A review of this
document is available in the public docket.

The California Environmental Protection Agency's Office of Environmental
Exposure and 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 Value™ (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 hepatoxicity (ClinTrials, 1997b)
and less than 100 ppm for developmental toxicity, as evidenced by
decreased fetal weight (Huntingdon Life Sciences, 2001).

In prior SNAP reviews, EPA has used ACGIH TLVs where available in
assessing a chemical's risks and determining its acceptability. 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 has significant
limitations as a reliable basis for a workplace 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 any 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 sperm effects
and estrous cycle changes; and (3) ACGIH may not have reviewed the
complete body of literature as several studies discussing neurotoxicity
and changes in estrous cycle length were omitted from the list of
references. A review of this document is available in the public docket.

B. 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.

EPA calculated the community exposure guideline using increased estrous
cycle length as the point of departure, the BMDL of 162 ppm for a
reduced number of estrous cycles during a three-week period, and an HEC
of 40 ppm as follows:

*162 ppm x (6 hours exposure in study/24 hours avg time) x (7 days/7
days) = 40 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 40 ppm by 30 yields a community
exposure guideline of approximately 1 ppm, the same as the value
calculated using liver effects or sperm motility as an endpoint.

EPA evaluated general population exposure using EPA's SCREEN3 (US EPA,
1995a) air dispersion model to assess the likely maximum concentration
of nPB from single sources. EPA used data collected from 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 major concern.

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

In this rule, EPA is proposing to find nPB unacceptable in adhesive and
aerosol solvent end uses, acceptable subject to use conditions in the
coatings end use, and acceptable in the metals, electronics and
precision cleaning end uses. The proposed listings are intended to allow
the use of nPB where it can be used safely (i.e., with exposure at or
below 17 ppm on an eight-hour \[8-hr\] TWA), and to prohibit its use
where nPB cannot be used safely. We also are taking comment on the
alternate approach of finding nPB acceptable subject to use conditions
in the adhesive and aerosol solvent end uses. We summarize these
proposed decisions for each end use and sector and the alternate
proposal in Table 13.

**Table 13**. Proposed Decisions by End Use and Sector

+-------------------+------------------------+-------------------------+
| For nPB in this   | Our proposal is to     | And our alternate       |
| sector and end    | list nPB as:           | proposal is:            |
| use:              |                        |                         |
+-------------------+------------------------+-------------------------+
| *Solvent          |                        |                         |
| Cleaning*         |                        |                         |
+-------------------+------------------------+-------------------------+
| Metals Cleaning   | Acceptable (without    | Acceptable, subject to  |
|                   | restriction)           | use conditions^2^       |
+-------------------+------------------------+-------------------------+
| Electronics       | Acceptable (without    | Acceptable, subject to  |
| Cleaning          | restriction)           | use conditions^2^       |
+-------------------+------------------------+-------------------------+
| Precision         | Acceptable (without    | Acceptable, subject to  |
| Cleaning          | restriction)           | use conditions^2^       |
+-------------------+------------------------+-------------------------+
| ##                |                        |                         |
| *Aerosols* {#aero |                        |                         |
| sols .unnumbered} |                        |                         |
+-------------------+------------------------+-------------------------+
| Aerosol solvents  | Unacceptable           | Acceptable, subject to  |
|                   |                        | use conditions^2^       |
+-------------------+------------------------+-------------------------+
| *Adhesives,       |                        |                         |
| Coatings, and     |                        |                         |
| Inks*             |                        |                         |
+-------------------+------------------------+-------------------------+
| Coatings          | Acceptable, subject to | Acceptable, subject to  |
|                   | use conditions^1^      | use 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
have provided EPA information demonstrating their ability to meet the
recommended workplace exposure limit as of \[INSERT DATE OF
PUBLICATION\] (i.e., the Lake City Army Ammunition Plant).

^2^ Use conditions would include proposed requirements that users must
(1) meet a workplace exposure limit of 17 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. Solvent Cleaning

There are a number of alternatives that reduce the risks from ozone
depletion or from smog production[^17] slightly more than nPB when used
in industrial solvent cleaning equipment. However, we found no single
alternative that could work in all applications that clearly would
reduce *overall* risks to human health and the environment in metals
cleaning, electronics cleaning, and precision cleaning. Balancing the
different criteria discussed above in section IV., nPB does not pose a
significantly greater risk than other substitutes or than the ODS it is
replacing in these end uses if users meet the recommended exposure
limit. As discussed below, we believe that users can and will meet the
recommended exposure limit in these end uses. Thus, we propose to list
nPB as acceptable in metals cleaning, electronics cleaning, and
precision cleaning.

EPA believes that the great majority of users of nPB in metals cleaning,
electronics cleaning, and precision cleaning have been able to attain
exposure levels of less than 17 ppm with their existing equipment.
Recently measured exposure levels for nPB are much lower than historic
exposure data from the 1970s and 1980s for metals cleaning and
electronics cleaning (ICF, 2006a); this reflects both improvements in
industrial hygiene practices and improvements in cleaning equipment
since 1994 spurred by the National Emission Standard for Hazardous Air
Pollutants for Halogenated Solvent Cleaning (59 FR 61801).
Concentrations of nPB emitted from industrial solvent cleaning equipment
were found to be below 25 ppm in roughly 88% of 500 samples on an 8-hr
time-weighted average, below 17 ppm in 80% of these samples, and below
10 ppm in roughly 70% of these samples (US EPA, 2003). The WEL of 17 ppm
was attained the vast majority of the time, even when users were trying
to meet their suppliers' higher exposure limits of 25 ppm instead of 17
ppm, and even in the absence of any regulatory requirements.

One nPB supplier provided evidence that on the few occasions when nPB
concentrations from vapor degreasers were higher than the company's
recommended WEL of 25 ppm, users were able to reduce exposure easily and
inexpensively by changing work practices, such as reducing drafts near
the cleaning equipment (Kassem, 2003). The ability to meet the workplace
exposure limit depends on: (1) the features of the cleaning equipment
used, such as the presence of secondary cooling coils; and (2) the work
practices, such as avoiding drafts near cleaning equipment and lifting
cleaned pieces out slowly from the cleaning equipment. Workplace
controls could include, but are not limited to, the use of the
following: covers on cold-cleaning and vapor degreasing equipment when
not in use; devices to limit air movement over the degreaser; and/or a
lip-vent exhaust system to capture vapors and vent them out of the room.
Training workers in industrial hygiene practices and in the proper use
of cold cleaning and vapor degreasing equipment, as well as warning
workers of the symptoms that may occur from over-exposure to nPB, will
also help reduce exposure. Therefore, we expect that users of nPB in the
solvent cleaning sector following typical industry practices and using
typical equipment for vapor degreasing will continue to meet the WEL and
to use nPB safely without regulatory requirements. This is the approach
the SNAP program has taken with many other solvents where users are
readily able to meet available workplace exposure limit and there is no
enforceable OSHA PEL (e.g., HFC-365mfc, HFC-245fa,
heptafluorocyclopentane, ketones, alcohols, esters, hydrocarbons, etc.).
Based on the available exposure data and current industry practices, EPA
believes that workers using nPB in industrial solvent cleaning equipment
for metals cleaning, electronics cleaning, and precision cleaning are
unlikely to be exposed to amounts of nPB above EPA's proposed workplace
exposure level of 17 ppm.

B. Aerosol Solvents

In this rule, EPA proposes to find nPB unacceptable in the aerosol
solvent end use. As for solvent cleaning, we found that some
alternatives could reduce particular environmental risks more than nPB,
such as generation of ground level "smog" or ozone depletion potential.
There are a number of aerosol solvent alternatives that do not pose any
potential for ozone depletion or for ground-level smog formation.
However, in balancing the different concerns and criteria for
evaluation, we find the greatest concern in this end use is with nPB's
human health effects. We propose to find nPB unacceptable in aerosol
solvents because it increases overall impacts on human health and the
environment significantly more than other available alternatives.

Available information on the use of nPB in aerosols shows that aerosol
users may not be able to maintain exposures to nPB at or below the
recommended WEL without ventilation or with only regional ventilation
such as a fan for an entire room. Personal breathing zone samples
collected in a recent study 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[^18] (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 ft^3^/min was associated with the lowest exposure level. Similar
measurements were made in another study: 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).
In these same two studies, exposure measurements taken from the
breathing zone of workers over 15-minutes, if divided by 32 to estimate
an equivalent 8-hr TWA, would have varied from less than 1 ppm to 34.4
ppm (Linnell, 2003; Confidential submission, 1998).

These monitoring data are consistent with or slightly higher than data
from EPA modeling that estimates exposures for workers using different
amounts of aerosol (500 and 1000 g over a full day), different rates of
ventilation (450 to 1350 cfm), and different aerosol solvent
formulations (pure nPB and mixtures of nPB and other solvents
commercially available) (ICF, 2006a). In a space with an air exchange
rate of 450 ft^3^/minute or less[^19], EPA's modeling predicts 8-hour
average exposure of approximately 16 to 17 ppm if a user sprays 450 g of
pure nPB (approximately 1 lb)[^20], and corresponding higher exposure
values at higher spray rates (e.g., 33 ppm if the amount of nPB sprayed
is 900 g) (ICF, 2006a). Therefore, if users varied the amount of nPB
used only slightly above a pound per day on average or had ventilation
levels below 450 cfm (face velocity of 50 fpm), they would be exposed in
excess of the WEL. EPA is aware of no data on ventilation levels that
would demonstrate that most users of aerosol solvents, or of nPB in
particular, would use aerosols in locations with ventilation levels of
450 cfm or greater. The available worker exposure studies examined
ventilation levels of 0, 48, 300, 472, 640, and 1900 cfm, implying that
manufacturers for this sector believe that ventilation flow rates could
be lower than 450 cfm. Based on the available monitoring and modeling
data, we expect exposure to nPB to exceed the proposed workplace
exposure limit of 17 ppm in confined spaces and in the many applications
for nPB-based aerosols where ventilation equipment is not or cannot be
installed, such as on energized electrical equipment (Linnell, 2003;
Werner, 2003; CSMA, 1999). Aerosol manufacturers have stated that the
majority of the market for nPB used in aerosols is for electrical
contact cleaning (Williams, 2005). We are reviewing nPB as a replacement
for HCFC-141b and in-place cleaning such as for electrical contact
cleaning comprised the majority of the aerosol market for HCFC-141b (US
EPA, 2004). Further, because aerosol cans are portable and their use
cannot reasonably be monitored continuously, EPA cannot ensure that
nPB-based aerosols are barred from use in confined spaces where exposure
levels would be likely to exceed the WEL and create excessive health
risks. Thus, EPA believes that it would be difficult or even impossible
to meet a recommended workplace exposure limit of 17 ppm in the majority
of situations where nPB would be used as a substitute for HCFC-141b as
an aerosol solvent.

EPA has found numerous other aerosol solvents acceptable. These aerosol
solvents can be used safely in a manner consistent with their respective
workplace 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). nPB exposure in similar ranges would be from two to eleven times
the WEL for nPB. Thus, nPB would impose significantly more risk to human
health and the environment than other alternatives available for this
end use.

C. Adhesives

EPA proposes to find nPB unacceptable in the adhesive end use. As for
solvent cleaning and aerosols, 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 increases overall impacts on human health and the environment
significantly more than other available alternatives.

Available information on exposure levels during use of nPB-based
adhesives indicates that it would be difficult to meet a recommended
exposure limit of 17 ppm. Therefore, we believe nPB poses a
significantly greater risk than other available substitutes in this end
use. For exposure to nPB when used in adhesives, 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 recommended by NIOSH (NIOSH, 2000b). Although use of spray
booths at this facility had a dramatic effect of reducing the
[average]{.underline} exposure level to 19.4 ppm, individual exposures
were still excessive. Eleven of fourteen sprayers (79%) and sixteen of
all thirty workers (53%) monitored continued to have exposures exceeding
the proposed WEL of 17 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 44% (15 of 34) of exposure samples were
higher than the proposed recommended WEL of 17 ppm, even after improving
ventilation.

Modeled data of workplace exposure based on average amounts of spray
adhesive and average ventilation would result in exposure levels of
roughly 60 ppm, more than three times the WEL (ICF, 2006a). In at least
four cases, workers using nPB-based adhesives have been exposed to
excessive amounts of nPB, to the point where they needed to be
hospitalized for adverse neurological effects (Ichihara et al., 2002 and
Miller, 2005; Raymond and Ford, 2005; Beck and Caravati, 2003, and
Majersik et al., 2004, 2005; Calhoun County, 2005).

Considering the exposure data for nPB-based adhesives, we believe it is
unlikely that, even with ventilation, exposure levels for adhesives
users would be below the proposed recommended WEL on a consistent basis.
Overall, 48% of all workers in these two facilities using nPB-based
adhesives were exposed to concentrations of nPB greater than the
proposed recommended WEL of 17 ppm (31 of 64 workers), 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.

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 data on whether it is feasible to use nPB-based
adhesives with worker exposure levels consistently below the proposed
recommended WEL of 17 ppm on an 8-hr TWA.

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 set by OSHA, the ACGIH, the
American Industrial Hygiene Association, or EPA. 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
present 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 of nPB in
the adhesives end use for which there are no other technically feasible
alternatives, and thus, for which nPB should be allowed. If so, 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 exposure
levels to the proposed recommended WEL, and to perform worker exposure
monitoring. Alternatively, if there were sufficient information provided
during the public comment period showing that there are applications in
which only nPB can be used, we would consider finding nPB acceptable in
adhesives, subject to use conditions requiring installation of local
exhaust ventilation and worker exposure monitoring, and subject to a
narrowed use limit for those specific applications where other
alternatives are not technically feasible, without requiring a
site-specific demonstration that nPB is the only feasible alternative.
This would allow for safer use of nPB in any applications where nPB is
the only alternative, if any such applications exist.

D. Coatings

We are proposing to find nPB acceptable, subject to use conditions, for
facilities that have provided EPA information demonstrating their
ability to meet the recommended workplace exposure limit as of \[INSERT
DATE OF PUBLICATION\]. 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. 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 EPA's proposed recommended workplace exposure limit
of 17 ppm. Thus, we believe that nPB can be used as safely as other
acceptable solvents used at their workplace 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
available 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 significantly increase risks to human health
compared to other acceptable substitutes in the coatings end use.

**VII. How did EPA choose the use conditions in the alternate proposal,
and why?**

We also take comment on an alternate proposal. In order to provide
flexibility for companies to choose nPB, but only where it would not
pose a significantly greater risk than use of other available
alternatives, we could require users to meet use conditions specifying a
worker exposure limit, monitoring, and recordkeeping. Users would be
required to (1) meet a workplace exposure limit of 17 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. The use condition requiring
users to meet the WEL would protect human health by ensuring that
exposure is not above a level that is safe. Monitoring of worker
exposure levels would give users a tool to identify and correct faulty
work practices or improve or replace equipment that provides
insufficient ventilation that, if undetected and uncorrected, would
result in exposure to nPB above the WEL of 17 ppm. Keeping records of
the monitoring data would give EPA the ability to enforce the monitoring
and exposure limit requirements.

In developing this proposal, EPA considered whether nPB presented a more
significant risk than other available ODS alternatives. We believe that
use of nPB does not present significantly more risk so long as exposure
levels are maintained below the proposed WEL. Establishing use
conditions could help ensure that users meet the WEL. Therefore, EPA is
taking comment on use conditions that would require users to meet the
workplace exposure limit and monitor worker exposure.

A. Use Conditions and Their Rationale

The major provisions of the use conditions and the related issues that
EPA considered in developing the alternate proposal are as follows:

*Workplace exposure limit*. A requirement to meet the 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 WEL. 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 WEL 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 a WEL 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.

*Worker exposure monitoring.* We modeled the worker exposure monitoring
requirements on 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 WEL is 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
(ERG, 2004).

[Option for monitoring representative set of workers]{.underline}.
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 WEL and avoiding underestimates of exposure.

[Initial monitoring]{.underline}*.* 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]{.underline}. 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. We would use a value of
8.5 ppm, half the proposed WEL of 17 ppm, as the action level. OSHA
standards also set an action level of half the PEL.

Monitoring would no longer be required where the most recent exposure
monitoring data found all worker exposures at or below 8.5 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]{.underline}*.* New monitoring would be required if an event occurs
that would make the most recent set of monitoring data no longer
representative. Examples of these changes are discussed above in section
III.F. Normally, 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 alternate proposal. 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
[+]{.underline} 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 up to three years from the date the
measurement is taken. This would provide information allowing EPA to
determine if facilities are complying with the WEL and if people exposed
to nPB are sufficiently protected. However, we note that 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 still be in effect.

*Responsibility for meeting requirements.* Under the alternate proposal,
the owner or operator of a facility using nPB would be responsible for
meeting the rule's use conditions.

## B. Advantages and disadvantages of the alternate proposal {#b.-advantages-and-disadvantages-of-the-alternate-proposal .unnumbered}

Setting use conditions that require users to meet a WEL and to monitor
and keep records to demonstrate achieving the WEL 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
who 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 a WEL, worker exposure monitoring, and
recordkeeping would be complex and potentially confusing. Requiring
users to meet the WEL, 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 WEL, only to find
that it is not achievable.

In the past, EPA only required a WEL for solvents that were new for
which there was limited workplace experience and a concern that the
exposure limit might be exceeded, such as when HFC-4310mee,
HCFC-225ca/cb, monochlorotoluenes, and benzotrifluorides were first
introduced. Since then, we have concluded that users would easily be
able to meet exposure limits for most substitutes for which such a limit
existed, and thus, EPA found no need to impose a workplace exposure
limit as a use condition. For a compound such as nPB, for which
workplace exposure data exist, there is greater certainty as to whether
the WEL would be exceeded. Given the limited circumstances under which
we expect aerosol and adhesive users could meet the workplace exposure
limit and given the availability of other, less toxic alternatives in
both of these end uses, EPA would prefer to find nPB unacceptable in
aerosols and adhesives. Further, considering that so many users of nPB
for metals, electronics, and precision cleaning and the users of nPB at
the Lake City Army Ammunition Plant meet the proposed WEL without
regulatory requirements (US EPA 2003; Lake City Army Ammunition Plant,
2004), it appears unnecessary to require an exposure limit in those end
uses.

VIII. **What other options did EPA consider?**

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

A. Regulatory options based on the ACGIH's Threshold Limit Value

We considered using ACGIH's TLV of 10 ppm as a workplace exposure limit
to recommend and to use in assessing human health risks to workers. For
certain other compounds that EPA found acceptable, we used a TLV when
available (e.g., acetone, cyclohexane, isopropyl alcohol). However, as
discussed above in section V.A, EPA has concerns about the documentation
and basis of ACGIH's TLV derivation for nPB. We note that if we were to
choose the TLV as the appropriate workplace exposure limit for assessing
human health risks of nPB, we would have proposed the same decisions for
each end use for the following reasons.

We believe that workers using nPB in solvent cleaning usually will not
be exposed in excess of the ACGIH's TLV of 10 ppm because roughly 70% of
samples from the workplace already meet this level, even when users were
aiming to meet a higher exposure limit of 25 ppm (US EPA, 2003).
Further, information from an nPB solvent supplier with a product
stewardship program demonstrates that users could take steps that
effectively reduce emissions further (Kassem, 2003).

For aerosol solvents, as mentioned above in Section VI.B, it would be
difficult for users in this end use to meet a higher recommended WEL of
17 ppm. Considering available exposure data from personal samples in two
studies, only one of seven samples on an eight-hour time-weighted
average showed an exposure level of 10 ppm or lower (ICF, 2006a).
Modeled exposures exceeded 10 ppm, even with some ventilation, if more
than a pound of nPB were used in a day.

In the adhesives end use, 80% of the exposure data are above 10 ppm,
even after installing state-of-the-art ventilation. Only one sprayer was
exposed to 10 ppm or less in reports from NIOSH (NIOSH, 1999, 2000a,
2002a, 2002b, 2003, etc). Modeled data of workplace exposure based on
average amounts of spray adhesive and average ventilation would result
in exposure levels of roughly 60 ppm, approximately six times more than
a level of 10 ppm (ICF, 2006a).

Tests at the Lake City Army Ammunition Plant showed an ability to meet a
WEL 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).

B.  Regulatory options requiring ventilation 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.

### 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 fell below 17 ppm reliably 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. Local exhaust ventilation is ventilation that
removes vapors from a specific work location using ducts and fans.
Regional ventilation is 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 the WEL.

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.

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, 1999; 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 (ICF, 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 without excessive worker
exposure. 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.

# 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 achieve a WEL of 17 ppm 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 the WEL, 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.

**IX.** **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%. The acceptability
determination for solvents cleaning imposes no requirements and thus
creates no additional cost to users. In addition, 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 considered potential costs end users could incur if they
implemented the recommended acceptable exposure limit and are not
already achieving it. EPA found that those users using nPB-based
solvents in a vapor degreaser would save money by reducing solvent
losses, and that the savings would recover the costs of emissions
controls (e.g., secondary cooling coils, automated lifts or hoists)
within a year of installation. Based on evidence from solvent suppliers,
EPA believes that some of those users would have chosen to use nPB in
order to avoid meeting requirements of the national emission standard
for halogenated solvents cleaning and that they would only become aware
of the potential savings due to reduced solvent usage as a result of
this proposal (Ultronix, 2001; Kassem, 2003; Tattersall, 2004). Based on
available exposure data for each sector, we assumed that 80% of nPB
users in the non-aerosol solvent cleaning sector already achieve
exposure levels of 17 ppm or less (US EPA, 2003). Of those nPB solvent
users with exposure levels above 17 ppm, we examined the cost associated
with reducing emissions on average by 60%.

-   Full implementation of the recommended workplace exposure guideline
    across all nPB users in solvent cleaning would save up to \$2
    million dollars per year. The value will depend on the number of
    users that attempt to meet the recommended exposure guideline, the
    number already achieving the WEL with existing equipment, the
    initial exposure level of cleaning solvent users, the price of nPB,
    and the amount of emission control equipment installed.

-   When the potential costs of compliance with the regulatory
    requirements and the recommended workplace exposure limit are
    considered together, EPA estimated the total cost in all sectors
    would range from \$ 37.0 to 44.4 million annually.

We also estimated the cost to the user community of the use conditions
in the alternate proposal for aerosols, adhesives, coatings, and solvent
cleaning. The requirements for users to meet a workplace exposure limit
and to perform exposure monitoring would be in the range of \$ 41.5 to
72.2 million per year. The upper end of the range of estimated impacts
likely 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. 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. For solvent cleaning, we assumed no change in equipment
for 80% of users, the upgrading of vapor degreasing equipment for the
remaining 20%, and monitoring an average of 1.3 times per year. Using
these assumptions, we calculated the cost of the use conditions in the
alternate proposal at \$18.0 to 24.0 million for adhesive users, \$24.3
to 43.5 million for aerosol users, and \$ -0.8 to \$ 4.7 million for
solvent cleaning 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 alternate proposal are
summarized in Table 14. For more detailed information, see section
XIII.C. below and EPA's analysis in the docket (US EPA, 2006).

**Table 14**. Estimated Costs of Regulatory Options EPA is Providing for
Comment

  -------------- ---------------- ------------- ---------------- --------------
  Sector or End  Requirements     Annual Cost   Requirements     Annual Cost of
  Use            under Alternate  of Alternate  under Proposed   Proposed Rule
                 Proposal         Proposal      Rule             

  Solvent        Achieve WEL of   \$-0.8 to 4.7 None explicit;   Cost savings
  Cleaning       17 ppm; exposure million       recommended WEL  of up to \$
  (Metals,       monitoring, one                of 17 ppm with   2.0 million
  Electronics,   or two times per               expectation that from reduced
  and Precision  year;                          users will meet  solvent
  Cleaning)      recordkeeping                  WEL              consumption
                                                                 when meeting
                                                                 WEL

  Aerosol        Achieve WEL of   \$24.3 to     Cease use of nPB \$ 36.3 to
  Solvents       17 ppm; exposure 43.5 million  and switch to a  39.7 million
                 monitoring one                 different ODS    
                 or two times per               substitute.      
                 year;                                           
                 Recordkeeping                                   

  Coatings       Achieve WEL of   None; only    None explicit;   None; only
                 17 ppm; exposure known         recommended WEL  known facility
                 monitoring, one  facility      of 17 ppm with   using
                 or two times per using         expectation that nPB-based
                 year;            nPB-based     users will meet  coatings
                 recordkeeping.   coatings      WEL. Decision    already
                                  already       only applies to  achieves the
                                  achieves the  use nPB in       WEL
                                  WEL and       coatings at at   
                                  performs      facilities that  
                                  exposure      have provided    
                                  monitoring    EPA information  
                                                demonstrating    
                                                their ability to 
                                                meet the         
                                                recommended      
                                                workplace        
                                                exposure limit   
                                                as of \[INSERT   
                                                DATE OF          
                                                PUBLICATION\].   

  Adhesives      Achieve WEL of   \$ 18.0 to    Cease use of nPB \$ 2.3 to 6.7
                 17 ppm; exposure 24.0 million  and switch to a  million
                 monitoring, one                different ODS    
                 or two times per               substitute.      
                 year;                                           
                 recordkeeping                                   

  Total                           \$ 41.5 to                     \$37.0 to 44.4
                                  72.2 million                   million
  -------------- ---------------- ------------- ---------------- --------------

**X. Comparison of EPA's June 2003 proposal and this proposal**

Table 15 compares the acceptability determination and evidence cited in
the June 2003 proposal and this proposal.

Table 15: n-Propyl Bromide Acceptability Decision

+-----------------+-------------------------+-------------------------+
| **Proposed      | **2003 Proposed Rule**  | **Current Proposed      |
| Decision**      |                         | Rule---Preferred        |
|                 |                         | Proposal**              |
+=================+=========================+=========================+
| **Industrial    | Acceptable, Subject to  | Acceptable; WEL of 17   |
| End Uses        | a Use Condition         | ppm^2^ on 8-hr TWA      |
| #1-3:**         | (Limiting use to nPB    | recommended             |
|                 | formulations containing |                         |
| **Metals        | no more than 0.05% by   |                         |
| Cleaning,       | weight isopropyl        |                         |
| Electronics     | bromide); WEL of 25     |                         |
| Cleaning, and   | ppm^1^ on 8-hr TWA      |                         |
| Precision       | recommended             |                         |
| Cleaning        |                         |                         |
| (Solvent        |                         |                         |
| Cleaning)**     |                         |                         |
+-----------------+-------------------------+-------------------------+
| **Industrial    | Acceptable, Subject to  | Unacceptable            |
| End Use #4:**   | a Use Condition         |                         |
|                 | (Limiting use to nPB    |                         |
| **Aerosol       | formulations containing |                         |
| Solvents**      | no more than 0.05% by   |                         |
|                 | weight isopropyl        |                         |
|                 | bromide; WEL of 25      |                         |
|                 | ppm^1^ on 8-hr TWA      |                         |
|                 | recommended             |                         |
+-----------------+-------------------------+-------------------------+
| **Industrial    | Acceptable, Subject to  | Unacceptable            |
| End Use #5:**   | a Use Condition         |                         |
|                 | (Limiting use to nPB    |                         |
| **Adhesives**   | formulations containing |                         |
|                 | no more than 0.05% by   |                         |
|                 | weight isopropyl        |                         |
|                 | bromide; WEL of 25      |                         |
|                 | ppm^1^ on 8-hr TWA      |                         |
|                 | recommended             |                         |
+-----------------+-------------------------+-------------------------+
| **Industrial    | Not addressed           | Acceptable, Subject to  |
| End Use #6:     |                         | Narrowed Use Limits     |
| Coatings**      |                         | (Decision limited to    |
|                 |                         | coatings at facilities  |
|                 |                         | that have provided EPA  |
|                 |                         | information             |
|                 |                         | demonstrating their     |
|                 |                         | ability to meet the     |
|                 |                         | recommended workplace   |
|                 |                         | exposure limit as of    |
|                 |                         | \[INSERT DATE OF        |
|                 |                         | PUBLICATION); WEL of 17 |
|                 |                         | ppm^2^ on 8-hr TWA      |
|                 |                         | recommended             |
+-----------------+-------------------------+-------------------------+

^1^ Proposed Workplace Exposure Limit of 25 ppm based upon nPB's effect
on sperm motility from ICF's 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^ Proposed Workplace Exposure Limit of 17 ppm based upon nPB's
    effect on the number of estrous cycles and estrous cycle length from
    ICF's re-evaluation of the WIL 2001 Study "An Inhalation
    Two-Generation Reproductive Toxicity Study of 1-Bromopropane in
    Rats."

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a)  ICF, 2006a, "Risk Screen for Use of N Propyl Bromide", Prepared for
    U.S. EPA, April, 2006.

b)  ICF, 2004c, "Expert Panel Response on nPB AEL", Prepared for U.S.
    EPA, December, 2004

c)  ICF, 2004d, "nPB Human Relevance", Prepared for U.S. EPA, September,
    2004

    Also, evaluation of documents by Stelljes and Wood (2004); TERA
    (2004); ACGIH (2005); Rozman and Doull (2005); Stelljes (2005); and
    others.

    **XI. How can I use nPB as safely as possible?**

    Below are actions that will help nPB users meet the workplace
    exposure limit proposed in this rule:

*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.

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```
-   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.

-   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.

*Solvent cleaning*

-   For non-aerosol solvent cleaning, follow guidelines in the NESHAP
    for halogenated solvents cleaning if you are using nPB. The
    equipment and procedural changes described in the halogenated
    solvents NESHAP can reduce emissions, reduce solvent losses and
    lower the cost of cleaning with organic solvents. For more
    information on the halogenated solvents NESHAP, visit
    http://www.epa.gov/ttn/atw/eparules.html and
    <http://www.epa.gov/ttn/atw/degrea/halopg.html.>

*Spray applications*

-   For spray applications (e.g., aerosols), use sufficient ventilation
    to meet the recommended 17 ppm WEL.

-   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
    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 is 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.

**XII. Statutory and Executive Order Reviews**

A. *Executive Order 12866: Regulatory Planning and Review*

Under Executive Order (EO) 12866 Number range CHAPTER(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. Number range CHAPTER 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.

Number range CHAPTERIn 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 nPB
Rulemaking." 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 \$37 and 44.4 million per year, with the health benefits being
as high as \$111 million per year.

## *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]{.underline}, 44 U.S.C. 3501
[et]{.underline} [seq]{.underline}. An Information Collection Request
(ICR) document has been prepared by EPA (ICR No. 2224.01) and a copy may
be obtained from Susan Auby by mail at Collection Strategies Division;
U.S. Environmental Protection Agency (2822T); 1200 Pennsylvania Ave.,
NW, Washington, DC 20460, by email at auby.susan@epamail.epa.gov, or by
calling (202) 566-1672. A copy may also be downloaded off the internet
at [www.regulations.gov](http://www.regulations.gov/). in Docket
EPA-HQ-OAR-2002-0064.

If the provisions of this proposed rule become final, there would be no
new information collection burden. This proposed rule is an Agency
determination. It 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. 1596.05). 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 alternate proposal, users of nPB
would have an information collection burden from exposure monitoring and
recordkeeping. Under the alternate proposal, 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 alternate proposal is as much as \$12.8 million and 24,050
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 1.6 monitoring events per year per worker, assuming that
roughly 60% of exposed workers must be monitored every six months and
40% must be monitored once annually. We estimate that up to 75,000
workers would be monitored for exposure to nPB. Costs 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.

We request comments 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. Send comments on the ICR to the Director,
Collection Strategies Division; U.S. Environmental Protection Agency
(2822T); 1200 Pennsylvania Ave., NW, Washington, DC 20460; and to the
Office of Information and Regulatory Affairs, Office of Management and
Budget, 725 17th St., N.W., 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 \[Insert date of publication in the FEDERAL
REGISTER\], a comment to OMB is best assured of having its full effect
if OMB receives it by \[Insert date 30 days after publication in the
FEDERAL REGISTER\]. The final rule will respond to any OMB or public
comments on the information collection requirements contained in this
proposal.

C. *Regulatory Flexibility Act (RFA)*

The Regulatory Flexibility Act (RFA) generally requires an agency to
prepare a regulatory flexibility analysis of any rule subject to notice
and comment rulemaking requirements under the Administrative Procedure
Act or any other statute unless the agency certifies that the rule will
not have a significant economic impact on a substantial number of small
entities. Small entities include small businesses, small organizations,
and small governmental jurisdictions. 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
USC 601(3) - (5). In addition, to establish an alternate small business
definition, agencies must consult with SBA's Chief Counsel for Advocacy.

For purposes of assessing the impacts of the proposed rule on small
entities, EPA is proposing to define "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 subject toincluded in our analysis but slightly increased the
percentages of small business significantly impacted in the analysis.
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. We
solicited comments on the choice of this alternate definition for this
analysis on the June 2003 NPRM, and received no public comments. We
again request comment on this alternate definition of "small business."

EPA consulted with the Small Business Administration Office of Advocacy
on the alternate small business definition of 500 employees for the June
2003 proposal. The Office of Advocacy concurred with EPA's approach. The
number and types of small businesses that would be regulated have not
changed significantly in this NPRM from the June 2003 proposal, and EPA
is proposing the same definition.

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. EPA estimates
that up to 4850 small industrial end users currently use nPB in the end
uses addressed by this rule and thus could be subject to the regulatory
impacts of this rule. This number includes approximately 1470 users of
nPB industrial cleaning solvents (e.g., cleaning with vapor degreasers),
3100 users of nPB-based aerosol solvents, and 280 users of nPB-based
adhesives. Considering together the regulatory impacts on adhesive and
aerosol users that must switch to other alternatives and the costs to
solvent users to implement the recommended 17 ppm exposure limit, we
found that up to 258 (8%) 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 percentage of small businesses that would experience
significant 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 primary metals, where there may be a need to clean
    off oil and grease (NAICS subsectors 331).

-   Manufacturers of fabricated metal parts, including plating, ball and
    roller bearings, machined parts, and other metal parts that require
    oil and grease to be cleaned off; and manufacturers of ammunition
    using coatings or sealants (NAICS subsectors 332, 333, and 339).

-   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).

    EPA estimates that up to 4850 small industrial end users currently
    use nPB in the end uses addressed by this rule and thus could be
    subject to the regulatory impacts of this rule. This number includes
    approximately 1470 users of nPB industrial cleaning solvents (e.g.,
    cleaning with vapor degreasers), 3100 users of nPB-based aerosol
    solvents, and 280 users of nPB-based adhesives.

    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
    of this proposed rule.

    **Table 16. Average Value of Shipments in NAICS Subsectors
    Performing Solvent Cleaning**,

    **by Number of Employees at Business**

  ------------ ------------ ------------ ------------- ------------ ------------ ----------------- ------------ -------------
  **Number of  **Average                                                                                        
  Employees at Value of                                                                                         
  Business**   Shipments                                                                                        
               per Business                                                                                     
               (\$) by                                                                                          
               NAICS                                                                                            
               Subsector                                                                                        
               Code**                                                                                           

               **331,       **332,       **333,        **334,       **335,       **336,            **337,       **339,Misc.
               Primary      Fabricated   Machinery**   Computer and Electrical   Transport-ation   Furniture    Mfg**
               Metal Mfg**  Metal                      Electronic   Equipment,   Equipment**       and Related  
                            Products**                 Products**   Appliance,                     Products**   
                                                                    and                                         
                                                                    Component                                   
                                                                    Mfg**                                       

  1 to 4       368,580      222,973      301,232       345,007      315,772      412,460           180,805      181,876
  employees                                                                                                     

  5 to 9       1,369,866    835,793      1,049,335     1,317,238    1,243,065    1,414,384         712,557      773,320
  employees                                                                                                     

  10 to 19     2,828,531    1,654,147    1,988,048     2,566,913    2,483,327    2,573,352         1,704,272    1,543,581
  employees                                                                                                     

  20 to 49     7,258,463    4,119,582    4,768,137     5,672,245    5,389,945    5,738,739         3,297,360    3,910,203
  employees                                                                                                     

  50 to 99     17,350,990   10,300,841   11,882,524    12,951,836   12,650,236   12,735,583        8,460,846    9,836,121
  employees                                                                                                     

  100 to 249   38,539,490   27,472,772   29,166,421    31,258,875   31,290,638   34,256,544        20,153,844   24,981,108
  employees                                                                                                     

  250 to 499   95,889,945   61,152,558   81,774,945    84,270,454   77,279,974   86,911,454        48,821,903   68,880,502
  employees                                                                                                     

  Avg Value    11,935,698   3,812,656    5,359,829     8,261,788    9,539,205    11,029,561        2,536,805    2,923,741
  Ship Small                                                                                                    
  Businesses                                                                                                    
  in                                                                                                            
  Sub-sector                                                                                                    

  Avg Value    28,783,017   4,168,836    6,620,907     20,810,094   13,417,905   45,029,773        2,875,473    3,857,370
  Ship ALL                                                                                                      
  Businesses                                                                                                    
  in Subsector                                                                                                  

  Avg Value    22,311,696   6,814,736    9,337,066     11,246,045   12,066,562   13,422,547        5,178,300    5,461,637
  Shipments                                                                                                     
  Subset Small                                                                                                  
  Businesses                                                                                                    
  using nPB                                                                                                     
  ------------ ------------ ------------ ------------- ------------ ------------ ----------------- ------------ -------------

^1^ Aerosol solvents are used in NAICS subsectors 334, 335 and 336.
Non-aerosol solvents are used in all seven NAICS subsectors.

^2^ "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.

**Table 17. Average Value of Shipments in NAICS Categories**

**Using nPB as a Carrier Solvent in Adhesives, by Number of Employees at
Business**

+------------+-----------+-----------+----------+-----------+---------+
| **Number   | # Average |           |          |           |         |
| of         |  Value of |           |          |           |         |
| Employees  |  Shipment |           |          |           |         |
| at         | s per Sma |           |          |           |         |
| Business** | ll Busine |           |          |           |         |
|            | ss (\$) b |           |          |           |         |
|            | y NAICS S |           |          |           |         |
|            | ub Sector |           |          |           |         |
|            |  {#averag |           |          |           |         |
|            | e-value-o |           |          |           |         |
|            | f-shipmen |           |          |           |         |
|            | ts-per-sm |           |          |           |         |
|            | all-busin |           |          |           |         |
|            | ess-by-na |           |          |           |         |
|            | ics-sub-s |           |          |           |         |
|            | ector .un |           |          |           |         |
|            | numbered} |           |          |           |         |
+------------+-----------+-----------+----------+-----------+---------+
|            | **        | **        | **3      | **        | **33    |
|            | 337121,** | 337110,** | 26150,** | 336360,** | 7124,** |
|            |           |           |          |           |         |
|            | **Up      | **Wood    | **       | **Motor   | **Metal |
|            | holstered | kitchen   | Urethane | vehicle   | ho      |
|            | household | cabinet   | and      | seating   | usehold |
|            | fu        | and       | other    | and       | furn    |
|            | rniture** | counter   | foam     | interior  | iture** |
|            |           | tops**    | products | trim**    |         |
|            |           |           | (except  |           |         |
|            |           |           | polyst   |           |         |
|            |           |           | yrene)** |           |         |
+------------+-----------+-----------+----------+-----------+---------+
| **1 to 4   | 234,345   | 156,833   | 496,318  | 425,863   | 187,950 |
| e          |           |           |          |           |         |
| mployees** |           |           |          |           |         |
+------------+-----------+-----------+----------+-----------+---------+
| **5 to 9   | 963,021   | 622,744   | 1        | 1,728,132 | 903,393 |
| e          |           |           | ,305,183 |           |         |
| mployees** |           |           |          |           |         |
+------------+-----------+-----------+----------+-----------+---------+
| **10 to 19 | 1,771,416 | 1,141,119 | 3        | 3,082,486 | 1,      |
| e          |           |           | ,152,283 |           | 431,480 |
| mployees** |           |           |          |           |         |
+------------+-----------+-----------+----------+-----------+---------+
| **20 to 49 | 3,653,623 | 2,619,197 | 6        | 5,508,370 | 3,      |
| e          |           |           | ,615,331 |           | 538,684 |
| mployees** |           |           |          |           |         |
+------------+-----------+-----------+----------+-----------+---------+
| **50 to 99 | 8,089,968 | 7,386,365 | 13       | 1         | 7,      |
| e          |           |           | ,281,000 | 4,088,500 | 547,536 |
| mployees** |           |           |          |           |         |
+------------+-----------+-----------+----------+-----------+---------+
| **100 to   | 1         | 1         | 31       | 4         | 19,     |
| 249        | 7,502,175 | 7,151,091 | ,524,872 | 4,310,286 | 821,719 |
| e          |           |           |          |           |         |
| mployees** |           |           |          |           |         |
+------------+-----------+-----------+----------+-----------+---------+
| **250 to   | 4         | 5         | 64       | 12        | D(1)    |
| 499        | 0,250,813 | 5,982,674 | ,119,800 | 3,803,610 |         |
| e          |           |           |          |           |         |
| mployees** |           |           |          |           |         |
+------------+-----------+-----------+----------+-----------+---------+
| **Avg      | 3,588,297 | 1,150,768 | 10       | 1         | 3,      |
| Small      |           |           | ,472,992 | 2,542,725 | 141,720 |
| Businesses |           |           |          |           |         |
| in Sub     |           |           |          |           |         |
| sector**   |           |           |          |           |         |
+------------+-----------+-----------+----------+-----------+---------+
| **Avg ALL  | 5,490,101 | 1,475,602 | 11       | 4         | 5,      |
| Businesses |           |           | ,110,822 | 4,808,573 | 239,747 |
| in Sub     |           |           |          |           |         |
| sector**   |           |           |          |           |         |
+------------+-----------+-----------+----------+-----------+---------+
| **Avg      | 1         | 5,999,622 | 18       | 1         | 20,     |
| Subset     | 1,519,540 |           | ,950,068 | 2,019,847 | 401,301 |
| Small      |           |           |          |           |         |
| Businesses |           |           |          |           |         |
| using      |           |           |          |           |         |
| nPB**      |           |           |          |           |         |
+------------+-----------+-----------+----------+-----------+---------+

^(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 requires that nPB would be 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 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 five percent of all 4850 or so small
businesses choosing to use nPB 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 rule to have a significant impact on a substantial
number of small businesses.

The Agency analyzed the cost impacts of implementing the exposure limit
for solvent cleaning uses in order to provide additional information
about potential effects on small businesses. Businesses using nPB-based
cleaning solvents for metals cleaning, electronics cleaning, or
precision cleaning would experience significant cost benefits by
reducing spending on solvent.

Considering together the regulatory impacts on adhesive and aerosol
users that must switch to other alternatives and the costs to solvent
users to implement the recommended 17 ppm exposure limit, we found that
up to 258 (8%) 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 percentage of small businesses that would experience significant
impacts, EPA concludes that this rule would not have a significant
economic impact on a substantial number of small entities.

We also analyzed the potential small business impacts of the alternate
proposal. Under the alternate proposal, users would have to: (1) meet a
workplace exposure limit of 17 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 alternate
proposal 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), no solvent cleaning
users, and 2.6 to 12.6 percent of all 4850 or so small businesses would
experience impacts of greater than 1% of annual sales if they chose to
meet nPB the proposed requirements with the applicable use conditions
rather than switching to another ODS substitute. Four to nine users of
nPB-based adhesives, or less than 1% of all small businesses, would
experience impacts of 3% or greater of annual sales under the alternate
proposal. Based on this analysis, the alternate proposal would not
create a significant adverse impact on a significant 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 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 workplace exposure limit or requiring a switch to another
    alternative.

-   Requiring that users clean metal, electronics, or other parts with
    nPB in low-emission air-tight vapor degreasing equipment.

• Requiring that users clean metal, electronics, or other parts with nPB
in vapor degreasing equipment that meets the requirements of the
national emission standards for halogenated solvent cleaning.

-   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
(EPA, 2006).

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 \$37.0 to 44.4 million per year, and the
alternate proposal would cost the private sector approximately \$ 49.6
to 76.2 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 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.

    Further, this proposed rule provides both regulatory restrictions
    and recommended exposure guidelines based upon toxicological studies
    in order to reduce risk of exposure to a reproductive toxin, nPB.
    This proposed rule is not subject to Executive Order 13045 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 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\"), Pub L. No. 104-113, §
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 a proposed or final workplace exposure
limit from the ACGIH is not subject to the NTTAA.

**XIII. 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.

***What criteria did EPA consider in preparing this proposal?***

Fabricant, 2003. Memo to Acting Administrator, Marianne L. Horinko.
2003. EPA's Authority to Impose Mandatory Controls to Address Global
Climate Change under the Clean Air Act, from Robert E. Fabricant.

ICF, 2006a. ICF Consulting. Risk Screen on Substitutes for
Ozone-Depleting Substances for Adhesive, Aerosol Solvent, and Solvent
Cleaning Applications. Proposed Substitute: n-Propyl Bromide. April 18,
2006.

***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.

IBSA, 2002. Number range CHAPTERRecord of September 5, 2002 Meeting with
the International Brominated Solvents Association Inc. (A-2001-07,
II-D-60)

IRTA, 2000. Number range CHAPTERAlternative 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. Number range CHAPTERTelephone 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

***Ozone-Depletion Potential 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>

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>

ATSDR, 1997. Toxicological Profile For Trichloroethylene. Agency for
Toxic Substances and Disease Registry. September, 1997. Available at
http://www.atsdr.cdc.gov/toxprofiles/tp19-c5.pdf

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>

EDSTAC, 1998. Final Report of the Endocrine Disruptor Screening and
Testing Advisory Committee. August, 1998.

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>

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 Environmental Stud.,
Univ.of Wisconsin-Superior, Superior, WI I:355. (Summarized in ICF,
2004a)

HSDB, 2004. Hazardous Substances Databank File for 1-Bromopropane.
Accessed 1/2004 from the World Wide Web at
http://toxnet.nlm.nih.gov/cgi-bin/sis/search/f?./temp/\~dLwM9e:1
(Summarized in ICF, 2004a)

ICF, 2004a. ICF Consulting. Memo to E. Birgfeld, EPA, re: nPB Aquatic
Toxicity. January 19, 2004.

LaGrega, M., Buckingham, P., Evans, J., and Environmental Resources
Management, 2001. *Hazardous Waste Management.* Second Edition.
McGraw-Hill, New York, NY. 2001.

Linnell, 2003. Comments from the Electronics Industry Alliance.
(EPA-HQ-OAR-2002-0064 items -0043, -0044, and -0045)

NPS, 1997. Irwin, R.J., M. VanMouwerik, L. Stevens, M.S. Seese, and W.
Basham. 1997. Environmental Contaminants Encyclopedia. National Park
Service,Water Resources Division, Fort Collins, Colorado.

Steminiski, 2003. July 27, 2003 Comment from J. Steminiski, Ph. D.
(EPA-HQ-OAR-2002-0064-0035 and -0043)

U.S. Economic Census, 2002a. General Summary: 2002. Subject Series.
Report No. EC02-31SG-1, October, 2005. U.S. Census Bureau.

U.S. Economic Census, 2002b. U.S. Economic Census for Island Areas,
2002. Report for Northern Marianas Islands, Rpt. No. IA02-00A-NMI, May,
2004. U.S. Census Bureau.

U.S. Economic Census, 2002c. U.S. Economic Census for Island Areas,
2002. Report for Guam, Rpt. No. IA02-00A-GUAM, March, 2005. U.S. Census
Bureau.

U.S. Economic Census, 2002d. U.S. Economic Census for Island Areas,
2002. Report for Virgin Islands, Rpt. No. IA02-00A-VI , April, 2005.
U.S. Census Bureau.

U.S. Economic Census, 2002e. U.S. Economic Census for Island Areas,
2002. Report for American Samoa, Rpt. No. IA02-00A-AS, April, 2005. U.S.
Census Bureau.

U.S. Economic Census, 2002f. U.S. Economic Census for Island Areas,
2002. Report for Puerto Rico: Manufacturing, Rpt. No. IA02-00I-PRM,
October, 2005. U.S. Census Bureau.

US EPA, 1980. Ambient Water Quality Criteria for Dichloroethylenes. EPA
440/5-80-041 October, 1980. Available at
<http://www.epa.gov/waterscience/pc/ambientwqc/dichloroethylenes80.pdf>

US EPA, 1992. Hazard Assessment Guidelines for Listing Chemicals on the
Toxic Release Inventory, Revised Draft. Washington, DC: Office of
Pollution, Prevention and Toxics. As referenced in ICF, 2004f.

US EPA, 1994b. Chemical Summary for Methyl Chloroform, prepared by
Office of Pollution Prevention and Toxics, August, 1994.

WMO, 2002: Scientific Assessment of Ozone Depletion: 2002, Global Ozone
Research and Monitoring Project -- Report No. 47, Geneva, 2003 Full
report available online at <http://esrl.noaa.gov/csd/assessments/>
(A-2001-07, II-A-20)

Wuebbles, Donald J. 2002. "The Effect of Short Atmospheric Lifetimes on
Stratospheric Ozone." Written for Enviro Tech International, Inc.
Department of Atmospheric Sciences, University of Illinois-Urbana.
(A-2001-07, II-D-29)

***Flammability and Fire Safety***

BSOC, 2000. February 1, 2000 Tabulation of Flammability Studies on
n-Propyl Bromide from the Brominated Solvents Committee, and other
information on flammability of n-propyl bromide. (A-2001-07, II-D-45)

Miller, 2003. Albemarle Corporation comments- Flash Point Data for
n-Propyl Bromide. (EPA-HQ-OAR-2002-0064-0040)

Morford, 2003a. Enviro Tech International Comment re Section IV D
Flammability with Exhibits (7/25/03) (EPA-HQ-OAR-2002-0064-0030 and
EPA-HQ-OAR-2002-0064-0031)

Morford, 2003b. Enviro Tech Int. Flammability of nPB & Comparison With
Methylene Chloride- Additional Comments on Flammability (7/29/03)
(EPA-HQ-OAR-2002-0064-0036)

Shubkin, 2003. R. Shubkin, Poly Systems, EPA received 7/23/03 Re:
Comment on Flammability of n-Propyl Bromide as Discussed in Proposed
Rule Published in Federal Register (EPA-HQ-OAR-2002-0064-0025)

Weiss Cohen, 2003. T. Weiss Cohen, Dead Sea Bromine Group,7/31/2003
Comment to Federal Register Proposed Rules of June 3, 2003, on
Protection of Stratospheric Ozone: Listing of Substitutes for
Ozone-Depleting Substances - n-Propyl Bromide
(EPA-HQ-OAR-2002-0064-0053)

***Human Health; Derivation of Workplace Exposure Limit and Community
Exposure Guideline***

ACGIH, 1991. Skin Notation Documentation for Methyl Chloride. Available
online at www.acgih.org.

ACGIH, 2005. Documentation for Threshold Limit Value for 1-Bromopropane.
2005. Available online at www.acgih.org.

Beck and Caravati, 2003. Neurotoxicity associated with 1-bromopropane
exposure.Utah Poison Control Center, University of Utah, Salt Lake City,
UT. *J Toxicology Clinical Toxicology* 41(5):729. (Abstract from
conference). 2003.

CERHR, 2002a. NTP- Center for the Evaluation of Risks to Human
Reproduction Expert Panel Report on the Reproductive and Developmental
Toxicity of 1-Bromopropane \[nPB\]. March 2002. (A-2001-07, II-A-11)

CERHR, 2002b. NTP- Center for the Evaluation of Risks to Human
Reproduction Expert Panel Report on the Reproductive and Developmental
Toxicity of 2-Bromopropane \[iPB\]. March 2002. (A-2001-07, II-A-12)

CERHR, 2003a. NTP- CERHR Monograph on the Potential Human Reproductive
and Developmental Effects of 1-Bromopropane. October 2003.

CERHR, 2003b. NTP- CERHR Monograph on the Potential Human Reproductive
and Developmental Effects of 2-Bromopropane. October 2003.

CERHR, 2004a. NTP-CERHR Expert Panel report on the reproductive and
developmental toxicity of 1-bromopropane. Center for the Evaluation of
Risks to Human Reproduction*. Repro Toxicol*. Vol.18, pp.157-188. 2004.

CERHR, 2004b. NTP-CERHR Expert Panel report on the reproductive and
developmental toxicity of 2-bromopropane. Boekelheide, et al. *Repro
Toxicol*. Vol.18, pp.189-217. 2004.

ClinTrials, 1997a. A 28-Day Inhalation Study of a VaporFormulation of
ALBTA1 in the Albino Rat. Report No. 91189. Prepared by ClinTrials
BioResearch Laboratories, Ltd., Senneville, Quebec, Canada. May 15,
1997. Sponsored by Albemarle Corporation, Baton Rouge, LA. (A-91-42,
X-A-4)

ClinTrials, 1997b. ALBTA1: A 13-Week Inhalation Study of a Vapor
Formulation of ALBTA1 in the Albino Rat. Report No. 91190. Prepared by
ClinTrials BioResearch Laboratories, Ltd., Senneville, Quebec, Canada.
February 28, 1997. Sponsored by Albemarle Corporation, Baton Rouge, LA.
(A-91-42, X-A-5)

Dunson et al, 2002. Dunson, D., Colombo, and B., Baird, D. Changes with
age in the level and duration of fertility in the menstrual cycle.
*Human Reproduction*, Vol. 17, No. 5, pp. 1399-1403, 2002.

Elf Atochem, 1995. Micronucleus Test by Intraperitoneal Route in Mice.
n-Propyl Bromide. Study No. 12122 MAS. Study Director, Brigitte
Molinier. Study performed by Centre International de Toxoicologie,
Misery, France, September 6, 1995. (A-91-42, X-A-9)

Fueta et al., 2002. Y. Fueta, K. Fukunaga, T. Ishidao, H. Hori.
Hyperexcitability and changes in activities of Ca2+/calmodulin-dependent
kinase II and mitogen-activated protein kinase in the hippocampus of
rats exposed to 1-bromopropane. 2002. *Life Sciences* 72 (2002) 521-529.

Fueta et al., 2004. Y. Fueta, T. Fukuda, T. Ishidao, H. Hori.
Electrophysiology and immunohistochemistry in the hippocampal CA1 and
the Dentate Gyrus of Rats Chronically exposed to 1-Bromopropane, a
Substitute for Specific Chlorofluorocarbons. *Neuroscience* 124 (2004)
593-603.

Honma et al., 2003. Honma, T, Suda M, Miyagawa M. "Inhalation of
1-bromopropane causes excitation in the central nervous system of male
F344 rats." Neurotoxicology. 2003 Aug; 24 (4-5):563-75.

Huntingdon Life Sciences, 2001. A Developmental Toxicity Study in Rat
Via Whole Body Inhalation Exposure. (A-2001-07, II-D-27)

ICF, 2002a. Risk Screen for Use of N-Propyl Bromide. ICF Consulting.
Prepared for U.S. EPA, May, 2002. (EPA-HQ-OAR-2002-0064-0006 through
-0012)

ICF, 2003. ICF Consulting. General Population Exposure Assessment for
N-Propyl Bromide. June 03, 2003. (EPA-HQ-OAR-2002-0064-0011)

ICF, 2004b. ICF Consulting. External Expert Review Panel on N-Propyl
Bromide. December 13, 2004.

ICF, 2006a. ICF Consulting**.** Risk Screen on Substitutes for
Ozone-Depleting Substances for Adhesive, Aerosol Solvent, and Solvent
Cleaning Applications. Proposed Substitute: n-Propyl Bromide. April 18,
2006. Attachments: A, Determination of an AEL; B, Derivation of an RfC;
C, Evaluation of the Global Warming Potential; D, Occupational Exposure
Analysis for Adhesive Applications; E, Occupational Exposure Analysis
for Aerosol Solvent Applications; F, General Population Exposure
Assessment for n-Propyl Bromide

ICF, 2006b. ICF Consulting. Revised Memorandum regarding RTI Metabolism
Study on nPB. April, 2006.

ICF, 2006c. ICF Consulting. Evaluation of Memorandum from Dr. M.
Stelljes. April, 2006.

Ichihara et al., 1998. Ichihara M., Takeuchi Y., Shibata E., Kitoh J.,
et al. Neurotoxicity of 1-Bromopropane. 1998. Translated by Albemarle
Corporation. (A-91-42, X-A-33)

Ichihara G., Jong X., Onizuka J., et al,. 1999. Histopathological
changes of nervous system and reproductive organ and blood biochemical
findings in rats exposed to 1_bromopropane. (Abstract only) Abstracts of
the 72nd Annual Meeting of Japan Society for Occupational Health. May
1999. Tokyo. (A-2001-07, II-A-15)

Ichihara G., Kitoh J., Yu, X., et al., 2000. 1-Bromopropane, an
alternative to ozone layer depleting solvents, is dose-dependently
neurotoxic to rats in long-term inhalation exposure. *Toxicol Sciences*
55:116-123. (A-2001-07, II-A-8)

Ichihara G. et al., 2002. Neurological Disorders in Three Workers
Exposed to 1-Bromopropane. *J Occu. Health* 44:1-7. (A-2001-07, II-D-64)

Ichihara et al., 2004a. G. Ichihara, W. Li, X. Ding, S. Peng, X. Yu, E.
Shibata, T. Yamada, H. Wang, S. Itohara, S. Kanno, K. Sakai, H. Ito, K.
Kanefusa, and Y. Takeuchi. A Survey on Exposure Level, Health Status,
and Biomarkers in Workers Exposed to 1-Bromopropane. *Am Jrnl of Ind
Med* 45:63--75 (2004)

Ichihara et al., 2004b. Gaku Ichihara, Weihua Li, Eiji Shibata, Xuncheng
Ding, Hailan Wang, Yideng Liang, Simeng Peng, Seiichiro Itohara,
Michihiro Kamijima, Qiyuan Fan, Yunhui Zhang, Enhong Zhong, Xiaoyun Wu,
William M. Valentine, and Yasuhiro Takeuchi. Neurological Abnormalities
in Workers of 1-Bromopropane Factory. *Env'l Health Perspectives,* 30
June 2004.

Ishidao et al., 2002. Ishidao T, Kunugita N, Fueta Y, Arashidani K, Hori
H. Effects of inhaled 1-bromopropane vapor on rat metabolism. *Toxicol
Lett*. 2002 Aug 5;134(1-3):237-43

Majersik et al., 2004. Chronic Exposure to 1-Bromopropane Associated
with Spastic Paraparesis and Distal Neuropathy: A Report of Six Foam
Cushion Gluers. Poster paper from 129th Annual Meeting of the American
Neurological Association, Toronto. October, 2004

Majersik et al, 2005. "Spastic Paraparesis and Distal Neuropathy
Associated with Chronic Exposure to 1BP," Presentation by Drs. J.
Majersik, M. Caravati, and J. Steffens at the North American Congress of
Clinical Toxicologists. September 14, 2005.

Miller, 2005. "1-Bromopropane: A Private Neurological Practice
Experience in 2000," Presentation by Dr. J. M. Miller, at the North
American Congress of Clinical Toxicologists. September 14, 2005

NAS, 1983. The National Academies of Science, *Risk Assessment in the
Federal Government: Managing the Process*, 1983. Available online at
<http://newton.nap.edu/catalog/366.html> (Executive summary in docket as
EPA-HQ-OAR-2002-0064-xxxx)

Nemhauser, 2005. "Bromopropane: A Health Hazard Evaluation Revisited"
Presentation by Dr. J. Nemhauser, U.S Public Health Service, Centers for
Disease Control & Presentation at the North American Congress of
Clinical Toxicologists. September 14, 2005.

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>.

NTP, 2003. Results of 13-week Inhalation Testing by the National
Toxicology Program. Available at
<http://ntp-apps.niehs.nih.gov/ntp_tox/>

index.cfm?fuseaction=ntpsearch.searchresults&searchterm=106-94-5

OEHHA, 2006. State Of California Environmental Protection Agency, Office
Of Environmental Health Hazard Assessment. Chemicals Known To The State
To Cause Cancer Or Reproductive Toxicity. June 9, 2006

Raymond and Ford, 2005. "Clinical Case Presentations from a Foam
Furniture Fabrication Plant in North Carolina," Presentation by Drs.
Larry Raymond and Marsha Ford at the North American Congress of Clinical
Toxicologists. September 14, 2005

Risotto, 2003. Comments of the Halogenated Solvents Industry Alliance on
nPB proposed rule. June, 2003. (EPA-HQ-OAR-2002-0064-0050)

Rodricks, 2002. October 21, 2002 remarks from Dr. J. Rodricks, Environ,
to R. Morford, Enviro Tech International concerning derivation of an OEL
for n-propyl bromide with cover letter to EPA from Enviro Tech
International (A-2001-07, II-D-65)

Rozman and Doull, 2002. "Derivation of an Occupational Exposure Limit
for n-Propyl Bromide Using an Improved Methodology" *App Occu. Env.
Hyg.* 17: 711-716 (A-2001-07, II-D-63)

Rozman and Doull, 2005. Presentation by Drs. Rozman and Doull at the
North American Congress of Clinical Toxicologists. September 14, 2005.

RTI, 2005. Report on uptake and metabolism of 1-bromopropane in rats and
mice. Research Triangle Institute report for the National Toxicology
Program. June, 2005.

Sekiguchi S, Suda M, Zhai YL, Honma T., "Effects of 1-bromopropane,
2-bromopropane, and 1,2-dichloropropane on the estrous cycle and
ovulation in F344 rats." *Toxicol Lett* 2002 Jan 5;126(1):41-9
(A-2001-07, II-D-39)

SLR International, 2001. "Inhalation Occupational Exposure Limit for
n-Propyl Bromide." Prepared for Enviro Tech International, Inc. 2001.
(A-2001-07, II-D-15)

Sohn et al., 2002. Sohn YK, Suh JS, Kim JW, Seo HH, Kim JY, Kim HY, Lee
JY, Lee SB, Han JH, Lee YM, Lee JY. "A histopathologic study of the
nervous system after inhalation exposure of 1-bromopropane in rat."
*Toxicol Lett*. 2002 May 28;131(3):195-201.

Stelljes and Wood, 2004. Stelljes, M., Wood, R. Development of an
occupational exposure limit for n-propylbromide using benchmark dose
methods. *Regulatory Toxicology and Pharmacology* 40 (2004) 136--150

Stelljes, ME, 2005. Mechanistic Hypothesis for n-Propylbromide and
Ramifications for Occupational Exposure Limit in the United States.
Technical Memorandum to EnviroTech International. 7 September, 2005.

Stump, 2005. "The Reproductive Toxicity of nPB in Rats," Presentation by
Dr Donald Stump at the North American Congress of Clinical
Toxicologists. September 14, 2005.

Swanson, M.B., J.R. Geibig, and K.E. Kelly. 2002. Alternative Adhesives
Technologies: Foam Furniture and Bedding Industries, Final Draft. Volume
2: Risk Screening and Comparison. Chapter 4: Exposure Assessment.
Produced by the University of Tennessee Center for Clean Products and
Clean Technologies under a grant from EPA's Design for the Environment
Branch, Office of Pollution and Prevention and Toxics. June 2002.
Available online at <http://eerc.ra.utk.edu/ccpct/aap1.html>.

TERA, 2004. Toxicological Excellence for Risk Assessment. Scientific
Review of 1-Bromopropane Occupational Exposure Limit Derivations --
Preliminary Thoughts and Areas for Further Analysis. 2004.

Toraason, M., Lynch, D.W., DeBorda, D.G., Singh, N., Krieg, E., Butler,
M.A.,Toennis, C.A., Nemhauser, J.B., 2006. DNA damage in leukocytes of
workers occupationallyexposed to 1-bromopropane. *Mutation Research* 603
(2006) 1--14

US EPA, 1991. Guidelines for Developmental Toxicity Risk Assessment.
U.S. Environmental Protection Agency. (A-2001-07, II-A-51)

US EPA, 1994a. U.S. Environmental Protection Agency (US EPA). 1994.
Methods for derivation of inhalation reference concentrations and
application of inhalation dosimetry. EPA/600/8-90/066F. Office of Health
and Environmental Assessment, Washington, DC. 1994. (A-2001-07, II-A-16)

US EPA, 1995a. SCREEN3 air dispersion model. (A-2001-07, II-A-53)

US EPA, 1995b. The Use of the Benchmark Dose Approach in Health Risk
Assessment. EPA/630-R-94-007. Risk Assessment Forum, Washington, DC.
(A-2001-07, II-A-17)

US EPA, 1996. Guidelines for Reproductive Toxicity Risk Assessment. U.S.
Environmental Protection Agency, Risk Assessment Forum, Washington, DC,
630/R-96/009, 1996.

US EPA, 2003. Number range CHAPTERSummary of Data on Workplace Exposure
to n-Propyl Bromide, May 21, 2003. EPA's summary of exposure data from
nPB suppliers and NIOSH. (EPA-HQ-OAR-2002-0064-0015 and
EPA-HQ-OAR-2002-0064-0016).

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

Werner, 2003. Comments from 3M on nPB proposed rule.
(EPA-HQ-OAR-2002-0064-58).

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. (II-D-10)

Yamada T. et al., 2003. Exposure to 1-Bromopropane Causes Ovarian
Dysfunction in Rats. *Toxicol Sci* 71:96-103 (A-2001-07, II-A-32)

***Decisions for Each Sector or End Use***

Amity International, 2001. Number range CHAPTERAmity Product Information
Bulletin Sheet Ref. No. 00-003: Vapor Degreasing Good Practice. 5 June
2001. (A-2001-07, II-A-18)

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.

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. Airborne Exposure Assessment of
1-Bromopropane, 1998. (A-2001-07, II-D-89)

CSMA, 1999. Comments from the Chemical Specialties Manufacturers
Association on Reconsideration of the 610 Nonessential Products Ban,
Docket A-98-31, IV-D-02. August 3, 1999.

Harper, 2005. Full citation above for "Availability" section.

ICF, 2006a. Full citation above for "Human Health" section.

Ichihara G. et al., 2002. Full citation above for "Human Health"
section.

Kassem, 2003. January 10, 2003 Letter from O. M. Kassem, Albemarle
Corporation to K. Bromberg, Small Business Administration Re: n propyl
bromine SNAP. (A-2001-07, II-D-78)

Lake City Army Ammunition Plant, 2004. March 9, 2004 Industrial Hygiene
Air Sampling Report for Normal Propyl Bromide Based Mouth Waterproofing
in Manufacture of 5.56 mm Ammunition. S.A. Hawk.

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, 1999. U.S. Dept. of Health and Human Services, Letter to Custom
Products Inc., December 1, 1999. Re: results of Dec. 1998 survey of
workplace exposure to nPB at Custom Products. (HHE Report 98-0153)
(A-2001-07, II-D-6)

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. 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>.

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>.

Raymond and Ford, 2005. Full citation above for "Human Health" section.

US EPA, 2003. Summary of Data on Workplace Exposure to n-Propyl Bromide,
May 21, 2003. EPA's summary of exposure data from nPB suppliers and
NIOSH. (EPA-HQ-OAR-2002-0064-0015 and -0016)

US EPA, 2004. US 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.

Werner, 2003. Full citation above for "Human Health" section.

Williams, 2005. Full citation above for "Availability" section.

***How did EPA choose the use conditions in the alternate proposal?***

Ensolv, 2006. Material Safety Data Sheet for Ensolv Solvents. Enviro
Tech International. February, 2006.

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.

NIOSH, 2003b. Method 1025 for 1- and 2-Bromopropane. NIOSH Manual of
Analytical Methods, 4^th^ Edition, March 15, 2003.

NIOSH, 2003c. Method 1003 for Halogenated Hydrocarbons. NIOSH Manual of
Analytical Methods, 4^th^ Edition, March 15, 2003.

***What other options did EPA consider?***

CSMA, 1999. Full citation above for "Decisions for Each Sector and End
Use" section.

ICF, 2006a. Full citation above for "Human Health" section.

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.

Kassem, 2003. Full citation above for "Decisions for Each Sector and End
Use" section.

NIOSH, 1999. Number range CHAPTERLetter from Dept. of Health and Human
Services to Marx Industries, Inc., February 1, 2000. Re: results of nPB
exposure assessment survey conducted Nov. 16-17, 1999. (A-2001-07,
II-D-6)

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>.

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>.

US EPA, 2003. Full citation above for "Decisions for Each Sector or End
Use" section***.***

Williams, 2005. Full citation above for "Availability" section.

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

Kassem, 2003. Full citation above for "Decisions for Each Sector and End
Use" section.

Tattersall, 2004. Conversation between M. Sheppard, EPA, and Tom
Tattersall, MicroCare Corp.

Ultronix, 2001. Response to questionnaire from EPA by C. Wolf, Ultronix,
2001. (A-2001-07, II-D-76)

US EPA, 2003. Full citation above for "Human Health" section.

US 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, Ph.D., M.D., and Karl K.
Rozman, Ph.D., 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, 2004g. Expert Panel Response on nPB AEL, Prepared for U.S. EPA,
December, 2004

ICF, 2004h. nPB Human Relevance, Prepared for U.S. EPA, September, 2004

ICF, 2006a. Full citation above for "Human Health" section.

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.

TERA, 2004. Full citation above for "Human Health" section.

***How can I use nPB as safely as possible?***

ACGIH, 2002. *Industrial Ventilation: A Manual of Recommended Practice
23^rd^ Edition.* American Conference of Governmental Industrial
Hygienists, Cincinnati, Ohio Available online at www.acgih.org.

[]{.mark}

**List of Subjects in 40 CFR Part 82**

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

**Protection of Stratospheric Ozone: Listing of Substitutes for
Ozone-Depleting**

**Substances--n-Propyl Bromide**

**Notice of Proposed Rulemaking**

Page 138 of [140](#End_of_document) pages

Dated:
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

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 Q to read as follows:

Subpart G - Significant New Alternatives Policy Program

\*\*\*\*\*

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

Listed in the \[**publication date of final rule**\] final rule.

AEROSOLS

UNACCEPTABLE SUBSTITUTES

  ---------- -------------------- --------------- --------------------------
  End Use    Substitute           Decision        Further Information

  Aerosol    n-propyl bromide     Unacceptable    EPA finds unacceptable
  solvents   (nPB) as a                           risks to human health in
             substitute for                       this end use compared to
             CFC-113, HCFC-141b,                  other available
             and methyl                           alternatives. nPB, also
             chloroform                           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           | Further          |
|          |            |           | Conditions    | Information      |
+----------+------------+-----------+---------------+------------------+
| Coatings | n-propyl   | A         | Use is        | EPA expects that |
|          | bromide    | cceptable | limited to    | all users of nPB |
|          | (nPB) as a | subject   | coatings at   | will adhere to a |
|          | substitute | to use    | facilities    | voluntary        |
|          | for methyl | c         | that have     | acceptable       |
|          | c          | onditions | provided EPA  | exposure limit   |
|          | hloroform, |           | information   | of 17 ppm on an  |
|          | CFC-113,   |           | demonstrating | 8-hour           |
|          | and        |           | their ability | time-weighted    |
|          | HCFC-141b  |           | to meet the   | average and      |
|          |            |           | recommended   | would comply     |
|          |            |           | workplace     | with any final   |
|          |            |           | exposure      | Permissible      |
|          |            |           | limit as of   | Exposure Limit   |
|          |            |           | \[INSERT DATE | that the         |
|          |            |           | OF            | Occupational     |
|          |            |           | P             | Safety and       |
|          |            |           | UBLICATION\]. | 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.    |
+----------+------------+-----------+---------------+------------------+

Note 1 : In accordance with the limitations provided in Section 310(a)
of the Clean Air Act (42 U.S.C. 7610(a)), nothing in this table shall
affect the Occupational Safety and Health Administrations' authority to
promulgate and enforce standards and other requirements under the
Occupational Safety and Health Act of 1970 (29 U.S.C. 651 et seq.)

Note 2: As of \[INSERT DATE OF PUBLICATION\], the Lake City Army
Ammunition Plant is the only facility that has provided information to
EPA demonstrating the facility\'s ability to meet the recommended
workplace exposure limit when using nPB in coatings.

ADHESIVES, COATINGS, AND INKS

UNACCEPTABLE SUBSTITUTES

  --------------- ------------------ -------------- -----------------------
  End Use         Substitute         Decision       Further Information

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

BILLING CODE []{#End_of_document .anchor}6560-50-P

[^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.

[^4]: See 29 CFR 1910.1052(d)(4)(i).

[^5]: Also called trichlorethene or TCE, C~2~Cl~3~H, CAS Reg. No.
    79-01-6.

[^6]: Also called PERC, tetrachloroethylene, or tetrachloroethene,
    C~2~Cl~4~, CAS Reg. No. 127-18-4.

[^7]: nPB emissions in the tropics would 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)

[^8]: The proposed WEL for nPB is lower than that for many acceptable
    solvents (HFEs, ketones, HFCs, HCFC-225ca/cb, hydrocarbons), but is
    higher or comparable to the WEL for other acceptable solvents (e.g.,
    dichlorobenzotrifluoride). However, a direct comparison between two
    compounds with different WELs does not necessarily mean that using a
    compound with a lower WEL is more risky. Risks from exposure will
    also vary due to emission controls in place, work practices,
    ventilation, rate of spraying, and vapor pressure of the solvent.

[^9]: iPB is also referred to as 2-bromopropane, 2-propyl bromide, or
    2-BP. Its CAS registry number is 75-26-3.

[^10]: The estrous cycle fulfills the same role in reproduction as the
    menstrual cycle in women.

[^11]: In addition, significant changes in the distribution of ovarian
    cell types were seen in the high dose groups (750 ppm) but were not
    counted in lower dose groups.

[^12]: Benchmark dose analysis uses mathematical models to fit
    dose-response data and identifies the "benchmark dose" associated
    with a "benchmark response" determined to be significant -- see
    EPA's Risk Assessment Forum Guidelines for Benchmark Dose Modeling
    (EPA, 2000a) and 68 FR 33292-33293 in the June NPRM on how EPA uses
    benchmark dose modeling in setting an exposure limit.

[^13]: In this analysis, the benchmark response was a 10% reduction in
    the mean number of estrous cycles, consistent with EPA guidance
    (EPA, 2000a). The BMDL for the same endpoint using a response of one
    standard deviation would be slightly higher, at 208 ppm.

[^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.

[^17]: ^7^ ^7^ Smog, also known as ground-level ozone, is produced from
    emissions of volatile organic compounds that react under certain
    conditions of temperature and light.

[^18]: 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 in addition to the 8-hr TWA limit (ACGIH, 2005; ERG,
    2004; see section IV.A.5). Additional information on these other
    samples is in the occupational exposure assessment for aerosols in
    the risk screen for nPB (ICF, 2006a).

[^19]: 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.

[^20]: 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.

[^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)).

[^22]: The action level is the exposure level that is half the 8-hour
    TWA exposure limit. In this case, the action level would be 8.5 ppm.