SEQ CHAPTER \h \r 1 ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 82

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

RIN 2060-AO10

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

Substances–n-Propyl Bromide in Solvent Cleaning

AGENCY:  Environmental Protection Agency.

ACTION:  Final Rule

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

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

ADDRESSES:  EPA has established a docket for this action under Docket ID
No. EPA-HQ-OAR-2002-0064.  All documents in the docket are listed on the
  HYPERLINK "http://www.regulations.gov"  www.regulations.gov  web site.
 Although listed in the index, some information is not publicly
available, i.e., Confidential Business Information (CBI) or other
information whose disclosure is restricted by statute.  Certain other
material, such as copyrighted material, is not placed on the Internet
and will be publicly available only in hard copy form.  Publicly
available docket materials are available either electronically in
HYPERLINK "http://www.regulations.gov"  www.regulations.gov  or in hard
copy at the Air and Radiation Docket, EPA/DC, EPA West, Room 3334, 1301
Constitution Ave., NW, Washington, DC.  This docket facility is open
from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal
holidays.  The telephone number for the Public Reading Room is (202)
566-1744, and the telephone number for the Air and Radiation Docket is
(202) 566-1742.

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

General Information

        Does this action apply to me?

	What is n-propyl bromide?

        What acronyms and abbreviations are used in the preamble?

How does the Significant New Alternatives Policy (SNAP) Program work?

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

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

	C.	How does the SNAP Program list our decisions?

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

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

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

		A.	Availability of alternatives to ozone-depleting substances

		B.	Impacts on the atmosphere and local air quality

		C.	Ecosystem and other environmental impacts

		D.	Flammability and fire safety

		E. 	Impact on human health

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

		A.	EPA’s acceptability decision

		B.	Toxicity

		C.	Ozone depletion potential

		D.	Other environmental impacts

		E.	Flammability

		F.	Legal authority to set exposure limits

VI. 	How can I use nPB as safely as possible? tc "VIII. 	 How can I use
nPB as safely as possible?"

VII.	Statutory and Executive Order Reviews

		A.  	Executive Order 12866:  Regulatory Planning and Review

B.  	Paperwork Reduction Act

C.  	Regulatory Flexibility Act

D.  	Unfunded Mandates Reform Act

E.  	Executive Order 13132:  Federalism

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

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

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

I.  	National Technology Transfer and Advancement Act

J. 	Congressional Review Act

VIII. 	References

I. 	General Information 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 final rule lists n-propyl bromide (nPB) as an acceptable
substitute when used as a solvent in industrial equipment for metals
cleaning, electronics cleaning, or precision cleaning.  General metals,
precision, and electronics cleaning includes cleaning with industrial
cleaning equipment such as vapor degreasers, in-line cleaning systems,
or automated equipment used for cleaning below the boiling point.  We
understand that nPB is used primarily for cleaning in vapor degreasers.
Manual cleaning, such as pail-and-brush, hand wipe, recirculating
over-spray (“sink-on-a-drum”) parts washers, immersion cleaning into
dip tanks with manual parts handling, and use of squirt bottles, is not
currently regulated under the SNAP program.  EPA also does not regulate
the use of solvents as carriers for flame retardants, dry cleaning, or
paint stripping under the SNAP program.

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

 Affected users under this final rule could include:

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

Businesses that manufacture electronics or computer equipment.

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

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

Category	NAICS code or subsector	Description of regulated entities

Industry	331	Primary Metal Manufacturing

Industry	332	Fabricated Metal Product Manufacturing

Industry	333	Machinery Manufacturing

Industry	334	Computer and Electronic Product Manufacturing

Industry	335	Equipment Appliance, and Component Manufacturing

Industry	336	Transportation Equipment Manufacturing

Industry	337	Furniture and Related Product Manufacturing

Industry	339	Miscellaneous Manufacturing

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

	B.	What is n-propyl bromide?

	n-propyl bromide (nPB), also called 1-bromopropane, is a non-flammable
organic solvent with a strong odor.  Its chemical formula is C3H7Br.
Its identification number in Chemical Abstracts Service’s registry
(CAS Reg. No.) is 106-94-5.  nPB is used to remove wax, oil, and grease
from electronics, metal, and other materials.  It also is used as a
carrier solvent in adhesives.  Some brand names of products using nPB
are:  Abzol®, EnSolv®, and Solvon® cleaners; Pow-R-Wash® NR Contact
Cleaner, Superkleen Flux Remover 2311 and LPS NoFlash NU Electro Contact
Cleaner aerosols; and Whisper Spray and Fire Retardant Soft Seam 6460
adhesives.

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

SIP–state implementation plan

SNAP–Significant New Alternatives Policy

STEL- Short term exposure limit

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

TCE—the chemical 1,1,2-trichloroethene, CAS Reg. No. 79-01-6, C2Cl3H;
also call trichloroethylene

TERA–Toxicological Excellence for Risk Assessment

TLV–Threshold Limit Value™

TSCA–Toxic Substances Control Act

TWA–time-weighted average

UMRA–Unfunded Mandates Reform Act

U.S.C.–United States Code

VMSs–volatile methyl siloxanes

VOC–volatile organic compound

WEL–workplace exposure limit

II.  	How does the Significant New Alternatives Policy (SNAP) program
work? 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 ODS in one of
the eight major industrial use sectors must provide the Agency with
health and safety studies on the substitute at least 90 days before
introducing it into interstate commerce for significant new use as an
alternative.  This requirement applies to the person planning to
introduce the substitute into interstate commerce, typically chemical
manufacturers, but may also include importers, formulators or end-users
when they are responsible for introducing a substitute into commerce.

C.	How does the SNAP program list our decisions?

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

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

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

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

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

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

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

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

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

for administering the SNAP program or criteria for evaluation of
substitutes, refer to the SNAP final rulemaking published in the Federal
Register on March 18, 1994 (59 FR 13044), codified at Code of Federal
Regulations at 40 CFR part 82, subpart G.  You can find a complete
chronology of SNAP decisions and the appropriate Federal Register
citations at http://www.epa.gov/ozone/snap/chron.html.

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

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

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

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

 Table 2: SOLVENT CLEANING

ACCEPTABLE SUBSTITUTE

End Use	Substitute	Decision	Further Information

Metals cleaning, electronics 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 would comply with any final
Permissible Exposure Limit that the Occupational Safety and Health
Administration issues in the future under 42 U.S.C. 7610(a).

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

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

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

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

	 EPA evaluated each of the criteria separately and then considered
overall risk to human health and the environment in comparison to other
available or potentially available alternatives.  We concluded that
overall, while there are a number of alternatives that reduce the risks
from ozone depletion or from smog production7 slightly more than nPB
when used in industrial solvent cleaning equipment, we found no single
alternative that could work in all applications that clearly would
reduce overall risks to human health and the environment in metals
cleaning, electronics cleaning, and precision cleaning.  Balancing the
different criteria discussed below, nPB used in solvent cleaning
end-uses does not pose a significantly greater risk than other
substitutes or than the ODS it is replacing in these end uses.  Thus, we
are listing nPB as acceptable in metals cleaning, electronics cleaning,
and precision cleaning.

A.	Availability of alternatives to ozone-depleting substances   tc
"Availability  " \l 3

	Other alternatives to methyl chloroform and CFC-113 are available for
metals, electronics, and precision cleaning that have already been found
acceptable or acceptable subject to use conditions under the SNAP
program including:  aqueous cleaners, semi-aqueous cleaners, alcohols,
ketones, esters, ethers, terpenes, HCFC-225ca/cb, hydrofluoroethers
(HFEs), hydrofluorocarbon (HFC)-4310mee, HFC-365mfc,
heptafluorocyclopentane, hydrocarbons, volatile methyl siloxanes (VMSs),
trans-1,2-dichloroethylene, methylene chloride, trichloroethylene (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 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). (IBSA, 2002)

	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.

The global warming potential (GWP) index is a means of quantifying the
potential integrated climate forcing of various greenhouse gases
relative to carbon dioxide.  Earlier data found a direct 100-year
integrated GWP (100yr GWP) for nPB of 0.31 (Atmospheric and
Environmental Research, Inc., 1995).  More recent analysis that
considers both the direct and the indirect GWP of nPB found a 100-yr GWP
of 1.57 (ICF, 2003a; ICF, 2006a).  In either case, the GWP for nPB is
comparable to or below that of previously approved substitutes in these
end uses.

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

	C.	Ecosystem and other environmental impacts  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 3).  Available data on the organic
carbon partition coefficient (Koc), the breakdown processes in water and
hydrolysis half-life, and the volatilization half-life indicate that nPB
is less persistent in the environment than many solvents and would be of
low to moderate concern for movement in soil.  Based on the LC50, the
acute concentration at which 50% of tested animals die, nPB’s toxicity
to aquatic life is moderate, being less than that for some acceptable
cleaners (for example, trichloroethylene, hexane, d-limonene, and
possibly some aqueous cleaners) and greater than that for some others
(methylene chloride, acetone, isopropyl alcohol, and some other aqueous
cleaners).  The LC50 for nPB is 67 mg/l, which is greater than 10 mg/l.
Based on EPA’s criteria for listing under the Toxics Release Inventory
(US EPA, 1992), we believe that nPB would not be sufficiently toxic to
aquatic life to warrant listing under the Toxics Release Inventory.
Based on its relatively low bioconcentration factor and log Kow value,
nPB is not prone to bioaccumulation.  Table 3 summarizes information on
environmental impacts of nPB; trans-1,2-dichloroethylene, a
commonly-used solvent in blends for aerosol solvents, precision
cleaning, and electronics cleaning; trichloroethylene, a solvent used
for metals, electronics, and precision cleaning; and methyl chloroform,
an ODS that nPB would replace.Table 3: Ecosystem and Other
Environmental Properties of nPB and Other Solvents

Property	Description of environmental property	Value for nPB	Value for
trans-1,2-dichloro-ethylene	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)	106 to
460 (Source:  ATSDR, 1997)	152 (Source: US EPA, 1994a)

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)	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)	3.4 hours to 18 days (Source:
ATSDR, 1997)	hours to weeks (Source: US EPA, 1994a)

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)	40.7 to 66.8 mg/L (Source:
 NPS, 1997)	52.8 to 105 mg/L (Source: US EPA, 1994a)

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)	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)	10 to 100 (Source:
ATSDR, 1997)	<9 (Source: US EPA, 1994a)

* Criteria from EDSTAC, 1998.

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

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

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

	E.	Impact on human health  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 because we
identified these groups of people as the ones likely to be exposed to
nPB when it is used as a substitute for ozone-depleting substances.  EPA
evaluated the available toxicity data using EPA guidelines to develop
health-based criteria to characterize human health risks (US EPA, 1994b.
RfC Guidelines; US EPA, 1991.  Guidelines for Developmental Toxicity
Risk Assessment; US EPA, 1995b.  Benchmark Dose guidelines; US EPA,
1996.  Guidelines for Reproductive Toxicity Risk Assessment).

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

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

Some general conclusions we draw from the new studies include:

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

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

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

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

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

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

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

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

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

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

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

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

The Occupational Safety and Health Administration (OSHA) has not
developed a permissible exposure limit (PEL) for nPB that EPA could use
to evaluate toxicity risks from workplace exposure.  In prior SNAP
reviews, EPA has used ACGIH TLVs where available in assessing a
chemical’s risks and determining its acceptability if OSHA has not set
a PEL.  ACGIH is recognized as an independent, scientifically
knowledgeable organization with expertise in issues of toxicity and
industrial hygiene.  However, in this case, EPA believes that ACGIH’s
TLV for nPB of 10 ppm has significant limitations as a reliable basis
for an acceptable exposure limit, especially given the availability of
other, more comprehensive analyses described in this proposalpreamble.
First, according to the authors of the Huntingdon Life Sciences study,
the decrease in fetal weight was an artifact of sampling procedure that
biased the data (test animals were only sacrificed at the end of the day
rather than at random).  The Center for the Evaluation of Risks to Human
Reproduction (CERHR) expert panel excluded “aberrantly low” fetal
weights from one litter in this study and calculated a BMDL greater than
300 ppm for this endpoint after removing those outlier data (CERHR,
2002a, 2003a, and 2004a).  TERA calculated a BMDL similar to that of the
CERHR expert panel when analyzing the same data set (TERA, 2004).
Further, the reference list in the documentation on the TLV indicates
that ACGIH did not review and evaluate all the studies available prior
to the development of the recommended exposure limit.  For example, key
supporting articles that reported disruption of estrous cycles (Yamada
et al., 2003 and Sekiguchi et al., 2002) were not discussed in the TLV
documentation.  Further, ACGIH did not provide sufficient reasoning for
the selection of the chosen endpoint over others (e.g., reproductive
toxicity and/or neurotoxicity).  The lack of discussion of applied
uncertainty factors also prevents a determination of how ACGIH arrived
at a TLV of 10 ppm.  In summary, EPA is not basing its proposed
acceptability determination for nPB on the ACGIH TLV because: (1) other
scientists evaluating the database for nPB did not find the reduced pup
weight to be the most sensitive endpoint; (2) BMD analysis of the
reduced pup weight data (CERHR, 2002a; TERA, 2004) results in a higher
BMDL (roughly 300 ppm) than those for sperm effects and estrous cycle
changes; and (3) ACGIH may not have reviewed the complete body of
literature as several studies discussing neurotoxicity and female
reproductive effects were omitted from the list of references.  A number
of reviews of this document are available in the public docket (ICF,
2004d; O’Malley, 2004).  Despite some flaws in its derivation, the TLV
of 10 ppm is less than two-fold lower than the low end of the range of
acceptable exposure levels based on the most sensitive reproductive
endpoints (see below).  This small difference is well within the
uncertainty we see when extrapolating a benchmark dose from an
experimental study in rats to an occupational exposure limit in humans.

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

Table 4: Summary of endpoints using benchmark response modeling

Endpointa	Study	BMDLb

(ppm)	Human Equivalent Concentration (HEC)c

(ppm)

Liver Effectsd

Liver vacuolation in males

(F1 offspring generation)	WIL, 2001 as analyzed in ICF, 2002	110

	116

Liver vacuolation in males  (F0 parent generation)	WIL, 2001 as analyzed
in ICF, 2002	143

	150

Liver vacuolation	ClinTrials, 1997b as analyzed in ICF, 2002 and
Stelljes & Wood, 2004	226

	170

Reproductive Effects—Male

Sperm motility (F1 offspring generation)

	WIL, 2001 as analyzed in ICF, 2002	169	177

	WIL, 2001 as analyzed in Stelljes & Wood, 2004	156	164

Sperm motility (F0 parent generation)

	WIL, 2001 as analyzed in ICF, 2002	282	296

	WIL, 2001 as analyzed in Stelljes & Wood, 2004	263	276

Prostate weight (F0 parent generation)	WIL, 2001 as analyzed in TERA,
2004	190	200

Sperm count 	Ichihara et al., 2000b as analyzed in Stelljes & Wood, 2004
232	325

Sperm deformities (F0 parent generation)	WIL, 2001 as analyzed in
Stelljes & Wood, 2004	296	311

Reproductive Effects—Female

Number of estrus cycles during a 3 week period (F0 parent generation)
WIL, 2001 as analyzed in ICF, 2006a	162	170

	WIL, 2001 as analyzed in ICF, 2006a	208 	218

Estrous cycle length (F1 offspring generation)d 	WIL, 2001 as analyzed
in TERA, 2004	400 	420

Estrous cycle length (F0 parent generation)e 	WIL, 2001 as analyzed in
TERA, 2004	210 	220

No estrous cycle incidence (F1 offspring generation)	WIL, 2001 as
analyzed in TERA, 2004	180	189

No estrous cycle incidence (F0 parent generation)	WIL, 2001 as analyzed
in TERA, 2004	480	504

Reproductive Effects—Reproductive Success

Decreased live litter size (F1 offspring generation)	WIL, 2001 as
analyzed in TERA, 2004	190	200

Decreased live litter size (F2 offspring generation)	WIL, 2001 as
analyzed in TERA, 2004	170	179

Pup weight gain, post-natal days 21 to 28 (F1 offspring generation)	WIL,
2001 as analyzed in TERA, 2004	180	189

Developmental Effects

Fetal body weight	WIL, 2001 as analyzed in TERA, 2004	310	326

Fetal body weight	WIL, 2001 as analyzed in CERHR, 2002a	305	320

Nervous System Effects

Hindlimb strength	Ichihara et al, 2000a as analyzed in Stelljes and
Wood, 2004	214	300

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

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

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

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

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

These more recent evaluations do not change EPA’s acceptability
determination for solvent cleaning.  As discussed below, users of
solvent cleaning equipment are reliably able to achieve exposure levels
well below our proposed AEL of 25 ppm in the June 2003 NPRM and
therefore we expect nPB users in the metals, electronics, and precision
cleaning end uses to be able to achieve acceptable exposure levels.
Concentrations of nPB emitted from industrial solvent cleaning equipment
were found to be below 25 ppm in roughly 88% of 500 samples on an 8-hr
time-weighted average, below 18 ppm in 81% of these samples, and below
10 ppm in roughly 70% of these samples (US EPA, 2003).

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

1.	Workplace Risks

 EPA believes that the great majority of users of nPB in metals
cleaning, electronics cleaning, and precision cleaning have been able to
attain exposure levels of well below 25 ppm, the proposed AEL in the
2003 NPRM, with their existing equipment.  Recently measured exposure
levels for nPB are much lower than historic exposure data from the 1970s
and 1980s for metals cleaning and electronics cleaning (ICF, 2006a);
this reflects both improvements in industrial hygiene practices and
improvements in cleaning equipment since 1994 spurred by the National
Emission Standard for Hazardous Air Pollutants for Halogenated Solvent
Cleaning (59 FR 61801).  Concentrations of nPB emitted from industrial
solvent cleaning equipment were found to be below 25 ppm in roughly 88%
of 500 samples on an 8-hr time-weighted average, below 18 ppm in 81% of
these samples, and below 10 ppm in roughly 70% of these samples (US EPA,
2003).

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

2.	General Population Risks

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

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

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

A. 	EPA’s acceptability decision

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

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

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

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

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

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

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

B.	Toxicity

	1.	Health Endpoints

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

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

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

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

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

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

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

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

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

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

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

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

3. 	Uncertainty Factors

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

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 BMD; or

An incomplete database of toxicity information exists for the chemical.

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

	Response:  EPA believes that two uncertainty factors are appropriate
for this database to account for (1) physiological differences between
humans and rats; and (2) variability within the working population.  EPA
RfC guidelines state that an uncertainty factor of 10 may be used for
potential differences between study animals and humans.  This factor of
10 consists in turn of two uncertainty factors of 3 – the first to
account for differences in pharmacodynamics 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, pp. 1-6, 4-73].  In
practice, EPA uses the square root of 10 when there are two or four
uncertainty factors of 3, yielding a total uncertainty factor of 10 or
100, and we use a value of 3 when multiplying by other uncertainty
factors.)  In general, EPA’s RfC guidelines state that for the
uncertainty factor extrapolating from animal to human data, “Use of a
3 is recommended with default dosimetric adjustments.” (US EPA, 1994b,
p. 4-73).  By EPA RfC guidelines (US EPA, 1994b), no adjustment for
differences in pharmacokinetics is necessary in this instance because
the blood/air partition coefficient for nPB in the human (7.1) is less
than in the rat (11.7), indicating that the delivered dose of nPB into
the bloodstream in rats is slightly higher than in humans.  EPA has seen
no data to indicate that (1) the toxicity is not directly related to the
inhaled parent compound in the arterial blood, or that (2) the critical
metabolic pathways do not scale across species, with respect to body
weight, in the same way as the ventilation rate.  Consistent with
Appendix J of EPA’s RfC guidelines for an inhaled compound that exerts
its effects through the bloodstream, EPA applies an uncertainty factor
of 1 for pharmacokinetics and an uncertainty factor of 3 for differences
between animals and humans.

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

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

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

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

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

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

4.	Other Analyses of nPB’s Toxicity

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

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

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

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

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

Drs. Rozman and Doull’s derivation of an AEL (II-D-63)—EPA discussed
our evaluation of this document at length in the preamble of the June
2003 NPRM at 68 FR 33298.  In particular, we disagree with Rozman and
Doull’s selection of the most sensitive endpoint.  Rozman and Doull
concluded that reproductive toxicity should not be considered the most
sensitive endpoint, stating that a National Institute for Occupational
Safety and Health (NIOSH) evaluation found that no human beings at a
facility using nPB-based adhesives experienced reproductive health
effects from the nPB.  However, the NIOSH study in fact concluded that
the survey questions would not be sufficient to determine if there were
reproductive health effects, which is significantly different from
saying that there was no health effect.  The expert panel for the CERHR
looked at the NIOSH report and a wide range of human and animal studies
on nPB; in contrast to Rozman and Doull, the expert panel concluded that
there was insufficient information on reproductive effects of nPB on
humans and that the results of tests on animals were considered
appropriate for evaluating potential reproductive health effects on
humans.

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

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

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

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

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

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

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

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

5.	Overall stringency of the acceptable exposure limit

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

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

	6.	Skin Absorption

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

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

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

	Rat studies indicate that dermal exposure to nPB results in neither
appreciable absorption through the skin (RTI, 2005) nor systemic
toxicity (Elf Atochem, 1995).  Unlike methyl chloride and dichlorvos,
which are absorbed through the skin and could contribute to systemic
toxicity (ACGIH, 1991), EPA is not including a skin notation for nPB in
the information provided to users associated with this rulemaking
because of the relatively low level of absorption.  The ACGIH provides
no skin notation in its TLV documentation for several solvents,
including nPB (ACGIH, 2005), methylene chloride, and perchloroethylene,
and there is no evidence that absorption through the skin is greater for
nPB than for the other halogenated compounds.  The TLV documentation for
nPB states, “There is no basis for a skin notation because the dermal
LD50 of 1-BP was >2 g/kg.”  Further, including a statement giving
advice about how to reduce skin exposure in the “Further
Information” column of listings is likely to be more informative to
workers than a skin notation.

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

7.	Iso-Propyl Bromide Limit

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

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

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

	8.	Short-term Exposure Limit (STEL)

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

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

	Response:     EPA disagrees that it is necessary to use a short-term
exposure limit in determining the acceptability of nPB in solvent
cleaning.  Acute, short-term exposures of nPB are not of significant
health concern, so long as long-term exposures are below the 8-hour TWA
limit (ERG, 2004).  EPA provided the STEL recommendation in the June
2003 proposal to give guidance to the user community, consistent with
the following recommendation of the American Conference of Governmental
Industrial Hygienists (ACGIH): “Excursions in worker exposure levels
may exceed 3 times the [threshold limit value] TLV-TWA for no more than
a total of 30 minutes during a workday” (ACGIH 1999).  We note that
when the ACGIH developed a TLV for nPB, they said there were no data to
support a short-term exposure limit (ACGIH, 2005).

	C.	Ozone depletion potential

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

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

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

	Comment:  Comments on the June 2003 NPRM expressed concern that other
countries, particularly those in equatorial regions, might assume that
nPB does not pose a danger to the stratospheric ozone layer if the U.S.
EPA’s SNAP program finds nPB acceptable (Linnell, 2003; Steminiski,
2003).

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

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

1. To request the Scientific Assessment Panel to update existing
information on the ozone depletion potential of n-propyl bromide,
including ozone depleting potential depending on the location of the
emissions and the season in the hemisphere at that location;

2. To request the Technology and Economic Assessment Panel to continue
its assessment of global emissions of n-propyl bromide, …paying
particular attention to:

(a) Obtaining more complete data on production and uses of n-propyl
bromide as well as emissions of n-propyl bromide from those sources;

(b) Providing further information on the technological and economical
availability of alternatives for the different use categories of
n-propyl bromide and information on the toxicity of and regulations on
the substitutes for n-propyl bromide;

(c) Presenting information on the ozone depletion potential of the
substances for which n-propyl bromide is used as a replacement;

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

	D.	Other environmental impacts

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

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

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

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

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

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

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

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

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

	E.	Flammability

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

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

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

F.	Legal authority to set exposure limits

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

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

	Although the Occupational Safety and Health Act (OSH Act) gives the
Occupational Safety and Health Administration (OSHA) authority to issue
a rule setting or revising an occupational safety or health standard (29
U.S.C. §655(b)), it does not prohibit other Federal agencies from
reviewing the safe level of exposure under other statutes that require
consideration of the human health and environmental effects of a
substance.  Conversely, although section 4(b)(1) of the OSH Act
prohibits OSHA from regulating a working condition addressed by another
federal agency’s regulations affecting occupational safety or health,
this provision is overridden with respect to EPA’s exercise of
authority under the Clean Air Act by 42 U.S.C. §7610.  That provision
states: “(a) Except as provided in subsection (b) of this section,
this chapter shall not be construed as superseding or limiting the
authorities and responsibilities, under any other provision of law, of
the Administrator or any other Federal officer, department, or
agency.”

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

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

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

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

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

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

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

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

	Response:  The commenter overstates the import of the decisions issued
by the Administrative Review Board.  In each of the cited decisions, the
Board examined the specific circumstances before it to determine which
statutory whistleblower provision provided the basis for the claimed
action.  While making general pronouncements that the CAA regulates
ambient air and OSHA regulates air within the workplace, none of these
opinions specifically addressed the scope of EPA’s authority under
section 612, the SNAP provisions of the Act.

	Comment:  A commenter stated that even if ventilation or other measures
could reduce exposures to below 25 ppm, there is nothing to ensure that
companies will take such measures.  This commenter also stated that he
is aware of nPB formulators that have already announced they will not
adhere to this voluntary standard.  Three commenters, all representing
local environmental regulators, stated that a recommendation that worker
exposure be limited to 25 ppm will not carry the enforcement powers of
an OSHA standard, and that this lack of control will encourage the use
of nPB in applications beyond those envisioned by EPA.  Another
commenter asserted that the proposed exposure limits (both the AEL and
the STEL) should be established as use conditions, citing Section 612 as
the basis for EPA’s authority to do so.  This commenter stated that a
precedent has already been set for EPA to accept an alternative chemical
subject to use conditions—including that observance of workplace
concentration limits—in the adhesives, aerosols, and solvent cleaning
sectors (e.g., HCFC-225 ca/cb, HFC-4310mee, monochlorotoluenes,
benzotrifluorides; 40 CFR part 82, subpart G, appendices A, B, and D).

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

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

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

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

VI. 	How can I use nPB as safely as possible? tc "VIII. 	 How can I use
nPB as safely as possible?"

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

All end uses

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

Limit worker exposure to solvents to minimize any potential adverse
health effects.  Workers should avoid staying for long periods of time
in areas near where they have been using the solvent.  Where possible,
shorten the period during each day when a worker is exposed.  Where
respiratory protection is necessary to limit worker exposures,
respirators must be selected and used in accordance with OSHA’s
Respiratory Protection standard, 29 CFR 1910.134.

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

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

Workers should receive safety training and education that includes