Number range CHAPTER**ENVIRONMENTAL PROTECTION AGENCY**

**40 CFR Part 82**

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

**RIN 2060-AO10**

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

**Substances--n-Propyl Bromide** **in Solvent Cleaning**

**AGENCY:** Environmental Protection Agency.

**ACTION:** Final Rule

**SUMMARY:** The Environmental Protection Agency (EPA) determines that
n-propyl bromide (nPB) is an acceptable substitute for methyl chloroform
and chlorofluorocarbon (CFC)-113 in the solvent cleaning sector under
the Significant New Alternatives Policy (SNAP) program under section 612
of the Clean Air Act. The SNAP program reviews alternatives to Class I
and Class II ozone depleting substances and approves use of alternatives
which do not present a substantially greater risk to public health and
the environment than the substance they replace or than other available
substitutes.

**DATES:** This final rule is effective on \[[insert date 60 days after
publication in the Federal Register]{.underline}\].

**ADDRESSES:** EPA has established a docket for this action under Docket
ID No. EPA-HQ-OAR-2002-0064. All documents in the docket are listed on
the [www.regulations.gov](http://www.regulations.gov/) web site.
Although listed in the index, some information is not publicly
available, i.e., Confidential Business Information (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 3334, 1301
Constitution Ave., NW, Washington, DC. This docket facility is open from
8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays.
The telephone number for the Public Reading Room is (202) 566-1744, and
the telephone number for the Air and Radiation Docket is (202) 566-1742.

**FOR FURTHER INFORMATION CONTACT:** Margaret Sheppard, Stratospheric
Protection Division, Office of Atmospheric Programs, Mail Code 6205J,
Environmental Protection Agency, 1200 Pennsylvania Ave., NW.,
Washington, DC 20460; telephone number (202) 343-9163; fax number (202)
343-2362, e-mail address: 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:** This action is divided into eight sections:

I.  General Information

    A.  Does this action apply to me?

    B.  What is n-propyl bromide?

    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. How does the SNAP Program list our decisions?

    D. Where can I get additional information about the SNAP Program?

    III\. What is EPA's final listing decision on nPB in solvent
    cleaning?

    IV\. What criteria did EPA use in making this final decision?

    A. Availability of alternatives to ozone-depleting substances

    B. Impacts on the atmosphere and local air quality

    C. Ecosystem and other environmental impacts

    D. Flammability and fire safety

    E. Impact on human health

    V. How is EPA responding to comments on the June 2003 Notice of
    Proposed Rulemaking?

    A. EPA's acceptability decision

    B. Toxicity

    C. Ozone depletion potential

    D. Other environmental impacts

    E. Flammability

    F. Legal authority to set exposure limits

    VI\. How can I use nPB as safely as possible?

    VII\. Statutory and Executive Order Reviews

    A. Executive Order 12866: Regulatory Planning and Review

    B. Paperwork Reduction Act

    C. Regulatory Flexibility Act

    D. Unfunded Mandates Reform Act

    E. Executive Order 13132: Federalism

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

    G. Executive Order 13045**:** Protection of Children from
    Environmental Health and Safety Risks

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

    I. National Technology Transfer and Advancement Act

    J. Congressional Review Act

VIII\. References

**I. General Information**

A. Does this action apply to me?

This final rule lists n-propyl bromide (nPB) as an acceptable substitute
when used as a solvent in industrial equipment for metals cleaning,
electronics cleaning, or precision 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 used 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. EPA also does not regulate
the use of solvents as carriers for flame retardants, dry cleaning, or
paint stripping under the SNAP program.

This final action does not address the use of n-propyl bromide as an
aerosol solvent or as a carrier solvent in adhesives or coatings. We are
issuing a proposed rule addressing these end uses in a separate *Federal
Register* action. Neither this final nor the proposed rule issue a
decision on other end uses in which nPB was submitted as an
ozone-depleting substance (ODS) substitute, such as fire suppression or
foam blowing, because of insufficient information.

Affected users under this final rule could 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.

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

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 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 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

*SIP*--state implementation plan

*SNAP*--Significant New Alternatives Policy

*STEL*- Short term exposure limit

*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

*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 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.

    C. How does the SNAP program list our decisions?

    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.

    D. 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. What is EPA's final listing decision on nPB in solvent
    cleaning?**

    The Agency is listing nPB as an acceptable substitute in metals,
    precision and electronics cleaning end uses. Based on the available
    information, we find that nPB can be used with no substantial
    increase in overall risks to human health and the environment,
    compared to other available or potentially available substitutes for
    ozone-depleting substances in these end uses.

    EPA is issuing today's listing in the form of a final rule, rather
    than in a notice of acceptability, in order to respond to the public
    comments received on a Notice of Proposed Rulemaking (NPRM) that we
    issued on June 3, 2003 (68 FR 33284). In that rule, we proposed
    listing n-propyl bromide (nPB) as an acceptable substitute for use
    in metals, precision, and electronics cleaning, and in aerosols and
    adhesives end-uses, subject to the use condition that nPB used in
    these applications contains no more than 0.05% by weight of
    isopropyl bromide. In addition, in that proposed rule, EPA indicated
    that we also would recommend that users adhere to a voluntary
    acceptable exposure limit (AEL) of 25 parts per million averaged
    over an eight-hour time-weighted average (TWA). Based on new
    information received after the close of the comment period on the
    June 2003 NPRM relevant to our proposed determinations for adhesive
    and aerosol solvent end uses in that same proposal, the Agency is
    issuing a new proposal for those end uses in a separate *Federal
    Register* action. The Agency is not including a recommended AEL in
    this final rule.

    Table 2 contains the text pertaining to nPB use in solvent cleaning
    end-uses that will be added to EPA's list of acceptable substitutes
    located on the SNAP web site at
    <http://www.epa.gov/ozone/snap/lists/index.html>. This and other
    listings for substitutes that are acceptable without restriction are
    not included in the Code of Federal Regulations because they are not
    regulatory requirements. The information contained in the "Further
    Information" column of those tables are non-binding recommendations
    on the safe use of substitutes.

    **Table 2: SOLVENT CLEANING**

    ACCEPTABLE SUBSTITUTE

+---------+----------+-------+----------------------------------------+
| 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      |
| and     | CFC-113  |       | would comply with any final            |
| pr      | and      |       | Permissible Exposure Limit that the    |
| ecision | methyl   |       | Occupational Safety and Health         |
| c       | ch       |       | Administration issues in the future    |
| leaning | loroform |       | under 42 U.S.C. 7610(a).               |
|         |          |       |                                        |
|         |          |       | nPB, also known as 1-bromopropane, is  |
|         |          |       | Number 106-94-5 in the Chemical        |
|         |          |       | Abstracts Service (CAS) Registry.      |
+---------+----------+-------+----------------------------------------+

**IV. What criteria did EPA consider in making this final
determination?**

In the original rule implementing the SNAP program (March 18, 1994; 59
FR 13044, at 40 CFR 82.180(a)(7)), the Agency identified the criteria we
use in determining whether a substitute is acceptable or unacceptable as
a replacement for class I or II compounds:

\(i\) Atmospheric effects and related health and environmental impacts;
\[e.g., ozone depletion potential\]

> \(ii\) General population risks from ambient exposure to compounds
> with direct toxicity and to increased ground-level ozone;

\(iii\) Ecosystem risks \[e.g., bioaccumulation, impacts on surface and
groundwater\];

\(iv\) Occupational risks;

\(v\) Consumer risks;

\(vi\) Flammability; and

\(vii\) Cost and availability of the substitute.

In this review, EPA considered all the criteria above. However, n-propyl
bromide is used in industrial applications such as electronics cleaning.
In those consumer products made using nPB, such as a computer, the nPB
would have evaporated long before a consumer would purchase the item.
Therefore, we believe there is no consumer exposure risk in the end uses
we evaluated for this rule.

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.

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 those specific applications.

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, while there are a number of alternatives that reduce the risks
from ozone depletion or from smog production[^1] slightly more than nPB
when used in industrial solvent cleaning equipment, 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 below, nPB used in solvent cleaning
end-uses does not pose a significantly greater risk than other
substitutes or than the ODS it is replacing in these end uses. Thus, we
are listing nPB as acceptable in metals cleaning, electronics cleaning,
and precision cleaning.

A. Availability of alternatives to ozone-depleting substances

Other alternatives to methyl chloroform and CFC-113 are available for
metals, electronics, and precision cleaning that have already been found
acceptable or acceptable subject to use conditions under the SNAP
program including: 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[^2]
(TCE), perchloroethylene[^3], 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 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)

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)[^4],
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

Use of nPB may be controlled as a volatile organic compound (VOC) under
state implementation plans (SIPs) developed to attain the National
Ambient Air Quality Standards for ground-level ozone, which is a
respiratory irritant. Users located in ozone 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 in accordance with the SIP. Companies have petitioned EPA,
requesting that we exempt nPB from regulation as a VOC. However, unless
and until EPA issues a final rulemaking exempting a compound from the
definition of VOC and states change their SIPs to exclude such a
compound from regulation, that compound is still regulated as a VOC.
Other acceptable ODS-substitute solvents that are VOCs for state air
quality planning purposes include most oxygenated solvents such as
alcohols, ketones, esters, and ethers; hydrocarbons and terpenes;
trichloroethylene; trans-1,2-dichloroethylene; monochlorotoluenes; and
benzotrifluoride. Some VOC-exempt solvents that are acceptable ODS
substitutes include HFC-245fa 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 3). 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). The LC~50~ for nPB is 67 mg/l, which is
greater than 10 mg/l. Based on EPA's criteria for listing under the
Toxics Release Inventory (US EPA, 1992), we believe that nPB would not
be sufficiently toxic to aquatic life to warrant listing under the
Toxics Release Inventory. Based on its relatively low bioconcentration
factor and log K~ow~ value, nPB is not prone to bioaccumulation. Table 3
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;
trichloroethylene, a solvent used for metals, electronics, and precision
cleaning; and methyl chloroform, an ODS that nPB would replace.

**Table 3: Ecosystem and Other Environmental Properties of nPB and Other
Solvents**

  -------------------------------------------------------------------------------------------------------------------------
  Property            Description of      Value for nPB  Value for                     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,      106 to 460 (Source: 152 (Source: US
  organic-carbon      substance tends to  ICF, 2004a)    1996)                         ATSDR, 1997)        EPA, 1994a)
  partition           stick to soil or                                                                     
  coefficient         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 speed Hydrolysis is  Photolytic decomposition,     Volatilization and  Volatilization
                      with which a        significant.   dechlorination and            biodegradation most most
                      compound breaks     Hydrolysis     biodegradation are            significant, with   significant;
                      down in the         half-life of   significant; hydrolysis not   hydrolysis          biodegradation
                      environment.        26 days        significant (Source: ATSDR,   relatively          and hydrolysis
                      (Hydrolysis         (Source: ICF,  1996)                         insignificant.      also occur
                      half-life values \> 2004a)                                       Hydrolysis          (Source: ATSDR,
                      25 weeks^\*^ are of                                              half-life of 10.7   2004)
                      concern.)                                                        to 30 months        
                                                                                       (Source: ATSDR,     
                                                                                       1997)               

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

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

  log K~ow~           Logarithm of the    2.10 (Source:  -0.48 (Source: LaGrega et     2.38 (Source:       2.50 (Source:
                      octanol/water       ICF, 2004a)    al., 2001, p. 1119)           LaGrega et al.,     LaGrega et al.,
                      partition                                                        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) 10 to 100 (Source:  \<9 (Source: US
  factor              (\>1000)^\*^        HSDB, 2004)                                  ATSDR, 1997)        EPA, 1994a)
                      indicate strong                                                                      
                      tendency for fish                                                                    
                      to absorb the                                                                        
                      chemical from water                                                                  
                      into body tissues.                                                                   
  -------------------------------------------------------------------------------------------------------------------------

^\*^ Criteria from EDSTAC, 1998.

nPB is not currently regulated as a hazardous air pollutant and is not
listed as a hazardous waste under the Resource Conservation and Recovery
Act (RCRA). nPB is not required to be reported as part of the Toxic
Release Inventory under Title III of the Superfund Amendments and
Reauthorization Act. Despite this, large amounts of nPB might be harmful
if disposed of in water. We recommend that users dispose of nPB as they
would dispose of any spent halogenated solvent (F001 waste under RCRA).
Users should not dump nPB into water, and should dispose of it by
incineration.

D. Flammability and fire safety

A number of commenters on the June 2003 proposal provided additional
information on the flammability of nPB using standard test methods for
determining flash point, such as the American Society for Testing and
Materials (ASTM) D 92 open cup, ASTM D56 Tag closed cup, and ASTM D93
Pensky-Martens closed cup methods (BSOC, 2000; Miller, 2003; Morford,
2003a, b and c; Shubkin, 2003; Weiss Cohen, 2003). We agree with the
commenters that by these standard test methods, nPB displayed no flash
point. Thus under standard test conditions, nPB is not flammable, and it
should not be flammable under normal use conditions. With its low
potential for flammability, nPB is comparable to chlorinated solvents,
HCFCs, HFEs, HFC-245fa, HFC-4310mee, and aqueous cleaners, and is less
flammable than many acceptable substitutes, such as ketones, alcohols,
terpenes, and hydrocarbons. nPB exhibits lower and upper flammability
limits of approximately 3% to 8% (BSOC, 2000). A number of other
solvents that are typically considered to be non-flammable also have
flammability limits (for example, methylene chloride, HCFC-141b, and
methyl chloroform). If the concentration of vapor of such a solvent
falls between the upper and lower flammability limits, it could catch
fire in presence of a flame. Such a situation is unusual, but users
should take appropriate precautions in cases where the concentration of
vapor could fall between the flammability limits.

E. Impact on human health

In evaluating potential human health impacts of nPB, EPA considered
impacts on both exposed workers and on the general population because we
identified these groups of people as the ones likely to be exposed to
nPB when it is used as a substitute for ozone-depleting substances. EPA
evaluated the available toxicity data using EPA guidelines to develop
health-based criteria to characterize human health risks (US EPA, 1994b.
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).

In the June 2003 NPRM, EPA proposed that an exposure limit of 25 ppm
would be protective of a range of effects observed in animal and human
studies, including reproductive and developmental toxicity,
neurotoxicity, and hepatotoxicity. Reduction of sperm motility in rats,
noted across multiple studies at relatively low exposures, was
determined to be the most sensitive effect. The Agency derived an
exposure limit of 18 ppm from a dose response relationship in male rat
offspring ("F1 generation") whose parents were exposed to nPB from prior
to mating through birth and weaning of the litters (WIL Research
Laboratories, 2001). We then proposed to adjust this value upwards to 25
ppm based on principles of risk management consistent with one of the
original "Guiding Principles" of the SNAP program (59 FR 13046, March
18, 1994). As we discussed in the June 2003 NPRM, EPA noted that
adhesives users should be able to achieve an AEL of 25 ppm and that 25
ppm was between the level based on the most sensitive endpoint (sperm
motility in the F1 offspring generation) and the second most sensitive
endpoint (sperm motility in the F0 parental generation). Following SNAP
program principles, we noted that "a slight adjustment of the AEL may be
warranted after applying judgment based on the available data and after
considering alternative derivations"(69 FR 33295) We stated further that
"18 ppm is a reasonable but possibly conservative starting point, and
that exposure to 25 ppm would not pose substantially greater risks,
while still falling below an upper bound on the occupation\[al\]
exposure limit."

As part of this final rulemaking, the Agency has reviewed both
information available at the time of the 2003 NPRM related to the health
risks associated with nPB use, as well as more recent case studies of
nPB exposures and effects in the workplace, newly published
toxicological studies, comments to the NPRM, new risk assessments on
nPB, and a new threshold limit value (TLV) issued by the American
Council of Government and Industrial Hygienists (ACGIH). The new
information is reviewed in greater detail in EPA's proposal specific to
the use of nPB in aerosol solvents, adhesives, and coatings.

Some general conclusions we draw from the new studies include:

-   New data from toxicological studies on nervous system effects remain
    inconsistent and equivocal concerning the level at which nervous
    system effects occur (Fueta et al., 2002; Fueta et al., 2004; Honma
    et al., 2003; Ishidao et al., 2002, NTP, 2003; Sohn et al. 2002,
    Wang et al., 2003).

-   Case reports of nPB exposure in the workplace indicate that severe,
    possibly irreversible, neurological effects may occur at sustained
    concentrations of approximately 100 ppm or greater (Beck and
    Caravati, 2003; Majersik et al, 2004; Majersik et al., 2005;
    Ichihara et al., 2002; Miller, 2005; Raymond and Ford, 2005). In
    other cases, similar or higher concentrations up to 170 ppm caused
    less severe nervous system effects (Nemhauser, 2005; NIOSH, 2003a;
    Ichihara, 2004a). Some neurological effects occurred in workers at
    levels of less than 50 ppm (Ichihara et al., 2004b). Because of
    design and methodological limitations, such as small numbers of
    subjects and limited exposure information, these studies do not
    provide a sufficient quantitative basis to derive an acceptable
    exposure limit.

-   Data on female rats indicate that nPB affects the maturation of
    ovarian follicles and the ovarian cycle (Yamada et al., 2003),
    consistent with previously reviewed data (WIL , 2001; Sekiguchi et
    al., 2002).

-   Some data on occupation exposure suggest that workers exposed to nPB
    may have experienced menstrual disorders (Ichihara et al., 2002;
    Ichihara et al., 2004b). However, the data are not statistically
    significant and are not sufficient to conclude that nPB exposure
    caused these female reproductive effects.

-   Data on DNA damage in workers exposed to nPB was not statistically
    significant (Toraason et al., 2006).

-   Metabolic data on mice and rats indicate some species differences.
    Metabolism of nPB appears to be primarily through cytochrome P450
    enzymes, particularly in mice; glutathione conjugation also plays a
    role, and a bigger role for rats than for mice (RTI, 2005).

These more recent studies do not cause us to change our acceptability
determination for solvent cleaning.

In addition, we considered new evaluations of the toxicity of nPB from
Stelljes and Wood (2004), Toxicological Excellence in Risk Assessment
(TERA, 2004), ICF (2004a, 2006a), and the TLV documentation from the
ACGIH (ACGIH, 2005).

-   Stelljes and Wood (2004) is similar in its results to SLR
    International (2001), a study by the same authors. EPA previously
    reviewed SLR International, 2001 in developing the June 2003 NPRM.
    Both these studies concluded with a recommended AEL of 156 ppm,
    based on male reproductive effects and uncertainty factors of 1 in
    driving the AEL. These documents assigned uncertainty factors in a
    manner inconsistent with EPA's guidance. This would result in a
    higher AEL than we would determine following the approach EPA has
    used on other chemicals, as well as an AEL that in our view would
    not sufficiently protect human health from nPB's effects because of
    multiple sources of uncertainty in available data (i.e., variability
    within the working population and differences between animals and
    humans in how nPB affects the reproductive system).

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

-   ICF (2004c, 2006b) derived an AEL for nPB based upon female
    reproductive effects. ICF (2004c, 2006b) discussed the relevant
    literature (Ichihara et al, 1999, 2002, 2004a, 2004b; Sekiguchi,
    2002; Yamada et al., 2003; WIL, 2001) and calculated mean estrous
    cycle length and the mean number of estrous cycles occurring during
    a three-week period at different exposure levels in the WIL, 2001
    2-generation study. ICF (2004c, 2006a) found statistically
    significant reductions in the number of estrous cycles in a
    three-week period, both including and excluding females that had
    stopped their estrous cycles, at 250, 500, and 750 ppm in the F0
    parental generation and at 500 and 750 ppm in the F1 generation. ICF
    (2004c, 2006a) conducted BMD modeling and calculated benchmark dose
    lowerbound (BMDL) values of the number of estrous cycles in a
    three-week period that varied from 102 to 208 ppm, depending upon
    the model used and the benchmark criteria selected. All data were
    calculated based on the mean reductions in estrous cycle number
    calculated from the WIL, 2001 study. Values were calculated for the
    F0 generation; the number of data for the F1 generation was too
    small for statistical analysis. The BMDLs that ICF calculated for
    the number of estrous cycles in a three-week period were 162 ppm and
    208 ppm, depending on the benchmark response criteria (10% change in
    response vs. one standard deviation) and using a
    linear-heterogeneous model.

-   The ACGIH issued a recommended TLV of 10 ppm (time-weighted average)
    for nPB (ACGIH, 2005). ACGIH summarized numerous studies showing
    different effects of nPB and identified no observed effect levels
    (NOELs) of 200 ppm for hepatotoxicity (ClinTrials, 1997b) and less
    than 100 ppm for developmental toxicity, as evidenced by decreased
    fetal weight (Huntingdon Life Sciences, 2001).

The Occupational Safety and Health Administration (OSHA) has not
developed a permissible exposure limit (PEL) for nPB that EPA could use
to evaluate toxicity risks[^5] from workplace exposure. In prior SNAP
reviews, EPA has used ACGIH TLVs where available in assessing a
chemical's risks and determining its acceptability if OSHA has not set a
PEL. ACGIH is recognized as an independent, scientifically knowledgeable
organization with expertise in issues of toxicity and industrial
hygiene. However, in this case, EPA believes that ACGIH's TLV for nPB of
10 ppm has significant limitations as a reliable basis for an acceptable
exposure limit, especially given the availability of other, more
comprehensive analyses described in this proposal. First, according to
the authors of the Huntingdon Life Sciences study, the decrease in fetal
weight was an artifact of sampling procedure that biased the data (test
animals were only sacrificed at the end of the day rather than at
random). The Center for the Evaluation of Risks to Human Reproduction
(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 BMDL similar to that of the CERHR expert panel
when analyzing the same data set (TERA, 2004). Further, the reference
list in the documentation on the TLV indicates that ACGIH did not review
and evaluate all the studies available prior to the development of the
recommended exposure limit. For example, key supporting articles that
reported disruption of estrous cycles (Yamada et al., 2003 and Sekiguchi
et al., 2002) were not discussed in the TLV documentation. Further,
ACGIH did not provide sufficient reasoning for the selection of the
chosen endpoint over others (e.g., reproductive toxicity and/or
neurotoxicity). The lack of discussion of applied uncertainty factors
also prevents a determination of how ACGIH arrived at a TLV of 10 ppm.
In summary, EPA is not basing its proposed acceptability determination
for nPB on the ACGIH TLV because: (1) other scientists evaluating the
database for nPB did not find the reduced pup weight to be the most
sensitive endpoint; (2) 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 female reproductive effects were omitted
from the list of references. A number of reviews of this document are
available in the public docket (ICF, 2004d; O'Malley, 2004). Despite
some flaws in its derivation, the TLV of 10 ppm is less than two-fold
lower than the low end of the range of acceptable exposure levels based
on the most sensitive reproductive endpoints (see below). This small
difference is well within the uncertainty we see when extrapolating a
benchmark dose from an experimental study in rats to an occupational
exposure limit in humans.

We summarize the data for a number of end points found in these analyses
in Table 4 below. We examined these data to assess the acceptability of
nPB use in the metals, electronics, and precision cleaning end uses
reviewed in this final rule**.** These data indicate that, once
uncertainty factors are applied consistent with EPA guidelines, the
lowest levels for acceptable exposures would be derived for reproductive
effects[^6]. The data also indicate that a level sufficient to protect
against male reproductive effects (e.g., reduced sperm motility) would
be in a range from 18 to 30 ppm, in the range of 17 to 22 ppm to protect
against female reproductive effects (e.g., estrous cycle length), and at
approximately 20 ppm for effects related to reproductive success (live
litter size).

Table 4: Summary of endpoints using benchmark response modeling

+-------------------+------------------------+-----------+------------+
| **Endpoint^a^**   | **Study**              | **        | **Human    |
|                   |                        | BMDL^b^** | Equivalent |
|                   |                        |           | Con        |
|                   |                        | **(ppm)** | centration |
|                   |                        |           | (HEC)^c^** |
|                   |                        |           |            |
|                   |                        |           | **(ppm)**  |
+-------------------+------------------------+-----------+------------+
| *Liver            |                        |           |            |
| Effects*^d^       |                        |           |            |
+-------------------+------------------------+-----------+------------+
| **Liver           | WIL, 2001 as analyzed  | 110       | 116        |
| vacuolation in    | in ICF, 2002           |           |            |
| males**           |                        |           |            |
|                   |                        |           |            |
| **(F~1~ offspring |                        |           |            |
| generation)**     |                        |           |            |
+-------------------+------------------------+-----------+------------+
| **Liver           | WIL, 2001 as analyzed  | 143       | 150        |
| vacuolation in    | in ICF, 2002           |           |            |
| males (F~0~       |                        |           |            |
| parent            |                        |           |            |
| generation)**     |                        |           |            |
+-------------------+------------------------+-----------+------------+
| **Liver           | ClinTrials, 1997b as   | 226       | 170        |
| vacuolation**     | analyzed in ICF, 2002  |           |            |
|                   | and Stelljes & Wood,   |           |            |
|                   | 2004                   |           |            |
+-------------------+------------------------+-----------+------------+
| *Reproductive     |                        |           |            |
| Effects---Male*   |                        |           |            |
+-------------------+------------------------+-----------+------------+
| **Sperm motility  | WIL, 2001 as analyzed  | 169       | 177        |
| (F~1~ offspring   | in ICF, 2002           |           |            |
| generation)**     |                        |           |            |
+-------------------+------------------------+-----------+------------+
|                   | WIL, 2001 as analyzed  | 156       | 164        |
|                   | in Stelljes & Wood,    |           |            |
|                   | 2004                   |           |            |
+-------------------+------------------------+-----------+------------+
| **Sperm motility  | WIL, 2001 as analyzed  | 282       | 296        |
| (F~0~ parent      | in ICF, 2002           |           |            |
| generation)**     |                        |           |            |
+-------------------+------------------------+-----------+------------+
|                   | WIL, 2001 as analyzed  | 263       | 276        |
|                   | in Stelljes & Wood,    |           |            |
|                   | 2004                   |           |            |
+-------------------+------------------------+-----------+------------+
| **Prostate weight | WIL, 2001 as analyzed  | 190       | 200        |
| (F~0~ parent      | in TERA, 2004          |           |            |
| generation)**     |                        |           |            |
+-------------------+------------------------+-----------+------------+
| **Sperm count**   | Ichihara et al., 2000b | 232       | 325        |
|                   | as analyzed in         |           |            |
|                   | Stelljes & Wood, 2004  |           |            |
+-------------------+------------------------+-----------+------------+
| **Sperm           | WIL, 2001 as analyzed  | 296       | 311        |
| deformities (F~0~ | in Stelljes & Wood,    |           |            |
| parent            | 2004                   |           |            |
| generation)**     |                        |           |            |
+-------------------+------------------------+-----------+------------+
| *Reproductive     |                        |           |            |
| Effects---Female* |                        |           |            |
+-------------------+------------------------+-----------+------------+
| **Number of       | WIL, 2001 as analyzed  | 162       | 170        |
| estrus cycles     | in ICF, 2006a          |           |            |
| during a 3 week   |                        |           |            |
| period (F~0~      |                        |           |            |
| parent            |                        |           |            |
| generation)**     |                        |           |            |
+-------------------+------------------------+-----------+------------+
|                   | WIL, 2001 as analyzed  | 208       | 218        |
|                   | in ICF, 2006a          |           |            |
+-------------------+------------------------+-----------+------------+
| **Estrous cycle   | WIL, 2001 as analyzed  | 400       | 420        |
| length (F~1~      | in TERA, 2004          |           |            |
| offspring         |                        |           |            |
| generation)^d^**  |                        |           |            |
+-------------------+------------------------+-----------+------------+
| **Estrous cycle   | WIL, 2001 as analyzed  | 210       | 220        |
| length (F~0~      | in TERA, 2004          |           |            |
| parent            |                        |           |            |
| generation)^e^**  |                        |           |            |
+-------------------+------------------------+-----------+------------+
| **No estrous      | WIL, 2001 as analyzed  | 180       | 189        |
| cycle incidence   | in TERA, 2004          |           |            |
| (F~1~ offspring   |                        |           |            |
| generation)**     |                        |           |            |
+-------------------+------------------------+-----------+------------+
| **No estrous      | WIL, 2001 as analyzed  | 480       | 504        |
| cycle incidence   | in TERA, 2004          |           |            |
| (F~0~ parent      |                        |           |            |
| generation)**     |                        |           |            |
+-------------------+------------------------+-----------+------------+
| *Reproductive     |                        |           |            |
| Effec             |                        |           |            |
| ts---Reproductive |                        |           |            |
| Success*          |                        |           |            |
+-------------------+------------------------+-----------+------------+
| **Decreased live  | WIL, 2001 as analyzed  | 190       | 200        |
| litter size (F~1~ | in TERA, 2004          |           |            |
| offspring         |                        |           |            |
| generation)**     |                        |           |            |
+-------------------+------------------------+-----------+------------+
| **Decreased live  | WIL, 2001 as analyzed  | 170       | 179        |
| litter size (F~2~ | in TERA, 2004          |           |            |
| offspring         |                        |           |            |
| generation)**     |                        |           |            |
+-------------------+------------------------+-----------+------------+
| **Pup weight      | WIL, 2001 as analyzed  | 180       | 189        |
| gain, post-natal  | in TERA, 2004          |           |            |
| days 21 to 28     |                        |           |            |
| (F~1~ offspring   |                        |           |            |
| generation)**     |                        |           |            |
+-------------------+------------------------+-----------+------------+
| *Developmental    |                        |           |            |
| Effects*          |                        |           |            |
+-------------------+------------------------+-----------+------------+
| **Fetal body      | WIL, 2001 as analyzed  | 310       | 326        |
| weight**          | in TERA, 2004          |           |            |
+-------------------+------------------------+-----------+------------+
| **Fetal body      | WIL, 2001 as analyzed  | 305       | 320        |
| weight**          | in CERHR, 2002a        |           |            |
+-------------------+------------------------+-----------+------------+
| *Nervous System   |                        |           |            |
| Effects*          |                        |           |            |
+-------------------+------------------------+-----------+------------+
| **Hindlimb        | Ichihara et al, 2000a  | 214       | 300        |
| strength**        | as analyzed in         |           |            |
|                   | Stelljes and Wood,     |           |            |
|                   | 2004                   |           |            |
+-------------------+------------------------+-----------+------------+

^a^ Unless explicitly stated, data are from a parental generation. Of
the studies analyzed, only the WIL, 2001 study has multiple generations
to be analyzed.

^b^ The benchmark response value represents a specified level of excess
risk above a control response.

^c^ When considering workplace exposures, the human equivalent
concentration is the BMDL, adjusted to apply to a 40-hour work week in
which workers are exposed for 8 hours a day for five days per week.
Animals in the WIL, 2001 study were exposed for 6 hours a day, 7 days a
week. Animals in the Ichihara, 2000a and 2000b studies were exposed for
8 hours a day, 7 days a week. Animals in the ClinTrials, 1997b study
were exposed for 6 hours a day, 5 days a week.

^d^ After applying an uncertainty factor of 3 for animal to human
extrapolation, acceptable levels of exposure to protect against liver
effects would be in the range of 39 to 57 ppm.

^e^ Omits data from those animals that have stopped estrous cycling
altogether (TERA, 2004).

These more recent evaluations do not change EPA's acceptability
determination for solvent cleaning. As discussed below, users of solvent
cleaning equipment are reliably able to achieve exposure levels well
below our proposed AEL of 25 ppm in the June 2003 NPRM and therefore we
expect nPB users in the metals, electronics, and precision cleaning end
uses to be able to achieve acceptable exposure levels. 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 18 ppm in 81% of these samples, and below 10 ppm in
roughly 70% of these samples (US EPA, 2003).

Based on review of the previously available information and information
submitted in comments to the NPRM, the Agency believes that its
derivation of 18 ppm as a starting point in the development of a
recommended acceptable exposure level is still valid. For purposes of
assessing the acceptability of nPB use in solvent cleaning applications,
the Agency evaluated whether exposure levels expected to result from
solvent cleaning would approach either the 2003 proposed recommended AEL
of 25 ppm, or the more conservative starting point of 18 ppm which was
derived from the Agency's original risk analysis. We also evaluated any
potential risks to the general population associated with nPB use as a
solvent.

> 1\. Workplace Risks

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 well below 25 ppm, the proposed AEL in the 2003 NPRM,
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 18 ppm in 81% of these samples, and
below 10 ppm in roughly 70% of these samples (US EPA, 2003).

One nPB supplier provided evidence that on the few occasions when nPB
concentrations from vapor degreasers were higher than the company's
recommended AEL 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 acceptable
exposure levels 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 workplace exposure limit that will
protect human health 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 users of nPB as an
industrial solvent for metals cleaning, electronics cleaning, and
precision cleaning are likely to be exposed to concentrations of nPB
well below the proposed AEL of 25 ppm from the 2003 NPRM.

> 2\. General Population Risks

In the 2003 NPRM, the Agency provided analyses demonstrating that people
living in the immediate vicinity of a facility using nPB in spray
adhesives would have exposures below the community exposure guideline of
1 ppm (68 FR 33300-33301). The community exposure guideline was derived
considering both sperm motility and liver effects in the WIL (2001)
2-generation study using EPA's reference concentrations (RfC) guidelines
(US EPA, 1994b). Since the general population would not be exposed in
excess of the community exposure guideline from a highly emissive
application, the less emissive uses such as metals, electronics, and
precision cleaning would create insignificant exposures (well below 1
ppm). Thus, we believe that proper use of nPB in solvent cleaning would
not pose measurable risks to the general population.

**V. How is EPA responding to comments on the June 2003 NPRM?**

In this section, EPA responds to comments on the major issues in the
June 2003 NPRM. A complete response to comments is in docket
EPA-HQ-OAR-2002-0064.

A. EPA's acceptability decision

There was no consensus among commenters about whether EPA should find
nPB acceptable, acceptable subject to use conditions, or unacceptable in
the various end uses listed in the proposal. Some commenters raised
concerns about specific end uses, particularly aerosols and adhesives.
Others supported finding nPB acceptable in solvents cleaning and in
adhesives. We are not taking final action in this rule with respect to
nPB as a substitute in aerosols or adhesives. We will respond to any
comments regarding those end uses at the time we take final action for
aerosols and adhesives.

*Comment:* Several commenters supported EPA's proposed approval of nPB
under the SNAP program in various end uses. In contrast, two commenters
opposed EPA's proposed acceptability determination in all end uses,
including solvent cleaning, citing concerns about exposure and the
toxicity of nPB. Another commenter stated that applications cited in the
proposal (e.g., electronics and metals cleaning, label removal and spray
cleaning) are not suitable for use of nPB. This commenter reasoned that
if nPB provides unique performance characteristics, its uses should be
limited to non-emissive and low-volume applications. A commenter from a
company that markets nPB as a chemical intermediate but not as a
solvent, noted that his company recognizes the health concerns
associated with nPB, and thus his company continues to prohibit the sale
of nPB to customers with dispersive uses. Another commenter stated that
nPB is dangerous to the ozone layer and workers and urged EPA to find a
safe substitute.

*Response:* EPA believes nPB may be found acceptable under the SNAP
program only in those end uses where it has been shown to be used
safely, as compared with other substitutes that are currently or
potentially available. We find this to be the case for metals cleaning,
electronics cleaning, and precision cleaning.

*Comment:* Several commenters agreed with EPA's proposed approval for
nPB in metal cleaning, electronics cleaning, and precision cleaning end
uses. One specifically reported that his company's industrial hygiene
program for nPB-based solvents in metal and electronics cleaning has
conducted extensive air sampling, and that the majority of the samples
have shown values well below 25 ppm. This commenter also noted that, in
those few workplaces where higher levels were found, adoption of
recommended workplace ventilation and handling practices produced
acceptable subsequent sample values. Thus, this commenter believes that
exposures can be controlled to protective levels.

One commenter expressed concerns over the approval of nPB as acceptable
for use in solvent cleaning, maintaining that toxicity data is
insufficient to be convincing that long-term effects will not be a
concern. Two other commenters did not support EPA's proposal to find nPB
acceptable. One of the commenters concurred with EPA that exposures from
manual wipe cleaning will not be acceptable and that nPB should not be
used in such operations. Another commenter opposed EPA's proposed
acceptability determination for solvent cleaning, stating that use of
nPB in applications such as electronics and metals cleaning, label
removal, and spray cleaning is not appropriate.

*Response:* EPA agrees with those commenters who said nPB should be
acceptable for use in metal cleaning, electronics cleaning, and
precision cleaning. By our definition of the solvent cleaning sector,
such users are cleaning using industrial cleaning equipment. For an
organic solvent, this means a vapor degreaser or an automated cold
cleaning machine. Emissions from vapor degreasers can be controlled both
through improving equipment (increasing the freeboard, adding cooling
coils, or adding a lift that raises cleaned pieces slowly) and through
improved work practices (leaving the vicinity of the vapor degreaser
when done with work, tipping work-pieces so they do not catch solvent,
or lifting cleaned pieces out slowly).

In solvent cleaning equipment, exposure data show that nPB can meet an
exposure level well below 25 ppm, even at levels of 5 ppm or less, the
majority of the time (USEPA 2003; ICF, 2006a). Concentrations of nPB
emitted from industrial solvent cleaning equipment were measure to be
below 25 ppm in roughly 88 % of more than 500 samples, below 18 ppm in
81% of these samples, and at or below 5 ppm in 56% of these samples (US
EPA, 2003). In cases where exposure levels are higher, there are simple,
cost-effective changes that can be made to reduce emissions (Kassem,
2003). We agree that manual cleaning using nPB is inappropriate, because
of the difficulty of controlling emissions, but manual cleaning is
currently beyond the scope of the SNAP Program. EPA plans to address
spray cleaning using aerosols in a new proposal.

B. Toxicity

1\. Health Endpoints

*Comment:* A number of commenters on the June 2003 NPRM suggested that
EPA should consider neurotoxicity as the endpoint in deriving the AEL
for nPB (Linnell, 2003; Werner, 2003; Rusch and Bernhard, 2003; Rusch,
2003). In particular, they requested that EPA consider the study
conducted by Wang (2003) and epidemiological data on neurotoxic effects
of nPB.

*Response:* Recent data collected from occupational settings indicate
that severe, possibly irreversible, neurological effects may occur at
sustained concentrations of approximately 100 ppm or greater (Beck and
Caravati, 2003; Majersik, 2004; Majersik, 2005), with variability in
effects observed in different studies, although in most cases exposures
may have been much higher. Other studies with human data are discussed
above in section IV.E. Because of design and methodological limitations,
such as small numbers of subjects and limited exposure information, none
of the recent studies individually provides a sufficient quantitative
basis to derive an AEL.

In the study on rats by Wang et al. (2003), measurements found a
decrease in enzymes in the spinal cord and brain at 200, 400, and 800
ppm, but the animals displayed no physical or behavioral changes.
Because of the lack of physical symptoms or behavioral changes, EPA does
not believe that the decrease in enzyme levels in the central nervous
system are toxicologically relevant. Other studies examining
neurological effects of nPB showed those effects to be transient and
reversible at and above 200 ppm (Ichihara et al., 2000a). Exposures of
200 ppm and above for three weeks had no effect on memory, learning
function, or coordination of limbs (Honma, 2003); the effect of
spontaneous locomotor activity seen in this study at 50 ppm and above
was not considered adverse by the authors. In other studies,
neurological effects were absent after extended periods of
exposure---after 28 days of exposure at concentrations \> 400 ppm
(ClinTrials, 1997a) and after 90 days of exposure at concentrations up
to 600 ppm (ClinTrials, 1997b). Thus, although neurological effects have
been associated with nPB exposure, the data are currently insufficient
to quantify and set an AEL based on this endpoint. More recent data does
not change EPA's acceptability determination for solvent cleaning.

*Comment:* One commenter on the June 2003 NPRM requested that EPA
evaluate a study by Yamada et al (2003), a study published just prior to
the June 2003 NPRM.

*Response:* EPA reexamined Yamada et al., 2003 and re-evaluated the
literature (Ichihara et al., 1999, 2002, 2004a,b; Sekiguchi, 2002,
Yamada et al., 2003; WIL, 2001). Multiple benchmark analyses found a
statistically significant decrease in the number of estrous cycles and
increase in estrous cycle length associated with nPB exposure,
consistent with other reproductive endpoints, namely reductions in sperm
motility, decreased live litter size, and change in prostate weight
(ICF, 2002a; ICF, 2006a; Stelljes and Wood, 2004; TERA, 2004). These
more recent evaluations, which could lead to an HEC of 170 ppm and an
AEL of 17 ppm, do not change EPA's acceptability determination for
solvent cleaning, since the evidence supports the ability of users in
this end use to consistently meet such a level.

*Comment:* Some commenters stated that data from the F1 generation is
inappropriate for calculating occupational exposure, citing statements
from some toxicologists that use of effects on adult F1 generation
animals is inappropriate. They also stated that EPA has not required
this for other chemicals and that the resulting value is more
conservative than what is normal and appropriate for industrial
toxicology (Morford, 2003d and e; Ruckriegel, 2003). One commenter
claims that because EPA's review of nPB differed from EPA's review of
other SNAP alternatives, the process violates equal protection (Morford,
2003d and e). Others stated that sperm motility effects on the F1
generation are appropriate to consider (Risotto, 2003; Farr, 2003),
particularly because of the potential for *in utero* effects and because
of the consistent presence of these reproductive effects in both
generations and at multiple levels.

*Response:* EPA is not finalizing a specific AEL for the purposes of
this final rule. EPA acknowledges that using data from the F1 offspring
generation may be conservative because the pups in the F1generation were
exposed to nPB between weaning and sexual maturity (WIL, 2001). During
occupational exposure, this period of exposure would not occur because
children under age 16 are not allowed to work in industrial settings.
However, EPA believes that because of the potential for *in utero*
effects that would only be seen in the offspring generation, looking
only at the F0 parental generation could underestimate the adverse
health impacts of a chemical. Therefore, it was appropriate for us to
consider effects seen in both the F0 parental generation and the F1
offspring generation. Further, effects on sperm motility in the parental
and offspring generations are seen at levels generally consistent with
multiple reproductive effects seen in both generations and both sexes
exposed to nPB, such as estrous cycle length, lack of estrous cycling,
the number of estrous cycles in a given period of time, fertility
indices, and the number of live pup births (TERA, 2004; ICF, 2006a; SLR
International, 2001).

We also note that different substances have different toxicological
effects and those effects must be considered based on the best
scientific information and methodologies available. It is incorrect to
claim that such reviews, which focus on the effects of different
substances, resulted in disparate treatment of nPB[^7].

2\. Adjustments to Acceptable Exposure Level Based on Risk Management
Principles

In the 2003 NPRM, EPA derived 18 ppm as the starting point for an
acceptable exposure level based on reduced sperm motility in the
offspring generation of animals exposed to nPB (WIL, 2001). Following a
SNAP program principle that alternatives should be restricted only where
it is "clearly more harmful to human health and the environment than
other alternatives," we noted that "a slight adjustment of the AEL may
be warranted after applying judgment based on the available data and
after considering alternative derivations"(69 FR 33294, 33295). The
Agency proposed an upward adjustment of the AEL to 25 ppm based on
principles of risk management, and based, among other things, on a
determination that 25 ppm was between the level based on the most
sensitive endpoint (sperm motility in the F1 offspring generation) and
the second most sensitive endpoint (sperm motility in the F0 parental
generation). We stated further that "18 ppm is a reasonable but possibly
conservative starting point, and that exposure to 25 ppm would not pose
substantially greater risks, while still falling below an upper bound on
the occupation\[al\] exposure limit."

*Comment:* Commenters responded that: 1) the SNAP program does not
create a presumption in favor of substances that are already available
on the market, especially where other alternatives exist (Linnell, 2003;
Werner, 2003); 2) EPA's AEL derivation of 18 ppm is not conservative
enough (Werner, 2003; Risotto, 2003) and further adjustment upward
further reduces protection; 3) the data do not support adjusting the AEL
upward (EPA-HQ-OAR-2002-0064-0003); 4) EPA should first use the same
methodology in establishing an AEL as for other chemicals to ensure that
the program's guiding principle in comparing risks is not compromised
(Werner, 2003); and 5) EPA should reconsider whether industrial
exposures consistently occur or can be controlled at 25 ppm (Werner,
2003). No commenters specifically supported adjusting the AEL upward.

*Response:* EPA is not finalizing a specific AEL for the purposes of
this final rule. In a separate proposed rulemaking for the aerosol,
adhesive and coatings end uses, we will be providing the public an
opportunity to comment on a range of exposure level values that are
comparable to the levels discussed in the June 2003 proposal (69 FR
33295) that the Agency would consider to be acceptable. Because we have
concluded that end users in the solvent sector are routinely able to
meet even the lowest exposure level we considered recommending (US EPA,
2003), we do not need to make a final determination as to the
appropriate level for purposes of this rulemaking.

3\. Uncertainty Factors

According to EPA risk assessment guidance for RfC (EPA 1994a),
uncertainty factors of up to 10 may be applied to the "human equivalent
concentrations (which accounts for worker exposure patterns of 8 hours
per day for 5 days a week), 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 BMD; or

(5) An incomplete database of toxicity information exists for the
    chemical.

*Comment:* Some commenters on the June 2003 NPRM stated that EPA should
use an uncertainty factor of 1 or 2 to extrapolate from animals to
humans (Weiss Cohen, 2003), while others suggested uncertainty factors
of 2 or 3 for pharmacokinetics, or an overall uncertainty factor of 10
for rat to human extrapolation because of a lack of information on the
metabolism and mode of action of nPB and because the rat is an
insensitive model for effects on male reproduction in humans (Werner,
2003; Rusch and Bernhardt, 2003).

*Response*: 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. 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[^8] and the second to
account for differences in pharmacokinetics[^9] 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 \[EPA,1994a, pp. 1-6,
4-73\]. 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.) In general, EPA's RfC guidelines state that for the
uncertainty factor extrapolating from animal to human data, "Use of a 3
is recommended with default dosimetric adjustments." (US EPA, 1994b, p.
4-73). By EPA RfC guidelines (US EPA, 1994b), no adjustment for
differences in pharmacokinetics is necessary in this instance because
the blood/air partition coefficient[^10] 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. EPA has
seen no data to indicate that (1) the toxicity is not directly related
to the inhaled parent compound in the arterial blood, or that (2) the
critical metabolic pathways do not scale across species, with respect to
body weight, in the same way as the ventilation rate. 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 and an uncertainty factor of 3 for differences
between animals and humans.

Recent studies provide additional data regarding metabolism of nPB in
rats and mice (RTI, 2005), but data on human metabolism are still
lacking. One analysis of these metabolic data suggested that mice are
less sensitive to the effects of nPB than rats and hypothesized that
humans would also be less sensitive than rats (Stelljes, 2005). This
analysis makes numerous assumptions about toxic nPB metabolites and
metabolic activation pathways that have not been confirmed by
experimental data. A review of this analysis is available in the public
docket (ICF, 2006c). Despite the difference in metabolic pathways for
nPB in mice and rats (RTI, 2005), EPA finds no significant
species-specific differences in toxicity exist between rats and mice at
inhaled concentrations \<500 ppm for 13 weeks (NTP, 2003; ICF, 2006c).
However, these metabolic and subchronic inhalation studies conducted
under the National Toxicology Program did not specifically examine for
reproductive toxicity or nPB metabolism in target organs that control
reproductive function. In summary, there is little available data about
the metabolic activation or reactive metabolites responsible for
reproductive toxicity in rodents. Similarly, for nPB, there is little
information available about differences and similarities between rodents
and humans. Given this circumstance, EPA assumes, in the absence of
evidence to the contrary, that nPB toxicity is directly related to the
inhaled parent compound in the arterial blood and that the critical
metabolic pathways scale across species in a manner similar to the
ventilation rate (US EPA, 1994b). Therefore, the Agency applied an
uncertainty factor of 1 to account for interspecies differences in
pharmacokinetics.

Given the available data on the blood/air partition coefficient and EPA
RfC guidance in the absence of other information, EPA is applying the
same rationale used for other compounds reviewed under EPA's SNAP
program with a comparable amount of data where an uncertainty factor of
1 for pharmacokinetics was applied. To account for uncertainty in
pharmacodynamics of nPB, EPA is applying the default uncertainty factor
of 3. This follows the procedures in EPA's RfC guidelines for situations
where there are no data to compare pharmacodynamics in rats versus
humans (US EPA, 1994b). Recently published data on humans and rodents do
not decrease the uncertainty regarding the pharmacodynamics of nPB;
therefore, modification of the uncertainty factor of 3 for differences
between species was not justified.

*Comment:* One commenter stated that EPA did not cite any data that
describes the size, condition, or existence of a subpopulation of men
especially sensitive to the effects of nPB. In addition, this commenter
asserted that sensitive populations are not traditionally considered
when deriving an OEL, and that EPA has never mentioned a concern with
sensitive subpopulations in previous SNAP reviews. Another commenter
said that there is no evidence to support the assertion that nPB
exposure below a 100 ppm average will further reduce sperm count or that
the removal of nPB exposure will improve sperm count.

*Response:* EPA disagrees with the comments. There are preexisting
reproductive conditions as well as significant variability in fertility
among otherwise healthy adults in the workplace. Both male and female
reproduction have been shown to be adversely affected by aging, with
effects on the ovarian cycle and on sperm motility as major factors
changing with increasing age for women and men, respectively (Dunson et
al., 2002). Adding damage from other factors, such as smoking or
occupational exposure to chemicals such as nPB, therefore, can
potentially harm an individual's ability to reproduce further (Dunson,
et al. 2002). EPA did not issue a proposal based on sperm count, so that
comment is not relevant to this rule. In addition, we note that EPA has
used uncertainty factors in the past to protect sensitive subpopulations
on other chemicals reviewed under the SNAP program (e.g.,
trifluoroiodomethane at 60 FR 31092, 61 FR 25585 and IoGas™ Sterilant
Blends at 69 FR 58903). For deriving AELs from health endpoints such as
liver effects and neurotoxicity, the SNAP program typically has assigned
an uncertainty factor of 1 for sensitive subpopulations because we
assume that individuals who are especially susceptible to these effects
will have greater difficulty working than most people. However, there is
no connection between the ability to reproduce and the ability to work
in the industrial sectors discussed in this rule. Thus, we find it
appropriate to require an uncertainty factor greater than 1 for
reproductive effects for variability within the working population.

*Comment:* Some commenters said that an uncertainty factor of 1 is
appropriate for variability within the working population because
sensitive subpopulations will not be present in the working population
(Stelljes, 2003, Morford, 2003e). Other commenters stated that there
will be very little difference in variability between the worker
population and the general population and that it is unclear why EPA
selected an uncertainty factor of 3 instead of 10 (Werner, 2003).
Commenters suggested uncertainty factors for variability in the working
population of 1, 2, and 5 (Stelljes, 2003, Weiss Cohen, 2003, Werner,
2003).

*Response:* EPA disagrees with the commenters. EPA's RfC guidelines
recommend an uncertainty factor of 10 to account for intraspecies
variability within the general population. However, in developing an
AEL, EPA's focus is on worker exposure, which excludes some particularly
vulnerable populations, such as children, most adolescents, and the
elderly. Thus, we believe that a full uncertainty factor of 10, as for
the general population, may be higher than necessary to protect workers.
Certain individuals in the general population but not in the working
population that might be particularly vulnerable would include children
and adolescents under age 16 and individuals with immune deficiency
disorders. However, because of variability in reproductive function due
to factors present among workers, such as aging, smoking, and sexually
transmitted disease (Dunson et al., 2002), and because there is no
screening of workers that would make workers more likely to have healthy
reproductive systems than non-workers of the same age, we believe than
an uncertainty factor of 1 is not sufficiently protective. Under EPA
guidelines, 3 is a default value for an uncertainty factor where there
is indication that a value less than an order of magnitude (10) but
greater than one is appropriate, and where the available data are not
sufficiently quantified to select a specific value.

4\. Other Analyses of nPB's Toxicity

*Comment:* One commenter stated that documents by Drs. Doull, Rozman,
Stelljes, Murray, Rodricks, and the KS Crump Group were not acknowledged
(Morford, 2003d,e, and f). Another commenter requested that EPA take
into account the scientific presentations presented by Drs. Doull,
Rozman and Stelljes and mentions a review by Dr. Rodricks (Weiss Cohen,
2003).

*Response:* EPA specifically mentioned and responded to the occupational
exposure limit recommendations from Drs. Rozman, Doull, and Stelljes in
the preamble to the June 2003 NPRM at 68 FR 33298-33299. In addition,
EPA included more detailed written responses to these derivations and
the evaluation by Dr. Rodricks in the online docket prior to proposal
(EPA-HQ-OAR-2002-0064-0017, -0018, and -0019). Here are abbreviated
responses to the various documents cited by the commenter:

-   Drs. Doull and Rozman's letter dated August 24, 2001, stating that a
    two-generational reproductive study is not appropriate (Docket
    A-2001-07, item II-D-26)---Drs. Doull and Rozman do not provide a
    rationale for their statement. Their statement is in conflict with
    their AEL derivation, in which they consider use of the F1
    generation of the WIL Laboratories two-generation study. As
    discussed above in section V.B.1, EPA believes that data from a
    two-generation reproductive study are appropriate in developing a
    guideline for the workplace in order to assure that workers and
    their children are protected from any adverse health effects of
    workplace exposure, including exposure *in utero*. We acknowledge
    that this value may be more conservative than considering data only
    from the parental generation.

-   Drs. Doull and Rozman's critique of ICF's AEL derivation
    (II-D-41b)\-- Drs. Doull and Rozman's primary stated reason for
    rejecting ICF Consulting's evaluation is that it does not reflect
    their own AEL derivation. They reiterate that they find
    neurotoxicity to be the appropriate basis for an AEL without
    addressing the reasons that ICF's derivation provides for finding
    reproductive toxicity to be of greater concern than neurotoxicity.
    We disagree with Doull and Rozman's conclusion that neurotoxicity is
    the more appropriate endpoint for several reasons: 1) the human data
    are insufficient to draw conclusions because of a small number of
    subjects, limited exposure information, and lack of statistical
    significance; 2) the animal data on neurotoxicity are inconsistent
    and equivocal concerning the level at which nervous system effects
    occur, and they indicate that neurotoxic effects may be reversible;
    and 3) neurotoxicity is a less sensitive endpoint than reproductive
    effects. However, if we had used neurotoxicity as the endpoint for
    an AEL, we would have reached the same acceptability determination
    for solvent cleaning.

> The basis of EPA's June 2003 NPRM is different from either one of
> these documents because it uses a different endpoint from Doull and
> Rozman's derivation (2001) and an uncertainty factor of 3 instead of 2
> to 3 for variability within the working population (Doull and Rozman,
> 2001; ICF, 2002a). According to EPA guidance on establishing
> uncertainty factors, if a uncertainty factor is between 1 and 10 and
> the data are not sufficient to quantify the uncertainty between those
> values, the default uncertainty factor to be used is 3 (US EPA,
> 1994b).

-   Drs. Rozman and Doull's derivation of an AEL (II-D-63)---EPA
    discussed our evaluation of this document at length in the preamble
    at 68 FR 33298. In particular, we disagree with Rozman and Doull's
    selection of the most sensitive endpoint. Rozman and Doull concluded
    that reproductive toxicity should not be considered the most
    sensitive endpoint, stating that a National Institute for
    Occupational Safety and Health (NIOSH) evaluation found that no
    human beings at a facility using nPB-based adhesives experienced
    reproductive health effects from the nPB. However, the NIOSH study
    in fact concluded that the survey questions would not be sufficient
    to determine if there were reproductive health effects, which is
    significantly different from saying that there was no health effect.
    The expert panel for the CERHR looked at the NIOSH report and a wide
    range of human and animal studies on nPB; in contrast to Rozman and
    Doull, the expert panel concluded that there was insufficient
    information on reproductive effects of nPB on humans and that the
    results of tests on animals were considered appropriate for
    evaluating potential reproductive health effects on humans.

> Further, EPA disagrees with the specific AEL value of 60 to 90 ppm
> that Rozman and Doull derived. They used data on headaches from a
> draft NIOSH survey, selecting an endpoint of 190 ppm. However, the
> data in the final survey were not sufficient to detect any
> dose-response with any statistical significance (Custom Products HHE,
> II-A-49). Further, more recent studies on human exposure to nPB have
> found neurotoxic effects occurring at levels at least as low as 86
> ppm, and possibly lower than 60 ppm (Ichihara 2004a, Beck and Caravati
> 2003). These data would indicate that an AEL of 60 to 90 ppm is not
> sufficiently protective against neurotoxic effects. Drs. Rozman and
> Doull themselves now suggest that an AEL of 25 ppm may be more
> appropriate for protecting against neurotoxic effects (Rozman and
> Doull, 2005).

-   Dr. Rodricks' AEL derivation and comments on ICF's derivation
    (II-D-65)---EPA reviewed Rodricks (2002) in developing its June 2003
    NPRM, although the study was not explicitly mentioned in that
    preamble. Rodricks (2002) suggests an AEL of 60 to 88 ppm for nPB,
    based on male reproductive effects. Dr. Rodricks says that the most
    sensitive endpoint that is relevant for occupational exposure is
    data from the parent generation of the two-generation reproductive
    study. Dr. Rodricks suggests that an uncertainty factor of only 1 to
    2 is necessary for animal to human extrapolation because one should
    consider animals and workers of average sensitivity; although such
    an argument presumably could be made for any chemical used in the
    workplace, EPA has not seen other AEL derivations that use this
    approach. Dr. Rodricks appears to agree with ICF that an uncertainty
    factor for variability in reproductive function in the human
    population is reasonable, although he suggests a factor of 2 instead
    of the range of 2 to 3 in ICF's derivation. Dr. Rodricks and
    colleagues previously recommended an AEL for nPB of less than 10
    ppm, and at that time suggested an uncertainty factor of 10 for
    variability in reproductive function in the human population
    (A-91-42, X-B-53). We discussed above the use of data from both the
    F0 and F1 generations and the use of an uncertainty factor of 3 for
    variability within the working population.

-   Dr. Stelljes's critique of ICF's AEL derivation (II-D-41a)---Dr.
    Stelljes states that ICF should have used data from the parent
    generation rather than from the offspring generation because "data
    from F1 animals is not directly applicable to a workplace exposure
    setting because both parents would not be exposed to nPB on a daily
    basis over the reproductive cycle, and also have their offspring
    exposed daily from weaning." EPA disagrees in part with Dr.
    Stelljes's reasoning. Data from F0 animals may not be sufficiently
    protective because effects on the F0 animals will not reflect
    effects of *in utero* exposure. However, we agree that exposure
    during weaning is not reflective of workplace exposure, and thus,
    data from F1 animals may be conservative. EPA proposed 25 ppm
    instead of 18 ppm in part to take this conservatism into account.

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-   Dr. Stelljes's (SLR International's) AEL derivation (II-D-13)---EPA
    discussed this AEL derivation at length in the preamble to the
    proposed rule at 68 FR 33298. We agreed with Dr. Stelljes's BMD
    modeling and his selection of reduced sperm motility in the F1
    offspring generation of the WIL Laboratories study as the most
    sensitive endpoint. However, we disagree with Dr. Stelljes's
    selection of uncertainty factors. There is no information showing
    that human sex cells are less sensitive to nPB than rat sex cells,
    and there is considerable evidence that human males have less
    reproductive capacity than male rats (citations from 2003 proposal).
    Therefore, it is appropriate to add an uncertainty factor of at
    least 3 to account for differences between rats and humans. Further,
    Stelljes dismisses the use of an uncertainty factor for differences
    within the human population. Although we agree that children and the
    elderly would not be present in the workplace as sensitive
    subpopulations, there certainly is variability in the reproductive
    abilities of different working-age people that would have no impact
    on the individual's ability to be hired or to work; therefore, EPA
    expects there is some variability in the susceptibility of working
    individuals to the effects of reproductive toxicants. EPA believes
    that male reproductive capacity is very susceptible to chemical
    insult (US EPA, 1996).

-   Dr. Murray's opinion on parent and offspring generations
    (II-D-58)---Dr. Murray says that because the offspring generation
    will not yet have developed sperm while *in utero*, it is more
    appropriate to use data from the parent generation of the
    two-generation study. However, Dr. Murray does not address the
    possibility that nPB exposure during pregnancy could influence the
    production of hormones that eventually would result in sperm
    production. Further, Dr. Murray's response does not address
    potential effects on ova, which would be present while a fetus is
    still in its mother's womb.

-   Report on uncertainty factors used by ACGIH from K.S. Crump Group
    (IV-D-26/OAR-2002-0064-0047 and -48)---This report concluded that
    EPA's approach to selecting uncertainty factors for use in risk
    assessment was more transparent, with justification for each value
    selected, and was more consistent than the values apparently used by
    the ACGIH in deriving TLVs. EPA agrees with these conclusions.

*Comment*: A commenter states that "an uncertainty factor of 10 is NOT
'generally' used to derive occupational exposure limits and that in
fact, uncertainty factors of 3 or less or more commonly used," citing
the K. S. Crump Group's report.

*Response*: In the case of the TLV that ACGIH established for nPB, ACGIH
appears to set an AEL that is a factor of 10 lower than the endpoint
cited as lowest (100 ppm for effects on pup weight) (ACGIH, 2005). Thus,
ACGIH has used an approach for nPB consistent with the total uncertainty
factor of 10 assigned by EPA.

> 5\. Overall stringency of the acceptable exposure limit

*Comment:* Some commenters supported the proposed AEL of 25 ppm, stating
that it was derived using appropriate conservative and cautious
scientific processes. Other commenters said that the proposed AEL of 25
ppm was too high, citing uncertainties in the data, the
inappropriateness of adjusting the AEL upward from 18 ppm, reports of
health effects on humans, and a need for higher uncertainty factors.
Other commenters said that the proposed AEL of 25 ppm was too low,
citing higher AELs derived by Drs. Stelljes, Doull, Rozman, and
Rodricks, NIOSH studies, and a need for lower uncertainty factors.
Commenters suggested alternate AEL values ranging from 1 ppm to 156 ppm.

*Response:* In this final rule, EPA is not recommending an acceptable
exposure limit. We have based our determination of acceptability by
comparing measured exposure levels from workers using nPB in solvent
cleaning to exposure levels discussed by EPA in the proposal (see
section IV.E). At the levels discussed in the NRPM or higher, we find
nPB acceptable for solvent cleaning. After considering the available
scientific studies on toxicity, exposure data, and alternative
derivations of the acceptable exposure limit, we find that the exposure
levels discussed in 2003 provide sufficient protection for human health
and are consistent with EPA's derivations of AELs for other chemicals
reviewed under the SNAP program and EPA guidance for risk assessment.

6\. Skin Absorption

In the June 2003 NPRM, EPA discussed listing nPB with a skin notation,
and proposed that this was not necessary (68 FR 33295).

*Comment:* Several commenters on the June 2003 proposal stated that a
skin notation for nPB is appropriate, while another commenter agreed
with EPA's proposal that no skin notation was necessary (Smith, 2003
(0024); HESIS, 2003 (0039); Werner, 2003 (0058), Weiss Cohen, 2003
(0038)). One commenter said that EPA should require manufacturers,
distributors, and marketers of nPB-containing products to communicate
such information on the Material Safety Data Sheets (MSDS) and the
product label.

*Response*: We agree with the commenter that said a skin notation is not
necessary. However, today's decision includes a recommendation for users
to wear protective clothing and flexible laminate gloves when using nPB
to address the concerns about dermal exposure.

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 including 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 (ACGIH, 2005), methylene chloride, and perchloroethylene, and there
is no evidence that absorption through the skin is greater for nPB than
for the other halogenated compounds. The TLV documentation for nPB
states, "There is no basis for a skin notation because the dermal LD50
of 1-BP was \>2 g/kg." Further, including a statement giving advice
about how to reduce skin exposure in the "Further Information" column of
listings is likely to be more informative to workers than a skin
notation.

Given the possibility that some nPB can be absorbed through the skin in
humans, and that the solvent can irritate the skin, EPA encourages users
to wear protective clothing and flexible laminate gloves when using nPB
and encourages manufacturers, distributors, and marketers of
nPB-containing products to include such precautions in their MSDSs. EPA
believes that our regulatory authority for the SNAP program is over the
substitution (use) of ozone-depleting substances, and thus, we do not
believe we have sufficient authority to regulate the manufacturers,
distributors and marketers of nPB.

7\. Iso-Propyl Bromide Limit

In the June 2003 proposed rule, we proposed as a use condition that nPB
formulations contain no more than 0.05% isopropyl bromide (iPB)[^11] by
weight because of potential health effects associated with this isomer
(68 FR 33301-33302).

*Comment*: Two commenters said that 0.05% iPB is an appropriate and
achievable limit. (Smith, 2003; Weiss Cohen, 2003). One of these
commenters stated that industry test studies showed that lower limits
were neither toxicologically justified nor economical. Another commenter
opposed the implementation of the proposed use restriction, stating that
it places an undue legal burden on end users, rather than the
manufacturers of raw materials, and would not benefit worker safety.
This commenter also stated that this is the only instance that SNAP has
regulated residual contaminants. This commenter also suggested that EPA
defer to an AEL of 1 ppm for iPB established by the government of Korea
and the Japan Society for Occupational Health. Moreover, this commenter
said that the difference between the acceptable iPB exposure determined
by EPA and that determined by ASTM-D6368-00 is very small and, thus,
EPA's proposed regulation does not add any value to existing standards.
Finally, this commenter noted that epidemiological data found no adverse
effect on human workers exposed to 110 ppm of iPB (Ichihara, specific
study not identified by the commenter). (Morford, 2003g and h)

*Response:* We agree that industry has achieved this contamination limit
for several years without regulation. We also agree that the
concentration of iPB likely to be breathed in by workers would be below
1 ppm even if workers were exposed to concentrations of nPB at 100 ppm
or more, provided that the iPB content meets the ASTM-D6368-00 standard
for nPB used in vapor degreasing. Further, even if iPB were present in
nPB formulations in concentrations as high as 1%, if industry meets the
AEL for nPB proposed in 2003 of 25 ppm, or lower, exposures still would
be at most 0.25 ppm. This is below the level of 1 ppm established by the
Korean government and by the Japan Society for Occupational Health
(Morford, 2003h). Therefore, we are not adopting a use condition for iPB
for the solvent cleaning end uses.

8\. Short-term Exposure Limit (STEL)

In the June 2003 NPRM, EPA recommended a short-term exposure limit of 75
ppm (three times the AEL).

*Comment:* One commenter noted that there was no indication in the
various applications as to how the exposures from those operations
compared to the EPA recommendation for a STEL at 75 ppm. This commenter
asserted that the potential for exceeding the STEL in solvent cleaning
applications appears high and should, therefore, be investigated by EPA.
This commenter also stated that, depending on the results of this
investigation, EPA may choose to find nPB unacceptable in metals
cleaning or restrict its use to where ventilation is employed and/or
personal protective equipment is worn.

*Response:* EPA disagrees that it is necessary to use a short-term
exposure limit in determining the acceptability of nPB in solvent
cleaning. 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). EPA provided the STEL recommendation in the June 2003
proposal to give guidance to the user community, consistent with the
following recommendation of the American Conference of Governmental
Industrial Hygienists (ACGIH): "Excursions in worker exposure levels may
exceed 3 times the \[threshold limit value\] TLV-TWA for no more than a
total of 30 minutes during a workday" (ACGIH 1999). We note that when
the ACGIH developed a TLV for nPB, they said there were no data to
support a short-term exposure limit (ACGIH, 2005).

C. Ozone depletion potential

We proposed that, since the ODP of nPB in the continental U.S. is only
0.013 to 0.018 relative to an ODP of 0.8 for CFC-113, 0.1 for methyl
chloroform, and 0.1 for HCFC-141b, nPB should not be found unacceptable
because of its ODP (68 FR 33303). The Agency recognized that nPB's ODP
could be much higher in tropical regions, as high as 0.071 to 0.100, but
since EPA is regulating nPB used in the U.S., we made our decision based
on the ODP in the continental U.S.

*Comment*: One commenter on the June 2003 NPRM provided information
(Wuebbles, 2002) and stated that "even if the entire amount of nPB
produced in 2002 was emitted across North American, European and Asian
latitudes, the resulting effects on ozone depletion would be too small
to measure." The same commenter said that the effects on ozone would
only be larger if all emissions were to occur in the equatorial region.
(Morford, 2003f)

*Response*: EPA agrees that, based on the current usage of nPB and its
ODP in the U.S., there is not a significant impact on the ozone layer.

*Comment:* 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).

*Response:* Because the ODP for nPB is higher when used in the tropics
(see footnote 3 above in section IV.2), we recognize the concerns raised
by these commenters. However, EPA is regulating use in the U.S. and
cannot dictate actions taken by other countries. For example, other
countries could choose to continue to use nPB even if EPA were to find
it unacceptable in the U.S. We believe the more appropriate forum to
address this concern is through the Parties to the Montreal Protocol.

At the most recent Meeting of the Parties to the Montreal Protocol, the
Parties made the following decision with regard to n-propyl bromide, in
order to "allow Parties to consider further steps regarding n-propyl
bromide, in the light of available alternatives" (Decision XVIII/11):

> 1\. To request the Scientific Assessment Panel to update existing
> information on the ozone depletion potential of n-propyl bromide,
> including ozone depleting potential depending on the location of the
> emissions and the season in the hemisphere at that location;
>
> 2\. To request the Technology and Economic Assessment Panel to
> continue its assessment of global emissions of n-propyl bromide,
> ...paying particular attention to:
>
> \(a\) Obtaining more complete data on production and uses of n-propyl
> bromide as well as emissions of n-propyl bromide from those sources;
>
> \(b\) Providing further information on the technological and
> economical availability of alternatives for the different use
> categories of n-propyl bromide and information on the toxicity of and
> regulations on the substitutes for n-propyl bromide;
>
> \(c\) Presenting information on the ozone depletion potential of the
> substances for which n-propyl bromide is used as a replacement;

3\. To request that the Technology and Economic Assessment Panel prepare
a report on the assessment referred to in paragraph 1 in time for the
twenty-seventh meeting of the Open-ended Working Group for the
consideration of the Nineteenth Meeting of the Parties. (MOP 18, 2006)

D. Other environmental impacts

With respect to environmental effects other than ozone depletion
potential, we stated in the June 2003 NPRM that users should observe
existing Federal, state, and local regulations such as those under the
Resource Conservation and Recovery Act or those for compliance with the
National Ambient Air Quality Standards (68 FR 33304).

*Comment*: Commenters stated that, until the safety of nPB has been
demonstrated conclusively, more stringent controls are necessary to
protect the public and the environment. In particular, these commenters
said that the potential for cross-media impacts was not given adequate
consideration in the proposed rule. They also stated that EPA did not
address the potential for nPB to bioaccumulate in the environment or its
impact on sensitive species. One commenter said that he thought it was
appropriate to ensure that nPB be kept out of wastewater, and an
independent contractor also mentioned concerns about water pollution.
Another commenter said that nPB hydrolyzes more quickly than the
chlorinated solvents, and so would have less impact on water quality.
Currently, the representative's company recommends that spent solvents
be incinerated, and offers free pickup and disposal of spent solvent to
its customers.

*Response*: EPA agrees that it should not be standard practice to
dispose of spent nPB in water, and that nPB should be kept out of
wastewater to the extent possible. This may be achieved by recycling or
through incineration. These also are good practices with other spent
halogenated solvents, whether or not they are specifically listed as
hazardous wastes.

EPA's PBT (*p*ersistence/*b*ioaccumulation/*t*oxicity) profiler tool
suggested that, based on its structure, nPB would not be considered
persistent in water or soil and that nPB would have a low tendency to
bioaccumulate (8.3, where 1000 is considered bioaccumulative and greater
than 5000 is considered very bioaccumulative). Further, the calculated
bioconcentration factor for nPB is only in the range of 18 to 23 (HSDB,
2004; ICF, 2004a). Under EPA's criteria for listing chemicals on the
Toxics Release Inventory, this would not be a level of concern (ICF
2004a, EPA 1992). Therefore, we conclude further testing for
bioaccumulation of this chemical is not needed before rendering a
decision for use of nPB in the solvent cleaning sector.

Currently, the estimated amount of nPB used in the U.S. in SNAP sectors
is on the order of 10 to 12 million pounds per year, which corresponds
to roughly 1% of the organic solvent cleaning market, a relatively small
amount. It is unlikely that very large amounts of nPB will enter and
remain in the nation's water supply, because:

-   nPB tends to evaporate quickly, with a calculated half-life of 3.4
    hours in a river or 4.4 days in a lake due to volatilization.

-   nPB hydrolyzes readily, with a measured hydrolysis half-life of 26
    days at 25° C and pH 7; and

-   If released to the atmosphere, nPB will exist solely in the vapor
    phase based on its vapor pressure of 110.8 mm Hg. Thus, it is
    unlikely to be redeposited in rainwater in significant amounts. (PBT
    Profiler, 2007; ICF, 2004a)

    Further, because nPB is short-lived compared to ODS and many ODS
    substitutes, it is unlikely that nPB will create a substantially
    greater impact than other acceptable cleaning solvents and than the
    ODS it replaces. EPA is required by the Clean Air Act to consider
    whether a replacement for an ODS is more harmful, overall, to human
    health and the environment than other available or potentially
    available substitutes. The available information shows that nPB will
    not be more hazardous than other available, acceptable solvents if
    it pollutes water or soil.

E. Flammability

In the June 2003 NPRM, we proposed that nPB should not be restricted or
found unacceptable because of flammability (68 FR 33303). EPA
specifically requested data concerning the flashpoint of pure nPB,
including the test method used to provide the data.

*Comment*: Several manufacturers of nPB and nPB-based solvents and an
independent contractor stated that nPB has no flash point under a number
of accepted consensus standards for flash point. In support of these
statements, the manufacturers of nPB and nPB-based solvents provided
flash point test data from a number of different test methods (ASTM D 92
open cup, ASTM D56 Tag closed cup, and ASTM D93 Pensky-Martens closed
cup).

*Response*: EPA agrees. The test results provided by the commenters
indicates that nPB has no flash point using a number of standard test
methods, including ASTM D 92 open cup, ASTM D56 Tag closed cup, and ASTM
D93 Pensky-Martens closed cup. Based on these data, we find that nPB is
not flammable under standard test conditions. EPA concludes that nPB
should not be considered unacceptable on the basis of flammability
risks.

F. Legal authority to set exposure limits

*Comment*: Two commenters stated that EPA has no jurisdiction to develop
any AEL designed to be applicable to a workplace environment, and that
this right belongs to OSHA.

*Response*: As an initial matter, EPA notes that it has not established
an AEL applicable to the workplace in this rule. Rather, EPA reviewed
the available information to determine what a safe workplace exposure
might be in order to determine whether use of nPB in the solvent
cleaning sector poses substantially more risk than use of other
available substitutes. The analysis performed by EPA imposes no binding
obligation on anyone, particularly in this case where EPA determined
that nPB is acceptable for use in the solvent cleaning sector.

Although the Occupational Safety and Health Act (OSH Act) gives the
Occupational Safety and Health Administration (OSHA) authority to issue
a rule setting or revising an occupational safety or health standard
(section 6), it does not prohibit other Federal agencies from reviewing
the safe level of exposure under other statutes that require
consideration of the human health and environmental effects of a
substance.

Section 612 of the Clean Air Act expressly recognizes that some
substitutes for ODS may pose more risk to human health and the
environment than others and expressly requires EPA to prohibit use of
substitutes. that pose more risk than other substitutes that are
currently or potentially available. Thus, in evaluating whether a
substitute should be found acceptable, we must compare the risks to
human health and the environment of that substitute to the risks
associated with other substitutes that are currently or potentially
available.

Our long-standing interpretation is that worker safety is a factor we
consider in determining whether a substitute poses significantly greater
risk than other available substitutes. In the original SNAP rule, we
promulgated the criteria we would review for purposes of determining
whether a substitute posed more risk than other available substitutes.
Specifically, 40 CFR 82.178(a) specifies the information we require as
part of a SNAP application and 40 CFR 82.180(a)(7) identifies the
criteria for review. Notably, we require submitters to provide
information regarding the exposure data (40 CFR 82.178(a)(10)) and we
identify "occupational risks" as one of the criteria for review (40 CFR
82.180(a)(7)(iv)). In the preamble of the original SNAP rule, we said
that we would use any available OSHA PELs, EPA inhalation reference
concentrations, or EPA cancer slope factor data for a substitute
together with exposure data to explore possible concerns with toxicity
(March 18, 1994; 59 FR 13066). We have reviewed substitutes based on
existing OSHA PELs, where available, and, where not available, based on
our own assessment of what level is safe for workers. (See e.g., March
18, 1994, 59 FR 13044; Sept. 5, 1996, 61 FR 47012; June 8, 1999, 64 FR
30410; June 19, 2000, 65 FR 37900; December 18, 2000, 65 FR 78977; March
22, 2002,67 FR 13272; August 21, 2003, 68 FR 50533). In making our own
assessment, we review any existing recommended exposure guidelines and
available scientific studies and use EPA's risk assessment guidelines
(e.g., US EPA, 1994b).

In the case of EPA's evaluation of nPB, there is no final OSHA PEL for
EPA to use in evaluating workplace exposure risks. There is a wide
variability in the workplace exposure guidelines recommended by
manufacturers of nPB-based products, ranging from 5 ppm to 100 ppm, thus
providing no definitive value for evaluating the human health risks of
workplace exposure. The ACGIH has recently established a TLV for nPB of
10 ppm; however, as discussed above in section IV.E, EPA has concerns
about the scientific basis for this TLV. As provided in the original
SNAP rule, in the absence of a definitive workplace exposure limit set
by OSHA, we evaluated the available information to establish our own
health-based criteria for evaluating nPB's human health risks to
workers.

*Comment:* A commenter said that EPA's authority for the SNAP program is
under section 615 of the Clean Air Act and that the SNAP program only
has authority to take action based on effects on the stratosphere.
Specifically, the commenter claims section 615 of the CAA limits EPA's
authority under title VI to regulating for purposes of protecting the
stratospheric ozone layer. Citing section 618, the commenter also
contends that section 618 identified SNAP requirements as "requirements
for the control and abatement of air pollution and cites the CAA and EPA
policy documents as identifying ambient air as air external to
buildings. The commenter also notes that title VI was intended to
implement the Montreal Protocol and that it replaced former Part B. The
commenter cites legislative history from the enactment of Part B that
indicated EPA's authority under Part B was not intended to pre-empt
authority of other agencies to take action with respect to hazards in
their areas of jurisdiction and that EPA's authority under Part B was
only to fill regulatory gaps and not to supersede existing authority of
other agencies. With respect to the legislative history of the 1990
Amendments, the commenter argues that there is no suggestion that "EPA
has authority to set workplace worker-exposure standards." The commenter
also cites legislative history from the Toxic Substances Control Act in
which Congress indicated EPA's authority under that statute does not
extend to setting workplace standards.

*Response*: While many provisions in title VI address the regulation of
substances that deplete the stratospheric ozone layer, section 612 which
governs the SNAP program is broader. The purpose of Section 612 is to
review substitutes for ODS and Section 612 of the Clean Air Act clearly
requires EPA to consider both the environmental effects as well as
*human* *health*, which includes both the health of the general
population and workers. EPA believes there is no doubt that the
statutory language requires EPA to consider effects beyond those on the
stratospheric ozone layer. In addition, the legislative history makes
clear that this language is to be interpreted broadly. Specifically, the
report of House Debate on the Clean Air Act Amendments provides "the
Administrator shall base risk estimates on the total environmental risk
(toxicity, flammability, atmospheric, etc.) that is perceived to exist,
not just the risk as it relates to ozone depletion." House Debate on the
Clean Air Act Amendments of 1990 Conference Report, S-Prt 103-38 at
1337. The legislative history cited by the commenter is not pertinent.
The legislative history for Part B of Title I of the Act is not relevant
because that section was repealed in 1990. Pub. Law 101-549, section
601. Nor is the legislative history for other statutes, such as TSCA,
relevant for determining what authority Congress granted to EPA under
the CAA.

The commenter incorrectly states that sections 615 and 618 of the CAA
place limits on EPA's authority under section 612 of the Act. These
provisions expand, rather than restrict, the Administrator's authority.
Section 615 is a separate provision of the statute and provides general
authority for the Administrator to regulate for purposes of addressing
adverse effects to the stratosphere. This provision does not explicitly
or implicitly purport to limit the Administrator's authority under other
provisions of the Act. Rather, it is a general provision authorizing the
Administrator to regulate for protecting against adverse effects to the
stratospheric ozone layer.

With respect to section 618, we first note that the commenter appears to
equate the stratospheric ozone layer with "ambient air." In fact, they
are two different things. Ambient air is defined as "that portion of the
atmosphere, external to buildings, to which the general public has
access." 40 CFR 50.1(e). The stratospheric level generally extends from
10 to 50 kilometers above the earth and is not considered air to which
the public has access. \[See <http://www.epa.gov/ozone/defns.html>\].
The definition of "air pollutant" under the CAA is defined in terms of
substances emitted to the "ambient air." The purpose of section 618 is
to make clear that for purposes of sections 116 (retention of state
authority) and 118 (control of pollution from federal facilities), the
provisions in Title VI governing protection of the stratospheric ozone
layer shall be treated the same as if they were for the purpose of
controlling and abating "air pollution" (i.e., pollution to the ambient
air). Again, this is not for the purpose of restricting the
Administrator's authority under any provision of the Act. Rather, it is
for the purpose of extending the protections of Title VI to programs
that otherwise only address air pollution (i.e., ambient air, which does
not include the stratospheric ozone layer).

*Comment*: A commenter stated that EPA's claim to authority conflicts
with the Department of Labor's administrative "whistleblower" case law.
These cases hold that a whistleblower action may proceed under the CAA
only when the complaint concerned substances emitted to the ambient air.
Claims regarding air quality within the workplace are brought under the
whistleblower provisions of the OSH Act.

*Response:* As an initial matter, the CAA and its legislative history
speak for itself and EPA, not the Department of Labor, is the Agency
responsible for interpreting the provisions of the Act. Thus, any broad
interpretation by the Department of Labor's Administrative Review Board
of the scope of EPA's authority under CAA taken should not be accorded
the same level of deference as an interpretation by EPA. In any event,
the commenter overstates the import of the decisions issued by the
Administrative Review Board. In each of the cited decisions, the Board
examined the specific circumstances before it to determine which
statutory whistleblower provision provided the basis for the claimed
action. While making general pronouncements that the CAA regulates
ambient air and OSHA regulates air within the workplace, none of these
opinions specifically addressed the scope of EPA's authority under
section 612, the SNAP provisions of the Act.

*Comment*: A commenter stated that even if ventilation or other measures
could reduce exposures to below 25 ppm, there is nothing to ensure that
companies will take such measures. This commenter also stated that he is
aware of nPB formulators that have already announced they will not
adhere to this voluntary standard. Three commenters, all representing
local environmental regulators, stated that a recommendation that worker
exposure be limited to 25 ppm will not carry the enforcement powers of
an OSHA standard, and that this lack of control will encourage the use
of nPB in applications beyond those envisioned by EPA. Another commenter
asserted that the proposed exposure limits (both the AEL and the STEL)
should be established as use conditions, citing Section 612 as the basis
for EPA's authority to do so. This commenter stated that a precedent has
already been set for EPA to accept an alternative chemical subject to
use conditions---including that observance of workplace concentration
limits---in the adhesives, aerosols, and solvent cleaning sectors (e.g.,
HCFC-225 ca/cb, HFC-4310mee, monochlorotoluenes, benzotrifluorides).

*Response*: EPA agrees that a recommended AEL from EPA does not provide
the same level of protection as an enforceable standard from OSHA. We
also agree that EPA has the authority under §612 to require use
conditions in those circumstances where use of a potentially promising
substitute would otherwise be unacceptable unless those use conditions
are met and there are significant concerns about the ability of industry
to meet a safe level for use. In the preamble to the original SNAP rule,
we recognized that there may be cases where OSHA has not regulated
worker exposure to a substitute. We went on to say that "EPA anticipates
applying use conditions only in the rare instances where clear
regulatory gaps exist, and where an unreasonable risk would exist in the
absence of any conditions." For the solvent cleaning end use, we do not
believe that there is an unreasonable risk in the absence of a use
condition. Available exposure data show that roughly 88% of samples from
nPB users in solvent cleaning met an exposure level of 25 ppm, 81% met
an exposure level of 18 ppm, and 70% met an exposure level of 10 ppm (US
EPA, 2003). One nPB supplier provided evidence that on the few occasions
when nPB concentrations from vapor degreasers were higher than the
company's recommended AEL 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). 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 use nPB at levels considered safe for workers. As noted
above, this is the approach we indicated we would follow at the time of
the original SNAP rule and we have taken this same approach for many
other solvents where users are readily able to meet a workplace exposure
limit that will protect human health and there is no enforceable OSHA
PEL (e.g., HFC-365mfc and heptafluorocyclopentane at 65 FR 78977,
ketones, alcohols, esters, and hydrocarbons at 59 FR 13044).

*Comment*: One commenter claims that section 6 of the Occupational
Safety and Health Act requires OSHA to make certain legal findings
before promulgating a standard and that therefore EPA has no authority
to develop any AEL applicable to a workplace environment. Furthermore,
since OSHA is the only agency that can make standards applicable in the
workplace, any level developed by EPA is misleading. The same commenter
said that EPA offers no reasoning as to why a different methodology for
setting an AEL (from that of OSHA) is necessary or advisable. Therefore,
this commenter believes that the Agency's process violates equal
protection unless EPA is publishing a new standard for chemical review
under SNAP.

*Response*: In this rulemaking, EPA has not developed an AEL that is
applicable in any workplace. Rather, EPA looked at a range of possible
AELs for purposes of determining whether nPB will pose significantly
greater risk than other substitutes that are available in the same end
use. The range of levels EPA used for its analysis is not binding.
Moreover, as explained above in section V.B.2, EPA has concluded that
for purposes of finding nPB acceptable in the solvent cleaning end use,
it is not necessary to provide a non-binding recommended workplace
exposure limit because these users in the solvent cleaning sector are
regularly able to comply with even the lowest level EPA considered in
performing its evaluation.

For standards covering hazardous chemicals in the workplace, the OSH Act
requires OSHA to set standards that, to the extent feasible, ensure that
workers do not suffer material impairments of health. Standards
established by OSHA under their statute have not typically prohibited
the use of the chemical in any particular application, but instead
establish performance goals for the use and handling of hazardous
chemicals that reduce such risks to the extent feasible. The available
information on health effects of nPB on workers is not sufficiently
well-characterized to develop a standard based on avoiding material
impairments of health in workers. Most manufacturers and organizations
that set workplace exposure limits such as ACGIH and the American
Industrial Hygiene Association use an approach similar to EPA\'s and do
not base exposure limits on avoiding material impairments of health in
workers. Because of the need for large amounts of well-characterized
data from the workplace on exposures and associated health effects to
prepare an AEL to prevent material impairment, if EPA were to develop
AELs for nPB and other chemicals based on the approach required by
section 6 of the OSH Act, EPA would effectively be unable to assess the
human health effects of ODS alternatives in time to assist industry in
transitioning away from ODS. In order to provide for a more timely
assessment of human health effects, as well as one that is consistent
with federal guidelines of the National Academies of Science (NAS,
1983), we have considered exposure levels following EPA guidance (US
EPA, 1994b). Different substances have different toxicological effects
and those effects must be considered based on the best scientific
information and methodologies available. It is incorrect to claim that
such reviews, which focus on the effects of different substances,
resulted in disparate treatment of nPB.

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

Below are actions that will help nPB users minimize exposure levels:

*All end uses*

-   All users of nPB should wear appropriate personal protective
    equipment, including chemical goggles, flexible laminate protective
    gloves (e.g., Viton, Silvershield) and chemical-resistant clothing.
    Special care should be taken to avoid contact with the skin since
    nPB, like many halogenated solvents, can be absorbed through the
    skin. Refer to OSHA's standard for the selection and use of Personal
    Protective Equipment, 29 CFR 1910.132.

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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. Where respiratory protection is necessary to limit worker
    exposures, respirators must be selected and used in accordance with
    OSHA's Respiratory Protection standard, 29 CFR 1910.134.

-   Use less solvent, or use a different solvent, either alone or in a
    mixture with nPB.

-   Follow all recommended safety precautions specified in the
    manufacturer's MSDS.

-   Workers should receive safety training and education that includes
    potential health effects of exposure to nPB, covering information
    included on the appropriate MSDSs, as required by OSHA\'s Hazard
    Communication Standard (29 CFR 1910.1200).

-   Request a confidential consultation from your State government on
    all aspects of occupational safety and health. You can contact the
    appropriate state agency that participates in OSHA's consultation
    program. These contacts are on OSHA's web site at
    <http://www.osha.gov/oshdir/consult.html.> For further information
    on OSHA's confidential consultancy program, visit OSHA's web page at
    <http://www.osha.gov/html/consultation.html>.

-   Use the employee exposure monitoring programs and product
    stewardship programs where offered by manufacturers and formulators
    of nPB-based products.

-   If the manufacturer or formulator of your nPB-based product does not
    have an exposure monitoring program, we recommend that you start
    your own exposure monitoring program, and/or request a confidential
    consultation from your State government.

A medical monitoring program should be established for the early
detection and prevention of acute and chronic effects of exposure to
nPB. The workers\' physician(s) should be given information about the
adverse health effects of exposure to nPB and the workers\' potential
for exposure.

-   For non-aerosol solvent cleaning, follow guidelines in the National
    Emissions Standards for Hazardous Air Pollutant (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.>

We note that these steps are useful for reducing exposure to any
industrial solvent, and not just nPB.

**VII. 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.

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.

EPA also considered potential costs end users could incur to meet
acceptable exposure levels if they 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 81% of nPB users in the non-aerosol solvent
cleaning sector already achieve exposure levels at the low end of the
range of acceptable exposures or lower (US EPA, 2003). Of those nPB
solvent users with exposure levels above that, we examined the cost
associated with reducing emissions on average by 60%.

If all nPB users in solvent cleaning reduced exposures to the low end of
the range of acceptable exposures, EPA estimates that users would save
up to \$2 million dollars per year, overall (US EPA, 2007). The value
will depend on the number of users that attempt to meet an acceptable
exposure level which is already being achieved with existing equipment,
the initial exposure level of cleaning solvent users, the price of nPB,
and the amount of emission control equipment installed.

## *B. Paperwork Reduction Act* 

There are no new requirements for reporting or recordkeeping or
information collection associated with this final rule. The final rule
merely allows the use of substitutes for ozone-depleting substances,
without requiring the collection, keeping, or reporting of information.
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. A copy of the OMB approved Information Collection
Request (ICR) may be obtained from Susan Auby, Collection Strategies
Division; U.S. Environmental Protection Agency (2822T); 1200
Pennsylvania Ave., NW, Washington, DC 20460 or by calling (202)
566-1672.

Burden means the total time, effort, or financial resources expended by
persons to generate, maintain, retain, or disclose or provide
information to or for a Federal agency. This includes the time needed to
review instructions; develop, acquire, install, and utilize technology
and systems for the purposes of collecting, validating, and verifying
information, processing and maintaining information, and disclosing and
providing information; adjust the existing ways to comply with any
previously applicable instructions and requirements; train personnel to
be able to respond to a collection of information; search data sources;
complete and review the collection

of information; and transmit or otherwise disclose the information.

An agency may not conduct or sponsor, and a person is not required to
respond to a collection of information unless it displays a currently
valid OMB control number. The OMB

control numbers for EPA\'s regulations in 40 CFR are listed in 40 CFR
part 9.

C. *Regulatory Flexibility Act*

The Regulatory Flexibility Act (RFA) generally requires an agency to
prepare a regulatory flexibility analysis of any rule subject to notice
and comment rulemaking requirements under the Administrative Procedure
Act or any other statute unless the agency certifies that the rule will
not have a significant economic impact on a substantial number of small
entities. Small entities include small businesses, small organizations,
and small governmental jurisdictions. 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 to inclusion in our analysis but slightly increased
the percentages of small business significantly impacted in the
analysis. We solicited comments on the choice of this alternate
definition for this analysis on the June 2003 NPRM, and received no
public comments.

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 finalizing 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 approximately 1470 users of nPB industrial cleaning solvents (e.g.,
cleaning with vapor degreasers) would be subject to this rule. This rule
will impose no requirements and thus, this rule would not have a
significant economic impact on a substantial number of small entities.

Types of businesses that would be subject to this final 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 (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 (NAICS subsector 336).

    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.

    In order to consider the resources that affected small businesses
    have available to operate and to respond to the recommendations in
    the final rule, EPA compared the cost of meeting the acceptable
    exposure limit to small businesses' annual sales. In our analysis
    for this 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 rule on small businesses.

    **Table 5: 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                                                                                                     
  ------------ ------------ ------------ ------------- ------------ ------------ ----------------- ------------ -------------

Considering the costs to solvent users to implement the recommended 18
ppm exposure limit, we found that no small businesses would experience
impacts of either 1% or 3% or greater of annual sales based on
annualized costs of purchasing or upgrading vapor degreasers. When
considering costs in the year that a company purchases or upgrades its
vapor degreaser, at most 50 small businesses would experience impacts of
1% or greater and at most 40 small businesses would experience impacts
of 3% or greater. This constitutes at most 3% of all small solvent users
of nPB. Based on the relatively small number and percentage of small
businesses that would experience significant impacts, EPA concludes that
recommendations in this rule would not have a significant economic
impact on a substantial number of small entities.

Although this final rule will not have a significant economic impact on
a substantial number of small entities, EPA nonetheless has tried to
reduce the impact of this rule on small entities. Before selecting the
regulatory option in this final rule, we considered a number of
regulatory options, such as:

-   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.

-   Retaining the previously proposed requirement for a limit on iPB
    content in nPB formulations.

The costs of a number of these options are included in EPA's analysis
(US EPA, 2006).

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 developed a fact sheet and updated our program web site to inform
small businesses about the proposed rule and to request their comments.

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 final rule does not affect State,
local, or tribal governments. This rule contains no enforceable
requirements. The impact of users meeting the AEL range discussed in the
preamble is from a savings of \$2 million per year to a cost of \$0
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 final 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 final 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 final 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 final 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 final 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 final 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.

    This final 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.

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*

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.

J. *Congressional Review Act*

The Congressional Review Act, 5 U.S.C. 801 et seq., as added by the
Small Business Regulatory Enforcement Fairness Act of 1996, generally
provides that before a rule may take effect, the agency promulgating the
rule must submit a rule report, which includes a copy of the rule, to
each House of the Congress and to the Comptroller General of the United
States. EPA will submit a report containing this rule and other required
information to the U.S. Senate, the U.S. House of Representatives, and
the Comptroller General of the United States prior to publication of the
rule in the Federal Register. A major rule cannot take effect until 60
days after it is published in the Federal Register. This action is not a
"major rule" as defined by 5 U.S.C. 804(2). This rule will be effective
**\[insert date 60 days after publication\]**.

**VIII. 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 final rule?***

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***

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

***Ozone-Depletion Potential and Other Environmental Impacts***

ATSDR, 1994. Toxicological Profile For Acetone. Agency for Toxic
Substances and Disease Registry. May, 1994. Available at
<http://www.atsdr.cdc.gov/toxprofiles/tp21-c5.pdf>
(EPA-HQ-OAR-2002-0064-0118)

ATSDR, 1996. Toxicological Profile For 1,2-Dichloroethene. Agency for
Toxic Substances and Disease Registry. August, 1996. Available at
<http://www.atsdr.cdc.gov/toxprofiles/tp87-c5.pdf>
(EPA-HQ-OAR-2002-0064-0113)

ATSDR, 1997. Toxicological Profile For Trichloroethylene. Agency for
Toxic Substances and Disease Registry. September, 1997. Available at
<http://www.atsdr.cdc.gov/toxprofiles/tp19-c5.pdf>
(EPA-HQ-OAR-2002-0064-0123)

ATSDR, 2004. Draft Toxicological Profile For 1,1,1-Trichloroethane.
Agency for Toxic Substances and Disease Registry. September, 2004.
Updated draft for comment. Available at
<http://www.atsdr.cdc.gov/toxprofiles/tp70-c6.pdf>
(EPA-HQ-OAR-2002-0064-0132)

EDSTAC, 1998. Final Report of the Endocrine Disruptor Screening and
Testing Advisory Committee. August, 1998. (EPA-HQ-OAR-2002-0064-0136)

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. (EPA-HQ-OAR-2002-0064-0112)

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.
(EPA-HQ-OAR-2002-0064-0086)

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.
(EPA-HQ-OAR-2002-0064-0133)

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. (EPA-HQ-OAR-2002-0064-0091)

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. (EPA-HQ-OAR-2002-0064-0102)

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. (EPA-HQ-OAR-2002-0064-0131)

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. (EPA-HQ-OAR-2002-0064-0103)

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. (EPA-HQ-OAR-2002-0064-0107)

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, 2004a.

US EPA, 1994a. Chemical Summary for Methyl Chloroform, prepared by
Office of Pollution Prevention and Toxics, August, 1994.
(EPA-HQ-OAR-2002-0064-0121)

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.
(EPA-HQ-OAR-2002-0064-0114)

***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, b. 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, 2003c. 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***

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](http://www.acgih.org/).

Albemarle, 2003. Material Safety Data Sheet for Abzol® Cleaners. 2003.

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. (EPA-HQ-OAR-2002-0064-0111)

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.
(EPA-HQ-OAR-2002-0064-0096)

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.
(EPA-HQ-OAR-2002-0064-0120)

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.
(EPA-HQ-OAR-2002-0064-0115)

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. (EPA-HQ-OAR-2002-0064-0142)

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.
(EPA-HQ-OAR-2002-0064-0138)

ICF, 2002. 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, 2004b. ICF Consulting. Number range CHAPTERICF Consulting Review of
the TERA Report. December 13, 2004.

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

ICF, 2004d. ICF Consulting. Review of ACGIH's Proposed Threshold Limit
Value for 1-Bromopropane. April 26, 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.

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., 2000a. 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., Yu X., Kitoh J., et al. 2000b. Reproductive toxicity of
1_bromopropane, a newly introduced alternative to ozone layer depleting
solvents, in male rats. *Toxicol Sciences* 54:416_423. (A-2001-07,
II-A-7)

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) (EPA-HQ-OAR-2002-0064-0093)

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. (EPA-HQ-OAR-2002-0064-0139)

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 (EPA-HQ-OAR-2002-0064-0125)

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. (EPA-HQ-OAR-2002-0064-0116)

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

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. (EPA-HQ-OAR-2002-0064-0105)

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](http://newton.nap.edu/catalog/366.html).
(EPA-HQ-OAR-2002-0064-0094)

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

O'Malley, 2004. Letter from Nancy O'Malley, Toxicology Advisor,
Albemarle Corporation to The Science Group of the American Conference of
Governmental Industrial Hygienists. Comments on the draft Documentation
for proposed TLV for 1-bropmopropane (1-BP). July 30, 2004.

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.
(EPA-HQ-OAR-2002-0064-0126)

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. (EPA-HQ-OAR-2002-0064-0077, -0080, -0081, -0082,
-0101, -0104, -0137, -0137.1)

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. (EPA-HQ-OAR-2002-0064-0127)

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
(EPA-HQ-OAR-2002-0064-0087)

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.
(EPA-HQ-OAR-2002-0064-0144)

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 occupationally exposed to 1-bromopropane. *Mutation Research*
603 (2006) 1--14 (EPA-HQ-OAR-2002-0064-0130)

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

US EPA, 1994b. 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)
Available online at
<http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=71993>

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. (EPA-HQ-OAR-2002-0064-0109)

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
(EPA-HQ-OAR-2002-0064-0088)

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. (A-2001-07, II-D-10)

Yamada T. et al., 2003. Exposure to 1-Bromopropane Causes Ovarian
Dysfunction in Rats. *Toxicol Sci* 71:96-103 (EPA-HQ-OAR-2002-0064-0097)

***How is EPA Responding to Comments?***

ACGIH, 1991. Full citation above in "Human Health" section.

ACGIH, 2004. TLVs and BEIs: Threshold Limit Values for Chemical
Substances and Physical Agents, Biological Exposure Indices. American
Conference of Governmental Industrial Hygienists. Cincinnati, OH.
Available online at [www.acgih.org](http://www.acgih.org/) .

ACGIH, 2005. Full citation above in "Human Health" section.

Beck and Caravati, 2003. Full citation above in "Human Health" section.

Chemtura, 2006. Material Safety Data Sheet for n-propyl bromide. April,
2006.

ClinTrials, 1997a. Full citation above in "Human Health" section.

ClinTrials, 1997b. Full citation above in "Human Health" section.

Doull and Rozman, 2001. 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)

Dunson et al., 2002. Full citation above in "Human Health" section.

Elf Atochem, 1995. 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)

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.

Farr, 2003. Comment on proposed rule on n-propyl bromide from Craig
Farr, Atofina. July 31, 2003. (EPA-HQ-OAR-2002-0064-0060)

HDSB, 2004. Full citation above in "Ozone-Depletion Potential and Other
Environmental Impacts" section.

HESIS, 2003. California Department of Health Services ‑ HESIS
1‑Bromopropane (n‑Propyl Bromide) Health Hazard Alert.
(EPA-HQ-OAR-2002-0064-0039)

Honma, 2003. Full citation above in "Human Health" section.

ICF, 2002a. Full citation above in "Human Health" section.

ICF, 2004a. Full citation above in "Ozone-Depletion Potential and Other
Environmental Impacts" section.

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

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, 1999. Full citation above in "Human Health" section.

Ichihara, 2000a. Full citation above in "Human Health" section.

Ichihara, 2002. Full citation above in "Human Health" section.

Ichihara, 2004a. Full citation above in "Human Health" section.

Ichihara, 2004b. Full citation above in "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)

Linnell, 2003. Full citation above in "Ozone-Depletion Potential and
Other Environmental Impacts" section.

Majersik, 2004. Full citation above in "Human Health" section.

Majersik, 2005. Full citation above in "Human Health" section.

MOP 18, 2006. Report of the Eighteenth Meeting of the Parties to the
Montreal Protocol on Substances that Deplete the Ozone Layer. November
16, 2006.

Morford, 2003a. Full citation above in "Flammability" section.

Morford, 2003b. Full citation above in "Flammability" section.

Morford, 2003c. Full citation above in "Flammability" section.

Morford, 2003d. Support for EPA Proposal to Approve n propyl bromide and
Comments Pursuant to Section D. Flammability of Protection of
Stratospheric Ozone: Listing of Substitutes for Ozone Depleting
Substances - n-Propyl Bromide: Proposed Rule Federal Register Vol. 68
No. 106, June 3, 2003. Enviro Tech International, Inc. Comments
Regarding Proposed Rule & Exhibit A Richard Morford, Enviro Tech
International. August 3, 2003. (EPA-HQ-OAR-2002-0064-0047)

Morford, 2003e. Enviro Tech International, Inc. Combined Exhibits to
Comment 0047/Morford, 2003e on Proposed Rule Richard Morford, Enviro
Tech International. August 3, 2003. (EPA-HQ-OAR-2002-0064-0048)

Morford, 2003f. Initial Comments to Protection of Stratospheric Ozone:
Listing of Substitutes for Ozone Depleting Substances - n-Propyl
bromide: Proposed Rule Federal Register

Vol. 68 No. 106, June 3, 2003. Richard Morford, Enviro Tech
International. June 26, 2003. (EPA-HQ-OAR-2002-0064-0002)

Morford, 2003g. Comment regarding proposed restriction on isopropyl
bromide Richard Morford, Enviro Tech International. August 3, 2003.
(EPA-HQ-OAR-2002-0064-0042)

Morford, 2003h. Enviro Tech International Inc Comment Regarding iPB
Content Restriction Exhibit A 04‑Aug‑2003 (EPA-HQ-OAR-2002-0064-0046)

Morford, 2003i. White Paper: "EPA Is Unlawfully Regulating Occupational
Exposures" Attachment to public comments. (EPA-HQ-OAR-2003-0064-0049)

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

PBT Profiler, 2007. Results from the PBT Profiler Tool for
1-bromopropane, CAS No. 106-94-5**.** Downloaded on February 9, 2007
from <http://www.pbtprofiler.net/default.asp>. Imagine of file available
in docket EPA-HQ-OAR-2002-0064.

Risotto, 2003. Full citation above in "Human Health" section.

Rodricks, 2002. Full citation above in "Human Health" section.

Rozman and Doull, 2005. Rozman and Doull, 2005. Presentation by Drs.
Rozman and Doull at the North American Congress of Clinical
Toxicologists. September 14, 2005. (EPA-HQ-OAR-2002-0064-0126)

RTI, 2005. Full citation above in "Human Health" section.

Ruckriegel, 2003. Comment on n-Propyl Bromide Recommended Workplace
Exposure Level in Proposed Rule Published in Federal Register Vol. 68,
No. 106, June 3, 2003. August 2, 2003 (EPA-HQ-OAR-2002-0064-0055)

Rusch and Bernhard, 2003. Comments on proposed regulation of n-propyl
bromide from Steven Bernhardt and George Rusch, Honeywell. August 1,
2003. (EPA-HQ-OAR-2002-0064-0059)

Rusch, 2003. Late comments on proposed regulation of n-propyl bromide
from George Rusch, Honeywell. (EPA-HQ-OAR-2002-0064-0059)

Sekiguchi, 2002. Full citation above in "Human Health" section.

SLR International, 2001. Full citation above in "Human Health" section.

Smith, 2003. Comments on Protection of Stratospheric Ozone: Listing of
Substitutes for Ozone-Depleting Substances - n-Propyl Bromide, FR Vol.
68, No. 106, June 3,2003. R. L. Smith, Albemarle Corporation. July 23,
2003.

Stelljes, 2003. Comments from Dr. Marc Stelljes, SLR International, on
proposed rule on n-propyl bromide. (HQ-EPA-OAR‑2002‑0064‑0022)

Stelljes and Wood, 2004. Full citation above in "Human Health" section.

Stelljes, 2005. Full citation above in "Human Health" section.

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

US EPA, 1994b. Full citation above in "Human Health" section.

US EPA, 1996. Full citation above in "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)

Weiss Cohen, 2003. Comments from Tammi Weiss Cohen, Dead Sea Bromine
Group. Comments 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-2002-0064-0038)

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

WIL, 2001. Full citation above in "Human Health" section.

Yamada et al., 2003. Full citation above in "Human Health" section.

***Executive Orders and Statutes***

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

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

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

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

US EPA, 2006. Analysis of Economic Impacts of nPB Rulemaking. 2006.

US EPA, 2007. Analysis of Economic Impacts of Final nPB Rulemaking for
Cleaning Solvent Sector. 2007.

**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 107 of [108](#End_of_document) pages

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

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

Stephen L. Johnson, Administrator

APPENDIX A: SUMMARY OF DECISION

**SOLVENT CLEANING**

ACCEPTABLE SUBSTITUTE

+------------+--------------+----------+------------------------------+
| End Uses   | Substitute   | Decision | Further Information          |
+============+==============+==========+==============================+
| Metals     | n-propyl     | Ac       | EPA recommends the use of    |
| cleaning,  | bromide      | ceptable | personal protective          |
| e          | (nPB) as a   |          | equipment, including         |
| lectronics | substitute   |          | chemical goggles, flexible   |
| cleaning,  | for CFC-113  |          | laminate protective gloves   |
| and        | and methyl   |          | and chemical-resistant       |
| precision  | chloroform   |          | clothing.                    |
| cleaning   |              |          |                              |
|            |              |          | EPA expects that all users   |
|            |              |          | of nPB would comply with any |
|            |              |          | final Permissible Exposure   |
|            |              |          | Limit that the Occupational  |
|            |              |          | Safety and Health            |
|            |              |          | Administration issues in the |
|            |              |          | future under 42 U.S.C.       |
|            |              |          | 7610(a).                     |
|            |              |          |                              |
|            |              |          | nPB, also known as           |
|            |              |          | 1-bromopropane, is Number    |
|            |              |          | 106-94-5 in the Chemical     |
|            |              |          | Abstracts Service (CAS)      |
|            |              |          | Registry.                    |
+------------+--------------+----------+------------------------------+

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

[^1]: ^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.

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

[^3]: Also called PERC, tetrachloroethylene, or tetrachloroethene,
    C~2~Cl~4~, CAS Reg. No. 127-18-4.

[^4]: nPB emissions in the tropics have an ODP of 0.071 to 0.100; the
    portions of the U.S. outside the continental U.S., such as Alaska,
    Hawaii, Guam, and the U.S. Virgin Islands, contain less than 1
    percent of the U.S.'s businesses in industries that could use nPB.
    Thus, their potential impact on the ozone layer must be
    significantly less than that of the already low impact from nPB
    emissions in the continental U.S. (U.S. Economic Census, 2002a
    through f)

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

[^6]: By EPA guidelines, we would apply an uncertainty factor of √10, or
    approximately 3, for differences between species for all health
    effects. We would also apply an uncertainty factor of √10 (3) for
    variability within the working population for reproductive and
    developmental effects, because, among other reasons, these
    conditions would not necessarily screen out an individual from being
    able to work, unlike for liver or nervous system effects. Therefore,
    for reproductive and developmental effects, we use a composite
    uncertainty factor of 10. See further discussion of uncertainty
    factors in section V.B.3 below.

[^7]: We interpret the commenter's use of the term "equal protection" to
    mean that the commenter believes that EPA has performed a harsher
    review of nPB than it has for other substitutes and not a claim that
    EPA has violated the 14^th^ Amendment of the Constitution, which
    applies only to the states and not the federal government.

[^8]: Pharmacodynamics refers to the biochemical and physiological
    effects of chemicals in the body and the mechanism of their actions.

[^9]: Pharmacokinetics refers to the activity or fate of chemicals in
    the body, including the processes of absorption, distribution,
    localization in tissues, biotransformation, and excretion.

[^10]: The blood/air partition coefficient is the ratio of a chemical's
    concentration between blood and air when at equilibrium.

[^11]: iPB is also referred to as 2-bromopropane, 2-propyl bromide, or
    2-BP. Its CAS registry number is 75-26-3.