30168 Federal Register / Vol. 72, No. 103 / Wednesday, May 30, 2007 / Proposed Rules 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 82 

[EPA–HQ–OAR–2002–0064; FRL–8316–7] 

RIN 2060–AK26 

Protection of Stratospheric Ozone: 

Listing of Substitutes for OzoneDepleting Substances—n-Propyl 

Bromide in Adhesives, Coatings, and 

Aerosols 

AGENCY: Environmental Protection 

Agency. 

ACTION: Notice of Proposed Rulemaking. 

SUMMARY: Pursuant to the U.S. 

Environmental Protection Agency’s 

(EPA or ‘‘we’’) Significant New 

Alternatives Policy (SNAP) program, 

this action proposes to list n-propyl 

bromide (nPB) as an unacceptable 

substitute for methyl chloroform, 

chlorofluorocarbon (CFC)–113, and 

hydrochlorofluorocarbon (HCFC)–141b 

when used in adhesives or in aerosol 

solvents because nPB in these end uses 

poses unacceptable risks to human 

health when compared with other 

substitutes that are available. In 

addition, EPA takes comment on 

alternate options that would find nPB 

acceptable subject to use conditions in 

adhesives or in aerosol solvents. This 

action also proposes to list nPB as 

acceptable, subject to use conditions, as 

a substitute for methyl chloroform, 

CFC–113, and hydrochlorofluorocarbon 

(HCFC)–141b in the coatings end use. 

This proposal supersedes EPA’s 

proposal of June 3, 2003 on the 

acceptability of nPB as a substitute for 

ozone-depleting substances for aerosols 

and adhesives. 

DATES: Comments must be received in 

writing by July 30, 2007. Under the 

Paperwork Reduction Act, comments on 

the information collection provisions 

must be received by the Office of 

Management and Budget (OMB) on or 

before June 29, 2007. Any person 

interested in requesting a public 

hearing, must submit such request on or 

before June 29, 2007. If a public hearing 

is requested, a separate notice will be 

published announcing the date and time 

of the public hearing and the comment 

period will be extended until 30 days 

after the public hearing to allow rebuttal 

and supplementary information 

regarding any material presented at the 

public hearing. Inquiries regarding a 

public hearing should be directed to the 

contact person listed below. 

ADDRESSES: Submit your comments, 

identified by Docket ID No. EPA–HQ– 

OAR–2002–0064, by one of the 

following methods: 

• http://www.regulations.gov. Follow 

the on-line instructions for submitting 

comments. 

• E-mail: A-And-R-Docket@epa.gov. 

• Mail: Air and Radiation Docket, 

Environmental Protection Agency, 

Mailcode 6102T, 1200 Pennsylvania 

Ave., NW., Washington DC 20460, 

Attention Docket ID No. EPA–HQ– 

OAR–2002–0064. In addition, please 

mail a copy of your comments on the 

information collection provisions to the 

Office of Information and Regulatory 

Affairs, Office of Management and 

Budget (OMB), Attn: Desk Officer for 

EPA, 725 17th St., NW., Washington, DC 

20503. 

• Hand Delivery: EPA Docket Center, 

(EPA/DC) EPA West, Room 3334, 1301 

Constitution Ave., NW., Washington, 

DC, Attention Docket ID No. EPA–HQ– 

OAR–2002–0064. Such deliveries are 

only accepted during the Docket’s 

normal hours of operation, and special 

arrangements should be made for 

deliveries of boxed information. 

Instructions: Direct your comments to 

Docket ID No. EPA–HQ–OAR–2002– 

0064. EPA’s policy is that all comments 

received will be included in the public 

docket without change and may be 

made available online at http:// 

www.regulations.gov, including any 

personal information provided, unless 

the comment includes information 

claimed to be Confidential Business 

Information (CBI) or other information 

whose disclosure is restricted by statute. 

Do not submit information that you 

consider to be CBI or otherwise 

protected through www.regulations.gov 

or e-mail. The http:// 

www.regulations.gov Web site is an 

‘‘anonymous access’’ system, which 

means EPA will not know your identity 

or contact information unless you 

provide it in the body of your comment. 

If you send an e-mail comment directly 

to EPA without going through http:// 

www.regulations.gov, your e-mail 

address will be automatically captured 

and included as part of the comment 

that is placed in the public docket and 

made available on the Internet. If you 

submit an electronic comment, EPA 

recommends that you include your 

name and other contact information in 

the body of your comment and with any 

disk or CD–ROM you submit. If EPA 

cannot read your comment due to 

technical difficulties and cannot contact 

you for clarification, EPA may not be 

able to consider your comment. 

Electronic files should avoid the use of 

special characters, any form of 

encryption, and be free of any defects or 

viruses. For additional instructions on 

submitting comments, go to Section I.B. 

of the SUPPLEMENTARY INFORMATION

section of this document. 

Docket: All documents in the docket 

are listed in the http:// 

www.regulations.gov index. Although 

listed in the index, some information is 

not publicly available, i.e., CBI or other 

information whose disclosure is 

restricted by statute. Certain other 

material, such as copyrighted material, 

is not placed on the Internet and will be 

publicly available only in hard copy 

form. Publicly available docket 

materials are available either 

electronically in http:// 

www.regulations.gov or in hard copy at 

the Air and Radiation Docket, EPA/DC, 

EPA West, Room 3334, 1301 

Constitution Ave., NW., Washington, 

DC. The Public Reading Room is open 

from 8:30 a.m. to 4:30 p.m., Monday 

through Friday, excluding legal 

holidays. The telephone number for the 

Public Reading Room is (202) 566–1744, 

and the telephone number for the Air 

and Radiation Docket is (202) 566–1742. 

FOR FURTHER INFORMATION CONTACT: 

Margaret Sheppard, Stratospheric 

Protection Division, Office of 

Atmospheric Programs, Mail Code 

6205J, Environmental Protection 

Agency, 1200 Pennsylvania Ave., NW., 

Washington, DC 20460; telephone 

number (202) 343–9163; fax number 

(202) 343–2362 e-mail address: 

sheppard.margaret@epa.gov. Notices 

and rulemakings under the SNAP 

program are available on EPA’s 

Stratospheric Ozone World Wide Web 

site at http://www.epa.gov/ozone/snap/ 

regs. 

SUPPLEMENTARY INFORMATION: 

Table of Contents 

I. General Information 

A. Does this action apply to me? 

B. What should I consider as I prepare my 

comments for EPA? 

C. What acronyms and abbreviations are 

used in the preamble? 

II. How does the Significant New 

Alternatives Policy (SNAP) program 

work? 

A. What are the statutory requirements and 

authority for the SNAP program? 

B. How do the regulations for the SNAP 

program work? 

C. Where can I get additional information 

about the SNAP program? 

III. What is EPA proposing today? 

A. What is n-propyl bromide? 

B. What industrial end uses are included 

in our proposed decision? 

C. What is the proposed text for EPA’s 

listing decisions? 

D. What does an unacceptability 

determination on adhesives and aerosols 

mean? 

E. What is the scope of the proposed 

determination for coatings? 


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IV. What criteria did EPA consider in 

preparing this proposal? 

A. Availability of Alternatives to OzoneDepleting Substances 

B. Impacts on the Atmosphere and Local 

Air Quality 

C. Ecosystem and Other Environmental 

Impacts 

D. Flammability and Fire Safety 

E. Health impacts and exposure 

V. How did EPA assess impacts on human 

health? 

A. Newly Available Exposure Data 

B. Newly Available Data on Health Effects 

C. Evaluation of Acceptable Exposure 

Levels for the Workplace 

D. Other Analyses of nPB Toxicity 

E. Community Exposure Guideline 

VI. What listing is EPA proposing for each 

end use, and why? 

A. Aerosol Solvents 

B. Adhesives 

C. Coatings 

VII. What other regulatory options did EPA 

consider? 

A. Alternative Option for Comment: 

Acceptable With Use Conditions 

Requiring Exposure Limit and 

Monitoring 

B. Regulatory Options Where nPB Would 

Be Acceptable With Use Conditions 

Requiring Specific Equipment 

VIII. What are the anticipated costs of this 

regulation to the regulated community? 

IX. How do the decisions for EPA’s June 2003 

proposal compare to those for this 

proposal? 

X. How can I use nPB as safely as possible? 

XI. 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 

XII. References 

I. General Information 

A. Does this action apply to me? 

This proposed rule would regulate the 

use of n-propyl bromide as an aerosol 

solvent and as a carrier solvent in 

adhesives and coatings. Businesses in 

these end uses that currently might be 

using nPB, or might want to use it in the 

future, include: 

• Businesses that manufacture 

electronics or computer equipment. 

• Businesses that require a high level 

of cleanliness in removing oil, grease, or 

wax, such as for aerospace applications 

or for manufacture of optical equipment. 

• Foam fabricators that glue pieces of 

polyurethane foam together or foam 

cushion manufacturers that glue fabric 

around a cushion. 

• Furniture manufacturers that use 

adhesive to attach wood parts to floors, 

tables and counter tops. 

• A company that manufactures 

ammunition for the U.S. Department of 

Defense. Regulated entities may include: 

TABLE 1.—POTENTIALLY REGULATED ENTITIES, BY NORTH AMERICAN INDUSTRIAL CLASSIFICATION SYSTEM (NAICS) 

CODE OR SUBSECTOR

Category NAICS code 

or subsector Description of regulated entities 

Industry ..................................................... 331 Primary Metal Manufacturing. 

Industry ..................................................... 332 Fabricated Metal Product Manufacturing. 

Industry/Military ......................................... 332992 Small Arms Ammunition Manufacturing. 

Industry ..................................................... 333 Machinery Manufacturing. 

Industry ..................................................... 334 Computer and Electronic Product Manufacturing. 

Industry ..................................................... 335 Equipment Appliance, and Component Manufacturing. 

Industry ..................................................... 336 Transportation Equipment Manufacturing. 

Industry ..................................................... 337 Furniture and Related Product Manufacturing. 

Industry ..................................................... 339 Miscellaneous Manufacturing. 

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

This table is not intended to be 

exhaustive, but rather a guide regarding 

entities likely to be regulated by this 

action. If you have any questions about 

whether this action applies to a 

particular entity, consult the person 

listed in the preceding section, FOR

FURTHER INFORMATION CONTACT. 

B. What should I consider as I prepare 

my comments for EPA? 

1. Submitting Confidential Business 

Information (CBI). Do not submit this 

information to EPA through 

www.regulations.gov or e-mail. Clearly 

mark the part or all of the information 

that you claim to be CBI. For CBI 

information in a disk or CD ROM that 

you mail to EPA, mark the outside of the 

disk or CD ROM as CBI and then 

identify electronically within the disk or 

CD ROM the specific information that is 

claimed as CBI. In addition to one 

complete version of the comment that 

includes information claimed as CBI, a 

copy of the comment that does not 

contain the information claimed as CBI 

must be submitted for inclusion in the 

public docket. Information so marked 

will not be disclosed except in 

accordance with procedures set forth in 

40 CFR part 2. 

2. Tips for Preparing Your Comments. 

When submitting comments, remember 

to: 

• Identify the rulemaking by docket 

number and other identifying 

information (subject heading, Federal 

Register (FR) date and page number). 

• Follow directions—The agency may 

ask you to respond to specific questions 

or organize comments by referencing a 

Code of Federal Regulations (CFR) part 

or section number. 

• Explain why you agree or disagree; 

suggest alternatives and substitute 

language for your requested changes. 

• Describe any assumptions and 

provide any technical information and/ 

or data that you used. 

• If you estimate potential costs or 

burdens, explain how you arrived at 

your estimate in sufficient detail to 

allow for it to be reproduced. 

• Provide specific examples to 

illustrate your concerns, and suggest 

alternatives. 

• Explain your views as clearly as 

possible, avoiding the use of profanity 

or personal threats. 

• Make sure to submit your 

comments by the comment period 

deadline identified. 

C. What acronyms and abbreviations are 

used in the preamble? 

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 


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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–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-dichloro1,1,2,2,3-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 

NIOSH—National Institute for Occupational 

Safety and Health 

NOAEL—No Observed Adverse Effect Level 

NOEL—No Observed Effect Level 

nPB—ln-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 

TCA—the ozone-depleting chemical 1,1,1- 

trichloroethane, CAS Reg. No. 71–55–6; 

also called methyl chloroform, MCF, or 

1,1,1 

TCE—the chemical 1,1,2-trichloroethene, 

CAS Reg. No. 79–01–6, C2Cl3H; also call 

trichloroethylene 

TERA—Toxicological Excellence for Risk 

Assessment 

TLV—Threshold Limit Value(tm) 

TSCA—Toxic Substances Control Act 

TWA—time-weighted average 

UMRA—Unfunded Mandates Reform Act 

U.S.C.—United States Code 

VMSs—volatile methyl siloxanes 

VOC—volatile organic compound 

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 ozonedepleting substance (ODS) in one of the 

eight major industrial use sectors must 

provide the Agency with health and 

safety studies on the substitute at least 

90 days before introducing it into 


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1CFC–113 is also referred to as Freon-113, or 

1,1,2-trifluoro-1,2,2-trichloroethane. Its CAS Reg. 

No. is 76–13–1. 

2Methyl chloroform is also referred to as 1,1,1- 

trichloroethane, TCA, MCF, or 1,1,1. Its CAS Reg. 

No. is 71–55–6. 

3HCFC–141b is also referred to as 1,1-dichloro1-fluoroethane. Its CAS Reg. No. is 1717–00–6. 

interstate commerce for significant new 

use as an alternative. This requirement 

applies to the person planning to 

introduce the substitute into interstate 

commerce, typically chemical 

manufacturers, but may also include 

importers, formulators or end-users 

when they are responsible for 

introducing a substitute into commerce. 

The Agency has identified four 

possible decision categories for 

substitutes: Acceptable; acceptable 

subject to use conditions; acceptable 

subject to narrowed use limits; and 

unacceptable. Use conditions and 

narrowed use limits are both considered 

‘‘use restrictions’’ and are explained 

below. Substitutes that are deemed 

acceptable with no use restrictions (no 

use conditions or narrowed use limits) 

can be used for all applications within 

the relevant sector end-use. Substitutes 

that are acceptable subject to use 

restrictions may be used only in 

accordance with those restrictions. It is 

illegal to replace an ODS with a 

substitute listed as unacceptable. 

After reviewing a substitute, the 

Agency may make a determination that 

a substitute is acceptable only if certain 

conditions of use are met to minimize 

risks to human health and the 

environment. We describe such 

substitutes as ‘‘acceptable subject to use 

conditions.’’ If you use these substitutes 

without meeting the associated use 

conditions, you use these substitutes in 

an unacceptable manner and you could 

be subject to enforcement for violation 

of section 612 of the Clean Air Act. 

For some substitutes, the Agency may 

permit a narrowed range of use within 

a sector. For example, we may limit the 

use of a substitute to certain end-uses or 

specific applications within an industry 

sector or may require a user to 

demonstrate that no other acceptable 

end uses are available for their specific 

application. We describe these 

substitutes as ‘‘acceptable subject to 

narrowed use limits.’’ If you use a 

substitute that is acceptable subject to 

narrowed use limits, but use it in 

applications and end-uses which are not 

consistent with the narrowed use limit, 

you are using these substitutes in an 

unacceptable manner and you could be 

subject to enforcement for violation of 

section 612 of the Clean Air Act. 

The Agency publishes its SNAP 

program decisions in the Federal 

Register. For those substitutes that are 

deemed acceptable subject to use 

restrictions (use conditions and/or 

narrowed use limits), or for substitutes 

deemed unacceptable, we first publish 

these decisions as proposals to allow the 

public opportunity to comment, and we 

publish final decisions as final 

rulemakings. In contrast, we publish 

substitutes that are deemed acceptable 

with no restrictions in ‘‘notices of 

acceptability,’’ rather than as proposed 

and final rules. As described in the rule 

implementing the SNAP program (59 FR 

13044), we do not believe that 

rulemaking procedures are necessary to 

list alternatives that are acceptable 

without restrictions because such 

listings neither impose any sanction nor 

prevent anyone from using a substitute. 

Many SNAP listings include 

‘‘comments’’ or ‘‘further information.’’

These statements provide additional 

information on substitutes that we 

determine are unacceptable, acceptable 

subject to narrowed use limits, or 

acceptable subject to use conditions. 

Since this additional information is not 

part of the regulatory decision, these 

statements are not binding for use of the 

substitute under the SNAP program. 

However, regulatory requirements listed 

in this column are binding under other 

programs. The further information does 

not necessarily include all other legal 

obligations pertaining to the use of the 

substitute. However, we encourage users 

of substitutes to apply all statements in 

the ‘‘Further Information’’ column in 

their use of these substitutes. In many 

instances, the information simply refers 

to sound operating practices that have 

already been identified in existing 

industry and/or building-code 

standards. Thus, many of the comments, 

if adopted, would not require the 

affected industry to make significant 

changes in existing operating practices. 

C. Where can I get additional 

information about the SNAP program? 

For copies of the comprehensive 

SNAP lists of substitutes or additional 

information on SNAP, look at EPA’s 

Ozone Depletion World Wide Web site 

at http://www.epa.gov/ozone/snap/lists/ 

index.html. For more information on the 

Agency’s process for administering the 

SNAP program or criteria for evaluation 

of substitutes, refer to the SNAP final 

rulemaking published in the Federal 

Register on March 18, 1994 (59 FR 

13044), codified at Code of Federal 

Regulations at 40 CFR part 82, subpart 

G. You can find a complete chronology 

of SNAP decisions and the appropriate 

Federal Register citations at http:// 

www.epa.gov/ozone/snap/chron.html. 

III. What is EPA proposing today? 

In this action, EPA proposes to list npropyl bromide (nPB) as (1) 

unacceptable for use as a substitute for 

CFC–113,1 methyl chloroform 2 and 

HCFC–141b 3 in the adhesive and 

aerosol solvent end uses; and (2) 

acceptable subject to use conditions 

(limited to coatings at facilities that, as 

of May 30, 2007, have provided EPA 

with information demonstrating their 

ability to maintain acceptable workplace 

exposures) as a substitute for methyl 

chloroform, CFC–113, and HCFC–141b 

in the coatings end use. This Notice of 

Proposed Rulemaking (NPRM) 

supersedes the NPRM published on 

June 3, 2003 (68 FR 33284) for aerosol 

solvents and adhesives. 

A. 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. 

B. What industrial end uses are 

included in our proposed decision? 

This proposal addresses the use of npropyl bromide in the aerosol solvent 

end use of the aerosol sector and the 

adhesives and coatings end uses in the 

adhesives, coatings, and inks sector as 

discussed below. EPA is issuing a 

decision on the use of nPB in metals, 

electronics, and precision cleaning in a 

separate final rule. EPA has insufficient 

information for ruling on other end uses 

or sectors where nPB might be used 

(e.g., inks, foam blowing, fire 

suppression). 

1. Aerosol Solvents 

We understand that nPB is being used 

as an aerosol solvent in: 

• Lubricants, coatings, or cleaning 

fluids for electrical or electronic 

equipment; 

Lubricants, coatings, or cleaning 

fluids for aircraft maintenance; or 


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• Spinnerrette lubricants and 

cleaning sprays used in the production 

of synthetic fibers. 

2. Adhesives 

Types of adhesives covered under the 

SNAP program are those that formerly 

used methyl chloroform, specifically, 

adhesives for laminates, flexible foam, 

hardwood floors, tire patches, and metal 

to rubber adhesives. Of these 

applications, nPB-based adhesives have 

been used most widely in spray 

adhesives used in manufacture of foam 

cushions, and to a lesser degree in 

laminate adhesives. 

3. Coatings 

The SNAP program regulates the use 

of carrier solvents in durable coatings, 

including paints, varnishes, and 

aerospace coatings (59 FR 13118). The 

SNAP program currently does not 

regulate carrier solvents in lubricant 

coatings, such as silicone coatings used 

on medical equipment (59 FR 13119). 

Methyl chloroform has been used as a 

carrier solvent in coatings, and to a 

much lesser degree, HCFC–141b also 

has been a carrier solvent. This rule 

responds to a submission from a facility 

that is substituting methyl chloroform 

with nPB as an ammunition coating 

(sealant). 

C. What is the proposed text for EPA’s 

listing decisions? 

In the proposed regulatory text at the 

end of this document, you will find our 

proposed decisions for those end uses 

for which we have proposed nPB as 

unacceptable or acceptable subject to 

use conditions. The proposed 

conditions listed in the ‘‘Use 

Conditions’’ column would be 

enforceable while information 

contained in the ‘‘Further Information’’

column of those tables provides 

additional recommendations on the safe 

use of nPB. Our proposed decisions for 

each end use are summarized below in 

tables 2 through 4. 

Proposed Listings 

TABLE 2.—AEROSOLS PROPOSED UNACCEPTABLE SUBSTITUTES

End Use Substitute Decision Further information 

Aerosol solvents .......... n-propyl bromide (nPB) as a substitute for 

CFC–113, HCFC–141b, and methyl chloroform.

Unacceptable ............. EPA finds unacceptable risks to human 

health in this end use compared to other 

available alternatives. nPB, also known as 

1-bromopropane, is Number 106–94–5 in 

the CAS Registry. 

TABLE 3.—ADHESIVES, COATINGS, AND INKS PROPOSED UNACCEPTABLE SUBSTITUTES

Enduse Substitute Decision Further information 

Adhesives .................... n-propyl bromide (nPB) as a substitute for 

CFC–113, HCFC–141b, and methyl chloroform.

Unacceptable ............. EPA finds unacceptable risks to human 

health in this end use compared to other 

available alternatives. nPB, also known as 

1-bromopropane, is Number 106–94–5 in 

the CAS Registry. 

TABLE 4.—ADHESIVES, COATINGS, AND INKS SUBSTITUTES THAT ARE PROPOSED ACCEPTABLE SUBJECT TO USE

CONDITIONS

End Use Substitute Decision Use conditions Further information 

Coatings ......... n-propyl bromide 

(nPB) as a substitute for methyl 

chloroform, CFC113, and HCFC141b.

Acceptable subject 

to use conditions.

Use is limited to coatings facilities that, 

as of May 30, 2007, have provided 

EPA information demonstrating their 

ability to maintain acceptable workplace exposures.

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 CAS Registry. 

Note: As of May 30, 2007, the Lake City Army Ammunition Plant is the only facility using nPB in coatings that has provided information to EPA 

that meets this condition. 

D. What does an unacceptability 

determination on adhesives and 

aerosols mean? 

In this action, EPA is proposing to 

find nPB unacceptable as a substitute 

for methyl chloroform, CFC–113, and 

HCFC–141b for use as a carrier solvent 

in adhesives and as an aerosol solvent. 

If this proposal were to become final, it 

would be illegal to use nPB or blends of 

nPB and other solvents in adhesives or 

in aerosol solvent formulations as a 

substitute for ozone-depleting 

substances. 

E. What is the scope of the proposed 

determination for coatings? 

We propose to list nPB as an 

acceptable substitute, subject to use 

conditions, for methyl chloroform, CFC–

113, and HCFC–141b in coatings for 

facilities that, as of May 30, 2007, have 


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4Also called trichlorethene or TCE, C2Cl3H, CAS 

Reg. No. 79–01–6. 

5Also called PERC, tetrachloroethylene, or 

tetrachloroethene, C2Cl4, CAS Reg. No. 127–18–4. 

provided EPA information 

demonstrating their ability to maintain 

acceptable workplace exposures. EPA 

has received a petition to allow use of 

nPB for the ammunition coating 

application at Lake City Army 

Ammunition Plant. This is the only 

coatings application or facility for 

which EPA has exposure and usage data 

demonstrating an ability to maintain 

workplace exposure levels below even 

the minimum level of the range of 

exposures that EPA is considering to be 

potentially acceptable (i.e., 17 to 30 

ppm) (see section IV.E for an evaluation 

of the health risks associated with nPB). 

If other facilities are interested in using 

nPB as a substitute for methyl 

chloroform, CFC–113, or HCFC–141b in 

their coatings application, or if a person 

wishes to market nPB for such use, then 

the interested party would need to make 

a submission under the SNAP program. 

IV. What criteria did EPA consider in 

preparing this 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 groundlevel 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 or spray adhesives used in 

foam fabrication. In those consumer 

products made using nPB, such as a 

piece of furniture or a computer, the 

nPB would have evaporated long before 

a consumer would purchase the item. 

Therefore, we believe there is no 

consumer exposure risk to evaluate in 

the end uses we evaluated for this rule. 

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 

carrier solvent in adhesives to other 

available or potentially available 

adhesive alternatives. 

Although EPA does not judge the 

effectiveness of an alternative for 

purposes of determining whether it is 

acceptable, we consider effectiveness 

when determining whether alternatives 

that pose less risk are available in a 

particular application within an end 

use. There are a wide variety of 

acceptable alternatives listed for aerosol 

solvents, but not all may be appropriate 

for a specific application because of 

differences in materials compatibility, 

flammability, degree of cleanliness 

required, local environmental 

requirements, and other factors. 

EPA evaluated each of the criteria 

separately and then considered overall 

risk to human health and the 

environment in comparison to other 

available or potentially available 

alternatives. We concluded that overall, 

environmental risks were not sufficient 

to find nPB unacceptable in any of the 

evaluated end uses. However, the 

overall risks to human health, and 

particularly the risks to worker health, 

are sufficiently high in the adhesive and 

aerosol solvent end uses to warrant our 

proposal to find nPB unacceptable. 

A. Availability of Alternatives to OzoneDepleting Substances 

Other alternatives are available in 

each end use considered in this 

proposal. Examples of other available 

alternatives for aerosol solvents that 

have already been found acceptable or 

acceptable subject to use conditions 

under the SNAP program include waterbased formulations, alcohols, ketones, 

esters, ethers, terpenes, HCFC–141b, 

HCFC–225ca/cb, hydrofluoroethers 

(HFEs), hydrofluorocarbon (HFC)–

4310mee, HFC–365mfc, HFC–245fa, 

hydrocarbons, trans-1,2- 

dichloroethylene, methylene chloride, 

trichloroethylene 4 (TCE), 

perchloroethylene 5, and 

parachlorobenzotrifluoride (PCBTF). Of 

these, hydrocarbons, alcohols, blends of 

trans-1,2-dichloroethylene and HFEs or 

HFCs, and HCFC–225ca/cb are most 

likely to be used in the same 

applications as nPB. nPB is already 

commercially available in aerosols. Its 

use is primarily for electrical contact 

cleaning, with some use for benchtop 

cleaning applications (Williams, 2005). 

Many alternatives are also available 

for use in adhesives, coatings, and inks: 

Water-based formulations, high solid 

formulations, alcohols, ketones, esters, 

ethers, terpenes, HFEs, hydrocarbons, 

trans-1,2-dichloroethylene, chlorinated 

solvents, PCBTF, and a number of 

alternative technologies (e.g., powder, 

hot melt, thermoplastic plasma spray, 

radiation-cured, moisture-cured, 

chemical-cured, and reactive liquid). Of 

these, the alternative adhesives most 

likely to be used in the same 

applications as nPB are water-based 

formulations, adhesives with methylene 

chloride, and flammable adhesives with 

acetone (IRTA, 2000). nPB is already 

used in adhesives, and particularly in 

foam fabrication and in constructing 

seating for aircraft (IRTA, 2000; 

Seilheimer, 2001). 

To our knowledge, nPB is potentially 

available as a carrier solvent in coatings, 

but has not yet been commercialized, 

except for use by one facility, the Lake 

City Army Ammunition Plant. The Lake 

City Army Ammunition Plant evaluated 

twenty-nine carrier solvent alternatives 

to methyl chloroform and determined 

that nPB is the only satisfactory 

alternative for their application given 

the current process at that facility 

(Harper, 2005). 

B. Impacts on the Atmosphere and 

Local Air Quality 

As discussed in the June, 2003 

proposal, nPB emissions from the 

continental United States are estimated 

to have an ozone depletion potential 

(ODP) of approximately 0.013–0.018, 

(Wuebbles, 2002), 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 as 

an aerosol solvent. There are other 

acceptable solvents for aerosols, 

adhesives, and coatings that essentially 

have no ODP—aqueous cleaners, HFEs, 

HFC–4310mee, HFC–365mfc, HFC–

245fa, hydrocarbons, volatile methyl 

siloxanes (VMSs), methylene chloride, 

TCE, perchloroethylene, and PCBTF. 


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6nPB emissions in the tropics have an ODP of 

0.071 to 0.100; the portions of the U.S. outside the 

continental U.S., such as Alaska, Hawaii, Guam, 

and the U.S. Virgin Islands, contain less than 1 

percent of the U.S.’s businesses in industries that 

could use nPB. Thus, their potential impact on the 

ozone layer must be significantly less than that of 

the already low impact from nPB emissions in the 

continental U.S. (U.S. Economic Census, 2002a 

through f). 

Based on this information, we do not 

believe the use of nPB within the U.S., 

and within the end-uses reviewed in 

this rulemaking, poses a significantly 

greater risk to the ozone layer than other 

available substitutes. 

Comments on the June 2003 NPRM 

expressed concern that other countries, 

particularly those in equatorial regions, 

might assume that nPB does not pose a 

danger to the stratospheric ozone layer 

if the U.S. EPA’s SNAP program finds 

nPB acceptable (Linnell, 2003; 

Steminiski, 2003). Because the ODP for 

nPB is higher when used in the tropics,6

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. 

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, 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 twentyseventh meeting of the Open-ended 

Working Group for the consideration of 

the Nineteenth Meeting of the Parties. 

(MOP 18, 2006) 

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 nonattainment 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 VOCexempt solvents that are acceptable ODS 

substitutes include HFC–245fa, HCFC–

225ca/cb, HFC–365mfc and HFC–

4310mee for aerosol solvents, and 

methylene chloride, perchloroethylene, 

HFE–7100, HFE–7200, PCBTF, acetone, 

and methyl acetate for aerosol solvents, 

adhesives, and coatings. 

C. Ecosystem and Other Environmental 

Impacts 

EPA considered the possible impacts 

of nPB if it were to pollute soil or water 

as a waste and compared these impacts 

to screening criteria developed by the 

Endocrine Disruptor Screening and 

Testing Advisory Committee (EDSTAC, 

1998) (see Table 5). 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 

milligrams per liter (mg/l), which is 

greater and thus less toxic than an LC50

of 10 mg/l, one of EPA’s criteria for 

listing under the Toxics Release 

Inventory (US EPA, 1992; ICF, 2004a). 

Based on its relatively low 

bioconcentration factor and log Kow

value (logarithm of the octanol-water 

partition coefficient), nPB is not prone 

to bioaccumulation. Table 5 summarizes 

information on environmental impacts 

of nPB; trans-1,2-dichloroethylene, a 

commonly-used solvent in blends for 

aerosol solvents, precision cleaning, and 

electronics cleaning; acetone, a 

commonly-used carrier solvent in 

adhesives; trichloroethylene, a solvent 

used for metals, electronics, and 

precision cleaning that could potentially 

be used in aerosol or adhesive end-uses; 

and methyl chloroform, an ODS that 

nPB would replace. 


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TABLE 5.—ECOSYSTEM AND OTHER ENVIRONMENTAL PROPERTIES OF nPB AND OTHER SOLVENTS

Property 

Description of environmental property 

Value for nPB 

Value for trans1,2-dichloro-ethylene 

Value for acetone Value for 

trichloroethylene 

Value for methyl 

chloroform 

Koc, organic-carbon 

partition coefficient.

Degree to which a 

substance 

tends to stick to 

soil or move in 

soil. Lower values (< 300)* indicate great soil 

mobility; values 

of 300 to 500 

indicate moderate mobility in 

soil.

330 (Source: ICF, 

2004a).

32 to 49 (Source: 

ATSDR, 1996).

5.4 (Source: 

ATSDR, 1994).

106 to 460 

(Source: 

ATSDR, 1997).

152 (Source: U.S. 

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).

Biodegradation is 

most significant 

form of breakdown (Source: 

ATSDR, 1994).

Volatilization and 

biodegradation 

most significant, 

with hydrolysis 

relatively insignificant. Hydrolysis half-life of 

10.7 to 30 

months 

(Source: 

ATSDR, 1997).

Volatilization most 

significant; biodegradation and 

hydrolysis also 

occur (Source: 

ATSDR, 2004). 

Volatilization halflife from surface 

waters.

Tendency to volatilize and pass 

from water into 

the air.

3.4 hours-4.4 

days (Source: 

ICF, 2004a).

3 to 6.2 hours 

(Source: 

ATSDR, 1996).

7.8 to 18 hours 

(Source: 

ATSDR, 1994).

3.4 hours to 18 

days (Source: 

ATSDR, 1997).

Hours to weeks 

(Source: U.S. 

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: U.S. 

EPA, 1980).

7280 to 8120 mg/ 

L (Source: Fisher Scientific, 

2001).

40.7 to 66.8 mg/L 

(Source: NPS, 

1997).

52.8 to 105 mg/L 

(Source: U.S. 

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).

¥0.24 (Source: 

LaGrega et al., 

2001, p. 1117).

2.38 (Source: 

LaGrega et al., 

2001, p. 1127).

2.50 (Source: 

LaGrega et al., 

2001, p. 1127). 

Bioconcentration 

factor.

High factors 

(>1000)* indicate strong 

tendency for 

fish to absorb 

the chemical 

from water into 

body tissues.

23 (Source: 

HSDB, 2004).

5 to 23 (Source: 

ATSDR, 1996).

<1 (Source: 

ATSDR, 1994).

10 to 100 

(Source: 

ATSDR, 1997).

<9 (Source: U.S. 

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. We 

conclude that nPB does not pose a 

significantly greater risk to the 

environment than other available 

alternatives, and that the use of nPB 

within the U.S. should not be prohibited 

under the SNAP program on the basis of 

its environmental impacts. 

D. Flammability and Fire Safety 

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, 2003b, and 2003c; 


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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 nonflammable 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. Health Impacts and Exposure 

In evaluating potential human health 

impacts of nPB used as a substitute for 

ozone-depleting substances, EPA 

considered impacts on both exposed 

workers and on the general population. 

Using the same approach finalized in 

the original SNAP rulemaking, EPA 

evaluated the available toxicity data 

using EPA guidelines to develop healthbased criteria to characterize human 

health risks (US EPA, 1994b. Inhalation 

Reference Concentration Guidelines; 

U.S. EPA, 1991. Guidelines for 

Developmental Toxicity Risk 

Assessment; U.S. EPA, 1995a. 

Benchmark Dose guidelines; U.S. EPA, 

1996. Guidelines for Reproductive 

Toxicity Risk Assessment). 

To assess human health risks, EPA 

followed the four basic steps of risk 

assessment outlined by the National 

Academy of Sciences: hazard 

identification, dose-response 

relationship, exposure assessment, and 

risk characterization (NAS, 1983). First, 

EPA examined available studies on 

nPB’s effects. Second, EPA considered 

the acceptable exposure levels for 

evaluating worker exposure and a 

community exposure guideline (CEG) 

for evaluating exposure to the general 

population based upon inhalation 

exposure. Third, EPA compared the 

acceptable exposure levels and CEG to 

available exposure data and projections 

of exposure levels to assess exposure, 

including new exposure data available 

since publication of the June 2003 

NPRM. Finally, EPA decided whether 

there was sufficient evidence indicating 

that nPB could be used as safely as other 

alternatives available in a particular end 

use. 

Authority To Set an Acceptable 

Exposure Limit 

Two commenters on the June 2003 

NPRM said that EPA has no jurisdiction 

to develop any acceptable exposure 

limit (AEL) designed to be applicable to 

a workplace environment and that only 

the Occupational Safety and Health 

Administration (OSHA) has that 

authority (Stelljes, 2003; Morford, 

2003d). In contrast, another commenter 

said that EPA has the authority to set an 

AEL for nPB under section 612 of the 

Clean Air Act, has done so in the past 

for other chemicals (e.g., HFC–4310mee, 

HCFC–225ca/cb), and should require 

the AEL as a use condition (Risotto, 

2003). 

EPA believes it has the authority to 

calculate exposure limits for the 

workplace under section 612. Section 

612(c) specifically states that 

The Administrator shall issue regulations: 

providing that it shall be unlawful to replace 

any class I or class II substance with any 

substitute substance which the Administrator 

determines may present adverse effects to 

human health or the environment, where the 

Administrator has identified an alternative to 

such replacement that—

(1) reduces the overall risk to human 

health and the environment; and 

(2) is currently or potentially available. 

Thus, we 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, as required by the 

Clean Air Act. In order to compare risks 

to human health, EPA performs 

quantitative risk assessments on 

different chemicals comparing exposure 

data and exposure limits, following the 

process described above by the National 

Academies of Science (NAS, 1983) and 

as described in the preamble to the 

original final SNAP rule (March 18, 

1994; 59 FR 13066). Because most 

humans who are exposed to nPB are 

exposed in the workplace, the 

appropriate exposure data and exposure 

limits to protect human health must 

include workplace exposure data and 

acceptable exposure limits for the 

workplace. Because there is wide 

disparity in acceptable exposure limits 

for nPB developed by industry, ranging 

from 5 ppm to 100 ppm (Albemarle, 

2003; Chemtura, 2006; Docket A–2001–

07, item II–D–19; Enviro Tech 

International, 2006; Farr, 2003; Great 

Lakes Chemical Company, 2001), and 

because there is not a Permissible 

Exposure Limit for nPB set by the 

Occupational Safety and Health 

Administration, EPA believes it is 

appropriate to independently evaluate 

the human health risks associated with 

use of nPB in the workplace. Similarly, 

EPA has developed a community 

exposure guideline to assess the human 

health effects of nPB exposure to the 

general public. 

Skin Notation 

Several commenters on the June 2003 

proposal stated that a skin notation for 

nPB is appropriate, while another 

commenter agreed with EPA’s proposal 

that no skin notation was necessary 

(Smith, 2003; HESIS, 2003; Werner, 

2003, Weiss Cohen, 2003). Rat studies 

indicate that dermal exposure to nPB 

results in neither appreciable absorption 

through the skin (RTI, 2005) nor 

systemic toxicity (Elf Atochem, 1995). 

Unlike methyl chloride and dichlorvos, 

which are absorbed through the skin 

and could contribute to systemic 

toxicity (ACGIH, 1991), EPA is not 

proposing to include a skin notation for 

nPB in the information provided to 

users associated with this rulemaking 

because of the relatively low level of 

absorption. The American Conference of 

Governmental Industrial Hygienists 

(ACGIH) provides no skin notation in its 

documentation for threshold limit 

values (TLVs) 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. 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 

vendors to include such precautions in 

their Material Safety Data Sheets 

(MSDSs). EPA requests comment on 

whether it would be useful, in lieu of a 

skin notation to add the following 

statement in the ‘‘further information’’

column of each end use where we find 

nPB acceptable with restrictions: ‘‘EPA 

recommends the use of personal 

protective equipment, including 

chemical goggles, flexible laminate 

protective gloves and chemical-resistant 

clothing, when using nPB.’’

EPA also considered the potential 

health effects of contamination of nPB 

formulations with isopropyl bromide 


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7 iPB is also referred to as 2-bromopropane, 2- 

propyl bromide, or 2–BP. Its CAS registry number 

is 75–26–3. 

8By EPA guidelines, we would apply an 

uncertainty factor of ¥10, or approximately 3, for 

differences between species for all health effects. 

We would also apply an uncertainty factor of √10 

(3) for variability within the working population for 

reproductive and developmental effects, because, 

among other reasons, these conditions would not 

necessarily screen out an individual from being able 

to work, unlike for liver or nervous system effects. 

Therefore, for reproductive and developmental 

effects, we use a composite uncertainty factor of 10. 

See further discussion of uncertainty factors in 

section V.C. below. 

9Based on WIL, 2001, as analyzed in ICF, 2002. 

The equivalent values based upon Stelljes and 

Wood’s (2004) analysis of WIL, 2001 would be 

slightly lower, from 16 to 28 ppm. 

(iPB).7 In the June 2003 proposed rule, 

we proposed as a use condition that nPB 

formulations contain no more than 

0.05% iPB by weight. One commenter 

opposed the proposed use condition, 

stating that it places an undue legal 

burden on end users, rather than the 

manufacturers of raw materials, that it 

would not benefit worker safety, and 

that the nPB industry has worked to 

reduce iPB content below 0.05% 

(Morford, 2003e). We agree that industry 

has met this contamination limit for 

several years without regulation. 

Furthermore, EPA agrees that if users 

are exposed to nPB concentrations no 

higher than the highest potentially 

acceptable concentration (30 ppm), a 

worker’s exposure to iPB will be 

sufficiently low to avoid adverse effects. 

Therefore, this proposed rule does not 

include a use condition limiting iPB 

content in nPB formulations. 

1. Workplace Risks 

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, 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 at 18 ppm) and the 

second most sensitive endpoint (sperm 

motility in the F0 parental generation at 

30 ppm). 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). Because the animals were 

exposed to nPB for some time periods 

that would not occur during actual 

occupational exposure, 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.’’

Since the 2003 proposal, 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 

June 2003 NPRM, including new risk 

assessments on nPB, and a new 

threshold limit value (TLV) issued by 

ACGIH. 

OSHA has not developed a 

permissible exposure limit (PEL) for 

nPB that EPA could use to evaluate 

toxicity risks from workplace exposure. 

The ACGIH, an independent 

organization with expertise in industrial 

hygiene and toxicology, has developed 

a final workplace exposure limit of 10 

ppm (ACGIH, 2005); however, as 

discussed below, EPA has concerns 

about the documentation and basis of 

ACGIH’s derivation. 

The Agency reconsidered which 

exposure levels are likely to protect 

against various health effects, based on 

review of all available information. We 

summarize benchmark dose data for a 

number of endpoints found in these 

analyses in Table 6 below. We examined 

these data to assess the acceptability of 

nPB use in the aerosol solvent, adhesive 

and coatings end uses reviewed in this 

proposed 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.8 The data indicate that levels 

sufficient to protect against male 

reproductive effects (e.g., reduced sperm 

motility) would be in a range from 18 

to 30 ppm,9 in the range of 17 to 22 ppm 

to protect against female reproductive 

effects (e.g., number and length of 

estrous cycles), and at approximately 20 

ppm for effects related to reproductive 

success (live litter size). 

TABLE 6.—SUMMARY OF ENDPOINTS USING BENCHMARK RESPONSE MODELING

Endpoint a Study 

Benchmark 

dose 

lowerbound 

(BMDL) b

(ppm) 

Human 

equivalent 

concentration 

(HEC) c

(ppm) 

Liver Effects d

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 .........................

WIL, 2001 as analyzed in Stelljes & Wood, 2004 .....

169 

156 

177 

164 

Sperm motility (F0 parent generation) ......................... WIL, 2001 as analyzed in ICF, 2002 .........................

WIL, 2001 as analyzed in Stelljes & Wood, 2004 .....

282 

263 

296 

276 

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


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TABLE 6.—SUMMARY OF ENDPOINTS USING BENCHMARK RESPONSE MODELING—Continued 

Endpoint a Study 

Benchmark 

dose 

lowerbound 

(BMDL) b

(ppm) 

Human 

equivalent 

concentration 

(HEC) c

(ppm) 

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, 2006 .........................

WIL, 2001 as analyzed in ICF, 2006 .........................

162 

208 

170 

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

cWhen 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. dAfter 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. eOmits data from those animals that have stopped estrous cycling altogether (TERA, 2004). 

2. General Population Risks 

EPA used a community exposure 

guideline of 1 ppm to assess potential 

risks to the general population living 

near a facility using nPB (see section 

V.E below). Of the end uses covered in 

this rule, use of nPB-based adhesives 

would result in the highest exposure 

levels, and so, we first examined general 

population exposure from adhesives. 

ICF Consulting modeled inhalation 

exposure to nPB to people living near a 

plant using nPB-based adhesives in 

several scenarios using the Agency’s 

SCREEN3 model (US EPA, 1995b). 

Based on this modeling, EPA found that 

the exposure to individuals in the 

general population was below the 

community exposure guideline. The 

analysis indicates that nPB is no greater 

a hazard to the general population than 

other acceptable solvents under the 

SNAP program. For further discussion, 

see the risk screen for nPB (ICF, 2006a). 

Representatives from a state 

environmental agency and from a 

potential user of nPB have asked EPA 

whether we had developed a reference 

concentration (RfC). We clarify that the 

community exposure guideline is a 

value developed by the SNAP program 

for our risk assessment of nPB following 

EPA’s RfC Guidelines. However, it is not 

a formal RfC developed by EPA’s 

National Center for Environmental 

Assessment and is not in IRIS. At this 

time, EPA does not have plans to issue 

an official RfC for nPB. 

V. How did EPA assess impacts on 

human health? 

A. Newly Available Exposure Data 

Since publication of the June 2003 

NPRM, EPA has received additional 

information on exposure levels in each 

end use discussed in this proposal. 

In the adhesives end use, we 

considered new exposure modeling 

based on information from site visits to 

facilities using spray adhesives (ICF, 

2006a). These data predicted that: 

• At average rates of ventilation and 

adhesive application, average workplace 

exposures would be approximately 60 

ppm. 

• Average adhesive application rates 

and poor ventilation rates resulted in 

average exposures of approximately 250 

ppm. 

• High (90th percentile) adhesive 

application rates and average ventilation 

rates resulted in average exposures of 

approximately 600 ppm. 

• In the worst case scenario with high 

adhesive application rates and poor 

ventilation, average workplace 

exposures would be as high as 2530 

ppm. 

We compared the modeled data in the 

four exposure scenarios to measured 

exposure data in three health hazard 

evaluations by the National Institute for 

Occupational Safety and Health 

(NIOSH) (NIOSH 2002a, 2002b, 2003a). 


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10Unlike samples measured directly in the 

breathing zone, area samples measured in the study 

are not considered representative of actual exposure 

and are not discussed here. Short-term 

measurements taken over 15 minutes from personal 

samplers, although in some cases extremely high, 

are not discussed in detail here because available 

toxicity information does not indicate need for a 

short-term exposure limit for nPB in addition to the 

8-hr TWA limit (ACGIH, 2005; ERG, 2004). 

Additional information on these other samples is in 

the occupational exposure assessment for aerosols 

in the risk screen for nPB (ICF, 2006a). 

11These measurements can be converted to 

estimates of nPB exposure by multiplying the 

measured concentration of the alternate chemical 

by the molecular weight of the same alternate 

chemical and dividing this by the molecular weight 

of nPB, 123. After performing this calculation, the 

equivalent exposure levels for nPB vary from 29.5 

ppm to 394.4 ppm. 

12This corresponds roughly to a regional or room 

fan at low levels or natural air currents in an open 

area. Confined areas would have even lower air 

exchange rates with higher exposure levels. 

13We consider use of 1000 g/day to be the high 

end of typical use, based on the setup of one of the 

exposure studies (Confidential Submission, 1998). 

The typical aerosol solvent user in the electronics 

industry uses a can per day (Williams, 2005). This 

is comparable to or slightly less than the spray rate 

assumed in the modeling. 

Our understanding is that North 

Carolina OSHA received complaints 

from workers and requested that NIOSH 

evaluate health hazards at these three 

facilities. NIOSH found average 

exposure levels of 68 ppm, 116 ppm, 

127 ppm, and 195 ppm for sprayers 

actively using the adhesive prior to 

installation of state-of-the-art ventilation 

systems (NIOSH 2002a, 2002b, 2003a). 

The plant with an average exposure 

level of 68 ppm for sprayers (9 samples) 

had an average exposure level 

comparable to the average concentration 

of 60 ppm in the modeling scenario 

with average adhesive rates and average 

ventilation levels. The other plants with 

average exposure levels of 116 to 127 

ppm (20 samples), and of 195 ppm (36 

samples) for sprayers had exposure 

levels between the average modeled 

exposure for a facility with average 

adhesive application rates and average 

ventilation (60 ppm) and the average 

modeled exposure for a facility with 

average adhesive application rates and 

poor ventilation (250 ppm). Based on 

this comparison, EPA believes the 

modeled exposure levels are a 

reasonable predictor of actual exposure 

based on current industry practice in 

the adhesive end use. 

In the aerosol solvent end use, we 

received a study on workplace exposure 

levels of nPB-based aerosols from a 

commenter (Linnell, 2003). This study 

was performed to simulate typical 

exposure levels in a number of 

situations where nPB might be used in 

the workplace while using different 

types of ventilation equipment, rather 

than using data from current industry 

users of nPB-based aerosols in their 

actual manufacturing or maintenance 

processes. As discussed below in 

section VI.A., we are concerned that the 

exposure data and ventilation levels in 

this study may not be representative of 

use of nPB-based aerosols in industry. 

Personal breathing zone samples taken 

from the collars of workers showed 8- 

hour time-weighted average (TWA) 

exposures of 5.5, 13, and 32 ppm for 

workers using 310 g of nPB from a spray 

can 10 (Linnell, 2003). The two higher 

exposure levels occurred in the absence 

of any local or regional ventilation; the 

use of both local and regional 

ventilation equipment with ventilation 

levels around 1900 ft3/min was 

associated with the lowest exposure 

level. Short-term exposures of 370, 

1,100 and 2,100 ppm taken from a room 

with regional ventilation at 640 cubic 

feet per minute (cfm), when averaged 

over an 8-hour period, resulted in 

exposures of 12, 34, and 66 ppm 

(Linnell, 2003). EPA considers the 

highest of these 8-hour values, 66 ppm, 

not to be representative of worker 

exposure from inhalation because the 

measurement was taken from the 

worker’s wrist, rather than from his 

breathing zone. Another short-term 

exposure value of 190 ppm, taken from 

a vented booth with local ventilation at 

472 cfm, in addition to the regional 

ventilation of 640 cfm, resulted in an 8- 

hour exposure of 6 ppm. Similar 

measurements were made in another 

study we considered in developing the 

June 2003 NPRM: Eight hour (8-hr) 

TWA exposures of 11.3, 15.1, 17.0, and 

30.2 ppm with regional ventilation of 

300 cubic feet per minute from a fan for 

the entire room (Confidential 

submission, 1998). 

Another commenter submitted 

information on aerosol exposures for a 

number of other available alternative 

aerosols (Werner, 2003). While these 

data do not include nPB, based on the 

properties of aerosol solvents, we 

believe it is reasonable to compare 

concentrations of these different 

chemicals to potential nPB exposures. 

The study compared concentrations of 

eight different chemicals that are 

acceptable under the SNAP program in 

aerosol formulations: HFE–7100, HFE–

7200, trans-1,2-dichloroethylene, 

HCFC–225ca and –225cb, acetone, 

pentane, and HFC–134a. In this study, 

with ventilation of only 48 cfm, 8-hr 

TWA exposure from the different 

chemicals varied from 35.5 ppm to 

194.0 ppm,11 below the recommended 

exposure levels for these particular 

chemicals (ICF, 2006a) but above the 

range of exposure levels that EPA would 

consider acceptable for nPB. 

In addition, we considered new 

information from modeling of nPB 

exposures (ICF, 2006a). The modeling 

examined exposure levels that would be 

expected at ventilation levels of 450 

cfm, 625 cfm, and 1350 ppm, 

considering the molecular weight of the 

compound and the composition of 

different aerosol blends. EPA’s SNAP 

program has previously used these same 

levels to calculate potential aerosol 

exposures, based upon exposure levels 

expected during benchtop cleaning. In a 

space with an air exchange rate of 450 

ft3/minute or less,12 EPA’s modeling 

predicts 8-hour average exposure of 

approximately 16 to 17 ppm if a user 

sprays 450 g of nPB (approximately 1 

lb),13 and corresponding higher 

exposure values at higher spray rates 

(e.g., 33 ppm if the amount of nPB 

sprayed is 900 g) (ICF, 2006a). Exposure 

values were predicted to be lower at 

higher ventilation rates. 

Since the June 2003 NPRM, EPA 

received a new submission for nPB in 

coatings (Lake City Army Ammunition 

Plant, 2003). The Lake City Army 

Ammunition Plant provided data on 

workplace exposure to nPB (Lake City 

Army Ammunition Plant, 2004). The 

mean exposure at this facility was 3.7 

ppm. Out of 31 samples taken, 25 

(approximately 80%) were below 5 

ppm. Only one of 31 samples had an 

exposure level above 10 ppm, and that 

exposure value was approximately 21 

ppm. 

B. Newly Available Data on Health 

Effects 

Since publication of the June 2003 

NPRM, EPA has examined additional 

occupational (Table 7) and animal 

(Table 8) studies that have become 

available: 


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TABLE 7.—RECENT STUDIES ON nPB OCCUPATIONAL EXPOSURE

Case Study Sample size/population Exposure data Observations Remarks 

Beck and Caravati, 

2003.

6 foam cushion factory workers (gluers).

Exposure during 30–

40 hr/wk for a 3- 

month period. Exposure measured in 

one day was a 

mean of 130 ppm 

(range, 91–176 

ppm).

Lower leg weakness accompanied by pain 

and difficulty with standing and walking, 

numbness of legs and feet, hyperreflexia 

and hypertonicity of lower extremities, dizziness and shortness of breath, and peripheral neurotoxicity. Measured serum 

bromide levels were elevated, range 44–

170 mg/dL.

Small sample size studied. Possible interference or synergistic effects from other 

adhesive ingredients (1,2-epoxybutane 

and styrene-butadiene). 

Majersik et al., 2004; 

Majersik et al., 

2005 *.

6 foam cushion factory workers (gluers).

5–8 hr/day for at least 

2 years with mean 

air concentration of 

130 ppm on last 

day of study. Measurements taken 

over 9 hours (equivalent to 92–127 

ppm with mean of 

108 ppm for an 8- 

hour TWA).

Subacute onset of lower extremity pain, difficulty walking, and high serum bromide 

levels in blood. Neurotoxic symptoms persisted for at least 2 years after exposure 

ended.

Follow-up to Beck and Caravati (2003). 

Chronic nPB exposure associated with incapacitating neurotoxic syndrome. Initial 

report from Utah OSHA indicated erroneously that workers were not spraying 

while measurements were taken. In fact, 

adhesives were being sprayed and fans 

were being used only for portions of the 

day that measurements were taken, making measurements likely to be representative of conditions during the past several 

months at the plant. 

Ichihara et al., 2004a 37 chemical plant 

workers (24 males 

and 13 females).

12 hour shifts over 2- 

day period, mean 

concentration of 82 

ppm (range, 0–170 

ppm).

Mucosal irritation (nose, throat), headache, 

dizziness, constipation, intoxication, and 

feeling light-headed or heavy-headed. 

Four female workers complained of disruption or cessation of menstruation. No 

severe chronic symptoms of neurological 

damage at less than 170 ppm. Several 

workers had hemoglobin and hematocrit 

values outside of the normal range and 

were diagnosed with mild anemia; most of 

these cases also showed signs of iron deficiency.

Inadequate exposure characterization and 

exposure to other potential toxicants, 

small sample size, and no appropriate 

control group. Healthy worker effect possible, where more sensitive workers left 

the factory between 1996 and 1999. 

Ichihara et al., 2004b 27 female chemical 

plant workers (23 

age matched with 

23 females from a 

beer factory control 

group).

1-day exposure period, range of exposure, 0.34–49 ppm.

Responses indicated anxiety, fatigue, confusion, tension, and depression. Changes in 

menstrual status but not statistically significant. Effects on peripheral and central 

nervous system—diminished vibration 

sensation of the foot; significantly longer 

distal latency in the tibial nerve; decreased values in sensory nerve conduction velocity in the sural nerve; and lower 

scores on memory and perceptual tests. 

No comparable effects seen in control 

group.

No long-term exposure measurements, 

small sample size; lack of controls for 

age, height, and body-weight. Low B vitamin levels in normal range in some workers but researchers concluded this did not 

cause observed neurological effects. Additionally, the study did not indicate any significant differences in the prevalence of 

menstrual cycle abnormalities. 

Nemhauser, 2005 * ... Foam cushion factory 

workers (gluers) in 

North Carolina.

In 1999 study, 16 

workers exposed to 

mean air concentration of 116 ppm, 

and 12 sprayers exposed to mean concentration of 108 

ppm with range of 

58 to 254 ppm. In 

2001 study, 13 

workers exposed to 

nPB mean air concentration of 46 

ppm and 12 sprayers were exposed 

to mean concentration of 101 ppm, 

with range of 38 to 

281 ppm.

Higher exposure to nPB and dose-dependent relationship among those who reported anxiety, headache, and ataxia. No 

reproductive abnormalities reported in 

medical survey for men or women. Semen 

analysis found no differences between exposed and unexposed workers.

Small sample sizes studied with moderate 

worker participation. Healthy worker effect 

likely occurred: Those that had most significant health effects had already removed themselves from workplace by the 

time of the study. No arsenic found at the 

plant. Neurotoxic effects caused by nPB. 

See related Health Hazard Evaluation 

(HHE): NIOSH, 2003a. 

NIOSH, 2003a ........... 16 workers in 1999 

evaluation; 13 workers in 2001 followup evaluation.

1999 Initial Site Visit: 

Geometric mean 

nPB concentration 

(from personal samples), 81.2 (range, 

18–254 ppm); 2001 

follow-up: Geometric mean, 81.2 

ppm (range, 7–281 

ppm).

Most workers exposed to nPB levels > 25 

ppm. Exposure concentrations lower in 

2001 than 1999, but difference not statistically significant. Headache, anxiety, feeling drunk associated with nPB exposure. 

Hematological endpoints unaffected in exposed group. No correlation of nPB exposure with sperm or semen indices or with 

neurological abnormalities.

Arsenic was not attributed to occupational 

exposure. The National Institute for Occupational Safety and Health (NIOSH) stated that neurological symptoms may have 

been related to excess exposure to nPB, 

but that no other effects could conclusively be related to nPB exposure. 


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TABLE 7.—RECENT STUDIES ON nPB OCCUPATIONAL EXPOSURE—Continued 

Case Study Sample size/population Exposure data Observations Remarks 

Raymond and Ford, 

2005 *.

4 foam cushion factory workers (gluers) in North Carolina.

Exposure study conducted 9 months 

after index patient 

became ill indicated 

workers exposed to 

mean nPB air concentration of 116 

ppm. 4 workers exposed for 2–3 

weeks before initial 

symptoms detected.

Dizziness, numbness, ocular symptoms, 

lower extremity weakness and unsteady 

gait, weakness, hypesthesia, and ataxic 

gait in all four workers. Symptoms decreased over time but after six years, at 

least one worker re-exposed twice at 

other furniture plants; one or more still 

suffer from ataxia.

Small sample size, possible confounding effect from arsenic. 

Toraason et al., 2006 41 and 22 foam cushion factory workers 

(gluers) at 2 facilities.

1–3 days up to 8 hrs 

per day, with concentrations of 0.2–

271 ppm at facility 

A, 4–27 ppm at facility B.

No statistically significant differences in DNA 

damage with worker’s nPB exposure. In 

vitro results showed nPB increased DNA 

damage.

Authors find limited evidence that nPB 

poses a ‘‘small risk’’ for DNA damage. 

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

TABLE 8.—RECENT ANIMAL STUDIES OF nPB EFFECTS

Citation Population/sample size Exposure Observations Comments 

Fueta et 

al., 2002.

24 male Wistar 

rats (12 control, 

12 exposed).

6 hr/day, 5 day/ 

wk for 8 weeks 

at 700 ppm.

No apparent morphological defects in the brain ........... Only one exposure concentration was used (which is 

higher than the level already associated with other 

toxic effects in rodents [400 ppm]) and a shorter exposure duration (8 weeks) was used than the other 

subchronic studies that have shown effects (13 

weeks). 

Fueta et 

al., 2004.

58 male Wistar 

rats (29 experimental and 29 

in control 

group).

6 hr/day, 5 day/ 

wk for 4 to 8 

weeks, 700 

ppm.

No apparent morphological defects in the brain. 

Chronic inhalation changes brain enzyme levels and 

electrical activity that is reversible after exposure.

Unclear how nPB and/or its metabolites directly act on 

receptors or channels in the brain. 

Furuhashi 

et al., 

2006.

80 Wistar rats 

(pups and their 

dams).

(1) 8 hr/day (4 hr, 

followed by 2.5- 

hr rest period, 

followed by 4 hr 

exposure), 7 

day/wk during 

gestation and 

nursing at 0, 

100, 400, 800 

ppm in first experiment.

(2) Dams exposed (800 

ppm) during 

gestation 

(Group A), offspring not exposed during 

nursing. Offspring of Group 

(B) of unexposed dams 

were nursed by 

exposed dams. 

Offspring in 

control groups 

C and D not exposed.

(1) At 800 ppm: most rat offspring died within 2 days 

of birth or in utero;. body weights of dams significantly lower, organ weights of offspring significantly 

lower after weaning at 800 ppm in males, and 800 

and 400 ppm in females. Most sperm and estrous 

indicators did not differ among the groups, although 

the rate of sperm arrival to the cauda epididymis 

was significantly lower in the 400 ppm group. Inconsistent or no changes in biochemical indicators.

(2) Second experiment No difference in body weights 

and pregnancy endpoints between exposed (800 

ppm) and unexposed dams. Live offspring at birth, 

survival rates, body weights, significantly decreased, 

number of dead offspring, significantly increased in 

800-ppm groups.

Authors concluded that exposure to nPB during pregnancy and lactation adversely affects growth and 

survival of offspring. Low numbers of offspring in 

400- and 800-ppm exposure groups prevent statistical testing 

EPA comments: Study design inconsistent with guidelines for developmental studies, so comparisons to 

previous studies are difficult. The mechanism for the 

adverse effects observed is not known (e.g., indirect 

exposure through milk, changes in nursing behavior, 

changes in milk production, exposure in utero, 

changes in the intrauterine environment) 

Honma et 

al., 2003.

Fisher 344 male 

rats.

8 hr/day, 7day/wk 

for three weeks 

exposed to 0, 

10, 50, 200 or 

1000 ppm (5 

rats/dosage 

and 5 different 

tests).

3 week exposure to greater than 50 ppm temporarily 

increased locomotor activity and ambulatory and 

rearing behaviors in male rats.

Neurological effects shown to be transient and reversible at ≥ 200 ppm (Ichihara et al., 2000) or absent 

after 28 days of exposure at concentrations ≥ 400 

ppm (ClinTrials, 1997a) or after 90 days of exposure at concentrations up to 600 ppm (ClinTrials, 

1997b) in other studies. Human studies are limited 

by co-exposures and poor estimates of exposure 

concentrations. Thus, EPA is not using this endpoint 

as the basis of an AEL. 


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TABLE 8.—RECENT ANIMAL STUDIES OF nPB EFFECTS—Continued 

Citation Population/sample size Exposure Observations Comments 

Ishidao et 

al., 2002.

30 male Wistar 

rats.

6 hr/day, 5 day/ 

wk with test 

groups (10/ 

dose) exposed 

to 700 ppm for 

4 and 12 weeks 

and 1500 ppm 

for 3 and 4 

weeks.

nPB is metabolized rapidly in the rat following exposures to nPB at concentrations ≥ 700 ppm for at 

least 3 weeks.

Exposure levels are higher than in some other studies 

and are much higher than concentrations seen in 

the workplace. nPB metabolism appears to be different following multiple exposures as compared to 

acute exposures (see RTI, 2005; ICF, 2006b). 

NTP, 2003 Female and male 

B6C3F1 mice 

and Fischer 

344 rats.

0, 62.5, 125, 250, 

500 (rats and 

mice), 1000 

(rats) ppm for 

90 days.

Early mortality in mice at 500 ppm accompanied by 

liver and lung cell degeneration and cytoplasmic 

vacuolization. Cytoplasmic vacuolization also in rat 

liver cells ≥ 250 ppm (males) and ≥ 500 ppm (females), with increased severity at higher doses. No 

adverse central nervous system (CNS) effects or 

histopathology reported.

Unpublished study. Conclusions drawn from a review 

of raw data from the National Toxicology Program 

(NTP) Web site. In general, the severity of effects 

(in non-reproductive organs) is slightly higher at 

lower concentrations in male rats than in females. 

RTI, 2005/ 

Garner 

et al., 

2006.

Female and male 

B6C3F1mice 

and Fisher 

344N rats, four 

to six animals 

in each test trial.

Exposure via several injection 

routes 

(intraperitoneal, 

intravenous, 

cannuliz-ation), 

inhalation, and 

dermal. Injection conducted 

via bolus dosing at 5, 20, or 

100 mg/kg body 

weight. Inhalation concentrations of 70, 

240, 800, and 

2700 ppm administered in a 

single acute exposure. A dose 

of 96 mg/kg 

was applied to 

a shaved area 

on the backs of 

six male rats 

with a non-occlusive charcoal 

filter covering 

(that is, one 

that does not 

prevent evaporation).

nPB cleared by mice after 48 hours as follows: 45% 

as volatiles in the breath, 28% as CO2 in the breath, 

26% in urine, <3% in feces, and 2% retained in the 

body. Distribution was similar in male rats, although 

amounts in urine and volatiles in breath were higher 

in mice. At higher doses, the amount of nPB excreted in urine and as CO2 decreased, with a much 

greater change in rats compared to mice.

• After pretreatment with a cytochrome P450 inhibitor, 

a decrease in nPB cleared as CO2 (80%) and urine 

(40%); pretreatment with a glutathione inhibitor reduced nPB cleared as CO2 by 10% and urine by 

4%.

• The Vmax, a measure of the maximum initial rate of 

an enzyme-catalysed reaction, is 0.227 for male 

rats, 0.143 for female rats, 0.329 for male mice and 

0.234 for female mice. Half-lives were comparable 

between males and females at ≤ 800 ppm.

• For rats exposed to nPB through skin, 37% of the 

dose was excreted in volatiles, 1.2 % in urine, 1.7% 

as CO2, and 35.7% was on the applicators or in the 

skin washes. Only 0.32% remained in tissues. Airborne concentrations of nPB in the chamber were 4 

to 10 ppm after dosing.

The study authors concluded that: 

• nPB administered via intraperitoneal injection or inhalation is eliminated mostly through the breath, 

with urine as a secondary path. 

• Metabolism of nPB appears to be primarily through 

cytochrome P450 enzymes (CYP2E1), particularly 

in mice; glutathione conjugation still plays an important role in rats. 

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

male rats. 

• nPB decreases glutathione levels in the liver after a 

one-time exposure to nPB at concentrations as low 

as 70 ppm. 

• nPB is not appreciably absorbed (∼3–27%) in rats 

following dermal application. 

EPA agrees with these points, except we found that 

gender differences were only apparent in rats at 

very high concentrations (2700 ppm and greater). 

We also note that: 

• Inhalation tests were only one-time exposures at 

very high concentrations (240 to 2700 ppm), and 

thus, are not comparable to long-term dosing at the 

lower levels expected in the workplace. 

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

Sohn et 

al., 2002.

40 male and 40 

female 

SpragueDawley rats.

6 hr/day, 5 day/ 

wk for 13 

weeks, test 

groups (10/sex/ 

dose) were exposed to 0, 

200, 500 or 

1250 ppm.

No effects on mortality, activity, weight gain, food consumption, urinalysis, or histological effects in the 

brains and spinal cords.

The differences between the various studies may be 

due to variability in exposure methodology and 

achieved concentrations of nPB. 

Stump, 

2005*.

125 female/125 

male rats in first 

generation and 

100 female/100 

male rats in offspring generation.

Both test groups 

of 25 male rats/ 

25 female rats 

exposed to 0, 

100, 200, 250, 

500 and 750 

ppm nPB for 10 

weeks.

Decreased litter size at 250 and 500 ppm in both generations. Decreased fertility at 100 and 250 ppm in 

offspring generation.

Complete infertility at 750 ppm. 

Reproductive effects seen in both rat sexes which is a 

strong signal of reproductive toxicity potential in humans. The author considers 100 ppm to be a lowest 

observed adverse effect level (LOAEL). This is a 

presentation of data from WIL, 2001. 

Wang et 

al., 2003.

36 male Wistar 

rats.

8 hr/day, 5 day/ 

wk for 12 

weeks, test 

groups ( 9 rats) 

were exposed 

to 0, 200, 400 

or 800 ppm.

Decrease in creatine kinase in the spinal cord (17% at 

≥ 200 ppm) and brain (15–28% at ≥ 400 ppm) at 

200, 400, and 800 ppm. No physical or behavioral 

changes observed.

Small study size. No behavioral changes or physical 

symptoms were observed in the animals, so the toxicological relevance of the decrease in creatine kinase is questionable. 

Yamada et 

al., 2003.

40 female Wistar 

rats.

8 hr/day, 7 day/ 

wk with test 

groups (9/dose) 

exposed to 0, 

200, 400, or 

800 ppm for 12 

weeks.

All rats at 800 ppm became seriously ill after 7 weeks 

of exposure. Significant decrease in antral follicles 

at ≥ 200 ppm, and a decrease in the number of female rats exhibiting regular estrous cycles in 400- 

ppm females during 7–9 weeks of exposure and at 

2–3 weeks at the 800-ppm dose.

Data suggest that nPB is affecting the maturation of 

ovarian follicles. A no observed adverse effect level 

(NOAEL) of 200 ppm is identified with a LOAEL of 

400 ppm for the changes in estrus cycles. 

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


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Federal Register / Vol. 72, No. 103 / Wednesday, May 30, 2007 / Proposed Rules 30183 

• In general, the recent animal studies 

collectively show a range of effects 

associated with nPB exposure that are 

qualitatively consistent with previously 

published findings. (Exceptions to this 

are the negative results regarding central 

nervous system toxicity in the NTP 

(2003) study and the Sohn (2002) study 

on rats.) Some general conclusions we 

draw from the new studies include: 

• 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., 

2002a; 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). 

• 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). 

A number of commenters on the June 

2003 NPRM suggested that EPA should 

consider neurotoxicity as the endpoint 

in deriving an AEL for nPB (Linnell, 

2003; Werner, 2003; Rusch and 

Bernhardt, 2003, Rusch, 2003). In 

particular, they requested that EPA 

consider the study conducted by Wang 

(2003) and epidemiological data on 

neurotoxic effects of nPB. As discussed 

above, the data on neurotoxic effects of 

nPB on workers are limited and are not 

sufficient to determine acceptable levels 

of exposure. 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 determine acceptable 

exposure levels based on this endpoint. 

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. In response to the comment, 

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) 

to assess potential reproductive toxicity 

in females (ICF, 2006a, Att. A). A peer 

review of these effects is in the public 

docket (ICF, 2004b). 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). 

Reproductive effects are seen in 

males, females, and offspring, and in 

different generations of the twogeneration study (WIL, 2000). They also 

are consistent with results seen in onegeneration reproductive studies, such as 

Ichihara et al. (2000b) and Yamada 

(2003). See Table 6 above in section 

IV.E.1. for a more complete list of the 

different health effects. EPA believes 

that the preponderance of the data 

indicate that exposure levels 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., 

number and length of estrous cycles), 

and at approximately 20 ppm for effects 

related to reproductive success (live 

litter size). We have not determined 

what specific level within those ranges 

(an overall range of 17 to 30 ppm) is 

most appropriate for evaluating whether 

a substitute may be used safely and 

consider these exposure levels to be 

potentially acceptable. Therefore, we 

assessed the acceptability of nPB by 

considering whether it could be used 

safely in the three end-uses. For enduses with likelihood of exposures above 

the range we are considering, while 

following typical industry practices, we 

are proposing an unacceptability 

determination. For end-uses that as their 

normal practice meet exposure levels 

below the range we are considering, we 

are proposing an acceptability 

determination. It is not necessary for 

100% of exposure data for an end use 

to be above or below the range of 17 to 

30 ppm in order to make a 

determination on the acceptability of an 

end use because there may be 

occasional cases that are not following 

common industry practices. Unusual 

events would not indicate the industry’s 

likelihood of keeping exposures at safe 

levels, and thus, should not be the 

determining factor in our decision. 

Rather, we consider the overall 

likelihood that typical industry use 

would consistently result in acceptably 

low or unacceptably high exposures. 

In the June 2003 NPRM, EPA used a 

BMDL of 169 ppm as a point of 

departure for developing an AEL. Some 

commenters stated that data from the F1 

generation is inappropriate for 

calculating occupational exposure, 

citing statements from toxicologists, 

such as, ‘‘occupational exposure 

involves adults only.’’ 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, 2003f, Ruckriegel, 

2003). Others stated that sperm motility 

effects on the F1 generation are 

appropriate to consider (Risotto, 2003; 

Farr, 2003), particularly because of the 


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14Pharmacodynamics refers to the biochemical 

and physiological effects of chemicals in the body 

and the mechanism of their actions. 

15Pharmacokinetics refers to the activity or fate 

of chemicals in the body, including the processes 

of absorption, distribution, localization in tissues, 

biotransformation, and excretion. 

16The blood/air partition coefficient is the ratio 

of a chemical’s concentration between blood and air 

when at equilibrium. 

potential for in utero effects and because 

of the consistent presence of these 

reproductive effects in both generations 

and at multiple levels. EPA 

acknowledges that using data from the 

F1 offspring generation may be 

conservative because the pups in the F1 

generation 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, we 

believe it is appropriate 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). Therefore, we 

believe that the available data indicate 

that in order to protect against adverse 

reproductive effects, an exposure level 

within the range of 17 to 30 ppm, would 

potentially be acceptable. We would 

reach the same proposed decisions of 

unacceptability based upon data from 

the F0 generation. 

C. Evaluation of Acceptable Exposure 

Levels for the Workplace 

To calculate acceptable exposure 

levels for nPB, EPA uses standard risk 

assessment methods delineated in 

Agency guidance (U.S. EPA, 1994b) in 

evaluating data, choosing a benchmark 

dose level or a NOAEL, and making the 

adjustments and uncertainty factors 

prescribed to account for differences in 

the duration of exposure and in 

sensitivity between and within species. 

Adjustment for Occupational Exposure 

Pattern 

To account for differences between 

the exposure pattern used in the WIL 

study (6 hours per day for 7 days per 

week) when compared to a typical 

workweek of 8 hours per day and 5 days 

a week, a ‘‘human equivalent 

concentration’’ (HEC) is first calculated 

by adjusting the benchmark dose level: 

(BMDL in ppm × 6 hours/8 hours) × 7 

days/5 days = HEC (ppm) 

HECs for the major health endpoints are 

shown in Table 6 above in section 

IV.E.1. 

Uncertainty Factors 

According to EPA risk assessment 

guidance for reference concentrations 

(RfC) (EPA 1994a), uncertainty factors of 

up to 10 may be applied to the HEC for 

each of the following conditions: 

(1) Data from animal studies are used 

to estimate effects on humans; 

(2) Data on healthy people or animals 

are adjusted to account for variations in 

sensitivity among members of the 

human population (inter-individual 

variability); 

(3) Data from subchronic studies are 

used to provide estimates for chronic 

exposure; 

(4) Studies that only provide a LOAEL 

rather than a NOAEL or benchmark 

dose; or 

(5) An incomplete database of toxicity 

information exists for the chemical. 

EPA believes that two uncertainty 

factors are appropriate for this database 

to account for that: (1) Physiological 

differences between humans and rats; 

and (2) variability within the working 

population. The rationale for the use of 

these two uncertainty factors is 

described below. 

EPA RfC guidelines state that an 

uncertainty factor of 10 may be used for 

potential differences between study 

animals and humans. This factor of 10 

consists in turn of two uncertainty 

factors of 3—the first to account for 

differences in pharmacodynamics 14 and 

the second to account for differences in 

pharmacokinetics 15 between the study 

of animal and humans. (The value of 

three is the square root of 10 rounded 

to one digit, with 10 representing an 

order of magnitude (EPA,1994a). In 

practice, EPA uses the square root of 10 

when there are two or four uncertainty 

factors of 3, yielding a total uncertainty 

factor of 10 or 100, and we use a value 

of 3 when multiplying by an uncertainty 

factor of 10). By EPA RfC guidelines 

(U.S. EPA, 1994b), no adjustment for 

differences in pharmacokinetics is 

necessary in this instance because the 

blood/air partition coefficient 16 for nPB 

in the human (7.1) is less than in the rat 

(11.7), indicating that the delivered dose 

of nPB into the bloodstream in rats is 

slightly higher than in humans. 

Consistent with Appendix J of EPA’s 

RfC guidelines for an inhaled compound 

that exerts its effects through the 

bloodstream, EPA applies an 

uncertainty factor of 1 for 

pharmacokinetics. 

However, EPA recognizes that the lack 

of an uncertainty adjustment for 

pharmacokinetic differences between 

animals and humans rests on a default 

approach applied to category 3 gases 

described in Appendix J of its 

guidelines for deriving an inhalation 

RfC. This default approach assumes that 

nPB’s toxicokinetics follow a model in 

which: (1) The toxicity is directly 

related to the inhaled parent compound 

in the arterial blood, and (2) the critical 

metabolic pathways scale across 

species, with respect to body weight, in 

the same way as the ventilation rate. 

Given the hypothesized metabolic 

pathways for nPB (ICF, 2002a; CERHR, 

2002a), it is plausible that toxicity in 

rats may be related to a reactive 

metabolite in the target tissue rather 

than the blood level of the parent 

compound. EPA is not aware of any 

quantitative data on nPB metabolism in 

humans, or evidence implicating the 

biologically active agent or mode of 

action. Some commenters on the June 

2003 NPRM stated that EPA should use 

an uncertainty factor of 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). 

Commenters provided no data to 

indicate that (1) the toxicity is not 

directly related to the inhaled parent 

compound in the arterial blood, or (2) 

the critical metabolic pathways do not 

scale across species, with respect to 

body weight, in the same way as the 

ventilation rate. 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). However, 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 


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Federal Register / Vol. 72, No. 103 / Wednesday, May 30, 2007 / Proposed Rules 30185 

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, 2006b). 

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 are 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. Therefore, the Agency 

is proposing to apply an uncertainty 

factor of 1 to account for interspecies 

differences in pharmacokinetics. 

EPA requests additional data and 

comment from the public on the 

pharmacokinetics, metabolism, and 

mode of action of nPB that will help 

determine whether an interspecies 

uncertainty factor greater than the 

default value of 1 is warranted to 

account for pharmacokinetics. If data 

become available indicating that nPB 

does not conform to the constraints 

assumed by the default pharmacokinetic 

model in the RfC guidelines, we would 

revise our risk assessment for nPB as 

necessary, and apply an uncertainty 

factor for pharmacokinetics consistent 

with the RfC guidelines in extrapolating 

from animal to humans. Depending on 

the resulting difference in the 

acceptable exposure levels, we would 

also revise our acceptability 

determinations accordingly. Given the 

available data on the blood/air partition 

coefficient and EPA RfC guidance in the 

absence of other information, EPA is 

applying the same rationale used for 

other compounds reviewed under EPA’s 

SNAP program with a comparable 

amount of data where an uncertainty 

factor of 1 for pharmacokinetics was 

applied. To account for uncertainty in 

pharmacodynamics of nPB, EPA is 

applying the default uncertainty factor 

of 3. This follows the procedures in 

EPA’s RfC guidelines for situations 

where there are no data to compare 

pharmacodynamics in rats versus 

humans (U.S. EPA, 1994b). Recently 

published data on humans and rodents 

do not decrease the uncertainty 

regarding the pharmacodynamics of 

nPB; therefore, modification of the 

uncertainty factor of 3 for differences 

between species is not justified. 

One commenter stated that EPA did 

not cite any data that describes the size, 

condition, or very 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 occupational exposure limit, and that 

EPA has never mentioned a concern 

with sensitive subpopulations in 

previous SNAP reviews. 

EPA disagrees with the comments. 

There are preexisting reproductive 

conditions as well as significant 

variability in fertility among otherwise 

healthy adults in the workplace. Women 

over age 35 and men over age 40 have 

fertility rates up to three times lower 

than those of people in their twenties, 

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 occupation exposure to 

chemicals such as nPB, therefore, can 

potentially harm an individual’s ability 

to reproduce further (Dunson, et al. 

2002). 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 69 FR 58907, 

October 1, 2004). 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 apply an uncertainty 

factor greater than 1 for reproductive 

effects. 

Some commenters on the June 2003 

NPRM 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, 2003f). 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). 

EPA’s RfC guidelines recommend an 

uncertainty factor of 10 to account for 

intraspecies variability within the 

general population. However, in 

deriving an acceptable exposure limit, 

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. However, 

because of variability in reproductive 

function due to factors present among 

workers, such as aging, smoking, and 

sexually transmitted disease, 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. 

Therefore, EPA is again proposing to 

assign an uncertainty factor of 3 to 

account for difference between 

individuals in the working population. 

The uncertainty factors of 3 for 

animal-human extrapolation and 3 for 

variability within the human working 

population (each representing the 

square root of ten, half an order of 

magnitude) yield a composite 

uncertainty factor of 10. This factor was 

applied to all HECs derived from 

reproductive studies summarized in 

Table 6 in section IV.E.1 above. The 

resultant values are higher than the 

value that would have been obtained 

had EPA used the TLV of 10 ppm 

developed by the ACGIH. EPA believes 

that the benchmark dose approach more 

accurately characterizes the observed 

effects and provides a more robust 

utilization of the data. 

D. Other Analyses of nPB Toxicity 

Analyses Reviewed During Preparation 

of June 2003 NPRM 

One commenter on the June 2003 

NPRM stated that documents by Drs. 

Doull, Rozman, Stelljes, Murray, 

Rodricks, and the KS Crump Group 

were not acknowledged (Morford, 2003f, 

g, and h). EPA specifically mentioned 


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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). We considered these documents 

in preparation of the June 2003 proposal 

as well as this proposal. 

In general, we disagree that the 

neurotoxicity endpoint selected by Drs. 

Rozman and Doull is the most 

appropriate endpoint for setting an AEL 

and we agree with Dr. Stelljes that 

sperm motility in the F1 offspring 

generation of the WIL, 2001 2- 

generation study is an appropriate 

endpoint. We agree with a number of 

these documents that data from the F1 

generation may be conservative because 

workplace exposure would not include 

exposure to the F1 animals during the 

four-week period from weaning to 

sexual maturity. 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 3-week 

period, and the number of live pup 

births (TERA, 2004; ICF, 2006a; SLR 

International, 2001; Stelljes and Wood, 

2004). We believe that the document 

from the K. S. Crump group, a survey of 

the ratio of points of departure to TLVs 

set by the ACGIH, is not relevant now 

that the ACGIH has issued a TLV 

specifically for nPB. ACGIH appears to 

set an AEL for nPB 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. In general, we find that these 

documents submitted by the commenter 

assigned uncertainty factors in a manner 

inconsistent with EPA 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 (e.g., 

variability within the working 

population, differences between animals 

and humans in how nPB affects the 

reproductive system). 

Since the 2003 NPRM, a number of 

reviews of nPB toxicity have been 

issued, several of which include 

recommendations for occupational 

exposure limits. CERHR, 2003a and 

2004a are similar to CERHR, 2002a, the 

expert panel report for nPB for the 

Center for the Evaluation of Risks to 

Human Reproduction (CERHR). CERHR, 

2003b and 2004b are similar to CERHR, 

2002b, the CERHR expert panel’s report 

for iPB. These documents discuss the 

usefulness of data in available studies 

for assessing nPB’s health impacts and 

establish No Observed Adverse 

Concentration levels of 100 ppm for 

both male and female reproductive 

effects in animals, but do not derive an 

AEL. Rozman and Doull, 2005 derived 

an AEL of 25 ppm for nPB based on 

neurotoxicity, using more recent 

information than Rozman and Doull, 

2002. 

The Stelljes and Wood (2004) analysis 

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 studies by 

Stelljes and Wood concluded with a 

recommended AEL of 156 ppm, based 

on male reproductive effects and 

uncertainty factors of 1 in driving the 

AEL. Stelljes (2005) reviews RTI’s 2005 

study on metabolism of nPB in mice and 

rats and other literature and speculates 

that humans should be less sensitive to 

nPB than either mice or rats based on 

differences in metabolite production. 

Stelljes (2005) recommends that no 

uncertainty factor is required to 

extrapolate from animals to humans and 

that an uncertainty factor of no more 

than 2 is appropriate to account for 

differences within the working 

population. All of these documents 

assigned uncertainty factors in a manner 

that is not sufficiently supported by the 

available data and that is inconsistent 

with EPA’s guidance. For example, 

Stelljes (2005) discusses metabolic data 

in rats and mice from RTI, 2005 and 

concludes that on this basis, the 

uncertainty factor for extrapolation from 

animals to humans should be 1. 

However, the metabolic data relate to 

pharmacokinetics—the activity of 

chemicals in the body—and do not 

address EPA’s proposed uncertainty 

factor of 3 related to pharmacodynamics 

(the biochemical and physiological 

effects of chemicals in the body and the 

mechanism of their actions). Using the 

AEL from one of these documents 

would result in a higher, less protective 

AEL than we would determine 

following the approach EPA has used 

for other chemicals under the SNAP 

program and would not consider 

multiple sources of uncertainty in 

health effects (i.e., variability within the 

working population and differences 

between animals and humans in how 

nPB affects the reproductive system). 

Thus, we are concerned that the AELs 

based on these documents would not be 

sufficiently protective and would result 

in an inappropriate acceptability 

decision. Detailed reviews of these 

documents are available in the public 

docket. 

Toxicological Excellence in Risk 

Assessment (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 analysis 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, 

2004c). 

ICF (2004b, 2006a) derived an AEL for 

nPB based upon female reproductive 

effects. ICF (2004b, 2006a) 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 (2004b, 

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 (2004b, 2006a) 

conducted BMD modeling and 

calculated 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 


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17 Vendors of nPB-based products have 

recommended a wide range of exposure limits, from 

5 ppm to 100 ppm (Albemarle, 2003; Chemtura, 

2006; Docket A–2001–07, item II–D–19; Enviro 

Tech International, 2006; Farr, 2003; Great Lakes 

Chemical Company, 2001). 

18We performed the modeling for a facility using 

nPB-based adhesives because the nPB emissions 

from this type of facility were expected to be higher 

than those from facilities using nPB for other end 

uses. Thus, if a facility using adhesives would not 

result in emissions exceeding the CEG, facilities 

using nPB in aerosols or in metals, electronics, or 

Continued 

deviation) and using a linearheterogeneous model. 

The California Environmental 

Protection Agency’s Office of 

Environmental Health Hazard 

Assessment (OEHHA) listed both nPB 

and iPB as reproductive toxins on the 

basis of developmental, male 

reproductive, and female reproductive 

toxicity under the State’s Safe Drinking 

Water and Toxic Enforcement Act of 

1986, also known as Proposition 65 

(OEHHA, 2006). Under this law, 

California is required to list chemicals 

known to be carcinogenic or to be 

reproductive toxins and to update that 

list at least annually. 

The American Conference of 

Government Industrial Hygienists 

(ACGIH) issued a recommended 

Threshold Limit ValueTM (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). 

OSHA has not developed a 

permissible exposure limit (PEL) for 

nPB that EPA could use to evaluate 

toxicity risks 17 from workplace 

exposure. In prior SNAP reviews, EPA 

has used ACGIH TLVs where available 

in assessing a chemical’s risks and 

determining its acceptability if OSHA 

has not set a PEL. ACGIH is recognized 

as an independent, scientifically 

knowledgeable organization with 

expertise in issues of toxicity and 

industrial hygiene. However, in this 

case, EPA believes that ACGIH’s TLV for 

nPB of 10 ppm has significant 

limitations as a reliable basis for an 

acceptable exposure limit, especially 

given the availability of other, more 

comprehensive analyses described in 

this proposal. First, according to the 

authors of the Huntingdon Life Sciences 

study, the decrease in fetal weight was 

an artifact of sampling procedure that 

biased the data (test animals were only 

sacrificed at the end of the day rather 

than at random). The CERHR expert 

panel excluded ‘‘aberrantly low’’ fetal 

weights from one litter in this study and 

calculated a BMDL greater than 300 

ppm for this endpoint after removing 

those outlier data (CERHR, 2002a, 

2003a, and 2004a). TERA calculated a 

similar BMDL when analyzing the same 

data set (TERA, 2004). Further, the 

reference list in the documentation on 

the TLV indicates that ACGIH did not 

review and evaluate all the studies 

available prior to the development of 

the recommended exposure limit. For 

example, key supporting articles that 

reported disruption of estrous cycles 

(Yamada et al., 2003 and Sekiguchi et 

al., 2002) were not discussed in the TLV 

documentation. Further, ACGIH did not 

provide 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) benchmark dose (BMD) 

analysis of the reduced pup weight data 

(CERHR, 2002a; TERA, 2004) results in 

a higher BMDL (roughly 300 ppm) than 

those for reproductive effects; 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). 

We note that, even if EPA had 

selected the ACGIH TLV as our basis for 

assessing the risks of nPB, we would 

have proposed the same determinations. 

In the specific coatings application that 

we propose to find acceptable subject to 

use conditions at the Lake City Army 

Ammunition Plant, exposure data 

showed an ability to meet an exposure 

level of 10 ppm, with the vast majority 

of measurements below that value. 

Thirty-four of 35 samples had 

concentrations below 10 ppm, and the 

mean concentration for the plant was 

less than 4 ppm (Lake City Army 

Ammunition Plant, 2004). For the 

aerosol and adhesive end uses, it would 

be even more difficult to achieve an 

exposure level of 10 ppm than to 

achieve a level in the range that EPA is 

considering (17 to 30 ppm). Thus, we 

would have proposed the same 

decisions for nPB of acceptable, subject 

to use conditions for coatings and 

unacceptable for aerosols and adhesives 

using the ACGIH’s TLV of 10 ppm to 

assess health risks. 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. This small 

difference is well within the uncertainty 

required to extrapolate a benchmark 

dose from an experimental study in rats 

to an occupational exposure limit in 

humans. 

E. Community Exposure Guideline 

In this proposal, EPA is using a 

community exposure guideline (CEG) of 

1 ppm to evaluate potential health risks 

among populations living near facilities 

using nPB. This community exposure 

guideline is an estimate of a continuous 

inhalation exposure (averaged over 24 

hours per day, 7 days per week) to the 

general public (including sensitive 

subgroups) that is likely to be without 

an appreciable risk of adverse health 

effects during a lifetime. 

Based on EPA risk assessment 

guidelines (US EPA, 1994b), the CEG 

was derived using the lowest BMDL 

from effects listed in Table 6 as the 

point of departure (110 ppm for 

vacuolation in the liver of animals in 

the F1 generation of WIL, 2001). The 

HEC was calculated as follows: 

110 ppm x (6 hours exposure in study/ 

24 hours avg time) x (7 days/7 days) 

= 28 ppm 

EPA used an uncertainty factor of 3 

for extrapolation from animals to 

humans, as discussed above in section 

VI.A, and an uncertainty factor of 10 for 

variability within the general 

population, consistent with EPA’s RfC 

guidelines. Dividing the HEC of 28 ppm 

by 30 yields a community exposure 

guideline of approximately 1 ppm. If we 

had used sperm motility (HEC of 42 

ppm based on a BMDL of 169 ppm) or 

number of estrous cycles (HEC of 40 

ppm based on a BMDL of 162 ppm) as 

starting points, we would calculate the 

same approximate CEG value. We note 

that, following RfC guidelines, EPA’s 

community exposure guideline includes 

a number of conservative assumptions, 

including exposure adjustments to 

protect an individual exposed for up to 

24 hours a day for 70 years (U.S. EPA, 

1994b, p. 1–5). 

EPA evaluated general population 

exposure using EPA’s SCREEN3 (U.S. 

EPA, 1995b) air dispersion model to 

assess the likely maximum 

concentration of nPB from single 

sources.18 EPA used data collected from 


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precision cleaning also would not result in 

emissions exceeding the CEG. 

19Smog, also known as ground-level ozone, is 

produced from emissions of volatile organic 

compounds that react under certain conditions of 

temperature and light. 

actual facilities (Swanson, 2002) to 

characterize two scenarios: (1) A typical 

large, high-use adhesive application 

facility where the closest resident is 100 

meters away; and (2) a smaller facility 

with average-use adhesive application 

in an urban area, where the nearest 

resident is only 3 meters away. The 

results indicated that modeled 

exposures in either scenario did not 

exceed the CEG of 1 ppm. The highest 

exposure modeled was 0.24 ppm at a 

distance of 3 meters away from the 

source in the urban scenario, while most 

other exposures were at least an order 

of magnitude lower (ICF, 2003; ICF, 

2006a). Because the community 

exposure guideline was not exceeded 

for any of the exposure scenarios in this 

conservative screening approach, EPA 

has concluded that nPB exposure to 

populations living close to facilities 

using nPB is not a concern for purposes 

of determining the acceptability of nPB 

under the SNAP program. 

VI. What listing is EPA proposing for 

each end use, and why? 

In this rule, EPA is proposing to find 

nPB unacceptable in adhesive and 

aerosol solvent end uses, and acceptable 

subject to use conditions in the coatings 

end use. The proposed listings, 

summarized in Table 9, are intended to 

allow the use of nPB where it does not 

pose a human health risk significantly 

greater than other substitutes and 

prohibit nPB’s use where nPB exposure 

cannot be maintained, or is unlikely to 

be maintained, at even the highest level 

considered in this proposal (i.e., 30 

ppm). We also are taking comment on 

an alternate approach of finding nPB 

acceptable subject to use conditions in 

the above end uses (see Section VII.A). 

TABLE 9.—PROPOSED DECISIONS BY END USE AND SECTOR

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

Aerosols: 

Aerosol solvents .......................................... Unacceptable ................................................... Acceptable, subject to use conditions.2

Adhesives, Coatings, and Inks: 

Coatings ...................................................... Acceptable, subject to use conditions 1 ........... Acceptable, subject to use conditions.2

Adhesives .................................................... Unacceptable ................................................... Acceptable, subject to use conditions.2

1 Use of nPB in this end use is limited to coatings at facilities that, as of May 30, 2007, have provided EPA information demonstrating their 

ability to maintain acceptable workplace exposures (i.e., the Lake City Army Ammunition Plant). 2 Use conditions would include proposed requirements that users must (1) meet an exposure limit of 20 ppm on an eight-hour time-weighted 

average, (2) monitor workers’ exposure to nPB using a personal breathing zone sampler on an eight-hour time-weighted average initially and periodically (every 6 months or longer, depending on the concentration during initial monitoring), and (3) keep records of the worker exposure data 

on site at the facility for at least three years from the date of the measurement. 

A. Aerosol Solvents 

In this rule, EPA proposes to find nPB 

unacceptable in the aerosol solvent end 

use. There are a number of aerosol 

solvent alternatives that do not pose any 

risk for ozone depletion or for ground 

level smog formation.19 EPA’s greatest 

concern with nPB-based aerosols is that 

users of nPB as an aerosol solvent 

cannot reliably maintain exposures at 

sufficiently low levels to ensure that 

workers are protected. This finding is 

based on measured exposure data and 

model estimations indicating the 

likelihood of elevated concentrations 

associated with nPB-based aerosols 

given typical ventilation conditions. A 

number of other acceptable solvent 

alternatives are available that can be 

used at exposure levels below their 

respective acceptable exposure limits. 

Ventilation conditions are an 

important consideration in evaluating 

potential risks within this end-use 

category. ‘‘Benchtop cleaning’’ of 

individual parts, which is feasible under 

exhaust hoods or in spray booths with 

adequate ventilation, comprises 25% or 

less of the market involving ODS 

substitutes for aerosols (U.S. EPA, 

2004). According to industry 

information and several commenters, 

the majority of the market for nPB-based 

aerosols involves in-place applications 

requiring a portable aerosol, such as 

cleaning energized electrical contacts 

and switches, maintenance in 

underground mines, or cleaning active 

elevator motors (CSMA, 1998; U.S. EPA, 

2004; Williams, 2005). These 

applications often occur in tightly 

confined spaces where it is not feasible 

to install ventilation equipment or 

remove parts to ventilated areas (CSMA, 

1998; Linnell, 2003; Werner, 2003). 

Other acceptable substitutes, such as 

blends of HFEs or HFCs and transdichloroethylene, are available in these 

end uses. One commenter also 

suggested that a user of an nPB-based 

aerosol will assume that they are being 

provided with a product that offers 

similar margins of safety as the product 

being replaced (i.e., HCFC–141b) and 

therefore can be used under the same 

conditions (Werner, 2003). 

The likelihood that nPB aerosol 

solvents would be used in poorly 

ventilated spaces is of particular 

concern given the likelihood of elevated 

exposure levels. The exposure data from 

aerosol solvent use are extremely 

limited. These data are from simulations 

of a number of situations where nPB 

might be used, such as benchtop 

cleaning of electronics and cleaning 

automotive brakes, rather than data from 

facilities currently using nPB in 

manufacturing or maintenance 

processes. Thus, the available exposure 

data may not be representative of 

ventilation levels normally used with 

nPB-based aerosols and may not 

adequately represent exposure levels 

during in-place cleaning, industry’s 

most common application for nPB-based 

aerosols. The distribution of exposure 

levels in the seven samples ranging from 

5.5 to 32 ppm corresponded to the range 

of ventilation rates reported—0, 300, 

640, and 1900 cfm—with the highest 

ventilation rate resulting in the lowest 

exposure levels and the lower 

ventilation levels resulting in the values 

above 30 ppm. The ventilation rate most 

consistent with use in a confined space 

for in-place cleaning, 0 cfm, resulted in 

half the exposures (one of two) 

exceeding 30 ppm. The highest 

ventilation rate, 1900 cfm, occurred at a 

vented booth, which would not be 

feasible to install for in-place cleaning 

applications—the majority of 

applications for nPB-based aerosols. The 

middle ventilation rates of 300 and 640 

cfm occurred during use of a fan for an 

entire room (regional ventilation), as 

might be expected for benchtop cleaning 

(Confidential submission, 1998), but not 

for in-place cleaning in confined spaces. 

In modeling nPB exposure from aerosol 

solvent use at a low ventilation rate of 


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450 cfm, a level that might be expected 

during benchtop cleaning, 8-hour 

average concentrations of 16.5 to 33 

ppm are predicted, depending on the 

amount of nPB used (ICF, 2006a). 

Exposure levels for confined spaces 

with even lower ventilation rates, as we 

would expect for in-place cleaning, 

would be even higher, likely exceeding 

the high end of the range that EPA is 

considering. Short-term exposures of 

370 and 1,100 ppm taken from workers’

collars in a room with regional 

ventilation at 640 cfm, when averaged 

over an 8-hour period, resulted in 

exposure levels of 12 and 34 ppm. 

These exposures occurred as a result of 

using nPB over a period up to 15 

minutes, so it is likely that users would 

have greater exposure than 30 ppm if 

they used nPB for longer than 15 

minutes per day, as with multiple uses. 

The available data sets have a small 

sample size, may not be representative 

of in-place cleaning in confined spaces, 

and do not provide EPA with 

convincing data that nPB is likely be 

used safely, at exposure levels at or 

below the highest level in the range we 

are considering for evaluation of 

acceptability. 

EPA is concerned that many, and 

perhaps most, uses of nPB aerosol 

solvents result in a high probability of 

exposures at or above even the upper 

end of the range of exposures that the 

Agency is considering to be potentially 

acceptable. EPA is aware of no data on 

ventilation levels demonstrating that 

most users of aerosol solvents, or of nPB 

in particular, would use aerosols in 

locations with sufficiently high 

ventilation levels to protect human 

health (e.g., 1900 cfm or greater). We 

request data on worker exposure levels, 

typical ventilation rates, and patterns 

for usage of nPB-based aerosols, 

considering both benchtop and in-place 

use. 

EPA has found numerous other 

aerosol solvents acceptable. These 

aerosol solvents can be used safely in a 

manner consistent with their respective 

acceptable exposure limits. This is 

highlighted in a study comparing 

concentrations of eight different 

chemicals that are acceptable under the 

SNAP program in aerosol formulations: 

HFE-7100, HFE-7200, trans-1,2- 

dichloroethylene, HCFC-225ca and 

-225cb, acetone, pentane, and HFC134a. In this study, with ventilation of 

only 48 cfm, 8-hr TWA exposure from 

the different chemicals varied from 35.5 

ppm to 194.0 ppm, and all chemicals 

met their respective recommended 

exposure levels (ICF, 2006a). As 

discussed above in section V.A, when 

these concentrations are adjusted for the 

chemicals’ respective molecular 

weights, they would correspond to nPB 

concentrations of 29.5 to 394.4 ppm, 

which is at or above even the highest 

level the Agency would consider 

acceptable. The ventilation level in this 

study is closer to what we would expect 

in a confined space where fans or vents 

cannot be installed, as for in-place 

cleaning. Based on these considerations, 

the Agency believes that nPB used as an 

aerosol solvent would impose 

significantly more risk to human health 

than other alternatives available for this 

end use. 

B. Adhesives 

EPA proposes to find nPB 

unacceptable in the adhesive end use. 

As for aerosol solvents, we found that 

some alternative adhesive formulations 

could reduce particular environmental 

risks more than nPB, such as generation 

of ground level ‘‘smog’’ or ozone 

depletion potential. However, we find 

the greatest concern in this end use is 

with nPB’s human health effects. We 

propose to find nPB unacceptable in 

adhesives because it poses significantly 

greater risk to human health as 

compared to other available alternatives 

in this end use. 

In the June 2003 NPRM, we initially 

proposed to find nPB acceptable in 

adhesives based on the SNAP program 

principle that ‘‘EPA does not intend to 

restrict a substitute if it poses only 

marginally greater risk than another 

substitute * * *. The Agency also does 

not want to intercede in the market’s 

choice of available substitutes, unless a 

substitute has been proposed or is being 

used that is clearly more harmful to 

human health and the environment than 

other alternatives.’’ (68 FR 33294, citing 

the original March 18, 1994 SNAP rule 

at 59 FR 13046). At the time of the 

proposal, we considered data from 

NIOSH monitoring and health hazard 

evaluations for three facilities using 

nPB-based adhesives. At two of the 

three facilities, NIOSH worked together 

with the companies to install state-ofthe-art ventilation equipment. Looking 

at exposure data from all workers after 

ventilation improvements, we believed 

it would be possible for facilities to 

meet the proposed AEL of 25 ppm (68 

FR 33294). 

• One public commenter suggested 

that EPA should reconsider whether 

industrial exposures consistently occur 

and/or can be controlled to a level at or 

below 25 ppm (Werner, 2003). We 

reevaluated the exposure data for the 

two plants that had improved their 

ventilation, focusing on exposure to the 

workers that receive the highest 

exposures because they directly spray 

the nPB-based adhesive. We found that, 

even in the best case, a substantial 

number of workers spraying nPB-based 

adhesives would be exposed above the 

highest level in the range we are 

considering. 

• NIOSH investigators initially 

reported that mean exposures to nPB 

ranged from 60 to 381 ppm (8-hour time 

weighted averages) at three different 

foam-fabrication facilities using nPBbased adhesives (NIOSH, 2000a, 2000b, 

2001, 2002a, 2002b, 2003a). In one 

facility, average (mean) nPB exposures 

were reduced from 169 ppm to 19 ppm, 

following installation of ventilation 

equipment (NIOSH, 2000b). Although 

use of spray booths at this facility 

reduced the average exposure level to 

19.4 ppm for all workers, the majority 

of the sprayers directly using nPB-based 

adhesives still would be exposed at 

unacceptably high levels. Out of 

fourteen sprayers at the Custom 

Products facility: 

• Six, or 43% of sprayers, would be 

exposed to more than 30 ppm. 

• Nine, or 64% of sprayers, would be 

exposed to more than 25 ppm. 

• Ten, or 71% of sprayers, would be 

exposed to more than 20 ppm. 

• Eleven, or 79% of sprayers, would 

be exposed to more than 15 ppm. 

• Thirteen, or 93% of sprayers, would 

be exposed to more than 10 ppm. 

At another facility using nPB-based 

adhesives, the average exposure was 

reduced from 58 pm to 19 ppm after the 

company installed ventilation 

recommended by NIOSH (NIOSH, 

2001). Data on exposure for sprayers 

found fewer individuals receiving high 

exposures than at the facility monitored 

in NIOSH (2000b), but 65% (22 of 34) 

of exposure samples for sprayers were 

higher than 15 ppm, 33% (11 of 34) 

were higher than 20 ppm and 15% (5 of 

34) were higher than 25 ppm after 

improving ventilation. 

Overall, 42% of sprayers in these two 

facilities using nPB-based adhesives 

were exposed to concentrations of nPB 

greater than 20 ppm (21 of 48 workers) 

and 23% (14 of 48 workers) were 

exposed to more than 25 ppm, even 

after installing state-of-the-art 

ventilation with assistance from NIOSH. 

Sprayers had significantly higher 

individual exposures than workers who 

did not work directly with the nPBbased adhesive. 

In response to public comment and 

additional information available to EPA 

since the June 2003 NPRM, we now 

propose that use of nPB-based adhesives 

poses significantly higher risks to 

human health than other available 

adhesives. Since the June 2003 NPRM, 

there have been a number of reports of 


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workers working with nPB-based 

adhesives that have suffered adverse, 

persistent neurological effects that 

resulted in hospitalization (Beck and 

Caravati, 2003, and Majersik et al., 2004, 

2005; Calhoun County, 2005; Miller, 

2005; Raymond and Ford, 2005). Based 

on data from actual facilities using 

adhesives, it is estimated that a facility 

using nPB with average adhesive 

application rates and average ventilation 

rates would have exposure levels of 

approximately 60 ppm on an 8-hr timeweighted average (ICF, 2006a). 

Modeling of exposures at high adhesive 

application rates and average or lower 

ventilation rates resulted in exposures 

of approximately 250 to 2530 ppm (ICF, 

2006a). We believe these modeling 

results show that most adhesive users 

would exceed acceptable exposure 

levels by significant margins and that it 

is unlikely that adhesive users would be 

able to use nPB safely. 

Considering the exposure data for 

nPB-based adhesives, we believe it is 

unlikely that, even with improved 

ventilation, adhesive users could reduce 

exposures to acceptable levels on a 

consistent basis. In the best case seen, 

a facility with low to average initial 

exposure levels was able to reduce 

exposures to the middle of the range 

EPA is considering after extensive 

assistance from NIOSH in installing 

state-of-the-art ventilation. We expect 

that many facilities will begin with 

higher exposure levels and will not have 

the same level of assistance to improve 

ventilation, thus making it unlikely that 

they would achieve acceptable 

exposures. Given the information above, 

we are concerned that nPB-based 

adhesives cannot be reliably used in a 

manner that protects human health. We 

request comment and further data on 

whether it is feasible to use nPB-based 

adhesives with worker exposure levels 

consistently at or below any of the 

values in the range of exposure levels 

that EPA is considering potentially 

acceptable (i.e., 17 to 30 ppm). 

The available information indicates 

that all acceptable carrier solvents in 

adhesives other than nPB have projected 

or actual exposure less than the 

appropriate workplace exposure limit 

EPA used in finding those substitutes 

acceptable. Examples of other carrier 

solvents currently used in adhesives 

and acceptable under the SNAP 

Program include hydrocarbon solvents, 

acetone, methylene chloride, and water. 

EPA finds that there are other available 

alternatives that pose significantly less 

risk to human health and the 

environment compared to nPB in the 

adhesives end use. 

During the public comment period on 

the June 2003 NPRM, one commenter 

representing the adhesives industry 

stated that there are some small but 

critical applications that require 

nonflammability and high solvency 

(Collatz, 2003). The commenter did not 

specify what those applications are, and 

whether there was information showing 

that other types of adhesives, such as 

those using water, flammable solvents, 

or methylene chloride, are technically 

infeasible in these applications. We 

request comment and data on whether 

there are any unique applications in the 

adhesives end use for which there are 

no technically feasible alternatives other 

than nPB and thus, for which nPB 

should be allowed. If so, and if 

determined that nPB should be 

unacceptable except where no other 

substitutes are feasible, we would 

consider finding nPB acceptable subject 

to narrowed use limits, with 

requirements for each end user to 

perform a demonstration that there are 

no other technically feasible alternatives 

for their particular site, to install local 

exhaust ventilation equipment designed 

to reduce exposures to acceptable levels 

and to perform worker exposure 

monitoring. Alternatively, if there was 

sufficient information provided during 

the public comment period showing 

that there are applications in which nPB 

can be safely used, we would consider 

finding nPB acceptable in adhesives, 

subject to use conditions requiring 

installation of local exhaust ventilation 

and worker exposure monitoring. This 

would allow for use of nPB in any 

applications where it may be used safely 

if any such applications exist. 

C. Coatings 

We are proposing to find nPB 

acceptable, subject to use conditions, for 

facilities that, as of May 30, 2007, have 

provided EPA information 

demonstrating their ability to maintain 

workplace exposure levels below even 

the minimum level of the range of 

exposures that EPA is considering to be 

potentially acceptable (i.e., 17 to 30 

ppm). The SNAP submission with 

information on coatings was made for a 

single facility and EPA is unaware of 

anyone else interested in using nPB in 

this end use. Therefore, there are 

currently no analyses indicating 

whether nPB would pose significantly 

greater risks in any coating applications 

other than this facility. Workplace 

exposure levels to nPB from 

ammunition sealant at Lake City Army 

Ammunition Plant ranged from less 

than 1 ppm up to 21 ppm on an eighthour time-weighted average. Thirty-four 

of 35 samples had concentrations below 

10 ppm, and the mean concentration for 

the plant was less than 4 ppm (Lake City 

Army Ammunition Plant, 2004). The 

vast majority of measurements show 

worker exposure well below the lowest 

level in the range of exposures that EPA 

is considering. Thus, we believe that 

nPB can be used as safely as other 

acceptable solvents used at their 

acceptable exposure limits under the 

conditions at this facility. 

Other acceptable substitutes for 

ozone-depleting substances in coatings, 

in general, include oxygenated solvents, 

hydrocarbon solvents, terpenes, 

hydrofluoroethers 7100 and 7200, 

benzotrifluorides (include 

parachlorobenzotrifluoride), 

monochlorotoluenes, trans-1,2- 

dichloroethylene, chlorinated solvents, 

water-based formulations, and highsolids formulations. In the particular 

application for ammunition coatings, 

the submitter evaluated a large number 

of alternatives and found that n-propyl 

bromide was the only one of 29 solvents 

tested that could meet performance 

specifications at this facility (Harper, 

2005). Thus, it is not clear that there are 

other substitutes available for this 

specific application, and exposure data 

show that in this specific application, 

nPB can be used in a way that does not 

pose significantly greater risks to human 

health compared to other acceptable 

substitutes in the coatings end use. 

VII. What other regulatory options did 

EPA consider? 

EPA considered several different 

options, but we prefer the approach 

proposed in this rule. We also take 

comment on the options discussed 

below. 

A. Alternate Option for Comment: 

Acceptable With Use Conditions 

Requiring Exposure Limit and 

Monitoring 

We also take comment on a proposed 

alternate approach in which nPB would 

be acceptable subject to use conditions 

in all the end uses addressed in this 

action. Under this alternate approach, 

users would meet an exposure limit, 

monitor exposure of workers using nPB, 

and keep records to demonstrate 

compliance with these requirements. 

For purposes of this alternative 

proposal, we selected 20 ppm to use as 

an exposure limit above which use 

would be unacceptable, and 10 ppm as 

an action level that allows reduced 

exposure monitoring, for the reasons 

discussed below in section VII.A.1, 

‘‘Use Conditions and Their Rationale.’’

However, we are soliciting comment on 

whether a different exposure level 

within the 17 to 30 ppm range should 


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20See 29 CFR 1910.1052(d)(4)(i). 

be selected. The following requirements 

would apply at each facility where nPB 

is used: 

Exposure Limit 

The owner or operator would be 

required to ensure that workers using 

nPB are exposed to no more than 20 

ppm on an 8-hour time-weighted 

average. The exposure limit could be 

met through engineering controls (e.g., 

ventilation equipment), work practices, 

or reduced use of nPB. 

Initial Worker Exposure Monitoring 

For each facility where nPB is used, 

the owner or operator of the facility 

would be required to ensure that 

personal breathing zone air samples of 

each nPB user’s exposure would be 

collected on an eight-hour, timeweighted average initially within 90 

days after a final rule becomes effective. 

Monitoring measurements may be taken 

with an organic chemical monitoring 

badge on the collar or a tube filled with 

charcoal on the collar. 

Periodic Exposure Monitoring 

(1) The owner or operator of the 

facility would be required to ensure that 

personal breathing zone air samples of 

user exposure are collected periodically 

on an eight-hour, time-weighted average 

depending on the results of the most 

recent set of exposure data. A 

monitoring program could be instituted 

by the company or by the nPB supplier 

for that facility. Periodic sampling 

requirements would be based on the 

most recent monitoring results, as 

follows: 

TABLE 10.—ALTERNATIVE APPROACH EXPOSURE LEVELS AND PERIODIC EXPOSURE MONITORING

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

all measurements at or below 10 ppm .................................... is not required to perform periodic exposure monitoring.

all measurements at or below 20 ppm, with some measurements above 10 ppm.must take personal breathing zone samples again at least once in the next six 

months. 

at least one measurement above 20 ppm ............................... must stop using nPB in the application exceeding the exposure limit until exposure data show that 20 ppm can be consistently met in the vast majority of 

cases. 

unknown, in cases of new workplace conditions increasing 

exposure or new applications of nPB.

must take personal breathing zone samples as a test before using nPB in new 

industrial applications or conditions, or within 7 days of an emergency caused 

by a leak, rupture or breakdown, and use this value to determine the next time 

monitoring is required. 

(2) For periodic monitoring, the 

owner or operator would be allowed 

either to monitor each nPB user’s 

exposure, or to monitor exposure of a 

representative nPB user in each job 

classification in a work area during 

every work shift, where the monitored 

nPB user is expected to have the highest 

exposure. 

(3) The owner or operator would be 

allowed to discontinue the periodic 8- 

hour TWA monitoring for nPB users at 

the facility where at least two 

consecutive sets of measurements taken 

at least seven days apart are below 10 

ppm. 

Monitoring for New Conditions or 

Applications 

Whenever there is a change in 

workplace conditions that may increase 

exposure or whenever a new application 

of nPB is introduced, the owner or 

operator would be required to take 

personal breathing zone samples 

accounting for all nPB users as a test 

before using nPB in manufacturing or 

repair. These could be either samples 

for each nPB user or samples 

representing each job classification in a 

work area during a work shift, so long 

as the samples are based on the user 

with the likely highest exposure. 

Examples of changes in workplace 

conditions that may increase exposure 

include changes in production, process 

control equipment, or work practices, or 

a leak, rupture, or other breakdown.20

Examples of introduction of a new 

application of nPB include aerosol 

contact cleaning in a location with 

regional ventilation or natural 

ventilation, where previous 

measurements were carried out on 

workers in a location with local 

ventilation. If the change occurs because 

of an unpredictable emergency, then the 

owner or operator would need to ensure 

exposure monitoring takes place within 

7 days of the change. 

Sampling Methods and Accuracy 

Exposure samples would be required 

to be analyzed either by NIOSH method 

1003 for halogenated hydrocarbons or 

method 1025 for 1-bromopropane and 2- 

bromopropane or by another method 

that is accurate to ±25% at the 95 

percent confidence level. 

Recordkeeping Requirements 

The owner or operator of the facility 

would be required to keep records of the 

monitored exposure data at the facility 

for at least three years from the date the 

measurements were taken for purposes 

of this rule. These records would be 

required to be made available in the 

event of a facility inspection or a request 

for the data by EPA. Note that the EPA’s 

recordkeeping requirement does not 

affect OSHA’s standard on access to 

employee exposure and medical 

records, which requires retaining any 

exposure records for at least 30 years (29 

CFR 1910.1020(d)(ii)). 

The regulatory listings by end-use 

under this alternate approach that the 

Agency requests comment on would be 

as follows: 

BILLING CODE 6560–50–P 


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BILLING CODE 6560–50–C 


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21 In its methylene chloride standard, OSHA 

defined representative sampling as follows: ‘‘The 

employer has taken one or more personal breathing 

zone air samples for at least one employee in each 

job classification in a work area during every work 

shift, and the employee sampled is expected to have 

the highest * * * exposure.’’ (29 CFR 

1910.1052(d)(1)(ii)(A)). 

22The action level is the exposure level that is 

half the 8-hour TWA exposure limit. In this case, 

the action level would be10 ppm. 

23OSHA’s standard on access to employee 

exposure and medical records requires retaining 

exposure records for at least 30 years (29 CFR 

1910.1020(d)(ii)), and these requirements would not 

be affected by this regulation. 

1. Use Conditions and Their Rationale 

The major provisions of the use 

conditions and the related issues that 

EPA considered in developing the 

alternate approach that we are taking 

comment on are as follows: 

Exposure limit. A requirement to meet 

a workplace exposure limit would be an 

interim measure to ensure that nPB will 

be used safely until OSHA issues a final 

permissible exposure limit (PEL) under 

the Occupational Safety and Health Act. 

In the event that OSHA issues a final 

PEL, it would supersede EPA’s exposure 

limit. EPA is specifically deferring to 

OSHA, and has no intention to assume 

responsibility to displace OSHA’s 

authority under Public Law 91–596. 

EPA’s exposure limit would not preempt the authority of OSHA to take 

regulatory or enforcement action with 

respect to exposure to this substance. 

This is made clear by the Clean Air Act 

under which EPA would promulgate 

this regulation (Subchapter VI—

Stratospheric Ozone Protection), which 

provides at 42 U.S.C. 7610 in pertinent 

part: ‘‘* * * this chapter [Chapter 85—

Air Pollution Prevention] shall not be 

construed as superseding or limiting the 

authorities, under any other provision of 

law, of the Administrator or any other 

Federal officer, department, or agency.’’

By issuing an exposure limit for nPB, 

EPA’s intention would be to fill existing 

regulatory gaps during the interim 

period of substitution away from ozonedepleting compounds and provide the 

needed margin of protection for human 

health and the environment until OSHA 

develops other regulatory controls or 

standards under appropriate authorities. 

As discussed above in section IV.E.1, 

EPA is considering exposures within the 

range of 17 to 30 ppm as potentially 

acceptable in order to determine 

whether nPB may be used safely in each 

end use. For purposes of having a clear 

compliance target under this alternative 

approach for public comment, we are 

using 20 ppm as the exposure limit 

above which use would be 

unacceptable. We chose this value 

because we expect it to be protective 

against the reproductive and 

developmental effects identified 

previously (live litter size, sperm 

motility, estrous cycles). Worker 

exposure monitoring. The worker 

exposure monitoring requirements 

under the use conditions in the alternate 

approach were modeled after OSHA’s 

requirements for monitoring for 

methylene chloride. 29 CFR 

1910.1052(d). We expect that the 

regulated community would be familiar 

with this approach and there might be 

fewer changes for regulated businesses 

if OSHA later were to establish a 

workplace standard for nPB. Because 

the exposure limit would be an 8-hr 

TWA value that is derived from studies 

that measured exposure via inhalation, 

the proposed use conditions require the 

owner or operator to monitor 8-hr TWA 

values that measure workers’ exposure 

in the breathing zone (e.g., samples from 

a worker’s collar). We are not proposing 

to monitor short-term exposures because 

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 or potentially 

acceptable exposure levels (ERG, 2004). 

Option for monitoring representative 

set of workers. Personal breath zone 

samples could be taken either from each 

worker using nPB or from a 

representative 21 set of exposed workers 

expected to have the highest exposure. 

Allowing exposure monitoring from 

representative workers using nPB, rather 

than requiring separate monitoring for 

each individual using nPB, would 

reduce overall compliance burden, 

while still detecting any exposure levels 

in excess of the exposure limit and 

avoiding underestimates of exposure. 

Initial monitoring. Users already using 

nPB would need to undergo exposure 

monitoring no later than 90 days after 

the date the final rule becomes effective. 

A user that has never used nPB before 

would need to perform initial 

monitoring before beginning to use nPB 

in the facility’s industrial applications. 

Periodic monitoring. Monitoring 

would have to be performed 

periodically on a schedule based on the 

results of the most recent set of 

exposure monitoring data. Monitoring 

from workers’ personal breathing zone 

would be required during the next six 

months if an initial measurement finds 

exposure levels between the action 

level 22 and the 8-hour TWA exposure 

limit. No periodic monitoring would be 

required if initial measurements are 

below the action level. The action level 

would be the value that is half the 

exposure limit, in this case 10 ppm. 

OSHA standards also set an action level 

of half the PEL. 

Under the alternate approach, 

monitoring would no longer be required 

where the most recent exposure 

monitoring data found all worker 

exposures at or below 10 ppm. OSHA 

rules also reduce monitoring 

requirements for exposures below the 

action level because if measured values 

are that low, it is unlikely that any 

measurement will exceed the PEL 

unless a major change to the process 

occurs. 

Monitoring for changes in workplace 

conditions or nPB use. New monitoring 

would be required if an event occurs 

that would make the most recent set of 

monitoring data no longer 

representative. EPA would expect that 

the owner or operator would plan new 

applications of nPB or changes to 

control equipment or work practices 

and would perform a test for worker 

exposure levels before using nPB on a 

regular basis in that application. In the 

case of an emergency, such as a 

breakdown of ventilation equipment or 

a leak, we would expect exposure 

monitoring to be performed as soon as 

possible, and no later than 7 days after 

the change in workplace conditions. 

This period is intended to give an owner 

or operator time to locate and purchase 

exposure monitoring equipment in an 

emergency where the equipment may 

not already be available at the facility. 

Monitoring method and accuracy. We 

take comment on the use of NIOSH 

methods 1003 and 1025 (NIOSH, 2003b 

and c) for analyzing nPB exposure 

under the proposed alternate approach. 

Several of the studies that supplied EPA 

with exposure data used this method 

and they are standardized methods 

prepared by NIOSH, a recognized 

authority on industrial hygiene. In 

addition, we would allow other 

methods that are accurate to ± 25% at 

the 95 percent confidence level. Based 

on the accuracy of available methods, 

most OSHA standards require exposure 

monitoring accurate to 25% at the 95 

percent confidence level, as in the 

methylene chloride standard (29 CFR 

1910.1052(d)(1)(iii)(A)) and other OSHA 

standards. 

Recordkeeping requirements. We 

would require that users keep records of 

the worker exposure data for three years 

from the date the measurement is 

taken.23 This would provide 

information allowing EPA to determine 

if facilities are complying with the 

exposure limit and if workers exposed 

to nPB are sufficiently protected. 

Responsibility for meeting 

requirements. Under the alternate 

approach, the owner or operator of a 


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facility using nPB would be responsible 

for meeting the rule’s use conditions. 

2. Advantages and Disadvantages of the 

Alternate Approach 

Setting use conditions that require 

users to meet an exposure limit and to 

monitor and keep records to 

demonstrate achieving the limit would 

protect the health of nPB users while 

giving industry more flexibility and 

more options for ODS substitutes, 

compared to finding nPB unacceptable. 

This could be especially useful for users 

of HCFC–141b as an aerosol solvent that 

are seeking an effective ODS substitute. 

If there were any situations in which 

other available alternatives did not 

provide as good performance, nPB 

would still be available as an option, 

provided the use conditions could be 

met. The monitoring requirements 

would encourage good industrial 

hygiene and safe use of nPB. 

Considering the list of use conditions 

above, we believe that setting use 

conditions requiring an exposure limit, 

worker exposure monitoring, and 

recordkeeping would be complex and 

potentially confusing. Requiring users to 

meet the exposure limit, although 

providing greater potential flexibility, 

also would provide less certainty about 

how to comply. A user could spend 

considerable time and expense trying to 

meet the exposure limit, only to find 

that it is not achievable. 

Given the limited circumstances 

under which we expect aerosol and 

adhesive users could meet an acceptable 

exposure limit and given the availability 

of other, less toxic alternatives in both 

of these end uses, EPA’s preferred 

option is to find nPB unacceptable in 

aerosols and adhesives. Further, 

considering that without regulatory 

requirements, the users of nPB at the 

Lake City Army Ammunition Plant have 

been operating with the vast majority of 

exposure levels below 17 ppm, the low 

end of the range of exposures that EPA 

is considering to be potentially 

acceptable (Lake City Army 

Ammunition Plant, 2004), it appears 

unnecessary to require an exposure 

limit in that application. 

B. Regulatory Options Where nPB 

Would Be Acceptable With Use 

Conditions Requiring Specific 

Equipment 

We considered use conditions for the 

adhesive and aerosol solvent end uses 

that would reduce the human health 

risks of using nPB by reducing exposure 

levels with requirements for installation 

and use of ventilation equipment. We 

also offer for comment use conditions 

that would require aerosol dispensing 

equipment that would reduce exposure 

levels and that would allow use of 

aerosol blends with reduced amounts of 

nPB to maintain acceptable exposure 

levels. 

1. Aerosols 

For the aerosol solvent end use, EPA 

considered proposing a requirement for 

installation of ventilation equipment. 

Such a use condition would need to 

specify and define which kinds of 

ventilation equipment would be 

necessary. For example, because one 

study on exposure levels found that 

exposure levels reliably fell in or below 

the range that EPA is considering (i.e., 

17 to 30 ppm) only where both local 

exhaust ventilation and regional 

ventilation equipment were used, a 

possible requirement would be for 

installation of both local exhaust 

ventilation and regional ventilation. We 

would define local exhaust ventilation 

as ventilation that removes vapors from 

a specific work location using ducts and 

fans. We would define regional 

ventilation as ventilation that moves air 

around in a large working area, such as 

one or more fans used for an entire 

room. A problem with requiring the 

type of ventilation equipment that all 

facilities must use is that it still might 

not provide enough ventilation in some 

situations and in other situations may 

be unnecessary to meet an exposure 

limit. 

Another approach for aerosols we 

considered was to require a specific 

level of ventilation. Possible criteria for 

the level of ventilation would be the air 

flow rate, in cubic feet per minute (cfm) 

or cubic meters per second, or the face 

velocity at the location where a user 

would work, in feet per minute (fpm) or 

meters per second face velocity. Based 

on both modeling and exposure data 

from one study (ICF, 2006a; Linnel, 

2003), an appropriate air flow rate for 

nPB-based aerosols would be greater 

than 1900 cfm and an appropriate face 

velocity would be 170 fpm. 

Alternatively, we considered requiring 

that facilities meet the guidelines for 

face velocity in spray booths from the 

ACGIH Ventilation Manual, in the range 

of 100 to 150 fpm, depending on the 

specific type of booth (ACGIH, 2002). 

These options would appear to 

provide greater flexibility for industry 

compared to finding nPB unacceptable 

in aerosol solvents. However, our 

understanding is that in most aerosol 

applications, it might not be feasible to 

install adequate ventilation, and thus, to 

reduce human health risks. In the case 

of benchtop cleaning or degreasing, 

such as during rework of individual 

parts that are not yet sufficiently clean, 

it is possible to transport the part to a 

hood or spray booth to provide 

sufficient ventilation. However, for 

applications that require in-place 

cleaning such as cleaning energized 

electrical contacts and switches, 

maintenance in underground mines, or 

cleaning hot elevator motors, it is not 

feasible to install ventilation equipment 

in place or to remove the parts for 

cleaning in ventilation equipment 

(CSMA, 1998; Linnell, 2003). 

Information available to EPA shows that 

benchtop cleaning is perhaps 25% or 

less of the market for the ODS being 

replaced in aerosols (US EPA, 2004) and 

that electrical contact cleaning makes 

up the vast majority of the market for 

nPB-based aerosols (Williams, 2005); 

thus, we expect that necessary 

ventilation cannot be installed in most 

aerosol applications for nPB. It would 

be difficult to explain and potentially 

confusing for users that an aerosol 

product may be used for cleaning in one 

location in a facility, but not in another, 

particularly when the ODS being 

substituted for could be used in all 

locations at safe exposure levels. 

Further, it would be difficult for EPA to 

enforce use conditions on ventilation 

equipment, because aerosols are 

portable and can easily be used outside 

of the ventilation equipment. Other 

acceptable substitutes, such as blends of 

HFEs or HFCs and transdichloroethylene, are available in these 

end uses. 

Another option that the Agency 

considered is finding nPB acceptable as 

an aerosol solvent, subject to the use 

condition that the aerosol product must 

be dispensed from a device or a system 

that is capable of maintaining 

acceptable exposure levels. The Agency 

is aware of at least two remote 

dispensing systems that could 

potentially mitigate exposures when 

used with low-pressure aerosols (Micro 

Care’s Trigger GripTM and Miller 

Stephenson’s Cobra Solvent Spray 

Cleaning Brush). Vendor data indicates 

that each aerosol can may last twice as 

long when using a remote dispensing 

system, compared to standard aerosol 

usage, indicating the ability to halve 

average exposure levels and reduce total 

solvent use (Micro Care, 2006). 

However, these types of systems would 

only be practical for benchtop cleaning, 

and not electrical contact cleaning, 

which comprises the majority of nPB 

aerosol use. The Agency requests 

comment on the viability and 

enforceability of a use condition 

requiring aerosol dispensing systems or 

other mitigation devices that could 

provide sufficient performance while 


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ensuring acceptable workplace exposure 

levels of nPB. 

Finally, the Agency considered 

another option by which the use of nPB 

would be acceptable in aerosol solvent 

uses, subject to the condition that users 

may only use blends of no more than 

fifty percent nPB and the remainder 

being propellants and other solvents, 

with manufacturer’s recommended 

exposure guidelines for compounds 

other than nPB being no lower than 100 

ppm. Based on exposure modeling 

performed on simulations of several 

commercial blends of nPB and another 

compound with a higher exposure limit 

(HFC–365mfc), it appears that users 

should be able to maintain exposures 

reliably below the range that EPA is 

considering for acceptability (i.e., 17 to 

30 ppm) when using a blend containing 

no more than fifty percent nPB by 

weight at the ventilation levels modeled 

(ICF, 2006a). We note that the modeling 

does not consider the possibility that a 

user might need to use more of a blend 

with less nPB, since nPB is more 

aggressive than many other solvents 

used in aerosols. It also does not address 

exposure levels in confined spaces as 

might occur during in-place cleaning 

with aerosols. We request comment and 

relevant, empirical data on the 8-hour 

TWA exposures that can be reliably 

attained when using blends containing 

50% or less of nPB by weight. In order 

to make this option enforceable, EPA 

would require users to keep records of 

nPB-containing aerosol blends they 

purchase, including the MSDS or other 

documentation of the proportion of nPB 

in the blend they use. We request 

comment on whether this is a feasible, 

enforceable option and whether it 

would provide useful flexibility to 

industry while ensuring adequate health 

protection. 

2. Adhesives 

EPA also considered use conditions 

for ventilation equipment or for specific 

ventilation levels for use of nPB-based 

adhesives. However, to date, we have 

found no study that demonstrates a 

ventilation option that could 

consistently achieve even the highest 

level within the range that EPA is 

considering for acceptability when 

using spray adhesives. Even with stateof-the-art ventilation equipment 

installed with the expert assistance of 

NIOSH, adhesives users were not able to 

lower exposure limits sufficient to 

protect the vast majority of their 

workers. Modeling of different levels of 

adhesive usage and ventilation, based 

on conditions at different facilities 

indicates that air flow rates would need 

to be more than 100,000 cfm. Even this 

high air flow rate might not be 

sufficient, since an air flow rate of 

28,500 cfm resulted in exposure levels 

of 3.5 to 35 times an acceptable 

exposure level, depending on the 

amount of adhesive used (ICF, 2006a, 

Att. D). Less toxic substitutes such as 

water-based adhesives and acetonebased adhesives are available in this end 

use. 

VIII. What are the anticipated costs of 

this regulation to the regulated 

community? 

As part of our rulemaking process, 

EPA estimated potential economic 

impacts of this proposed regulation. In 

our analysis, we assumed that capital 

costs are annualized over 15 years or 

less using a discount rate for 

determining net present value of 7.0%. 

Because the use condition for coatings 

still permits nPB’s use in the only 

known coatings application using nPB, 

we find no additional cost to the user 

community from this regulatory 

provision. We found that if this 

proposed rule were to become final, the 

cost to the user community of the 

unacceptability determinations, which 

are regulatory prohibitions on the use of 

nPB in adhesives and aerosols, would 

be in the range of $2.3 to $6.7 million 

per year for adhesive users and $36.3 to 

39.7 million per year for aerosol users. 

EPA also estimated the cost to the 

user community of the use conditions in 

the proposed alternate approach for 

aerosols, adhesives, and coatings. The 

requirements for users to meet an 

acceptable exposure limit and to 

perform exposure monitoring would be 

in the range of $42.3 to 67.5 million per 

year. The upper end of the range of 

estimated impacts assumes laboratory 

grade ventilation for aerosols, which we 

expect to be significantly more 

expensive than standard industrial fume 

hoods or spray booths (approximately 

$10,000 compared to $1,000 for each 

hood). For coatings, use of nPB is 

limited to a single facility that already 

performs workplace exposure 

monitoring, and thus, no new costs 

would be incurred. For aerosols and 

adhesives, we assumed the installation 

of fume hoods or spray booths, the use 

of personal protective equipment, and 

monitoring for 1.9 to 2.0 times per year 

on average. Using these assumptions, 

we calculated the cost of the use 

conditions in the proposed alternate 

approach at $18.0 to 24.0 million for 

adhesive users, and $24.3 to 43.5 

million for aerosol users. The estimated 

cost of the use conditions does not 

consider that some users could choose 

to switch to other alternatives at a lower 

cost. 

Estimated costs of the proposed 

regulation and proposed alternate 

approach are summarized in Table 13. 

For more detailed information, see 

section XIII.C. below and EPA’s analysis 

in the docket (US EPA, 2006). 

TABLE 13.—ESTIMATED COSTS OF REGULATORY OPTIONS EPA IS PROVIDING FOR COMMENT

Sector or end use Requirements under proposed rule Annual cost of 

proposed rule 

Requirements under alternate 

approach 

Annual cost of 

alternate 

approach 

Aerosol Solvents .... Cease use of nPB and switch to a different ODS substitute.$36.3 to 39.7 million.Achieve 20 ppm; exposure monitoring 

one or two times per year; Recordkeeping.

$24.3 to 43.5 million. 

Coatings ................. Decision applies to use nPB in coatings at facilities that, as of May 30, 

2007, have provided EPA information demonstrating their ability to 

maintain acceptable workplace exposures.

None ..................... Achieve 20 ppm; exposure monitoring, 

one or two times per year; recordkeeping.

None. 

Adhesives .............. Cease use of nPB and switch to a different ODS substitute.$2.3 to 6.7 million Achieve 20 ppm; exposure monitoring, 

one or two times per year; recordkeeping.

$18.0 to 24.0 million. 

Total ................ .............................................................. $38.6 to 46.4 million............................................................... $42.3 to 67.5 million. 


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IX. How do the decisions for EPA’s June 

2003 proposal compare to those for this 

proposal? 

Table 14 compares the acceptability 

determination and evidence cited in the 

June 2003 proposal and this proposal. 

TABLE 14.—n-PROPYL BROMIDE ACCEPTABILITY DECISION

Proposed decision 2003 proposed rule Current proposed rule—preferred proposal 

Industrial End Use #1: Aerosol Solvents ........... Acceptable, Subject to a Use Condition (Limiting use to nPB formulations containing no 

more than 0.05% by weight isopropyl bromide; AEL of 25 ppm 1 on 8-hr TWA recommended.

Unacceptable. 

Industrial End Use #2: Adhesives ...................... Acceptable, Subject to a Use Condition (Limiting use to nPB formulations containing no 

more than 0.05% by weight isopropyl bromide; AEL of 25 ppm 1 on 8-hr TWA recommended.

Unacceptable. 

Industrial End Use #3: Coatings ........................ Not addressed .................................................. Acceptable, Subject to Use Conditions (Decision limited to coatings at facilities that, as 

of May 30, 2007, have provided EPA information demonstrating their ability to maintain acceptable workplace exposures.2

1Proposed acceptable exposure limit of 25 ppm adjust upward from value of 18 ppm based upon nPB’s effect on sperm motility from evaluation of the WIL 2001 Study ‘‘An Inhalation Two-Generation Reproductive Toxicity Study of 1-Bromopropane in Rats.’’

(a) ICF, 2001. ’’Brief Discussion of the BMD Approach: Overview of its Purpose, Methods, Advantages, and Disadvantages.’’ Prepared for U.S. 

EPA. 

(b) ICF, 2002a. ’’Risk Screen for Use of N Propyl Bromide.’’ Prepared for U.S. EPA, May, 2002. 

(c) ICF, 2002b. Comments on the NTP-Center for the Evaluation of Risks to Human Reproduction, Final Report on 1-Bromopropane. Cover 

Letter Dated 5/9/02. 

Also, evaluation of documents by CERHR (2002a, b), Doull and Rozman (2001), Rodricks (2002), Rozman and Doull (2002), SLR International 

(2001), and others. 2For purposes of this proposal, EPA is considering levels within the range of 17–30 ppm based on the following information on nPB’s health 

effects for purposes of determining acceptability: estrous cycle length at 17 to 22 ppm, live litter size at 20 ppm, and sperm motility at 18 to 30 

ppm from evaluation of the WIL 2001 Study ‘‘An Inhalation Two-Generation Reproductive Toxicity Study of 1-Bromopropane in Rats’’ and confirmed by comparison with other studies. Also, considers evaluation of documents by Stelljes and Wood (2004); TERA (2004); ICF, 2006a; 

ACGIH (2005); Rozman and Doull (2005); Stelljes (2005); and others. 

X. 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 chemicalresistant clothing. Special care should 

be taken to avoid contact with the skin 

since nPB, like many halogenated 

solvents, can be absorbed through the 

skin. Refer to OSHA’s standard for the 

selection and use of Personal Protective 

Equipment, 29 CFR 1910.132. 

• Limit worker exposure to solvents 

to minimize any potential adverse 

health effects. Workers should avoid 

staying for long periods of time in areas 

near where they have been using the 

solvent. Where possible, shorten the 

period during each day when a worker 

is exposed. Where respiratory protection 

is necessary to limit worker exposures, 

respirators must be selected and used in 

accordance with OSHA’s Respiratory 

Protection standard, 29 CFR 1910.134. 

• Use less solvent, or use a different 

solvent, either alone or in a mixture 

with nPB. 

• Follow all recommended safety 

precautions specified in the 

manufacturer’s MSDS. 

• Workers should receive safety 

training and education that includes 

potential health effects of exposure to 

nPB, covering information included on 

the appropriate MSDSs, as required by 

OSHA’s Hazard Communication 

Standard (29 CFR 1910.1200). 

• Request a confidential consultation 

from your State government on all 

aspects of occupational safety and 

health. You can contact the appropriate 

state agency that participates in OSHA’s 

consultation program. These contacts 

are on OSHA’s web site at http:// 

www.osha.gov/oshdir/consult.html. For 

further information on OSHA’s 

confidential consultancy program, visit 

OSHA’s web page at http:// 

www.osha.gov/html/consultation.html. 

• Use the employee exposure 

monitoring programs and product 

stewardship programs where offered by 

manufacturers and formulators of nPBbased products. 

• If the manufacturer or formulator of 

your nPB-based product does not have 

an exposure monitoring program, we 

recommend that you start your own 

exposure monitoring program, and/or 

request a confidential consultation from 

your State government. A medical 

monitoring program should be 

established for the early detection and 

prevention of acute and chronic effects 

of exposure to nPB. The workers’

physician(s) should be given 

information about the adverse health 

effects of exposure to nPB and the 

workers’ potential for exposure. 

Spray applications 

• For spray applications (e.g., 

aerosols), consider your available 

options, and if using nPB, use sufficient 

ventilation to reduce exposure to 

maintain acceptable exposure levels. 

• For ventilation, we recommend that 

you follow the design guidelines for 

ventilation in ACGIH’s Industrial 

Ventilation: A Manual of Recommended 

Practice (ACGIH, 2002). In particular, 

the guidelines in Chapter 10.75 are 

appropriate for spray booths, and the 


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guidelines in Chapter 10.35 are 

appropriate for laboratory hoods. 

• The ACGIH Ventilation Manual 

recommends a minimum flow rate of 

150 cubic feet per minute (cfm) for each 

sq-ft of opening for a small booth with 

at least 4 sq-ft of open face area. This 

equates to an average face velocity of 

150 ft/min. For a large booth, the 

recommended face velocity is 100 ft/ 

min for walk-in booths and 100 to 150 

ft/min for a large spray booth where the 

operator works outside. In general, the 

opening should be kept as small as 

possible to accommodate the workpieces, generally 12 inches wider and 

taller than the largest piece of work. If 

all spraying is not directed towards the 

back of the booth or the booth is too 

shallow for the size of the pieces being 

sprayed or if disruptive air currents are 

present at the face of the booth, a greater 

flow of air will be needed. 

We note that these steps are useful for 

reducing exposure to any industrial 

solvent, and not just nPB. 

XI. Statutory and Executive Order 

Reviews 

A. Executive Order 12866: Regulatory 

Planning and Review 

Under Executive Order (EO) 12866 

(58 FR 51735, October 4, 1993), this 

action is a ‘‘significant regulatory 

action.’’ It raises novel legal or policy 

issues arising out of legal mandates, the 

President’s priorities, or the principles 

set forth in the Executive Order. 

Accordingly, EPA submitted this action 

to the Office of Management and Budget 

(OMB) for review under EO 12866 and 

any changes made in response to OMB 

recommendations have been 

documented in the docket for this 

action. 

In addition, EPA prepared an analysis 

of the potential costs and benefits 

associated with this action. This 

analysis is contained in the document 

‘‘Analysis of Economic Impacts of 

Proposed nPB Rule on Aerosols and 

Adhesives.’’ A copy of the analysis is 

available in the docket for this action 

(Ref. EPA–HQ–OAR–2002–0064) and 

the analysis is briefly summarized here. 

EPA estimates the total costs of the 

proposed rule to between $38.6 and 46.4 

million per year. 

B. Paperwork Reduction Act 

The information collection 

requirements in this proposed rule have 

been submitted for approval to the 

Office of Management and Budget 

(OMB) under the Paperwork Reduction 

Act, 44 U.S.C. 3501 et seq. The 

Information Collection Request (ICR) 

document prepared by EPA has been 

assigned EPA ICR number 2224.01. 

If the provisions of this proposed rule 

become final (i.e., if the proposed 

regulatory language at the end of this 

document is finalized), there would be 

no new information collection burden. 

This proposed rule contains no new 

requirements for reporting or 

recordkeeping. OMB has previously 

approved the information collection 

requirements contained in the existing 

regulations in subpart G of 40 CFR part 

82 under the provisions of the 

Paperwork Reduction Act, 44 U.S.C. 

3501 et seq. and has assigned OMB 

control number 2060–0226 (EPA ICR 

No. 1596.06). This ICR included five 

types of respondent reporting and 

record-keeping activities pursuant to 

SNAP regulations: Submission of a 

SNAP petition, filing a SNAP/Toxic 

Substance Control Act (TSCA) 

Addendum, notification for test 

marketing activity, record-keeping for 

substitutes acceptable subject to use 

restrictions, and record-keeping for 

small volume uses. 

However, if EPA were to finalize the 

proposed alternate approach described 

in section VII.A of this preamble, users 

of nPB would have an information 

collection burden from exposure 

monitoring and recordkeeping. Under 

the proposed alternate approach, users 

of nPB would be required to monitor 

worker exposure initially and 

periodically (usually every 6 months) 

and keep records of these exposure data 

at the facility for at least three years 

from the date the samples were taken. 

This data is necessary to ensure that 

users of nPB are meeting the regulatory 

use conditions. If the data indicates that 

the use condition is not being met, it 

could be used by EPA or citizens in an 

enforcement action against the facility. 

These data would be considered 

available to the public and would not be 

considered confidential. 

The estimated burden of 

recordkeeping for the entire regulated 

community under the proposed 

alternate approach is as much as $7.0 

million and 13,170 hours per year. The 

estimated recordkeeping burden for a 

typical user is $96 and 0.18 hours per 

worker per monitoring event. We 

estimate approximately 1.9 monitoring 

events per year per worker, assuming 

that roughly 90% of exposed workers 

must be monitored every six months 

and 10% must be monitored once 

annually. We estimate that up to 35,000 

workers would be monitored for 

exposure to nPB. Costs under the 

proposed alternate approach include the 

annual cost of purchasing passive 

organic exposure monitoring badges, the 

annual cost of services for analyzing the 

resulting exposure, and the annual cost 

of reviewing and filing the data up to 2 

times per year. 

Burden means the total time, effort, or 

financial resources expended by persons 

to generate, maintain, retain, or disclose 

or provide information to or for a 

Federal agency. This includes the time 

needed to review instructions; develop, 

acquire, install, and utilize technology 

and systems for the purposes of 

collecting, validating, and verifying 

information, processing and 

maintaining information, and disclosing 

and providing information; adjust the 

existing ways to comply with any 

previously applicable instructions and 

requirements; train personnel to be able 

to respond to a collection of 

information; search data sources; 

complete and review the collection of 

information; and transmit or otherwise 

disclose the information. 

An Agency may not conduct or 

sponsor, and a person is not required to 

respond to, a collection of information 

unless it displays a currently valid OMB 

control number. The OMB control 

numbers for EPA’s regulations are listed 

in 40 CFR part 9 and 48 CFR chapter 15. 

To comment on the Agency’s need for 

this information, the accuracy of the 

provided burden estimates, and any 

suggested methods for minimizing 

respondent burden, including through 

the use of automated collection 

techniques, EPA has established a 

public docket for this rule, which 

includes this ICR, under Docket ID 

number EPA–HQ–OAR–2002–0064. 

Submit any comments related to the ICR 

for this proposed rule to EPA and OMB. 

See ADDRESSES section at the beginning 

of this notice for where to submit 

comments to EPA. Send comments to 

OMB at the Office of Information and 

Regulatory Affairs, Office of 

Management and Budget, 725 17th St., 

NW., Washington, DC 20503, marked 

‘‘Attention: Desk Officer for EPA.’’

Include the ICR number in any 

correspondence. Since OMB is required 

to make a decision concerning the ICR 

between 30 and 60 days after May 30, 

2007, a comment to OMB is best assured 

of having its full effect if OMB receives 

it by June 29, 2007. The final rule will 

respond to any OMB or public 

comments on the information collection 

requirements contained in this proposal. 

C. Regulatory Flexibility Act 

The Regulatory Flexibility Act (RFA) 

generally requires an agency to prepare 

a regulatory flexibility analysis of any 

rule subject to notice and comment 

rulemaking requirements under the 

Administrative Procedure Act or any 


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other statute unless the agency certifies 

that the rule will not have a significant 

economic impact on a substantial 

number of small entities. Small entities 

include small businesses, small 

organizations, and small governmental 

jurisdictions. The RFA provides default 

definitions for each type of small entity. 

Small entities are defined as: (1) A small 

business as defined by the Small 

Business Administration’s (SBA) 

regulations at 13 CFR 121.201; (2) a 

small governmental jurisdiction that is a 

government of a city, county, town, 

school district or special district with a 

population of less than 50,000; and (3) 

a small organization that is any not-forprofit enterprise which is independently 

owned and operated and is not 

dominant in its field. However, the RFA 

also authorizes an agency to use 

alternate definitions for each category of 

small entity, ‘‘which are appropriate to 

the activities of the agency’’ after 

proposing the alternate definition(s) in 

the Federal Register and taking 

comment. 5 U.S.C. 601(3)–(5). In 

addition, to establish an alternate small 

business definition, agencies must 

consult with SBA’s Office of Advocacy. 

EPA proposed an alternate definition 

for regulatory flexibility analyses under 

the RFA for rules related to the use of 

nPB as an alternative to ozone-depleting 

substances (ODS) in metals, precision, 

and electronics cleaning, adhesives, and 

aerosol solvents in the June 2003 NPRM 

(68 FR 33309, June 3, 2003). EPA 

established this final definition under 

section 601(3) of the RFA when we 

promulgated the final rule on the 

acceptable use of nPB in metals, 

precision, and electronics cleaning in 

the Rules and Regulations section of 

today’s Federal Register. For purposes 

of assessing the economic impacts of 

this proposed rule on small entities, 

EPA defined ‘‘small business’’ as a small 

business with less than 500 employees, 

rather than use the individual SBA size 

standards for the numerous NAICS 

subsectors and codes. We believe that 

no small governments or small 

organizations are affected by this rule. 

EPA chose to use the alternate 

definition to simplify the economic 

analysis. This approach slightly reduced 

the number of small businesses 

included in our analysis and slightly 

increased the percentage of small 

businesses for whom the analysis 

indicated the use of nPB in accordance 

with this proposed rule may have an 

economically significant impact. 

Furthermore, this size standard was set 

by the Small Business Administration 

for all NAICS codes for businesses using 

nPB-based adhesives, one of the end 

uses that would be affected by this rule. 

After considering the economic 

impacts of this proposed rule on small 

entities, I certify that this action will not 

have a significant economic impact on 

a substantial number of small entities. 

This rule proposes to list nPB as an 

unacceptable substitute for ODS in 

aerosols and adhesives. EPA has 

analyzed the economic impacts of 

switching from nPB to other alternative 

aerosol solvents or adhesives. EPA 

estimates that up to 3,380 small 

industrial end users currently use nPB 

in the end uses addressed by this 

proposed rule and thus could be subject 

to the regulatory impacts of this rule. 

This number includes approximately 

3,100 users of nPB-based aerosol 

solvents, and 280 users of nPB-based 

adhesives. Considering the regulatory 

impacts on adhesive and aerosol users 

that must switch to other alternatives, 

we found that up to 258 (8%) of small 

businesses would experience impacts of 

1% or greater of annual sales and no 

small businesses would experience 

impacts of 3% or greater of annual sales. 

Based on the relatively small number 

and low percentage of small businesses 

that would experience significant 

economic impacts, EPA concludes that 

this rule would not have a significant 

economic impact on a substantial 

number of small entities. 

In the case of coatings uses, our 

understanding is that only a single 

facility, the Lake City Army 

Ammunition Plant, is currently using 

coatings with nPB as the carrier solvent, 

and this facility could continue to use 

nPB following its current practices. 

Therefore, we consider there to be no 

economic impact of this rule on coatings 

users and have not done further analysis 

for this end use. 

Types of businesses that would be 

subject to this proposed rule include: 

• Manufacturers of computers and 

electronic equipment that clean with 

nPB cleaning solvents (NAICS subsector 

334). 

• Manufacturers of appliances, 

electrical equipment, and components 

that require oil, grease, and solder flux 

to be cleaned off (NAICS subsection 

335). 

• Manufacturers of transportation 

equipment, such as aerospace 

equipment that requires cleaning either 

in a tank or with aerosols, or aircraft 

seating, which is assembled using 

adhesives containing nPB as a carrier 

solvent; and ship or boat builders 

applying adhesives with nPB (NAICS 

subsector 336). 

• Manufacturers of furniture, 

including various kinds of furniture 

with cushions and countertops 

assembled using adhesives containing 

nPB as a carrier solvent (NAICS 

subsector 337). 

• Foam fabricators, who assemble 

foam cushions or sponges using 

adhesives containing nPB as a carrier 

solvent (NAICS code 326150). 

In order to consider the resources that 

affected small businesses have available 

to operate and to respond to the 

proposed regulatory requirements, EPA 

compared the cost of meeting the 

proposed regulatory requirements to 

small businesses’ annual sales. In our 

analysis for this proposed rule, we used 

the average value of shipments for the 

products manufactured by the end user 

as a proxy for sales or revenues, since 

these data are readily available from the 

U.S. Department of Commerce. The 

following tables display the average 

value of shipments for different sizes of 

business and different NAICS subsectors 

or codes in the affected industrial 

sectors. EPA then used data from these 

sources to determine the potential 

economic impacts of this proposed rule 

on small businesses. 

TABLE 15.—AVERAGE VALUE OF SHIPMENTS IN NAICS SUBSECTORS USING AEROSOL SOLVENTS, BY NUMBER OF

EMPLOYEES AT BUSINESS

Number of employees at business 

Average value of shipments per business ($) by NAICS 

subsector code 

334, computer 

and electronic 

products 

335, electrical 

equipment, 

appliance, and 

component mfg 

336, transportation equipment 

1 to 4 employees ............................................................................................................. 345,007 315,772 412,460 

5 to 9 employees ............................................................................................................. 1,317,238 1,243,065 1,414,384 

10 to 19 employees ......................................................................................................... 2,566,913 2,483,327 2,573,352 


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TABLE 15.—AVERAGE VALUE OF SHIPMENTS IN NAICS SUBSECTORS USING AEROSOL SOLVENTS, BY NUMBER OF

EMPLOYEES AT BUSINESS—Continued 

Number of employees at business 

Average value of shipments per business ($) by NAICS 

subsector code 

334, computer 

and electronic 

products 

335, electrical 

equipment, 

appliance, and 

component mfg 

336, transportation equipment 

20 to 49 employees ......................................................................................................... 5,672,245 5,389,945 5,738,739 

50 to 99 employees ......................................................................................................... 12,951,836 12,650,236 12,735,583 

100 to 249 employees ..................................................................................................... 31,258,875 31,290,638 34,256,544 

250 to 499 employees ..................................................................................................... 84,270,454 77,279,974 86,911,454 

Avg. value ship small businesses in sub-sector ............................................................. 8,261,788 9,539,205 11,029,561 

Avg. value ship all businesses in subsector ................................................................... 20,810,094 13,417,905 45,029,773 

Avg. value shipments subset small businesses using nPB ............................................ 11,246,045 12,066,562 13,422,547 

TABLE 16.—AVERAGE VALUE OF SHIPMENTS IN NAICS CATEGORIESUSING NPB AS A CARRIER SOLVENT IN ADHESIVES, 

BY NUMBER OF EMPLOYEES AT BUSINESS

Number of employees at business 

Average value of shipments per small business ($) by NAICS sub sector 

337121, 

upholstered 

household furniture 

337110, wood 

kitchen cabinet 

and counter tops 

326150, 

urethane and 

other foam products (except polystyrene) 

336360, motor 

vehicle seating 

and interior trim 

337124, metal 

household 

furniture 

1 to 4 employees ............................................. 234,345 156,833 496,318 425,863 187,950 

5 to 9 employees ............................................. 963,021 622,744 1,305,183 1,728,132 903,393 

10 to 19 employees ......................................... 1,771,416 1,141,119 3,152,283 3,082,486 1,431,480 

20 to 49 employees ......................................... 3,653,623 2,619,197 6,615,331 5,508,370 3,538,684 

50 to 99 employees ......................................... 8,089,968 7,386,365 13,281,000 14,088,500 7,547,536 

100 to 249 employees ..................................... 17,502,175 17,151,091 31,524,872 44,310,286 19,821,719 

250 to 499 employees ..................................... 40,250,813 55,982,674 64,119,800 123,803,610 d(1) 

Avg. Small Businesses in Sub sector .............. 3,588,297 1,150,768 10,472,992 12,542,725 3,141,720 

Avg. ALL Businesses in Sub sector ................ 5,490,101 1,475,602 11,110,822 44,808,573 5,239,747 

Avg. Subset Small Businesses using nPB ...... 11,519,540 5,999,622 18,950,068 12,019,847 20,401,301 

(1) ‘‘d’’ designates ‘‘Data withheld to avoid disclosing data of individual companies; data are included in higher level totals.’’ The average value 

of shipments for businesses estimates those values marked with ‘‘d,’’ and thus may be overestimated or underestimated. 

This proposed rule would list nPB as 

unacceptable for use in adhesives and 

aerosols. The available alternatives 

identified include adhesive 

formulations based on water, methylene 

chloride, or flammable solvents such as 

acetone and aerosol formulations of 

flammable solvents, combustible 

solvents, blends of transdichloroethylene and HFEs or HFCs, 

and HCFC–225ca/cb. We considered 

various aspects of the cost of switching 

to other alternatives, including the cost 

of meeting OSHA requirements and the 

cost of the alternative adhesive. We 

specifically request public comment on 

the assumptions and costs used in 

EPA’s analysis (US EPA, 2007). 

We estimate that up to 9 small 

businesses using nPB-based adhesives, 

or roughly 3% of the 280 or so small 

businesses that use nPB-based 

adhesives, would experience a cost 

increase (i.e., an impact) of greater than 

1.0% of annual sales, and no small 

businesses would experience an impact 

of greater than 3% of annual sales if this 

proposed rule became final. For small 

businesses using nPB-based aerosols, we 

estimate that approximately 249 would 

experience a cost increase of greater 

than 1.0% of annual sales. This equates 

to roughly 8% of the 3100 or so small 

businesses currently using nPB-based 

aerosol solvents. No small businesses 

using aerosols would experience an 

impact of greater than 3% of annual 

sales. Approximately eight percent of all 

3380 or so small businesses choosing to 

use nPB in these end uses would 

experience an impact of greater than 

1.0% of annual sales and no small 

businesses would experience an impact 

of greater than 3.0% of annual sales. 

Because of the small total number and 

small percentage of affected businesses 

that would experience an impact of 

greater than either 1.0% or 3.0% of 

annual sales, EPA does not consider this 

proposed rule to have a significant 

economic impact on a substantial 

number of small businesses. 

We also analyzed the potential small 

business impacts of the proposed 

alternate approach. Under the proposed 

alternate approach, users would have to: 

(1) Meet an exposure level of 20 ppm on 

an eight-hour time-weighted average, (2) 

monitor workers’ exposure to nPB using 

a personal breathing zone sampler on an 

eight-hour time-weighted average 

initially and periodically (every 6 

months or longer, depending on the 

concentration during initial 

monitoring), and (3) keep records of the 

worker exposure data on site at the 

facility for at least three years from the 

date of the measurement. We assume 

that the cost of following the proposed 

alternate approach is the cost of 

installing ventilation for aerosols and 

adhesives or emission controls for 

solvent cleaning, the cost of using 

personal protective equipment, and the 

cost of monitoring worker exposure. 

Approximately 67 to 387 aerosol solvent 

users (2 to 13 percent), 25 to 54 

adhesive users (9 to 19 percent), and 2.6 

to 12.6 percent of all 3380 or so small 

businesses would experience impacts of 

greater than 1% of annual sales if they 

chose to use nPB subject to the 

proposed use conditions rather than 

switching to another ODS substitute. 


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Four to nine users of nPB-based 

adhesives, or less than 1% of all small 

businesses affected by this proposal, 

would experience impacts of 3% or 

greater of annual sales under the 

proposed alternate approach. Based on 

this analysis, the proposed alternate 

approach would not create a significant 

adverse economic impact on a 

substantial number of small entities. 

Although this proposed rule would 

not have a significant economic impact 

on a substantial number of small entities 

if it became final, EPA nonetheless has 

tried to reduce the impact of this rule on 

small entities. Before selecting preferred 

the regulatory option in this proposed 

rule, we considered a number of 

regulatory options, such as: 

• Placing a narrowed use limit on the 

use of nPB in adhesives and aerosols 

that would allow its use only in those 

cases where alternatives are technically 

infeasible due to performance or safety 

issues. This would have required 

testing, recordkeeping, and some 

installation of capital equipment. 

• Requiring that when nPB is used in 

adhesives or aerosols, it must be used 

with local ventilation equipment and 

personal protective equipment. This 

would have required further installation 

of capital equipment, without 

necessarily protecting workers as 

thoroughly as a required acceptable 

exposure limit or requiring a switch to 

another alternative. 

• Prohibiting the use of nPB in all 

end uses. 

• Retaining the previously proposed 

requirement for a limit on iPB content 

in nPB formulations. 

The costs of a number of these options 

are included in EPA’s analysis (US EPA, 

2006; U.S. EPA, 2007). 

In developing our regulatory options, 

we considered information we learned 

from contacting small businesses using 

or selling nPB. EPA staff visited the site 

of a small business using nPB for 

cleaning electronics. We contacted 

several fabricators of foam cushions that 

have used adhesives containing nPB. 

We participated in meetings with a 

number of adhesive manufacturers and 

users of adhesives in furniture 

construction. We developed a fact sheet 

and updated our program Web site to 

inform small businesses about the 

proposed rule and to request their 

comments. 

We continue to be interested in the 

potential impacts of the proposed rule 

on small entities and welcome 

comments on issues related to such 

impacts. 

D. Unfunded Mandates Reform Act 

Title II of the Unfunded Mandates 

Reform Act of 1995 (UMRA), Public 

Law 104–4, establishes requirements for 

Federal agencies to assess the effects of 

their regulatory actions on State, local, 

and tribal governments and the private 

sector. Under section 202 of the UMRA, 

EPA generally must prepare a written 

statement, including a cost-benefit 

analysis, for proposed and final rules 

with ‘‘Federal mandates’’ that may 

result in expenditures to State, local, 

and tribal governments, in the aggregate, 

or to the private sector, of $100 million 

or more in any one year. Before 

promulgating an EPA rule for which a 

written statement is needed, section 205 

of the UMRA generally requires EPA to 

identify and consider a reasonable 

number of regulatory alternatives and 

adopt the least costly, most costeffective or least burdensome alternative 

that achieves the objectives of the rule. 

The provisions of section 205 do not 

apply when they are inconsistent with 

applicable law. Moreover, section 205 

allows EPA to adopt an alternative other 

than the least costly, most cost-effective 

or least burdensome alternative if the 

Administrator publishes with the final 

rule an explanation why that alternative 

was not adopted. Before EPA establishes 

any regulatory requirements that may 

significantly or uniquely affect small 

governments, including tribal 

governments, it must have developed 

under section 203 of the UMRA a small 

government agency plan. The plan must 

provide for notifying potentially 

affected small governments, enabling 

officials of affected small governments 

to have meaningful and timely input in 

the development of EPA regulatory 

proposals with significant Federal 

intergovernmental mandates, and 

informing, educating, and advising 

small governments on compliance with 

the regulatory requirements. EPA has 

determined that this rule does not 

contain a Federal mandate that may 

result in expenditures of $100 million or 

more for State, local, and tribal 

governments, in the aggregate, or the 

private sector in any one year. This 

proposed rule does not affect State, 

local, or tribal governments. The 

enforceable requirements of the rule for 

the private sector affect a number of end 

users in manufacturing. The estimated 

cost of the proposed requirements for 

the private sector is approximately 

$38.6 to 46.4 million per year, and the 

proposed alternate approach would cost 

the private sector approximately $ 42.3 

to 67.5 million per year. Therefore, the 

impact of this rule on the private sector 

is less than $100 million per year. Thus, 

this rule is not subject to the 

requirements of sections 202 and 205 of 

the UMRA. EPA has determined that 

this rule contains no regulatory 

requirements that might significantly or 

uniquely affect small governments. This 

regulation applies directly to facilities 

that use these substances and not to 

governmental entities. 

E. Executive Order 13132: Federalism 

Executive Order 13132, entitled 

‘‘Federalism’’ (64 FR 43255, August 10, 

1999), requires EPA to develop an 

accountable process to ensure 

‘‘meaningful and timely input by State 

and local officials in the development of 

regulatory policies that have federalism 

implications.’’ ‘‘Policies that have 

federalism implications’’ is defined in 

the Executive Order to include 

regulations that have ‘‘substantial direct 

effects on the States, on the relationship 

between the National government and 

the States, or on the distribution of 

power and responsibilities among the 

various levels of government.’’

This proposed rule does not have 

federalism implications. It will not have 

substantial direct effects on the States, 

on the relationship between the national 

government and the States, or on the 

distribution of power and 

responsibilities among the various 

levels of government, as specified in 

Executive Order 13132. This regulation 

applies directly to facilities that use 

these substances and not to 

governmental entities. Thus, Executive 

Order 13132 does not apply to this rule. 

F. Executive Order 13175: Consultation 

and Coordination With Indian Tribal 

Governments 

Executive Order 13175, entitled 

‘‘Consultation and Coordination with 

Indian Tribal Governments’’ (65 FR 

67249, November 6, 2000), requires EPA 

to develop an accountable process to 

ensure ‘‘meaningful and timely input by 

tribal officials in the development of 

regulatory policies that have tribal 

implications.’’ ‘‘Policies that have tribal 

implications’’ is defined in the 

Executive Order to include regulations 

that have ‘‘substantial direct effects on 

one or more Indian tribes, on the 

relationship between the Federal 

government and the Indian tribes, or on 

the distribution of power and 

responsibilities between the Federal 

government and Indian tribes.’’

This proposed rule does not have 

tribal implications. It will not have 

substantial direct effects on tribal 

governments, on the relationship 

between the Federal government and 

Indian tribes, or on the distribution of 

power and responsibilities between the 


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30202 Federal Register / Vol. 72, No. 103 / Wednesday, May 30, 2007 / Proposed Rules 

Federal government and Indian tribes, 

as specified in Executive Order 13175. 

This proposed rule would not 

significantly or uniquely affect the 

communities of Indian tribal 

governments, because this regulation 

applies directly to facilities that use 

these substances and not to 

governmental entities. Thus, Executive 

Order 13175 does not apply to this 

proposed rule. 

G. Executive Order 13045: Protection of 

Children From Environmental Health 

and Safety Risks 

Executive Order 13045: ‘‘Protection of 

Children from Environmental Health 

Risks and Safety Risks’’ (62 FR 19885, 

April 23, 1997) applies to any rule that: 

(1) Is determined to be ‘‘economically 

significant’’ as defined under Executive 

Order 12866, and (2) concerns an 

environmental health or safety risk that 

EPA has reason to believe may have a 

disproportionate effect on children. If 

the regulatory action meets both criteria, 

the Agency must evaluate the 

environmental health or safety effects of 

the planned rule on children, and 

explain why the planned regulation is 

preferable to other potentially effective 

and reasonably feasible alternatives 

considered by the Agency. 

This proposed rule is not subject to 

the Executive Order because it is not 

economically significant as defined in 

Executive Order 12866, and because the 

Agency does not have reason to believe 

the environmental health or safety risks 

addressed by this action present a 

disproportionate risk to children. The 

exposure limits and acceptability 

listings in this proposed rule apply to 

the workplace. These are areas where 

we expect adults are more likely to be 

present than children, and thus, the 

agents do not put children at risk 

disproportionately. 

The public is invited to submit or 

identify peer-reviewed studies and data, 

of which the agency may not be aware, 

that assessed results of early life 

exposure to nPB. 

H. Executive Order 13211: Actions That 

Significantly Affect Energy Supply, 

Distribution, or Use 

This rule is not a ‘‘significant energy 

action’’ as defined in Executive Order 

13211, ‘‘Actions Concerning Regulations 

That Significantly Affect Energy Supply, 

Distribution, or Use’’ (66 FR 28355 (May 

22, 2001)) because it is not likely to 

have a significant adverse effect on the 

supply, distribution, or use of energy. 

This action would impact 

manufacturing of various metal, 

electronic, medical, and optical 

products cleaned with solvents 

containing nPB and products made with 

adhesives containing nPB. Further, we 

have concluded that this rule is not 

likely to have any adverse energy 

effects. 

I. National Technology Transfer and 

Advancement Act 

As noted in the proposed rule, 

Section 12(d) of the National 

Technology Transfer and Advancement 

Act of 1995 (‘‘NTTAA’’), Public Law 

104–113, section 12(d) (15 U.S.C. 272 

note) directs EPA to use voluntary 

consensus standards in its regulatory 

activities unless to do so would be 

inconsistent with applicable law or 

otherwise impractical. Voluntary 

consensus standards are technical 

standards (e.g., materials specifications, 

test methods, sampling procedures, and 

business practices) that are developed or 

adopted by voluntary consensus 

standards bodies. The NTTAA directs 

EPA to provide Congress, through OMB, 

explanations when the Agency decides 

not to use available and applicable 

voluntary consensus standards. 

This action does not involved 

technical standards. Therefore, EPA did 

not consider the use of any voluntary 

consensus standards. We note that the 

American Conference of Governmental 

Industrial Hygienists (ACGIH), although 

it sets voluntary standards, is not a 

voluntary consensus standards body. 

Therefore, use of an acceptable exposure 

limit from the ACGIH is not subject to 

the NTTAA. 

XII. References 

The documents below are referenced 

in the preamble. All documents are 

located in the Air Docket at the address 

listed in section I.B.1 at the beginning 

of this document. Unless specified 

otherwise, all documents are available 

electronically through the Federal 

Docket Management System, Docket # 

EPA–HQ–OAR–2002–0064. Some 

specific items are available only in hard 

copy in dockets A–2001–07 or A–92–42 

(legacy docket numbers for SNAP nPB 

rule and for SNAP program and 

submissions). Numbers listed after the 

reference indicate the docket and item 

numbers. 

Availability 

Harper, 2005. Telephone call from M. 

Sheppard, EPA to Dr. S. Harper, ATK. 

Re: Availability of other methyl 

chloroform substitutes for the Lake City 

Army Ammunition Plant. October 11, 

2005. (EPA–HQ–OAR–2002–0064–0150) 

IRTA, 2000. Alternative Adhesive 

Technologies in the Foam Furniture and 

Bedding Industries: A Cleaner 

Technologies Substitution Assessment, 

Cost and Performance Evaluation. 

Michael Morris and Katy Wolf, Institute 

for Research and Technical Assistance. 

Prepared for the U.S. EPA Office of 

Pollution Prevention Technology, June 

2000. (A–2001–07, II–D–70) 

Seilheimer, 2001. Telephone Log of April 4, 

2001 call between Margaret Sheppard, 

EPA, and Bob Seilheimer, Imperial 

Adhesives. (A–2001–07, II–B–5) 

Williams, 2005. Notes on conversation of Ed 

Williams, Technical Manager, LPS 

Laboratories, and Margaret Sheppard, 

EPA. November 3, 2005 (EPA–HQ–OAR–

2002–0064–0198) 

Impacts on the Atmosphere, Local Air 

Quality, and Other Environmental 

Impacts 

Atmospheric and Environmental Research, 

Inc., 1995. Estimates of the Atmospheric 

Lifetime, Global Warming Potential and 

Ozone Depletion Potential of n-Propyl 

Bromide. Independent study prepared 

for Albemarle Corporation. (A–2001–07, 

II–D–17) 

ATSDR, 1994. Toxicological Profile For 

Acetone. Agency for Toxic Substances 

and Disease Registry. May, 1994. 

Available at http://www.atsdr.cdc.gov/ 

toxprofiles/tp21-c5.pdf (EPA–HQ–OAR–

2002–0064–0118) 

ATSDR, 1996. Toxicological Profile For 1,2- 

Dichloroethene. Agency for Toxic 

Substances and Disease Registry. August, 

1996. Available at http:// 

www.atsdr.cdc.gov/toxprofiles/tp87- 

c5.pdf (EPA–HQ–OAR–2002–0064–

0113) 

ATSDR, 1997. Toxicological Profile For 

Trichloroethylene. Agency for Toxic 

Substances and Disease Registry. 

September, 1997. Available athttp:// 

www.atsdr.cdc.gov/toxprofiles/tp19- 

c5.pdf (EPA–HQ–OAR–2002–0064–

0123) 

ATSDR, 2004. Draft Toxicological Profile For 

1,1,1-Trichloroethane. Agency for Toxic 

Substances and Disease Registry. 

September, 2004. Updated draft for 

comment. Available at http:// 

www.atsdr.cdc.gov/toxprofiles/tp70- 

c6.pdf (EPA–HQ–OAR–2002–0064–

0132) 

EDSTAC, 1998. Final Report of the Endocrine 

Disruptor Screening and Testing 

Advisory Committee. August, 1998. 

(EPA–HQ–OAR–2002–0064–0136) 

Fisher Scientific, 2001. Material Safety Data 

Sheet for acetone. Updated March 19, 

2001. Available at http:// 

www.mhatt.aps.anl.gov/dohn/msds/ 

acetone.html (EPA–HQ–OAR–2002–

0064–0129) 

Geiger et al., 1998. Geiger, D.L., Call, D.J., 

and Brooke, L.T. 1988. Acute Toxicities 

of Organic Chemicals to Fathead 

Minnows (Pimephales promelas), Vol. 4. 

In: Center for Lake Superior 

Environmental Stud., Univ. of 

Wisconsin-Superior, Superior, WI I:355. 

(Summarized in ICF, 2004a) 

HSDB, 2004. Hazardous Substances Databank 

File for 1-Bromopropane. Accessed 1/ 

2004 from the World Wide Web at 

http://toxnet.nlm.nih.gov/cgi-bin/sis/ 


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search/f?./temp/dLwM9e:1 (Summarized 

in ICF, 2004a) 

ICF, 2003a. ICF Consulting. Revised 

Evaluation of the Global Warming 

Potential for n-Propyl Bromide. (EPA–

HQ–OAR–2002–0064–0164) 

ICF, 2004a. ICF Consulting. Memo to E. 

Birgfeld, EPA, re: nPB Aquatic Toxicity. 

January 19, 2004. (EPA–HQ–OAR–2002–

0064–0177) 

ICF, 2006a. ICF Consulting. Risk Screen on 

Substitutes for Ozone-Depleting 

Substances for Adhesive, Aerosol 

Solvent, and Solvent Cleaning 

Applications. Proposed Substitute: nPropyl Bromide. April 18, 2006. 

Attachments: A, Determination of an 

AEL; B, Derivation of an RfC; C, 

Evaluation of the Global Warming 

Potential; D, Occupational Exposure 

Analysis for Adhesive Applications; E, 

Occupational Exposure Analysis for 

Aerosol Solvent Applications; F, General 

Population Exposure Assessment for nPropyl Bromide 

LaGrega, M., Buckingham, P., Evans, J., and 

Environmental Resources Management, 

2001. Hazardous Waste Management. 

Second Edition. McGraw-Hill, New 

York, NY. 2001. (EPA–HQ–OAR–2002–

0064–0112) 

Linnell, 2003. Comments from the 

Electronics Industry Alliance. (EPA–HQ–

OAR–2002–0064 items –0043, –0044, 

and –0045) 

MOP 18, 2006. Report of the Eighteenth 

Meeting of the Parties to the Montreal 

Protocol on Substances that Deplete the 

Ozone Layer. November 16, 2006. (EPA–

HQ–OAR–2002–0064–0163) 

NPS, 1997. Irwin, R.J., M. VanMouwerik, L. 

Stevens, M.S. Seese, and W. Basham. 

1997. Environmental Contaminants 

Encyclopedia. National Park Service, 

Water Resources Division, Fort Collins, 

Colorado. (EPA–HQ–OAR–2002–0064–

0086) 

Steminiski, 2003. July 27, 2003 Comment 

from J. Steminiski, Ph.D. (EPA–HQ–

OAR–2002–0064–0035 and –0043) 

U.S. Economic Census, 2002a. General 

Summary: 2002. Subject Series. Report 

No. EC02–31SG–1, October, 2005. U.S. 

Census Bureau. (EPA–HQ–OAR–2002–

0064–0133) 

U.S. Economic Census, 2002b. U.S. Economic 

Census for Island Areas, 2002. Report for 

Northern Marianas Islands, Rpt. No. 

IA02–00A–NMI, May, 2004. U.S. Census 

Bureau. (EPA–HQ–OAR–2002–0064–

0091) 

U.S. Economic Census, 2002c. U.S. Economic 

Census for Island Areas, 2002. Report for 

Guam, Rpt. No. IA02–00A–GUAM, 

March, 2005. U.S. Census Bureau. (EPA–

HQ–OAR–2002–0064–0102) 

U.S. Economic Census, 2002d. U.S. 

Economic Census for Island Areas, 2002. 

Report for Virgin Islands, Rpt. No. IA02–

00A–VI , April, 2005. U.S. Census 

Bureau. (EPA–HQ–OAR–2002–0064–

0131) 

U.S. Economic Census, 2002e. U.S. Economic 

Census for Island Areas, 2002. Report for 

American Samoa, Rpt. No. IA02–00A–

AS, April, 2005. U.S. Census Bureau. 

(EPA–HQ–OAR–2002–0064–0103) 

U.S. Economic Census, 2002f. U.S. Economic 

Census for Island Areas, 2002. Report for 

Puerto Rico: Manufacturing, Rpt. No. 

IA02–00I–PRM, October, 2005. U.S. 

Census Bureau. (EPA–HQ–OAR–2002–

0064–0107) 

U.S. EPA, 1980. Ambient Water Quality 

Criteria for Dichloroethylenes. EPA 440/ 

5–80–041 October, 1980. Available at 

http://www.epa.gov/waterscience/pc/ 

ambientwqc/dichloroethylenes80.pdf 

U.S. EPA, 1992. Hazard Assessment 

Guidelines for Listing Chemicals on the 

Toxic Release Inventory, Revised Draft. 

Washington, DC: Office of Pollution, 

Prevention and Toxics. As referenced in 

ICF, 2004f. 

U.S. EPA, 1994a. Chemical Summary for 

Methyl Chloroform, prepared by Office 

of Pollution Prevention and Toxics, 

August, 1994. (EPA–HQ–OAR–2002–

0064–0121) 

WMO, 2002: Scientific Assessment of Ozone 

Depletion: 2002, Global Ozone Research 

and Monitoring Project—Report No. 47, 

Geneva, 2003 Full report available online 

at http://esrl.noaa.gov/csd/assessments/ 

(A–2001–07, II–A–20) 

Wuebbles, Donald J. 2002. ‘‘The Effect of 

Short Atmospheric Lifetimes on 

Stratospheric Ozone.’’ Written for Enviro 

Tech International, Inc. Department of 

Atmospheric Sciences, University of 

Illinois–Urbana. (EPA–HQ–OAR–2002–

0064–0114) 

Flammability and Fire Safety 

BSOC, 2000. February 1, 2000 Tabulation of 

Flammability Studies on n-Propyl 

Bromide from the Brominated Solvents 

Committee, and other information on 

flammability of n-propyl bromide. (A–

2001–07, II–D–45) 

Miller, 2003. Albemarle Corporation 

comments-Flash Point Data for n-Propyl 

Bromide. (EPA–HQ–OAR–2002–0064–

0040) 

Morford, 2003a. Enviro Tech International 

Comment re Section IV D Flammability 

with Exhibits (7/25/03) (EPA–HQ–OAR–

2002–0064–0030) 

Morford, 2003b. Enviro Tech International 

Supporting Exhibits on Flammability (7/ 

25/03) (EPA–HQ–OAR–2002–0064–

0031) 

Morford, 2003c. Enviro Tech Int. 

Flammability of nPB & Comparison With 

Methylene Chloride-Additional 

Comments on Flammability (7/29/03) 

(EPA–HQ–OAR–2002–0064–0036) 

Shubkin, 2003. R. Shubkin, Poly Systems, 

EPA received 7/23/03 Re: Comment on 

Flammability of n-Propyl Bromide as 

Discussed in Proposed Rule Published in 

Federal Register (EPA–HQ–OAR–2002–

0064–0025) 

Weiss Cohen, 2003. T. Weiss Cohen, Dead 

Sea Bromine Group, 7/31/2003 Comment 

to Federal Register Proposed Rules of 

June 3, 2003, on Protection of 

Stratospheric Ozone: Listing of 

Substitutes for Ozone-Depleting 

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HQ–OAR–2002–0064–0053) 

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ACGIH, 1991. Skin Notation Documentation 

for Methyl Chloride. Available online at 

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ACGIH, 2005. Documentation for Threshold 

Limit Value for 1-Bromopropane. 2005. 

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Albemarle, 2003. Product Description for 

Abzol Cleaners. 2003. (EPA–HQ–OAR–

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Beck and Caravati, 2003. Neurotoxicity 

associated with 1-bromopropane 

exposure. Utah Poison Control Center, 

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41(5):729. (Abstract from conference). 

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CERHR, 2002a. NTP-Center for the 

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CERHR, 2002b. NTP-Center for the 

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CERHR, 2003a. NTP-CERHR Monograph on 

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CERHR, 2003b. NTP-CERHR Monograph on 

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CERHR, 2004a. NTP-CERHR Expert Panel 

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CERHR, 2004b. NTP-CERHR Expert Panel 

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2004. 

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section on ‘‘Impacts on the atmosphere, 

local air quality, and other 

environmental impacts’’

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OAR–2002–0064–0179) 

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2006. 

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Y., Shibata, E., Kitoh, J., et al. 

Neurotoxicity of 1-Bromopropane. 1998. 

Translated by Albemarle Corporation. 

(A–91–42, X–A–33) 

Ichihara, G., Jong, X., Onizuka, J., et al., 1999. 

Histopathological changes of nervous 

system and reproductive organ and 

blood biochemical findings in rats 

exposed to 1-bromopropane. (Abstract 

only) Abstracts of the 72nd Annual 

Meeting of Japan Society for 

Occupational Health. May 1999. Tokyo. 

(A–2001–07, II–A–15) 

Ichihara G., Kitoh J., Yu, X., et al., 2000a. 1- 

Bromopropane, an alternative to ozone 

layer depleting solvents, is dosedependently neurotoxic to rats in longterm inhalation exposure. Toxicol 

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8) 

Ichihara, G., Yu, X., Kitoh, J., et al. 2000b. 

Reproductive toxicity of 1- 

bromopropane, a newly introduced 

alternative to ozone layer depleting 

solvents, in male rats. Toxicol Sciences 

54:416–423. (A–2001–07, II–A–7) 

Ichihara G. et al., 2002. Neurological 

Disorders in Three Workers Exposed to 

1-Bromopropane. J Occu. Health 44:1–7. 

(A–2001–07, II–D–64) 

Ichihara et al., 2004a. G. Ichihara, W. Li, X. 

Ding, S. Peng, X. Yu, E. Shibata, T. 

Yamada, H. Wang, S. Itohara, S. Kanno, 

K. Sakai, H. Ito, K. Kanefusa, and Y. 

Takeuchi. A Survey on Exposure Level, 

Health Status, and Biomarkers in 

Workers Exposed to 1-Bromopropane. 

Am Jrnl of Ind Med 45:63–75 (2004) 

(EPA–HQ–OAR–2002–0064–0093) 

Ichihara et al., 2004b. Gaku Ichihara, Weihua 

Li, Eiji Shibata, Xuncheng Ding, Hailan 

Wang, Yideng Liang, Simeng Peng, 

Seiichiro Itohara, Michihiro Kamijima, 

Qiyuan Fan, Yunhui Zhang, Enhong 

Zhong, Xiaoyun Wu, William M. 

Valentine, and Yasuhiro Takeuchi. 

Neurological Abnormalities in Workers 

of 1-Bromopropane Factory. Env’l Health 

Perspectives, 30 June 2004. (EPA–HQ–

OAR–2002–0064–0139) 

Ishidao et al., 2002. Ishidao, T., Kunugita, N., 

Fueta, Y., Arashidani, K., Hori, H. Effects 

of inhaled 1-bromopropane vapor on rat 

metabolism. Toxicol Lett. 2002 Aug 5; 

134(1–3):237–43 (EPA–HQ–OAR–2002–

0064–0125) 

Lake City Army Ammunition Plant, 2003. 

SNAP application for n-Propyl Bromide 

in coatings, T.J. Herman, ATK Alliant 

Lake City Small Caliber Ammunition 

Company, dated 7/8/2003. EPA Received 

7/14/2003. (EPA–HQ–OAR–2002–0064–

0029) 

Lake City Army Ammunition Plant, 2004. 

March 9, 2004 Industrial Hygiene Air 

Sampling Report for Normal Propyl 

Bromide Based Mouth Waterproofing in 

Manufacture of 5.56 mm Ammunition. 

S.A. Hawk. (EPA–HQ–OAR–2002–0064–

0211) 

Majersik et al., 2004. Chronic Exposure to 1- 

Bromopropane Associated with Spastic 

Paraparesis and Distal Neuropathy: A 

Report of Six Foam Cushion Gluers. 

Poster paper from 129th Annual Meeting 

of the American Neurological 

Association, Toronto. October, 2004. 

(EPA–HQ–OAR–2002–0064–0219) 

Majersik et al, 2005. ‘‘Spastic Paraparesis and 

Distal Neuropathy Associated with 

Chronic Exposure to 1BP,’’ Presentation 

by Drs. J. Majersik, M. Caravati, and J. 

Steffens at the North American Congress 

of Clinical Toxicologists. September 14, 

2005. (EPA–HQ–OAR–2002–0064–0116) 

Miller, 2005. ‘‘1-Bromopropane: A Private 

Neurological Practice Experience in 

2000,’’ Presentation by Dr. J.M. Miller, at 

the North American Congress of Clinical 

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(EPA–HQ–OAR–2002–0064–0216) 

Morford, 2003d. White Paper: ‘‘EPA Is 

Unlawfully Regulating Occupational 

Exposures’’ Attachment to public 

comments. (EPA–HQ–OAR–2003–0064–

0049) 

Morford, 2003e. Comment regarding 

proposed restriction on isopropyl 

bromide Richard Morford, Enviro Tech 

International. August 3, 2003. (EPA–HQ–

OAR–2002–0064–0042) 

Morford, 2003f. Support for EPA Proposal to 

Approve n propyl bromide and 

Comments Pursuant to Section D. 

Flammability of Protection of 

Stratospheric Ozone: Listing of 

Substitutes for Ozone Depleting 

Substances—n-Propyl Bromide: 

Proposed Rule Federal Register Vol. 68 

No. 106, June 3, 2003. Enviro Tech 

International, Inc. Comments Regarding 

Proposed Rule & Exhibit A Richard 

Morford, Enviro Tech International. 

August 3, 2003. (EPA–HQ–OAR–2002–

0064–0047) 

Morford, 2003g. Enviro Tech International, 

Inc. Combined Exhibits to Comment 

0047/Morford, 2003f on Proposed Rule 

Richard Morford, Enviro Tech 

International. August 3, 2003. (EPA–HQ–

OAR–2002–0064–0048) 

Morford, 2003h. Initial Comments to 

Protection of Stratospheric Ozone: 

Listing of Substitutes for Ozone 

Depleting Substances—n-Propyl 

bromide: Proposed Rule Federal Register 

Vol. 68 No. 106, June 3, 2003. Richard 

Morford, Enviro Tech International. June 


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26, 2003. (EPA–HQ–OAR–2002–0064–

0002) 

NAS, 1983. The National Academies of 

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1983. Available online at http:// 

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Nemhauser, 2005. ‘‘Bromopropane: A Health 

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Public Health Service, Centers for 

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NIOSH, 2002a. NIOSH Health Hazard 

Evaluation Report: HETA # 98–0153–

2883; Custom Products, Inc.; 

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Occupational Safety and Health. 

November 2002. Available online at 

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pdfs/1998-0153-2883.pdf. (EPA–HQ–

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NIOSH, 2002b. NIOSH Health Hazard 

Evaluation Report: HETA #2000–0410–

2891; STN Cushion Company; 

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2002. Available online at http:// 

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2000-410-2891.pdf. (A–2001–07, II–A–

31) 

NIOSH, 2003a. NIOSH Health Hazard 

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Industries, Inc. Sawmills, NC. Available 

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reports/pdfs/1999-0260-2906.pdf. (EPA–

HQ–OAR–2002–0064–0094) 

NTP, 2003. Results of 13-week Inhalation 

Testing by the National Toxicology 

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OEHHA, 2006. State Of California 

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Assessment. Chemicals Known To The 

State To Cause Cancer Or Reproductive 

Toxicity. June 9, 2006. (EPA–HQ–OAR–

2002–0064–0124) 

O’Malley, 2004. Letter from Nancy O’Malley, 

Toxicology Advisor, Albemarle 

Corporation to The Science Group of the 

American Conference of Governmental 

Industrial Hygienists. Comments on the 

draft Documentation for proposed TLV 

for 1-bromopropane (1-BP). July 30, 

2004. (EPA–HQ–OAR–2002–0064–0128) 

Raymond and Ford, 2005. ‘‘Clinical Case 

Presentations from a Foam Furniture 

Fabrication Plant in North Carolina,’’

Presentation by Drs. Larry Raymond and 

Marsha Ford at the North American 

Congress of Clinical Toxicologists. 

September 14, 2005. (EPA–HQ–OAR–

2002–0064–0170) 

Risotto, 2003. Comments of the Halogenated 

Solvents Industry Alliance on nPB 

proposed rule. June, 2003. (EPA–HQ–

OAR–2002–0064–0050) 

Rodricks, 2002. October 21, 2002 remarks 

from Dr. J. Rodricks, Environ, to R. 

Morford, Enviro Tech International 

concerning derivation of an OEL for npropyl bromide with cover letter to EPA 

from Enviro Tech International (A–2001–

07, II–D–65) 

Rozman and Doull, 2002. ‘‘Derivation of an 

Occupational Exposure Limit for nPropyl Bromide Using an Improved 

Methodology’’ App Occu. Env. Hyg. 17: 

711–716 (A–2001–07, II–D–63) 

Rozman and Doull, 2005. Presentation by 

Drs. Rozman and Doull at the North 

American Congress of Clinical 

Toxicologists. September 14, 2005. 

(EPA–HQ–OAR–2002–0064–0126) 

RTI, 2005. Report on uptake and metabolism 

of 1-bromopropane in rats and mice. 

Research Triangle Institute report for the 

National Toxicology Program. June, 

2005. (EPA–HQ–OAR–2002–0064–0077, 

–0080, –0081, –0082, –0101, –0104, 

–0137, –0137.1) 

Ruckriegel, 2003. Comment on n-Propyl 

Bromide Recommended Workplace 

Exposure Level in Proposed Rule 

Published in Federal Register Vol. 68, 

No. 106, June 3, 2003. August 2, 2003 

(EPA–HQ–OAR–2002–0064–0055) 

Rusch and Bernhard, 2003. Comments on 

proposed regulation of n-propyl bromide 

from Steven Bernhardt and George 

Rusch, Honeywell. August 1, 2003. 

(EPA–HQ–OAR–2002–0064–0059) 

Rusch, 2003. Late comments on proposed 

regulation of n-propyl bromide from 

George Rusch, Honeywell. (EPA–HQ–

OAR–2002–0064–0068) 

Sekiguchi S, Suda M, Zhai YL, Honma T., 

‘‘Effects of 1-bromopropane, 2- 

bromopropane, and 1,2-dichloropropane 

on the estrous cycle and ovulation in 

F344 rats.’’ Toxicol Lett 2002 Jan 

5;126(1):41–9 (A–2001–07, II–D–39) 

SLR International, 2001. ‘‘Inhalation 

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Tech International, Inc. 2001. (A–2001–

07, II–D–15) 

Smith, 2003. Comments on Protection of 

Stratospheric Ozone: Listing of 

Substitutes for Ozone-Depleting 

Substances—n-Propyl Bromide, FR Vol. 

68, No. 106, June 3, 2003. R.L. Smith, 

Albemarle Corporation. July 23, 2003. 

(EPA–HQ–OAR–2002–0064–0067) 

Sohn et al., 2002. Sohn YK, Suh JS, Kim JW, 

Seo HH, Kim JY, Kim HY, Lee JY, Lee 

SB, Han JH, Lee YM, Lee JY. ‘‘A 

histopathologic study of the nervous 

system after inhalation exposure of 1- 

bromopropane in rat.’’ Toxicol Lett. 2002 

May 28;131(3):195–201. (EPA–HQ–

OAR–2002–0064–0127) 

Stelljes, 2003. Comments from Dr. Marc 

Stelljes, SLR International, on proposed 

rule on n-propyl bromide. (HQ–EPA–

OAR–2002–0064–0022) 

Stelljes and Wood, 2004. Stelljes, M., Wood, 

R. Development of an occupational 

exposure limit for n-propylbromide 

using benchmark dose methods. 

Regulatory Toxicology and 

Pharmacology 40 (2004) 136–150 (EPA–

HQ–OAR–2002–0064–0087) 

Stelljes, ME, 2005. Mechanistic Hypothesis 

for n-Propylbromide and Ramifications 

for Occupational Exposure Limit in the 

United States. Technical Memorandum 

to EnviroTech International. 7 

September, 2005. (EPA–HQ–OAR–2002–

0064–0144) 

Stump, 2005. ‘‘The Reproductive Toxicity of 

nPB in Rats,’’ Presentation by Dr. Donald 

Stump at the North American Congress 

of Clinical Toxicologists. September 14, 

2005. (EPA–HQ–OAR–2002–0064–0076) 

Swanson, M.B., J.R. Geibig, and K.E. Kelly. 

2002. Alternative Adhesives 

Technologies: Foam Furniture and 

Bedding Industries, Final Draft. Volume 

2: Risk Screening and Comparison. 

Chapter 4: Exposure Assessment. 

Produced by the University of Tennessee 

Center for Clean Products and Clean 

Technologies under a grant from EPA’s 

Design for the Environment Branch, 

Office of Pollution and Prevention and 

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TERA, 2004. Toxicological Excellence for 

Risk Assessment. Scientific Review of 1- 

Bromopropane Occupational Exposure 

Limit Derivations—Preliminary 

Thoughts and Areas for Further 

Analysis. 2004. (EPA–HQ–OAR–2002–

0064–0189) 

Toraason, M., Lynch, D.W., DeBorda, D.G., 

Singh, N., Krieg, E., Butler, 

M.A.,Toennis, C.A., Nemhauser, J.B., 

2006. DNA damage in leukocytes of 

workers occupationally exposed to 1- 

bromopropane. Mutation Research 603 

(2006) 1–14 (EPA–HQ–OAR–2002–0064–

0130) 

U.S. EPA, 1991. Guidelines for 

Developmental Toxicity Risk 

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Protection Agency. (A–2001–07, II–A–

51) 

U.S. EPA, 1994b. U.S. Environmental 

Protection Agency (US EPA). 1994. 

Methods for derivation of inhalation 

reference concentrations and application 

of inhalation dosimetry. EPA/600/8–90/ 

066F. Office of Health and 

Environmental Assessment, Washington, 

DC. 1994. (A–2001–07, II-A–16) 

U.S. EPA, 1995a. The Use of the Benchmark 

Dose Approach in Health Risk 

Assessment. EPA/630–R–94–007. Risk 

Assessment Forum, Washington, DC. (A–

2001–07, II–A–17) 

U.S. EPA, 1995b. SCREEN3 air dispersion 

model. (A–2001–07, II-A–53) 

U.S. EPA, 1996. Guidelines for Reproductive 

Toxicity Risk Assessment. U.S. 

Environmental Protection Agency, Risk 

Assessment Forum, Washington, DC, 

630/R–96/009, 1996. (EPA–HQ–OAR–

2002–0064–0109) 

Wang et al., 2003. H. Wang, G. Ichihara, H. 

Ito, K. Kato, J. Kitoh, T. Yamada, X. Yu, 

S. Tsuboi, Y. Moriyama, and Y. 

Takeuchi. 2003. ‘‘Dose-Dependant 

Biochemical Changes in RateCentral 

Nervous System after 12-Week Exposure 

to 1-Bromopropane’’ NeuroToxicology 

24: 199–206 (EPA–HQ–OAR–2002–

0064–0088) 

Werner, 2003. Comments from 3M on nPB 

proposed rule. (EPA–HQ–OAR–2002–

0064–0058). 


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WIL, 2001. WIL Research Laboratories. ‘‘An 

inhalation two-generation reproductive 

toxicity study of 1-bromopropane in 

rats.’’ Sponsored by the Brominated 

Solvent Consortium. May 24, 2001. (A–

2001–07, II–D–10) 

Yamada T. et al., 2003. Exposure to 1- 

Bromopropane Causes Ovarian 

Dysfunction in Rats. Toxicol Sci 71:96–

103 (EPA–HQ–OAR–2002–0064–0097) 

Listings for Each End Use 

Beck and Caravati, 2003. Full citation above 

for ‘‘Human Health’’ section. 

Calhoun County, 2005. Summary of Court 

Case against Franklin Technologies and 

Mid-South Adhesive Company in 

Calhoun County, MS. (EPA–HQ–OAR–

2002–0064–0217) 

Collatz, 2003. Comment entitled ‘‘Addition of 

n-Propyl-Bromide to the Significant New 

Alternatives Policy (SNAP) List’’

submitted by Mark Collatz, Director of 

Government Relations, The Adhesive 

and Sealant Council, Inc. 04–Aug–2003. 

(EPA–HQ–OAR–2002–0064–0066) 

Confidential submission, 1998. Full citation 

above in ‘‘Human Health’’ section. 

CSMA, 1998. Letter with attachments from J. 

DiFazio, Chemical Specialties 

Manufacturers Association to C. 

Newberg, EPA Re: Maintaining the 

Current Exemption under Section 610 of 

the Clean Air Act for Use of HCFC–141b 

in Electronic Cleaning and Aircraft 

Maintenance. September 10, 1998. (EPA–

HQ–OAR–2002–0064–0153) 

Harper, 2005. Full citation above for 

‘‘Availability’’ section. 

ICF, 2006a. Full citation above for section on 

‘‘Impacts on the atmosphere, local air 

quality, and other environmental 

impacts’’. 

Lake City Army Ammunition Plant, 2004. 

Full citation above in ‘‘Human 

Health’’section. 

Linnell, 2003. Comments from the 

Electronics Industry Alliance. (IV–D–25/ 

EPA–HQ–OAR–2002–0064 items –0043, 

–0044, and –0045) 

Majersik et al., 2004. Full citation above for 

‘‘Human Health’’ section. 

Majersik et al, 2005. Full citation above for 

‘‘Human Health’’ section. 

Miller, 2005. Full citation above for ‘‘Human 

Health’’ section. 

NIOSH, 2000a. U.S. Dept. of Health and 

Human Services, Letter to Marx 

Industries, Inc., February 1, 2000. Re: 

results of nPB exposure assessment 

survey conducted Nov. 16–17, 1999. (A–

2001–07, II–D–7) 

NIOSH, 2000b. U.S. Dept. of Health and 

Human Services, Letter to Custom 

Products Inc., December 21, 2000. Re: 

results of nPB exposure assessment 

survey conducted Nov. 16, 2000. (HHE 

Report 98–0153) (A–2001–07, II–D–8) 

NIOSH, 2001. U.S. Dept. of Health and 

Human Services, Letter to STN Cushion 

Company, March 7, 2001. Re: Results of 

nPB exposure assessment survey 

conducted November 14, 2000. (A–2001–

07, II–D–9) 

NIOSH, 2002a. Full citation above in 

‘‘Human Health’’ section. 

NIOSH, 2002b. Full citation above in 

‘‘Human Health’’ section. 

NIOSH, 2003a. NIOSH Health Hazard 

Evaluation Report #99–0260–2906 Marx 

Industries, Inc. Sawmills, NC Available 

online at http://www.cdc.gov/niosh/hhe/ 

reports/pdfs/1999–0260–2906.pdf. (EPA–

HQ–OAR–2002–0064–0094) 

Raymond and Ford, 2005. Full citation above 

for ‘‘Human Health’’ section. 

U.S. EPA, 2004. U.S. EPA Solvent Market 

Report: The U.S. Solvent Cleaning 

Industry and the Transition to Non 

Ozone Depleting Substances. Prepared 

for U.S. Environmental Protection 

Agency, Significant New Alternatives 

Policy (SNAP) Program by ICF 

Consulting. September 2004. (EPA–HQ–

OAR–2002–0064–0106) 

Werner, 2003. Full citation above for 

‘‘Human Health’’ section. 

Williams, 2005. Full citation above for 

‘‘Availability’’ section. 

What other options did EPA consider? 

ACGIH, 2002. Industrial Ventilation: A 

Manual of Recommended Practice 23rd 

Edition. American Conference of 

Governmental Industrial Hygienists, 

Cincinnati, Ohio Available online at 

http://www.acgih.org. 

CSMA, 1999. Full citation above for 

‘‘Decisions for Each Sector and End Use’’

section. 

Ensolv, 2006. Material Safety Data Sheet for 

Ensolv Solvents. Enviro Tech 

International. February, 2006. (EPA–HQ–

OAR–2002–0064–0143) 

ERG, 2004. Analysis of Health and 

Environmental Impacts of ODS 

Substitutes—Evaluating the need to set a 

short-term exposure or ceiling limit for npropyl bromide. ERG. June 8, 2004. 

ICF, 2006a. Full citation above for section on 

‘‘Impacts on the atmosphere, local air 

quality, and other environmental 

impacts’’. 

Lake City Army Ammunition Plant, 2004. 

Full citation above for ‘‘Decisions for 

Each Sector and End Use’’ section. 

Linnell, 2003. Full citation above for ‘‘Ozone 

Depletion Potential and Other 

Environmental Impacts’’ section. 

Micro Care, 2006. Web page for Micro Care 

Corporation on the Trigger GripTM

Dispensing System. URL at http:// 

www.microcare.com/products/PDF/PS05T_G.html, last update January 19, 

2006. Also see http:// 

www.microcare.com/images/PDF–CSPAllied%20Worker%20Exposures.pdf. 

NIOSH, 2000a. U.S. Dept. of Health and 

Human Services, Letter to Marx 

Industries, Inc., February 1, 2000. Re: 

Results of nPB exposure assessment 

survey conducted Nov. 16–17, 1999. (A–

2001–07, II–D–7) 

NIOSH, 2002a. NIOSH Health Hazard 

Evaluation Report: HETA # 98–0153–

2883; Custom Products, Inc.; 

Mooresville, NC. National Institute for 

Occupational Safety and Health. 

November 2002. Available online at 

http://www.cdc.gov/niosh/hhe/reports/ 

pdfs/1998-0153-2883.pdf. (EPA–HQ–

OAR–2002–0064–0093) 

NIOSH. 2002b. NIOSH Health Hazard 

Evaluation Report: HETA #2000–0410–

2891; STN Cushion Company; 

Thomasville, NC. National Institute for 

Occupational Safety and Health. August 

2002. Available online at http:// 

www.cdc.gov/niosh/hhe/reports/pdfs/ 

2000-0410-2891.pdf. (A–2001–07, II–A–

31) 

NIOSH, 2003a. NIOSH Health Hazard 

Evaluation Report #99–0260–2906 Marx 

Industries, Inc. Sawmills, NC Available 

online at http://www.cdc.gov/niosh/hhe/ 

reports/pdfs/1999-0260-2906.pdf. (EPA–

HQ–OAR–2002–0064–0094) 

NIOSH, 2003b. Method 1025 for 1- and 2- 

Bromopropane. NIOSH Manual of 

Analytical Methods, 4th Edition, March 

15, 2003. (EPA–HQ–OAR–2002–0064–

0173) 

NIOSH, 2003c. Method 1003 for Halogenated 

Hydrocarbons. NIOSH Manual of 

Analytical Methods, 4th Edition, March 

15, 2003. (EPA–HQ–OAR–2002–0064–

0134) 

Williams, 2005. Full citation above for 

‘‘Availability’’ section. 

What are the anticipated costs of this 

regulation to the regulated community? 

U.S. EPA, 2006. Analysis of Economic 

Impacts of nPB Rulemaking. 2006. 

Comparison of EPA’s June 2003 

Proposal and This Proposal 

ACGIH, 2005. Full citation above for ‘‘Human 

Health’’ section. 

CERHR, 2002a. Full citation above for 

‘‘Human Health’’ section. 

CERHR, 2002b. Full citation above for 

‘‘Human Health’’ section. 

Doull and Rozman, 2001. Derivation of an 

Occupational Exposure Limit for nPropyl Bromide, prepared by John Doull, 

PhD., M.D., and Karl K. Rozman, PhD., 

D.A.B.T. submitted by Envirotech 

International, Inc. (A–2001–07, II–D–14) 

ICF, 2001. Brief Discussion of the BMD 

Approach: Overview of its Purpose, 

Methods, Advantages, and 

Disadvantages. Prepared for U.S. EPA. 

(A–2001–07, II–A–52) 

ICF, 2002a. Full citation above for ‘‘Human 

Health’’ section. 

ICF, 2002b. Comments on the NTP-Center for 

the Evaluation of Risks to Human 

Reproduction, Final Report on 1- 

Bromopropane. Cover Letter Dated 5/9/ 

02. (EPA–HQ–OAR–2002–0064–0013) 

ICF, 2006a. Full citation above for section on 

‘‘Impacts on the atmosphere, local air 

quality, and other environmental 

impacts’’. 

Rodricks, 2002. Full citation above for 

‘‘Human Health’’ section. 

Rozman and Doull, 2002. Full citation above 

for ‘‘Human Health’’ section. 

Rozman and Doull, 2005. Full citation above 

for ‘‘Human Health’’ section. 

SLR International, 2001. Full citation above 

for ‘‘Human Health’’ section. 

Stelljes and Wood, 2004. Full citation above 

for ‘‘Human Health’’ section. 

Stelljes, ME. 2005. Full citation above for 

‘‘Human Health’’ section. 


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TERA, 2004. Full citation above for ‘‘Human 

Health’’ section. 

WIL, 2001. Full citation above for ‘‘Human 

Health’’ section. 

How can I use nPB as safely as possible? 

ACGIH, 2002. Full citation above for ‘‘What 

other options did EPA consider’’ section. 

Statutory and Executive Order Reviews 

U.S. EPA, 2006. Analysis of Economic 

Impacts of nPB Rulemaking. 2006. 

U.S. EPA, 2007. Analysis of Economic 

Impacts of Proposed nPB Rule for 

Aerosols and Adhesives. 2007. 

List of Subjects in 40 CFR Part 82 

Environmental protection, 

Administrative practice and procedure, 

Air pollution control, Reporting and 

recordkeeping requirements. 

Dated: May 15, 2007. 

Stephen L. Johnson, 

Administrator. 

For the reasons set out in the 

preamble, 40 CFR part 82 is proposed to 

be amended as follows: 

PART 82—PROTECTION OF 

STRATOSPHERIC OZONE 

1. The authority citation for Part 82 

continues to read as follows: 

Authority: 42 U.S.C. 7414, 7601, 7671—

7671q. 

2. Subpart G is amended by adding 

Appendix S to read as follows: 

Subpart G—Significant New 

Alternatives Policy Program 

* * * * * 

Appendix S to Subpart G—Substitutes 

Subject to Use Restrictions and 

Unacceptable Substitutes 

Listed in the May 30, 2007 final rule. 

AEROSOLS—UNACCEPTABLE SUBSTITUTES

End use Substitute Decision Further information 

Aerosol solvents .......... n-propyl bromide (nPB) as a substitute for 

CFC–113, HCFC–141b, and methyl chloroform.

Unacceptable ............. EPA finds unacceptable risks to human 

health in this end use compared to other 

available alternatives. nPB, also known as 

1-bromopropane, is Number 106–94–5 in 

the CAS Registry. 

ADHESIVES, COATINGS, AND INKS—SUBSTITUTES THAT ARE ACCEPTABLE SUBJECT TO USE CONDITIONS

End use Substitute Decision Use conditions Further information 

Coatings n-propyl bromide 

(nPB) as a substitute for methyl 

chloroform, CFC–

113, and HCFC–

141b.

Acceptable subject 

to use conditions.

Use is limited to coatings at facilities 

that, as of May 30, 2007, have provided EPA information demonstrating 

acceptable workplace exposures.

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-brompropane, is 

Number 106–94–5 in the CAS Registry. 

As of May 30, 2007, the Lake City Army Ammunition Plant is the only facility using nPB in coatings that has provided information to EPA that 

meets this condition. 

ADHESIVES, COATINGS, AND INKS—UNACCEPTABLE SUBSTITUTES

End use Substitute Decision Further information 

Adhesives .................... n-propyl bromide (nPB) as a substitute for 

CFC–113, HCFC–141b, and methyl chloroform.

Unacceptable ............. EPA finds unacceptable risks to human 

health in this end use compared to other 

available alternatives. nPB, also known as 

1-bromopropane, is Number 106–94–5 in 

the CAS Registry. 

[FR Doc. E7–9706 Filed 5–29–07; 8:45 am] 

BILLING CODE 6560–50–P 


rwilkins on PROD1PC63 with PROPOSALS3