[Federal Register Volume 68, Number 106 (Tuesday, June 3, 2003)]
[Proposed Rules]
[Pages 33284-33316]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-13254]



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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; Proposed Rule

  Federal Register / Vol. 68, No. 106 / Tuesday, June 3, 2003 / 
Proposed Rules  

[[Page 33284]]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 82

[FRL-7504-3]
RIN 2060-AK28


Protection of Stratospheric Ozone: Listing of Substitutes for 
Ozone-Depleting Substances--n-Propyl Bromide

AGENCY: Environmental Protection Agency.

ACTION: Notice of proposed rulemaking.

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SUMMARY: This action proposes to list n-propyl bromide (nPB) as an 
acceptable substitute for ozone-depleting substances (ODSs), subject to 
use conditions, in the solvent cleaning sector and aerosol solvents and 
adhesive end uses under the U.S. Environmental Protection Agency's (EPA 
or ``we'') Significant New Alternatives Policy (SNAP) program. The SNAP 
program implements section 612 of the amended Clean Air Act of 1990 
(CAA), which requires EPA to evaluate substitutes for ODSs in order to 
reduce overall risk to human health and the environment.
    While we find that nPB has a short atmospheric lifetime and low 
ozone depletion potential when emitted from locations in the 
continental U.S., the Agency cautions that significant use of nPB 
closer to the equator poses significant risks to the stratospheric 
ozone layer. Further, if workplace exposure to nPB is poorly 
controlled, it may increase health risks to workers. In the interim, 
until the Occupational Safety and Health Administration (OSHA) develops 
a mandatory workplace exposure limit under Section 6 of the 
Occupational Safety and Health Act, the Agency recommends that users of 
nPB adhere to an acceptable exposure limit of 25 parts per million 
(ppm) over an eight-hour time-weighted average.
    In today's action, EPA proposes that the use of nPB is acceptable 
subject to a use condition, in a limited number of specific 
applications where emissions can be tightly controlled for both 
environmental and exposure concerns. The proposal only allows the use 
of nPB as a solvent in metals, precision, and electronics cleaning, and 
in aerosol solvent and adhesive end-uses. EPA is proposing to list nPB 
as an acceptable substitute for chlorofluorocarbon (CFC)-113, 
hydrochlorofluorocarbon (HCFC)-141b, and methyl chloroform when used in 
aerosol solvent and adhesive end uses, subject to the condition that 
nPB used in these end uses not contain more than 0.05% isopropyl 
bromide by weight before adding stabilizers or other chemicals. We are 
also proposing to list nPB as an acceptable substitute for CFC-113 and 
methyl chloroform in general metals cleaning, electronics cleaning, and 
precision cleaning, subject to the condition that nPB used in these end 
uses not contain more than 0.05% isopropyl bromide by weight before 
adding stabilizers or other chemicals.

DATES: Comments must be received in writing by August 4, 2003.

ADDRESSES: Comments may be submitted by mail to: Air and Radiation 
Docket, Environmental Protection Agency, Mailcode 6102T, 1200 
Pennsylvania Ave., NW., Washington, DC 20460, Attention Docket ID No. 
OAR-2002-0064. Comments may also be submitted electronically, by 
facsimile, or through hand delivery/courier. Follow the detailed 
instructions as provided at the beginning of the ``supplementary 
information'' section.

FOR FURTHER INFORMATION CONTACT: For further information about this 
proposed rule, contact Margaret Sheppard by telephone at (202) 564-
9163, or by e-mail at [email protected]. Notices and 
rulemakings under the SNAP program are available on EPA's Stratospheric 
Ozone World Wide Web site at http://www.epa.gov/ozone/snap/regs.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. General Information
    A. Regulated entities
    B. How can I get copies of related information?
    C. How and to whom do I submit comments?
    D. How should I submit CBI to the agency?
    E. Acronyms and abbreviations used in the preamble
II. How does the Significant New Alternatives Policy (SNAP) program 
work?
    A. What are the statutory requirements and authority for the 
SNAP program?
    B. How do the regulations for the SNAP program work?
    C. Where can I get additional information about the SNAP 
program?
III. Is EPA listing n-propyl bromide as an acceptable substitute for 
ozone-depleting substances?
    A. What is EPA proposing today?
    B. What is n-propyl bromide?
    C. What industrial sectors are included in our proposed 
decision?
IV. What did EPA consider in preparing today's proposal?
    A. Toxicity
    1. What Acceptable Exposure Limit is EPA recommending for n-
propyl bromide, and why?
    a. Summary of toxicity studies
    b. Derivation of an AEL for nPB
    c. Overview of the Center for Evaluation of Risk to Human 
Reproduction (CERHR) Expert Panel Report
    d. AELs suggested by other reviewers and outside parties
    e. Feasibility of meeting the AEL for nPB in each sector
    2. Are there other entities that may set workplace standards for 
nPB?
    3. Is the general population exposed to too much nPB?
    4. What limit is EPA setting on isopropyl bromide contamination 
of n-propyl bromide as a condition of acceptability, and why?
    B. Ozone depletion potential
    C. Global warming potential
    D. Flammability
    E. Other environmental concerns
    F. Comparison of nPB to other solvents
V. What other factors did EPA consider that are unique to nPB?
    A. Continued review of nPB by other federal and international 
programs
    B. Potential market for n-propyl bromide
    C. Estimated economic impacts on businesses
VI. How is EPA responding to comments on the advance notice of 
proposed rulemaking and December 18, 2000 notice of data 
availability?
VII. What should I include in my comments on EPA's proposal?
VIII. What is the federal government doing to help businesses use 
nPB safely?
IX. How can I use nPB as safely as possible?
X. Statutory and Executive Order Reviews
XI. References

I. General Information

A. Regulated Entities

    Today's proposal would regulate the use of n-propyl bromide as a 
solvent used in industrial equipment for metals cleaning, electronics 
cleaning, or precision cleaning, and as an aerosol solvent and a 
carrier solvent in adhesives. Businesses that currently might be using 
nPB, or might want to use it in the future, include:
    [sbull] Businesses that clean metal parts, such as automotive 
manufacturers, machine shops, machinery manufacturers, and 
electroplaters.
    [sbull] Businesses that manufacture electronics or computer 
equipment.
    [sbull] 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.
    [sbull] Foam fabricators that glue pieces of polyurethane foam 
together or foam cushion manufacturers that glue fabric around a 
cushion.
    [sbull] Furniture manufacturers that use adhesive to attach wood 
parts to floors, tables and counter tops.
    Regulated entities may include:

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 Table 1.--Potentially Regulated Entities, by North American Industrial
             Classification System (NAICS) Code or Subsector
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                                  NAICS
           Category              code 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......................       336   Transportation equipment
                                            manufacturing
Industry......................       337   Furniture and related product
                                            manufacturing
Industry......................    326150   Urethane and other foam
                                            product (except polystyrene)
                                            manufacturing
------------------------------------------------------------------------

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

B. How Can I Get Copies of Related Information?

1. Docket
    EPA has established an official public docket for this action under 
Docket ID No. OAR-2002-0064 (continuation of Docket A-2001-07). The 
official public docket consists of the documents specifically 
referenced in this action, any public comments received, and other 
information related to this action. Hard copies of documents from prior 
to the public comment period are found under Docket ID No. A-2001-07. 
Although a part of the official docket, the public docket does not 
include Confidential Business Information (CBI) or other information 
whose disclosure is restricted by statute. The official public docket 
is the collection of materials that is available for public viewing at 
the Air and Radiation Docket in the EPA Docket Center, (EPA/DC) EPA 
West, Room B102, 1301 Constitution Ave., NW., Washington, DC. The EPA 
Docket Center Public Reading Room is open from 8:30 a.m. to 4:30 p.m., 
Monday through Friday, excluding legal holidays. The telephone number 
for the Reading Room is (202) 566-1742, and the telephone number for 
the Air and Radiation Docket is (202) 566-1742.
2. Electronic Access
    An electronic version of the public docket is available through 
EPA's electronic public docket and comment system, EPA Dockets. You may 
use EPA Dockets at http://www.epa.gov/edocket/ to submit or view public 
comments, access the index listing of the contents of the official 
public docket, and to access those documents in the public docket that 
are available electronically. Once in the system, select ``search,'' 
then key in the appropriate docket identification number.
    Certain types of information will not be placed in the EPA 
Dockets.Information claimed as CBI and other information whose 
disclosure is restricted by statute, which is not included in the 
official public docket, will not be available for public viewing in 
EPA's electronic public docket. EPA's policy is that copyrighted 
material will not be placed in EPA's electronic public docket but will 
be available only in printed, paper form in the official public docket. 
Although not all docket materials may be available electronically, you 
may still access any of the publicly available docket materials through 
the docket facility identified in section I.B.1. above.
    For public commenters, it is important to note that EPA's policy is 
that public comments, whether submitted electronically or in paper, 
will be made available for public viewing in EPA's electronic public 
docket as EPA receives them and without change, unless the comment 
contains copyrighted material, CBI, or other information whose 
disclosure is restricted by statute. When EPA identifies a comment 
containing copyrighted material, EPA will provide a reference to that 
material in the version of the comment that is placed in EPA's 
electronic public docket. The entire printed comment, including the 
copyrighted material, will be available in the public docket.
    Public comments submitted on computer disks that are mailed or 
delivered to the docket will be transferred to EPA's electronic public 
docket. Public comments that are mailed or delivered to the Docket will 
be scanned and placed in EPA's electronic public docket. Where 
practical, physical objects will be photographed, and the photograph 
will be placed in EPA's electronic public docket along with a brief 
description written by the docket staff.

C. How and to Whom Do I Submit Comments?

    You may submit comments electronically, by mail, by facsimile, or 
through hand delivery/courier. To ensure proper receipt by EPA, 
identify the appropriate docket identification number in the subject 
line on the first page of your comment. Please ensure that your 
comments are submitted within the specified comment period. Comments 
received after the close of the comment period will be marked ``late.'' 
EPA is not required to consider these late comments. If you wish to 
submit CBI or information that is otherwise protected by statute, 
please follow the instructions in section I.D. Do not use EPA Dockets 
or e-mail to submit CBI or information protected by statute.
    1. Electronically. If you submit an electronic comment as 
prescribed below, EPA recommends that you include your name, mailing 
address, and an e-mail address or other contact information in the body 
of your comment. Also include this contact information on the outside 
of any disk or CD ROM you submit, and in any cover letter accompanying 
the disk or CD ROM. This ensures that you can be identified as the 
submitter of the comment and allows EPA to contact you in case EPA 
cannot read your comment due to technical difficulties or needs further 
information on the substance of your comment. EPA's policy is that EPA 
will not edit your comment, and any identifying or contact information 
provided in the body of a comment will be included as part of the 
comment that is placed in the official public docket, and made 
available in EPA's electronic public docket. If EPA cannot read your 
comment due to technical difficulties and cannot contact you for 
clarification, EPA may not be able to consider your comment.
    Your use of EPA's electronic public docket to submit comments to 
EPA electronically is EPA's preferred method for receiving comments. Go 
directly to EPA Dockets at http://www.epa.gov/edocket, and follow the 
online instructions for submitting comments. To access EPA's electronic 
public docket from the EPA Internet Home Page, select ``Information 
Sources,'' ``Dockets,'' and ``EPA Dockets.'' Once in the system, select 
``search,'' and then key in Docket ID No. OAR-2002-0064. The system is 
an ``anonymous access'' system, which means EPA will not know your 
identity, e-mail address, or other contact information unless you 
provide it in the body of your comment.
    Comments may be sent by electronic mail (e-mail) to A-And-R-

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[email protected], Attention Docket ID No. OAR-2002-0064. In contrast to 
EPA's electronic public docket, EPA's e-mail system is not an 
``anonymous access'' system. If you send an e-mail comment directly to 
the Docket without going through EPA's electronic public docket, EPA's 
e-mail system automatically captures your e-mail address. E-mail 
addresses that are automatically captured by EPA's e-mail system are 
included as part of the comment that is placed in the official public 
docket, and made available in EPA's electronic public docket.
    You may submit comments on a disk or CD ROM that you mail to the 
mailing address identified in section I.B.1. These electronic 
submissions will be accepted in WordPerfect or ASCII file format. Avoid 
the use of special characters and any form of encryption.
    2. By Mail. Send two copies of your comments to: Air and Radiation 
Docket, Environmental Protection Agency, Mailcode: 6102T, 1200 
Pennsylvania Ave., NW., Washington DC, 20460, Attention: Docket ID No. 
OAR-2002-0064.
    3. By Hand Delivery or Courier. Deliver your comments to: EPA 
Docket Center, (EPA/DC) EPA West, Room B102, 1301 Constitution Ave., 
NW., Washington, DC, Attention Docket ID No. OAR-2002-0064. Such 
deliveries are only accepted during the Docket's normal hours of 
operation as identified in section I.B.1.
    4. By Facsimile. Fax your comments to: 202-566-1741, Attention: 
Docket ID No. OAR-2002-0064.

D. How Should I Submit CBI to the Agency?

    Do not submit information that you consider to be CBI 
electronically through EPA's electronic public docket or by e-mail. 
Send or deliver information identified as CBI only to the following 
address: Margaret Sheppard, U.S. EPA, 4th floor, 501 3rd Street NW., 
Washington DC 20001, via delivery service. You may claim information 
that you submit to EPA as CBI by marking any part or all of that 
information as CBI (if you submit CBI on disk or CD ROM, mark the 
outside of the disk or CD ROM as CBI and then identify electronically 
within the disk or CD ROM the specific information that is CBI). 
Information so marked will not be disclosed except in accordance with 
procedures set forth in 40 CFR part 2.
    In addition to one complete version of the comment that includes 
any information claimed as CBI, a copy of the comment that does not 
contain the information claimed as CBI must be submitted for inclusion 
in the public docket and EPA's electronic public docket. If you submit 
the copy that does not contain CBI on disk or CD ROM, mark the outside 
of the disk or CD ROM clearly that it does not contain CBI. Information 
not marked as CBI will be included in the public docket and EPA's 
electronic public docket without prior notice. If you have any 
questions about CBI or the procedures for claiming CBI, please consult 
the person identified in the FOR FURTHER INFORMATION CONTACT section.

E. Acronyms and Abbreviations Used in the Preamble

    Below is a list of acronyms and abbreviations used in this 
document.
    1,1,1--the ozone-depleting chemical 1,1,1-trichloroethane, CAS Reg. 
No. 71-55-6; also called TCA, methyl chloroform, or MCF
    1-BP--the chemical 1-bromopropane, C3H7Br, 
CAS Reg. No. 106-94-5; also called n-propyl bromide or nPB
    2-BP--the chemical 2-bromopropane, C3H7Br, 
CAS Reg. No. 75-26-3; also called isopropyl bromide or iPB
    2-D--two-dimensional
    3-D--three dimensional
    ACGIH--American Congress of Governmental Industrial Hygienists
    AEL--acceptable exposure limit
    AFEAS--Alternative Flurocarbon Environmental Acceptability Study
    AIC--Akaike Information Criterion
    AIHA--American Industrial Hygienists Association
    ANPRM--Advance Notice of Proposed Rulemaking
    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
    BMR--benchmark response
    BSOC--Brominated Solvents Consortium
    CAA--Clean Air Act
    CAS Reg. No.--Chemical Abstracts Service Registry Identification 
Number
    CBI--Confidential Business Information
    CERHR--Center for the Evaluation of Risks to Human Reproduction
    CFC-113--the ozone-depleting chemical trifluorotrichloroethane, 
C2Cl3F3, CAS Reg. No. 76-13-1
    CFCs--chlorofluorocarbons
    CFR--Code of Federal Regulations
    CNS--Central nervous system
    EPA--the United States Environmental Protection Agency
    FR--Federal Register
    GLP--Good Laboratory Practice
    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 1,1,1-trichloro-2-
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-pentafluoro-propane, CAS Reg. No. 422-
56-0 and 3,3-dichloro-1,1,2,2,3-pentafluoropropane, CAS Reg. No. 507-
55-1
    HCFCs--hydrochlorofluorocarbons
    HEC--human equivalent concentration
    HESIS--Hazard Evaluation System and Information Service of the 
California Department of Health Services
    HFC-245fa--the chemical 1,1,3,3,3-pentafluoropropane, CAS Reg. No. 
460-73-1
    HFC-365mfc--the chemical 1,1,3,3,3-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
    HFCs--hydrofluorocarbons
    HFEs--hydrofluoroethers
    HHE--health hazard evaluation
    HSIA--Halogenated Solvents Industry Alliance
    IARC--International Agency for Research on Cancer
    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
    IPCC--International Panel on Climate Change
    IRTA--Institute for Research and Technical Assistance
    LOAEL--Lowest Observed Adverse Effect Level
    MF--modifying factor
    MSDS--Material Safety Data Sheet
    NAICS--North American Industrial Classification System
    NESHAP--National Emission Standards for Hazardous Air Pollutants
    NIEHS--National Institute of Environmental Health Services
    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
    OMB--U.S. Office of Management and Budget

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    OSHA--U.S. Occupational Safety and Health Administration
    PCBTF--parachlorobenzotrifluoride, CAS Reg. No. 98-56-6
    PEL--Permissible Exposure Limit
    PERC--perchloroethylene, also called tetrachloroethylene; 
C2Cl4, CAS Reg. No. 127-18-4
    POD--point of departure
    ppm--parts per million
    RCRA--Resource Conservation and Recovery Act
    RFA--Regulatory Flexibility Act
    RfC--reference concentration
    RfD--reference dose
    SBREFA--Small Business Regulatory Enforcement Fairness Act
    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 1,1,1, methyl chloroform, or MCF
    TCE--trichloroethylene, C2Cl3H, CAS Reg. No. 
79-01-6
    TEAP--Technical and Economic Assessment Panel of the United Nations 
Environmental Programme
    TSCA--Toxic Substances Control Act
    TWA--time-weighted average
    UF--uncertainty factor
    UMRA--Unfunded Mandates Reform Act
    UNEP--United Nations Environmental Programme
    VMSs--volatile methyl siloxanes
    VOC--volatile organic compound

II. How Does the Significant New Alternatives Policy (SNAP) Program 
Work?

A. What Are the Statutory Requirements and Authority for the SNAP 
Program?

    Section 612 of the Clean Air Act (CAA) authorizes EPA to develop a 
program for evaluating alternatives to ozone-depleting substances, 
referred to as the Significant New Alternatives Policy (SNAP) program. 
The major provisions of section 612 are:
    [sbull] 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.
    [sbull] 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.
    [sbull] 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.
    [sbull] 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.
    [sbull] 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.
    [sbull] 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 our 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 produces a substitute for an ODS 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 chemical manufacturers, 
but may include importers, formulators or end-users when they are 
responsible for introducing a substitute into commerce.
    The Agency has identified four possible decision categories for 
substitutes: acceptable; acceptable subject to use conditions; 
acceptable subject to narrowed use limits; and unacceptable.
    Use conditions and narrowed use limits are both considered ``use 
restrictions'' and are explained below. Substitutes that are deemed 
acceptable with no use restrictions (no use conditions or narrowed use 
limits) can be used for all applications within the relevant sector 
end-use. Substitutes that are acceptable subject to use restrictions 
may be used only in accordance with those restrictions. It is illegal 
to replace an ODS with a substitute listed as unacceptable.
    After reviewing a substitute, the Agency may make a determination 
that a substitute is acceptable only if certain conditions of use are 
met to minimize risks to human health and the environment. We describe 
such substitutes as ``acceptable subject to use conditions.'' If you 
use these substitutes without meeting the associated use conditions, 
you use these substitutes in an unacceptable manner and you could be 
subject to enforcement for violation of section 612 of the Clean Air 
Act.
    For some substitutes, the Agency may permit a narrowed range of use 
within a sector (that is, we may limit the use of a substitute to 
certain end-uses or specific applications within an industry sector), 
to allow alternatives to be used in specific uses that would otherwise 
be deemed unacceptable. 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 specified as acceptable in 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

[[Page 33288]]

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, you are not 
required to follow these statements to use a substitute unless they 
specifically reference regulatory requirements. 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 
application of these substitutes, regardless of any regulatory 
requirements. In many instances, the information simply refers to sound 
operating practices that have already been identified in existing 
industry and/or building-code standards. Thus, many of the comments, if 
adopted, would not require the affected industry to make significant 
changes in existing operating practices.

C. Where Can I Get Additional Information About the SNAP Program?

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

III. Is EPA Listing n-Propyl Bromide as an Acceptable Substitute for 
Ozone-Depleting Substances?

A. What Is EPA Proposing Today?

    EPA is proposing today to list n-propyl bromide (nPB) acceptable, 
subject to use conditions, for use as a substitute for CFC-113 and 
methyl chloroform \1\ in metals, precision and electronics cleaning, 
and acceptable, subject to use conditions, for use as a substitute for 
CFC-113, methyl chloroform and HCFC-141b in adhesives and aerosol 
solvent end uses. The use conditions for each end use provide that nPB 
not contain more than 0.05% isopropyl bromide (iPB)\2\ by weight before 
adding stabilizers or other chemicals. By this, we mean the chemical n-
propyl bromide that is produced by the manufacturer or reclaimed by a 
recycler before other substances are added, such as stabilizers, other 
solvents, or adhesive solids. End users would need to keep 
documentation for two years from the date on the documentation to show 
that the nPB-based product that they are using contains no more than 
0.05% iPB in the nPB. EPA's decision is based upon comparing 
environmental and health risks associated with the use of nPB in 
specific applications in the United States, compared to other available 
alternatives. Based on our review, the impact of using nPB in the U.S. 
does not warrant listing the chemical as an unacceptable substitute 
under the SNAP program.
---------------------------------------------------------------------------

    \1\ Methyl chloroform is also referred to as 1,1,1-
trichloroethane, TCA, or 1,1,1.
    \2\ iPB is also referred to as 2-bromopropane, 2-propyl bromide, 
or 2-BP. Its CAS registration number is 75-26-3.
---------------------------------------------------------------------------

    We recommend, but do not require, that users in all industrial 
sectors adhere to EPA's recommended guideline for worker exposure of 25 
parts per million (ppm) over an eight-hour time-weighted average. While 
we believe it is possible to achieve the recommended exposure limit of 
25 ppm in the kinds of applications listed above, we are concerned 
about potentially high emissions and exposure levels of nPB in adhesive 
applications in particular. Consequently, EPA intends to work with the 
National Institute for Occupational Safety and Health (NIOSH) to 
develop information for employers and workers at facilities that use, 
or could use, nPB. NIOSH and state occupational safety and health 
agencies will provide technical assistance to help ensure a safe 
workplace environment if owners or workers request it.
    EPA strongly recommends that users follow responsible use practices 
suggested by the manufacturer when using nPB. You can also reduce risk 
in the workplace by monitoring workers' levels of exposure to nPB. 
These practices will reduce the risk of toxic effects to workers, as 
well as reducing the impact of emissions on the environment.

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[reg], EnSolv[reg], and 
Solvon[reg] cleaners, and Whisper Spray and Fire Retardant Soft Seam 
6460 adhesives.

C. What Industrial Sectors Are Included in Our Proposed Decision?

    EPA has received petitions under CAA Section 612(d) to add nPB to 
the list of acceptable alternatives for CFC-113, methyl chloroform, and 
HCFC-141b in the solvent cleaning sector for general metals, precision, 
and electronics cleaning, as well as in aerosol solvent and adhesive 
applications.\3\ Today's proposal does not list nPB as a substitute for 
HCFC-141b for the solvent cleaning sector, but does list nPB as an 
acceptable substitute for HCFC-141b, subject to use conditions, for 
aerosol solvents. This is because EPA previously listed HCFC-141b as 
unacceptable for use in non-aerosol solvent cleaning applications 
because of the availability of safer alternatives (59 FR 13090; March 
18, 1994), and listed HCFC-141b as acceptable for use in aerosol 
solvents. No one may legally use HCFC-141b for non-aerosol solvent 
cleaning and, therefore, no one would substitute for its use.
---------------------------------------------------------------------------

    \3\ EPA also received petitions for using nPB in the foam 
blowing and fire suppression sectors. Because the information in 
these petitions about the use of nPB is incomplete, EPA was unable 
to consider them. Therefore, today's action does not address nPB's 
use in the foam blowing and fire suppression sectors.
---------------------------------------------------------------------------

    The proposal for aerosol solvents only applies to a limited number 
of aerosol solvent applications because of the Nonessential Products 
Ban promulgated under Section 610 of the Act which prohibits the sale, 
distribution, or offer for sale or distribution in interstate commence 
of many products containing CFCs and HCFCs. All aerosol products, 
pressurized dispensers and foam products containing or manufactured 
with CFCs and HCFCs--except those specifically exempted by the 
regulations at 40 CFR part 82, subpart C, and those that are listed as 
essential medical devices by the Food and Drug Administration at 21 CFR 
2.125(e)--are banned from sale and distribution in the

[[Page 33289]]

United States. Users of aerosol solvents can purchase them only for 
those applications that are exempted from the Non-Essential Products 
Ban. The SNAP program applies to the use of substitutes for ODSs, and 
thus, applies only to those applications where ODSs may be used. 
Therefore, today's proposed listing only applies to those specific 
aerosol solvent applications where ODSs are allowed to be sold. This 
list of permissible uses is subject to change. Of the allowable 
applications for aerosol solvents, it is most likely that nPB would be 
used as a solvent in:
    [sbull] Lubricants, coatings, or cleaning fluids for electrical or 
electronic equipment;
    [sbull] Lubricants, coatings, or cleaning fluids for aircraft 
maintenance; or
    [sbull] Spinnerrette lubricants and cleaning sprays used in the 
production of synthetic fibers.
    In addition, no one has specifically stated that they use, or 
intend to use, nPB in coatings or inks. Thus, our proposed ruling only 
addresses nPB use in the adhesives end use, in the adhesives, coatings, 
and inks sector. We would require a separate SNAP submission and 
additional information on nPB use and exposure data in coatings and 
inks to consider its acceptability in those applications.
    EPA notes that the SNAP program currently does not cover some uses 
of solvents, such as manual cleaning, carriers for flame retardants, 
dry cleaning, or paint stripping. Ozone-depleting solvents were never 
used in significant quantities in these applications, compared to 
applications that are covered by the SNAP program, such as vapor 
degreasing or cold batch cleaning. For further discussion, see the 
original SNAP rule (March 18, 1994; 59 FR 13089-13090 and 59 FR 13117-
13120).
    We summarize our proposed actions by sector and end use in Table 2 
below.

                           Table 2.--Summary of Proposed Actions by Sector and End Use
----------------------------------------------------------------------------------------------------------------
                                                                             as a substitute for these ozone
                                                                                  depleting substances:
For this industrial sector...     in this end      we propose to list  -----------------------------------------
                                    use...         nPB as follows...                     methyl
                                                                           CFC-113     chloroform     HCFC-141b
----------------------------------------------------------------------------------------------------------------
Solvents Cleaning............  Metals Cleaning.  Acceptable, subject              X             X   ............
                                                  to use conditions\1\.
                               Electronics       Acceptable, subject              X             X   ............
                                Cleaning.         to use conditions\1\.
                               Precision         Acceptable, subject              X             X   ............
                                Cleaning.         to use conditions\1\.
------------------------------
Aerosols.....................  Aerosol Solvents  Acceptable, subject              X             X             X
                                                  to use conditions\1\.
------------------------------
Adhesives, Coatings, and Inks  Adhesives.......  Acceptable, subject              X             X            X
                                                  to use conditions\1\.
----------------------------------------------------------------------------------------------------------------
\1\ In order to use nPB, the nPB would have to contain no more than 0.05% iPB by weight before adding
  stabilizers or other chemicals.

    At the end of today's action, you will find language that we are 
proposing to add as Appendix L to subpart G of 40 CFR part 82 to 
summarize our proposed listing decisions. Information contained in the 
``Further Information'' column of those tables provides additional 
information on nPB. Although EPA expects nPB users to conform to all 
information shown in Appendix L, the ``further information'' is not 
part of the regulatory decision, and, therefore, is not mandatory. 
Also, there may be other legal obligations pertaining to the 
manufacture, use, handling, disposal of nPB that are not included in 
the comments listed in Appendix L.

IV. What Did EPA Consider for Today's Acceptability Decision?

    To assess the acceptability of any substitute, including nPB, EPA 
reviews the environmental and health risks potentially posed by the 
substitute, including ozone depletion potential, global warming 
potential, flammability, and toxicity. Today's action on nPB follows 
the publication of an Advanced Notice of Proposed Rulemaking (ANPRM) 
published in the Federal Register on February 18, 1999, at 64 FR 8043. 
The ANPRM provided the public an opportunity to review the information 
available to the Agency at that time, and requested additional 
information and comment to assist in the development of regulatory 
options. In particular, the ANPRM asked for information on those key 
parameters where information was limited--that is, the toxicity, ozone 
depletion potential, and market potential of nPB. The Agency also 
issued a notice on December 18, 2000 which provided the public with an 
update on the information EPA had received regarding nPB's ODP and 
toxicity, and provided a summary of anticipated next steps in 
developing regulations under SNAP for nPB (65 FR 78977).
    Based on all information now available, EPA is proposing to find 
nPB acceptable subject to use conditions. The Agency is concerned that 
excessive exposure to nPB can pose risks of adverse health effects and 
is recommending a workplace exposure guideline that we believe will 
protect workers who are exposed to this chemical. EPA is basing this 
recommendation on several factors, including a review of the 
toxicological literature and a subsequent risk evaluation conducted 
according to EPA guidelines (adjusted to represent workplace exposure), 
and consideration of risk management principles. EPA finds that it is 
possible to reduce workplace exposure to nPB to acceptable levels with 
commonly available control equipment or ventilation equipment. Thus, 
the Agency has concluded that it is appropriate to list nPB as 
acceptable because there is evidence that it can be used in a way that 
does not present greater risk than other substitutes.
    Based on these data, the Agency is proposing to list nPB as 
acceptable, subject to a use condition, for the non-aerosol solvents 
cleaning sector, aerosol solvents end use, and adhesives end use 
because we believe it is feasible to meet the recommended AEL of 25 ppm 
in the solvents cleaning sector, the aerosol solvents end use, and the 
adhesives end use. However, EPA expects users to defer to any 
permissible exposure limit ultimately established by OSHA. We note that 
section 6 of the Occupational Safety and Health Act requires OSHA to 
make specific legal findings to support a standard. Specifically, under 
the case law OSHA can set a standard only where there is ``substantial 
evidence'' that the particular standard will provide

[[Page 33290]]

``significant'' risk reduction of a ``material'' adverse health effect 
to workers. Because OSHA operates under a different statute, employs 
different methodology, and will presumably have additional data at some 
point in the future, OSHA's derivation of a permissible exposure limit 
(PEL) may result in a different number than the AEL we set using EPA's 
own methodology and the data available today.
    Today's proposed decision to find nPB acceptable under the SNAP 
program is based in part on its relatively low ozone depletion 
potential when emitted within the continental United States. However, 
the ODP of nPB varies with latitude; therefore, this decision should 
not guide decisions of other countries. For example, nPB emitted closer 
to the equator has a significantly higher ozone depleting potential 
than nPB emitted from the middle and northern latitudes, which include 
the continental United States (for a further discussion, see section 
IV.B. below on Ozone Depletion Potential). EPA recommends that any 
decisions on the use of nPB outside the U.S. should be based on 
latitude-specific ODPs and volumes of the chemical projected to be used 
in those regions.

A. Toxicity

    A primary concern regarding nPB use in the United States is its 
potential adverse health effects to exposed workers. Since EPA 
recommended a preliminary exposure guideline in 1999, additional 
studies have been conducted on the toxicity of nPB and its isomer, iPB. 
EPA has reviewed available toxicity data in order to develop a 
contamination limit for iPB and an Acceptable Exposure Limit (AEL)\4\ 
for occupational exposure to nPB that are protective of human health. 
EPA has also reviewed workplace exposure measurements from several 
facilities where nPB has been used.
---------------------------------------------------------------------------

    \4\ An AEL is the SNAP program's generic term for an eight-hour 
time-weighted average occupational exposure limit.
---------------------------------------------------------------------------

1. What Acceptable Exposure Limit Is EPA Recommending for n-Propyl 
Bromide, and Why?
    Today, EPA is recommending an AEL for nPB of 25 ppm as an eight-
hour time-weighted average. Based upon currently available data, EPA 
believes that workers can be exposed to an average nPB concentration of 
25 ppm without appreciable risk of adverse health effects. In addition, 
like many halogenated solvents, nPB has the potential to be absorbed 
through the skin, so we recommend avoiding skin exposure to nPB by 
wearing protective clothing and flexible laminated gloves. The 
discussion below describes the derivation of the recommended AEL of 25 
ppm for workplace exposure.
    a. Summary of toxicity studies. EPA reviewed all the studies listed 
in docket numbers A-2001-07 and A-91-42 and the studies cited as 
references in Section XI at the end of this preamble. The 
epidemiological data on nPB are limited. An anecdotal report by Sclar 
described neurotoxic effects seen in one patient who used an nPB-based 
solvent (Sclar, 1999). Another recently published paper describes three 
women exhibiting signs of peripheral and central nervous system 
toxicity, such as stumbling, numbness, urinary incontinence, diarrhea, 
nausea, difficulty in concentrating, dizziness, and headaches which was 
attributed to nPB exposure (Ichihara, 2002a). Because detailed exposure 
data are not available in either of these papers, it is difficult to 
use this information in a risk assessment. Vibration sense deficits, 
decreased nerve conduction, and reduced scores on neurological 
functional tests were reported in female workers in China exposed to 
nPB between <1 ppm and 49 ppm (Ichihara et al., 2002b). The study 
authors concluded that their findings suggest that exposure to nPB at 
levels below or around 50 ppm may affect peripheral and central nervous 
system function. However, because only an abstract of the study was 
available to EPA, it was not possible to determine if the exposures and 
effects were well-characterized or if the sample was large enough to 
draw reliable conclusions. As discussed below in section IV.A.1.e, 
``Feasibility of meeting the AEL for nPB in each industrial sector,'' 
NIOSH has performed a number of health hazard evaluations with measured 
workplace exposures to nPB. However, only one of these studies 
attempted to assess health effects (NIOSH, 2002). In this study, NIOSH 
conducted a voluntary medical survey and performed a complete blood 
count on those workers who chose to participate (43 out of 70 workers 
participated). The medical survey included questions on whether workers 
had headaches at least once per week, and whether workers had 
difficulty having children. No exposure-response relationship could be 
identified from these data. The survey was not designed to fully 
characterize effects on the reproductive system, nor did the study 
employ a control group (a group of workers who were not exposed to 
nPB), further limiting the utility of this data for risk assessment.
    The acute toxicity of nPB has been studied in Sprague-Dawley rats 
for inhalation (Elf Atochem, 1997), oral (Elf Atochem, 1993), and 
dermal (Elf Atochem, 1995b) routes of exposure. The 4-hour LC50 (lethal 
concentration for 50% of the test animals) for inhalation of nPB was 
35,000 mg/m3 (Elf Atochem, 1997), with death resulting from pulmonary 
edema. The LD50 (lethal dose for 50% of the test animals) for gavage 
dosing of nPB was greater than 2,000 mg/kg (Elf Atochem, 1993).
    Animals receiving 2,000 mg/kg nPB dermally (with occlusion of the 
exposure area) showed no cutaneous reactions and no evidence of 
toxicity (Elf Atochem, 1995b). A skin sensitization test in Guinea pigs 
was also negative (Elf Atochem, 1995c).
    Key chronic and subchronic toxicological studies on nPB include a 
28-day inhalation study (ClinTrials, 1997a), a 90-day inhalation study 
(ClinTrials, 1997b), a two-generation reproductive toxicity study (WIL, 
2001), and various papers and abstracts published in peer-reviewed 
scientific journals (Ichihara, 1998, 1999, 2000a, 2000b; Kim, 1999; 
Wang, 1999; Yu, 2001; Ichihara 2002a, 2002b). The results of these 
studies consistently show that sensitive health endpoints \5\ (i.e., 
the biological effects occurring at the lowest levels of nPB exposure) 
include effects on the liver (centrilobular vacuolation--cellular 
changes in the central area of the liver) and on the male reproductive 
system (decreases in absolute and relative seminal vesicle weights, and 
reduced sperm count, motility and maturation, and effects on sperm 
shape).
---------------------------------------------------------------------------

    \5\ An endpoint is an observable or measurable biological event 
or chemical concentration (e.g., metabolite concentration in a 
target tissue) used as an index of an effect of a chemical exposure.
---------------------------------------------------------------------------

    The ClinTrials 90-day inhalation study showed liver effects at 
exposures of 400 ppm and above, which is consistent with the effects 
seen by Kim et al. (1999). Effects of nPB on the central and peripheral 
nervous system have also been reported, including peripheral nerve 
degeneration and axonal swelling in the spinal cord at 1000 ppm (Yu, 
2001), degeneration of the myelin of peripheral nerves at 800 ppm 
(Ichihara, 1999), and significantly decreased hind limb grip strength 
(a measure of motor nerve function) at 400 ppm (Ichihara, 2000b).
    Concerns over potential reproductive toxicity associated with nPB 
were initially raised because exposure to iPB,

[[Page 33291]]

a structural analog of nPB, was associated with significant 
reproductive effects in both male and female workers (Kim, 1996; Park, 
1997; Ichihara, 1997). In animal studies, iPB has been shown to induce 
estrous cycle alterations, decreases in accessory sex gland weights 
(e.g, seminal vesicle, prostate), reductions in sperm counts and sperm 
motility, and changes in sperm morphology (Yu, 1997; Ichihara, 1997; 
Kamijima, 1997). Results presented by Ichihara and colleagues indicated 
that nPB exerts some level of reproductive toxicity in rats (Ichihara 
et al., 1998, 1999; Wang, 1999).
    More recently, two studies have reported effects of nPB on the 
female reproductive system in rats. In the first study, female rats 
were dosed at 0, 200, 400, and 800 ppm for eight hours a day for 7 
weeks. Tests of vaginal smears showed a significant increase in the 
number of irregular estrous cycles with extended diestrus \6\ in the 
400 and 800 ppm dose groups, and dose dependent reduction of the number 
of normal antral follicles in the 400 ppm group (Yamada, 2003). In the 
second study, female rats were exposed to 1000 ppm nPB for 7 days per 
week for three weeks. The ratio of the number of estrous cycles of 6 
days or longer to the total number of estrous cycles was calculated for 
the 1000 ppm exposure group and the control group. This ratio was two 
times higher in the exposed animals than controls, however, this 
difference was not statistically significant (Sekiguchi, 2002).
---------------------------------------------------------------------------

    \6\ Diestrus is a period of sexual inactivity during the estrous 
cycle.
---------------------------------------------------------------------------

    In 1999, the Brominated Solvents Consortium (BSOC), a group of 
several nPB manufacturers, initiated a two-generation study (WIL, 2001) 
designed to investigate thoroughly the reproductive toxicity of nPB, as 
well as to provide additional information on other toxic endpoints of 
concern, including liver effects, and effects on the central nervous 
system (CNS). In this study, groups of 25 male and female rats were 
exposed to nPB via whole-body inhalation. The F0, or first generation, 
animals were exposed to target air concentrations of 0, 100, 250, 500, 
or 750 parts per million (ppm) of nPB for 6 hours/day, 7 days/week for 
at least 70 days prior to mating. The F1, or second generation, animals 
were exposed to 0, 100, 250, or 500 ppm nPB (infertility in the F0 750 
ppm group precluded having an F1 750 ppm group). Exposure of male 
animals in both generations continued throughout mating to the day 
prior to study termination. Exposure for female animals in both 
generations continued throughout mating and gestation through gestation 
day 20. After birth of the pups, the females' exposure continued on 
lactation day 5 through the day prior to study termination.
    In this study, fertility was compromised significantly at 500 ppm, 
and no live offspring were produced at 750 ppm. There was strong 
evidence of dose-response in both the parent (F0) and offspring (F1) 
generations for a constellation of reproductive effects in both males 
and females, including decreases in sperm motility and changes in sperm 
morphology, reduced numbers of implantation sites and changes in 
estrous cycles, and reduced litter size. There were slight decreases 
(only some of which were statistically significant) at 250 ppm, and 
even 100 ppm for some reproductive endpoints. Statistically significant 
effects were observed at 250 ppm for reduced prostate weight in F0 
males and increased estrous cycle length F1 females. Sperm motility in 
the 250 ppm group of F1 males was slightly reduced (84.8%) compared to 
the control group (88.9%). The difference was statistically significant 
(p<0.05). The study authors noted, however, that the sperm motility 
percentage for F1 males was slightly higher than the mean value in the 
WIL Research Laboratories historical control data (83.2%). Therefore, 
the authors did not attribute the reduction in sperm motility to 
exposure to nPB at 250 ppm. Male reproductive effects were consistent 
with those identified in the Japanese studies previously cited 
(Ichihara et al., 1998, 1999, 2000a; Wang, 1999).
    Liver effects similar to those reported in the ClinTrials (1997b) 
90-day inhalation study were observed in males and females in both 
generations. Increases in liver weights occurred in both sexes 
following exposure to 500 ppm; corresponding increases in the incidence 
of minimal to mild hepatocellular vacuolation were observed at 250 ppm 
in males and 500 ppm in females. The adverse effects on the central and 
peripheral nervous system reported by Yu (2001) and Ichihara (1999, 
2000b) occurred at higher doses than those associated with reproductive 
and liver effects in the two-generation study.
    Carcinogenicity/Mutagenicity. Limited in vitro screening assays 
testing for mutagenicity and potential carcinogenicity have been 
conducted on nPB. Two studies have been performed investigating the 
potential mutagenicity of nPB in bacterial strains. Barber et al. 
(1981) exposed five S. typhimurium strains (TA98, TA100, TA1535, TA1537 
and TA1538) to five different vapor concentrations of nPB ranging from 
1.1 to 20.3 [mu]mol/plate (135-2497 [mu]g/plate). Exposures were 
performed in a closed incubation system in the presence and absence of 
liver S9 fraction (from Arochlor-induced rats). Increases in revertants 
were observed in only strains TA100 and TA1535 in both the absence and 
presence of S9; increases were not reported in the other strains. Elf 
Atochem (1994) exposed the same bacterial strains to nPB concentrations 
of 100 to 100,000 [mu]g/plate in both the absence and presence of liver 
S9 (from male Sprague-Dawley rats induced with Arochlor 1254). This 
protocol also used a closed system (closed stainless-steel vessels). 
The highest concentration was slightly cytotoxic; however, this assay 
did test up to the limit dose (5,000 [mu]g/plate) recommended for 
bacterial reversion assays. Appropriate positive and negative controls 
were used to determine spontaneous background revertant frequency. No 
increases in revertants were reported in any strain or condition. Given 
these conflicting studies, the current data regarding mutagenicity of 
nPB in bacterial strains are equivocal. Unpublished studies of in vivo 
micronucleus formation (Elf Atochem 1995a) indicate that nPB is not 
clastogenic, and a published dominant lethal assay with NPB was 
negative (Saito-Suzuki et al. 1982).
    In a cell death bioassay using cultured human liver cells (HepG2 
hepatoma), the cytotoxicity of nPB was evaluated at concentrations 
<=500 ppm (SLR 2001a). Results of the bioassay indicated that nPB was 
cytotoxic (measured as decreased cell viability) at the highest 
concentration tested (500 ppm). There were no positive responses 
reported at any concentration for tests that evaluated enzyme function, 
DNA damage, or DNA damage and repair when tested at concentrations up 
to 500 ppm. A closely related compound, ethyl bromide, is weakly 
carcinogenic in rodents (Haseman and Lockhart 1994), and iPB has been 
shown to induce reverse mutations in bacteria (Maeng and Yu 1997). 
Results from these screening assays for short-term genotoxicity do not 
suggest significant concerns regarding nPB's potential carcinogenicity, 
although more data are needed.
    The National Institute of Environmental Health Sciences' National 
Toxicology Program (NTP) is planning to conduct carcinogenicity studies 
in both sexes of rats and mice, which will allow for more definitive 
conclusions. To date, the NTP has not initiated new experimental 
studies on nPB, and the data will not be available for several years.

[[Page 33292]]

    b. Derivation of an AEL for nPB.
    Benchmark Dose Modeling Background. EPA considered two methods to 
derive a recommended acceptable exposure level for workplace exposure: 
(1) The use of the no-observed-adverse-effect level (NOAEL) to define 
the starting point of departure (POD) for the computation of a 
reference value, and (2) the use of benchmark dose-response (BMD) 
modeling to define the POD. Both methods are essentially a two-step 
process, the first step defining a POD, and then the second 
extrapolating from the POD to a lower, environmentally relevant 
exposure level. EPA's in-depth analysis uses the BMD modeling approach, 
for reasons explained below; however, under either approach, one 
arrives at a similar value.
    The traditional approach to derive safe exposure limits for 
numerous chemicals regulated in a variety of programs, including the 
SNAP program, has been to first determine the NOAEL (or LOAEL if a 
NOAEL cannot be identified), use the NOAEL as the POD, and then apply 
uncertainty factors based on EPA's guidelines to determine an 
appropriate reference value. Using the NOAEL to determine a reference 
value has long been recognized as having limitations in that it: (1) Is 
limited to one of the doses in the study; (2) does not account for 
variability in the estimate of the dose-response, which is due to the 
characteristics of the study design; (3) does not account for the slope 
of the dose-response curve; and (4) cannot be applied when there is no 
NOAEL, except through the application of an additional uncertainty 
factor (Crump, 1984; Kimmel and Gaylor, 1988).
    A newer analytic approach is to use benchmark dose modeling to 
define a point of departure for deriving a reference value or slope 
factor that is more independent of study design. For risk assessment of 
nPB, EPA followed the BMD guidelines to develop an AEL. The EPA Risk 
Assessment Forum has written guidelines for the use of the BMD approach 
in the assessment of non-cancer health risk (USEPA, 1995b), and the EPA 
Benchmark Dose Workgroup is in the process of drafting technical 
guidance for the application of the BMD approach in cancer and non-
cancer dose-response assessments. Use of BMD methods involve fitting 
mathematical models to dose-response data and using the results to 
select a BMD that is associated with a predetermined benchmark response 
(BMR) at the low end of the observed range in the studies used, such as 
a 10% increase in the incidence of a particular lesion or a 10% 
decrease in body weight gain. The BMD derived from mathematical 
modeling is the central estimate of the dose/exposure associated with 
the BMR. The point of departure derived from BMD modeling, however, is 
the Benchmark Dose Lowerbound (BMDL), or the lower 95% bound on the 
dose/exposure associated with the BMR. Using the lower bound accounts 
for the uncertainty inherent in a given study (e.g., small sample 
size), and assures (with 95% statistical confidence) that the desired 
BMR is not exceeded.
    The advantage of the benchmark dose approach is that it considers 
response data across all exposure groups. For example, a benchmark dose 
can be calculated even in studies where a NOAEL could not be 
identified, i.e., in studies where responses even in the lowest 
exposure group tested were considered adverse. Unlike the NOAEL/LOAEL, 
the benchmark dose does not have to be one of the exposure levels (dose 
groups) chosen in the experimental design. In a hypothetical experiment 
where groups of rats are exposed to a chemical at 0 ppm, 100 ppm, 500 
ppm and 1,000 ppm, the NOAEL or LOAEL must be either 100 ppm, 500 ppm, 
or 1,000 ppm simply because those were the only levels tested in the 
experiment. However, the benchmark dose derived from the data in the 
same experiment could be 200 ppm, 750 ppm, or even 997 ppm depending on 
the shape of the dose response curve described by the data. EPA uses 
the BMD approach whenever possible because it provides a more 
quantitative alternative to identification of a point of departure than 
the traditional NOAEL/LOAEL approach (US EPA 1995b).
    Dosimetric adjustments and application of uncertainty factors. 
Under either approach--NOAEL/LOAEL or BMD modeling--an adjustment to 
the point of departure for the calculation of a reference value may be 
necessary to calculate a ``human equivalent concentration'' (HEC) if 
there are differences between the exposure regime used in the toxicity 
studies and a typical workweek of 8 hours per day and 5 days per week. 
Once a POD and the corresponding HEC is identified, uncertainty factors 
(UFs) are applied to account for extrapolation uncertainties that could 
underestimate the chemical's toxicity potential for exposed humans (in 
this case, workers using nPB). According to standard risk assessment 
methods as delineated in Agency guidance (US EPA, 1994), UFs of up to 
10 may be applied 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 (e.g., 
interindividual variability);
    (3) Data from subchronic studies are used to provide estimates for 
chronic exposure;
    (4) Studies that only provide a lowest observed adverse effect 
level (LOAEL) rather than a no observed adverse effect level (NOAEL) or 
benchmark dose; or
    (5) An incomplete data base of toxicity information exists for the 
chemical (US EPA, 1995b).
    Finally, a modifying factor (MF), which is an additional 
uncertainty factor that is greater than zero and less than or equal to 
10, may be used. The magnitude of the MF depends upon the professional 
assessment of scientific uncertainties of the study and data base not 
explicitly treated above, e.g., the completeness of the overall data 
base and the number of species tested. The default value for the MF is 
1.
    It is important to note that EPA does not have specific guidelines 
for occupational studies. As such, EPA is applying its general risk 
assessment principles and adapting its methodologies, as appropriate to 
consider risk in an occupational setting. For example, as mentioned 
above, EPA is adjusting its exposure scenario to derive a human 
equivalent concentration (HEC) that is representative of workplace 
exposure, rather than continuous lifetime exposure.
    Selection of Endpoints for Benchmark Dose Modeling. Based on EPA 
guidance, endpoints were selected for BMD analysis and for potential 
use as a point of departure using the following principles:
    [sbull] Toxicological significance of the endpoint
    [sbull] Relevance to humans
    [sbull] Quality of study and dose-response data
    [sbull] Reproducibility of effects across multiple studies.
    EPA selected reduced sperm motility and increased liver vacuolation 
for BMD analysis because they met the above criteria, and because these 
effects were seen consistently throughout the toxicological database at 
low exposures. EPA guidance states that endpoints selected as 
appropriate for risk assessment should be modeled if their LOAEL is up 
to 10-fold above the lowest LOAEL. This ensures that no endpoints with 
the potential to have the lowest BMDL are excluded from the analysis. 
The selection of the most appropriate

[[Page 33293]]

BMDs to use for determining the point of departure must be made by the 
risk assessor using scientific judgement and principles of risk 
assessment, as well as the results of the modeling process.
    Toxicological Evaluation for AEL Derivation. Benchmark dose 
modeling was conducted following EPA guidelines. EPA modeled six data 
sets for liver vacuolation and reduced sperm motility based on results 
from two studies to identify the lowest BMDL as a point of departure 
(POD).\7\ EPA selected these endpoints for BMD analysis because they 
were consistently found to be the most sensitive effect across the many 
studies that were conducted on the compound. Further, these particular 
studies provided robust data on these endpoints so that BMD analysis 
could be conducted. Based on this analysis, sperm motility in the F1 
males from the WIL (2001) study was selected as the POD as it would be 
protective for all effects of nPB. SLR conducted a BMD analysis using 
data sets for numerous endpoints from 5 studies, including the WIL 
(2000) and ClinTrials (1997b) studies used by EPA (SLR International 
Corp., 2001b).\8\ SLR also identified sperm motility in F1 males from 
the WIL (2001) study as the lowest BMDL. The SLR BMD analysis is 
discussed further in section IV.A.1.d. The methods used in development 
of the AEL based on sperm motility are described below. It is important 
to note that the animals in the 2-generation study were dosed every day 
for six hours. As such, the dosing scenario used for the testing 
procedure does not exactly mirror the human exposure scenario in the 
workplace of 8 hours per day 5 days per week. However, it is still 
appropriate to consider the data because they address the most 
sensitive health endpoints, and because the BMDL is adjusted by 
deriving a HEC to account for workplace exposures. A more complete 
discussion of EPA's adjustment of the BMDL is contained in ICF, 2002a.
---------------------------------------------------------------------------

    \7\ Data sets that were modeled from the WIL study include sperm 
motility and liver vacuolation in the F0 and F1 generations. Data 
sets modeled from ClinTrials (1997b) were liver vacuolation in both 
males and females.
    \8\ SLR International Corp. (2001b) conducted BMD modeling on 
the following studies: ClinTrials (1997a), ClinTrials (1997b), 
Ichihara, et al. (2000a and b), and WIL (2001). Reproductive 
endpoints modeled included sperm count, retained sperm in 
seminiferous tubules, sperm deformities, sperm motility, epididymal 
sperm count, fertility index, litter viability, and plasma glucose 
levels. Other toxicological endpoints modeled included forelimb 
strength, hind limb strength, motor conduction velocity, distal 
latency time, plasma creatinine phosphokinase levels, brain cell 
vacuolation, liver vacuolation in males, and analysis in various 
parameters associated with effects on blood formation.
---------------------------------------------------------------------------

    EPA did not use neurotoxic effects as endpoints for deriving an AEL 
value since we did not consider this to be one of the most sensitive 
endpoints. No neurotoxic effects were reported in the 2-generation 
reproductive toxicity assay (WIL, 2001), and no adverse effects were 
observed in the functional observational battery analysis, either in an 
abbreviated form in the 28-day study at exposure concentrations of 400 
and 1,000 ppm (ClinTrials, 1997a), nor in the 90-day study at 
concentrations of 400 and 600 ppm (ClinTrials, 1997b). Although the 
NIOSH voluntary medical survey performed in 1999 attempted to assess 
symptoms of neurotoxic effects, no exposure-response trend for headache 
or other neurological effects could be identified from the data.
    The vacuolation of the white brain matter that was observed in the 
28-day study at all exposure concentrations was not observed in the 90-
day study, indicating that this effect may be a transient response and 
not adverse. Further, the vacuolation was not dose-dependent and did 
not correlate with other gross CNS effects observed at 1,600 ppm in the 
28-day study. In the 2-generation study, clinical signs were monitored 
and CNS effects were not observed at any exposure concentration (0, 
100, 250, 500, and 750 ppm) in the F0 or F1 animals, nor were 
histopathologic lesions observed in the brain, spinal cord or 
peripheral (sciatic) nerve of rats in the 750-ppm group of the F0 
generation in the 2-generation study or in the F1 population.
    EPA's Benchmark Dose Software (BMDS) was used for model fitting and 
BMD and BMDL estimation. To derive a BMD and BMDL for reduced sperm 
motility in the F0 and F1 males from WIL (2001), the data were modeled 
as continuous effects. Following EPA's Benchmark Dose guidelines, BMDs 
and BMDLs were defined based on benchmark responses (BMRs) of 10% extra 
risk--that is, the level at which 10% of the animals would show adverse 
effects for a particular endpoint. BMDLs were defined as the 95% lower 
confidence bound on the corresponding BMD estimates. Confidence bounds 
were calculated by BMDS using a likelihood profile method. The data 
sets for the reduced sperm motility endpoint were quantitatively 
summarized by group means and measures of variability (standard errors 
or standard deviations). The models used to represent the dose-response 
behavior of these continuous endpoints are those implemented in EPA's 
Benchmark Dose Software which are the Power model, the Hill model, and 
the polynomial model. Goodness-of-fit for each model for a given data 
set was determined based on a likelihood ratio statistic. In 
particular, maximized log-likelihoods associated with the modeling were 
sequentially compared.
    Based on the criteria below, the most appropriate mathematical 
model and its corresponding BMDL was chosen as the best fit for each of 
the data sets modeled:
    1. Models with an unacceptable fit (including consideration of 
local fit in the low-dose region) were excluded. Visual fit, 
particularly in the low-dose region, was assessed for models that had 
acceptable global goodness-of-fit.
    2. If the BMDL values for the remaining models for a given endpoint 
were within a factor of 3, no model dependence was assumed, and the 
models were considered indistinguishable in the context of the 
precision of the methods. The models were then ranked according to the 
Akaike Information Criterion (AIC), which is reported by the BMDS 
software to aid in comparing the fit of different models. The model 
with the lowest AIC (within the family of models) was chosen as the 
basis for the BMDL.
    3. If the BMDL values were not within a factor of 3, some model 
dependence was assumed, and the lowest BMDL was selected as a 
reasonable conservative estimate, unless it was an outlier compared to 
the results from all of the other models. Note that when outliers are 
removed, the remaining BMDLs may then be within a factor of 3, and so 
the criteria given in item 2 would be applied.
    BMDs for reduced sperm motility in F1 and F0 males were 276 ppm and 
362 ppm respectively, and BMDLs were 169 ppm and 282 ppm. Consistent 
with EPA risk assessment guidance, the BMDL of 169 ppm for reduced 
sperm motility in F1 males (WIL, 2001) was selected as the POD. EPA 
considered whether a BMDL derived from the F1 generation should be used 
to determine a workplace exposure limit, particularly in relation to 
the potential mechanisms by which nPB exerts its effects on the 
reproductive system. While some mechanistic data are available on this 
subject, they are inconclusive and limited. The available data do not 
rule out the possibility that the effects on the F1 generation occurred 
as a result of effects on parental germ cells (sperm or ova) or effects 
mediated by changes to the endocrine system. Because of the lack of 
mechanistic data on developmental and potential transgenerational 
effects, it is most appropriate and protective, as well as consistent 
with EPA risk assessment

[[Page 33294]]

guidelines, to use the endpoint observed at the lowest effect level to 
derive the AEL. In this case, that endpoint is decreased sperm motility 
in the F1 generation.
    The BMDL was multiplied by 6/8 and 7/5 in order to derive the HEC, 
which accounts for temporal differences between the exposure duration 
used in the study (6 hours per day, 7 days per week) and an 8-hour per 
day, 5-day work week. This results in a HEC for spermatic effects of 
177 ppm. Uncertainty factors were then applied to the HEC, taking into 
account the following considerations listed below.
    (1) An uncertainty factor is needed to account for physiological 
differences between humans and rats. EPA reference concentration (RfC) 
guidelines describe the factors that must be considered and state that 
an uncertainty factor 10 may be used for potential differences between 
study animals and humans. This factor of 10 is often thought to consist 
of two uncertainty factors of 3--the first to account for differences 
in pharmacokinetics \9\ and another uncertainty factor to account for 
differences in pharmacodynamics \10\ between the study animal and 
humans. (The value of 3 is the closest whole number to the square root 
of 10.) According to EPA RfC guidelines, no adjustment for differences 
in pharmacokinetics is necessary in this case since the blood/air 
partition coefficient \11\ 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.
---------------------------------------------------------------------------

    \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\ Pharmacodynamics refers to the biochemical and 
physiological effects of chemicals in the body and the mechanisms of 
their actions.
    \11\ A ratio of a chemical's concentration between blood and air 
when at equilibrium.
---------------------------------------------------------------------------

    However, EPA recognizes that the lack of an uncertainty adjustment 
for pharmacokinetic differences between animals and humans rests on a 
default approach applied to category 3 gases described in Appendix J of 
its guidelines for deriving an inhalation RfC. This default approach 
assumes that the pharmacokinetics of nPB conform to a model that 
requires several assumptions, in particular: (1) The toxicity is 
directly related to the inhaled parent compound in the arterial blood, 
and (2) the critical metabolic pathways scale across species, with 
respect to body weight, in the same way as the ventilation rate (e.g., 
BW\3/4\). Given the hypothesized metabolic pathways for nPB 
(ICF, 2002a; CERHR, 2002a), it is plausible that toxicity in rats may 
be related to a reactive metabolite in the target tissue rather than 
the blood level of the parent compound. EPA is not aware of any 
quantitative data on nPB metabolism in humans, or evidence implicating 
the biologically active agent or mode of action. EPA requests 
additional data and comment from the public on nPB pharmacokinetics, 
metabolism, and mode of action that will help determine whether an 
interspecies uncertainty factor greater than 1 is appropriate to 
account for pharmacokinetics. If data become available indicating that 
nPB does not conform to the constraints assumed by the default 
pharmacokinetic model in the RfC guidelines, EPA would refine its risk 
assessment for nPB as necessary, and apply an uncertainty factor for 
pharmacokinetics in extrapolating from animal to humans. We would also 
revise our acceptability determinations accordingly.
    With regard to the UF for pharmacodynamics, no data exist to 
compare the effect of nPB on human spermatocytes and rat spermatocytes. 
EPA does not have data suggesting that the default of 3 for 
pharmacodynamics should not be used. Thus, the full uncertainty factor 
of 3 for differences in pharmacodynamics was applied. EPA also requests 
comments and data on this uncertainty factor.
    (2) Although workers employed in the types of industrial sectors 
that are part of this SNAP review likely represent a generally healthy 
population, pre-existing reproductive conditions as well as general 
variability in fertility would not impact a worker's overt health or 
employment status, and would be largely unobserved. It is estimated 
that 6% of adult males are infertile (Purves, 1992), and that 40%-90% 
of these cases are due to deficient sperm production of unidentifiable 
origin (Griffin, 1994). Given this information, EPA concludes that a 
significant portion of the male population has pre-existing 
reproductive deficits. EPA's risk guidelines for deriving community-
based reference concentrations recommend a factor of 10 in accounting 
for intraspecies variability. EPA believes that in the case of nPB, a 
lower uncertainty factor is appropriate to account for variability 
within the worker population. This UF is intended to protect for 
potential ``unobserved'' reproductive medical conditions (e.g., 
decreased sperm motility, aberrant sperm formation) that are known to 
exist among otherwise healthy males of working age. Because we are 
concerned about exposures in the workplace, not exposures to the full 
population, and because exposures would not be continuous, such as 
would be expected when developing an RfC, we employed an UF of three as 
an upper bound instead of the full uncertainty factor of 10 for 
intrahuman variability.
    The following equation describes how EPA derives 18 ppm as a 
starting point in the development of a recommended AEL using a UF of 3 
for variations in the human population, and 3 for pharmacodynamics:

169 ppm * \6/8\ * \7/5\ * \1/3\ * \1/3\) = 18 ppm

    This derivation rests on assumptions that some may consider 
conservative, including the use of the F1 generation as the point of 
departure for workplace exposure, and the fact that reduced sperm 
motility may be a particularly sensitive endpoint for male reproductive 
effects. For a further discussion, see the next section below, ``AEL 
adjustment based on risk management principles.''
    AEL adjustment based on risk management principles. Risk management 
uses risk characterization, along with directives of the enabling 
regulatory legislation and other factors, to decide whether to control 
exposure to the suspected agent and the level of control. Risk 
management decisions also consider socioeconomic, technical, and 
political factors (EPA Reproductive Risk Assessment Guidelines, 1996). 
Unlike many other chemicals being reviewed by SNAP, nPB is already in 
use. Therefore, a decision on the AEL that incorporates risk management 
considerations may be appropriate. Doing so is consistent with one of 
the original ``Guiding Principles'' of the SNAP program (59 FR 13046, 
March 18, 1994):

    EPA does not intend to restrict a substitute if it poses only 
marginally greater risk than another substitute. Drawing fine 
distinctions concerning the acceptability of substitutes would be 
extremely difficult given the variability in how each substitute can 
be used within a specific application and the resulting 
uncertainties surrounding potential health and environmental 
effects. The Agency also does not want to intercede in the market's 
choice of available substitutes, unless a substitute has been 
proposed or is being used that is clearly more harmful to human 
health and the environment than other alternatives.

    If EPA adopted 18 ppm as the AEL, we would likely propose that use 
of nPB be listed as unacceptable in adhesives applications, based on 
data indicating that exposure to nPB in such uses regularly exceed 18 
ppm on average. However, EPA has determined that adhesive operations 
can meet an AEL of 25 ppm with proper ventilation and

[[Page 33295]]

controls (see Section IV.A.1.e., ``Feasibility of meeting the AEL for 
nPB in each industrial sector''). The AEL of 18 ppm was derived using 
assumptions that some may consider conservative. Following the SNAP 
principle referenced above, some slight adjustment of the AEL may be 
warranted after applying judgment based on the available data, and 
after considering alternative derivations.
    To assess how much of an adjustment may be appropriate that would 
still be protective of human health, EPA considered potential sources 
of conservatism in the AEL derivation--specifically, the use of the 
BMDL in the F1 generation as a point of departure. To assess the 
magnitude of this conservatism, we derived an AEL based on the BMDL for 
reduced sperm motility in the F0 generation (282 ppm), the second most 
sensitive endpoint found in the 2-generation study. Deriving an HEC 
(296 ppm), and applying the same uncertainty factors as applied to the 
F1 generation (3 for intraspecies variability and 3 for differences in 
pharmacodynamics), would result in an occupational exposure limit of 
approximately 30 ppm. A derivation based on F0 data could be considered 
as a reasonable and protective upper bound for the occupational 
exposure limit. EPA requests comment on whether it appropriate to 
interpret 30 ppm as an upper bound for an occupational exposure limit.
    EPA has determined 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 exposure limit. An AEL of 25 ppm would reduce overall 
risk to worker health while adhering to EPA's SNAP guiding principle of 
not finding a substitute unacceptable unless the proposed substitute is 
clearly more harmful than other alternatives. EPA specifically requests 
comment on this approach.
    Dermal Exposure. EPA believes that workers should use good 
workplace practices and proper handling procedures to avoid unnecessary 
dermal exposure to all industrial solvents, including nPB. Similar to 
other halogenated solvents, nPB may defat the skin and may cause local 
irritation due to this characteristic. A skin notation is applied to 
those chemicals where ``dermal absorption contributes substantially to 
the overall systemic toxicity'' (skin notation documentation for methyl 
chloride; ACGIH, 1991). As described previously, the available acute 
dermal toxicity study in rats (Elf Atochem, 1995) indicates that acute 
dermal exposure to nPB does not result in systemic toxicity. Because 
significant dermal absorption of nPB was not demonstrated in this 
study, EPA is not including a skin notation for nPB along with our 
recommended AEL in the comments section of the regulatory text. The 
database regarding dermal toxicity for nPB is not as conclusive as the 
data for chemicals that have a skin notation, (e.g., methyl chloride, 
dichlorvos). To apply a skin notation to nPB would imply that the 
dermal toxicity of this compound is similar to that of these other 
compounds. It is also noteworthy that there is no skin notation for 
other halogenated solvents such as methylene chloride or 
perchloroethylene, and there is no evidence that absorption through the 
skin is greater for nPB than for the other halogenated compounds. Thus, 
in EPA's judgement the database currently does not support the need for 
a skin notation for nPB.
    However, we note that the acute dermal study did not provide 
information regarding chronic dermal absorption. Further, NIOSH 
evaluated the potential of nPB to permeate skin and promote chronic, 
systemic toxicity using a mathematical model and the log octanol::water 
coefficient for nPB, which is approximately 2. This evaluation found 
that nPB dermal exposure may be an additional source of exposure to 
workers if the unprotected skin of both hands is exposed (NIOSH, 2003). 
Given the above information, EPA specifically requests comment on 
whether to add a skin notation to our recommended AEL in the final rule 
if there are data that support this change.
    c. Overview of the Evaluation of Risks to Human Reproduction 
(CERHR) Expert Panel Report on nPB. In December 1999, NIOSH submitted 
an assessment nomination to the National Toxicology Program's (NTP) 
Center for the Evaluation of Risks to Human Reproduction (CERHR) for 
both nPB and iPB. The NTP and the National Institute of Environmental 
Health Sciences (NIEHS) established CERHR in June 1998. CERHR's purpose 
is to provide timely, unbiased, scientifically sound evaluations of 
human and experimental evidence for adverse effects on reproduction, 
including development, caused by agents to which humans may be exposed.
    nPB (1-Bromopropane) was nominated by NIOSH and selected for 
evaluation by the CERHR based primarily on documented evidence of 
worker exposures and published evidence of reproductive and 
developmental toxicity in rodents (this evidence is reviewed above in 
section IV.A.1.a). The evaluation of nPB was a four-month effort by a 
ten-member Expert Panel of academic, private and government scientists 
that culminated in a public meeting in December 2001. At that meeting, 
the Expert Panel reviewed the scientific evidence on nPB and reached 
conclusions regarding its potential effects on human reproduction and 
development. The Expert Panel Report on nPB was issued in March 2002 
(CERHR, 2002a). An Expert Panel Report on iPB was issued at the same 
time and is discussed in section IV.A.4. of this preamble (CERHR, 
2002b).
    The Expert Panel Report on nPB is intended to: (1) Interpret the 
strength of scientific evidence that a given exposure or exposure 
circumstance may pose a hazard to reproduction and the health and 
welfare of children; (2) provide objective and scientifically thorough 
assessments of the scientific evidence that adverse reproductive/
developmental health effects are associated with exposure to specific 
chemicals or classes of chemicals, including descriptions of any 
uncertainties that would diminish confidence in assessment of risks; 
and (3) identify knowledge gaps to help establish research and testing 
priorities.
    NTP-CERHR sought public comment on the Expert Panel Report through 
a Federal Register notice on March 8, 2002 (67 FR 10734). The NTP has 
issued a final report, and has published all the public comments that 
were received on that report. These documents may be accessed through 
the CERHR Web site at http://cerhr.niehs.nih.gov/news/bromo/index.html.
    The conclusions of the March 2002 Expert Panel Report on nPB were 
as follows:
    [sbull] Available human data are insufficient to draw conclusions 
on the potential for reproductive or developmental toxicity.
    [sbull] Available toxicological data were sufficient to conclude 
that nPB exposure can induce developmental and reproductive toxicity in 
rats. In evaluating the potential effects on human reproduction, the 
rat data are assumed to be relevant for humans.
    [sbull] The mechanisms that lead to reproductive or developmental 
toxicity are unknown.
    [sbull] There are no relevant kinetic or metabolism data for nPB to 
compare human and animal exposure levels.
    The Expert Panel identified LOAELs from the body of animal data as 
follows:
    [sbull] A LOAEL for male reproductive effects of 200 ppm based on 
decreases in absolute and relative seminal vesicle weight reported in 
Ichihara (2000b). A

[[Page 33296]]

NOAEL of 100 ppm was identified based on decreases in prostate weight 
observed at 250 ppm in WIL (2001).
    [sbull] A LOAEL of 250 ppm, and a NOAEL of 100 ppm for female 
reproduction based on increased estrous cycle length in WIL (2001).
    [sbull] A LOAEL of 250 ppm and a NOAEL of 100 ppm for 
mineralization of the kidney pelvis in both F0 and F1 generations, 
based on WIL (2001).
    EPA agrees with the panel's conclusions that the available human 
data are insufficient to draw conclusions on the reproductive or 
developmental toxicity of nPB and that the mechanisms that lead to 
reproductive or developmental toxicity are unknown. EPA also agrees 
with the panel that a NOAEL for reproductive effects (male) would be 
considered to be 100 ppm under a traditional risk assessment analysis. 
However, based on the criteria described previously for selecting 
endpoints for BMDL analysis, we believe the CERHR endpoints are not 
appropriate for developing the AEL for nPB, as explained below.
    Reduced seminal vesicle weight. EPA did not conduct BMD analysis 
for reduced seminal vesicle weight observed in the Ichihara (2000b) 
study because there is no consistency of effect across available 
studies for this endpoint. Reduced seminal vesicle weight was not found 
to be a sensitive endpoint in WIL (2001). In fact, a statistically 
significant reduction in seminal vesicle weight was only seen in the 
750 ppm group in the F0 generation, and there were no statistically 
significant effects on seminal vesicle weight in the F1 generation. 
Because there were other endpoints that were more sensitive in the WIL 
study, we regard those endpoints to be of greater toxicological 
importance. Further, EPA believes that because the Ichihara study was 
not performed according to GLP guidelines, and there were conflicting 
reports regarding the exposure regime and the number of animals used, 
it is not appropriate to use this study in quantitative risk 
assessment.
    Reduced absolute prostate weight. Based on the WIL study, the CERHR 
Expert Panel identified a NOAEL of 100 (with a LOAEL of 250) for 
reduced absolute prostate weight in the F0 males. The toxicological 
relevance of absolute prostate weight reduction is questionable since 
this endpoint may be associated with reduction in overall weight gain. 
To assess the significance of this particular endpoint, EPA calculated 
the mean relative prostate weights for exposed dose groups from the WIL 
(2001) study. Relative prostate weights (organ weight/body weight) in 
F0 males were 0.0040, 0.0039, 0.0036, 0.0035, and 0.0035 at 0, 100, 
250, 500, and 750 ppm respectively, revealing that relative prostate 
weight at exposures greater than or equal to 250 ppm decreased only 10% 
relative to controls. Because the dose-response relationship in other 
endpoints was more pronounced, EPA did not conduct BMD modeling on this 
endpoint.
    Increased estrous cycle length. The Expert Panel identified 250 ppm 
as a LOAEL for females based on increased estrous cycle length in the 
F1 generation of the WIL (2001) study. EPA agrees that the slight 
increase in estrous cycle length may be a result of nPB exposure. 
However, because the estrous cycle length of 4.9 days at 250 ppm is 
within the range of historical controls, the effect cannot be 
conclusively attributed to exposure without statistical analysis. The 
study report also notes lack of cycling in some females, which may have 
caused difficulty in accurately determining the average estrous cycle 
length for each affected group. Because these data are lacking, this 
endpoint should not be used for developing the AEL.
    Mineralization of the kidney pelvis. The Expert Panel concluded 
that mineralization of the pelvis of the kidneys at 250 ppm was an 
adverse effect. EPA notes that mineralization of the kidney was not 
consistently associated with nPB exposure across different studies, and 
that in WIL (2001) the severity of mineralization did not increase 
above a category of minimal except at 750 ppm where it was mild. 
Therefore, EPA did not consider using this endpoint as useful for 
developing the AEL.
    Sperm Motility. The Expert Panel identified 500 ppm as the LOAEL 
for reduced sperm motility. The Panel agreed with the WIL (2001) study 
authors that the slight but statistically significant reduction in the 
percentage of motile sperm in the F1 males at 250 ppm (85% vs. 89% in 
concurrent control animals) could not be attributed to nPB exposure 
since the percentage of motile sperm in this dose group slightly 
exceeded that of historic controls (83%). The data indicate that the 
small changes observed at 250 ppm are consistent with larger changes in 
sperm motility observed at 500 and 750 ppm. Thus, results for sperm 
motility in F0 and F1 males exhibited dose-related trends, and 
conformed to other principles for the selection of endpoints for BMD 
analysis (See earlier discussion in section IV.A.1.b.). Thus, 
regardless of whether a LOAEL of 500 ppm or 250 ppm is assigned to this 
particular endpoint, the Agency determined that reduction in the 
percentage of motile sperm in the F1 males is a good candidate for BMD 
analysis. In addition, it is important to note that the Panel did not 
have access to either the ICF or SLR International benchmark dose 
analyses. As discussed in section IV.A.1.b, benchmark dose modeling 
overcomes the issue of drawing a ``bright line'' in the form of a LOAEL 
or NOAEL and instead uses the full set of data across all exposure 
levels (ICF, Inc., 2002a; SLR International, 2001b). Using the results 
of benchmark dose modeling, it becomes clear that sperm motility is a 
sensitive effect, and is an appropriate effect upon which to base an 
AEL.
    d. AELs suggested by other reviewers and outside parties. In the 
draft final nPB risk screen conducted for EPA in preparation for 
today's proposal, ICF Consulting states that ``Given the strength of 
the data base and the extrapolation of the data to occupational 
exposures, a range of uncertainty factors to account for variability in 
the human population of 2 to 3 is considered appropriate.'' (ICF, 
2002a). EPA recognizes that the choice of UF relates to a wide range of 
considerations including the strength of the data base. Applying a 
range of UFs between 2 and 3 to account for intrahuman variability 
would yield a range of occupational exposure limits between 18 and 30 
ppm. ICF suggested that the midpoint of this range, 25 ppm, was an 
appropriate occupational limit value for the purposes of the risk 
screen for nPB. EPA requests comment on this recommended approach in 
deriving an occupational exposure limit, including the application of 
uncertainty factors.
    EPA's Office of Atmospheric Programs solicited comments regarding 
ICF Consulting's analysis and derivation of a recommended AEL from 
EPA's Office of Research and Development (ORD), external toxicologist 
William Brock, external toxicologist Darol Dodd, and the State of 
California, Department of Health Services, Hazard Evaluation System & 
Information Service (HESIS). The comments are available in docket A-
2001-07.
    ORD's comments focused on the WIL Research Laboratories two-
generation study and its use in identifying sensitive endpoints. ORD 
noted that the study's results indicated dose-related trends, that a 
number of endpoints were significantly affected at 500 ppm in both 
generations, and there were slight--though in most cases not 
statistically significant--decreases at 250 ppm and even 100 ppm for 
some endpoints. They also stated that ``[i]n the absence of evidence of 
dominant lethality or trans-generational effects typical of endocrine

[[Page 33297]]

disrupting chemicals, it is reasonable to conclude that the effects of 
[nPB] are elicited in both sexes via their exposure as adults.'' They 
also noted that ``the modest degree of change in the 250 ppm F1 sperm 
motility endpoint (and lack of significance in the F0 at this dose) 
compared to the collective more robust changes at 500 ppm, in both the 
F0 and F1, indicates that 250 ppm could reasonably be considered a 
NOAEL for nPB, with 500 ppm being a LOAEL.'' Finally, ORD noted that 
``even if the F1 data may not be directly applicable for occupational 
exposures in males, it certainly is applicable to occupational 
exposures of pregnant women.'' They conclude with suggestions for 
further research (Klinefelter and Darney, 2002).
    EPA asked William Brock to review the draft AEL report from a 
general toxicological point of view. Dr. Brock is currently a senior 
manager with Environ Corporation. In his review, Dr. Brock noted that 
several subchronic studies in rats have been conducted with nPB with 
concentrations ranging from approximately 100 ppm to 1800 ppm. 
Biological effects have been on liver, male reproductive tissue, and, 
to some extent, hematological parameters. Although some of the studies 
have not been conducted according to GLP, this fact does not 
necessarily limit the usefulness of the studies to recommend an 
exposure limit. Overall, the sperm effect observed at 400 ppm and the 
effects on fertility at 500 ppm with hepatic vacuolation at 250 
represent the PODs for setting exposure limits for nPB. The NOAEL for 
these effects would be 200 ppm. Dr. Brock notes that ``exposure limits 
that have historically been established are generally, but no[t] 
always, an order of magnitude below the NOAEL. Taking this approach 
would result in an occupational limit of 20 ppm (200/10). Although the 
ICF report could be improved by being more specific on effects and 
concentrations, the logic provided in the report and the end result, 
i.e., a 25 ppm exposure limit, is certainly justified'' (Brock, 2002).
    EPA asked Darol Dodd to review and comment on the draft AEL report 
(ICF, 2000a). Dr. Dodd is currently the Laboratory Director for ManTech 
Environmental Technology, Inc. In his comments, Dr. Dodd stated that 
the ICF report provided logical and consistent explanations for 
selection of the BMDL and uncertainty factors. He noted that several of 
the studies show LOAEL or NOAEL values at 200 ppm to 250 ppm. In his 
opinion, ``a recommended AEL value that is about one order of magnitude 
lower than LOAELs/NOAELs in a number of laboratory rodent studies does 
not appear to be overly protective'' (Dodd, 2002).
    HESIS provided comments on the AEL derivation for nPB that focused 
on the available studies useful for low-dose risk assessment, 
identifying the LOAELs and NOAELs from these studies, and identifying 
their disagreements with the ICF evaluation. Overall, HESIS took issue 
with the approach used by ICF to derive an AEL: ``ICF repeatedly 
ignores or discounts effects seen with low-level exposures. At most 
points where a decision based on professional judgment must be made, 
ICF makes the choice that leads to the highest possible AEL.'' HESIS 
states that, contrary to the ICF approach, an appropriate risk 
assessment methodology would take a NOAEL, LOAEL or appropriate BMDL, 
and apply uncertainty factors of 10 for each of the following 
conditions: (1) Interspecies variation, (2) intraspecies variation, (3) 
reliance on a LOAEL rather than a NOAEL where necessary, and (4) 
extrapolation from acute or subchronic exposure to chronic exposure. 
The total uncertainty factor would be between 1,000 and 10,000. HESIS 
stated that appropriate endpoints and points of departure would be 
reduced pup weight seen in the Huntingdon (2001) study at 103 ppm, the 
neurotoxicity seen in Ichihara (2000a) at 200 ppm, reduced seminal 
vesicle weight and increase in tailless sperm seen at 200 ppm in 
Ichihara (2001a), reduced sperm motility at 200 ppm in Wang (1999), CNS 
pathology (vacuolation of white matter) at 400 ppm seen in ClinTrials 
(1997a), and from the WIL (2001) study, reduced fertility observed at 
100 ppm and other adverse reproductive and kidney effects observed at 
250 ppm or the lowest BMDL calculated from all studies. Using any of 
these points of departure, HESIS suggests that a reasonable AEL could 
range from less than 0.05 ppm to less than 5 ppm, and recommends an AEL 
of 1 ppm.
    HESIS stated that, in deriving the AEL for the liver vacuolation, 
ICF used no uncertainty factor for interspecies pharmacokinetic 
variation, assuming ``without any basis, that gas exchange within the 
lung constitutes the entire pharmacokinetic variation between the 
species, simply because the blood-air partition coefficient is lower in 
humans than in rats.'' HESIS also disagreed with the use of no 
uncertainty factor for intraspecies variation for liver vacuolation. 
With regard to ICF's derivation of an AEL for sperm motility, HESIS 
disagreed with ICF's use of no uncertainty factor for interspecies 
pharmacokinetic variation for the same reason given for liver 
vacuolation. HESIS also stated that there ``is no data base at all on 
which to determine the likelihood and degree of interhuman variability 
in sensitivity to the spermatotoxic effect of [nPB] * * * .'' Finally, 
HESIS stated that nPB ``is an organic solvent that is probably well 
absorbed through the skin and should be listed with a skin notation * * 
* .''
    A response from ICF Consultants to HESIS's comments is included in 
the docket (ICF 2002c). EPA concluded that the issues HESIS raises are, 
in fact, questioning EPA's risk assessment guidelines that were the 
basis for the AEL report, rather than comments unique to the AEL for 
nPB. For example, EPA's risk assessment guidelines allow use of a 
default uncertainty factor of 1 instead of 3 for pharmacokinetics for 
nPB and other inhaled gases where the toxicity is from the parent 
compound, rather than metabolites. As discussed above in section 
IV.A.1.b, we request comment and data that would confirm or refute the 
appropriateness of the assumptions in Appendix J of EPA's risk 
assessment guidelines. In addition, EPA disagrees that the uncertainty 
factor for variability in the worker population should be the same as 
that for variability in the general population (10). Because the 
working population does not include children or the elderly, as is the 
case for the general population, we do not believe that a full UF of 10 
for sensitive subpopulations is necessary. Further, workers are only 
potentially exposed during a 40-hour workweek and not continuously, as 
would be expected for the general population. Finally, because of the 
length of the WIL Laboratories study, we do not believe that it is 
necessary to add an uncertainty factor to extrapolate from subchronic 
to chronic exposures.
    Various chemical manufacturers and solvent formulators have derived 
their own recommended industrial exposure limits. Albemarle Corporation 
and Dead Sea Bromine Group, both of whom continue to produce nPB, 
recommend an AEL of 25 ppm in their Material Data Safety Sheets. Great 
Lakes Chemical and Atofina recommended AELs of 10 ppm and 5 ppm 
respectively, although neither of these companies currently sells nPB. 
Petroferm produces nPB formulations and recommends an exposure limit of 
25 ppm. Finally, Enviro Tech International, Poly Systems International, 
TULSTAR Products, and Amity International, all of whom produce nPB 
formulations, recommend an exposure limit of 100 ppm.
    In a November 6, 2000, meeting with EPA, Albemarle explained that 
its derivation of a workplace exposure guideline of 25 ppm is based 
upon raw

[[Page 33298]]

data from the two-generation reproductive study (WIL, 2001). In the 
fall of 2000, Albemarle analyzed preliminary data from the two highest 
exposure groups in two-generation study, 750 ppm and 500 ppm, and found 
evidence of reproductive effects. As a proactive measure while 
completing analysis of the data, Albemarle started with an exposure 
level of 250 ppm and divided by a safety factor of 10, yielding an 
exposure guideline of 25 ppm. EPA has not seen the derivation of Great 
Lakes Chemical Corporation's workplace exposure guideline of 10 ppm or 
Atofina's guideline of 5 ppm.
    The AEL recommended by Enviro Tech International is based on two 
separate analyses. In the first analysis, Rozman and Doull (2001) 
recommend an AEL of 60-90 ppm based on the results obtained from a 
health questionnaire administered as a part of a NIOSH Health Hazard 
Evaluation at a site where nPB is used as an adhesive (NIOSH, 1999). 
This AEL derivation was subsequently published in Applied Occupational 
Environmental Hygiene, the ACGIH's journal, in 2002 (Rozman and Doull, 
2002).
    In their analysis, Rozman and Doull identified the most sensitive 
endpoint for nPB toxicity as peripheral/central neurotoxicity followed 
by reproductive toxicity and then liver toxicity. This ranking was 
based on a subchronic inhalation study by Ichihara (2000b) in which 
decreased hind limb strength in mice was observed following 4 weeks of 
exposure at 200 ppm. Rozman and Doull concluded that rats are more 
sensitive to reproductive effects of nPB than humans based on the NIOSH 
health survey (NIOSH 2002b), which did not identify any statistically 
significant reproductive effects in humans exposed to nPB. Based on the 
NIOSH health survey data, conducted at a facility where nPB was used as 
an adhesive solvent, Rozman and Doull identified 170 ppm as a no 
observed effect level (NOEL) in workers who reported having a headache 
more than once per week. They then applied a safety of 2 to protect 
nearly all workers, and a safety factor of 3 to provide a larger margin 
of safety from this adverse effect. This approach resulted in a 
recommended industrial exposure guideline for nPB of 60-90 ppm.
    EPA does not agree with Rozman and Doull's AEL recommendation. 
First, their ranking of neurotoxicity as the most sensitive 
toxicological endpoint fails to take into account that in the Ichihara 
study, rats were dosed 8 hours per day for 12 weeks, while in the two-
generation study, animals were exposed to nPB for 6 hours per day. 
Therefore, the exposure levels in the Ichihara study must be adjusted 
by a factor of 0.75 in order to directly compare doses to the 2 
generation study. If this adjustment is made, the LOAEL for the 
Ichihara study becomes 266 ppm, higher than the LOAEL of 250 ppm for 
reproductive and liver effects identified in the two-generation study. 
Further, the results of the Ichihara study conflict with the results of 
the 90-day inhalation study (ClinTrials, 1997b), in which decreases in 
grip strength were not observed in rats exposed to levels up to 600 ppm 
nPB for 6 hours/day for 5 days/week. In fact, in the ClinTrials study, 
there were no consistent treatment-related changes reported in the rats 
following 4, 8, or 13 weeks of exposure in any parameter evaluated in a 
full functional observational battery (a suite of tests designed to 
assess a full spectrum of neurotoxic effects). Because the LOAEL for 
neurotoxic effects in Ichihara et al. (2000b) is actually higher than 
the LOAEL identified in the two-generation study, and because the 
findings on neurotoxicity from the Ichihara study conflict with the 
results of the 90-day ClinTrials (1997b) study, it is erroneous to 
conclude that neurotoxicity is the most sensitive endpoint for nPB 
exposure.
    Second, the NIOSH medical survey used by Rozman and Doull is not a 
suitable basis for deriving an AEL. Use of epidemiological data for a 
quantitative risk assessment requires that the exposures be well-
characterized, that the sample size be large enough to allow for the 
detection of subtle effects in a statistically significant way, and 
that comparisons to an unexposed control group be made. The data 
provided in the NIOSH evaluation do not fit these criteria: (1) The 
sample size in this study was relatively small (46 participants); (2) 
the health survey was not given to an unexposed control population for 
comparison; (3) no obvious exposure-response trend for headache was 
seen, since the low and medium exposure groups had similar prevalence 
of headache. For each of the neurological symptoms evaluated in the 
NIOSH health survey, air concentrations of nPB were not statistically 
different between those employees reporting the symptom compared to 
those not reporting the symptom (NIOSH 2002).
    Finally, EPA disagrees with Rozman and Doull's conclusion that 
reproductive toxicity did not occur in workers exposed to up to 190 ppm 
of nPB, which is the basis for their assertion that humans are less 
sensitive to reproductive health effects of nPB compared to rats 
(Rozman and Doull, 2001). The NIOSH report states that 3 workers (2 
male and 1 female) who had been exposed to between 110 and 157 ppm of 
nPB reported difficulty in having a child. However, as noted by the 
authors of the NIOSH report, due to the small sample size and the 
personal nature of the questions, there were significant limitations in 
the ability of the NIOSH medical survey to detect reproductive or 
fertility problems. The data from the NIOSH medical survey should not 
be used to conclude that rats are more sensitive than humans to 
reproductive effects of nPB, or to draw any general conclusions 
regarding the potential reproductive toxicity of nPB in humans.
    In the second analysis submitted by Enviro Tech, SLR International 
Corporation derived an AEL for nPB of 156 ppm (SLR International, 
2001b). We understand that this derivation is currently undergoing peer 
review for potential publication in a scientific journal. This analysis 
used benchmark dose-response modeling using data sets for several 
effects taken from the various animal toxicity tests that have been 
conducted with nPB. SLR derived a BMDL at a 10% response level of 156 
ppm, based on reduced sperm motility in F1 males from the WIL (2001) 
study. This BMDL is similar to EPA's BMDL for sperm motility of 169 
ppm. SLR stated that ``Due to the relative completeness of the 
toxicological database on nPB, including data on human in vitro 
bioassays, use of a UF is likely not considered necessary for this 
chemical.'' Thus, SLR's recommended AEL is equivalent to their BMDL. 
EPA maintains that an uncertainty factor is necessary for protection of 
sensitive individuals since low sperm count is a condition that can 
occur in otherwise healthy workers. There are no data indicating that 
human sperm are less sensitive than rat sperm. In fact, sperm 
production is less efficient in humans, suggesting that human males are 
likely to be more susceptible than rats to nPB (Amann, 1986). Further, 
based on EPA's RfC guidelines, an uncertainty factor of 3 is necessary 
to account for interspecies differences in pharmacodynamics between 
rats and humans. Had SLR applied what EPA considers appropriate 
uncertainty factors, their recommended AEL would have been 17 ppm.
    In a memorandum submitted to Poly Systems International, Joel 
Charm, a certified industrial hygienist, supported the analyses by both 
SLR and Rozman and Doull. Mr. Charm suggested that establishing an 
occupational exposure level of 100 ppm as a ceiling value (i.e.,

[[Page 33299]]

a level not to be exceeded during any part of the working day), coupled 
with an effective Product Stewardship program, would help companies 
maintain exposure to their workers as low as reasonably achievable. He 
suggests that a Product Stewardship program focused on: (1) Training 
material on how nPB can be handled and used safely; (2) conducting 
industrial hygiene evaluations as a service to customers, to develop 
actual exposure level information for a variety of end uses under 
varying circumstances; and (3) monitoring the health (including 
reproductive parameters) of workers would, over time, aid in assessing 
the validity of the occupational exposure limit selected. He also 
states that through the Product Stewardship program and the regulatory 
reporting requirements of the Toxic Substances Control Act (TSCA), 
Section 8, corrective actions could be taken if necessary.
    While we do not agree with the AELs derived by Rozman and Doull or 
by SLR, EPA agrees that producers and formulators of nPB should engage 
in responsible Product Stewardship programs. Albermarle Corporation has 
been conducting an extensive stewardship program for nPB involving air 
sampling and workplace practice evaluation for customers to help ensure 
exposures below 25 ppm. We also note that, in order to verify if 
exposure levels are below a ceiling value, it would be necessary to 
monitor workplace exposure continuously. Periodic evaluations of 
exposure levels would be sufficient for determining long-term exposure 
to workers. EPA recommends that workplace exposures should be 
controlled to levels at or below the AEL in order to avoid risk of 
adverse health effects.
    e. Feasibility of meeting the AEL for nPB in each industrial 
sector. Each of the three sectors EPA is considering in today's 
proposal could potentially expose workers to nPB in different ways. 
Therefore, we considered separately whether it is feasible to meet the 
AEL in each of the three sectors. If EPA becomes aware of further 
information showing that nPB use is likely to pose unacceptable risks 
to human health in particular applications or end uses, we will find 
nPB unacceptable in those applications or end uses.
    Solvents cleaning. When using industrial cleaning equipment, 
workers are likely to be exposed to solvent vapors continually over the 
course of a workday. However, users can control nPB emissions from 
vapor degreasers by changes to the equipment, as well as changes in 
operating practice. For example, a user can install an additional set 
of condensation coils to prevent vapor from leaving the vapor degreaser 
or defluxer. An operator can tilt pieces to be cleaned to allow the 
solvent to drain off inside the vapor degreaser instead of evaporating 
outside of the degreaser where workers will breathe the vapors.
    Exposure data on nPB used in vapor degreasers indicate that it is 
possible to maintain exposure levels from 2 to 24 ppm over an 8-hour 
average, as measured using personal samplers (Albemarle, 1997). In 
1998, Albemarle Corporation also collected workplace monitoring data 
from metal cleaning operations. Many, although not all, of the samples 
collected showed concentrations that, extrapolated to an 8-hour period, 
would remain under 25 ppm. In addition, another manufacturer and 
distributor of nPB-based solvents stated that, ``For a properly 
designed, installed, operated, and maintained traditional open-top 
vapor degreaser, experience has shown that eight-hour time weighted 
operator exposure levels will be < 20 ppm. For enclosed and automated 
degreasers, lower exposures can be achieved'' (Amity UK Ltd, 2001).
    EPA has only one set of direct exposure data for equipment that 
cleans using nPB below its boiling point (``cold cleaning''). These 
data are from a NIOSH Health Hazard Evaluation for a company that 
produces instrumentation and components for radio and microwave 
frequency communications. In this study, NIOSH measured exposures to 
nPB from a cold batch cleaner that was in a special enclosed room with 
a local exhaust ventilation system. The highest exposure level was 8.4 
ppm (NIOSH, 2000b). However, the type of enclosure and ventilation used 
at this site is not typical of most facilities using cold cleaning 
equipment.
    In general, it is expected that it will be more difficult to 
control emissions from cold cleaning equipment than from vapor 
degreasers. The design of vapor degreasers reduces emissions from the 
equipment by boiling the solvent and then causing it to condense, 
rather than allowing solvent vapors to be emitted. Because cold 
cleaning equipment may expose workers to high levels of nPB, we 
recommend that nPB not be used in cold cleaning equipment unless 
additional engineering controls are instituted to keep worker exposure 
to levels below the recommended AEL of 25 ppm.
    The limited data available on manual cleaning indicate that it may 
be difficult to attain exposures less than 50 ppm when wiping with nPB 
by hand (Albemarle, 2001). The SNAP program currently does not regulate 
manual cleaning with solvents. However, we recommend that nPB not be 
used for manual cleaning because of the likelihood of high exposures.
    Aerosol Solvents. Only limited data are available on exposure 
levels to nPB from aerosol solvent usage. Four measurements on a single 
user showed exposures to nPB that ranged from 5 to 14 ppm over an 8-
hour time-weighted average (Albemarle, 2001). Since the user was 
cleaning brakes on public works equipment, it is possible that the 
mechanic was working outdoors, or in an area that was only partially 
enclosed. EPA expects that these data are not representative of the 
diverse conditions under which aerosol solvents are used. Confidential 
data from another facility revealed that exposures vary greatly and in 
some instances can be higher than 200 ppm. In contrast to vapor 
degreasers, aerosol solvents tend to be used intermittently for short 
periods of 1-2 minutes. In some cases, aerosols containing nPB are used 
in confined spaces without ventilation ducts and fans where workers 
could be exposed to high levels over a short time. Emissions from 
aerosols are typically not controlled with equipment that captures the 
nPB vapor, although aerosol users can improve ventilation and reduce 
exposure levels through a variety of approaches (e.g., fume hoods). 
Given this information, EPA requests further workplace exposure data on 
nPB's use as an aerosol solvent. In addition, we request comment on 
whether nPB should be acceptable for use as an aerosol solvent, or if 
its use should be limited in this end use (e.g., use limit restricting 
nPB only to applications with ventilation equipment).
    EPA believes that users should adhere to a short-term exposure 
limit (time weighted average over 15 minutes) of three times the AEL. 
We recommend this short-term exposure limit, which would equal 75 ppm 
over 15 minutes, in addition to the 8-hour time weighted average of 25 
ppm. We believe that limiting short-term exposure to 75 ppm in a 15 
minute period of exposure is feasible with proper ventilation and/or 
low use volumes. We also recommend only using aerosols containing nPB 
in open or well-ventilated areas. This procedure is recommended for use 
of any aerosol solvent, compared to use in enclosed, unventilated 
areas.
    Adhesives. In adhesives applications, exposures are expected to 
vary depending upon the particular kind of application. For example, in 
the foam-fabrication industry, workers generally are exposed to 
evaporating solvents on

[[Page 33300]]

a long-term basis. When adhering tops on counters or tables, workers 
are more likely to have breaks between exposure, with short-term 
exposure being of greater concern (HSIA, 2001).
    EPA is aware that it may be difficult to meet the recommended 25 
ppm AEL in adhesive applications that are highly emissive. Exposure 
data from nPB used in adhesives in the foam-fabrication industry show 
high nPB concentrations within the workplace. At three different foam-
fabrication facilities, NIOSH investigators reported that mean 
exposures to nPB ranged from 60 to 381 ppm (8-hour time weighted 
averages) (NIOSH, 1999, 2000a, 2000c, 2001). In one facility, average 
nPB exposures were reduced from 169 ppm to 19 ppm, following 
installation of ventilation equipment recommended by NIOSH (NIOSH, 
2000c). Although use of spray booths at this facility had a dramatic 
effect of reducing average exposures to nPB, a significant percentage 
of workers whose jobs required direct use of spray adhesive containing 
nPB continued to have exposures in excess of 25 ppm. Among sprayers and 
assemblers working in the Assembly area, 2 of 10 (20%) full-shift 
samples exceeded 25 ppm, and among sprayers working in the Covers 
department, 9 of 11 (81%) of samples exceeded 25 ppm, with a maximum of 
58 ppm (time-weighted average, TWA). These findings indicate that it 
may be necessary for employees to wear appropriate respiratory 
protection where engineering controls do not reduce exposures to or 
below the AEL. Where respirators are used to protect workers against 
nPB, employers should be aware that OSHA's Respiratory Protection 
standard (29 CFR 1910.134) would apply.
    Because there is evidence that workplace exposures to nPB can be 
reduced to levels close to or below the recommended AEL, the Agency has 
concluded that it is appropriate to find the use of nPB acceptable in 
adhesive applications. Nevertheless, EPA expects that businesses using 
nPB in adhesive applications may have difficulty meeting the 
recommended exposure limit without some form of engineering controls 
such as confining operations to spray booths with ducts and a fan 
providing ventilation. Further, although use of spray booths at this 
facility had a dramatic effect of reducing exposures to nPB, as 
discussed above, some workers whose jobs required direct use of spray 
adhesive containing nPB continued to be exposed to nPB in excess of 25 
ppm. Given this information, EPA requests comment on whether nPB should 
be acceptable for use in adhesives.
    EPA conducted a detailed risk screen for nPB use in adhesives 
applications in the foam fabrication industry (ICF, 2001a , Attachment 
C) since this represents the most emissive use, and the use where 
workers and the general population have the highest exposures. Because 
this highly emissive use passed our risk screen, we did not conduct a 
formal risk screen for the solvents cleaning sector and aerosol 
solvents sectors end use, because emissions and worker exposures in 
these uses are expected to be lower than the adhesives end use.
2. Are There Other Entities That May Set or Recommend Workplace 
Standards?
    Under the National Technology Transfer and Advancement Act of 1995, 
Section 12(d), Public. Law. 104-113, Federal agencies are required to 
consider using technical standards that are developed or adopted by 
voluntary consensus standards bodies, using such technical standards as 
a means to carry out policy objectives or activities. No such standards 
for occupational exposure to nPB currently exist. In comparison, the 
American Conference of Governmental Industrial Hygienists (ACGIH) has 
established threshold limit values (TLVs) for the primary chlorinated 
solvents used in the same applications as nPB. The most current TLVs 
for these solvents--25 ppm for perchloroethylene, and 50 ppm for 
trichloroethylene and methylene chloride--are identical or moderately 
higher than our proposed recommended guideline for nPB. It is possible 
that the American Industrial Hygiene Association (AIHA) or the ACGIH 
will review the toxicity of nPB in the future and set a voluntary 
standard. AIHA may develop a Workplace Environmental Exposure Limit 
(WEEL) for nPB. Further, in 2002, the ACGIH listed 1-Bromopropane and 
2-Bromopropane (nPB and iPB, respectively) in its list of ``Chemical 
substances and other issues under study.'' If either of these standard-
setting bodies recommends an exposure limit on nPB, we would make that 
information available to the public for comment.
    In the future, OSHA may develop a mandatory exposure limit for nPB 
use in the workplace. The result of OSHA's review could result in a 
permissible exposure limit (PEL) different from EPA's recommended 
exposure limit of 25 ppm. Unlike nPB, the chlorinated solvents are 
regulated by OSHA and have been regularly re-evaluated by OSHA, NIOSH, 
and EPA (e.g., as a National Emission Standard for Hazardous Air 
Pollutants). The most current permissible exposure limits for these 
solvents established by OSHA are 25 ppm for methylene chloride and 100 
ppm for perchloroethylene and trichloroethylene. The OSHA permissible 
exposure levels for perchlorethylene and trichloroethylene of 100 ppm 
were originally issued on 1971 based on the 1968 threshold limit values 
established by the ACGIH. Since then, ACGIH has issued TLVs of 25 ppm 
for perchloroethylene and 50 ppm for trichloroethylene and OSHA has 
issued a PEL of 25 ppm for methylene chloride; as such, the Agency does 
not believe that a 25 ppm recommended AEL for nPB would result in a 
significant competitive advantage for any of these solvents. As stated 
earlier in this preamble, EPA defers to OSHA in regulating workplace 
safety. The recommended AEL in today's proposal is an interim measure 
in the absence of an OSHA PEL. Thus, any PEL that OSHA sets would 
supersede EPA's recommended AEL.
3. Is the General Population Exposed To Too Much nPB?
    As a part of the SNAP review process for alternative chemicals, EPA 
also considers exposure to the general population. Near facilities that 
use nPB in non-emissive applications such as vapor degreasing, exposure 
is expected to be insignificant. For emissive applications of nPB, such 
as an adhesive solvent in foam fabrication, we conducted a more 
detailed assessment of potential exposure to people living in the 
immediate vicinity of a facility. We first estimated a community 
exposure guideline, using EPA's Methods for Derivation of Reference 
Concentration Guidelines (1994) as a risk index to compare against 
potential community exposure. This community exposure guideline is an 
estimate of a continuous inhalation exposure (averaged over 24 hours 
per day, 7 days per week) to the general public (including sensitive 
subgroups) that is likely to be without an appreciable risk of adverse 
health effects during a lifetime. Community exposure guidelines can be 
derived from a NOAEL, LOAEL, or benchmark concentration, with 
uncertainty factors generally applied to reflect limitations of the 
data used. Average daily exposures of people living close to facilities 
where nPB is used in an emissive application were then estimated and 
compared to the community exposure guideline to determine whether nPB 
exposure presents an appreciable risk to the general population.
    EPA derived the community exposure guideline for nPB using the same 
critical

[[Page 33301]]

studies and BMDLs for spermatic effects and liver effects that were 
used in developing the AEL. Adjustments were made to account for 
continuous lifetime exposure and sensitive subpopulations. The lowest 
BMDL of 110 ppm was based on the incidence of liver effects 
(centrilobular vacuolation) in the two-generation reproductive study 
(WIL, 2001). Using EPA's dosimetry guidelines for a category 3 gas (US 
EPA, 1994), and making adjustments to account for continuous exposure, 
the human equivalent concentration (HEC) is 110 ppm * (6 hours/24 
hours) = 27.5 ppm. No adjustment for differences in pharmacokinetics 
was necessary based on EPA's RfC guidelines. EPA applied an UF of 3 for 
extrapolation from rat to human pharmacodynamics. An additional factor 
of 10 was applied for intrahuman variability including the protection 
of sensitive subpopulations (e.g., individuals with liver disease, 
children, or the elderly). Therefore, the total uncertainty factor was 
30 (3 for differences in pharmacodynamics, 10 for sensitive 
subpopulations). The application of the uncertainty factor of 30 to the 
HEC of 27.5 ppm results in a community exposure guideline of 
approximately 1 ppm. EPA requests comment on the appropriate use of 
uncertainty factors for the community exposure guideline.
    The next lowest BMDL (169 ppm) was for the effects on sperm 
motility in the second generation of male rats in the two generation 
study. In the derivation of a community exposure guideline RfC for this 
endpoint, EPA adjusted the BMDL to account for continuous exposure 
averaged over 24 hours a day, resulting in an HEC of 42 ppm. An 
uncertainty factor of up to 10 may be applied for animals to human 
extrapolation in consideration of potential differences in 
pharmacokinetics and pharmacodynamics. However, for the reasons listed 
earlier, we did not consider an uncertainty factor necessary to account 
for differences in pharmacokinetics. The results of the in vitro 
studies conducted with liver cells do not allow us to draw any 
conclusions regarding the relative sensitivity of the human and rat 
spermatocyte to nPB. Consequently, EPA applied a factor of 3 for 
differences in pharmacodynamics. Finally, an uncertainty factor of 10 
was applied for intrahuman variability including the protection of 
sensitive individuals in the general population (e.g., children whose 
sex organs are in development, pregnant women, and individuals with low 
fertility). An overall uncertainty factor of 30 results (3 for 
differences in pharmacodynamics, and 10 for the protection of sensitive 
individuals). The application of the overall uncertainty factor (30) to 
the HEC (42 ppm) results in a community exposure guideline an RfC of 
approximately 1 ppm. The estimated community exposure guideline values 
are identical for both liver and reproductive effects. Consequently, 
EPA estimated that a RfC community exposure guideline of 1 ppm would be 
protective for all health endpoints--that is, someone exposed to an 
average of 1 ppm of nPB, 24 hours of every day during a lifetime, would 
not be at appreciable risk for adverse health effects during their 
lifetime.
    The next step was to determine whether people living close to sites 
where nPB is used in emissive applications could potentially be exposed 
to levels above the estimated RfC community exposure guideline of 1 
ppm. Data collected from actual facilities (CCPCT, 2001) used to 
characterize two scenarios: (1) A typical large, high-use adhesive 
application facility where the closest resident is 100 meters away; and 
(2) a smaller facility with average-use adhesive application in an 
urban area, where the nearest resident is only 3 meters away.
    EPA's SCREEN3 (US EPA, 1995a) air dispersion model was used to 
assess the likely maximum-potential concentration of nPB from single 
sources. This technique is typically used to evaluate air quality 
impacts of sources pursuant to the requirements of the Clean Air Act, 
such as New Source Review and air toxic regulations. The approach 
applied here was the initial-phase approach used to determine if 
either: (1) The source clearly poses no air quality problem or (2) the 
potential for an air quality problem exists. If a potential problem 
exists, then a more refined analysis is necessary.
    The results from our screen indicated that modeled exposures in 
either scenario did not exceed the RfC of 1 ppm. The urban scenario 
where a facility uses fans to ventilate nPB horizontally (through 
windows or other openings in the walls as opposed to openings in the 
roof), modeled exposures of 0.24 ppm at a distance of 3 meters away 
from the source, 0.19 ppm at 5 meters from the source, and 0.13 ppm at 
10 meters from the source. These levels were by far the highest 
concentrations of nPB exposures modeled. The majority of modeled 
exposures were at least an order of magnitude lower, and ranged from 0 
ppm to 0.08 ppm. Because the community exposure guideline was not 
exceeded for any of the exposure scenarios in this conservative 
screening approach, EPA has concluded that nPB exposure to populations 
living close to adhesive application sites is not a major concern. A 
memo describing the risk screen in detail may be found in the public 
docket (ICF, 2002a).
4. What Limit Is EPA Proposing on Isopropyl Bromide Contamination of 
nPB as a Condition of Acceptability, and Why?
    Isopropyl bromide (iPB or 2-bromopropane), an isomer of nPB (1-
bromopropane), is a contaminant that is created to different degrees in 
the manufacture of some nPB formulations. In reviewing the 
toxicological risks of iPB, EPA initially was concerned that its 
molecular structure was similar to chemicals that are potent 
reproductive toxins and carcinogens. This concern focused on the 
position of the halogen atom within the compound. There are 
toxicological data that indicate that when the halogen atom is located 
on the second carbon, there may be increased potential for the compound 
to cause cancer when compared to the compound with the halogen atom on 
carbon number 1. One example of this is the differential toxicity of 1-
nitropropane and 2-nitropropane. Inhalation exposure to 2-nitropropane 
has been linked to liver toxicity in humans and has resulted in liver, 
and to a lesser extent, lung toxicity in male and female Sprague-Dawley 
rats (US EPA, 1991); it has also been shown to induce liver cancer in 
both Sprague-Dawley (IARC, 1992) and Fischer rats (Fiala, 1995). 1-
Nitropropane has shown no carcinogenic potential to date.
    Direct data on the carcinogenic potential of iPB are limited, 
although it has been shown to induce reverse mutations in bacteria 
(Maeng and Yu, 1997). Further, iPB was shown to be more cytotoxic and 
genotoxic to human liver cells than nPB and other toxins, including 
methylene chloride and trichloroethylene (SLR, 2001a). The combination 
of the position of the bromine atom in iPB (and its relationship to the 
carcinogenic potential of the compound) and the genotoxicity of the 
compound in bacterial and human cells indicate that caution is 
necessary when recommending an acceptable exposure concentration for 
iPB.
    In the limited animal testing data available, iPB has been shown to 
be inherently more toxic than nPB on reproductive and hematopoietic 
endpoints. In two separate studies, significant disruptions in the 
estrous cycles and abnormal growth in uterine cells were reported in 
female rats

[[Page 33302]]

exposed to iPB daily for 9 weeks (Kamijima, 1997a, 1997b; Yu, 2001). 
Daily exposure of male rats to iPB at 300, 1000, and 3000 ppm was 
associated with effects ranging from reduced body and organ (e.g., 
kidneys, liver, testis) weight, reduced sperm counts and sperm 
motility, abnormal sperm, reduced red blood cell and platelet counts, 
and hemoglobin volume (Ichihara, 1997). A recent study has been 
published (Sekiguchi, 2002) in which the effects of iPB exposure on the 
reproductive physiology of female F344 rats were investigated. The rats 
were exposed to air (in the control group, the number of animals, n, is 
7) or 50 (n=6), 200 (n=7), or 1000 (n=9) ppm of iPB via whole-body 
inhalation for 8 hours/day for 21-24 days (exact number of days not 
specified in the article). A larger number of females at the high 
concentration exhibited an estrous cycle of 6 days (7 of 9 
animals) than those at the control, low- and mid-concentration (4, 2, 
and 3, respectively) which corresponded to the greater number of 
estrous cycles lasting 6 days (9 of 34 animals) in the high-
concentration group as compared to the other groups (4 of 31, 4 of 30, 
3 of 30). A dose-dependent increase in the number of days/cycle was 
observed in rats at 200 and 1000 ppm. These increases did not reach 
statistical significance, however. A smaller number of females per 
group was analyzed for uterine and ovary weights because only rats 
showing the estrous stage upon vaginal smear test were chosen for 
autopsy (5, 5, 5, and 7, respectively in the low-, mid-, and high-
concentration groups). No changes were noted in the weights of ovaries 
or uterus, or in the number of ovulated ova among any of the female 
groups (exposed or controls). Although this study indicates that iPB 
was not a strong reproductive toxin in the female rat, the small number 
of animals exposed is a significant limitation to the study. The dose 
dependent increase in estrous cycles observed at 200 and 1000 ppm 
suggest the potential for reproductive failure from exposure to this 
compound. These results also indicate the need for additional studies 
using greater numbers of exposed animals.
    Both male and female workers occupationally exposed to iPB have 
been found to exhibit some of the same effects reported in animal 
toxicological studies. Ichihara (1999) reported low sperm motility, low 
semen volume, abnormal sperm cells, and decreased blood cell count, 
hemoglobin and hematocrit in otherwise healthy Chinese male workers 
exposed to a wide range of iPB concentrations (2.5-111 ppm). Abnormal 
or an absence of menstruation was associated with iPB exposure in 
several female workers, as well as reduced blood cell count, 
hemoglobin, and hematocrit. Employees of an electronics factory in 
South Korea showed similar effects following exposure to iPB (Kim, 
1996). In female workers, disrupted or absent menstruation, abnormal 
hormone levels, hot flashes, and abnormal bone marrow were found, while 
male workers exhibited significantly reduced sperm counts and sperm 
motility.
    CERHR convened an Expert Panel to consider existing toxicological 
studies on effects of both nPB and iPB. (See section IV.A.1.c. for a 
discussion of CERHR review process and the Expert Panel Report.) The 
CERHR Expert Panel came to the following conclusions on the existing 
studies on iPB (CERHR, 2002b, p. 44):
    [sbull] Available human and animal data are insufficient to draw 
conclusions on the potential for developmental toxicity due to iPB.
    [sbull] There is sufficient evidence that iPB is a reproductive 
hazard in men and women, particularly based upon the epidemiological 
data from Korea.
    [sbull] At low levels (less than 0.004 ppm), there is minimal 
concern for human reproduction. At higher levels up to 1.35 ppm, there 
is some concern.
    [sbull] For reproductive data from male rats, the panel identified 
a NOAEL of 100 ppm.
    The toxicological studies on male reproductive endpoints for iPB 
have limitations which (e.g., small number of dose groups) make them 
inappropriate for use in quantitative risk assessment. Although the 
occupational exposure studies also are limited, given the mutagenicity 
of the compound and that human exposures have resulted in significant 
health effects consistent with those reported in the available animal 
studies, the Agency considers it appropriate to limit the amount of iPB 
exposure resulting from nPB use to the maximum extent feasible.
    Today's action proposes to limit SNAP acceptability of nPB to those 
formulations of nPB that contain concentrations less than 0.05% iPB by 
weight before adding stabilizers or other chemicals. The current 
American Society for Testing and Materials (ASTM) standard for vapor 
degreasing grade and general grade nPB specifies that unstabilized nPB 
must have less than 0.1% of iPB as a contaminant. EPA believes that 
this level should be reduced to 0.05% given the toxicity of iPB, and 
the fact that achieving a level of 0.05% is technologically feasible 
and would not cause significant economic impacts (US EPA, 2003). The 
Agency also requests comment on the appropriateness of alternative 
concentration limits for iPB in nPB, including 0.1%. If this provision 
is finalized, the iPB concentration limit would be a condition that all 
users in the U.S. must observe in all sectors and end uses where nPB is 
listed as acceptable.
    In order to show compliance with the use condition, end users would 
need to keep records to demonstrate that the nPB used in the product 
contains no more than 0.05% iPB by weight before adding stabilizers or 
other chemicals. Documentation could involve, for example, keeping a 
certificate of analysis or purity provided by the manufacturer or 
formulator for two years from the date of creation of that record. Such 
records are customary business information that chemical companies 
provide to their customers, so we do not expect that this requirement 
will impose an additional paperwork burden.

B. Ozone Depletion Potential

    The ozone depletion potential (ODP) of a chemical compound provides 
a measure of its impact on stratospheric ozone levels relative to the 
impact of an equal mass emission of CFC-11. The Parties to the Montreal 
Protocol have used the ODP benchmark index as a means of characterizing 
the relative risks associated with the various ozone-depleting 
compounds subject to the requirements of the Protocol and to calculate 
the total allowable production and consumption of different classes of 
ozone depleting substances. Every four years the World Meteorological 
Organization publishes the Scientific Assessment of Ozone Depletion. 
These assessments are authored by leading experts in the fields of 
atmospheric science and atmospheric chemistry, and include the most 
current research findings relevant to the science of ozone depletion. 
These assessments, along with other studies in the field of atmospheric 
chemistry, have traditionally focused on compounds with relatively long 
atmospheric lifetimes (in excess of 3 months).
    Two-dimensional (2-D) models that base calculations on latitude and 
altitude are sufficient for calculating the ODP of long-lived 
chemicals. However, 2-D models cannot simulate the complex atmospheric 
transport pathways that are necessary to determine the ODP of short-
lived compounds like nPB (Wuebbles, 2000). nPB is estimated to remain 
in the atmosphere for only 11 to 20 days after

[[Page 33303]]

emission.\12\ The short lifetime of nPB complicates the calculation of 
its ODP because it is not valid to make the standard simplifying 
assumption that concentrations are ``well mixed'' in the troposphere. 
Thus, a meaningful comparison can be made between the ODP of nPB and 
the longer-lived compounds already controlled under the Montreal 
Protocol only by using the results from a 3-D model that bases 
calculations on longitude, latitude, and altitude to augment the ODP 
calculation using a 2-D model.
---------------------------------------------------------------------------

    \12\ Wuebbles et al., 1998; Wuebbles et al., 2000.
---------------------------------------------------------------------------

    Generally, a compound emitted in the troposphere travels toward the 
equator and into the tropics before rising convectively into the 
stratosphere. As a result, a compound emitted at high latitudes, such 
as the northern United States or the southern tip of Brazil, will take 
longer to reach the stratosphere than one emitted in the tropics. For a 
long-lived chemical, this difference in travel time is insignificant. 
But for a short-lived compound such as nPB, which is subject to 
degradation in the troposphere, the latitude of emission can have a 
significant impact on the amount of ozone-destroying bromine that is 
delivered to the stratosphere.
    Using a combination of 2-D and 3-D models, Wuebbles et al. (2001) 
estimated the ODP to be between 0.016 and 0.019 for nPB emissions over 
the United States. In the tropical latitudes, over India, Southeast 
Asia and Indonesia, nPB emissions have a larger ODP of 0.087 to 0.105. 
A more recent paper by Wuebbles found that the ODP of nPB emissions 
from the United States would be closer to 0.013-0.018, while nPB 
emissions in the tropics would have an ODP of 0.071 to 0.100 (Wuebbles, 
2002).
    In proposing to list nPB as an acceptable substitute for CFC-113, 
methyl chloroform and HCFC-141b, EPA has considered that the ODP for 
nPB at the latitude of the continental U.S. is substantially less than 
the ODPs for the chemicals it would replace (0.8 for CFC-113, 0.1 for 
methyl chloroform, and 0.11 for HCFC-141b). Given that fact, we do not 
believe that nPB's ODP is a compelling reason to list it as an 
unacceptable substitute for CFC-113, methyl chloroform, and HCFC-141b 
for use in the U.S.
    While advances in modeling are producing more specific methods to 
better estimate nPB's ODP, the value will never be pinpointed to a 
single number that may be applied to all latitudes. EPA notes that if 
the ODP were as high in the U.S. as it is in the tropics (0.071 to 
0.100), we would have found it unacceptable as a substitute. When 
making regulatory determinations, governments or users in other 
latitudes should consider the ODP at their latitude as well as the 
toxicity of other solvents available for use. For example, users in 
other counties may find nPB preferable to carbon tetrachloride, which 
has a high ODP (1.1) and is highly toxic. On the other hand, users in 
the tropics should realize that nPB at their latitude has an ODP 
comparable to substances controlled by the Montreal Protocol (methyl 
chloroform or HCFC-141b). EPA also recommends that any decisions on the 
use of nPB outside the U.S. should be based on latitude-specific ODPs 
and volumes of the chemical projected to be used in those regions.
    Few commenters on the ANPRM discussed the ODP of nPB. However, the 
Agency agrees with two commenters who stated that nPB's low ODP should 
be balanced against the much longer atmospheric lifetime of other 
choices.
    We have attempted to gather and assess all available information 
from the full range of experts on nPB's ODP. EPA continues to be 
interested in receiving from the public any other information 
pertaining to the atmospheric effects and ODP of short-lived 
atmospheric chemicals, especially nPB. In the event that data become 
available after final rulemaking that are contrary to the current 
scientific understanding, section 612 of the CAA allows the Agency to 
reconsider our decision under the SNAP program.

C. Global Warming Potential

    The global warming potential (GWP) index is a means of quantifying 
the potential integrated climate forcing of various greenhouse gases 
relative to carbon dioxide. Thus, the GWP of carbon dioxide is, by 
definition, equal to one. Since GWP is a measure of the climate forcing 
integrated over time, the value of the index depends on the choice of 
time horizon. The standard GWP used for making climate-related policy 
decisions is based on a 100-year time horizon (called the 100yr 
GWP).\13\
---------------------------------------------------------------------------

    \13\ The 100yr GWP is the index recommended by the 
Intergovernmental Panel on Climate Change (IPCC) for comparing the 
climate impacts of various global warming gases. The United States 
employs the standard 100yr GWP index for making climate policy 
decisions and reporting of greenhouse gases.
---------------------------------------------------------------------------

    The 100yr GWP of nPB is 0.31 (Atmospheric and Environmental 
Research, Inc., 1995). This is a relatively low GWP, representing a 
climate forcing approximately one third that of carbon dioxide, by 
weight. Estimations of the net climate impact must take into 
consideration the amount of the compound expected to be emitted. As 
will be discussed in section V.B. below, nPB will most likely be 
emitted in small enough quantities worldwide that there should not be a 
concern about its causing climate change. Additionally, the GWP of nPB 
is considerably lower than that of the chemicals it potentially 
replaces. (100yr GWP values are 6000 for CFC-113, 140 for methyl 
chloroform and 700 for HCFC-141b.) \14\ Therefore, we conclude that the 
use of nPB as a substitute for CFC-113, HCFC-141b, or methyl chloroform 
should not be restricted based on its GWP.
---------------------------------------------------------------------------

    \14\ All GWPs (other than that of nPB) discussed in this NPRM 
are taken from the Scientific Assessment of Ozone Depletion: 1998 
(WMO, 1999).
---------------------------------------------------------------------------

D. Flammability

    nPB forms flammable mixtures in air within only a narrow range. All 
estimates that EPA reviewed fall somewhere within the range of 3.5%-9%. 
Most, but not all, of the material safety data sheets we reviewed state 
that nPB has no flashpoint. The 1998 Report of the United Nations 
Environment Programme's Solvents, Coatings and Adhesives Technical 
Option Committee stated that ``under certain test conditions, using 
standard flash point testing apparatus, pure nPB has demonstrated a 
flash point at -10[deg]C * * * [O]ther ASTM test methods have resulted 
in no observed flash point'' (UNEP, 1999). In response to information 
requests in the nPB ANPRM, various commenters asserted that nPB has a 
flashpoint of 10[deg]C, 14[deg]C, and 21[deg]C-25[deg]C, 70[deg]F 
(21[deg]C), and 70[deg]C. These data are inconclusive about the 
flashpoint of nPB and whether nPB is likely to be flammable under 
normal use conditions.
    In addition, we are aware that many manufacturers of foam cushions 
use adhesives containing nPB because it is essentially non-flammable 
compared to many other solvents used in adhesives, such as acetone or 
heptane. Also, one company has submitted a fire suppressant containing 
nPB as the active ingredient for review by the SNAP program. (We are 
not addressing this incomplete submission in today's proposed rule.) It 
is not surprising that nPB would have little or no flammability, given 
that many organic compounds containing bromine have little or no 
flammability, such as halons or hydrobromofluorocarbons.
    Based on the full range of available information, we do not 
currently believe that the use of nPB as a substitute for CFC-113, 
methyl chloroform, or HCFC-141b should be restricted because of 
flammability. EPA, however, invites

[[Page 33304]]

commenters to submit more specific information concerning the 
flashpoint of pure nPB. We are aware that nPB blends may have 
flashpoint characteristics different from that of pure nPB, depending 
on the nature of the additives or stabilizers. In this rulemaking, EPA 
is evaluating only pure nPB as a substitute for CFC-113 and methyl 
chloroform. We therefore are not interested in receiving information 
concerning the flashpoints of blends that contain nPB. Commenters 
providing information on nPB's flashpoint should refer to the specific 
test methodology and apparatus used to determine the flashpoint, such 
as ISO 1523, American Society of Testing Materials (ASTM) E-681, D92, 
D93-85--Pensky-Martens closed cup, or D56-96--Tag closed cup. EPA also 
invites readers to submit information concerning any potential fire or 
explosion hazards that may result from the use in solvent cleaning of 
compounds that have flashpoints within the range of normal atmospheric 
pressures and temperatures.

E. Other Environmental Concerns

    Because nPB breaks down in the atmosphere within 21 days, and is 
not particularly soluble in water, it is unlikely that ``rain out'' 
from nPB released into the atmosphere could cause contamination of 
water supplies. However, as with all chemicals, significant 
contamination of soil and water can result when directly introduced 
into water or onto the ground. Thus, EPA expects that users will 
dispose of nPB in accordance with relevant regulations under the 
Resource Conservation and Recovery Act, and with applicable state and 
local regulations. Compliance with these regulations will mitigate the 
possibility that nPB might enter water supplies or top soil.
    nPB is a volatile organic compound (VOC). VOCs are associated with 
the formation of ground-level ozone, a respiratory irritant. Therefore, 
nPB use currently is controlled under state and local regulations 
implementing Federal clean air requirements at 40 CFR part 51. These 
regulations are intended to bring areas into compliance with the 
National Ambient Air Quality Standards for ground-level ozone. Users 
located in ozone non-attainment areas may need to consider using other 
alternatives for cleaning that are not VOCs or control emissions.

F. Comparison of nPB to Other Solvents

    Section 612 of the Clean Air Act directs EPA to determine the 
acceptability of a replacement substance (``substitutes'') for class I 
and class II ozone depleting substances based on whether such 
substitute creates an overall greater risk to human health and the 
environment than other substitutes that are available. Section 612(c) 
specifically states that the Administrator shall issue regulations:

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

    Thus, 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, consistent with the safe 
alternatives policy of Sec.  612.
    In our evaluation, we considered the substitutes available within a 
given end use. In other words, we compared nPB as a metal cleaning 
solvent against other metal cleaning alternatives, and we compared nPB 
as a carrier solvent in adhesives to other adhesive alternatives. 
Because of the large amount of overlap in the alternatives available in 
the different end uses, the discussion below will mention alternatives 
from multiple end uses where nPB is used.
    Although EPA does not judge the effectiveness of alternatives, this 
factor is an additional one that we consider when determining what 
alternatives are available in a particular application within an end 
use. For example, aqueous cleaners are the substitute of choice for 
many in the metal cleaning end use and many electronics applications 
now use the ``no clean'' technology. However, some types of soils are 
especially difficult to remove and some applications require a high 
degree of cleanliness; thus, in some applications, particularly in 
precision cleaning, there may still be a need for organic solvents for 
cleaning. Depending on the particular application, it may be necessary 
to use an aggressive cleaning solvent such as nPB.
    nPB has an ODP of 0.013 to 0.018 at the latitudes of the 
continental U.S. Thus, nPB reduces risk compared to CFC-113, methyl 
chloroform, and HCFC-141b, the ODSs it replaces, which have ODPs of 
0.8, 0.1, and 0.11, respectively. HCFC-225ca/cb has an ODP of 
approximately 0.03. HCFC-225ca/cb is acceptable in metals cleaning and 
aerosol solvents, and acceptable subject to use conditions in precision 
cleaning and electronics cleaning. Although HCFC-141b has been phased 
out of production in the U.S., its use is currently acceptable in 
aerosol solvents; HCFC-141b has a higher ODP than nPB. HCFC-123 has an 
ODP of 0.0124, which is comparable to that of nPB. HCFC-123 is 
acceptable in precision cleaning. There are other acceptable cleaners 
that essentially have no ODP (aqueous cleaners, hydrofluoroethers 
(HFEs), hydrofluorocarbon (HFC)-4310mee, HFC-365mfc, HFC-245fa, 
hydrocarbons, volatile methyl siloxanes (VMSs), methylene chloride, 
trichloroethylene (TCE), perchloroethylene (PERC), and 
parachlorobenzotrifluoride (PCBTF).
    nPB has a GWP of only 0.31, which is lower than or comparable to 
that of the lowest GWP solvents. Acceptable HCFC, HFC and HFE solvents 
all have GWPs that are two to four orders of magnitude higher than that 
of nPB (55 to 1700 on a 100 year time horizon compared to 
CO2).
    nPB is a volatile organic compound for purposes of EPA regulations, 
although there are petitions with EPA requesting its exemption. Thus, 
nPB currently is subject to regulations for ground-level ozone and 
local air quality. nPB is not currently regulated as a hazardous air 
pollutant and is not listed as a hazardous waste under RCRA.
    nPB is less flammable than many acceptable substitutes, such as 
ketones, alcohols, terpenes, and hydrocarbons. nPB is comparable in its 
low flammability to chlorinated solvents, HCFCs, HFEs, HFC-245fa, HFC-
4310mee, and aqueous cleaners.
    EPA used an acceptable exposure limit of 25 ppm as the basis for 
comparison with measured exposure levels in the workplace to determine 
whether nPB could be used safely, and thus, to determine the 
acceptability of nPB. EPA found that nPB could be used as safely at 25 
ppm as other acceptable solvents when they are used at their AELs or 
other relevant occupational exposure limits, such as OSHA PELs or ACGIH 
TLVs.\15\ Based on the

[[Page 33305]]

assumption that most users will attain exposure levels at or below the 
AEL of 25 ppm, EPA finds nPB acceptable in terms of its human health 
risks. As discussed in section IV.A.4, ``What limit is EPA proposing on 
isopropyl bromide contamination of nPB as a condition of acceptability, 
and why?'' iPB is a contaminant in nPB formulations that is 
considerably more toxic than nPB. Therefore, in order for nPB 
formulations to ``reduce overall risk to human health and the 
environment,'' EPA finds it necessary for users to use nPB formulations 
that have minimal levels of iPB. Hence, the Agency's proposed decision 
of acceptability depends on the condition that users use nPB 
formulations that limit the amount of iPB. EPA's proposes that this 
limit be 0.05% before other chemicals are added.
---------------------------------------------------------------------------

    \15\ The recommended AEL for nPB is lower than that for many 
acceptable solvents (HFEs, ketones, HFCs, HCFC-225ca/cb, 
hydrocarbons), but is higher or comparable to the AEL for some 
acceptable solvents (d-limonene, VMSs, dichlorobenzotrifluoride, 
HCFC-123, methylene chloride, PCBTF). However, a direct comparison 
between two compounds with different AELs does not necessarily mean 
that using a compound with a higher AEL is more risky. Actual 
exposure levels will vary based upon factors other than the AEL, 
such as emission controls in place, work practices, ventilation, 
rate of spraying, and vapor pressure of the solvent.
---------------------------------------------------------------------------

    Balancing these different factors, it is not clear that nPB poses 
greater risks than other substitutes in the same end uses, so long as 
nPB is used consistent with the use condition and recommended AEL. 
Further, it appears that nPB reduces overall risk compared to the ozone 
depleting substances being replaced. Thus, EPA proposes to find that 
nPB is acceptable, subject to a use condition.

V. What Other Factors Did EPA Consider That Are Unique to nPB?

A. Review of nPB by Other Federal and International Programs

    In proposing to find nPB acceptable in solvents cleaning, and as a 
solvent in adhesive and aerosol applications, we have sought to avoid 
overlap with other existing regulatory authorities. EPA's mandate under 
the CAA is to list agents that ``reduce overall risk to human health 
and the environment'' for ``specific uses.'' In light of this 
authorization, EPA is recommending an occupational exposure limit 
which, if adhered to, would result in the safe use of nPB in the 
workplace. This is an interim measure until OSHA issues a PEL for nPB. 
EPA defers to OSHA on workplace safety standards, and is not in any way 
assuming that agency's responsibility for regulating workplace safety.
    As stated in a footnote in today's proposed rule language at the 
end of this document, ``In accordance with the limitations provided in 
section 310(a) of the Clean Air Act (42 U.S.C. 7610(a)), nothing in 
this [rule] shall affect the Occupational Safety and Health 
Administration's authority to enforce standards and other requirements 
under the Occupational Safety and Health Act of 1970 (29 U.S.C. 651 et 
seq.).'' EPA's recommended workplace exposure guidelines, which are not 
regulatory, and use requirements, which are not expressly related to 
use in the workplace, will not bar OSHA from regulating under authority 
of the Occupational Safety and Health Act.
    As mentioned above in section IV.E, nPB is a VOC. Two companies 
have petitioned EPA to exempt nPB from VOC regulations. To date, EPA 
has not received sufficient information on photochemical reactivity of 
nPB and thus, has no plans to exempt it. In contrast to other solvents, 
nPB is not controlled as a hazardous air pollutant under the CAA and 
generates wastes that are not considered hazardous under regulations 
implementing the Resource, Conservation and Recovery Act (RCRA). 
Several commenters on the ANPRM argued that because no U.S. 
environmental authorities regulate nPB use, EPA's SNAP program has all 
the more obligation to establish an acceptable exposure limit for the 
workplace, even if it is recommended rather than mandated (IRTA, 1999). 
With today's proposed rule, EPA is recommending a workplace exposure 
limit to protect workers exposed to nPB in the absence of OSHA 
regulations.
    While the Montreal Protocol currently does not control the 
production and distribution of nPB worldwide, nPB may be controlled by 
the Protocol in the future. At the Thirteenth Meeting of the Parties to 
the Montreal Protocol in Colombo, Sri Lanka, the Parties made a 
decision regarding nPB. Decision XIII/7 states:

    Noting the Technology and Economic Assessment Panel's report 
that n-propyl bromide (nPB) is being marketed aggressively and that 
nPB use and emissions in 2010 currently projected to be around 
40,000 metric tonnes,
    A. To request Parties to inform industry and users about the 
concerns surrounding the use and emissions of nPB and the potential 
threat that these might pose to the ozone layer;
    B. To request Parties to urge industry and users to consider 
limiting the use of nPB to applications where more economically 
feasible and environmentally friendly alternatives are not 
available, and to urge them also to take care to minimize exposure 
and emissions during use and disposal;
    C. To request the Technology and Economic Assessment Panel to 
report annually on nPB use and emissions.

B. Potential Market for nPB

    There are varying estimates of the total market for nPB. The 
Brominated Solvents Consortium, which consists of producers of nPB, 
estimated in 2001 that approximately 9.2 million pounds of nPB were 
sold worldwide in 2000, with that number expected to rise to 15 million 
pounds in 2002 (Biles, 2001). In contrast, the Technology and Economic 
Assessment Panel (TEAP) of the United Nations Environment Programme 
(UNEP) estimated that the ``most likely'' amount of nPB use in 2010 
would be between 44 million and 132 million pounds worldwide, pending 
the result of toxicity testing and price trends of various solvents 
(UNEP, 2001). EPA believes that the actual market size in 2010 may be 
lower than the 44-132 million pounds cited by the TEAP report. Further, 
since the TEAP report was published, some manufacturers and blenders of 
nPB have withdrawn their products from the market.
    EPA notes that the TEAP report based its estimates of how much nPB 
would be used by assuming that nPB will displace significant amounts of 
chlorinated solvents and HCFCs in the marketplace. The report states, 
``If occupational exposure limits for nPB were 2-4 times higher than 
exposure limits of methylene chloride, nPB would replace a substantial 
portion of methylene chloride solvent use even if nPB had a 
significantly higher price. High rates of market penetration will 
require U.S. EPA SNAP listing, a favorable AEL, and market confidence'' 
(UNEP, 2001). Given that today's proposal recommends an AEL equivalent 
to that for methylene chloride (OSHA PEL) and perchloroethylene (ACGIH 
TLV) and slightly lower than that for trichloroethylene (ACGIH TLV = 50 
ppm, 8 hour TWA), it is likely that the TEAP's estimates for market 
penetration of nPB are too high.
    In addition, we note that producers of HCFC-141b, a solvent with 
slightly lower cost and similar solvency to nPB, never sold more than 
36 million pounds per year as a solvent, even at the height of its 
usage (AFEAS, 2002). HCFC-141b has recently been phased out of 
production in the U.S. and the Agency expects nPB to be only one of 
several alternative solvents that will substitute for it. Further, 
experience with the growth of the market for HCFC-141b suggests that 
the growth in the market for nPB is unlikely to continue at its current 
pace for more than a few years. The most recent information from 
suppliers of nPB indicates that in 2001, sales were approximately 9 
million pounds, similar to the level in 2000 (Biles, 2002).

[[Page 33306]]

C. Estimated Economic Impacts on Businesses

    As part of our rulemaking process, EPA estimated potential economic 
impacts of today's proposed regulation. In our analysis, we assumed 
that capital costs are annualized over 10 years and that the discount 
rate for determining net present value is 7.0%. We found the following 
impacts from the regulatory use condition on the iPB content in nPB 
formulations:
    [sbull] In general, users in the solvent cleaning sector and 
aerosol solvent end use are already using nPB formulations containing 
less than 0.05% iPB by weight, and will experience little or no rise in 
prices. Most of the costs of compliance would fall upon adhesives 
users, since some of them currently use nPB formulations containing as 
much as 1% iPB.
    [sbull] If today's proposed rule were to become final, the cost of 
the regulatory condition to the user community would be in the range of 
$2 to $3 million per year.
    EPA also considered potential costs end users could incur if they 
implemented the recommended acceptable exposure limit. Qualitatively, 
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 today's 
proposal (Ultronix, 2001; Albemarle, 2003). Based on the experience of 
companies that assist their customers in meeting an exposure limit of 
25 ppm for nPB, we assumed that 75% to 90% of nPB users in the non-
aerosol solvent cleaning sector already have exposure levels of 25 ppm 
or less. Of those nPB users with exposure levels above 25 ppm, we 
examined the cost associated with reducing emissions by 50% to 75%. EPA 
also found:
    [sbull] Balancing the savings due to reduced solvent loss and the 
cost of emission controls on vapor degreaser, the range of costs for 
solvent cleaning ranged from a net savings of $83,900 to a cost of 
$2000 per user.
    [sbull] Installing ventilation equipment was a minor expense for 
aerosol solvent users ($124 to $1230 annualized cost per user).
    [sbull] The more extensive ventilation equipment necessary for 
adhesive users was more expensive ($24,000 to $39,000 annualized cost 
per user).
    [sbull] EPA estimated that full implementation of the recommended 
workplace exposure guideline across all nPB users in all three 
industrial sectors would range in cost from a potential net savings up 
to $1.9 million to a cost of $5.5 million dollars per year. The value 
will depend on the number of users that attempt to meet the recommended 
exposure guideline, the initial exposure level of cleaning solvent 
users, the price of nPB, and the amount of emission control equipment 
or ventilation equipment installed. The high end of the range likely 
would be an overestimate of actual impacts because, among other things, 
it does not consider that some users may choose to switch to other 
alternatives.
    [sbull] When the potential costs of compliance with the regulatory 
use condition and implementation of the recommended acceptable exposure 
limit are considered together, EPA found the total cost to range from a 
savings of $0.1 million to a cost of $8.1 million.
    For purposes of comparison with these costs numbers, average values 
of shipments as a proxy for revenues for different types of businesses 
are as follows:

        Table 3.--Examples of nPB Users by NAICS Code or Subsector and Average Annual Value of Shipments
----------------------------------------------------------------------------------------------------------------
                                                                                                 Average annual
                                                                                                    value of
                                                                                               shipments by each
  NAICS code for subsector code       NAICS description            Example Uses of nPB             company in
                                                                                                   subsector
                                                                                                   (million)
----------------------------------------------------------------------------------------------------------------
326150..........................  Urethane and other foam   Carrier solvent in adhesivs to                  10.1
                                   product (except           stick together foam pieces in
                                   polystyrene)              foam fabrication.
                                   manufacturing.
332.............................  Fabricated Metal Product  Metals cleaning to remove oil,                   3.9
                                   Manufacturing.            grease, and wax from metal parts.
333.............................  Machinery Manufacturing.  Metals cleaning to remove oil,                   8.9
                                                             grease, and wax from metal parts.
334.............................  Computer and Electronic   Electronics cleaning, and aerosol               25.2
                                   Product Manufacturing.    solvent use to remove solder
                                                             flux from circuit boards.
336.............................  Transportation Equipment  Aerosol solvent use for cleaning                44.6
                                   Manufacturing.            aerospace equipment; carrier
                                                             solvent in adhesives for
                                                             aircraft seating.
337.............................  Furniture and Related     Carrier solvent in adhesives for                 3.1
                                   Product Manufacturing.    cushions or kitchen countertops;
                                                             metals cleaning to remove grease
                                                             from metal furniture parts.
----------------------------------------------------------------------------------------------------------------

    For more detailed information, see section X.C. below and EPA's 
analysis in the docket (US EPA, 2003).

VI. How is EPA Responding to Comments on the Advance Notice of Proposed 
Rulemaking (ANPRM) and December 18, 2000 Notice of Data Availability?

    EPA received 66 comments on the February 18, 1999, Advance Notice 
of Proposed Rulemaking (64 FR 8043) from 61 commenters. Forty-eight 
commenters advocated listing nPB as an acceptable substitute for CFC-
113 and methyl chloroform under SNAP; ten commenters opposed listing 
nPB as acceptable; and three commenters responded to the information 
requests contained in the ANPRM without taking a position on the 
acceptability of nPB. Close to one-third of the commenters were 
manufacturers of products that require solvent cleaning. Other 
commenters included chemical manufacturers, solvent and lubricant 
distributors, consultants, academicians, adhesive manufacturers, 
product repair companies, vapor degreaser manufacturers, an aerosol 
manufacturer, an adhesive distributor, a machinery distributor, the 
U.S. Army, the U.S. Department of Energy, a solvent

[[Page 33307]]

blender, a printed circuit board repair facility, and a labor union. 
Almost all of the comments focused on the use of nPB in solvent 
cleaning, although the Agency did receive a few comments on the use of 
nPB in adhesives and aerosols applications. No commenter suggested 
using nPB in coatings or inks.
    Many of the commenters described the complex task of searching for 
an optimal substitute for CFC-113 or methyl chloroform. Factors they 
have considered include maintaining superior performance, minimizing 
contamination, maintaining cost-effective and efficient processes, 
complying with local and other national regulatory requirements, 
assuring employee safety, and meeting exacting customer standards. 
These commenters often described their specific experiences using nPB, 
and compared nPB with other solvents and with other cleaning processes 
such as aqueous cleaning. Proponents of nPB listed as its chief 
advantages its lower cost compared to some alternatives (e.g., HFCs, 
HFEs), lack of corrosiveness, potency as a solvent, low conductivity, 
minimal residues, and quick drying time. They also noted its ODP, short 
atmospheric lifetime and low GWP.
    One commenter stated that because of its expense, users may use nPB 
more efficiently than they would use other, less expensive solvents. 
The commenter, a manufacturer of precision electromagnetic relays, 
formerly used about 5,000 pounds of methyl chloroform each year, and 
now uses about 1,500 pounds of nPB. Another commenter noted that nPB's 
bad odor provides users with an incentive to minimize evaporative 
losses. Commenters who oppose listing nPB as an acceptable substitute 
cited its instability, reactivity, and toxicity. Several commenters 
argued that nPB should not be used in solvent cleaning because it is 
largely uncontrolled and relatively little is known about its health 
effects.
    In response to the Agency's December 18, 2000, SNAP notice and 
update on nPB (65 FR 78977), one commenter expressed concern about the 
use of nPB in cleaning and adhesive applications because of data 
showing that nPB is a reproductive toxin. The commenter also noted that 
the chemical sold as nPB contains fairly high quantities of iPB, a 
potent reproductive toxin. In addition, the commenter expressed concern 
that one manufacturer of nPB had recently left the market, and asked 
EPA to seek input on setting the proper exposure level from NIOSH, 
OSHA, and toxicologists who are not from industry or EPA.
    Our proposal today reflects the Agency's agreement with those 
commenters who stated that there are some cleaning operations for which 
only nPB (and presumably, the CFC-113 or methyl chloroform that it 
replaced) meets all of the criteria necessary for the success of those 
operations. However, we also agree that some, but not all, cleaning 
operations that formerly relied on CFC-113 or methyl chloroform can use 
alternative cleaning agents, or alternative processes such as aqueous 
or semi-aqueous cleaning. EPA has discussed the results of the 2-
generation reproductive study (WIL, 2001) and the recommended exposure 
limit with NIOSH as well as outside toxicologists not involved with the 
solvent industry or EPA, as one commenter suggested. We agree that the 
quantity of iPB in nPB is of concern. In response, we are proposing 
today to limit the iPB content in nPB to 0.05% by weight. We also are 
recommending an acceptable exposure limit for nPB of 25 ppm as an 
eight-hour time-weighted average, and recommending that users employ 
controls to minimize worker exposure to nPB to the lowest levels 
reasonably possible. The Agency believes that today's proposed rule 
takes into account environmental and workplace safety concerns 
associated with nPB, and that adhering to the recommended AEL of 25 ppm 
will protect against adverse health effects.

VII. What Should I Include in My Comments on EPA's Proposal?

    In your comments, please explain what you think EPA should do in 
this rulemaking and why you think your suggested approach is 
appropriate. You may find the following suggestions helpful for 
preparing your comments:
    1. Explain your views as clearly as possible.
    2. Describe any assumptions that you used.
    3. Provide any technical information and/or data you used that 
support your views.
    4. If you estimate potential burden or costs, explain how you 
arrived at your estimate.
    5. Provide specific examples to illustrate your concerns.
    6. Offer alternatives.
    7. Make sure to submit your comments by the comment period deadline 
identified.
    8. To ensure proper receipt by EPA, identify the appropriate docket 
identification number, OAR-2002-0064 in the subject line on the first 
page of your response. It would also be helpful if you provided the 
name, date, and Federal Register citation related to your comments.
    EPA invites comment on all aspects of today's proposed rule. A 
number of specific issues are raised throughout the SUPPLEMENTARY 
INFORMATION section of today's preamble. We request your comments on 
the following issues in particular:
    (1) Is it appropriate for EPA to find nPB acceptable for use in the 
solvents metals, electronics and precision cleaning, aerosol solvents, 
and adhesives, coatings, and inks sectors? Why or why not? Should EPA 
have different decisions for different sectors or end uses? In 
particular, given that the CERHR Expert Panel expressed concern about 
``poorly controlled spray adhesive applications,'' should EPA find nPB 
acceptable, subject to use conditions, for use in spray adhesives? 
Should the Agency find nPB acceptable, subject to use conditions, for 
use in aerosol solvents, or should nPB's use be limited to certain 
applications in this end use? (See section III of today's notice and 
CERHR, 2002a, p. 50.)
    (2) What is an appropriate and achievable limit on the content of 
isopropyl bromide (iPB) in unstabilized nPB? Should this impurity limit 
be 0.1%, 0.05%, or 0.025% iPB by weight? Why? How much does each of 
these purity levels add to the cost of cleaning solvents or adhesives 
made using nPB, in terms of $/drum and as a percentage of the current 
cost? (See section IV.A.4. of today's notice.)
    (3) What is an appropriate acceptable exposure limit for EPA to 
recommend, and why? If you disagree with the proposed recommended 
exposure limit of 25 ppm, why do you disagree? Should EPA consider risk 
management principles in developing a recommended AEL? Please cite 
specific points of concern (e.g., studies considered, endpoints 
considered in BMD analysis, uncertainty factors applied). (See sections 
IV.A.1.a through d. of today's notice.)
    (4) Should nPB be listed acceptable with a skin notation? (See 
section IV.A.1.b of today's notice.)
    EPA also invites commenters to submit any new, relevant data 
pertaining to nPB and iPB beyond what is discussed in today's notice. 
Under EPA guidelines, there is a preference for peer reviewed data 
because of the potential to improve the quality and credibility of the 
product. Peer-reviewed data are studies/analyses that have been 
reviewed by qualified individuals (or organizations) who are 
independent of those who performed the work, but who are collectively 
equivalent in technical expertise (i.e., peers) to those who

[[Page 33308]]

performed the original work. A peer review is an in-depth assessment of 
the assumptions, calculations, extrapolations, alternate 
interpretations, methodology, acceptance criteria, and conclusions 
pertaining to the specific major scientific and/or technical work 
products and of the documentation that supports them (US EPA, 2000b).
    To ensure that we have time to consider your comments, please 
submit them to EPA's Air Docket by the date in the DATES section at the 
beginning of this document. You may submit them via e-mail to [email protected]. Comments may be submitted electronically, by mail, by 
facsimile, or through hand delivery/courier. Follow the detailed 
instructions provided in sections I.B through I.D. To give us more time 
to consider your comments, please also send a copy via e-mail to our 
staff directly at [email protected]. EPA's responses to 
comments, whether the comments are written or electronic, will be in a 
final rule published in the Federal Register or in a response-to-
comments document placed in the rulemaking docket. We will not reply to 
respondents electronically other than to seek clarification of 
electronic comments that may be disrupted in transmission or during 
conversion to paper form.

VIII. What Is the Federal Government Doing To Help Businesses Use nPB 
Safely?

    EPA is concerned that careless use of nPB will place those exposed 
at risk of serious adverse health effects. We are also concerned that 
some users perceive nPB as a ``path of less resistance'' because it has 
similar properties to methyl chloroform, but, unlike methyl chloroform, 
OSHA has not issued a permissible exposure limit (PEL) for nPB. In 
particular, the adhesives industry widely used methyl chloroform and 
then methylene chloride as carrier solvents. Since the introduction of 
OSHA workplace regulations for methylene chloride, some companies 
appear to prefer nPB-based adhesives because nPB is not yet regulated, 
and because nPB is not flammable under normal conditions. Because of 
these concerns, EPA is working with NIOSH to develop outreach materials 
to share with facilities that use, or could use, nPB to inform them of 
good workplace practices.
    Further, EPA recommends that users contact OSHA's consultation 
service. OSHA funds confidential consultation services to users through 
state government staff. Employers can find out about potential hazards 
at their worksites, improve their occupational safety and health 
management systems, and even qualify for a one-year exemption from 
routine OSHA inspections. The consultation service is separate from 
inspections and enforcement. To request a consultation, telephone or 
write to the appropriate state consultation service, listed on the web 
at http://www.osha.gov/oshdir/consult.html. For example, if you have a 
facility in North Carolina, call the North Carolina Department of Labor 
at (919) 807-2899. See OSHA's web site at http://www.osha.gov/html/consultation.html for further information on consultation services.

IX. How Can I Use nPB as Safely as Possible?

    As discussed above in section IV.A.1.e, EPA believes that the AEL 
of 25 ppm can be met in all the industrial sectors being reviewed 
today, including solvent cleaning applications, adhesives applications, 
and aerosol solvents applications, as long as appropriate controls are 
put in place. However, EPA also realizes that this exposure guideline 
is relatively low and that in many cases, users will have to implement 
additional emissions control measures to reach this level. Below are 
actions that will help nPB users meet the exposure guideline 
recommended in today's proposed rule:
    [sbull] All users of nPB should wear appropriate personal 
protective equipment, including chemical goggles, flexible laminate 
protective gloves 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.
    [sbull] Follow guidelines in the National Emission Standard for 
Hazardous Air Pollutants (NESHAP) for halogenated solvents cleaning if 
you are using nPB for non-aerosol solvent cleaning. 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.
    [sbull] Use the employee exposure monitoring programs and product 
stewardship programs where offered by manufacturers and formulators of 
nPB-based solvents and adhesives.
    [sbull] Follow all recommended safety precautions specified in the 
manufacturer's Material Safety Data Sheets (MSDSs).
    [sbull] Use sufficient ventilation and emissions controls to meet 
the 25 ppm AEL in adhesives or aerosol applications (or, once 
developed, the applicable OSHA PEL). Examples of ventilation equipment 
for aerosol uses include ventilation hoods and fans. Adhesive appliers 
can use spray booths, ventilation hoods or ducts, and fans to reduce 
exposure.
    [sbull] Request a confidential consultation from your State 
government. 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.
    [sbull] 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.
    [sbull] A medical monitoring program should be established for the 
early detection and prevention of acute and chronic effects of exposure 
to nPB. The workers' physician(s) should be given information about the 
adverse health effects of exposure to nPB and the workers' potential 
for exposure.
    [sbull] Workers should receive safety training and education that 
includes potential health effects of exposure to nPB, covering 
information included on the appropriate material data safety sheets, as 
required by OSHA's Hazard Communication Standard (29 CFR 1910.1200).
    We note that these steps are useful for reducing exposure to any 
industrial solvent, and not just nPB.

X. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review

    Under Executive Order 12866, (58 FR 51735; October 4, 1993) the 
Agency must determine whether the regulatory action is ``significant'' 
and therefore subject to the Office of Management and Budget (OMB) 
review and the requirements of the Executive Order. The Order defines 
``significant regulatory action'' as one that is likely to result in a 
rule that may: (1) Have an annual effect on the economy of $100 million 
or more or adversely affect in a material way the economy, a sector of 
the economy, productivity, competition, jobs, the environment, public 
health or safety, or State, local, or tribal

[[Page 33309]]

governments or communities; (2) create a serious inconsistency or 
otherwise interfere with an action taken or planned by another agency; 
(3) materially alter the budgetary impact of entitlement, grants, user 
fees, or loan programs or the rights and obligations of recipients 
thereof; or (4) raise novel legal or policy issues arising out of legal 
mandates, the President's priorities, or the principles set forth in 
the Executive Order.
    Pursuant to the terms of Executive Order 12866, OMB notified EPA 
that it considers this action a ``significant regulatory action'' 
within the meaning of the Executive Order, and EPA submitted this 
action to OMB for review. Changes made in response to OMB suggestions 
or recommendations have been documented in the public record.

B. Paperwork Reduction Act

    This action does not impose any new information collection burden. 
Today's proposal is an Agency determination. It contains no new 
requirements for reporting. The only new recordkeeping requirement 
involves customary business practice. The Office of Management and 
Budget (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 numbers 2060-0226 (EPA 
ICR No. 1596.05). This ICR included five types of respondent reporting 
and record-keeping activities pursuant to SNAP regulations: submission 
of a SNAP petition, filing a SNAP/TSCA Addendum, notification for test 
marketing activity, record-keeping for substitutes acceptable subject 
to use restrictions, and record-keeping for small volume uses. Today's 
proposed rule, if finalized, would require minimal record-keeping for 
two years from the date of creation of the record to demonstrate that 
the nPB contains no more than 0.05% iPB. Because it is customary 
business practice that chemical companies provide certificates of 
analysis to their customers, we believe this requirement will not 
impose an additional paperwork burden.
    Copies of the ICR document(s) may be obtained from Sandy Farmer, by 
mail at the Office of Environmental Information, Collection Strategies 
Division; U.S. Environmental Protection Agency (2822); 1200 
Pennsylvania Ave., NW., Washington, DC 20460, by e-mail at 
[email protected], or by calling (202) 566-1676. A copy may also be 
downloaded off the Internet at http://www.epa.gov/icr. Include the ICR 
and/or OMB number in any correspondence.
    Burden means the total time, effort, or financial resources 
expended by persons to generate, maintain, retain, or disclose or 
provide information to or for a Federal agency. This includes the time 
needed to review instructions; develop, acquire, install, and utilize 
technology and systems for the purposes of collecting, validating, and 
verifying information, processing and maintaining information, and 
disclosing and providing information; adjust the existing ways to 
comply with any previously applicable instructions and requirements; 
train personnel to be able to respond to a collection of information; 
search data sources; complete and review the collection of information; 
and transmit or otherwise disclose the information.
    An Agency may not conduct or sponsor, and a person is not required 
to respond to, a collection of information unless it displays a 
currently valid OMB control number. The OMB control numbers for EPA's 
regulations are listed in 40 CFR part 9 and 48 CFR chapter 15.

C. Regulatory Flexibility Act (RFA)

    The RFA generally requires an agency to prepare a regulatory 
flexibility analysis of any rule subject to notice and comment 
rulemaking requirements under the Administrative Procedure Act or any 
other statute unless the agency certifies that the rule will not have a 
significant economic impact on a substantial number of small entities. 
Small entities include small businesses, small organizations, and small 
governmental jurisdictions. For purposes of assessing the impacts of 
today's rule on small entities, small entity is defined as: (1) A small 
business that has fewer than 500 employees; (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. EPA 
has consulted with the Small Business Administration's Office of 
Advocacy on the alternate small business definition of 500 employees. 
For today's rule, we chose to use 500 employees, rather than use the 
individual size standards for the numerous NAICS subsectors and codes 
to simplify the economic analysis. Furthermore, this size standard was 
set by SBA for all NAICS codes for businesses using nPB-based 
adhesives, which is the end use that could experience the greatest cost 
impacts under today's rule. We solicit comments on the choice of this 
alternate definition for this analysis.
    After considering the economic impacts of today's proposed rule on 
small entities, I certify that this action will not have a significant 
economic impact on a substantial number of small entities.
    Types of businesses that would be subject to today's proposed rule, 
if it became final, would include:
    [sbull] Manufacturers of computers and electronic equipment that 
clean with nPB cleaning solvents (NAICS subsector 334).
    [sbull] Manufacturers of fabricated metal parts, including plating, 
ball and roller bearings, machined parts, and other metal parts that 
require oil and grease to be cleaned off (NAICS subsectors 332 and 
333).
    [sbull] Manufacturers of transportation equipment, such as 
aerospace equipment that requires cleaning either in a tank or with 
aerosols, and aircraft seating, which is assembled using adhesives 
containing nPB as a carrier solvent (NAICS subsector 336).
    [sbull] Manufacturers of furniture, including various kinds of 
furniture with cushions and countertops assembled using adhesives 
containing nPB as a carrier solvent (NAICS subsector 337).
    [sbull] Foam fabricators, who assemble foam cushions using 
adhesives containing nPB as a carrier solvent (NAICS code 326150).
    EPA estimates that up to 7330 small industrial end users currently 
use nPB and thus could be subject to this rule. This number includes 
approximately 500 to 2300 users of nPB industrial cleaning solvents 
(e.g., cleaning with vapor degreasers), 900 to 4750 users of nPB-based 
aerosol solvents, and 40 to 280 users of nPB-based adhesives.
    In order to consider the resources that affected small businesses 
have available to operate and to respond to regulatory requirements, 
EPA compared the cost of meeting regulatory requirements to small 
businesses' annual sales. In our analysis for today's proposal, we used 
the average value of shipments for the products manufactured by the end 
user as a proxy for sales or revenues, since these data are readily 
available from the U.S. Department of Commerce. The following tables 
display the average value of shipments for different sizes of business 
and different NAICS subsectors or codes in the affected industrial 
sectors. EPA then used data from these sources to determine the 
potential economic impacts on small businesses of today's proposed 
rule.

[[Page 33310]]



Table 4.--Average Value of Shipments in NAICS Subsectors Performing Solvent Cleaning \1\, by Number of Employees
                                                   at Business
----------------------------------------------------------------------------------------------------------------
                                        Average value of shipments per company ($) by NAICS subsector code
                                 -------------------------------------------------------------------------------
 Number of employees at business       332,                        334, Computer       336,       337, Furniture
                                    Fabricated    333, Machinery  and electronic  Transportation    and related
                                  metal products                     products        equipment       products
----------------------------------------------------------------------------------------------------------------
1-4.............................         174,832         230,806         279,683           d \2\         141,654
5-9.............................           d \2\         766,045         903,756           d \2\         501,193
10-19...........................       1,393,019           d \2\       1,925,077       1,897,347       1,102,104
20-49...........................       3,596,222           d \2\       4,270,554       4,190,678       2,744,633
50-99...........................       9,283,654      10,429,360      10,440,847      10,140,871       6,908,332
100-249.........................      24,566,631      25,781,244           d \2\      27,861,502      17,898,851
250-499.........................      55,392,738      64,822,617           d \2\      69,529,351           d \2\
                                 -----------------
Average--All Small Businesses in     3.2 million     4.2 million     2.4 million     8.9 million     1.7 million
 Subsector......................
                                 -----------------
Average--All Businesses in           3.9 million     8.9 million    25.2 million    44.6 million    3.1 million
 Subsector......................
----------------------------------------------------------------------------------------------------------------
\1\ Aerosol solvents are used in NAICS subsectors 334 and 336. Non-aerosol solvents are used in all five NAICS
  subsectors.
\2\ ``d'' designates ``Data withheld to avoid disclosing data of individual companies; data are included in
  higher level totals.'' The average value of shipments for small businesses does not include those values
  marked with ``d,'' and thus may be overestimated or underestimated.


 Table 5.--Average Value of Shipments in NAICS Categories Using nPB as a Carrier Solvent in Adhesives, by Number
                                            of Employees at Business
----------------------------------------------------------------------------------------------------------------
                                          Average Value of Shipments per Small Company ($) by NAICS Code
                                 -------------------------------------------------------------------------------
                                                                      326150,
                                      337121,      337110, Wood    Urethane and    336360, Motor
 Number of employees at business    Upholstered       kitchen       other foam        vehicle      337124, Metal
                                     household      cabinet and      products       seating and      household
                                     furniture     counter tops       (except      interior trim     furniture
                                                                   polystyrene)
----------------------------------------------------------------------------------------------------------------
1-4.............................         135,545         135,046         287,744         174,500         170,820
5-9.............................         428,646         457,310       1,211,200         532,875         582,725
10-19...........................         913,225       1,015,967       2,537,028       2,490,455       1,299,671
20-49...........................       2,582,340       2,326,857       5,892,653       3,901,979       3,730,479
50-99...........................       5,680,148       5,655,585      11,608,984       8,981,786       7,522,129
100-249.........................      14,832,151      16,139,988      26,480,552      44,153,730      16,911,474
250-499.........................               d      47,943,433      59,104,111     100,579,000      33,330,714
                                 -----------------
Average--All Small Businesses in     3.3 million     0.9 million     9.4 million    18.3 million     4.1 million
 NAICS Code.....................
                                 -----------------
Average--All Businesses in NAICS     4.9 million     1.1 million    10.1 million    29.1 million     6.0 million
 Code...........................
----------------------------------------------------------------------------------------------------------------

    Today's proposed rule would require that users use nPB that 
contains no more than 0.05% iPB by weight. Most chemical manufacturers 
and solvent formulators already make products that meet this 
requirement. Some users of adhesives containing nPB use formulations 
that do not meet the proposed limit on iPB content. These users may 
need to purchase a more expensive grade of nPB-based adhesives that 
contains less iPB. Many users of adhesives containing nPB are small 
businesses that fabricate foam to be used in cushions for furniture.
    If the requirements of today's proposed rule were to be finalized, 
we estimate that between 0 and 13 small businesses using nPB-based 
adhesives, or less than 5% of the 280 or so small businesses that use 
nPB-based adhesives, would experience a cost increase (i.e., an impact) 
of greater than 1.0% of annual sales. Because solvent and aerosol 
solvent formulations of nPB already contain less than 0.05% iPB by 
weight, there were no impacts on end users in the non-aerosol solvent 
cleaning sector and aerosol solvents end use; only the 0 to 13 adhesive 
end users experienced a significant impact. An even smaller percentage 
of all 7330 or so small businesses choosing to use nPB would experience 
an impact of greater than 1.0% of annual sales. In addition, we 
estimate that no small businesses would experience an impact of greater 
than 3.0% of annual sales. We conclude that no small business subject 
to today's rule would go out of business as a result of the rule's 
requirements, if they were to become final. Because of the small total 
number and small percentage of affected businesses that would 
experience an impact of greater than either 1.0% or 3.0% of annual 
sales, EPA does not consider this rule to have a significant impact on 
a substantial number of small businesses.
    The recommended acceptable exposure limit is only a recommendation 
and not an enforceable requirement of today's rule, and thus, EPA is 
not required to analyze the cost associated with implementing the 
recommended exposure limit. Nevertheless, the Agency did analyze the 
cost impacts of the combination of implementing the exposure limit and 
complying with the regulatory use condition in order to provide 
additional information about potential effects on small businesses. We 
found that, when the costs to comply with the regulatory use condition 
and to implement the recommended acceptable exposure limit are 
considered together, at most 47 small businesses choosing to use nPB 
would experience an impact of greater

[[Page 33311]]

than 1.0% of annual sales, and none would experience an impact of 
greater than 3.0% of annual sales. All of the small businesses that 
would experience significant impacts are users of nPB-based adhesives. 
Thus, slightly less than 17% of the 280 or so small businesses choosing 
to use nPB-based adhesives would experience significant impacts, and 
less than 1% of all 7330 or so small businesses choosing to use nPB 
would experience significant impacts. Based on the relatively small 
number and percentage of small businesses that would experience 
significant impacts, EPA concludes that even if costs of implementing 
the recommended exposure limit were considered together with costs of 
complying with the regulatory use condition, today's rule would not 
have a significant impact on a substantial number of small entities.
    Although this proposed rule will not have a significant economic 
impact on a substantial number of small entities, EPA nonetheless has 
tried to reduce the impact of this rule on small entities. Before 
selecting the regulatory options proposed today, we considered a number 
of regulatory options that would have had greater impacts on small 
businesses, such as:
    [sbull] Finding nPB unacceptable for use in adhesives. This 
approach would require hundreds of small businesses to use other types 
of adhesives, with no option to improve ventilation to reduce worker 
exposure. Although small businesses could potentially save money by 
using a less expensive adhesive, such as a flammable adhesive, the 
capital costs of fire-proofing currently discourage small businesses 
from using inexpensive flammable adhesives. In addition, requirements 
of the Federal Aviation Administration for aircraft seating cushions 
effectively require either using nPB-based or methylene chloride-based 
adhesive or receiving a special waiver from the Administration. Recent 
regulations for hazardous air pollutants disallow use of methylene 
chloride in foam fabrication facilities. Thus, it is useful for 
adhesive users to have the option of nPB-based adhesives.
    [sbull] Placing a narrowed use limit on the use of nPB in adhesives 
that would allow its use only in those cases where alternatives are 
technically infeasible due to performance or safety issues.
    [sbull] Requiring that users clean metal, electronics, or other 
parts with nPB in vapor degreasing equipment that meets the 
requirements of the national emission standards for halogenated solvent 
cleaning.
    In developing our regulatory options, we considered information we 
learned from contacting small businesses using or selling nPB. EPA 
staff visited the site of a small business using nPB for cleaning 
electronics. We contacted several fabricators of foam cushions that 
have used adhesives containing nPB. We participated in meetings with a 
number of adhesive manufacturers and users of adhesives in furniture 
construction. We have developed a fact sheet and have updated our 
program web site to inform small businesses about this proposed rule 
and to request their comments. We continue to be interested in the 
potential impacts of the proposed rule on small entities and request 
comments on issues related to such impacts.

D. Unfunded Mandates Reform Act

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

E. Executive Order 13132: Federalism

    Executive Order 13132, entitled ``Federalism'' (64 FR 43255, August 
10, 1999), requires EPA to develop an accountable process to ensure 
``meaningful and timely input by State and local officials in the 
development of regulatory policies that have federalism implications.'' 
``Policies that have federalism implications'' is defined in the 
Executive Order to include regulations that have ``substantial direct 
effects on the States, on the relationship between the national 
government and the States, or on the distribution of power and 
responsibilities among the various levels of government.''
    This proposed rule does not have federalism implications. It will 
not have substantial direct effects on the States, on the relationship 
between the national government and the States, or on the distribution 
of power and responsibilities among the various levels of government, 
as specified in Executive Order 13132. This regulation applies directly 
to facilities that use these substances and not to governmental 
entities. Thus, Executive Order 13132 does not apply to this rule.

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

    Executive Order 13175, entitled ``Consultation and Coordination 
with Indian Tribal Governments'' (65 FR 67249, November 6, 2000), 
requires EPA to develop an accountable process to ensure ``meaningful 
and timely input by tribal officials in the development of regulatory 
policies that have tribal implications.'' ``Policies that have tribal

[[Page 33312]]

implications'' is defined in the Executive Order to include regulations 
that have ``substantial direct effects on one or more Indian tribes, on 
the relationship between the Federal government and the Indian tribes, 
or on the distribution of power and responsibilities between the 
Federal government and Indian tribes.''
    This proposed rule does not have tribal implications. It will not 
have substantial direct effects on tribal governments, on the 
relationship between the Federal government and Indian tribes, or on 
the distribution of power and responsibilities between the Federal 
government and Indian tribes, as specified in Executive Order 13175.
    Today's proposed rule does not significantly or uniquely affect the 
communities of Indian tribal governments, because this regulation 
applies directly to facilities that use these substances and not to 
governmental entities. Thus, Executive Order 13175 does not apply to 
this proposed rule.

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

    Executive Order 13045: ``Protection of Children from Environmental 
Health Risks and Safety Risks'' (62 FR 19885, April 23, 1997) applies 
to any rule that: (1) Is determined to be ``economically significant'' 
as defined under Executive Order 12866, and (2) concerns an 
environmental health or safety risk that EPA has reason to believe may 
have a disproportionate effect on children. If the regulatory action 
meets both criteria, the Agency must evaluate the environmental health 
or safety effects of the planned rule on children, and explain why the 
planned regulation is preferable to other potentially effective and 
reasonably feasible alternatives considered by the Agency.
    This proposed rule is not subject to the Executive Order because it 
is not economically significant as defined in Executive Order 12866, 
and because the Agency does not have reason to believe the 
environmental health or safety risks addressed by this action present a 
disproportionate risk to children. The exposure limits and 
acceptability listings in this proposed rule apply to the workplace. 
These are areas where we expect adults are more likely to be present 
than children, and thus, the agents do not put children at risk 
disproportionately.
    Further, today's proposed rule provides both regulatory 
restrictions and recommended exposure guidelines based upon 
toxicological studies in order to reduce risk of exposure to 
reproductive toxins, both iPB and nPB. This rule is not subject to 
Executive Order 13045 because it is not economically significant as 
defined in Executive Order 12866 and because the Agency does not have 
reason to believe the environmental health or safety risks addressed by 
this action present a disproportionate risk to children. The public is 
invited to submit or identify peer-reviewed studies and data, of which 
the agency may not be aware, that assessed results of early life 
exposure to nPB or iPB.

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

    This proposed 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 
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 
proposed rulemaking involves technical standards since EPA is proposing 
to limit the amount of iPB as a contaminant of nPB formulations to 
0.05%, which is lower than the 0.1% limit set by the ASTM standard for 
vapor degreasing grade and general grade nPB. Based on the relatively 
potent toxicity of iPB (see discussion in section IV.A.4 of the 
preamble), EPA believes it is prudent to reduce the level of iPB to 
0.05% to protect worker health. EPA has consulted with producers and 
formulators of nPB products, and all have stated that an iPB limit of 
0.05% is achievable. EPA requests comment on this aspect of the 
proposed rulemaking and, specifically, invites the public to comment on 
the level of iPB contamination that EPA should set, and to explain why 
such limits should be set in this regulation.

XI. 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 in hard copy in docket number A-2001-07 (legacy 
docket number for Docket ID No. OAR-2002-0064). Numbers listed after 
the reference indicate the item number within the docket.

Flammability

UNEP, 1999. 1998 Report of the United Nations Environment Programme 
Ozone Secretariat, Solvents, Coatings and Adhesives Technical Options 
Committee, April, 1999. (II-A-22)

Ozone-Depletion Potential and Global Warming Potential

Atmospheric and Environmental Research, Inc., 1995: Estimates of the 
Atmospheric Lifetime, Global Warming Potential and Ozone Depletion 
Potential of n-Propyl Bromide. Independent study prepared for Albemarle 
Corporation. (II-D-17)
WMO (World Meteorological Organization), 1999: Scientific Assessment of 
Ozone Depletion: 1998, Global Ozone Research and Monitoring Project--
Report No. 44, Geneva, 1998. (II-A-20)
Wuebbles, D. J., R. Kotamarthi, and K. O. Patten, 1999: ``Updated 
evaluation of Ozone Depletion Potentials for Chlorobromomethane and 1-
bromo-propane.'' Atmospheric Environment, Vol. 33, p. 1641-1643. (A-91-
42, IX-A-62)
Wuebbles, D. J., K. O. Patten, and M. T. Johnson, 2000: ``Effects of n-
propyl bromide and other short-lived chemicals on stratospheric 
ozone.'' Proceedings, Symposium on Atmospheric Chemistry Issues in the 
21st Century, American Meteorological Society, Boston. (II-A-4)
Wuebbles, Donald J., Patten, Kenneth O., Johnson, Matthew T., 
Kotamarthi, Rao, 2001: ``New methodology for Ozone Depletion Potentials 
of short-lived compounds: n-propyl bromide as an example.'' Journal of

[[Page 33313]]

Geophysical Research, Vol. 106, No. D13, p. 14,551. (II-A-3)
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. (II-
D-29)

Toxicity

Albemarle, 1997. Attachment 5 to August 7, 1997 submission to EPA, Air 
Monitoring Data. (Docket A-91-42, item VI-D-114)
Albemarle, 2001. November 16, 2001 e-mail from Mick Kassem, Albemarle 
Corporation, concerning exposure levels using nPB in various 
applications. (II-A-19)
Amity UK Ltd, 2001. Amity Product Information Bulletin Sheet Ref. No. 
00-003: Vapor Degreasing Good Practice. 5 June 2001. (II-A-18)
Barber E.D., Donish W., Mueller K. 1981. A procedure for the 
quantitative measurement of the mutagenicity of volatile liquids in the 
Ames Salmonella/microsome assay. Mutat Res 90:31-48. (II-A-9)
Barber E., Donish W. 1982. An exposure system for quantitative 
measurements of the microbial mutagenicity of volatile liquids in 
genotoxic effects of airborne agents. Environ Sci Res 25:3-18. (II-A-
29)
Brock, W. 2002. Letter to Jeff Cohen, EPA re: Comments on Acceptable 
Exposure Limit Derivation for n-Propyl Bromide (II-D-57)
Biles, 2002. Personal communication between Jeff Cohen, EPA and Blake 
Biles, Arnold & Porter, counsel to the Brominated Solvents Consortium 
(II-B-18)
CCPCT (The Center for Clean Products and Clean Technologies) August 
2001. Alternative Adhesive Technologies in the Foam Furniture and 
Bedding Industries: A Cleaner Technologies Substitutes Assessment. 
Volume 2: Risk Screening and Comparison. The University of Tennessee 
Center for Clean Products and Clean Technologies. (II-D-70)
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. (II-A-11)
CERHR, 2002b. NTP-Center for the Evaluation of Risks to Human 
Reproduction Expert Panel Report on the Reproductive and Developmental 
Toxicity of 2-Bromopropane [iPB]. March 2002. (II-A-12)
Charm, 2001. Letter to Dov Shellef, President, Poly Systems USA, Inc. 
from Joel Charm CIH, Charm HS&E International Inc. re: n-Propyl Bromide 
(II-D-16).
ClinTrials, 1997a. A 28-Day Inhalation Study of a Vapor-Formulation 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)
Crump, K.S. 1984. A new method for determining allowable daily intakes. 
Fundam. Appl. Toxicol. 4:854-871. (II-A-30)
Dodd, D. 2002. Letter to Jeff Cohen, EPA re: Comments on Acceptable 
Exposure Limit Derivation for n-Propyl Bromide (II-D-56)
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)
Fiala ES, Sodum RS, Hussain NS, Rivenson A, Dolan L. 1995. Secondary 
nitroalkanes: induction of DNA repair in rat hepatocytes, activation by 
aryl sulfotransferase and hepatocarcinogenicity of 2-nitrobutane and 3-
nitropentane in male F344 rats. Toxicology May 5; 99(1-2):89-97. (A-91-
42, X-A-16)
Griffin, E., Wilson D. Disorders of the Testes. In: Isselbacher K, 
Baunwald E, Wilson J, Martin B., et al. eds. Harrison's Principles of 
Internal Medicine. 13th ed. New York, McGraw Hill; 1994: 2006-2017. 
(II-A-35)
HESIS, 2002. Comments on ICF's proposed AEL for 1-Bromopropane from Dr. 
Julia Quint, California Department of Health Services, Hazard 
Evaluation System & Information Service (II-D-62)
Huntingdon Life Sciences, August 23, 2001. A Developmental Toxicity 
Study in Rat Via Whole Body Inhalation Exposure. (II-D-27)
HSIA (Halogenated Solvents Industry Alliance), 2001. Minutes of EPA 
meeting with Halogenated Solvents Industry Alliance, 10/17/2001. (II-B-
6)
IARC (International Agency for Research on Cancer), 1992. Monographs on 
the Evaluation of the Carcinogenic Risk of Chemicals to Humans: Some 
Industrial Chemicals and Dyestuffs, Vol. 29, pages 331-343. (II-A-34)
ICF, Inc., 2001. ``Brief Discussion of the BMD Approach: Overview of 
its Purpose, Methods, Advantages, and Disadvantages.'' Prepared for 
U.S. EPA. (II-A-52)
ICF, Inc., 2002a. ``Risk Screen for Use of N Propyl Bromide.'' Prepared 
for U.S. EPA, May, 2002. (II-A-13)
ICF, Inc. 2002c. ``Response to California HESIS comments on AEL for 
nPB'' (II-A-55)
Ichihara G., Asaeda N., Kumazawa T., et al. 1997. Testicular and 
hematopoietic toxicity of 2-bromopropane, a substitute for ozone layer-
depleting chlorofluorocarbons. J Occup Health 39:57-63. (A-91-42, X-A-
32)
Ichihara M., Takeuchi Y., Shibata E., Kitoh J., et al. 1998. 
Neurotoxicity of 1-Bromopropane. Translated by Albemarle Corporation. 
(A-91-42, X-A-33)
Ichihara G., Jong X., Onizuka J., et al. 1999. Histopathological 
changes of nervous system and reproductive organ and blood biochemical 
findings in rats exposed to 1-bromopropane. (Abstract only) Abstracts 
of the 72nd Annual Meeting of Japan Society for Occupational Health. 
May 1999. Tokyo. (II-A-15)
Ichihara G., Yu X., Kitoh J., et al. 2000a. Reproductive toxicity of 1-
bromopropane, a newly introduced alternative to ozone layer depleting 
solvents, in male rats. Toxicol Sciences 54:416-423. (II-A-7)
Ichihara G., Kitoh J., Yu, X., et al. 2000b. 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. (II-A-8)
Ichihara G. et al., 2002a. Neurological Disorders in Three Workers 
Exposed to 1-Bromopropane. J Occu. Health 44:1-7. (II-D-64)
Ichihara G. et al., 2002b. Poster presentation titled: ``Neurological 
abnormality in workers of 1-bromopropane factory,'' Presented at the 
Society of Toxicology Meeting, Wednesday, March 20, 2002. Poster 
ID:1236. (II-D-35)
Kamijima M., Ichihara G., Kitoh J., et al. 1997a. Disruption in ovarian 
cyclicity due to 2-bromopropane in the rat. J Occu. Health 39:3-4. (A-
91-42, X-A-35)
Kamijima M., Ichihara G., Kitoh J. et al. 1997b. Disruption in ovarian 
cyclicity due to 2-bromopropane in the rat. J

[[Page 33314]]

Occu. Health 39:3-4. (A-91-42, X-A-35)
Kamijima M., Ichihara G., Kitoh J., et al. 1997b. Ovarian toxicity of 
2-bromopropane in the nonpregnant female rat. J Occu. Health 39:144-
149. (A-91-42, X-A-36)
Kim Y., Jung K., Hwang T., Jung G., Kim H., Park J., Kim J., Park J., 
Park D., Park S., Choi K., Moon Y. 1996. Hematopoietic and reproductive 
hazards of Korean electronic workers exposed to solvents containing 2-
bromopropane. Scand J Work Environ Health 22:387-391. (A-91-42, X-A-39)
Kim H.-Y., Chung Y.-H., Jeong J.-H., Lee Y.-M., Sur G.-S., Kang J.-K. 
1999. Acute and repeated inhalation toxicity of 1-bromopropane in SD 
rats. J Occup Health 41:121-128. (II-D-23)
Kimmel, C. and Gaylor, D. 1988. Issue in qualitative and quantitative 
risk analysis for developmental toxicology. Risk Anal 8:15-21. (II-A-
28)
Kleinfelter, G. and Darney, S. 2002. Memorandum from EPA's Office of 
Research and Development, Reproductive Toxicology Division, to J. 
Cohen, Office of Air and Radiation, Comments on Acceptable Exposure 
Limit for n-Propyl Bromide (II-C-1)
Maeng S.H., Yu I.J. 1997. Mutagenicity of 2-bromopropane. Ind Health 
35:87-95. (A-91-42, X-A-47)
NIOSH, 1999. U.S. Dept. of Health and Human Services, Letter to Custom 
Products Inc., December 1, 1999. Re: results of Dec. 1998 survey of 
workplace exposure to nPB at Custom Products. (HHE Report 98-0153) (II-
D-6)
NIOSH, 2000a. U.S. Dept. of Health and Human Services, Letter to Marx 
Industries, Inc., February 1, 2000. Re: results of nPB exposure 
assessment survey conducted Nov. 16-17, 1999. (II-D-7)
NIOSH, 2000b. NIOSH Health Hazard Evaluation Report of nPB exposure 
from cold vapor degreasers at Trilithic, Inc. (HHE Report 2000-0233-
2845) (II-D-11)
NIOSH, 2000c. U.S. Dept. of Health and Human Services, Letter to Custom 
Products Inc., December 21, 2000. Re: results of nPB exposure 
assessment survey conducted Nov. 16, 2000. (HHE Report 98-0153) (II-D-
8)
NIOSH, 2001. U.S. Dept. of Health and Human Services, Letter to STN 
Cushion Company, March 7, 2001. Re: Results of nPB exposure assessment 
survey conducted November 14, 2000. (II-D-9)
NIOSH, 2002. NIOSH Health Hazard Evaluation Report of nPB exposure from 
spray adhesives at STN Cushion Company. August, 2002. (HHE Report 2000-
0410-2891) (II-A-31)
NIOSH, 2003. Comments of the National Institute for Occupational Safety 
and Health of the draft Environmental Protection Agency Federal 
Register Notice Protection of Stratospheric Ozone: Listing of 
Substitutes for Ozone-Depleting Substances--n-Propyl Bromide (III-C-6)
Park, Jung-Sun et. al. 1997. ``An Outbreak of Hematopoietic and 
Reproductive Disorders Due to Solvents Containing 2-Bromopropane in an 
Electronic Factory, South Korea: Epidemiological Survey.'' J Occu. 
Health 1997; 39: 138-143. (II-A-1)
Purvis K., Christiansen E., 1992, Male infertility: current concepts. 
Ann Med 1992; 24:258-272. (II-A-36)
Rozman K. and Doull J., 2002. ``Derivation of an Occupational Exposure 
Limit for n-Propyl Bromide Using an Improved Methodology'' App Occu. 
Env. Hyg. 17: 711-716 (II-D-63)
Saito-Suzuki R., Teramoto S., Shirasu Y. 1982. Dominant lethal studies 
in rats with 1,2-dibromo-3-chloropropane and its structurally related 
compounds. Mutat Res 101:321-327. (A-91-42, X-A-55)
Sclar, 1999. Sclar, Gary, ``Case Report: Encephalomyeloradicu lo-
neuropathy following exposure to an industrial solvent'' Clinical 
Neurology and Neurosurgery Vol. 01(1999) 99-202. (II-D-34)
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 
(II-D-39)
SLR International Corp, 2001a. Human in vitro bioassays conducted by 
EnviroMed Laboratories (II-D-2)
SLR International Corp., 2001b. ``Inhalation Occupational Exposure 
Limit for n-Propyl Bromide.'' Prepared for Enviro Tech International, 
Inc. 2001. (II-D-15)
US EPA, 1991a. Toxicity summary for 2-nitropropane. U.S. Environmental 
Protection Agency. Integrated Risk Information System. Last updated 1 
March 1991. (II-A-10)
US EPA, 1991b. Guidelines for Developmental Toxicity Risk Assessment. 
U.S. Environmental Protection Agency. (II-A-51)
US EPA, 1994. U.S. Environmental Protection Agency (USEPA). 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. (II-A-16)
US EPA, 1995a. SCREEN3 air dispersion model. (II-A-53)
US EPA, 1995b. The Use of the Benchmark Dose Approach in Health Risk 
Assessment. EPA/630-R-94-007. Risk Assessment Forum, Washington, DC. 
(II-A-17)
US EPA, 2000b. Science Policy Council Handbook: Peer Review, 2nd 
Edition. EPA Report 100-B-00-001, Office of Science Policy, Office of 
Research and Development. December 2000. (II-A-46)
US EPA, 2002. E. Birgfeld, EPA, Letter transmitting comments on the 
Expert Panel report of the Center for Evaluation of Risks to Human 
Reproduction on 1-bromopropane and 2-bromopropane. May 9, 2002. (II-A-
14)
US EPA, 2003. EPA staff report, ``Economic Impacts: Options for SNAP 
Decision on n-Propyl Bromide.'' (III-A-3)
Wang H., Ichihara G., Yamada T. 1999. Subacute effects of 1-
bromopropane on reproductive organs and the nervous system. Abstracts 
of the 72nd Annual Meeting of Japan Society for Occupational Health. 
May 1999. Tokyo. (II-A-33)
WIL, 2001. WIL Research Laboratories. ``An inhalation two-generation 
reproductive toxicity study of 1-bromopropane in rats.'' Sponsored by 
the Brominated Solvent Consortium. May 24, 2001. (II-D-10)
Yamada T. et al., 2003. Exposure to 1-Bromopropane Causes Ovarian 
Dysfunction in Rats. Toxicol Sci 71:96-103 (II-A-32)
Yu X, Ichihara G, Kitoh J, Xie Z, Shibata E, Kamijima M, Takeuchi Y. 
2001. Neurotoxicity of 2-bromopropane and 1-bromopropane, alternative 
solvents for chlorofluorocarbons. Environ Res 85(1):48-52. (II-D-20)

Potential Market, Lack of Regulatory Controls, and Economic Impacts

AFEAS (Alternative Fluorocarbon Environmental Acceptability Study), 
2002. Data from the Web Site of the Alternative Fluorocarbon 
Environmental Acceptability Study. 2002. (II-A-27)
Biles, 2001. Email from Blake Biles to Jeff Cohen on behalf of the 
Brominated Solvents Consortium (BSOC). Contains the BSOC estimates of 
world-wide nPB sales for the calendar years 2000, 2001, 2002. (II-D-18)
Institute for Research and Technical Assistance (IRTA), April 29, 1999. 
Re: comments on nPB. (Docket A-91-42, item X-B-58)

[[Page 33315]]

Kassem, 2003. January 10, 2003 Letter from O. M. Kassem, Albemarle 
Corporation to K. Bromberg, Small Business Administration Re: n propyl 
bromine SNAP. (II-D-78)
UNEP (United Nations Environmental Programme), 2001: Geographic Market 
Potential and Estimated Emissions of n-Propyl Bromide. Report by the 
Technology and Economic Assessment Panel (TEAP) Task Force of the 
Solvents, Coatings and Adhesives Technical Options Committee (STOC). 
April, 2001. (II-A-21)
US EPA, 2003. EPA staff report, ``Economic Impacts: Options for SNAP 
Decision on n-Propyl Bromide.'' (III-A-3)
Wolf, 2001. July 9, 2001, Letter from C. Wolf, Ultronix to M. Sheppard, 
EPA (II-D-85)

List of Subjects in 40 CFR Part 82

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

    Dated: May 21, 2003.
Christine Todd Whitman,
Administrator.
    For the reasons set out in the preamble, 40 CFR part 82 is proposed 
to be amended as follows:

PART 82--PROTECTION OF STRATOSPHERIC OZONE

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

    Authority: 42 U.S.C. 7414, 7601, 7671-7671q.
    2. Subpart G is amended by adding the following appendix M to read 
as follows:

Subpart G--Significant New Alternatives Policy Program

* * * * *

Appendix M to Subpart G--Substitutes Subject to Use Restrictions and 
Unacceptable Substitutes Listed in the [publication date of final rule] 
final rule

                   Solvent Cleaning Substitutes That are Acceptable Subject to Use Conditions
----------------------------------------------------------------------------------------------------------------
            End use                Substitute         Decision          Use condition       Further information
----------------------------------------------------------------------------------------------------------------
Metals cleaning...............  n-propyl bromide  Acceptable        nPB in this end use    EPA expects that all
                                 (nPB) as a        subject to use    shall not contain      users of nPB will
                                 substitute for    conditions.       more than 0.05%        adhere to a
                                 CFC-113 and                         isopropyl bromide by   voluntary acceptable
                                 methyl                              weight before adding   exposure limit of 25
                                 chloroform.                         stabilizers or other   ppm on an 8-hour
                                                                     chemicals. End users   time-weighted
                                                                     must keep records      average. nPB is
                                                                     documenting            Number 106-94-5 in
                                                                     compliance with this   the CAS Registry.
                                                                     condition for up to
                                                                     two years from the
                                                                     date on the
                                                                     documentation.
Electronics cleaning..........  nPB as a          Acceptable        nPB in this end use    EPA expects that all
                                 substitute for    subject to use    shall not contain      users of nPB will
                                 CFC-113 and       conditions        more than 0.05%        adhere to a
                                 methyl                              isopropyl bromide by   voluntary acceptable
                                 chloroform.                         weight before adding   exposure limit of 25
                                                                     stabilizers or other   ppm on an 8-hour
                                                                     chemicals. End users   time-weighted
                                                                     must keep records      average. nPB is
                                                                     documenting            Number 106-94-5 in
                                                                     compliance with this   the CAS Registry.
                                                                     condition for up to
                                                                     two years from the
                                                                     date on the
                                                                     documentation.
Precision cleaning............  nPB as a          Acceptable        nPB in this end use    EPA expects that all
                                 substitute for    subject to use    shall not contain      users of nPB will
                                 CFC-113 and       conditions.       more than 0.05%        adhere to a
                                 methyl                              isopropyl bromide by   voluntary acceptable
                                 chloroform.                         weight before adding   exposure limit of 25
                                                                     stabilizers or other   ppm on an 8-hour
                                                                     chemicals. End users   time-weighted
                                                                     must keep records      average. nPB is
                                                                     documenting            Number 106-94-5 in
                                                                     compliance with this   the CAS Registry.
                                                                     condition for up to
                                                                     two years from the
                                                                     date on the
                                                                     documentation.
----------------------------------------------------------------------------------------------------------------
Note: In accordance with the limitations provided in section 310(a) of the Clean Air Act (42 U.S.C. 7610(a)),
  nothing in this appendix shall affect the Occupational Safety and Health Administration's authority to enforce
  standards and other requirements under the Occupational Safety and Health Act of 1970 (29 U.S.C. 651 et seq.)


                       Aerosols Substitutes That Are Acceptable Subject to Use Conditions
----------------------------------------------------------------------------------------------------------------
            End use                Substitute         Decision          Use condition       Further information
----------------------------------------------------------------------------------------------------------------
Aerosol solvents..............  n-propyl bromide  Acceptable        nPB in this end shall  EPA expects that all
                                 (nPB) as a        subject to use    not contain more       users of nPB will
                                 substitute for    conditions.       than 0.05% isopropyl   adhere to a
                                 CFC-113, HCFC-                      bromide by weight      voluntary acceptable
                                 141b, and                           before adding          exposure limit of 25
                                 methyl                              stabilizers or other   ppm on an 8-hour
                                 chloroform.                         chemicals. End users   time-weighted
                                                                     must keep records      average. nPB is
                                                                     documenting            Number 106-94-5 in
                                                                     compliance with this   the CAS Registry.
                                                                     condition for up to
                                                                     two years from the
                                                                     date on the
                                                                     documentation.
----------------------------------------------------------------------------------------------------------------
Note: In accordance with the limitations provided in section 310(a) of the Clean Air Act (42 U.S.C. 7610(a)),
  nothing in this appendix shall affect the Occupational Safety and Health Administration's authority to enforce
  standards and other requirements under the Occupational Safety and Health Act of 1970 (29 U.S.C. 651 et seq.)


[[Page 33316]]


             Adhesives, Coatings, and Inks Substitutes That Are Acceptable Subject to Use Conditions
----------------------------------------------------------------------------------------------------------------
            End use                Substitute         Decision          Use Condition       Further information
----------------------------------------------------------------------------------------------------------------
Adhesives.....................  n-propyl bromide  Acceptable        nPB in this end use    EPA expects that all
                                 (nPB) as a        subject to use    shall not contain      users of nPB will
                                 substitute for    conditions.       more than 0.05%        adhere to a
                                 CFC-113, HCFC-                      isopropyl bromide by   voluntary acceptable
                                 141b, and                           weight before adding   exposure limit of 25
                                 methyl                              stabilizers or other   ppm on an 8-hour
                                 chloroform.                         chemicals. End users   time-weighted
                                                                     must keep records      average. nPB is
                                                                     documenting            Number 106-94-5 in
                                                                     compliance with this   the CAS Registry.
                                                                     condition for up to
                                                                     two years from the
                                                                     date on the
                                                                     documentation.
----------------------------------------------------------------------------------------------------------------
Note: In accordance with the limitations provided in section 310(a) of the Clean Air Act (42 U.S.C. 7610(a)),
  nothing in this appendix shall affect the Occupational Safety and Health Administration's authority to enforce
  standards and other requirements under the Occupational Safety and Health Act of 1970 (29 U.S.C. 651 et seq.)


[FR Doc. 03-13254 Filed 6-2-03; 8:45 am]
BILLING CODE 6560-50-P