[Federal Register Volume 72, Number 103 (Wednesday, May 30, 2007)]
[Rules and Regulations]
[Pages 30142-30167]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E7-9707]



[[Page 30141]]

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Part III





Environmental Protection Agency





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40 CFR Part 82



 Protection of Stratospheric Ozone: Listing of Substitutes for Ozone-
Depleting Substances-n-Propyl Bromide in Solvent Cleaning; Protection 
of Stratospheric Ozone: Listing of Substitutes for Ozone-
DepletingSubstances-n-Propyl Bromide in Adhesives, Coatings, and 
Aerosols; Final Rule and Proposed Rule

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

[[Page 30142]]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 82

[EPA-HQ-OAR-2002-0064; FRL-8316-8]
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.

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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 July 30, 2007.

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 
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 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: [email protected]. Notices and 
rulemakings under the SNAP program are available on EPA's Stratospheric 
Ozone World Wide Web site at http://www.epa.gov/ozone/snap/regs.

SUPPLEMENTARY INFORMATION: Table of Contents: 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.

[[Page 30143]]



 Table 1.--Potentially Regulated Entities, by North American Industrial
             Classification System (NAICS) Code or Subsector
------------------------------------------------------------------------
                                    NAICS code
             Category                   or      Description of regulated
                                    subsector           entities
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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 
C3H7Br. Its identification number in Chemical 
Abstracts Service's registry (CAS Reg. No.) is 106-94-5. nPB is used to 
remove wax, oil, and grease from electronics, metal, and other 
materials. It also is used as a carrier solvent in adhesives. Some 
brand names of products using nPB are: Abzol[supreg], EnSolv[supreg], 
and Solvon[supreg] cleaners; Pow-R-Wash[supreg] NR Contact Cleaner, 
Superkleen Flux Remover 2311 and LPS NoFlash NU Electro Contact Cleaner 
aerosols; and Whisper Spray and Fire Retardant Soft Seam 6460 
adhesives.

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, C2Cl3F3, CAS Reg. 
No. 76-13-1
CFC--chlorofluorocarbon
cfm--cubic feet per minute
CFR--Code of Federal Regulations
CNS--central nervous system
DNA--deoxyribonucleic acid
EDSTAC--The Endocrine Disruptor Screening and Testing Advisory 
Committee
EPA--the United States Environmental Protection Agency
FR--Federal Register
GWP--global warming potential
HCFC-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, C3H7Br, CAS Reg. No. 
75-26-3, an isomer of n-propyl bromide; also called 2-bromopropane 
or 2-BP
Koc--organic carbon partition coefficient, for 
determining the tendency of a chemical to bind to organic carbon in 
soil
LC50--the concentration at which 50% of test animals die
LOAEL--Lowest Observed Adverse Effect Level
Log Kow--logarithm of the octanol-water partition 
coefficient, for determining the tendency of a chemical to 
accumulate in lipids or fats instead of remaining dissolved in water
mg/l--milligrams per liter
MSDS--Material Safety Data Sheet
NAICS--North American Industrial Classification System
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, C3H7Br, CAS Reg. No. 
106-94-5; also called 1-bromopropane or 1-BP
NPRM--Notice of Proposed Rulemaking
NTP--National Toxicology Program
NTTAA--National Technology Transfer and Advancement Act
ODP--ozone depletion potential
ODS--ozone-depleting substance
OEHHA--Office of Environmental Health Hazard Assessment of the 
California Environmental Protection Agency
OMB--U.S. Office of Management and Budget
OSHA--the United States Occupational Safety and Health 
Administration
PCBTF--parachlorobenzotrifluoride, CAS Reg. No. 98-56-6
PEL--Permissible Exposure Limit
ppm--parts per million
RCRA--Resource Conservation and Recovery Act
RFA--Regulatory Flexibility Act
RfC--reference concentration
SIP--state implementation plan
SNAP--Significant New Alternatives Policy
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, 
C2Cl3H; also call trichloroethylene
TERA--Toxicological Excellence for Risk Assessment
TLV--Threshold Limit Value\TM\
TSCA--Toxic Substances Control Act
TWA--time-weighted average
UMRA--Unfunded Mandates Reform Act
U.S.C.--United States Code
VMSs--volatile methyl siloxanes
VOC--volatile organic compound
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

[[Page 30144]]

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

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

    On March 18, 1994, EPA published the original rulemaking (59 FR 
13044) that described the process for administering the SNAP program 
and issued the first acceptability lists for substitutes in the major 
industrial use sectors. These sectors include: Refrigeration and air 
conditioning; foam blowing; solvents cleaning; fire suppression and 
explosion protection; sterilants; aerosols; adhesives, coatings and 
inks; and tobacco expansion. These sectors comprise the principal 
industrial sectors that historically consumed large volumes of ozone-
depleting substances.
    Anyone who plans to market or produce a substitute for an 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. 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

[[Page 30145]]

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

III. What is EPA'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                      Substitute               Decision             Further information
----------------------------------------------------------------------------------------------------------------
Metals cleaning, electronics         n-propyl bromide (nPB)  Acceptable............  EPA recommends the use of
 cleaning, and precision cleaning.    as a substitute for                             personal protective
                                      CFC-113 and methyl                              equipment, including
                                      chloroform.                                     chemical goggles, flexible
                                                                                      laminate protective gloves
                                                                                      and chemical-resistant
                                                                                      clothing.
                                                                                     EPA expects that all users
                                                                                      of nPB would comply with
                                                                                      any final Permissible
                                                                                      Exposure Limit that the
                                                                                      Occupational Safety and
                                                                                      Health Administration
                                                                                      issues in the future under
                                                                                      42 U.S.C. 7610(a).
                                                                                     nPB, also known as 1-
                                                                                      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.
    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

[[Page 30146]]

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.
---------------------------------------------------------------------------

    \1\ Smog, also known as ground-level ozone, is produced from 
emissions of volatile organic compounds that react under certain 
conditions of temperature and light.
---------------------------------------------------------------------------

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).
---------------------------------------------------------------------------

    \2\ Also called trichlorethene or TCE, 
C2Cl3H, CAS Reg. No. 79-01-6.
    \3\ Also called PERC, tetrachloroethylene, or tetrachloroethene, 
C2Cl4, CAS Reg. No. 172-18-4.
---------------------------------------------------------------------------

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.
---------------------------------------------------------------------------

    \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).
---------------------------------------------------------------------------

    The global warming potential (GWP) index is a means of quantifying 
the potential integrated climate forcing of various greenhouse gases 
relative to carbon dioxide. Earlier data found a direct 100-year 
integrated GWP (100yr GWP) for nPB of 0.31 (Atmospheric and 
Environmental Research, Inc., 1995). More recent analysis that 
considers both the direct and the indirect GWP of nPB found a 100-yr 
GWP of 1.57 (ICF, 2003a; ICF, 2006a). In either case, the GWP for nPB 
is comparable to or below that of previously approved substitutes in 
these end uses.
    Use of nPB may be controlled as a volatile organic compound (VOC) 
under state implementation plans (SIPs) developed to attain the 
National Ambient Air Quality Standards for ground-level ozone, which is 
a respiratory irritant. Users located in ozone 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 (Koc), the breakdown 
processes in water and hydrolysis half-life, and the volatilization 
half-life indicate that nPB is less persistent in the environment than 
many solvents and would be of low to moderate concern for movement in 
soil. Based on the LC50, the acute concentration at which 
50% of tested animals die, nPB's toxicity to aquatic life is moderate, 
being less than that for some acceptable cleaners (for example, 
trichloroethylene, hexane, d-limonene, and possibly some aqueous 
cleaners) and greater than that for some others (methylene chloride, 
acetone, isopropyl alcohol, and some other aqueous cleaners). The 
LC50 for nPB is 67 mg/l, which is greater than 10 mg/l. 
Based on EPA's criteria for listing under the Toxics Release Inventory 
(U.S. EPA,

[[Page 30147]]

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 Kow 
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
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                          Description of                              Value for trans-1,2-         Value for          Value for methyl
             Property                 environmental property        Value for nPB       dichloro-ethylene      trichloroethylene         chloroform
--------------------------------------------------------------------------------------------------------------------------------------------------------
Koc, organic-carbon partition       Degree to which a           330 (Source: ICF,     32 to 49 (Source:     106 to 460 (Source:     152 (Source: U.S.
 coefficient.                        substance tends to stick    2004a).               ATSDR, 1996).         ATSDR, 1997).           EPA, 1994a).
                                     to soil or move in soil.
                                     Lower values (< 300)*
                                     indicate great soil
                                     mobility; values of 300
                                     to 500 indicate moderate
                                     mobility in soil.
Break down in water...............  Mechanism and speed with    Hydrolysis is         Photolytic            Volatilization and      Volatilization most
                                     which a compound breaks     significant.          decomposition,        biodegradation most     significant;
                                     down in the environment.    Hydrolysis half-      dechlorination and    significant, with       biodegradation and
                                     (Hydrolysis half-life       life of 26 days       biodegradation are    hydrolysis relatively   hydrolysis also
                                     values > 25 weeks* are of   (Source: ICF,         significant;          insignificant.          occur (Source:
                                     concern.)                   2004a).               hydrolysis not        Hydrolysis half-life    ATSDR, 2004).
                                                                                       significant           of 10.7 to 30 months
                                                                                       (Source: ATSDR,       (Source: ATSDR, 1997).
                                                                                       1996).
Volatilization half-life from       Tendency to volatilize and  3.4 hours-4.4 days    3 to 6.2 hours        3.4 hours to 18 days    Hours to weeks
 surface waters.                     pass from water into the    (Source: ICF,         (Source: ATSDR,       (Source: ATSDR, 1997).  (Source: U.S. EPA,
                                     air.                        2004a).               1996).                                        1994a).
LC50 (96 hours) for fathead         Concentration at which 50%  67 mg/L (Source:      108 mg/L (Source:     40.7 to 66.8 mg/L       52.8 to 105 mg/L
 minnows.                            of animals die from         Geiger, 1988).        U.S. EPA, 1980).      (Source: NPS, 1997).    (Source: U.S. EPA,
                                     toxicity after exposure                                                                         1994a).
                                     for 4 days.
log Kow...........................  Logarithm of the octanol/   2.10 (Source: ICF,    -0.48 (Source:        2.38 (Source: LaGrega   2.50 (Source:
                                     water partition             2004a).               LaGrega et al.,       et al., 2001, p.        LaGrega et al.,
                                     coefficient, a measure of                         2001, p. 1119).       1127).                  2001, p. 1127).
                                     tendency to accumulate in
                                     fat. Log Kow values >3*
                                     indicate high tendency to
                                     accumulate.
Bioconcentration factor...........  High factors (>1000)*       23 (Source: HSDB,     5 to 23 (Source:      10 to 100 (Source:      <9 (Source: U.S.
                                     indicate strong tendency    2004).                ATSDR, 1996).         ATSDR, 1997).           EPA, 1994a).
                                     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 (U.S. 
EPA, 1994b. RfC Guidelines; U.S. EPA, 1991. Guidelines for 
Developmental Toxicity Risk Assessment; U.S. EPA, 1995b. Benchmark Dose 
guidelines; U.S. EPA, 1996. Guidelines for Reproductive Toxicity Risk 
Assessment).

[[Page 30148]]

    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

[[Page 30149]]

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 preamble. 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.
---------------------------------------------------------------------------

    \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).
---------------------------------------------------------------------------

    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).
---------------------------------------------------------------------------

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

                        Table 4.--Summary of Endpoints Using Benchmark Response Modeling
----------------------------------------------------------------------------------------------------------------
                                                                                                       Human
                                                                                                     equivalent
                 Endpoint \a\                                  Study                    BMDL\b\    concentration
                                                                                         (ppm)        (HEC)\c\
                                                                                                       (ppm)
----------------------------------------------------------------------------------------------------------------
                                                Liver Effects \d\
----------------------------------------------------------------------------------------------------------------
Liver vacuolation in males (F1 offspring       WIL, 2001 as analyzed in ICF, 2002...          110           116
 generation).
Liver vacuolation in males (F0 parent          WIL, 2001 as analyzed in ICF, 2002...          143           150
 generation).
Liver vacuolation............................  ClinTrials, 1997b as analyzed in ICF,          226           170
                                                2002 and Stelljes & Wood, 2004.
----------------------------------------------------------------------------------------------------------------
                                           Reproductive Effects--Male
----------------------------------------------------------------------------------------------------------------
Sperm motility (F1 offspring generation).....  WIL, 2001 as analyzed in ICF, 2002...          169           177
                                               WIL, 2001 as analyzed in Stelljes &            156           164
                                                Wood, 2004.
Sperm motility (F0 parent generation)........  WIL, 2001 as analyzed in ICF, 2002...          282           296
                                               WIL, 2001 as analyzed in Stelljes &            263           276
                                                Wood, 2004.
Prostate weight (F0 parent generation).......  WIL, 2001 as analyzed in TERA, 2004..          190           200
Sperm count..................................  Ichihara et al., 2000b as analyzed in          232           325
                                                Stelljes & Wood, 2004.

[[Page 30150]]

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

    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 (U.S. 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

[[Page 30151]]

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 (U.S. 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 (U.S. 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

[[Page 30152]]

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 (U.S. EPA 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 
(U.S. 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\.
---------------------------------------------------------------------------

    \7\ We interpret the commenter's use of the term ``equal 
protection'' to mean that the commenter beleives that EPA has 
performend 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.
---------------------------------------------------------------------------

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

[[Page 30153]]

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 (U.S. 
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.'' (U.S. 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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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

[[Page 30154]]

compound in the arterial blood and that the critical metabolic pathways 
scale across species in a manner similar to the ventilation rate (U.S. 
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 (U.S. EPA, 1994b). Recently published data on humans and 
rodents do not decrease the uncertainty regarding the pharmacodynamics 
of nPB; therefore, modification of the uncertainty factor of 3 for 
differences between species 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 
IoGasTM 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

[[Page 30155]]

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 (U.S. 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 
of the June 2003 NPRM 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.
     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 (U.S. EPA, 1996). 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 (U.S. 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

[[Page 30156]]

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; 
HESIS, 2003; Werner, 2003, Weiss Cohen, 2003). 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).
---------------------------------------------------------------------------

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

    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.

[[Page 30157]]

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 (persistence/bioaccumulation/toxicity) 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

[[Page 30158]]

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[deg] C and pH 7.
     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 
(29 U.S.C. 655(b)), 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. Conversely, although section 4(b)(1) of the OSH Act 
prohibits OSHA from regulating a working condition addressed by another 
federal agency's regulations affecting occupational safety or health, 
this provision is overridden with respect to EPA's exercise of 
authority under the Clean Air Act by 42 U.S.C. 7610. That provision 
states: ``(a) Except as provided in subsection (b) of this section, 
this chapter shall not be construed as superseding or limiting the 
authorities and responsibilities, under any other provision of law, of 
the Administrator or any other Federal officer, department, or 
agency.''
    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., U.S. 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.

[[Page 30159]]

    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. Public 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: 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; 40 CFR part 82, 
subpart G, appendices A, B, and D).
    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 section 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,

[[Page 30160]]

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 (U.S. 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 (U.S. 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.
     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

[[Page 30161]]

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 (58 FR 51735, October 4, 1993), 
this action is a ``significant regulatory action.'' It raises novel 
legal or policy issues arising out of legal mandates, the President's 
priorities, or the principles set forth in the Executive Order. 
Accordingly, EPA submitted this action to the Office of Management and 
Budget (OMB) for review under EO 12866 and any changes made in response 
to OMB recommendations have been documented in the docket for this 
action.
    In addition, EPA prepared an analysis of the potential costs and 
benefits associated with this action. This analysis is contained in the 
document ``Analysis of Economic Impacts of 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 lowest 
level that we considered, i.e., 18 ppm (U.S. 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 18 ppm, 
EPA estimates that users would save up to $2 million dollars per year, 
overall (U.S. 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. 
1596.06). This ICR included five types of respondent reporting and 
record-keeping activities pursuant to SNAP regulations: submission of a 
SNAP petition, filing a SNAP//Toxic Substance Control Act (TSCA) 
Addendum, notification for test marketing activity, record-keeping for 
substitutes acceptable subject to use restrictions, and record-keeping 
for small volume uses. 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 
U.S.C. 601(3)--(5). In addition, to establish an alternate small 
business definition, agencies must consult with SBA's Office of 
Advocacy.
    For purposes of assessing the impacts of EPA's June 2003 proposed 
rule on

[[Page 30162]]

small entities, EPA proposed 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 to 
simplify the economic analysis. We solicited comments on the use of 
this alternate definition for this analysis in the June 2003 NPRM and 
received no public comments. EPA also consulted with the SBA's Office 
of Advocacy on the use of an alternate small business definition of 500 
employees. The Office of Advocacy concurred with EPA's use of this 
alternate definition to analysis the economic impacts on small 
businesses from the use of n-propyl bromide as an acceptable substitute 
for use in metals, precision, and electronics cleaning, and in aerosols 
and adhesives end-uses. Therefore, EPA used this alternate definition 
for this final rule. We believe that no small governments or small 
organizations are affected by this rule. This approach slightly reduced 
the number of small businesses included in our analysis and slightly 
increased the percentage of small businesses for whom the analysis 
indicated the use of nPB in metals, precision, and electronics cleaning 
may have an economically significant impact. The number and types of 
small businesses that are subject to this rule have not changed 
significantly since the June 2003 proposal. EPA intends to use this 
alternate definition of ``small business'' for regulatory flexibility 
analyses under the RFA for any other rule related to the use of nPB as 
a chemical alternative to ozone-depleting substances (ODS) for the same 
end uses in the June 2003 NPRM (e.g., adhesives and aerosol solvents).
    After considering the economic impacts of this 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 lists nPB as an acceptable substitute for ODS. 
This rule itself does not impose any binding requirements on users of 
nPB, and therefore will not have a significant economic impact on a 
substantial number of small entities. EPA did however analyze the 
potential economic impacts on small businesses that use nPB for 
cleaning solvents for metals cleaning, electronics cleaning, or 
precision cleaning. The details of EPA's analysis are described in the 
supporting materials for this rulemaking (U.S. EPA, 2007). Based on its 
analysis, EPA believes businesses using nPB-based cleaning solvents for 
metals cleaning, electronics cleaning, or precision cleaning would 
experience significant cost benefits by reducing spending on solvent.

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

[[Page 30163]]

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.

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''), Public Law 104-113, section 12(d) (15 U.S.C. 
272 note) directs EPA to use voluntary consensus standards in its 
regulatory activities unless to do so would be inconsistent with 
applicable law or otherwise impractical. Voluntary consensus standards 
are technical standards (e.g., materials specifications, test methods, 
sampling procedures, and business practices) that are developed or 
adopted by voluntary consensus standards bodies. The NTTAA directs EPA 
to provide Congress, through OMB, explanations when the Agency decides 
not to use available and applicable voluntary consensus standards.
    This action does not involve 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 July 30, 2007.

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.

Availability

IBSA, 2002. Record 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. (EPA-HQ-OAR-2002-0064-0193)
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)

[[Page 30164]]

Steminiski, 2003. July 27, 2003 Comment from J. Steminiski, PhD. 
(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)
U.S. 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
U.S. 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.
U.S. 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 http://www.acgih.org.
ACGIH, 2005. Documentation for Threshold Limit Value for 1-
Bromopropane. 2005. Available online at http://www.acgih.org.
Albemarle, 2003. Product Description for Abzol([supreg]) Cleaners. 
2003. (EPA-HQ-OAR-2002-0064-0148)
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-
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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. ICF 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. (EPA-HQ-OAR-2002-0064-0179)
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)

[[Page 30165]]

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-
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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-
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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. (EPA-HQ-
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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 
(EPA-HQ-OAR-2002-0064-0216)
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. (EPA-
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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. (EPA-HQ-OAR-2002-0064-0128)
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. (EPA-HQ-OAR-2002-0064-
0170)
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, Y.L., 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, Y.K., Suh, J.S., Kim, J.W., Seo, H.H., Kim, 
J.Y., Kim, H.Y., Lee, J.Y., Lee, S.B., Han, J.H., Lee, Y.M., Lee, 
J.Y. ``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. (EPA-HQ-
OAR-2002-0064-0189)
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)
U.S. EPA, 1991. Guidelines for Developmental Toxicity Risk 
Assessment. U.S. Environmental Protection Agency. (A-2001-07, II-A-
51)
U.S. EPA, 1994b. U.S. Environmental Protection Agency (U.S. 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
U.S. 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)
U.S. EPA, 1996. Guidelines for Reproductive Toxicity Risk 
Assessment. U.S. Environmental Protection Agency, Risk Assessment 
Forum, Washington, DC, 630/R-96/009, 1996. (EPA-HQ-OAR-2002-0064-
0109)
U.S. 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 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-
2002-0064-0058).
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.

[[Page 30166]]

Cincinnati, OH. Available online at 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. (EPA-HQ-OAR-2002-0064-0151)
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. Full citation above in ``Human Health'' section.
ICF, 2006c. ICF Consulting. Evaluation of Memorandum from Dr. M. 
Stelljes. May, 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 bromide 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. (EPA-HQ-OAR-2002-0064-0163)
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. Full citation above in ``Human Health'' section.
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. (EPA-HQ-OAR-2002-0064-0168)
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-2002-0064-0068)
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. (EPA-HQ-OAR-2002-0064-0067)
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.
U.S. EPA, 1994b. Full citation above in ``Human Health'' section.
U.S. EPA, 1996. Full citation above in ``Human Health'' section.
U.S. 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. (EPA-HQ-OAR-2002-0064-0171)

[[Page 30167]]

U.S. EPA, 2003. Full citation above for ``Human Health'' section.
U.S. 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.

    Dated: May 15, 2007.
Stephen L. Johnson,
Administrator.

Appendix A: Summary of Decision

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

 [FR Doc. E7-9707 Filed 5-29-07; 8:45 am]
BILLING CODE 6560-50-P