SEQ CHAPTER \h \r 1 ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 82

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

RIN 2060-AK26

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

Substances–n-Propyl Bromide

AGENCY:  Environmental Protection Agency.

ACTION:  Notice of Proposed Rulemaking

SUMMARY:  Pursuant to the U.S. Environmental Protection Agency’s (EPA
or “we”) Significant New Alternatives Policy (SNAP) program, this
action proposes to list n-propyl bromide (nPB) as an acceptable
substitute for methyl chloroform and chlorofluorocarbon (CFC)-113 in the
solvent cleaning sector and to list nPB as acceptable, subject to use
conditions, as a substitute for methyl chloroform, CFC-113, and
hydrochlorofluorocarbon (HCFC)-141b in the coatings end use.  We also
recommend that users be exposed to no more than 17 parts per million of
nPB on an eight-hour, time-weighted average.  This action also proposes
to list nPB as an unacceptable substitute for methyl chloroform,
CFC-113, and HCFC-141b when used in adhesives or in aerosol solvents
because nPB in these end uses poses unacceptable risks to human health,
when compared with other substitutes that are available.  This proposal
supersedes EPA’s proposal of June 3, 2003 on the acceptability of nPB
as a substitute for ozone-depleting substances.

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

DATES:  Comments must be received in writing by [Insert date 60 days
after Federal Register publication date].  Under the Paperwork Reduction
Act, comments on the information collection provisions must be received
by OMB on or before [insert date [thirty] days after date of publication
in the Federal Register].  Any person interested in requesting a public
hearing, must submit such request on or before [insert 30 days from date
of publication in the Federal Register].  If a public hearing is
requested, a separate notice will be published announcing the date and
time of the public hearing and the comment period will be extended until
30 days after the public hearing to allow rebuttal and supplementary
information regarding any material presented at the public hearing.
Inquires regarding a public hearing should be directed to the contact
person listed below.

ADDRESSES:  Submit your comments, identified by Docket ID No.
EPA-HQ-OAR-2002-0064, by one of the following methods:

  HYPERLINK "http://www.regulations.gov"  http://www.regulations.gov .
Follow the on-line instructions for submitting comments.

E-mail<EMAIL_ADDRESS>
Mail:  Air and Radiation Docket, Environmental Protection Agency,
Mailcode 6102T, 1200 Pennsylvania Ave., NW, Washington, DC, 20460,
Attention Docket ID No. EPA-HQ-OAR-2002-0064.  In addition, please mail
a copy of your comments on the information collection provisions to the
Office of Information and Regulatory Affairs, Office of Management and
Budget (OMB), Attn: Desk Officer for EPA, 725 17th St. NW., Washington,
DC 20503.

Hand Delivery:  EPA Docket Center, (EPA/DC) EPA West, Room B102, 1301
Constitution Ave., NW, Washington, D.C., Attention Docket ID No.
EPA-HQ-OAR-2002-0064.  Such deliveries are only accepted during the
Docket’s normal hours of operation, and special arrangements should be
made for deliveries of boxed information.

     Instructions:  Direct your comments to Docket ID No.
EPA-HQ-OAR-2002-0064.  EPA's policy is that all comments received will
be included in the public docket without change and may be made
available online at   HYPERLINK "http://www.regulations.gov"
www.regulations.gov , including any personal information provided,
unless the comment includes information claimed to be Confidential
Business Information (CBI) or other information whose disclosure is
restricted by statute.  Do not submit information that you consider to
be CBI or otherwise protected through www.regulations.gov or e-mail.
The www.regulations.gov websites is an “anonymous access” system,
which means EPA will not know your identity or contact information
unless you provide it in the body of your comment.  If you send an
e-mail comment directly to EPA without going through
www.regulations.gov, your e-mail address will be automatically captured
and included as part of the comment that is placed in the public docket
and made available on the Internet.  If you submit an electronic
comment, EPA recommends that you include your name and other contact
information in the body of your comment and with any disk or CD-ROM you
submit.  If EPA cannot read your comment due to technical difficulties
and cannot contact you for clarification, EPA may not be able to
consider your comment.  Electronic files should avoid the use of special
characters, any form of encryption, and be free of any defects or
viruses.  For additional instructions on submitting comments, go to
Section I.B. of the SUPPLEMENTARY INFORMATION section of this document.

	Docket: All documents in the docket are listed in the   HYPERLINK
"http://www.regulations.gov"  www.regulations.gov  index.  Although
listed in the index, some information is not publicly available, i.e.,
CBI or other information whose disclosure is restricted by statute.
Certain other material, such as copyrighted material, is not placed on
the Internet and will be publicly available only in hard copy form.
Publicly available docket materials are available either electronically
in   HYPERLINK "http://www.regulations.gov"  www.regulations.gov  or in
hard copy at the Air and Radiation Docket, EPA/DC, EPA West, Room B102,
1301 Constitution Ave., NW, Washington, DC.  The Public Reading Room is
open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal
holidays.  The telephone number for the Public Reading Room is (202)
566-1744, and the telephone number for the Air and Radiation Docket is
(202) 566-1742.

FOR FURTHER INFORMATION CONTACT:  Margaret Sheppard, Stratospheric
Protection Division, Office of Atmospheric Programs, Mail Code 6205J,
Environmental Protection Agency, 1200 Pennsylvania Ave., NW.,
Washington, DC 20460; telephone number<PHONE_NUMBER>; fax number (202)
343-2338, e-mail address<EMAIL_ADDRESS> Notices and
rulemakings under the SNAP program are available on EPA’s
Stratospheric Ozone World Wide Web site at www.epa.gov/ozone/snap/regs.

SUPPLEMENTARY INFORMATION:

	Table of Contents

 TOC \f

I. 	General Information

A. Does this action apply to me?

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

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

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

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

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

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

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

A.  What is EPA proposing today?

B.  What is n-propyl bromide?

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

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

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

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

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

	A.	Availability

	B. 	Impacts on the atmosphere and local air quality

	C.	Ecosystem and other environmental impacts

	D.	Flammability and fire safety

	E.	Impact on human health

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

	A.	Workplace exposure limit

	B.	Community exposure guideline

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

	A.	Solvent Cleaning

B.	Aerosol Solvents

C.	Adhesives

D.	Coatings

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

	A.	Use conditions and their rationale

	B.	Advantages and disadvantages of the alternate proposal

VIII.	What other options did EPA consider?

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

	B.	Regulatory options requiring ventilation equipment

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

X. 	Comparison of EPA’s June 2003 proposal and this proposal

How can I use nPB as safely as possible?

Statutory and Executive Order Reviews

Executive Order 12866:  Regulatory Planning and Review

Paperwork Reduction Act

Regulatory Flexibility Act (RFA)

Unfunded Mandates Reform Act

Executive Order 13132: Federalism

Executive Order 13175:  Consultation and Coordination with Indian Tribal
Governments

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

Executive Order 13211:  Actions that Significantly Affect Energy Supply,
Distribution, or Use

National Technology Transfer and Advancement Act

References

 I. 	General Information tc "I. 	General Information"   TC "I. 	General
Information" \f A \l "1"

	A.	Does this action apply to me?  tc "	A. Does this action apply to me?
" \l 2

	This proposed rule would regulate the use of n-propyl bromide as a
solvent used in industrial equipment for metals cleaning, electronics
cleaning, or precision cleaning, as an aerosol solvent, and as a carrier
solvent in adhesives and coatings.  Businesses in these end uses that
currently might be using nPB, or might want to use it in the future,
include:

Businesses that clean metal parts, such as automotive manufacturers,
machine shops, machinery manufacturers, and electroplaters.

Businesses that manufacture electronics or computer equipment.

Businesses that require a high level of cleanliness in removing oil,
grease, or wax, such as for aerospace applications or for manufacture of
optical equipment.

Foam fabricators that glue pieces of polyurethane foam together or foam
cushion manufacturers that glue fabric around a cushion.

Furniture manufacturers that use adhesive to attach wood parts to
floors, tables and counter tops.

A company that manufactures ammunition for the U.S. Department of
Defense.

	Regulated entities may include:

Table 1–Potentially Regulated Entities, by North American Industrial
Classification System (NAICS) Code or Subsector

Category	NAICS code or subsector	Description of regulated entities

Industry	331	Primary Metal Manufacturing

Industry	332	Fabricated Metal Product Manufacturing

Industry/Military	332992 	Small Arms Ammunition Manufacturing

Industry	333	Machinery Manufacturing

Industry	334	Computer and Electronic Product Manufacturing

Industry	335	Equipment Appliance, and Component Manufacturing

Industry	336	Transportation Equipment Manufacturing

Industry	337	Furniture and Related Product Manufacturing

Industry	339	Miscellaneous Manufacturing

Industry	326150	Urethane and Other Foam Product (except Polystyrene)
Manufacturing

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

	B. 	What should I consider as I prepare my comments for EPA?  tc "	B.
What should I consider as I prepare my comments for EPA? " \l 2

		1.	Submitting Confidential Business Information (CBI).  Do not submit
this information to EPA through www.regulations.gov or e-mail.  Clearly
mark the part or all of the information that you claim to be CBI.  For
CBI information in a disk or CD ROM that you mail to EPA, mark the
outside of the disk or CD ROM as CBI and then identify electronically
within the disk or CD ROM the specific information that is claimed as
CBI.  In addition to one complete version of the comment that includes
information claimed as CBI, a copy of the comment that does not contain
the information claimed as CBI must be submitted for inclusion in the
public docket.  Information so marked will not be disclosed except in
accordance with procedures set forth in 40 CFR part 2.

		2.	Tips for Preparing Your Comments.  When submitting comments,
remember to:

Identify the rulemaking by docket number and other identifying
information (subject heading, Federal Register date and page number).

Follow directions - The agency may ask you to respond to specific
questions or organize comments by referencing a Code of Federal
Regulations (CFR) part or section number.

Explain why you agree or disagree; suggest alternatives and substitute
language for your requested changes.

Describe any assumptions and provide any technical information and/or
data that you used.

If you estimate potential costs or burdens, explain how you arrived at
your estimate in sufficient detail to allow for it to be reproduced.

Provide specific examples to illustrate your concerns, and suggest
alternatives.

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

Make sure to submit your comments by the comment period deadline
identified.

    	C.	What acronyms and abbreviations are used in the preamble?  tc
"C.  What acronyms and abbreviations are used in the preamble? " \l 2

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

8-hr—eight hour

ACGIH–American Conference of Governmental Industrial Hygienists

AEL–acceptable exposure limit

ASTM–American Society for Testing and Materials

BMD–benchmark dose

BMDL–benchmark dose lowerbound, the lower 95%-confidence level bound
on the dose/exposure associated with the benchmark response

BSOC–Brominated Solvents Consortium

CAA–Clean Air Act

CAS Reg. No–Chemical Abstracts Service Registry Identification Number

CBI–Confidential Business Information

CEG–community exposure guideline

CERHR–Center for the Evaluation of Risks to Human Reproduction

CFC-113–the ozone-depleting chemical
1,1,2-trifluoro-1,2,2-trichloroethane, C2Cl3F3, CAS Reg. No. 76-13-1

CFC–chlorofluorocarbon

cfm–cubic feet per minute

CFR–Code of Federal Regulations

CNS–central nervous system

DNA—deoxyribonucleic acid

EDSTAC--The Endocrine Disruptor Screening and Testing Advisory Committee

EPA–the United States Environmental Protection Agency

FR–Federal Register

GWP—global warming potential

HCFC-123–the ozone-depleting chemical
1,2-dichloro-1,1,2-trifluoroethane, CAS Reg. No. 306-83-2

HCFC-141b–the ozone-depleting chemical 1,1-dichloro-1-fluoroethane,
CAS Reg. No. 1717-00-6

HCFC-225ca/cb–the commercial mixture of the two ozone-depleting
chemicals 3,3-dichloro- 1,1,1,2,2-pentafluoropropane, CAS Reg. No.
422-56-0 and 1,3-dichloro-1,1,2,2,3-pentafluoropropane, CAS Reg. No.
507-55-1

HCFC–hydrochlorofluorocarbon

HEC–human equivalent concentration

HFC-245fa–the chemical 1,1,3,3,3-pentafluoropropane, CAS Reg. No.
460-73-1

HFC-365mfc–the chemical 1,1,1,3,3-pentafluorobutane, CAS Reg. No.
405-58-6

HFC-4310mee –the chemical 1,1,1,2,3,4,4,5,5,5-decafluoropentane, CAS
Reg. No. 138495-42-8 HFC–hydrofluorocarbon

HFE–hydrofluoroether

HHE–health hazard evaluation

ICF–ICF Consulting

ICR–Information Collection Request

iPB–isopropyl bromide, C3H7Br, CAS Reg. No. 75-26-3, an isomer of
n-propyl bromide; also called 2-bromopropane or 2-BP

Koc–organic carbon partition coefficient, for determining the tendency
of a chemical to bind to organic carbon in soil

LC50 –the concentration at which 50% of test animals die

LOAEL–Lowest Observed Adverse Effect Level

Log Kow–logarithm of the octanol-water partition coefficient, for
determining the tendency of a chemical to accumulate in lipids or fats
instead of remaining dissolved in water

mg/l–milligrams per liter

MSDS–Material Safety Data Sheet

NAICS–North American Industrial Classification System

NESHAP–National Emission Standard for Hazardous Air Pollutants

NIOSH–National Institute for Occupational Safety and Health

NOAEL–No Observed Adverse Effect Level

NOEL–No Observed Effect Level

nPB–n-propyl bromide, C3H7Br, CAS Reg. No. 106-94-5; also called
1-bromopropane or 1-BP

NPRM–Notice of Proposed Rulemaking

NTP–National Toxicology Program

NTTAA–National Technology Transfer and Advancement Act

ODP–ozone depletion potential

ODS–ozone-depleting substance

OEHHA–Office of Environmental Health Hazard Assessment of the
California Environmental Protection Agency

OMB–U.S. Office of Management and Budget

OSHA–the United States Occupational Safety and Health Administration

PCBTF–parachlorobenzotrifluoride, CAS Reg. No. 98-56-6

PEL–Permissible Exposure Limit

ppm–parts per million

RCRA–Resource Conservation and Recovery Act

RFA–Regulatory Flexibility Act

RfC–reference concentration

SNAP–Significant New Alternatives Policy

TCA–the ozone-depleting chemical 1,1,1-trichloroethane, CAS Reg. No.
71-55-6; also called methyl chloroform, MCF, or 1,1,1

–Threshold Limit Value™

TSCA–Toxic Substances Control Act

TWA–time-weighted average

UF–uncertainty factor

UMRA–Unfunded Mandates Reform Act

U.S.C.–United States Code

VMSs–volatile methyl siloxanes

VOC–volatile organic compound

WEL–workplace exposure limit

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

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

	Section 612 of the Clean Air Act (CAA) authorizes EPA to develop a
program for evaluating alternatives to ozone-depleting substances,
referred to as the Significant New Alternatives Policy (SNAP) program.
The major provisions of section 612 are:

Rulemaking–Section 612(c) requires EPA to promulgate rules making it
unlawful to replace any class I (chlorofluorocarbon, halon, carbon
tetrachloride, methyl chloroform, and hydrobromofluorocarbon) or class
II (hydrochlorofluorocarbon) substance with any substitute that the
Administrator determines may present adverse effects to human health or
the environment where the Administrator has identified an alternative
that (1) reduces the overall risk to human health and the environment,
and (2) is currently or potentially available.

Listing of Unacceptable/Acceptable Substitutes--Section 612(c) also
requires EPA to publish a list of the substitutes unacceptable for
specific uses.  We must publish a corresponding list of acceptable
alternatives for specific uses.

Petition Process--Section 612(d) grants the right to any person to
petition EPA to add a substitute to or delete a substitute from the
lists published in accordance with section 612(c).  EPA has 90 days to
grant or deny a petition.  Where the Agency grants the petition, we must
publish the revised lists within an additional six months.

90-day Notification--Section 612(e) requires EPA to require any person
who produces a chemical substitute for a class I substance to notify the
Agency not less than 90 days before new or existing chemicals are
introduced into interstate commerce for significant new uses as
substitutes for a class I substance.  The producer must also provide the
Agency with the producer's health and safety studies on such
substitutes.

Outreach--Section 612(b)(1) states that the Administrator shall seek to
maximize the use of federal research facilities and resources to assist
users of class I and II substances in identifying and developing
alternatives to the use of such substances in key commercial
applications.

Clearinghouse--Section 612(b)(4) requires the Agency to set up a public
clearinghouse of alternative chemicals, product substitutes, and
alternative manufacturing processes that are available for products and
manufacturing processes which use class I and II substances.

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

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

	Anyone who plans to market or produce a substitute for an
ozone-depleting substance (ODS) in one of the eight major industrial use
sectors must provide the Agency with health and safety studies on the
substitute at least 90 days before introducing it into interstate
commerce for significant new use as an alternative.  This requirement
applies to the person planning to introduce the substitute into
interstate commerce, typically chemical manufacturers, but may also
include importers, formulators or end-users when they are responsible
for introducing a substitute into commerce.

	The Agency has identified four possible decision categories for
substitutes:  acceptable; acceptable subject to use conditions;
acceptable subject to narrowed use limits; and unacceptable.  Use
conditions and narrowed use limits are both considered “use
restrictions” and are explained below.  Substitutes that are deemed
acceptable with no use restrictions (no use conditions or narrowed use
limits) can be used for all applications within the relevant sector
end-use.  Substitutes that are acceptable subject to use restrictions
may be used only in accordance with those restrictions.  It is illegal
to replace an ODS with a substitute listed as unacceptable.

	After reviewing a substitute, the Agency may make a determination that
a substitute is acceptable only if certain conditions of use are met to
minimize risks to human health and the environment.  We describe such
substitutes as "acceptable subject to use conditions."  If you use these
substitutes without meeting the associated use conditions, you use these
substitutes in an unacceptable manner and you could be subject to
enforcement for violation of section 612 of the Clean Air Act.

	For some substitutes, the Agency may permit a narrowed range of use
within a sector.   For example, we may limit the use of a substitute to
certain end-uses or specific applications within an industry sector or
may require a user to demonstrate that no other acceptable end uses are
available for their specific application.  We describe these substitutes
as “acceptable subject to narrowed use limits.”  If you use a
substitute that is acceptable subject to narrowed use limits, but use it
in applications and end-uses which are not consistent with the narrowed
use limit, you are using these substitutes in an unacceptable manner and
you could be subject to enforcement for violation of section 612 of the
Clean Air Act.

	The Agency publishes its SNAP program decisions in the Federal
Register.  For those substitutes that are deemed acceptable subject to
use restrictions (use conditions and/or narrowed use limits), or for
substitutes deemed unacceptable, we first publish these decisions as
proposals to allow the public opportunity to comment, and we publish
final decisions as final rulemakings.

In contrast, we publish substitutes that are deemed acceptable with no
restrictions in “notices of acceptability,” rather than as proposed
and final rules.  As described in the rule implementing the SNAP program
(59 FR 13044), we do not believe that rulemaking procedures are
necessary to list alternatives that are acceptable without restrictions
because such listings neither impose any sanction nor prevent anyone
from using a substitute.

	Many SNAP listings include “comments” or “further information.”
 These statements provide additional information on substitutes that we
determine are either unacceptable, acceptable subject to narrowed use
limits, or acceptable subject to use conditions.  Since this additional
information is not part of the regulatory decision, these statements are
not binding for  use of the substitute under the SNAP program.  However,
regulatory requirements listed in this column are binding under other
programs.  The further information does not necessarily include all
other legal obligations pertaining to the use of the substitute.
However, we encourage users of substitutes to apply all statements in
the “Further Information” column in their use of these substitutes.
In many instances, the information simply refers to sound operating
practices that have already been identified in existing industry and/or
building-code standards.  Thus, many of the comments, if adopted, would
not require the affected industry to make significant changes in
existing operating practices.

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

	For copies of the comprehensive SNAP lists of substitutes or additional
information on

SNAP, look at EPA’s Ozone Depletion World Wide Web site at
http://www.epa.gov/ozone/snap/lists/index.html.  For more information on
the Agency's process

for administering the SNAP program or criteria for evaluation of
substitutes, refer to the SNAP final rulemaking published in the Federal
Register 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? tc "III.	Is EPA listing n–propyl bromide
as an acceptable substitute for ozone-depleting substances?"

	A.	What is EPA proposing today?  tc "	A.  What is EPA proposing today?
" \l 2

	In this action, EPA proposes to list n-propyl bromide (nPB) as (1)
acceptable for use as a substitute for CFC-113 and methyl chloroform in
solvent cleaning in the metals, precision and electronics cleaning end
uses; (2) unacceptable for use as a substitute for CFC-113, methyl
chloroform and HCFC-141b in the adhesive and aerosol solvent end uses;
and (3) acceptable subject to use conditions (limited to coatings at
facilities that have provided EPA with information as of [INSERT DATE OF
PUBLICATION] demonstrating their ability to meet the recommended
workplace exposure limit) as a substitute for methyl chloroform,
CFC-113, and HCFC-141b in the coatings end use.  This Notice of Proposed
Rulemaking (NPRM) supersedes the NPRM published on June 3, 2003 (68 FR
33284).

We also are taking comment on an alternate proposal.  Under the
alternate proposal, nPB would be acceptable, subject to use conditions,
in the metals, electronics, and precision cleaning, aerosol solvent,
adhesives, and coatings end uses.  The use of nPB in these end uses
would be subject to conditions that users must (1) meet a workplace
exposure limit of 17 ppm on an eight-hour time-weighted average (8-hr
TWA), (2) monitor workers’ exposure to nPB using a personal breathing
zone sampler on an eight-hour time-weighted average initially and
periodically (every 6 months or longer, depending on the concentration
during initial monitoring), and (3) keep records of the worker exposure
data on site at the facility for at least three years from the date of
the measurement.

	B.	What is n-propyl bromide?  tc "	B.   What is n-propyl bromide? " \l
2

	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®, EnSolv®, and Solvon® cleaners; Pow-R-Wash® NR Contact
Cleaner, Superkleen Flux Remover 2311 and LPS NoFlash NU Electro Contact
Cleaner aerosols; and Whisper Spray and Fire Retardant Soft Seam 6460
adhesives.

	C. 	What industrial end uses are included in our proposed decision?  tc
"	C. 	What industrial end uses are included in our proposed decision? "
\l 2

Solvent Cleaning  TC "Solvent Cleaning" \f A \l "3"

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

2.	Aerosol Solvents  TC "Aerosol Solvents" \f A \l "3"

	We understand that nPB is being used as an aerosol solvent in:

     •    Lubricants, coatings, or cleaning fluids for electrical or
electronic equipment;

     •    Lubricants, coatings, or cleaning fluids for aircraft
maintenance; or

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

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

Adhesives  TC "Adhesives" \f A \l "3"

	Types of adhesives covered under the SNAP program are those that
formerly used methyl chloroform, specifically, adhesives for laminates,
flexible foam, hardwood floors, tire patches, and metal to rubber
adhesives.  Of these applications, nPB-based adhesives have been used
most widely in spray adhesives used in manufacture of foam cushions, and
to a lesser degree in laminate adhesives.

Coatings  TC "Coatings" \f A \l "3"

	The SNAP program regulates the use of carrier solvents in durable
coatings, including paints, varnishes, and aerospace coatings (59 FR
13118).  The SNAP program currently does not regulate carrier solvents
in lubricant coatings, such as silicone coatings used on medical
equipment (59 FR 13119).  Methyl chloroform has been used as a carrier
solvent in coatings, and to a much lesser degree, HCFC-141b also has
been a carrier solvent.  This rule responds to a submission from a
facility that is substituting methyl chloroform with nPB in an
ammunition coating (sealant).

5.	Proposed Text for Listing Decisions  TC "5.		Proposed Listings" \f A
\l "3"

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

Table 2.  SOLVENT CLEANING

PROPOSED ACCEPTABLE SUBSTITUTES

End Use	Substitute	Decision	Further Information

Metals cleaning, electronics cleaning, and precision cleaning	n-propyl
bromide (nPB) as a substitute for CFC-113 and methyl chloroform
Acceptable 	EPA recommends the use of personal protective equipment,
including chemical goggles, flexible laminate protective gloves and
chemical-resistant clothing.

EPA expects that all users of nPB will adhere to a voluntary acceptable
exposure limit of 17 parts per million (ppm) on an 8-hour time-weighted
average and would comply with any final Permissible Exposure Limit that
the Occupational Safety and Health Administration issues in the future.

nPB, also known as 1-bromopropane, is Number 106-94-5 in the Chemical
Abstracts Service (CAS) Registry.

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

Table 3.  AEROSOLS

PROPOSED UNACCEPTABLE SUBSTITUTES

End Use	Substitute	Decision	Further Information

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

Table 4.  ADHESIVES, COATINGS, AND INKS

PROPOSED UNACCEPTABLE SUBSTITUTES

End Use	Substitute	Decision	Further Information

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

Table 5.  ADHESIVES, COATINGS, AND INKS

SUBSTITUTES THAT ARE PROPOSED ACCEPTABLE SUBJECT TO USE CONDITIONS

End Use	Substitute	Decision	Use Conditions	Further Information

Coatings	n-propyl bromide (nPB) as a substitute for methyl chloroform,
CFC-113, and HCFC-141b	Acceptable subject to use conditions	Use is
limited to coatings at facilities that have provided EPA information
demonstrating their ability to meet the recommended workplace exposure
limit as of [INSERT DATE OF PUBLICATION].

	EPA recommends the use of personal protective equipment, including
chemical goggles, flexible laminate protective gloves and
chemical-resistant clothing.

EPA expects that all users of nPB will adhere to a voluntary acceptable
exposure limit of 17 ppm on an 8-hour time-weighted average and would
comply with any final Permissible Exposure Limit that the Occupational
Safety and Health Administration issues in the future.

nPB, also known as 1-bromopropane, is Number 106-94-5 in the CAS
Registry.

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

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

ALTERNATE PROPOSAL

Table 6.  SOLVENT CLEANING

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

End Use	Substitute	Decision	Use Conditions	Further Information

Metals cleaning, electronics cleaning, and precision cleaning	n-propyl
bromide (nPB) as a substitute for CFC-113, HCFC-141b, and methyl
chloroform	Acceptable subject to use conditions	The owner or operator of
a facility must ensure that users of nPB achieve a workplace exposure
limit (WEL) of 17 ppm on an 8-hour time-weighted average.

The owner or operator of a facility must ensure that workers using nPB
are monitored for their exposure to nPB using personal breathing zone
samples on an eight-hour, time-weighted average (8-hr TWA) no later than
90 days after the effective date of this rule.

If the most recent data from exposure monitoring shows all personal
breathing exposures to be at or below 8.5 ppm, no periodic exposure
monitoring is required.  If the most recent data from exposure
monitoring shows all exposures to be at or below 17 ppm, but some above
8.5 ppm, the owner or operator must take personal breathing zone samples
for nPB users at least once during the next six months.

The owner or operator may discontinue the periodic 8-hour TWA monitoring
for nPB users at the facility where at least two consecutive sets of
measurements taken at least seven days apart are below 8.5 ppm.

The owner or operator must determine the exposure of each nPB user by
either taking personal breathing zone air samples of each user's
exposure or samples that are representative of each user's exposure.
The samples are representative where the owner or operator has taken one
or more personal breathing zone air samples for at least one nPB user in
each job classification in a work area during every work shift, and the
nPB user sampled is expected to have the highest exposure to nPB.

The owner or operator also must perform exposure monitoring when a
change in workplace conditions indicates that employee exposure may have
increased or whenever new applications of nPB are introduced.  Perform
exposure monitoring before making planned changes, and perform
monitoring no later than 7 days after an emergency change in conditions.

All personal breathing zone samples must be analyzed either by NIOSH
method 1003 or 1025 or by another method that is accurate to + 25% at a
95 percent confidence level.

The owner or operator must keep records of nPB worker exposure data at
the facility for at least three years from the date the measurements
were taken.   	EPA recommends the use of personal protective equipment,
including chemical goggles, flexible laminate protective gloves and
chemical-resistant clothing.  The American Conference of Governmental
Industrial Hygienists recommends a threshold limit value of 10 ppm.

nPB, also known as 1-bromopropane, is Number 106-94-5 in the CAS
Registry.

Note that the Occupational Safety and Health Administration (OSHA) may
establish a final Permissible Exposure Limit (PEL) standard in the
workplace at 29 CFR part 1910 under 42 U.S.C. 7610(a).

OSHA’s standard on access to employee exposure and medical records
requires retaining exposure records for at least 30 years (29 CFR
1910.1020(d)(ii)).

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

Table 7.  AEROSOLS

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

End Use	Substitute	Decision	Use Conditions	Further Information

Aerosol solvents	n-propyl bromide (nPB) as a substitute for CFC-113,
HCFC-141b, and methyl chloroform	Acceptable subject to use conditions
The owner or operator of a facility must ensure that users of nPB
achieve a workplace exposure limit (WEL) of 17 ppm on an 8-hour
time-weighted average.

The owner or operator of a facility must ensure that workers using nPB
are monitored for their exposure to nPB using personal breathing zone
samples on an eight-hour, time-weighted average (8-hr TWA) no later than
90 days after the effective date of this rule.

If the most recent data from exposure monitoring shows all personal
breathing exposures to be at or below 8.5 ppm, no periodic exposure
monitoring is required.  If the most recent data from exposure
monitoring shows all exposures to be at or below 17 ppm, but some above
8.5 ppm, the owner or operator must take personal breathing zone samples
for nPB users at least once during the next six months.

The owner or operator may discontinue the periodic 8-hour TWA monitoring
for nPB users at the facility where at least two consecutive sets of
measurements taken at least seven days apart are below 8.5 ppm.

The owner or operator must determine the exposure of each nPB user by
either taking personal breathing zone air samples of each user's
exposure or samples that are representative of each user's exposure.
The samples are representative where the owner or operator has taken one
or more personal breathing zone air samples for at least one nPB user in
each job classification in a work area during every work shift, and the
nPB user sampled is expected to have the highest exposure to nPB.

The owner or operator also must perform exposure monitoring when a
change in workplace conditions indicates that employee exposure may have
increased or whenever new applications of nPB are introduced.  Perform
exposure monitoring before making planned changes, and perform
monitoring no later than 7 days after an emergency change in conditions.

All personal breathing zone samples must be analyzed either by NIOSH
method 1003 or 1025 or by another method that is accurate to + 25% at a
95 percent confidence level.

The owner or operator must keep records of nPB worker exposure data at
the facility for at least three years from the date the measurements
were taken.   	EPA recommends the use of personal protective equipment,
including chemical goggles, flexible laminate protective gloves and
chemical-resistant clothing.  The American Conference of Governmental
Industrial Hygienists recommends a threshold limit value of 10 ppm.

nPB, also known as 1-bromopropane, is Number 106-94-5 in the CAS
Registry.

Note that the Occupational Safety and Health Administration (OSHA) may
establish a final Permissible Exposure Limit (PEL) standard in the
workplace at 29 CFR part 1910 under 42 U.S.C. 7610(a).

OSHA’s standard on access to employee exposure and medical records
requires retaining exposure records for at least 30 years (29 CFR
1910.1020(d)(ii)).

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

Table 8.  ADHESIVES, COATINGS, AND INKS

Alternate Proposal:  SUBSTITUTES THAT ARE PROPOSED

ACCEPTABLE SUBJECT TO USE CONDITIONS

End Use	Substitute	Decision	Use Conditions	Further Information

Adhesives and coatings 	n-propyl bromide (nPB) as a substitute for
CFC-113, HCFC-141b, and methyl chloroform	Acceptable subject to use
conditions	The owner or operator of a facility must ensure that users of
nPB achieve a workplace exposure limit (WEL) of 17 ppm on an 8-hour
time-weighted average.

The owner or operator of a facility must ensure that workers using nPB
are monitored for their exposure to nPB using personal breathing zone
samples on an eight-hour, time-weighted average (8-hr TWA) no later than
90 days after the effective date of this rule.

If the most recent data from exposure monitoring shows all personal
breathing exposures to be at or below 8.5 ppm, no periodic exposure
monitoring is required.  If the most recent data from exposure
monitoring shows all exposures to be at or below 17 ppm, but some above
8.5 ppm, the owner or operator must take personal breathing zone samples
for nPB users at least once during the next six months.

The owner or operator may discontinue the periodic 8-hour TWA monitoring
for nPB users at the facility where at least two consecutive sets of
measurements taken at least seven days apart are below 8.5 ppm.

The owner or operator must determine the exposure of each nPB user by
either taking personal breathing zone air samples of each user's
exposure or samples that are representative of each user's exposure.
The samples are representative where the owner or operator has taken one
or more personal breathing zone air samples for at least one nPB user in
each job classification in a work area during every work shift, and the
nPB user sampled is expected to have the highest exposure to nPB.

The owner or operator also must perform exposure monitoring when a
change in workplace conditions indicates that employee exposure may have
increased or whenever new applications of nPB are introduced.   Perform
exposure monitoring before making planned changes, and perform
monitoring no later than 7 days after an emergency change in conditions.

All personal breathing zone samples must be analyzed either by NIOSH
method 1003 or 1025 or by another method that is accurate to + 25% at a
95 percent confidence level.

The owner or operator must keep records of nPB worker exposure data at
the facility for at least three years from the date the measurements
were taken.  	EPA recommends the use of personal protective equipment,
including chemical goggles, flexible laminate protective gloves and
chemical-resistant clothing.  The American Conference of Governmental
Industrial Hygienists recommends a threshold limit value of 10 ppm.
nPB, also known as 1-bromopropane, is Number 106-94-5 in the CAS
Registry.

Note that the Occupational Safety and Health Administration (OSHA) may
establish a final Permissible Exposure Limit (PEL) standard in the
workplace at 29 CFR part 1910 under 42 U.S.C. 7610(a).

OSHA’s standard on access to employee exposure and medical records
requires retaining exposure records for at least 30 years (29 CFR
1910.1020(d)(ii)).

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

D.  What does an unacceptability determination on adhesives and aerosols
mean?  tc "	D. How would the proposed unacceptability determination on
adhesives work? " \l 2

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

	E. What is the scope of the proposed determination for coatings?  tc "
E. How would the proposed regulatory restriction on coatings work? " \l
2

	We propose to list nPB as an acceptable substitute, subject to use
conditions, for methyl chloroform, CFC-113, and HCFC-141b in coatings
for facilities that have provided EPA information demonstrating their
ability to meet the recommended workplace exposure limit as of [INSERT
DATE OF PUBLICATION].  EPA has received a petition to allow use for the
ammunition coating application at Lake City Army Ammunition Plant.  This
is the only coatings application or facility for which EPA has exposure
and usage data demonstrating an ability to meet the recommended
workplace exposure limit when using nPB in coatings.  If other
facilities are interested in using nPB as a substitute for methyl
chloroform, CFC-113, or HCFC-141b in their coatings application, or if a
person wishes to market nPB for such use, then the interested party
would need to make a submission under the SNAP program.

How would the use conditions in the alternate proposal work?  TC "How
would the use conditions in the alternative proposal work?" \f A \l "2"

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

Workplace Exposure Limit

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

Initial Worker Exposure Monitoring

For each facility where nPB is used, the owner or operator of the
facility would be required to ensure that personal breathing zone air
samples of each nPB user’s exposure would be collected on an
eight-hour, time-weighted average initially within 90 days after a final
rule becomes effective.  Monitoring measurements may be taken with an
organic chemical monitoring badge on the collar or a tube filled with
charcoal on the collar.

Periodic Exposure Monitoring

The owner or operator of the facility would be required to ensure that
personal breathing zone air samples of user exposure are collected
periodically on an eight-hour, time-weighted average depending on the
results of the most recent set of exposure data.  A monitoring program
could be instituted by the company or by the nPB supplier for that
facility.  Periodic sampling requirements would be based on the most
recent monitoring results, as follows:

Table 9.  Exposure Levels and Periodic Exposure Monitoring

under the Alternate Proposal

If exposure measurements for nPB are at this level:	then the owner or
operator:

all measurements at or below 8.5 ppm	is not required to perform periodic
exposure monitoring.

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

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

unknown, in cases of new workplace conditions increasing exposure or new
applications of nPB	must take personal breathing zone samples as a test
before using nPB in new industrial applications or conditions, or within
7 days of an emergency caused by a leak, rupture or breakdown, and use
this value to determine the next time monitoring is required.

 For periodic monitoring, the owner or operator would be allowed either
to monitor each nPB user’s exposure, or to monitor exposure of a
representative nPB user in each job classification in a work area during
every work shift, where the monitored nPB user is expected to have the
highest exposure.

The owner or operator would be allowed to discontinue the periodic
8-hour TWA monitoring for nPB users at the facility where at least two
consecutive sets of measurements taken at least seven days apart are
below 8.5 ppm.

Monitoring for new conditions or applications

Whenever there is a change in workplace conditions that may increase
exposure or whenever a new application of nPB is introduced, the owner
or operator would be required to take personal breathing zone samples
accounting for all nPB users as a test before using nPB in manufacturing
or repair.   These could be either samples for each nPB user or samples
representing each job classification in a work area during a work shift,
so long as the samples are based on the user with the likely highest
exposure.  Examples of changes in workplace conditions that may increase
exposure include changes in production, process control equipment, or
work practices, or a leak, rupture, or other breakdown.  Examples of
introduction of a new application of nPB include aerosol contact
cleaning in a location with regional ventilation or natural ventilation,
where previous measurements were carried out on workers in a location
with local ventilation, or cleaning with an open-top vapor degreaser
when previous measurements were performed on workers using enclosed,
conveyorized cleaning equipment.  If the change occurs because of an
unpredictable emergency, then the owner or operator would need to ensure
exposure monitoring takes place within 7 days of the change.

Sampling methods and accuracy

Exposure samples would be required to be analyzed either by NIOSH
method 1003 for halogenated hydrocarbons or method 1025 for
1-bromopropane and 2-bromopropane or by another method that is accurate
to + 25% at the 95 percent confidence level.

Recordkeeping requirements

The owner or operator of the facility would be required to keep records
of the monitored exposure data at the facility for at least three years
from the date the measurements were taken for purposes of this rule.
These records would be required to be made available in the event of a
facility inspection or a request for the data by EPA.   Note that the
employer would still need to meet OSHA’s standard on access to
employee exposure and medical records, which requires retaining any
exposure records for at least 30 years (29 CFR 1910.1020(d)(ii)).

IV.	What criteria did EPA consider in preparing this proposal? tc "IV.
What did EPA consider in preparing today’s proposal?"

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

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

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

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

(iv) Occupational risks;

(v) Consumer risks;

(vi) Flammability; and

(vii) Cost and availability of the substitute.

	In this review, EPA considered all the criteria above except for
consumer risks.  n-propyl bromide is used in industrial applications
such as electronics cleaning or spray adhesives used in foam
fabrication.  In those consumer products made using nPB, such as a piece
of furniture or a computer, the nPB would have evaporated long before a
consumer would purchase the item.  Therefore, we believe there is no
consumer exposure risk to evaluate in the end uses we evaluated for this
rule.

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

	Section 612(c) of the Clean Air Act directs EPA to publish a list of
replacement substances (“substitutes”) for class I and class II
ozone depleting substances based on whether the Administrator determines
they are safe (when compared with other currently or potentially
available substitutes) for specific uses or are to be prohibited for
specific uses.  EPA must compare the risks to human health and the
environment of a substitute to the risks associated with other
substitutes that are currently or potentially available.  In addition,
EPA also considers whether the substitute for class I and class II ODSs
“reduces the overall risk to human health and the environment”
compared to the ODSs being replaced.  Our evaluation is based on the end
use; for example, we compared nPB as a metal cleaning solvent against
other available or potentially available metal cleaning alternatives,
and we compared nPB as a carrier solvent in adhesives to other available
or potentially available adhesive alternatives.

	Although EPA does not judge the effectiveness of an alternative for
purposes of determining whether it is acceptable, we consider
effectiveness when determining whether alternatives that pose less risk
are available in a particular application within an end use.  There are
a wide variety of acceptable alternatives listed for solvent cleaning,
but not all are appropriate for a specific application because of
differences in soils, materials compatibility, degree of cleanliness
required, local environmental requirements, and other factors.  For
example, aqueous cleaners are effective cleaners in many situations and
are the substitute of choice for many in the metal cleaning end use.
However, in some specific precision cleaning applications that require a
high degree of cleanliness and that have narrow spaces that may trap
water used in rinsing, aqueous cleaners may not be appropriate and thus
are not available in that specific application.

	 EPA evaluated each of the criteria separately and then considered
overall risk to human health and the environment in comparison to other
available or potentially available alternatives.  We concluded that
overall, environmental risks were not sufficient to find nPB
unacceptable in any of the evaluated end uses.  However, the overall
risks to human health, and particularly the risks to worker health, are
sufficiently high in the adhesive and aerosol solvent end uses to
warrant our proposal to find nPB unacceptable.

A.	Availability   tc "Availability  " \l 3

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

	Many of the same substitutes may be used and are commercially available
in aerosol solvents:  water-based formulations, alcohols, ketones,
esters, ethers, terpenes, HCFC-141b, HCFC-225ca/cb, HFEs, HFC-4310mee,
HFC-365mfc, HFC-245fa, hydrocarbons, trans-1,2-dichloroethylene,
chlorinated solvents, and PCBTF.  Of these, hydrocarbons, alcohols,
blends of trans-1,2-dichloroethylene and HFEs or HFCs, and HCFC-225ca/cb
are most likely to be used in the same applications as nPB.  nPB is
already commercially available in aerosols.  Its use is primarily for
electrical contact cleaning, with some use for benchtop cleaning
applications (Williams, 2005).

	Many alternatives are also available for use in adhesives, coatings,
and inks:  water-based formulations, high solid formulations, alcohols,
ketones, esters, ethers, terpenes, HFEs, hydrocarbons,
trans-1,2-dichloroethylene, chlorinated solvents, PCBTF, and a number of
alternative technologies (e.g., powder, hot melt, thermoplastic plasma
spray, radiation-cured, moisture-cured, chemical-cured, and reactive
liquid).  Of these, the alternative adhesives most likely to be used in
the same applications as nPB are water-based formulations, adhesives
with methylene chloride, and flammable adhesives with acetone (IRTA,
2000).  nPB is already used in adhesives, and particularly in foam
fabrication and in constructing seating for aircraft (IRTA, 2000;
Seilheimer, 2001).

	To our knowledge, nPB is potentially available as a carrier solvent in
coatings, but has not yet been commercialized, except for use by one
facility, the Lake City Army Ammunition Plant.  The Lake City Army
Ammunition Plant evaluated twenty-nine carrier solvent alternatives to
methyl chloroform and determined that nPB is the only satisfactory
alternative for their application given the current process at that
facility (Harper, 2005).

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

	B. 	Impacts on the atmosphere and local air quality   TC "2.
Atmospheric effects" \f A \l "3"

	As discussed in the June, 2003 proposal, nPB emissions from the
continental United States are estimated to have an ozone depletion
potential (ODP) of approximately 0.013-0.018, (Wuebbles, 2002), lower
than that of the ozone depletion potential of the substances that nPB
would replace -- CFC-113 (ODP=1.0), and methyl chloroform and HCFC-141b
(ODPs = 0.12) (WMO, 2002).  Some other acceptable alternatives for these
ODSs also have low ODPs.  For example, HCFC-225ca/cb has an ODP of
0.02-0.03 (WMO, 2002) and is acceptable in metals cleaning and aerosol
solvents, and acceptable subject to use conditions in precision cleaning
and electronics cleaning.  HCFC-123 has an ODP of 0.02 (WMO, 2002), and
is an acceptable substitute in precision cleaning.  There are other
acceptable cleaners that essentially have no ODP--aqueous cleaners,
HFEs, HFC-4310mee, HFC-365mfc, HFC-245fa, hydrocarbons, VMSs, methylene
chloride, TCE, perchloroethylene, and PCBTF.  Based on this information,
we do not believe the use of nPB within the U.S., and within the
end-uses reviewed in this rulemaking, poses a significantly greater risk
to the ozone layer than other available substitutes.

	Comments on the June 2003 NPRM expressed concern that other countries,
particularly those in equatorial regions, might assume that nPB does not
pose a danger to the stratospheric ozone layer if the U.S. EPA’s SNAP
program finds nPB acceptable (Linnell, 2003; Steminiski, 2003).  We
recognize the concern that if significant nPB usage were to occur in
equatorial regions, there could be an impact on the ozone layer.
However, EPA is regulating use in the U.S. and cannot dictate actions
taken by other countries.  We believe the more appropriate forum to
address this concern is through the Parties to the Montreal Protocol.

	Use of nPB is controlled as a volatile organic compound (VOC) under
state and local regulations to comply with National Ambient Air Quality
Standards for ground-level ozone, which is a respiratory irritant.
Users located in ozone non-attainment areas may need to consider using a
substitute for cleaning that is not a VOC or if they choose to use a
substitute that is a VOC, they may need to control emissions.  Companies
have petitioned EPA, requesting that we exempt nPB from regulation as a
VOC.  However, unless and until EPA issues a final rulemaking exempting
a compound from the definition of VOC, that compound is still regulated
as a VOC.  Other acceptable ODS-substitute solvents that are VOCs for
state air quality planning purposes include most oxygenated solvents
such as alcohols, ketones, esters, and ethers; hydrocarbons and
terpenes; trichloroethylene; trans-1,2-dichloroethylene;
monochlorotoluenes; and benzotrifluoride.  Some VOC-exempt solvents that
are acceptable ODS substitutes include HFC-245fa for aerosol solvents;
HCFC-225ca/cb, HFC-365mfc and HFC-4310mee for metals electronics, and
precision cleaning and aerosol solvents; and methylene chloride,
perchloroethylene, HFE-7100, HFE-7200, PCBTF, acetone, and methyl
acetate for metals, electronics, and precision cleaning, aerosol
solvents, adhesives, and coatings.

	C.	Ecosystem and other environmental impacts  TC "3.	Ecosystem and
other environmental impacts" \f A \l "3"

	EPA considered the possible impacts of nPB if it were to pollute soil
or water as a waste and compared these impacts to screening criteria
developed by the Endocrine Disruptor Screening and Testing Advisory
Committee (EDSTAC, 1998) (see Table 11).  Available data on the organic
carbon partition coefficient (Koc), the breakdown processes in water and
hydrolysis half-life, and the volatilization half-life indicate that nPB
is less persistent in the environment than many solvents and would be of
low to moderate concern for movement in soil.  Based on the LC50, the
acute concentration at which 50% of tested animals die, nPB’s toxicity
to aquatic life is moderate, being less than that for some acceptable
cleaners (for example, trichloroethylene, hexane, d-limonene, and
possibly some aqueous cleaners) and greater than that for some others
(methylene chloride, acetone, isopropyl alcohol, and some other aqueous
cleaners).  Based on EPA’s criteria for listing under the Toxics
Release Inventory, nPB would not be sufficiently toxic to aquatic life
to warrant listing, since the LC50 is greater than 10 mg/l (US EPA,
1992).  Based on its relatively low bioconcentration factor and log Kow
value, nPB is not prone to bioaccumulation.  Table 10 summarizes
information on environmental impacts of nPB; trans-1,2-dichloroethylene,
a commonly-used solvent in blends for aerosol solvents, precision
cleaning, and electronics cleaning; acetone, a commonly-used carrier
solvent in adhesives; trichloroethylene, a solvent used for metals,
electronics, and precision cleaning; and methyl chloroform, an ODS that
nPB would replace.Table 10.  Ecosystem and Other Environmental
Properties of nPB and Other Solvents

Property	Description of environmental property	Value for nPB	Value for
trans-1,2-dichloro-ethylene	Value for acetone	Value for
trichloroethylene	Value for methyl chloroform

Koc, organic-carbon partition coefficient	Degree to which a substance
tends to stick to soil or move in soil.  Lower values (< 300)* indicate
great soil mobility; values of 300 to 500 indicate moderate mobility in
soil.	330 (Source: ICF, 2004a)	32 to 49 (Source:  ATSDR, 1996)	5.4
(Source:  ATSDR, 1994)	106 to 460 (Source:  ATSDR, 1997)	152 (Source: US
EPA, 1994b)

Break down in water	Mechanism and speed with which a compound breaks
down in the environment.  (Hydrolysis half-life values > 25 weeks* are
of concern.)	Hydrolysis is significant.  Hydrolysis half-life of 26 days
(Source: ICF, 2004a)	Photolytic decomposition, dechlorination and
biodegradation are significant; hydrolysis not significant (Source:
ATSDR, 1996)	Biodegrada-tion is most significant form of breakdown
(Source:  ATSDR, 1994)	Volatilization and biodegradation most
significant, with hydrolysis relatively insignificant.  Hydrolysis
half-life of 10.7 to 30 months (Source:  ATSDR, 1997)	Volatilization
most significant;  biodegradation and hydrolysis also occur (Source:
ATSDR, 2004)

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

LC50 (96 hours) for fathead minnows	Concentration at which 50% of
animals die from toxicity after exposure for 4 days.	67 mg/L (Source:
Geiger, 1988)	108 mg/L (Source: US EPA, 1980)	7280 to 8120 mg/L (Source:
 Fisher Scientific, 2001)	40.7 to 66.8 mg/L (Source:  NPS, 1997)	52.8 to
105 mg/L (Source: US EPA, 1994b)

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

Bioconcen-tration factor 	High factors (>1000)* indicate strong tendency
for fish to absorb the chemical from water into body tissues.	23
(Source:  HSDB, 2004)	5 to 23 (Source:  ATSDR, 1996)	<1 (Source:  ATSDR,
1994)	10 to 100 (Source:  ATSDR, 1997)	<9 (Source: US EPA, 1994b)

* Criteria from EDSTAC, 1998.

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

	D.	Flammability and fire safety  tc "		4.	Flammability and fire safety
" \l 3

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

	E.	Impact on human health  tc "		5.	Impact on human health " \l 3

	In evaluating potential human health impacts of nPB, EPA considered
impacts on both exposed workers and on the general population.  Using
the same approach commented on and then finalized in the original SNAP
rulemaking, EPA evaluated the available toxicity data using EPA
guidelines to develop health-based criteria to characterize human health
risks (US EPA, 1994a. RfC Guidelines; US EPA, 1991.  Guidelines for
Developmental Toxicity Risk Assessment; US EPA, 1995b.  Benchmark Dose
guidelines; US EPA, 1996.  Guidelines for Reproductive Toxicity Risk
Assessment).

	To assess human health risks, EPA followed the four basic steps of risk
assessment outlined by the National Academy of Sciences:  hazard
identification, dose-response relationship, exposure assessment, and
risk characterization (NAS, 1983).  First, EPA examined available
studies on nPB’s effects.  Second, EPA developed a workplace exposure
limit (WEL) (also known as an acceptable exposure limit [AEL]) for
evaluating worker exposure and a community exposure guideline (CEG) for
evaluating exposure to the general population based upon inhalation
exposure.  Third, EPA compared the WEL and CEG to available exposure
data and projections of exposure levels to assess exposure.  Finally,
EPA decided whether there was sufficient evidence indicating that nPB
could be used as safely as other alternatives available in a particular
end use.

		1.	Occupational health risks

f Industrial Hygienists (ACGIH) Threshold Limit Values™ (TLVs).
However, EPA found that the ability to meet the recommended nPB
workplace exposure limit (WEL) of 17 ppm (8-hour time weighted average
[TWA]) varies, depending on equipment used and the end use.  In some
uses, users clearly can meet the WEL (metals, electronics and precision
cleaning), while in other end uses, users may not be able to meet the
WEL following current industry practices (adhesives and aerosols).   We
discuss the ability to meet the nPB WEL in each end use below in section
VI.

	Rat studies indicate that dermal exposure to nPB results in neither
appreciable absorption through the skin (RTI, 2005) nor systemic
toxicity (Elf Atochem, 1995).  Unlike methyl chloride and dichlorvos,
which are absorbed through the skin and could contribute to systemic
toxicity (ACGIH, 1991), EPA is not proposing to include a skin notation
for nPB in the information provided to users associated with this
rulemaking because of the relatively low level of absorption.  The ACGIH
provides no skin notation in its TLV documentation for several solvents,
including nPB, methylene chloride, and perchloroethylene, and there is
no evidence that absorption through the skin is greater for nPB than for
the other halogenated compounds.  Given the possibility that some nPB
can be absorbed through the skin in humans, and that the solvent can
irritate the skin, EPA encourages users to wear protective clothing and
flexible laminate gloves when using nPB and encourages vendors to
include such precautions in their Material Safety Data Sheets (MSDSs).

	EPA also considered the potential health effects of contamination of
nPB formulations with isopropyl bromide (iPB).  In the June 2003
proposed rule, we proposed as a use condition that nPB formulations
contain no more than 0.05% iPB by weight.  Industry has met this
contamination limit for several years without regulation.  Furthermore,
EPA believes that if users are meeting the recommended workplace
exposure limit for nPB of 17 ppm, a worker’s exposure to iPB will be
sufficiently low to avoid adverse effects.  Therefore, this proposed
rule does not include a use condition limiting iPB content in nPB
formulations.

		2.	General population risks

EPA used a community exposure guideline of 1 ppm to assess potential
risks to the general population living near a facility using nPB (see
section V.B below) and determined that community exposures were likely
to be higher for nPB used in adhesives than for nPB used in aerosol
solvents or in metals cleaning, electronics cleaning, or precision
cleaning.  EPA modeled inhalation exposure to nPB to people living near
a plant using nPB-based adhesives in several scenarios using the
Agency’s SCREEN3 model and found that the exposure to individuals in
the general population was below the community exposure guideline.  The
analysis indicates that nPB is no greater a hazard to the general
population than other acceptable solvents under the SNAP program.  For
further discussion, see the risk screen for nPB (ICF, 2006a).

V.	How did EPA derive the proposed workplace exposure limit and
community exposure guideline used to assess impacts on human health?  TC
"How did EPA derive the proposed workplace exposure limit and community
exposure guideline used to assess impacts on human health?" \f A \l "2"

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

A.	Workplace exposure limit  TC "1.	Workplace Exposure Limit" \f A \l
"3"

 OSHA has not developed a permissible exposure limit (PEL) for nPB that
EPA could use to evaluate toxicity risks from workplace exposure.  The
American Conference of Governmental Industrial Hygienists (ACGIH), an
independent organization with expertise in industrial hygiene and
toxicology, has developed a final workplace exposure limit of 10 ppm
(ACGIH, 2005); however, as discussed below, EPA has concerns about the
documentation and basis of ACGIH’s derivation.  Further, there is a
wide range of exposure limits recommended by nPB vendors (from 5 ppm to
100 ppm).  After considering all of the various exposure limits
recommended by industry and governmental organizations, and individual
companies and consultants, and a thorough review of all available data,
EPA has developed a recommended WEL of 17 ppm averaged over eight hours
to assess human health risks and to evaluate the acceptability of nPB in
potential use sectors.

In the June 2003 NPRM, EPA proposed that an exposure limit of 25 ppm
would be protective of a range of effects observed in animal and human
studies, including reproductive and developmental toxicity,
neurotoxicity, and hepatotoxicity.  Reduction of sperm motility in rats,
noted across multiple studies at relatively low exposures, was
determined to be the most sensitive effect, and we derived the
recommended exposure limit in the June 2003 NPRM from a dose response
relationship in male rat offspring (“F1 generation”) whose parents
were exposed to nPB from prior to mating through birth and weaning of
the litters (WIL Research Laboratories, 2001).  For this proposed rule,
we reviewed both new information and the previously available
information on health effects in developing an exposure limit.

1.	Newly Available Data on Health Effects

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

Table 11. Recent Studies on nPB Occupational Exposure

Case Study	Sample Size/Population	Exposure Data	Observations	Remarks

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

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

Ichihara et al., 2004a	37 chemical plant workers (24 males and 13
females)	12 hour shifts over 2-day period, mean concentration of 82 ppm
(range, 0-170 ppm) 	Mucosal irritation (nose, throat), headache,
dizziness, constipation, intoxication, and feeling light-headed or
heavy-headed.  Four female workers complained of disruption or cessation
of menstruation.  No severe chronic symptoms of neurological damage at
less than 170 ppm.  Several workers had hemoglobin and hematocrit values
outside of the normal range and were diagnosed with mild anemia; most of
these cases also showed signs of iron deficiency.	Inadequate exposure
characterization and exposure to other potential toxicants, small sample
size, and no appropriate control group.  Healthy worker effect possible,
where more sensitive workers left the factory between 1996 and 1999.

Ichihara et al., 2004b	27 female chemical plant workers (23 age matched
with 23 females from a beer factory control group)	1-day exposure
period, range of exposure, 0.34-49 ppm	Responses indicated anxiety,
fatigue, confusion, tension, and depression.  Changes in menstrual
status but not statistically significant.  Effects on peripheral and
central nervous system —diminished vibration sensation of the foot;
significantly longer distal latency in the tibial nerve; decreased
values in sensory nerve conduction velocity in the sural nerve; and
lower scores on memory and perceptual tests.  No comparable effects seen
in control group. 	No long-term exposure measurements, small sample
size; lack of controls for age, height, and body-weight.  Low B vitamin
levels in normal range in some workers but researchers concluded this
did not cause observed neurological effects.  Additionally, the study
did not indicate any significant differences in the prevalence of
menstrual cycle abnormalities.

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

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

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

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

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

Table 12. Recent Animal Studies of nPB Effects

Citation	Population/

in rat liver cells ≥ 250 ppm (males) and ≥ 500 ppm (females), with
increased severity at higher doses.  No adverse central nervous system
(CNS) effects or histopathology reported.	Unpublished study.
Conclusions drawn from a review of raw data from the National Toxicology
Program (NTP) web site.  In general, the severity of effects (in
non-reproductive organs) is slightly higher at lower concentrations in
male rats than in females.

RTI, 2005	Female and male B6C3F1mice and Fisher 344N  rats, four to six
animals in each test trial	Exposure via several injection routes
(intraperitoneal, intravenous, cannuliz-ation), inhalation, and dermal.
Injection conducted via bolus dosing at 5, 20, or 100 mg/kg body weight.
 Inhalation concentrations of 70, 240, 800, and 2700 ppm administered in
a single acute exposure.  A dose of 96 mg/kg was applied to a shaved
area on the backs of six male rats with a non-occlusive charcoal filter
covering (that is, one that does not prevent evaporation).  	nPB cleared
by mice after 48 hours as follows:  45% as volatiles in the breath, 28%
as CO2 in the breath, 26% in urine, <3% in feces, and 2% retained in the
body.  Distribution was similar in male rats, although amounts in urine
and volatiles in breath were higher in mice.  At higher doses, the
amount of nPB excreted in urine and as CO2 decreased, with a much
greater change in rats compared to mice.

After pretreatment with a cytochrome P450 inhibitor, a decrease in nPB
cleared as CO2 (80%) and urine (40%); pretreatment with a glutathione
inhibitor reduced  nPB cleared as CO2 by 10% and urine by 4%.

The Vmax, a measure of the maximum initial rate of an enzyme-catalysed
reaction, is 0.227 for male rats, 0.143 for female rats, 0.329 for male
mice and 0.234 for female mice.  Half-lives were comparable between
males and females at ≤ 800 ppm.

For rats exposed to nPB through skin, 37% of the dose was excreted in
volatiles, 1.2 % in urine, 1.7%  as CO2, and 35.7% was on the
applicators or in the skin washes.  Only 0.32% remained in tissues.
Airborne concentrations of nPB in the chamber were 4 to 10 ppm after
dosing.	RTI concluded that:

nPB administered via intraperitoneal injection or inhalation is
eliminated mostly through the breath, with urine as a secondary path.

Metabolism of nPB appears to be primarily through cytochrome P450
enzymes (CYP2E1), particularly in mice; glutathione conjugation still
plays an important role in rats.

At high concentrations, female rats may have a decreased capacity to
metabolize nPB compared to male rats.

nPB decreases glutathione levels in the liver after a one-time exposure
to nPB at concentrations as low as 70 ppm.

nPB is not appreciably absorbed (~3-27%) in rats following dermal
application.

EPA agrees with these points, except we found that gender differences
were only apparent in rats at very high concentrations (2700 ppm and
greater).  We also note that:

Inhalation tests were only one-time exposures at very high
concentrations (240 to 2700 ppm), and thus, are not comparable to
long-term dosing at the lower levels expected in the workplace.

Results of dermal testing are not conclusive because of potential for
inhalation exposure.

Sohn et al., 2002	40 male and 40 female Sprague-Dawley rats	6 hr/day, 5
day/wk for 13 weeks, test groups (10/sex/dose) were exposed to 0, 200,
500 or 1250 ppm	No effects on mortality, activity, weight gain, food
consumption, urinalysis, or histological effects in the brains and
spinal cords. 	The differences between the various studies may be due to
variability in exposure methodology and achieved concentrations of nPB.

Stump, 2005* 	125 female/125 male rats in first generation and 100
female/100 male rats in offspring generation	Both test groups of 25 male
rats/ 25 female rats exposed to 0, 100, 200, 250, 500 and 750 ppm nPB
for 10 weeks	Decreased litter size at 250 and 500 ppm in both
generations. Decreased fertility at 100 and 250 ppm in offspring
generation.

ignificant decrease in antral follicles at ≥ 200 ppm, and a decrease
in the number of female rats exhibiting regular estrous cycles in
400-ppm females during 7-9 weeks of exposure and at 2-3 weeks at the
800-ppm dose.	Data suggest that nPB is affecting the maturation of
ovarian follicles.  A no observed adverse effect level (NOAEL) of 200
ppm is identified with a LOAEL of 400 ppm for the changes in estrus
cycles.

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

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

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

After further reviewing the Yamada et al. (2003) study, published just
prior to the 2003 NPRM, EPA re-evaluated the literature (Ichihara et
al., 1999, 2002, 2004a,b; Sekiguchi, 2002, Yamada et al., 2003; WIL,
2001) to assess potential reproductive toxicity in females (ICF, 2006a,
Att. A). We focused on the WIL study because of the following strengths
described in the June 2003 NPRM: (1) it was conducted in accord with
Good Laboratory Practice procedures and standard test guidelines over
multiple generations; (2) it underwent an independent audit; (3) it
contained a sufficiently large sample size; and (4) the raw data were
provided for detailed statistical analyses.

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

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

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

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

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

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

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

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

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

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

These effects are seen in males, females, and offspring, and in
different generations of the two- generation study (WIL, 2000).  They
also are consistent with results seen in one-generation reproductive
studies, such as Ichihara et al., 2000 and Yamada, 2003.  Of these
effects, the one occurring at the lowest level, and thus protecting
against all adverse health effects, is the number of estrous cycles
during a 3-week period.  Consistent with Agency guidance (US EPA,
1994a), EPA is using 162 ppm as a “point of departure” to derive the
WEL.

2.	Derivation of WEL

	To calculate the WEL for nPB, EPA uses standard risk assessment methods
delineated in Agency guidance (US EPA, 1994a) in evaluating data,
choosing a benchmark dose level or a NOAEL, and making the adjustments
and uncertainty factors prescribed to account for differences in the
duration of exposure and in sensitivity between and within species.

		Adjustment for Occupational Exposure Pattern

To account for differences between the exposure pattern used in the WIL
study (6 hours per day for 7 days per week) when compared to a typical
workweek of 8 hours per day and 5 days a week, a “human equivalent
concentration” (HEC) is first calculated by adjusting the benchmark
dose level:

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

		Uncertainty Factors

According to EPA risk assessment guidance for reference concentrations
(RfC) (EPA 1994a), uncertainty factors of up to 10 may be applied to the
HEC for each of the following conditions:

Data from animal studies are used to estimate effects on humans;

Data on healthy people or animals are adjusted to account for variations
in sensitivity among members of the human population (inter-individual
variability);

Data from subchronic studies are used to provide estimates for chronic
exposure;

Studies that only provide a LOAEL rather than a NOAEL or benchmark dose;
or

An incomplete database of toxicity information exists for the chemical.

EPA believes that two uncertainty factors are appropriate for this
database to account for (1) physiological differences between humans and
rats; and (2) variability within the working population.  The rationale
for the use of these two uncertainty factors is described below.

EPA RfC guidelines state that an uncertainty factor of 10 may be used
for potential differences between study animals and humans.  This factor
of 10 consists in turn of two uncertainty factors of 3 – the first to
account for differences in pharmacodynamics and the second to account
for differences in pharmacokinetics between the study animal and humans.
(The value of three is the square root of 10 rounded to one digit, with
10 representing an order of magnitude (EPA,1994a).  In practice, EPA
uses the square root of 10 when there are two or four uncertainty
factors of 3, yielding a total uncertainty factor of 10 or 100, and we
use a value of 3 when multiplying by other uncertainty factors).  By EPA
RfC guidelines (EPA, 1994a), no adjustment for differences in
pharmacokinetics is necessary in this instance because the blood/air
partition coefficient for nPB in the human (7.1) is less than in the rat
(11.7), indicating that the delivered dose of nPB into the bloodstream
in rats is slightly higher than in humans.  Consistent with Appendix J
of EPA’s RfC guidelines for an inhaled compound that exerts its
effects through the bloodstream, EPA applies an uncertainty factor of 1
for pharmacokinetics.

However, EPA recognizes that the lack of an uncertainty adjustment for
pharmacokinetic differences between animals and humans rests on a
default approach applied to category 3 gases described in Appendix J of
its guidelines for deriving an inhalation RfC.  This default approach
assumes that nPB’s toxicokinetics follow a model in which: (1) the
toxicity is directly related to the inhaled parent compound in the
arterial blood, and (2) the critical metabolic pathways scale across
species, with respect to body weight, in the same way as the ventilation
rate.  Given the hypothesized metabolic pathways for nPB (ICF, 2002a;
CERHR, 2002a), it is plausible that toxicity in rats may be related to a
reactive metabolite in the target tissue rather than the blood level of
the parent compound.  EPA is not aware of any quantitative data on nPB
metabolism in humans, or evidence implicating the biologically active
agent or mode of action.  Some commenters on the June 2003 NPRM stated
that EPA should use an uncertainty factor of 2 or 3 for
pharmacokinetics, or an overall uncertainty factor of 10 for rat to
human extrapolation because of a lack of information on the metabolism
and mode of action of nPB (Werner, 2003; Risotto, 2003).  Recent studies
provide additional data regarding metabolism of nPB in rats and mice
(RTI, 2005), but data on human metabolism are still lacking.

Despite the difference in metabolic pathways for nPB in mice and rats
(RTI, 2005), no significant species-specific differences in toxicity
exist between rats and mice at inhaled concentrations <500 ppm for 13
weeks (NTP, 2003; ICF, 2006c).  EPA requests additional data and comment
from the public on the pharmacokinetics, metabolism, and mode of action
of nPB that will help determine whether an interspecies uncertainty
factor greater than the default value of 1 is warranted to account for
pharmacokinetics.  If data become available indicating that nPB does not
conform to the constraints assumed by the default pharmacokinetic model
in the RfC guidelines, we would revise our risk assessment for nPB as
necessary, and apply an uncertainty factor for pharmacokinetics
consistent with the RfC guidelines in extrapolating from animal to
humans.  Depending on the resulting difference in the recommended WEL,
we would also revise our acceptability determinations accordingly.
Given the available data on the blood/air partition coefficient and EPA
RfC guidance in the absence of other information, EPA is applying the
same rationale used for other compounds reviewed under EPA’s SNAP
program with a comparable amount of data where an uncertainty factor of
1 for pharmacokinetics was applied.  To account for uncertainty in
pharmacodynamics of nPB, EPA is applying the default uncertainty factor
(UF) of 3.  This follows the procedures in EPA’s RfC guidelines for
situations where there are no data to compare pharmacodynamics in rats
versus humans (EPA, 1994a).  Recently published data on humans and
rodents do not decrease the uncertainty regarding the pharmacodynamics
of nPB; therefore, modification of the UF of 3 for differences between
species is not justified.

EPA is also applying an uncertainty factor of 3 to protect for sensitive
subpopulations and variability in the working population.  There are
preexisting reproductive conditions as well as significant variability
in fertility among otherwise healthy women.  For example, in a study of
782 couples, Dunson et al. (2002) found that fertility was twice as high
for women ages 19 to 26 years compared to women ages 35 to 39 years, and
that factors other than age (e.g., smoking, sexually transmitted
diseases, occupational exposure) accounted for a three-fold difference
in fertility rates.  Since similar sources of variability would be
expected among individuals in the workplace, variability in reproductive
capacity of workers of more than 2-fold and less than 10-fold based on
the finding of Dunson et al. (2002) might be expected.  EPA’s RfC
guidelines recommend an uncertainty factor of 10 to account for
intraspecies variability within the general population.  However, in
developing a WEL, EPA’s focus is on worker exposure, which excludes
some particularly vulnerable populations, such as children, most
adolescents, and the elderly.  Under EPA guidelines, 3 is a default
value for an uncertainty factor where there is indication that a value
less than an order of magnitude (10) but greater than one is
appropriate, and where the available data are not sufficiently
quantified to select a specific value.

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

3.	Other Recent Analyses of nPB Toxicity

Since the 2003 NPRM, a number of reviews of nPB toxicity have been
issued, several of which include recommendations for occupational
exposure limits.  CERHR, 2003a and 2004a are similar to CERHR, 2002a,
the expert panel report for nPB for the Center for the Evaluation of
Risks to Human Reproduction (CERHR).  CERHR, 2003b and 2004b are similar
to CERHR, 2002b, the CERHR expert panel’s report for iPB.  Rozman and
Doull, 2005 derived a WEL of 25 ppm for nPB based on neurotoxicity,
using more recent information than Rozman and Doull, 2002.

EPA reviewed Rodricks (2002) in developing its June 2003 NPRM, although
the study was not explicitly mentioned in that preamble.  Rodricks
(2002) suggests a WEL of 60 to 88 ppm for nPB, based on male
reproductive effects.  The Stelljes and Wood (2004) analysis is similar
in its results to SLR International (2001), a study by the same authors.
 EPA previously reviewed both these studies in developing the June 2003
NPRM.   Both studies concluded with a recommended WEL of 156 ppm, based
on male reproductive effects.  Stelljes (2005) reviews RTI’s 2005
study on metabolism of nPB in mice and rats and other literature and
speculates that humans should be less sensitive to nPB than either mice
or rats based on differences in metabolite production.  Stelljes (2005)
recommends that no uncertainty factor is required to extrapolate from
animals to humans and that an uncertainty factor of no more than 2 is
appropriate to account for differences within the working population.
All of these documents assigned uncertainty factors in a manner that is
not sufficiently supported by the available data and that is
inconsistent with EPA’s guidance.  For example, Stelljes (2005)
discusses metabolic data in rats and mice from RTI, 2005 and concludes
that on this basis, the uncertainty factor for extrapolation from
animals to humans should be 1.  However, the metabolic data relate to
pharmacokinetics--the activity of chemicals in the body--and do not
address EPA’s proposed uncertainty factor of 3 related to
pharmacodynamics (the biochemical and physiological effects of chemicals
in the body and the mechanism of their actions).  Using the WEL from one
of these documents would result in a higher, less protective WEL than we
would determine following the approach EPA has used for other chemicals
under the SNAP program and would ignore significant sources of
uncertainty in health effects.  In addition, based on our most recent
examination of the health effects of nPB, these documents do not select
the most sensitive endpoint to protect against female reproductive
effects, effects on live litter size, and other adverse health effects.
Thus, we are concerned that the WELs based on these documents are not
sufficiently protective and would result in an inappropriate
acceptability decision.  Detailed reviews of these documents are
available in the public docket.

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

The California Environmental Protection Agency’s Office of
Environmental Exposure and Hazard Assessment (OEHHA) listed both nPB and
iPB as reproductive toxins on the basis of developmental, male
reproductive, and female reproductive toxicity under the State’s Safe
Drinking Water and Toxic Enforcement Act of 1986, also known as
Proposition 65 (OEHHA, 2006).  Under this law, California is required to
list chemicals known to be carcinogenic or to be reproductive toxins and
to update that list at least annually.

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

In prior SNAP reviews, EPA has used ACGIH TLVs where available in
assessing a chemical’s risks and determining its acceptability.  ACGIH
is recognized as an independent, scientifically knowledgeable
organization with expertise in issues of toxicity and industrial
hygiene.  However, in this case, EPA believes that ACGIH’s TLV for nPB
has significant limitations as a reliable basis for a workplace exposure
limit, especially given the availability of other, more comprehensive
analyses described in this proposal.  First, according to the authors of
the Huntingdon Life Sciences study, the decrease in fetal weight was an
artifact of sampling procedure that biased the data (test animals were
only sacrificed at the end of the day rather than at random).  The CERHR
expert panel excluded “aberrantly low” fetal weights from one litter
in this study and calculated a BMDL greater than 300 ppm for this
endpoint after removing those outlier data (CERHR, 2002a, 2003a, and
2004a).  TERA calculated a similar BMDL when  analyzing the same data
set (TERA, 2004).  Further, the reference list in the documentation on
the TLV indicates that ACGIH did not review and evaluate all the studies
available prior to the development of the recommended exposure limit.
For example, key supporting articles that reported disruption of estrous
cycles (Yamada et al., 2003 and Sekiguchi et al., 2002) were not
discussed in the TLV documentation.  Further, ACGIH did not provide any
reasoning for the selection of the chosen endpoint over others (e.g.,
reproductive toxicity and/or neurotoxicity).  The lack of discussion of
applied uncertainty factors also prevents a determination of how ACGIH
arrived at a TLV of 10 ppm.  In summary, EPA is not basing its proposed
acceptability determination for nPB on the ACGIH TLV because: (1) other
scientists evaluating the database for nPB did not find the reduced pup
weight to be the most sensitive endpoint; (2) benchmark dose (BMD)
analysis of the reduced pup weight data (CERHR, 2002a; TERA, 2004)
results in a higher BMDL (roughly 300 ppm) than those for sperm effects
and estrous cycle changes; and (3) ACGIH may not have reviewed the
complete body of literature as several studies discussing neurotoxicity
and changes in estrous cycle length were omitted from the list of
references.  A review of this document is available in the public
docket.

	B.	Community exposure guideline tc "		2.	CEG " \l 3

	In this proposal, EPA is using a community exposure guideline (CEG) of
1 ppm to evaluate potential health risks among populations living near
facilities using nPB.  This community exposure guideline is an estimate
of a continuous inhalation exposure (averaged over 24 hours per day, 7
days per week) to the general public (including sensitive subgroups)
that is likely to be without an appreciable risk of adverse health
effects during a lifetime.

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

162 ppm x (6 hours exposure in study/24 hours avg time) x (7 days/7
days) = 40 ppm

EPA used an uncertainty factor of 3 for extrapolation from animals to
humans, as discussed above in section VI.A, and an uncertainty factor of
10 for variability within the general population, consistent with
EPA’s RfC guidelines.  Dividing the HEC of 40 ppm by 30 yields a
community exposure guideline of approximately 1 ppm, the same as the
value calculated using liver effects or sperm motility as an endpoint.

	EPA evaluated general population exposure using EPA’s SCREEN3 (US
EPA, 1995a) air dispersion model to assess the likely maximum
concentration of nPB from single sources.  EPA used data collected from
actual facilities (Swanson, 2002) to characterize two scenarios:  (1) a
typical large, high-use adhesive application facility where the closest
resident is 100 meters away; and (2) a smaller facility with average-use
adhesive application in an urban area, where the nearest resident is
only 3 meters away.  The results indicated that modeled exposures in
either scenario did not exceed the CEG of 1 ppm.  The highest exposure
modeled was 0.24 ppm at a distance of 3 meters away from the source in
the urban scenario, while most other exposures were at least an order of
magnitude lower (ICF, 2003; ICF, 2006a).  Because the community exposure
guideline was not exceeded for any of the exposure scenarios in this
conservative screening approach, EPA has concluded that nPB exposure to
populations living close to facilities using nPB is not a major concern.

VI.	What listing is EPA proposing for each sector or end use, and why?
tc "C.	What  proposals is EPA making for each sector or end use based on
these criteria? " \l 2

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

Table 13.  Proposed Decisions by End Use and Sector

For nPB in this sector and end use:	Our proposal is to list nPB as:	And
our alternate proposal is:

Solvent Cleaning

Metals Cleaning	Acceptable (without restriction)	Acceptable, subject to
use conditions2

Electronics Cleaning	Acceptable (without restriction)	Acceptable,
subject to use conditions2

Precision Cleaning	Acceptable (without restriction)	Acceptable, subject
to use conditions2

Aerosols

Aerosol solvents	Unacceptable	Acceptable, subject to use conditions2

Adhesives, Coatings, and Inks

Coatings	Acceptable, subject to use conditions1	Acceptable, subject to
use conditions2

Adhesives	Unacceptable	Acceptable, subject to use conditions2

 1  Use of nPB in this end use is limited to coatings at facilities that
have provided EPA information demonstrating their ability to meet the
recommended workplace exposure limit as of [INSERT DATE OF PUBLICATION]
(i.e., the Lake City Army Ammunition Plant).

2  Use conditions would include proposed requirements that users must
(1) meet a workplace exposure limit of 17 ppm on an eight-hour
time-weighted average, (2) monitor workers’ exposure to nPB using a
personal breathing zone sampler on an eight-hour time-weighted average
initially and periodically (every 6 months or longer, depending on the
concentration during initial monitoring), and (3) keep records of the
worker exposure data on site at the facility for at least three years
from the date of the measurement.

A.	Solvent Cleaning

	There are a number of alternatives that reduce the risks from ozone
depletion or from smog production7 slightly more than nPB when used in
industrial solvent cleaning equipment.  However, we found no single
alternative that could work in all applications that clearly would
reduce overall risks to human health and the environment in metals
cleaning, electronics cleaning, and precision cleaning.  Balancing the
different criteria discussed above in section IV., nPB does not pose a
significantly greater risk than other substitutes or than the ODS it is
replacing in these end uses if users meet the recommended exposure
limit.  As discussed below, we believe that users can and will meet the
recommended exposure limit in these end uses.  Thus, we propose to list
nPB as acceptable in metals cleaning, electronics cleaning, and
precision cleaning.

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

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

	B.	Aerosol Solvents  tc "2.	Aerosol Solvents " \l 3

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

	Available information on the use of nPB in aerosols shows that aerosol
users may not be able to maintain exposures to nPB at or below the
recommended WEL without ventilation or with only regional ventilation
such as a fan for an entire room.  Personal breathing zone samples
collected in a recent study showed 8-hour time-weighted average (TWA)
exposures of 5.5, 13, and 32 ppm for workers using 310 g of nPB from a
spray can (Linnell, 2003).   The two higher exposure levels occurred in
the absence of any local or regional ventilation; the use of both local
and regional ventilation equipment with ventilation levels around 1900
ft3/min was associated with the lowest exposure level.  Similar
measurements were made in another study:  8-hr TWA exposures of 11.3,
15.1, 17.0, and 30.2 ppm with regional ventilation of 300 cubic feet per
minute from a fan for the entire room (Confidential submission, 1998).
In these same two studies, exposure measurements taken from the
breathing zone of workers over 15-minutes, if divided by 32 to estimate
an equivalent 8-hr TWA, would have varied from less than 1 ppm to 34.4
ppm (Linnell, 2003; Confidential submission, 1998).

	These monitoring data are consistent with or slightly higher than data
from EPA modeling that estimates exposures for workers using different
amounts of aerosol (500 and 1000 g over a full day), different rates of
ventilation (450 to 1350 cfm), and different aerosol solvent
formulations (pure nPB and mixtures of nPB and other solvents
commercially available) (ICF, 2006a).  In a space with an air exchange
rate of 450 ft3/minute or less, EPA’s modeling predicts 8-hour average
exposure of approximately 16 to 17 ppm if a user sprays 450 g of pure
nPB (approximately 1 lb), and corresponding higher exposure values at
higher spray rates (e.g., 33 ppm if the amount of nPB sprayed is 900 g)
(ICF, 2006a).  Therefore, if users varied the amount of nPB used only
slightly above a pound per day on average or had ventilation levels
below 450 cfm (face velocity of 50 fpm), they would be exposed in excess
of the WEL.  EPA is aware of no data on ventilation levels that would
demonstrate that most users of aerosol solvents, or of nPB in
particular, would use aerosols in locations with ventilation levels of
450 cfm or greater.  The available worker exposure studies examined
ventilation levels of 0, 48, 300, 472, 640, and 1900 cfm, implying that
manufacturers for this sector believe that ventilation flow rates could
be lower than 450 cfm.  Based on the available monitoring and modeling
data, we expect exposure to nPB to exceed the proposed workplace
exposure limit of 17 ppm in confined spaces and in the many applications
for nPB-based aerosols where ventilation equipment is not or cannot be
installed, such as on energized electrical equipment (Linnell, 2003;
Werner, 2003; CSMA, 1999).  Aerosol manufacturers have stated that the
majority of the market for nPB used in aerosols is for electrical
contact cleaning (Williams, 2005).  We are reviewing nPB as a
replacement for HCFC-141b and in-place cleaning such as for electrical
contact cleaning comprised the majority of the aerosol market for
HCFC-141b (US EPA, 2004).  Further, because aerosol cans are portable
and their use cannot reasonably be monitored continuously, EPA cannot
ensure that nPB-based aerosols are barred from use in confined spaces
where exposure levels would be likely to exceed the WEL and create
excessive health risks.  Thus, EPA believes that it would be difficult
or even impossible to meet a recommended workplace exposure limit of 17
ppm in the majority of situations where nPB would be used as a
substitute for HCFC-141b as an aerosol solvent.

	EPA has found numerous other aerosol solvents acceptable.  These
aerosol solvents can be used safely in a manner consistent with their
respective workplace exposure limits.  This is highlighted in a study
comparing concentrations of eight different chemicals that are
acceptable under the SNAP program in aerosol formulations:  HFE-7100,
HFE-7200, trans-1,2-dichloroethylene, HCFC-225ca and -225cb, acetone,
pentane, and HFC-134a.  In this study, with ventilation of only 48 cfm,
8-hr TWA exposure from the different chemicals varied from 35.5 ppm to
194.0 ppm, and all chemicals met their respective recommended exposure
levels (ICF, 2006a).  nPB exposure in similar ranges would be from two
to eleven times the WEL for nPB.  Thus, nPB would impose significantly
more risk to human health and the environment than other alternatives
available for this end use.

	C.	Adhesives

	EPA proposes to find nPB unacceptable in the adhesive end use.  As for
solvent cleaning and aerosols, we found that some alternative adhesive
formulations could reduce particular environmental risks more than nPB,
such as generation of ground level “smog” or ozone depletion
potential.  However, we find the greatest concern in this end use is
with nPB’s human health effects.  We propose to find nPB unacceptable
in adhesives because it increases overall impacts on human health and
the environment significantly more than other available alternatives.

   tc "		3.	Adhesives " \l 3 	Available information on exposure levels
during use of nPB-based adhesives indicates that it would be difficult
to meet a recommended exposure limit of 17 ppm.  Therefore, we believe
nPB poses a significantly greater risk than other available substitutes
in this end use.  For exposure to nPB when used in adhesives, NIOSH
investigators initially reported that mean exposures to nPB ranged from
60 to 381 ppm (8-hour time weighted averages) at three different
foam-fabrication facilities using nPB-based adhesives (NIOSH, 2000a,
2000b, 2001, 2002a, 2002b, 2003a).  In one facility, average (mean) nPB
exposures were reduced from 169 ppm to 19 ppm, following installation of
ventilation equipment recommended by NIOSH (NIOSH, 2000b).  Although use
of spray booths at this facility had a dramatic effect of reducing the
average exposure level to 19.4 ppm, individual exposures were still
excessive.  Eleven of fourteen sprayers (79%) and sixteen of all thirty
workers (53%) monitored continued to have exposures exceeding the
proposed WEL of 17 ppm.

	At another facility using nPB-based adhesives, the average exposure was
reduced from 58 pm to 19 ppm after the company installed ventilation