[Federal Register Volume 59, Number 20 (Monday, January 31, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-1556]


[[Page Unknown]]

[Federal Register: January 31, 1994]


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Part III





Environmental Protection Agency





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40 CFR Parts 9 and 68




List of Regulated Substances and Thresholds for Accidental Release 
Prevention and Risk Management Programs for Chemical Accident Release 
Prevention; Final Rule and Notice
ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 9 and 68

[FRL-4828-6]

 
List of Regulated Substances and Thresholds for Accidental 
Release Prevention; Requirements for Petitions Under Section 112(r) of 
the Clean Air Act as Amended

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: The Environmental Protection Agency (EPA) is promulgating the 
list of regulated substances and thresholds required under section 
112(r) of the Clean Air Act as amended. The list is composed of three 
categories: A list of 77 toxic substances, a list of 63 flammable 
substances, and explosive substances with a mass explosion hazard as 
listed by the United States Department of Transportation (DOT). 
Threshold quantities are established for toxic substances ranging from 
500 to 20,000 pounds. For all listed flammable substances the threshold 
quantity is established at 10,000 pounds. For explosive substances the 
threshold quantity is established at 5,000 pounds. The list and 
threshold quantities will identify facilities subject to chemical 
accident prevention regulations promulgated under section 112(r) of the 
Clean Air Act as amended; a proposed regulation for such requirements 
has been published in the Federal Register on October 20, 1993, 
entitled Risk Management Programs for Chemical Accidental Release 
Prevention. EPA is also promulgating in this regulation the 
requirements for the petition process for additions to, or deletions 
from, the list of regulated substances. EPA is deferring action on a 
proposed exemption from regulation for listed flammable substances when 
used solely for facility consumption as fuel. For a document relating 
to the proposed exemption, see a supplemental notice published 
elsewhere in this issue.

DATES: This rule is effective March 2, 1994.

ADDRESSES: Docket: Supporting information used in developing both the 
proposed and the final rule is contained in Docket No. A-91-74. The 
docket is available for public inspection and copying from 8 a.m. to 4 
p.m., Monday through Friday, at the EPA's Air Docket Section, Waterside 
Mall, room M 1500, U.S. Environmental Protection Agency, 401 M Street, 
SW., Washington, DC 20460. A reasonable fee may be charged for copying.

FOR FURTHER INFORMATION CONTACT: Vanessa Rodriguez, Chemical Engineer, 
(202) 260-7913, Chemical Emergency Preparedness and Prevention Office, 
Mailcode 5101, U.S. Environmental Protection Agency, 401 M Street, SW., 
Washington, DC 20460, or the Emergency Planning and Community Right-to-
Know Hot Line at 1-800-535-0202.

SUPPLEMENTARY INFORMATION: The information presented in this preamble 
is organized as follows:

I. Introduction
    A. Statutory Authority
    B. Background
II. Clean Air Act Amendments of 1990
    A. Prevention of Accidental Releases
    B. List of Substances and Thresholds; Petitions for Additions 
and Deletions
    1. Legislative Requirements
    2. Summary of Proposed Rule
III. Public Participation
IV. Discussion of Comments and Major Regulatory Changes
    A. List of Substances and Threshold Quantities
    1. Toxic Substances
    a. Listing Criteria
    b. Specific Substances
    c. Other List Options Considered
    d. Threshold Quantities
    e. Other Threshold Quantity Options Considered
    2. Flammable Substances
    3. Explosives
    B. Threshold Determination
    1. Basis for Threshold Determination
    2. Mixture Exemption
    a. Toxic Substances
    b. Flammable Substances
    c. Explosive Substances
    3. Other Threshold Exemptions
    C. Petition Process
    D. Definitions
    E. Exemptions
    F. Scope
V. Summary of Provisions of the Final Rule
VI. Required Analyses
    A. E.O. 12866
    B. Regulatory Flexibility Act
    C. Paperwork Reduction Act
    D. Display of OMB Control Numbers

I. Introduction

A. Statutory Authority

    This final rule is being issued under sections 112(r) and 301 of 
the Clean Air Act (CAA or Act) as amended (42 U.S.C. 7412(r), 7601).

B. Background

    Public awareness of the potential danger from accidental releases 
of hazardous chemicals has increased over the years as serious chemical 
accidents have occurred around the world (e.g., the 1974 explosion in 
Flixborough, England, and the 1976 release of dioxin in Seveso, Italy). 
Public concern intensified following the 1984 release of methyl 
isocyanate in Bhopal, India, which killed more than 2,000 people living 
near the facility. A subsequent release from a chemical facility in 
Institute, West Virginia, sent more than 100 people to the hospital and 
made Americans aware that such accidents can and do happen in the 
United States.
    In response to this public concern and the hazards that exist, the 
U.S. Environmental Protection Agency (EPA) began its Chemical Emergency 
Preparedness Program (CEPP) in 1985, as part of the Agency's Air Toxics 
Strategy. CEPP was a voluntary program to encourage state and local 
authorities to identify hazards in their areas and to plan for chemical 
emergency response actions. In 1986, Congress adopted many of the 
elements of CEPP in the Emergency Planning and Community Right-to-Know 
Act of 1986 (EPCRA), also known as Title III of the Superfund 
Amendments and Reauthorization Act of 1986 (SARA Title III). EPCRA 
requires states to establish state and local emergency planning groups, 
namely the State Emergency Response Commissions (SERCs) and the Local 
Emergency Planning Committees (LEPCs), to develop emergency response 
plans for each community. EPCRA requires facilities to provide 
information on the hazardous chemicals they have on-site; the 
information collected is available to the public through the SERC/LEPC 
structure. This information forms the foundation of both the emergency 
response plans and the public-industry dialogue on risks and risk 
reduction.
    Congress required EPA, under EPCRA (SARA Title III) section 305(b), 
to conduct a review of emergency systems to monitor, detect, and 
prevent chemical accidents. The final report to Congress, Review of 
Emergency Systems (EPA, 1988), concluded that the prevention of 
accidental releases requires an integrated approach that considers 
technologies, operations, and management practices. The report 
emphasized the importance of management commitment to safety.
    In 1986, EPA established a chemical accident prevention program to 
collect information on chemical accidents and work with other groups to 
increase knowledge of prevention practices and encourage industry to 
improve safety at facilities. Under this program, EPA developed its 
Accidental Release Information Program (ARIP) to collect data on the 
causes of chemical accidents and the steps facilities take to prevent 
recurrences. EPA also developed a program for conducting chemical 
safety audits at facilities. Through the audit program, EPA 
headquarters and regional staff, as well as state and local officials, 
learned about integrated approaches to process safety from facilities. 
EPA has also worked with trade associations, professional 
organizations, labor, environmental groups, and other Federal agencies 
to determine how best to reach smaller operations, which the section 
305(b) study indicated are less aware of risks than larger facilities. 
EPA has also been an active participant in international efforts 
related to chemical accident prevention, particularly through the 
Organization for Economic Cooperation and Development (OECD), which has 
held five international workshops from 1989 through 1991 to discuss 
issues related to accident prevention, preparedness, and response, and 
has developed guidelines for member countries.
    In addition to EPA's work in this area, other agencies and states 
have developed programs related to chemical accident prevention. The 
Occupational Safety and Health Administration (OSHA) promulgated a 
final rule on chemical process safety management amending 29 CFR 
1910.109 and adding 29 CFR 1910.119 (57 FR 6356, February 24, 1992) as 
required under section 304 of the Clean Air Act Amendments of 1990 (CAA 
Amendments). Four states--New Jersey, California, Delaware, and 
Nevada--have operational risk management programs. Additional states 
have begun to address accidental release prevention as part of their 
air toxics program development.
    Professional and trade organizations have also developed programs 
in this area. For example, the Center for Chemical Process Safety of 
the American Institute of Chemical Engineers has published guidance on 
the management of chemical process safety. The Chemical Manufacturers' 
Association has adopted a Responsible CareTM program, which all 
members must comply with to maintain membership. The American Petroleum 
Institute has developed a similar program, Management of Process 
Hazards; Recommended Practice 750 (RP 750), for its members. In 1982, 
the European Community adopted the Seveso Directive (82/501/EEC, as 
amended), which requires facilities handling certain chemicals to 
develop a safety report that is similar to a risk management plan.

II. Clean Air Act Amendments of 1990

A. Prevention of Accidental Releases

    In the CAA Amendments, signed into law on November 15, 1990, 
Congress added subsection (r) to CAA section 112 for the prevention of 
chemical accidents. The goals of the chemical accident prevention 
provisions are to focus on chemicals that pose a significant hazard to 
the community should an accident occur, to prevent their accidental 
release and to minimize the consequences of such releases.
    Section 112(r) of the CAA has a number of provisions. Under section 
112(r) owners and operators of stationary sources who produce, process, 
handle, or store substances listed under section 112(r)(3) or any other 
extremely hazardous substances have a general duty to initiate specific 
activities to prevent and mitigate accidental releases. The general 
duty requirements apply to stationary sources regardless of the 
quantity of substances managed at the facility. Activities such as 
identifying hazards which may result from accidental releases using 
appropriate hazard assessment techniques; designing, maintaining and 
operating a safe facility; and minimizing the consequences of 
accidental releases if they occur would be essential activities to be 
taken as necessary to satisfy the general duty requirements. As a 
matter of business practice, owners and operators of these stationary 
sources have a duty to conduct these activities under section 112(r) in 
the same manner and to the same extent as an employer's duties under 
OSHA's general duty clause in section 654 of title 29 of the United 
States Code.
    Section 112(r)(3) of the CAA requires EPA to promulgate an initial 
list of at least 100 substances (``regulated substances'') that are 
known to cause, or may be reasonably anticipated to cause, death, 
injury, or serious adverse effects to human health or the environment 
if accidentally released. EPA is required to set threshold quantities 
for each listed substance. Under CAA section 112(r)(7), the Act 
requires EPA to promulgate reasonable regulations and appropriate 
guidance to provide for the prevention and detection of accidental 
releases and for responses to such releases. The accident prevention 
regulations will apply to stationary sources that have present more 
than a threshold quantity of a regulated substance. These regulations 
shall address, as appropriate, the use, operation, repair, and 
maintenance of equipment to monitor, detect, inspect, and control 
releases, including training of personnel in the use and maintenance of 
equipment or in the conduct of periodic inspections. The regulations 
shall include requirements for the development and submission of Risk 
Management Plans (RMPs) by regulated sources. The RMP shall include a 
hazard assessment, a prevention program, and an emergency response 
program. The proposed rule for accident prevention, Risk Management 
Programs for Chemical Accidental Release Prevention, was published on 
October 20, 1993 (58 FR 54190).
    The Act establishes a Chemical Safety and Hazard Investigation 
Board to investigate (or cause to be investigated) chemical accidents 
at facilities and recommend to Congress, Federal, state, local 
authorities, and the public actions that can be taken to improve 
chemical safety. Under the Act, EPA is authorized to conduct studies 
related to accidental releases, including research on hazard 
assessments, hydrogen fluoride, and air dispersion modeling. A report 
to Congress on hydrogen fluoride was completed and published by the 
Agency in September 1993, entitled Hydrogen Fluoride Study, Report to 
Congress, section 112(n)(6) of the Clean Air Act as Amended.
    The Clean Air Act also addressed the approval of state programs and 
delegation of Federal authorities for all section 112 requirements in 
section 112(l). Thus, state Accidental Release Prevention programs are 
approved through the authorities in section 112(l). The approval 
provisions of section 112(l)(5) include a determination that: A state 
program contains the authorities to assure compliance by all sources 
within the state with each applicable standard, regulation, or 
requirement; adequate resources are available to implement the program; 
an expeditious implementation schedule is in place to ensure that 
affected sources achieve compliance; and the state program is otherwise 
in compliance with the objectives of the Act and guidance published 
under section 112(l)(2).
    The Agency promulgated a final rule in November 1993 which 
addresses the approval requirements of section 112(l) entitled Approval 
of State Programs and Delegation of Federal Authorities. These 
requirements can be found in 40 CFR part 63--Subpart E. Section 63.95 
specifically address the required components of an accidental release 
prevention program. The Agency is currently working on developing 
further guidance to states in regard to the development of an 
accidental release prevention program.
    Under section 304 of the CAA Amendments OSHA was required to 
promulgate a chemical process safety management standard to protect 
employees from hazards associated with accidental releases of highly 
hazardous chemicals in the workplace. OSHA promulgated a final rule 
amending 29 CFR 1910.109 and adding 29 CFR 1910.119 (57 FR 6356, 
February 24, 1992) that requires a chemical process safety management 
(PSM) program for any process involving a highly hazardous chemical at 
or above a specified threshold quantity. The rule applies to a list of 
highly hazardous toxic and reactive substances at particular threshold 
quantities, flammable liquids or flammable gases in quantities of 
10,000 pounds or more and to the manufacture of explosives and 
pyrotechnics.

B. List of Substances and Thresholds; Petitions for Additions and 
Deletions

1. Legislative Requirements
    The Act requires EPA to promulgate an initial list of at least 100 
substances that, in the event of an accidental release, are known to 
cause or may reasonably be anticipated to cause death, injury, or 
serious adverse effects to human health or the environment. An 
accidental release is defined under CAA section 112(r)(2)(A) as ``an 
unanticipated emission * * * into the ambient air from a stationary 
source.'' In developing this list, EPA was required to consider, but 
was not limited to, the list of extremely hazardous substances (EHSs) 
promulgated under EPCRA (SARA Title III) section 302.
    Congress listed the following 16 substances to be included in the 
initial list (the Chemical Abstracts Service (CAS) Registry number is 
provided in parentheses):

Chlorine (7782-50-5)
Ammonia and anhydrous ammonia (7664-41-7)
Methyl chloride (74-87-3)
Ethylene oxide (75-21-8)
Vinyl chloride (75-01-4)
Methyl isocyanate (624-83-9)
Hydrogen cyanide (74-90-8)
Hydrogen sulfide (7783-06-4)
Toluene diisocyanate, represented by:
--Toluene 2,4-diisocyanate (584-84-9)
--Toluene 2,6-diisocyanate (91-08-7)
--Toluene diisocyanate, unspecified isomer (26471-62-5)
Phosgene (75-44-5)
Bromine (7726-95-6)
Anhydrous hydrogen chloride (7647-01-0)
Hydrogen fluoride (7664-39-3)
Anhydrous sulfur dioxide (7446-09-5), and
Sulfur trioxide (7446-11-9)

    No air pollutant for which a national primary ambient air quality 
standard has been established may be included on the list, with the 
exception of anhydrous sulfur dioxide and sulfur trioxide, which must 
be included. No substances regulated under Title VI of the Act as 
amended may be included on the list. Title VI covers ozone depleters, 
primarily chlorofluorocarbons (CFCs) and halons. The Act requires EPA 
to review, and if necessary revise, the list of regulated substances 
under section 112(r) at least every five years. EPA may also review and 
if necessary revise the list as a result of petitions. EPA is required 
to develop procedures for petitions to the Agency for the addition of 
substances to, and deletion of substances from, the list; these 
petition procedures are to be consistent with those applicable to the 
list of hazardous air pollutants found in CAA Amendments section 
112(b).
2. Summary of Proposed Rule
    On January 19, 1993 (58 FR 5102), EPA proposed a list of 100 toxic 
substances and threshold quantities, a list of 62 flammable substances 
(gases and volatile liquids) with threshold quantities of 10,000 
pounds, and commercial explosives defined by the Department of 
Transportation (DOT) as Division 1.1 (explosives with mass explosion 
hazard) with a threshold quantity of 5,000 pounds. EPA also proposed 
requirements for a petition process to add or delete chemicals from the 
list.
    Toxic substances were included on the list based on their toxicity, 
physical state, vapor pressure, production volume, and accident 
history. Toxicity criteria used to identify chemicals as extremely 
hazardous substances (EHSs) under EPCRA were used as criteria for the 
proposed list. The acute toxicity criteria are:
    (a) Inhalation LC50  0.5 milligrams per liter of 
air (for exposure time  8 hours), or
    (b) Dermal LD50  50 milligrams per kilogram of body 
weight, or
    (c) Oral LD50  25 milligrams per kilogram of body 
weight where LC50 is the median concentration in air at which 50 
percent of the test animals died, and LD50 is the median lethal 
dose that killed 50 percent of the test animals. In the absence of 
LC50 or LD50 data, LCLo or LDLo data were used for 
listing, where LCLo is the lethal concentration low, or lowest 
concentration in air at which any of the test animals died, and 
LDLo is the lethal dose low, or the lowest concentration at which 
any of the test animals died. Additional substances on the EHS list 
meet the secondary EHS toxicity criteria in light of production volume 
(see appendix B of EPA's Technical Guidance for Hazards Analysis, 
December 1987, which is in the docket for this rulemaking). A vapor 
pressure criterion of 0.5 millimeters of mercury (mm Hg) was used as a 
baseline, based on the vapor pressure of toluene diisocyanate, a 
substance mandated for the initial list by Congress; toxic gases and 
liquids with a vapor pressure of 0.5 mm Hg or higher under ambient 
conditions were considered for listing. Only toxic chemicals in 
commercial production, verified through EPA's Toxic Substances Control 
Act (TSCA) Chemical Inventory, were included on the list. By applying 
these criteria to the 360 chemicals on the EPCRA EHS list, the Agency 
identified 87 potential regulated substances for the CAA Amendments 
section 112(r) list. The Agency also looked at other data sources 
(including the OSHA highly hazardous chemical list) to identify 9 more 
substances for the section 112(r) list. Four additional substances were 
identified for listing based on a combination of toxicity, high 
production volume, and history of accidents involving death or injury. 
Threshold quantities were set for toxic substances based on a ranking 
method that considers toxicity and volatility of the chemicals. EPA 
assigned identical thresholds to chemicals with similar ranking scores, 
ranging from 500 pounds to 10,000 pounds.
    Flammable gases and volatile flammable liquids were included on the 
list based on the flash point and boiling point criteria used by the 
National Fire Protection Association (NFPA) for its highest 
flammability hazard ranking (flash point below 73 deg.F (22.8 deg.C) 
and boiling point below 100 deg.F (37.8 deg.C)) (Fire Protection Guide 
on Hazardous Materials, 1984, 8th edition). Only flammable substances 
in commercial production were listed. The threshold quantity for 
flammable substances was set at 10,000 pounds, based on the potential 
for a vapor cloud explosion.
    Explosives in Division 1.1 were proposed for listing based on their 
potential to detonate. The threshold quantity for explosives was set at 
5,000 pounds because a detonation of this quantity could yield blast 
wave overpressures of 3.0 pounds per square inch (psi) at a distance of 
100 meters from the blast site and could have potentially lethal 
effects in the community beyond the fenceline.
    EPA proposed to apply the threshold quantity to the maximum total 
quantity of a substance in a process. This definition would apply to 
the maximum total quantity, at any one time, in a single vessel, in a 
group of interconnected vessels or in several vessels that could 
potentially be involved at one time in an accidental release. 
Substances in mixtures would be exempted from the threshold 
determination if they represent less than one percent of the mixture by 
weight. EPA also proposed to exempt substances if (1) they are part of 
articles; (2) if they are used as structural components; (3) if they 
are used for janitorial maintenance; or (4) if they are found in 
consumer products, process water, or in water or air from the 
environment or municipal sources. Activities in laboratories were also 
proposed for exemption. In addition, an exemption was proposed for 
flammable substances present at a facility to be used solely for 
consumption as fuel at the facility.
    The Agency also proposed requirements for petitions to add or 
delete regulated substances under section 112(r). The Agency proposed 
to establish that the burden of proof be on the petitioner to 
demonstrate that the criteria for addition and deletion are met. Basic 
administrative and documentation requirements for petitions were also 
included in the proposal.

III. Public Participation

    A hearing was held on the proposed rule in the EPA Auditorium, 401 
M Street, SW., Washington DC, on Tuesday, April 12, 1993. The hearing 
was held to provide interested parties the opportunity for oral 
presentation of data, views, or arguments concerning the proposed rule. 
This hearing was open to the public; a transcript of the public hearing 
is available in the docket. A total of 272 letters were received during 
the public comment period on the proposed rule (an additional 18 were 
received after the close of the public comment period); copies of all 
comment letters received are available for public inspection in the 
docket. A response to comments document, entitled Proposed List of 
Substances and Thresholds for Accidental Release Prevention: Summary 
and Response to Comments, includes a summary of comments received and 
the Agency's responses; the document is available in the docket.

IV. Discussion of Comments and Major Regulatory Changes

    This portion of the preamble discusses comments on major issues 
received on the proposed list and thresholds rule and the principal 
regulatory changes made in the final rule in response to public 
comments. Included in the discussion is the rationale for these changes 
and the Agency action on the comments. Where the proposed regulation 
has not been changed in the final rule, the Agency continues to rely on 
the rationale provided in the proposal notice, supplemented as 
appropriate by additional discussion in this preamble and in the 
response to comments document.

A. List of Substances and Thresholds

    The list of substances and thresholds promulgated today identifies 
sources that are subject to accident prevention regulations promulgated 
under section 112(r)(7) of the Act. The list of substances is intended 
to focus accidental release prevention efforts on those stationary 
sources and substances that pose the most significant risks to the 
community. These risks may be established either by the potential of 
the chemical to cause harm (the inherent hazards and physical/chemical 
properties), known incidents (accident history), or a combination 
thereof. EPA strongly emphasizes that the substances promulgated in 
today's listing are not the only substances that may pose a threat to 
communities upon release. There are large numbers of compounds and 
mixtures in commerce in the U.S. that in specific circumstances could 
be considered dangerous to human health or the environment; however, it 
would not be feasible to include all such substances and circumstances. 
This list should serve to focus prevention efforts and is not a list of 
all substances that could be considered for accident prevention. 
Similarly, the threshold quantities established today may not always 
represent a level below which no hazard exists. Although stationary 
sources will be required to comply with the accidental release 
prevention regulations under section 112(r)(7)(B) only if they have 
listed substances in quantities exceeding the threshold quantity, it 
does not mean that these substances in smaller quantities represent no 
potential hazard to the community in certain circumstances. In support 
of this principle Congress included general duty provisions under 
section 112(r)(1) of the Act.
    Several commenters objected to the listing of classes of substances 
such as explosives or particular substances such as various flammable 
natural gases because these commenters claimed that categorizing these 
chemicals as regulated substances would also make these chemicals 
subject to the general duty clause of section 112(r)(1), and that 
without such listing these chemicals would be outside the scope of 
section 112(r)(1). The general duty provision in section 112(r)(1) 
applies to ``any substance listed pursuant to section 112(r)(3) or any 
other extremely hazardous substance.'' The Agency believes the scope of 
substances covered by section 112(r)(1) is not affected by this 
rulemaking except that by including a substance on the regulated 
substance list, the Agency unambiguously specifies that the general 
duty provisions apply to such chemicals. The plain language of section 
112(r)(1) applies not only to the regulated substances listed today but 
also to ``any other extremely hazardous substance.''
    In discussing nearly identical language in the Senate's Clean Air 
Act Amendments bill of 1989, the Environment and Public Works Committee 
expressed the intent that the term ``extremely hazardous substance'' 
would include not only listed substances under the accident prevention 
provisions and extremely hazardous substances under EPCRA (SARA Title 
III) section 302 but also ``other agents which may or may not be listed 
or otherwise identified by any Government agency which may as the 
result of short-term exposures associated with releases to the air 
cause death, injury or property damage'' (Senate Committee on 
Environment and Public Works, Clean Air Act Amendments of 1989, Senate 
Report No. 228, 101st Congress, 1st Session 211 (1989)--``Senate 
Report''). Regardless of whether a substance is listed under today's 
rule, the general duty to identify and assess hazards associated with 
accidental releases (as defined in section 112(r)(2)), to design and 
maintain a facility to prevent such releases, and to minimize the 
consequences of such releases that do occur, extends to owners and 
operators of any facility that may cause such impacts due to short-term 
exposures. As the Senate makes clear, ``the release of any substance 
which causes death or serious injury because of its acute toxic effect 
or as a result of an explosion or fire or which causes substantial 
property damage by blast, fire, corrosion or other reaction would 
create a presumption that such substance is extremely hazardous.'' 
Senate Report at 211. No revision to the list promulgated today negates 
the applicability of the general duty provisions.
1. Toxic Substances
    a. Listing criteria. Several commenters suggested that EPA modify 
its listing criteria, largely so that EPA's list would be more 
consistent with OSHA's list of Highly Hazardous Substances for its 
Process Safety Management Standard, but also because commenters 
believed EPA's list includes some chemicals that do not pose the 
greatest hazards to the public. Some commenters suggested the proposed 
0.5 mm Hg vapor pressure cut off was too low. Others suggested an 
alternative method of choosing the list of toxics, namely the 
``Substance Hazard Index''. Several commenters also objected to EPA's 
use of accident history as a criterion for listing substances. EPA's 
proposed toxics list was based on the EHS list under SARA Title III, 
with additional consideration of the vapor pressures and accident 
histories for each substance. The proposed list included 50 toxic 
substances that are not listed by OSHA.
    Substance Hazard Index: Some commenters suggested replacing EPA's 
proposed listing criteria with another method labeled the ``Substance 
Hazard Index'' (SHI). The SHI is the ratio of a substance's vapor 
pressure to its acute toxicity; all substances would be ranked by their 
SHI and a cut-off would need to be selected to determine the substances 
to be listed. An SHI value of 1,000 was suggested by commenters as a 
cut-off, but commenters did not provide a technical basis, or any other 
rationale, for why this cut-off was selected. The SHI value of 1,000 
would derive a list of toxic substances that more closely approximates 
OSHA's PSM list than EPA's proposed list; provided that the Agency 
considers only those substances initially proposed for listing as 
toxics.
    EPA generally disagrees with the comments concerning the use of the 
SHI as a listing criterion. The Agency had considered this approach 
during the proposed rule development, but decided not to include it as 
an alternate listing methodology option. EPA instead considered 
toxicity and vapor pressure separately in identifying chemicals for 
listing; the SHI combines these factors. EPA believes that using 
separate toxicity and vapor pressure criteria is a more valid method of 
identifying chemical candidates for listing. Both EPA's method and the 
SHI approach consider properties related to the severity of acute 
health effects (toxicity) and the likelihood of accidental releases of 
the substances (volatility), as required by the Act. However, as 
required by the Act, EPA's approach is based on the list of EHSs as a 
starting point for identification of toxic substances (see Senate 
Report at 218; listing factors used in EHS list are appropriate for 
accidental release program). EPA's approach limits toxic chemicals to 
those meeting the acute toxicity criteria for the EHS list and then 
applies a vapor pressure cut-off. The SHI approach does not include 
specific toxicity or vapor pressure cut-offs but instead specifies a 
cut-off value for a factor combining toxicity and vapor pressure. To 
identify all chemicals meeting the specific SHI cut-off of 1,000 as 
recommended by commenters, chemicals with a much wider range of 
toxicity than those represented by the EHSs would have to be 
considered. Chemicals that are far less toxic than the EHSs would be 
potentially included, improperly characterizing the risk associated 
with them. Moreover, EPA does not believe the SHI method has been 
systematically applied to all substances for development of any current 
chemical list. The state of Delaware used the SHI approach to develop a 
list of substances for its risk management regulation; the SHI 
methodology was applied to existing lists of substances identified by 
use of toxicity criteria and not all substances. The Agency considers 
the SHI to be more appropriate for determining the relative ranking of 
substances in an already established list. The Agency's threshold 
quantity methodology for listed toxics is similar on the toxicity/
volatility ranking principle; it differs from the SHI in that the vapor 
pressure is only part of the factor used to account for the potential 
dispersability of the listed substances. For these reasons, the Agency 
will not adopt the SHI criteria for listing toxic substances.
    Acute Toxicity Criteria: Commenters generally supported EPA's 
consideration of acute toxicity hazards as a basis for listing toxic 
substances under section 112(r). Some commenters, however, recommended 
other measures of toxicity, such as the Emergency Response Planning 
Guidelines (ERPGs) developed by the American Industrial Hygiene 
Association, or data developed by the National Academy of Sciences 
among others. The Agency recognizes the value of these other measures 
and guidelines for purposes of emergency preparedness and prevention 
activities. However, these measures are consensus exposure levels 
judged by the developing organizations to represent concentrations 
above which there may be serious irreversible health effects, or death, 
as a result of a single exposure for a relatively short period of time. 
In addition, the methodology for most of these measures is still in the 
developmental stages, with recommended guidelines or acute exposure 
levels presently available only for a limited number of potentially 
hazardous substances. The Agency believes using acute toxicity data as 
proposed is more appropriate for the review and selection of hazardous 
substances for listing under section 112(r) because acute toxicity data 
directly reflects results of valid mammalian testing and thus is more 
objectively verifiable than judgmental standards.
    Concerns were also expressed about the Agency's focus on acute 
toxicity rather than on chronic toxicity effects as a basis for 
listing. Some commenters also opposed the Agency's consideration of 
acute exposures by the dermal and oral routes. EPA believes that 
chemical accident prevention efforts should focus on those chemicals 
that, because of their inherent toxicity, are most likely to cause 
immediate severe, irreversible health effects following exposures 
during an accidental release. Consequently, for purposes of this 
rulemaking, the Agency is primarily interested in substances that are 
acutely toxic, rather than in substances that could generate a future 
health effect after repeated long term or chronic exposures. 
Furthermore, acute toxicity and lethality data are often readily 
available and the most commonly reported information generated by 
animal toxicity testing. A greater number of potentially hazardous 
substances can therefore be screened on the same basis using these 
values. For purposes of this rule, the listed toxic substances are 
expected to rapidly become airborne, thus human exposure by the 
inhalation route is of primary concern. The Agency believes that using 
data on oral and dermal acute lethality, in addition to inhalation 
lethality, is appropriate for this listing.
    Vapor Pressure Cut-Off: Other commenters suggested that EPA should 
use a higher vapor pressure level as a listing criterion. EPA's vapor 
pressure criterion of 0.5 mm Hg was based on the properties of toluene 
diisocyanate, a substance with relatively low volatility, which was 
mandated for the initial list by Congress. Commenters noted that 
Congress listed toluene diisocyanate because it has been involved in 
accidents, not because of its properties, and that its properties do 
not necessarily provide a valid basis for EPA's vapor pressure 
criterion. Several commenters suggested a vapor pressure of 20 mm Hg 
(18 mm Hg is the approximate vapor pressure of water) but did not 
provide a basis for choosing this or any other vapor pressure 
criterion.
    EPA has considered the comments concerning the proposed vapor 
pressure criterion of 0.5 mm Hg and generally agrees that this low 
vapor pressure level may lead to an overly conservative listing of 
chemicals that pose a relatively lower potential for air releases. EPA 
has decided to set the vapor pressure criterion at the higher level of 
10 mm Hg. In selecting this new vapor pressure cut-off, the Agency 
examined the substances on the proposed list that have vapor pressures 
of less than 10 mm Hg and compared the rate of volatilization expected 
in a large release to the rate expected for substances with a vapor 
pressure greater than 10 mm Hg. As expected, volatilization rates 
increase with increasing vapor pressure and increasing pool sizes. The 
Agency believes that a timely facility response after the onset of an 
accidental release will likely limit the amount that could volatilize 
for substances with vapor pressures lower than 10 mm Hg, thereby 
reducing the potential public or off-site impact. The Agency believes 
that a greater amount of substances with vapor pressures above 10 mm Hg 
is likely to be volatilized and released, even after a timely facility 
response occurs, potentially causing off-site impacts. The Agency also 
reviewed accident history and production volume information on the 
substances that would be delisted at this vapor pressure. This review 
has led the Agency to conclude that the accident histories or 
production volumes associated with the delisted substances do not 
warrant their listing under this rulemaking at this time. The Agency 
believes that this revised vapor pressure criterion focuses the list on 
chemicals that present a greater potential for accidental release than 
would a list using a 0.5 mm Hg criterion.
    The new vapor pressure criterion will drop from the list some 
chemicals that may have a lower likelihood of accidental release to 
air. Using the new vapor pressure criterion, the following 18 chemicals 
proposed for listing (shown with their CAS Registry numbers) will not 
be included in the list promulgated today:

Acetone cyanohydrin (75-86-5)
Aniline (62-53-3)
Antimony pentafluoride (7783-70-2)
Benzal chloride (98-87-3)
Benzenamine, 3-(trifluoromethyl)- (98-16-8)
Benzotrichloride (98-07-7)
Benzyl chloride (100-44-7)
Benzyl cyanide (140-29-4)
Chloroethanol (107-07-3)
Dichloroethyl ether (111-44-4)
Dimethyl phosphorochloridothioate (2524-03-0)
Formaldehyde cyanohydrin (107-16-4)
Hydrogen peroxide (concentration > 52%) (7722-84-1)
Lactonitrile (78-97-7)
Pyridine, 2-methyl-5-vinyl- (140-76-1)
Thiophenol (108-98-5)
Trans-1,4-dichlorobutene (110-57-6)
Trichloroethylsilane (115-21-9)

    EPA will be reevaluating the list periodically and as a result of 
petitions. If additional information is submitted on the accident 
history or production volume of these substances, EPA may list these 
substances at a later time. In addition, these substances, as well as 
any other extremely hazardous substance, are subject to the section 
112(r) general duty clause.
    Accident History: The Agency disagrees with several commenters who 
claimed that the Agency lacked authority to list substances based on 
accident history. The accident history associated with the use of a 
substance, in combination with toxicity, physical/chemical properties, 
and production volume considerations, is a permissible basis for the 
Administrator to list substances under section 112(r). Data from 
recorded accidents relate to each of the factors identified in section 
112(r)(4). Such data can provide information on the severity of impacts 
when impacts occur, as well as on the likelihood and magnitude of 
exposure. Substances that ``are known to cause * * * death, injury, or 
serious adverse effects on human health or the environment'' may be 
included on the list under section 112(r)(3). It would be a strained 
reading of the statute to say the Administrator must ignore documented 
accidental releases of substances in deciding which chemicals shall be 
the focus of the accidental release prevention program.
    The listing criteria established for toxic substances considers not 
only acute toxicity, but also physical/chemical properties (physical 
state, vapor pressure), and accident history. Several commenters argued 
that in analyzing accident histories EPA should not consider: (1) 
Transportation accidents; (2) accidents not involving death and/or 
injuries; (3) accidents involving fires and explosions; (4) accidents 
involving reactions with other chemicals; and (5) accidents involving 
elevated temperatures and pressures. The Agency disagrees with these 
comments. Accident history may indicate, beyond vapor pressure or other 
physical/chemical properties, unique qualities or circumstances that 
warrant accident prevention efforts. Evidence from transportation 
accidents may indicate the potential for airborne releases. For 
example, chemicals may be supplied in containers, such as tank cars, 
holding the chemical in similar conditions to storage conditions at 
stationary source. A failure of a container while in transit may 
indicate the potential for release while at a fixed location, since it 
may be stored under similar conditions. Quantities of chemicals are 
also commonly held at facilities for some period of time in trucks, 
tank cars, and other shipping containers. Accidents that did not result 
in off-site deaths or injuries may still indicate the serious potential 
for off-site impacts; e.g., evacuations may indicate that there was 
concern that people could suffer adverse effects from exposure. 
Furthermore, other effects, such as environmental damage, are 
appropriate to consider as well. While the factors to be considered 
under section 112(r)(4) do not specifically direct EPA to consider 
environmental effects, section 112(r)(3) directs the Administrator to 
consider ``substances which pose the greatest risk of causing * * * 
serious adverse effects to * * * the environment from accidental 
releases''. As noted at several points in this preamble, EPA believes 
that its decision to consider reported accidental releases involving 
fire and explosions as events of concern is supported by both the 
statute and legislative history. See also 136 Congressional Record 
S16992 (daily ed., Oct. 27, 1990) (statement of Senator Reid addressing 
the explosion in Henderson, Nevada); 136 Congressional Record H12931 
(daily ed., Oct. 26, 1990) (statement of Representative Barton 
addressing releases from burning material); H.R. Conf. Rep. No. 952, 
101st Congress, 2nd sess., 340 (1990) (Board to investigate fires and 
explosions). It may also be appropriate to consider chemical reactions 
with common materials such as water; e.g., it may be important to 
consider whether the reaction of an acid with water, producing heat, 
could lead to formation of an acid vapor or mist (the Bhopal accident 
involved a reaction of methyl isocyanate with water, generating heat). 
Accidents resulting from conditions of elevated temperatures and 
pressures in chemical processes may provide important information 
regarding the potential for accidental releases having an effect off-
site.
    The legislative history of section 112(r) contains extensive 
discussion of historical accidents and accident history data to support 
the need for enacting section 112(r) and the particular provisions 
included in the legislation. See 136 Congressional Record H12940 (daily 
ed., Oct. 26, 1990) (statement of Representative Richardson); 136 
Congressional Record S16921, S16925-26 (daily ed., Oct. 27, 1990) 
(statement of Senator Durenberger); 136 Congressional Record S16979 
(daily ed., Oct. 27, 1990) (statement of Senator Baucus). Incidents 
such as the explosion in Henderson, Nevada and the releases documented 
in the Acute Hazardous Events database, as well as statistics 
concerning the number of releases and evacuations were seen as 
demonstrating the need for an accident prevention program. See H.R. 
Rep. No. 490, 101st Congress, 2nd sess., 154-157 (1990); Senate Report 
at 211-221. The Agency will continue to consider accident history, in 
conjunction with acute toxicity and vapor pressure, to determine which 
substances need to be listed under section 112(r), and will consider 
these same elements in any revisions to the list promulgated today. 
When determining whether to list a substance based on its accident 
history, the Agency will analyze and explain the relevance of the 
accident history to the potential for a stationary source to 
accidentally release the substance.
    b. Specific substances. Sulfuric acid, phenol, parathion, and 
nitrobenzene, proposed to be listed because of accident history, were 
the focus of a number of comments. As stated above, the Agency believes 
that accident history, as well as toxicity, physical/chemical 
properties, and current commercial production volume, are all 
appropriate elements to be considered in determining the substances to 
be listed. The Agency reserves the flexibility to consider the listed 
substances in light of a combination of, or all of these criteria 
elements. Accident history was targeted by several commenters as not 
being a valid criteria to use in listing these substances. As discussed 
above, the Agency disagrees. The Agency has listed substances that meet 
two or three elements of the criteria only; e.g., there are acutely 
toxic substances listed that meet the high vapor pressure 
considerations but have no accident history associated with them. By 
the same token, the Agency also believes that commercially produced 
substances that meet the acute toxicity criterion and have an accident 
history, still could present a high potential for an impact beyond the 
fenceline even though they do not meet the vapor pressure 
consideration.
    A number of commenters objected to the inclusion of sulfuric acid 
on the list of substances, noting that because of its high boiling 
point and low vapor pressure under ambient conditions, it is unlikely 
to become airborne in a release. EPA recognizes that sulfuric acid does 
not meet the vapor pressure criterion. EPA originally proposed for 
listing sulfuric acid because of its toxicity, high production volume, 
and because it has been involved in a number of accidental releases 
with reported migration of a vapor cloud off-site; some of these 
incidents also resulted in worker deaths and injuries on-site. Several 
commenters indicated that the accidents cited by EPA did not provide a 
valid basis for listing for a number of reasons. First, some of the 
accidents, according to commenters, actually involved fuming sulfuric 
acid (oleum), which is a mixture of sulfuric acid and sulfur trioxide, 
and vapor clouds reported from these accidents were attributable to 
sulfur trioxide rather than sulfuric acid. Second, commenters stated 
that the injuries in some accidents were caused by direct contact with 
sulfuric acid rather than inhalation of vapor. Third, according to some 
commenters, some accidents involved reactions of sulfuric acid with 
other substances. Finally, comments were received which indicated there 
have been no accidents involving vapor clouds of sulfuric acid that 
caused off-site deaths or injuries, and that, in fact, the low vapor 
pressure of sulfuric acid makes it impossible for an accidental release 
to have any effect beyond the fenceline.
    EPA is well aware that sulfuric acid has a low vapor pressure and 
is unlikely to be released into the air under ambient conditions. 
However, as noted above, EPA also believes that, exclusive of vapor 
pressure, accident history can provide a valid basis, in combination 
with toxicity and/or physical/chemical properties, for adding a 
substance to the list. The Agency also notes that nothing in the 
statute limits EPA to consider solely the effects of vapor inhalation 
as a consequence of a release. As noted above, the EHS toxicity 
criteria endorsed by the Senate are not limited to inhalation. 
Furthermore, death, injuries, and environmental impacts caused by 
direct contact are relevant to the risks posed by a chemical.
    While believing the EPA has the authority to list sulfuric acid if 
its accident history, in conjunction with its toxicity and significant 
production volume, warrants listing, the comments received by the 
Agency have created doubt about the accuracy of what has been reported 
as air releases of sulfuric acid. For purposes of today's rulemaking, 
the Agency has been unable to determine from accident history whether 
sulfuric acid has generated an air release that has caused impact off-
site. Because of the uncertainty associated with past reported 
accidental release information and the common confusion between oleum 
and sulfuric acid in such reporting, the Agency has decided not to list 
sulfuric acid at this time. Although sulfuric acid is not specifically 
listed, facilities handling sulfuric acid are still subject to general 
duty requirements. The Agency will continue to monitor and review 
sulfuric acid accident reports to determine the need for listing at a 
future time. EPA also seeks data on the off-site impacts of sulfuric 
acid that could be used to evaluate whether sulfuric acid should be 
added to the list.
    Related to the sulfuric acid issue are comments suggesting that the 
Agency specifically list oleum (fuming sulfuric acid), CAS number 8014-
95-7. Oleum is a mixture of sulfuric acid and sulfur trioxide. In the 
proposed rule, the Agency believed oleum would be subject to section 
112(r) requirements because both of its components, sulfuric acid and 
sulfur trioxide, were proposed for listing, and because of the Agency's 
proposed de-minimis concentration for mixtures. However, two commenters 
noted that it is ``reasonable to include oleum as a regulated 
chemical'' and that ``oleum and sulfuric acid must be listed 
separately, since the fuming effects of an oleum release make it 
potentially much more serious.'' The Agency agrees with commenters that 
oleum should be included in this listing because of its accident 
history, toxicity, and production volume. Furthermore, the Agency has 
reviewed the accident history data relevant to oleum and sulfuric acid 
and agrees with commenters that some of the accidents the Agency had 
relied on to list sulfuric acid in fact involved oleum. Furthermore, 
because of the revisions on the de-minimis concentration provisions and 
the Agency's decision not to finalize the listing of sulfuric acid at 
this time, oleum would no longer be subject to 112(r) provisions 
without a specific listing. In order to continue the coverage of oleum 
in the accidental release prevention provisions, EPA is specifically 
listing all forms of oleum in the section 112(r) list of substances.
    Phenol (in liquid form only), parathion, and nitrobenzene are also 
included on the proposed list based on accident history. Several 
commenters objected to the inclusion of these chemicals, for reasons 
similar to those concerning the listing of sulfuric acid, i.e., the low 
vapor pressure of these substances and the lack of sufficient 
supporting accident history to provide a basis for listing. The Agency 
generally agrees with the comments regarding these three specific 
substances. Having considered the comments and having conducted further 
review of accident history for these chemicals, the record indicates 
that there are not a clearly significant number of accident reports 
with effects, or potential effects, beyond the fenceline to merit 
listing at this time.
    Several commenters objected to the listing of other specific 
substances for a variety of reasons, including low vapor pressure, low 
toxicity, existing safety regulations, and accident history. The 
chemicals mentioned include hydrogen peroxide, acrylonitrile, and 
hydrochloric acid, among others. EPA has reviewed the comments on these 
chemicals and categories of chemicals that were recommended for 
deletion and has decided to, except as noted, retain them on the list 
of regulated substances under section 112(r). As noted above, EPA is 
revising the vapor pressure criterion and not proceeding to list 18 
chemicals with vapor pressures below 10 mm Hg. In addition, the Agency 
has determined that section 112(r)(3) prohibits it from listing methyl 
bromide because the substance has been listed by regulation as an ozone 
depleting chemical under CAA Title VI (see 58 FR 65018, December 10, 
1993).
    The Agency disagrees with commenters that seek deleting substances 
because of other existing regulations. The listing of substances and 
thresholds, as mandated by Congress, reflects the potential for these 
listed substances to cause serious adverse effects to human health or 
the environment. The Agency believes that considerations of other 
regulations applicable to these regulated substances are appropriately 
accounted for in accident prevention requirements developed for 
facilities handling the regulated substances above the threshold 
quantities, rather than in determining whether any listed substance 
poses a potential hazard.
    Several commenters recommended the deletion of substances that were 
mandated for listing by Congress, including ammonia, toluene 
diisocyanate, and anhydrous sulfur dioxide. The Agency believes that 
the language of section 112(r)(3) precludes it from omitting these 
chemicals from the initial list. The Agency will consider petitions to 
delist these chemicals if such petitions comply with the petition 
criteria announced today.
    Several commenters recommended adding other specific substances, 
such as chlordane and tetraethyl lead, to the list of regulated 
substances. The Agency will consider these at the time it revises the 
list promulgated today, or through the petition process. However, the 
Agency notes that notwithstanding today's listing, these substances are 
still subject to the general duty provisions, particularly if they are 
in commercial production and use.
    In the list rule proposal, EPA requested information to determine 
the need and appropriateness of including radionuclides under this 
rulemaking. Some commenters objected to including radionuclides while 
others recommended inclusion. Still other commenters recommended the 
inclusion of only some radionuclides. However, none of the commenters 
provided sufficient technical information to assist the Agency in 
determining whether or not radionuclides should be listed. Due to the 
uncertainty associated with gaps in EPA's data and the appropriate 
criteria for listing, the Agency has decided not to include 
radionuclides in the initial list of regulated substances.
    c. Other list options considered. EPA considered the option of 
adopting the entire list of 360 toxic chemicals regulated under EPCRA 
(SARA Title III) section 302. A small number of commenters favored this 
option, believing that consistency with EPCRA is desirable, that having 
a single list would help avoid confusion, and that listing additional 
toxic substances would be more protective of the public. EPA did not 
propose to adopt the entire EHS list because it includes a number of 
solids and non-volatile liquids for which an effect beyond the 
fenceline in the event of an accidental release is expected to be less 
likely than for gaseous or volatile liquids. It also includes 
substances that are not currently in commercial production. Congress 
did not direct EPA to list all EHS substances. Instead, Congress 
provided that the Administrator could include as few as 100 substances 
on the initial list under section 112(r). In directing the 
Administrator to ``use'' the EHS list, but not to be ``limited to'' 
this list, and in providing that ``such modifications as * * * 
appropriate'' be made, the CAA provides the Agency with the flexibility 
to cull from the EHS list and other sources a more focused list of 
substances for accidental release prevention regulations. Most 
commenters supported EPA's decision to propose for listing only those 
EHSs that best reflect the statutory criteria of likelihood and 
magnitude of release. For these reasons, EPA is not adopting the entire 
EHS list.
    d. Threshold quantities. EPA's proposed thresholds were lower than 
OSHA's for 15 of the substances listed by both OSHA and EPA. A number 
of commenters stated that EPA's thresholds should not be lower than 
OSHA's for any listed substances, since in general, workers face a more 
immediate threat of exposure in an accidental release than would the 
public. Several commenters indicated that EPA should adopt the OSHA 
thresholds for chemicals which EPA had assigned lower thresholds. 
Conversely, there were other comments supporting the lower thresholds 
proposed by EPA for several chemicals, based on the commenters' 
experience with these chemicals.
    EPA has reviewed the threshold quantities for the listed substances 
and the OSHA thresholds for the substances on both the EPA and OSHA 
lists prior to and after the proposal of EPA's rule. EPA recognizes the 
practical importance of consistency with the OSHA list to the extent 
possible, but also believes it is necessary to have a sound methodology 
for assignment of threshold quantities; the CAA requires the Agency to 
include an explanation of the basis for establishing the list, and to 
account for specified factors in setting threshold quantities. OSHA's 
thresholds were not required to reflect the factors EPA must consider. 
The statute also provides for petitions to add new chemicals, and 
requires the development of thresholds for such chemicals when listed. 
A sound methodology is essential for making changes to the list and 
thresholds after promulgation. The methodology adopted today considers 
the factors required by the CAA under section 112(r)(5). No other 
methodology was identified that EPA could use to derive thresholds that 
would be consistent and equally applicable to the current listed 
substances and to those that may be added in the future. Therefore, EPA 
is not adopting the OSHA thresholds.
    Nevertheless, EPA agrees with commenters that EPA should review its 
proposed threshold methodology and quantity categories to ensure that 
they accurately reflect the range of risks posed by the listed toxic 
substances. Based on this review, EPA has decided to retain its 
threshold methodology but revise the range of threshold quantities for 
toxics. The minimum quantity remains at 500 pounds, representative of 
drum-size containers, but the maximum threshold quantity is raised to 
20,000 pounds, replacing the proposed 10,000 pound maximum. This higher 
upper limit expands the range of threshold quantities to better reflect 
the relative hazards among the listed toxics; the upper limit of 20,000 
represents typical handling quantities, and would still be protective 
of the public for those substances which now have the higher 
thresholds. Threshold quantity categories for toxic substances are now: 
500 pounds, 1,000 pounds, 2,500 pounds, 5,000 pounds, 10,000 pounds, 
15,000 pounds, and 20,000 pounds.
    Using this revised range, higher thresholds have been assigned for 
most of the toxic substances listed based on the revised vapor pressure 
criterion. Several toxic substances also meet the flammability 
criteria, and thus could be assigned two thresholds. Toxic substances 
that also meet the criteria for listing as flammable substances are 
assigned the lower of the thresholds. Under the revised methodology, 
the only substance that has a threshold quantity that is lower under 
EPA than OSHA's PSM standard is methyl chloride, which meets the 
criteria for listing for flammability and, therefore, is assigned a 
threshold quantity of 10,000 pounds, rather than the 20,000 pounds that 
would apply under the methodology for toxics. The OSHA threshold for 
methyl chloride is 15,000 pounds. This is to account for those hazards 
presented by the substance that are considered in this rulemaking; the 
lowest threshold quantity is assigned to be more protective.
    A number of commenters suggested that site-specific factors should 
be considered in setting or modifying thresholds, such as population 
density, ecosystem sensitivity, safety devices, experience, uses of the 
substance, and handling conditions. EPA recognizes that these and many 
other site-specific factors could affect the likelihood of occurrence 
or the effects of a release. Accounting for these factors has the 
advantage of more specifically tailoring threshold quantities based on 
common use patterns of the substances and on the particular site in 
which they would be used. One serious disadvantage of applying site-
specific factors to setting thresholds would be that such an approach 
would be inappropriate for ubiquitous chemicals, such as chlorine and 
ammonia, because of the innumerable applications that would have to be 
considered. A greater disadvantage to this approach is that the 
intrinsic hazard of a chemical will still be present even when it is 
used outside of a ``typical'' scenario. As stated in the proposed rule, 
EPA believes it is not feasible to develop a methodology for 
establishing threshold quantities based on site-specific factors that 
would be applicable uniformly nationwide. Therefore, EPA did not 
incorporate site-specific factors in setting or modifying thresholds. 
As discussed in the preamble section IV.B. Threshold Determination, 
substance-specific factors and use scenarios are considered in 
determining whether there is a threshold quantity on-site. Also, site 
specific factors will more appropriately be accounted for in the 
accidental release prevention regulations under section 112(r)(7). This 
Agency rationale is also applicable to similar comments for 
establishing thresholds for flammable and explosive substances.
    e. Other threshold quantity options considered. In addition to the 
proposed methodology for setting thresholds for toxic substances and 
the use of OSHA thresholds as discussed above, EPA requested comment on 
several other options. One option was use of the vapor quantity method, 
based on air dispersion modeling, to determine the quantity in air 
needed to equal the ``Immediately Dangerous to Life and Health'' (IDLH, 
published by the National Institute for Occupational Safety and Health) 
concentration level at 100 meters from the point of release. This 
option was not generally supported by commenters. A second option was 
to adopt the threshold planning quantities (TPQs) under EPCRA section 
302. A small number of commenters favored this option, believing that 
consistency with EPCRA would help to avoid confusion. EPA did not 
propose this option because the TPQs are intended to represent a level 
at which the chemical hazards should be considered by localities for 
discretionary community planning purposes. As mentioned in the preamble 
of the proposed rule, the thresholds established under this rule have a 
different purpose, i.e., to indicate which facilities must comply with 
mandatory facility-based prevention requirements. Any confusion that 
results from two different threshold quantities applying to the same 
chemical under two EPA emergency preparedness and prevention programs 
is mitigated by the fact that the more onerous and detailed planning 
requirements are triggered when greater, and presumably more dangerous, 
quantities are present.
    The third threshold option considered for toxics was adoption of 
the OSHA thresholds for all substances listed by both EPA and OSHA. A 
number of commenters favored this option. As noted above, EPA 
recognizes the importance of consistency with OSHA. However, because of 
EPA's statutory obligation to establish a methodology based on 
specified factors, the Agency has elected not to adopt the OSHA 
thresholds. The thresholds adopted in today's rule for chemicals listed 
by EPA are, with the exception of methyl chloride, equal to or higher 
than OSHA's.
2. Flammable Substances
    EPA's listing of flammable gases and volatile flammable liquids was 
generally supported by commenters, although a few commenters maintained 
that, because OSHA regulates flammable substances, EPA should not list 
them. The Agency disagrees that flammable substances should not be 
listed for accident prevention and potential effects off-site, since 
such substances pose a potential off-site hazard (namely, a vapor cloud 
explosion) because of their inherent properties. The proposed threshold 
for flammables, 10,000 pounds, was generally supported as well. EPA is 
finalizing the proposed listing for flammables and their threshold 
quantities.
    Commenters also focused on specific flammable substances, including 
methane, ethane, propane, and butane (some components of natural gas). 
Commenters argued that special factors (e.g., the low density of 
methane gas) justify not listing or modifying the listing of these 
substances. EPA has reviewed the comments on specific flammable 
substances and disagrees with the commenters. EPA believes there is 
sufficient information, from both accident reports and modeling 
results, to support the conclusion that flammable substances that meet 
the listing criteria, in quantities above the threshold quantity of 
10,000 pounds, could present a hazard to the public from a vapor cloud 
explosion. EPA recognizes that, as noted by commenters, some situations 
in which these substances are handled may present a lesser hazard than 
others. However, these substances still pose a potential threat beyond 
the fenceline in case of an accidental release. Therefore, in order to 
be protective of the public, EPA is maintaining the same application of 
the criteria for flammable substances as proposed for all listed 
flammable substances. EPA's listing decision is based on the 
substances' demonstrated or potential effects in the event of an 
accidental release, not on existing regulations, standards, or 
recommended practices applicable to the listed substances; these 
factors may more appropriately be accounted for when accident 
prevention regulations are promulgated under section 112(r)(7).
    Several commenters recommended that EPA provide an exemption, 
similar to the exemption under OSHA's PSM Standard, for flammable 
liquids kept in atmospheric tanks below their normal boiling points. 
Unlike OSHA, EPA is listing only flammable gases and volatile flammable 
liquids. EPA considers these substances to be intrinsically hazardous, 
regardless of conditions of storage, and, therefore, does not believe 
it is appropriate to provide an exemption for atmospheric storage.
3. Explosives
    Explosives classified by DOT as Class 1, Division 1.1 and listed as 
such in 49 CFR 172.101 (the Hazardous Materials Table) are covered by 
this rule with a threshold of 5,000 pounds. In 49 CFR 173.50, DOT 
defines the term ``explosive'' as any substance or article, including a 
device, which is designed to function by explosion (i.e., an extremely 
rapid release of gas and heat) or which, by chemical reaction within 
itself, is able to function in a similar manner even if not designed to 
function by explosion, unless the substance or article is otherwise 
classed under DOT provisions. Division 1.1 consists of explosives with 
a mass explosion hazard; a mass explosion is one which affects almost 
the entire load instantaneously. The Agency proposed to list all 
substances that met the definition of Division 1.1 (58 FR 5110). The 
Agency is clarifying and modifying its listing of explosive substances 
to include only those substances listed in 49 CFR 172.101 (DOT's 
Hazardous Material Table), which is a subset of all substances and 
mixtures of substances that would meet DOT's Division 1.1 definition.
    EPA noted in the preamble to the proposed rule that it believed 
this threshold would apply primarily to manufacturers of high 
explosives (58 FR 5112). More than 100 commenters, primarily explosives 
distributors and users, objected to the listing of explosives in 
general. These commenters maintained that explosives are regulated 
adequately by a number of agencies, including the Bureau of Alcohol, 
Tobacco, and Firearms (BATF), DOT, OSHA, the Mine Safety and Health 
Administration (MSHA), and the Department of Defense (DOD). The 
commenters believe the requirements of the existing regulations serve 
to prevent accidents and cited the safety record of the explosives 
industry as evidence. The commenters believe the American Table of 
Distances, used by BATF to set distances for storage of explosives, 
provides protection for the community from the effects of an accidental 
explosion; this table is based on a lower overpressure level than the 
3.0 psi used by EPA to set the threshold for explosives and, therefore, 
is more protective of the public. In addition, a number of commenters 
said the 5,000-pound threshold proposed by EPA would not restrict the 
effects of the rule to manufacturers, as suggested by EPA, but would 
also cover many distribution and use sites. They noted that, for 
example, blasting may require only a small quantity of high explosive 
(Division 1.1), but that the entire quantity of explosives on-site used 
in blasting is treated as a high explosive; the high explosive portion 
serves to initiate the reaction involving the entire quantity.
    EPA acknowledged in the proposed rule that explosives are already 
regulated by a number of agencies. However, these existing regulations 
do not negate the properties of these substances. The explosives listed 
in today's rule meet the criteria of section 112(r) (3) and (4) because 
the inherent properties of the listed explosives plainly indicate that 
such chemicals may have a severe impact in the event of a detonation. 
The listed explosives represent the category of explosives that may 
most easily detonate. In the event of an accidental detonation these 
substances pose an inherent risk of off-site effects. Industry 
requirements under other applicable regulations, or recommended 
standards, are more appropriately accounted for in the development of 
accidental release prevention requirements. The requirements for 
accident prevention in section 112(r)(7) specifically allow for 
recognition of industry-specific circumstances, including voluntary 
prevention measures, in EPA's prevention regulations. No similar 
provision is set forth in sections 112(r) (3), (4), or (5), which 
covers the development of this list of substances and thresholds 
quantities. Section 112(r)(7) implementing rules, as appropriate, will 
allow for industry specific circumstances to be considered. Other 
regulatory requirements, and other practices already in place aimed 
specifically at protecting the public from adverse effects in case of 
accidental releases are expected to be integrated with accident 
prevention requirements of rulemaking under section 112(r)(7).
    In particular, EPA's review of existing regulations indicates that 
public safety would be enhanced if additional information about 
explosives, such as hazards assessments, were available to emergency 
response agencies and local emergency planners. Public safety would 
also be enhanced if there were additional coordination between 
facilities handling explosives and the local emergency planners and 
responders. The listing of explosives will make information available 
under section 112(r) rulemaking and facilitate this coordination. 
Furthermore, current regulations do not provide for public 
communication of potential off-site hazards, as do CAA Amendments 
requirements under section 112(r)(7). Currently, only information 
related to the quantity and location of explosives is available to the 
public under sections 311 and 312 of EPCRA. Under the risk management 
provisions of the CAA, the public will also have available to them 
information about the measures being taken by the facility to prevent 
off-site consequences from accidental detonations.
    The Agency has noted that the practice of treating the entire 
quantity of mixtures of high explosives with other explosives as high 
explosives, coupled with the Agency's proposed threshold determination 
rule for mixtures, creates the potential for coverage of explosive 
formulations that are intended to be released (exploded) on-site. The 
Agency did not intend such coverage in its proposal. In response to 
this problem identified by the commenters, the Agency is modifying the 
listing of explosives in today's final rule so that specific explosives 
on the Hazardous Materials Table are identified as the regulated 
substances. This avoids the potential circularity in the proposed 
definition. Mixtures with substances listed on the Hazardous Materials 
Table are potentially covered only through the operation of the 
explosive mixture provision in the threshold determination portion of 
today's rule. The Agency is also clarifying the coverage of explosive 
mixtures to be used for intentional on-site detonations (not an 
accidental release) when determining if a threshold quantity is present 
in a process. This clarification is discussed later in today's 
preamble.

B. Threshold Determination

    Section 68.115 was originally proposed as section 68.5. It has been 
consolidated with other subpart C provisions that relate to covered 
substances and applicable thresholds. This section of the regulation 
establishes how to estimate the presence of a threshold quantity. 
Exemptions of those quantities that need not be accounted for in 
determining a threshold are also included.
1. Basis for Threshold Determination
    Comments on the proposed rule generally supported a threshold 
quantity determination that is based on the quantity of a regulated 
substance in a process. Some commenters, however, suggested that 
determining threshold quantities should be based on the quantity on-
site, the average annual usage, or on-site specific factors. EPA 
generally disagrees with these statements. The total quantity on-site, 
while consistent with other regulations in determining threshold 
quantities (particularly EPCRA, section 302) does not necessarily 
represent the quantity that could be involved in an accident. The total 
quantity on-site may include quantities in separate processes, 
buildings, and locations within the same facility. The average annual 
usage measures the quantity used by a facility in a year and is not 
related to the maximum quantity that could be released at a given time. 
Site-specific factors are appropriately accounted for both in defining 
the process for which a threshold calculation must be undertaken and in 
assessing the hazards and preparing the risk management plan for the 
particular facility. As recommended by most commenters, EPA is 
retaining the threshold determination based on the total quantity in a 
process, using the same process definition as OSHA. This approach 
focuses on the quantity of a substance that might be released in a 
single accident, and that could be reasonably anticipated to cause 
effects of concern as a result of an accidental release. This threshold 
determination approach is consistent with OSHA's PSM standard.
2. Mixture Exemption
    a. Toxic substances. The proposed rule included a de-minimis 
concentration of one percent by weight for all listed substances 
present in a mixture; i.e., quantities of a regulated substance in a 
mixture did not have to be accounted for purposes of the threshold 
quantity if the substance were present at concentrations below one 
percent by weight. A number of comments were received on this exemption 
for solutions and mixtures.
    Several commenters suggested providing a threshold determination 
method for mixtures based on the SHI. The partial pressure of the 
listed substance in solution and its toxicity would be used to 
determine the value of the SHI for the solution; the index value would 
be compared to a cut-off value (commenters recommended a cut-off of 
1,000). EPA does not agree that the SHI criteria should be used to 
determine the mixture cut-off. Because the SHI approach was not used in 
determining which chemicals to list, a mixtures score based on this 
index would not relate to whether a chemical met the listing criteria. 
EPA also remains concerned about the lack of a basis for the 
recommended 1,000 SHI cut-off. In addition, EPA believes the SHI 
approach would be difficult to implement within the structure of 
section 112(r), especially for facilities outside the chemical 
manufacturing industry.
    Most of the commenters believed the one percent concentration cut-
off is too low for solutions of toxic substances; their position being 
that one percent mixtures of a regulated substance pose essentially no 
threat to the public. Several commenters also suggested that EPA should 
provide specific concentration cut-offs for solutions of certain listed 
substances, such as hydrogen fluoride, nitric acid, and sulfuric acid. 
Several commenters suggested that the concentration cut-offs should be 
raised for hydrochloric acid (listed for concentrations of 25 percent 
or greater) and ammonia (listed for concentrations of 20 percent or 
greater).
    The Agency agrees with commenters that the one percent cut-off may 
prove to be too conservative in certain circumstances, and that it may 
not adequately reflect the decreased potential for air release of most 
regulated substances in dilute mixtures or solutions; at very low 
concentrations some of these mixtures or solutions fail to meet the 
listing criteria. The Agency also believes, however, that no 
justification would exist to exclude the quantities in mixtures or 
solutions from the threshold calculation if it is uncertain that these 
mixtures or solutions fail to meet the original listing criteria.
    In response to these comments, EPA has modified the one percent 
mixture exemption to reflect the amount of the regulated substance that 
may reasonably be anticipated to cause an effect of concern in an 
accidental release. The Agency has reassessed the concentration at 
which certain dilute solutions of regulated substances may pose a 
hazard to the community, sufficient to warrant treatment as a regulated 
substance, for purposes of determining whether a threshold quantity is 
present in a process. As part of this modification, EPA has decided to 
provide specific cut-off concentrations for certain chemicals. These 
chemicals, in mixtures or solutions with concentrations below the 
specified cut-off, will not have to be considered in determining 
whether a threshold quantity is present. For other chemicals, a method, 
rather than a specific cut-off, will be provided to determine whether 
mixtures should be considered in the threshold determination. The 
following chemicals are now listed with concentration cut-offs (in 
addition to those already proposed with concentrations cut-offs) as 
shown for weight percent of the substances in water solution:
     Hydrogen fluoride/Hydrofluoric acid (concentration 50 
percent or greater); the listing of hydrogen fluoride has been 
clarified to reflect that it includes the aqueous form of hydrogen 
fluoride, hydrofluoric acid.
     Nitric acid (concentration 80 percent or greater).
    The concentration limits for hydrofluoric and nitric acid are based 
on the partial pressures of these substances in water solution. At the 
concentrations listed, the partial pressures of the solutions would 
meet the vapor pressure criterion of 10 mm Hg. Also, EPA is raising the 
proposed concentration cut-off for hydrochloric acid from 25 to 30 
percent, based on water solutions, to meet the revised vapor pressure 
criterion. EPA is not changing the concentration cut-off for ammonia 
because the partial pressure of ammonia in a 20-percent solution still 
exceeds the 10 mm Hg vapor pressure criterion.
    Other listed toxic substances in solutions or mixtures must be 
included in threshold determination if the partial pressure of the 
substance in the solution or mixture is equal to, or exceeds, 10 mm Hg. 
If the partial pressure of the regulated toxic substance in the mixture 
is determined to be below 10 mm Hg under all conditions in process 
handling or process storage, the solution or mixture need not be 
considered in the threshold determination. If the partial pressure of 
the regulated toxic substance in the mixture equals or exceeds 10 mm Hg 
in portions of the process, then the quantity of the listed substance 
contained in the mixture at these portions of the process shall be 
included in determining whether a threshold is met. The facility will 
be required to use the one percent de-minimis concentration in 
determining threshold quantities unless it can measure or estimate, and 
document, that the partial pressure of the regulated substance in the 
mixture or solution is less than 10 mm Hg.
    The methodology for determining the amount of a regulated substance 
in a mixture to apply to thresholds does not apply to oleum, toluene 
2,4-diisocyanate, toluene 2,6-diisocyanate, and toluene diisocyanate 
(unspecified isomer). These substances have vapor pressures less than 
10 mm Hg.
    b. Flammable substances. The proposed rule included the same de-
minimis concentration of one percent by weight for all listed 
substances present in a mixture for flammable substances. A number of 
commenters noted that mixtures of flammable substances in 
concentrations above one percent may not be flammable. They suggested 
that a listed flammable substance in a mixture should be included in 
threshold determination only if the mixture meets the flammability 
criteria for listing. Other commenters suggested that the entire 
mixture containing a listed substance should be treated as a regulated 
substance if the mixture meets the listing criteria for flammable 
substances. EPA agrees that a mixture containing a listed flammable 
substance should only be considered in a threshold determination if the 
mixture itself meets the criteria for an NFPA flammability rating of 4, 
i.e., flash point below 22.8 deg. C (73 deg. F) and boiling point below 
37.8 deg. C (100 deg. F). Again, as for the toxics in mixtures or 
solutions, a facility is required to use the one percent de-minimis 
concentration for threshold quantity calculations unless it can measure 
or estimate, and document, that the mixture or solution does not have a 
flash point below 22.8 deg. C (73 deg. F) and a boiling point below 
37.8 deg. C (100 deg. F).
    The Agency agrees with commenters who suggested that a mixture 
containing a flammable regulated substance should be treated as the 
regulated substance for purposes of determining whether a threshold 
quantity is present if the mixture itself meets the boiling point and 
flash point criteria of today's rule. EPA believes the hazards 
associated with such highly flammable mixtures make it appropriate to 
treat such mixtures as regulated substances when such mixtures meet the 
flammability listing criteria. EPA recognizes that counting the entire 
quantity of a flammable mixture for threshold determination differs 
from the proposed rule and from the treatment of mixtures containing 
regulated toxic substances. However, the Agency believes this different 
treatment is appropriate because, for flammable substance mixtures, the 
mixture is known to display the flammability hazard at levels that meet 
the listing criteria, while for toxic substance mixtures, the mixture 
is not known to meet the acute toxicity criterion. For toxic substance 
mixtures, EPA requires counting towards a threshold only the portion of 
the mixture that would meet the acute toxicity criterion (i.e., the 
amount of the actual substance).
    c. Explosive substances. A number of comments were received 
regarding the threshold calculations for explosives, particularly for 
mixtures of division 1.1 explosives with low explosives or blasting 
agents at use sites. In the proposed rule, the Agency had established a 
de-minimis concentration applicable to all listed substances. 
Commenters pointed out problems with this mixture consideration, in 
light of EPA's listing of all explosives meeting DOT's definition of 
Division 1.1 hazardous materials. This definition treats the entire 
quantity of a mixture containing a high explosive as a Division 1.1 
explosive, hence negating the de-minimis calculation for purposes of 
threshold quantity determinations. This affected particularly those 
mixtures formulated on-site, prior to intentional detonations, 
following BATF regulations. To minimize the potential for accidents, 
these mixtures generally are made shortly before intentional on-site 
explosions. The Agency recognizes that the intentional release (or 
controlled release) in an explosion of mixtures containing a regulated 
substance is not an accidental release. Thus, the Agency believes that 
the amount of an explosive in such a mixture cannot be reasonably 
anticipated to cause effects of concern as a result of an accidental 
release when such quantities are intended to be released on-site. 
Therefore, in addition to clarifying the listing of explosives only to 
include those substances listed by DOT in 49 CFR 172.101, the Agency is 
also clarifying the applicability of the mixture concentration 
provision for explosives. For purposes of determining whether a 
threshold quantity is present in a process involving explosives, 
mixtures of Division 1.1 explosives listed by DOT in 49 CFR 172.101 
(Hazardous Material Table) and other explosives need not to be included 
when the mixture is intended to be used in an on-site non-accidental 
release in a manner consistent with applicable BATF regulations. 
Quantities of explosive regulated substances in mixtures that are not 
intended to be used on-site in an intentional explosion would not be 
exempt if such mixture would be treated as a Division 1.1 explosive 
under 49 CFR parts 172 and 173.
    The following two examples demonstrate how this threshold 
determination provision would operate. An owner or operator of a 
stationary source receives a mixture, or prepares a mixture, that 
combines a small quantity of an explosive listed as Division 1.1 
hazardous material in 49 CFR 172.101 with a large quantity of a 
blasting agent, so that the total quantity is above the 5,000 lbs 
threshold quantity established for listed explosives. If the owner or 
operator intends to detonate the high explosive/blasting agent mixture 
at the stationary source in a manner that is consistent with applicable 
BATF regulations, then the owner or operator need not count the weight 
of the mixture in determining whether the source has a threshold 
quantity of the regulated substance on-site. If the owner or operator 
intends to store, and then transport off-site the high explosive/
blasting agent mixture, and the entire mixture would be treated as 
Division 1.1 explosive under applicable DOT regulations, then the 
weight of the entire mixture would need to be calculated to determine 
whether a threshold quantity is present.
3. Other Threshold Exemptions
    Except as noted below, all other threshold exemptions in the 
proposed rule are retained in the final rule. All comments received 
concerning these exemptions favored the Agency's proposal. The Agency 
continues to believe that the forms of regulated substances exempted in 
today's rule cannot reasonably be anticipated to cause effects of 
concern in the event of an accidental release.
    Use for facility consumption as fuel: The Agency has deferred a 
decision on the proposed exemption for listed flammable substances when 
used solely for facility consumption as fuel. For a document relating 
to this proposed exemption, see a supplemental notice published 
elsewhere in this issue. The Agency intends to decide on whether to 
promulgate this exemption on or before the date the final risk 
management program rule is promulgated.

C. Petition Process

    Section 68.120 of the rule establishes the specific administrative 
and technical requirements for the submission of petitions to add or 
delete substances from the list of regulated substances.
    Several comments were received on the criteria for determining 
whether a substance that is the subject of a petition should be listed 
or delisted. Two commenters said the listing criteria are too narrow. 
For example, it was argued that EPA should allow petitioners to develop 
a case for listing toxic chemicals that do not meet the acute toxicity 
criteria. Another commenter said the listing criteria are too broad, 
and the standards for delisting are too stringent; delisting requires 
demonstrating that the substance ``will not'' cause death, injury, or 
environmental harm.
    EPA believes the acute toxicity criteria for listing toxics, as 
well as the volatility and accident history, provide a valid basis for 
identification of chemicals that pose hazards to the community in case 
of acute exposures resulting from an accidental release and is 
retaining these criteria for petition review. The Agency is also 
retaining the selection criteria for listing flammables and explosives. 
EPA agrees that the petition requirements for delisting may be too 
stringent and will delete substances from the list if it can be 
determined that the substance, in case of an accidental release, ``is 
not known or anticipated to'' cause death, injury, or serious adverse 
effects to human health or the environment.
    One commenter said the decision not to accept additional petitions 
unless new data become available should be modified so that petitions 
that present significant data not previously considered (whether or not 
the data are new) can be accepted. The petition process provides that 
when a petition is received, EPA will publish a notice in the Federal 
Register requesting additional, pertinent scientific information that 
was not identified by the petitioner. Interested parties will have the 
opportunity to present significant data not included in the petition. 
Therefore, EPA believes it is appropriate to accept additional 
petitions on a substance only if new data become available.
    Another commenter said the 18-month period proposed for review of 
petitions should be shortened to six months. EPA believes the 18-month 
review period is not excessive for carrying out a thorough review of 
the petition and any public comments and publishing a decision 
concerning the petition. Denials shall be published in the Federal 
Register within 18 months of the Agency receiving the petition; for 
petitions granted, the Agency will publish a proposed new listing 
within 18 months.

D. Definitions

    Section 68.3 of the regulation sets forth the definitions that will 
apply to all regulations published under section 112(r). Some of the 
terms used in other parts of the CAA are also applicable to section 
112(r). In addition, a number of terms new to the CAA, resulting from 
the implementation of section 112(r), are defined in section 68.3 for 
purposes of all accidental release prevention regulations. These 
definitions include terms necessary to communicate effectively the new 
regulatory requirements.
    Accidental Release: The definition proposed for accidental release 
has been taken directly from the legislative language. Several 
commenters, however, thought it appropriate that the Agency clarify 
this definition to better focus on EPA's intent through this 
regulation. Several commenters submitted that the definition of 
accidental release should be clarified not to include routine emissions 
to the environment. The Agency believes that the definition is clear in 
specifying that and accidental release is an ``unanticipated emission'' 
of a regulated substance and that this would not include routine 
emissions. Several commenters also had concerns regarding the inclusion 
of the term ``other extremely hazardous substances'' in the definition 
of accidental release. This term has also been taken directly from the 
legislative language and the Agency believes it to be an important 
component of this definition. Under section 112(r)(1) the owners and 
operators of stationary sources have a duty to initiate specific 
activities to prevent and mitigate accidental releases of any regulated 
substance under 112(r)(3), or any other extremely hazardous substance.
    Process: There were a number of comments related to EPA's 
definition of process. The proposed definition was consistent with 
OSHA's definition of process under their PSM standard, and included any 
activity involving a regulated substance including any use, storage, 
manufacturing, handling, or on-site movement of such substances, or 
combination of these activities. Any group of vessels that is 
interconnected, or separate vessels that are located such that a 
regulated substance could be involved in a potential release, were 
proposed to be considered a single process. Because of the need to 
maintain as much consistency as possible with OSHA, EPA is retaining 
this definition and is providing, in this preamble, some clarification 
prompted by comments submitted on this issue.
    Many commenters argued that the proposed definition included terms 
that were not clear, such as interconnected vessels and single 
processes. The commenters indicated, for example, that in some cases 
vessels may be connected in indirect ways and still present a low 
probability that they could be involved in a single release. The Agency 
believes that this was already accounted for through the proposed 
definition of process. To serve as clarification, interconnected 
vessels that could be involved in a single release would include 
vessels physically connected so that an event could lead to an 
accidental release involving all these vessels at one time. The Agency 
still believes that the facility is responsible in accounting for any 
quantity of a regulated substance that could potentially be released 
from one or more vessels, whether these are connected or not.
    Stationary source: Several commenters requested clarification 
regarding pipelines and whether listed flammable substances in pipeline 
transfer stations would be covered by the rule under the stationary 
source definition. Other commenters had questions regarding the 
inclusion in this definition of transportation containers not under 
active shipping orders. The Agency is clarifying the definition of 
stationary source. For purposes of regulations under section 112(r), 
the term stationary source does not apply to transportation conditions, 
which would include storage incident to such transportation, of any 
112(r) regulated substance. Pipelines, transfer stations, and other 
activities already covered under DOT as transportation of hazardous 
substances by pipeline, or incident to such transportation, under 49 
CFR parts 192, 193 and 195 would not be covered. Transportation 
containers that are not under active shipping papers are not considered 
by EPA to be storage incident to transportation; the Agency considers 
the definition of stationary source to include such containers.

E. Exemptions

    The Agency is retaining the proposed exemption from this part for 
ammonia used as an agricultural nutrient, when held by farmers. This 
exemption was authorized by statute, and it was also generally 
supported by commenters.
    A number of commenters suggested that an exemption should be added 
for natural gas, mainly because of other existing regulations. As 
discussed previously in this preamble, EPA's listing of a substance is 
based on the demonstrated or potential effects in the event of an 
accidental release. Existing regulations may be targeted to reduce a 
potential release, or the effects of a release, but do not negate the 
hazards presented by the substances regulated. Existing requirements 
under other regulations, standards, or recommended practices are to be 
accounted for though the requirements of the risk management program 
and any other prevention regulations under section 112(r).

F. Scope

    An issue of concern to a number of commenters were the general duty 
requirements under section 112(r)(1). Generally, commenters voiced some 
confusion regarding what the requirements would be, and particularly 
about which substances would be included. Because of similarities with 
OSHA's general duty clause, commenters expressed the need for EPA to 
develop guidance along the OSHA Field Operations Manual to assist 
facilities in evaluating their compliance with these requirements.
    The CAA identified the following activities as part of the general 
duty requirements: Identification of hazards which may result from an 
accidental release using appropriate hazard assessment techniques, 
designing and maintaining a safe facility taking such steps as 
necessary to prevent accidental releases, and actions which minimize 
the consequences of an accidental release once it has occurred. Section 
112(r)(1) specifically indicates that the general duty provision 
applies in the same manner and to the same extent as OSHA's general 
duty clause under section 654, title 29 of the U.S. Code. The Agency is 
investigating the relationship between requirements under section 
112(r) and OSHA's general duty provisions.
    Comments were also received on the separate issuance of the list 
and thresholds rule and the risk management program rule. The comments 
focused on the difficulties for the regulated community to evaluate and 
comment on the full impact of the list and thresholds without specific 
information on the accident prevention requirements. The Agency agrees 
that the separation of these rules does not allow the regulated 
community the optimum opportunity to comment on the proposed 
regulation. While the Agency recognizes that the two rules comprise a 
single program, the statute allows for proposal and promulgation of the 
list and thresholds rule prior to the proposal and promulgation of the 
section 112(r)(7) rule. Because EPA's duty to publish the list and 
thresholds rule arose before the duty to publish the risk management 
program rule, the Agency was obligated to publish the proposed list and 
thresholds rule before the section 112(r)(7)(B) proposed rule was 
publishable. The Agency has just published a proposed notice for the 
prevention requirements applicable to facilities having the listed 
substances above the threshold quantities (Risk Management Programs for 
Chemical Accidental Release Prevention, 58 FR 54190, October 20, 1993). 
The comment period for the risk management program rule will be open at 
the time this rule is finalized. This will give commenters the 
opportunity to comment on the risk management program with the 
knowledge of what substances are covered.

V. Summary of Provisions of the Final Rule

    EPA is adding part 68 to title 40 of the Code of Federal 
Regulations, including the list of regulated substances and threshold 
quantities, as well as the requirements for the petition process to add 
regulated substances to the list or to delete regulated substances from 
the list.
    Section 68.1 establishes the scope of the Part 68 chemical accident 
prevention provisions.
    Section 68.3 establishes definitions applicable to all Part 68 
regulations.
    Section 68.100 establishes the purpose of the subpart as the 
designation of regulated substances and their threshold quantities, and 
establishment of the requirements for petitions to add substances or 
delete substances from the list.
    Section 68.115 (proposed Sec. 68.5) establishes the procedures to 
determine whether a threshold quantity of a regulated substance is 
present at a stationary source. Specific exemptions to the threshold 
determination procedure are also included for mixture concentrations, 
articles, and certain uses and activities.
    The final rule includes several exemptions for mixtures that have 
been revised from the proposed rule. These are:
    (1) For toxic substances present in a mixture or solution at a 
concentration of one percent or greater by weight, the facility has the 
option of demonstrating that the partial pressure of the regulated 
substance in the solution under any or all storage or handling 
conditions is less than 10 mm Hg; in this case, the quantity of the 
regulated substance in the mixture in the portion of the process with a 
partial pressure of less than 10 mm Hg would be exempt from threshold 
determination;
    (2) Mixtures containing regulated flammable substances are exempt 
from threshold determination if the facility demonstrates that the 
mixture itself does not meet the criteria for flammability (flash point 
below 73 deg.F (22.8 deg.C) and boiling point below 100 deg.F 
(37.8 deg.C); and
    (3) Mixtures of Division 1.1 explosives listed in 49 CFR 172.101 
and other explosives need not be considered when determining whether a 
threshold quantity is present, provided that the mixture is intended to 
be intentionally released (i.e., a non-accidental release) in a manner 
consistent with DOT and BATF regulations.
    Section 68.120 specifies the requirements for petitions to the 
Agency to add substances to the list, and to delete substances from the 
list. Petition requirements have been modified slightly to read that a 
substance may be deleted from the list if adequate data are available 
to determine that the substance, in the case of an accidental release, 
is ``unlikely to cause'' (rather than ``will not cause'') death, 
injury, or serious adverse effects to human health or the environment.
    Section 68.125 exempts ammonia used as an agricultural nutrient 
when held by a farmer.
    Section 68.130 establishes the list of regulated substances, 
including a list of toxic substances, a list of flammable substances, 
and a list criterion for commercial high explosives. This section also 
establishes the threshold quantities for all listed substances.
    The final rule includes several changes to the proposed list and 
thresholds. Eighteen substances, with vapor pressures below 10 mm Hg, 
have been deleted from the proposed list of toxic substances, and one 
substance (vinyl chloride) has been moved from the list of toxic 
substances to the list of flammable substances. One substance, methyl 
bromide, has been deleted because it is listed under Title VI of the 
CAA. Four substances on the proposed list, included partly because of 
their accident history, have been deleted while another, oleum, has 
been specifically listed. The final list contains 77 toxic substances. 
Concentration cut-off levels have been specified for solutions of two 
additional substances, hydrogen fluoride and nitric acid. The 
concentration cut-off level has been raised for hydrochloric acid from 
25 to 30 percent by weight. Threshold quantities have been raised for 
71 of the 77 toxic substances listed. The final list contains 63 
flammable substances, with the threshold quantity remaining at 10,000 
lbs. The listing of explosive substances has been modified only to 
include those substances listed by DOT in 49 CFR 172.101; the Agency is 
also clarifying the applicability of the mixture concentration 
provision for explosives.

VI. Required Analyses

A. E.O. 12866

    Under Executive Order 12866, 58 Federal Register 51735 (October 4, 
1993), the Agency must determine whether the regulatory action is 
``significant'', and therefore subject to OMB review and the 
requirements of the Executive Order. The Order defines ``significant 
regulatory action'' as one that is likely to result in a rule that may:
    (1) Have an annual effect on the economy of $100 million or more or 
adversely affect in a material way the economy, a sector of the 
economy, productivity, competition, jobs, the environment, public 
health or safety, or state, local, or tribal government or communities;
    (2) Create a serious inconsistency or otherwise interfere with an 
action taken or planned by another agency;
    (3) Materially alter the budgetary impact of entitlements, grants, 
user fees, or loan programs or the rights and obligations of recipients 
thereof; or
    (4) Raise novel legal or policy issues arising out of legal 
mandates, the President's priorities, or the principles set forth in 
the Executive Order.
    Pursuant to the terms of the Executive Order 12866, it has been 
determined that this rule is a ``significant regulatory action''. Even 
though the list and thresholds rule, by itself, imposes no cost on 
facilities, the cost impact of the list and thresholds derives from 
compliance with the risk management program regulations and other 
reasonable regulations, which are triggered by the presence of a 
regulated substance above its threshold quantity. The annual effect on 
the economy for the accidental release prevention regulations that will 
be triggered by this rule is expected to exceed $100 million. As such, 
this action is submitted to OMB for review as part of a larger 
accidental release prevention program. Changes made in response to OMB 
suggestions or recommendations will be documented in the public record.
    The Agency developed a draft Regulatory Impacts Analysis (RIA) for 
the proposed rule that considered the cost for the accidental release 
prevention program envisioned under section 112(r); this draft RIA 
includes the list and thresholds and the risk management program 
requirements. The list rule, by itself, imposes only very minimal costs 
associated with the petition requirements for additions to, and 
deletions from, the list and for the documentation of mixtures; the 
majority of costs relate to actions that facilities with listed 
chemicals must undertake as a result of the risk management program 
rule.
    The requirements under the OSHA Process Safety Management Standard, 
which parallels the EPA risk management planning requirements, have now 
been in place for some time, and information is becoming available on 
the costs to facilities working to comply with OSHA. An addendum to the 
draft RIA was developed for the proposed risk management program rule 
to reflect public comments and the new information. The Agency estimate 
of the universe of facilities covered by the final list and thresholds 
rule has since been revised. EPA now estimates that approximately 
118,000 facilities will be covered by the final list and thresholds 
rule. The distribution of facilities covered includes 11,000 
manufacturers and 107,000 non-manufacturers (i.e., refineries; public 
drinking water and waste treatment systems; cold storage facilities; 
wholesalers; agricultural retailers; service industry facilities; 
private utilities; propane retailers, propane users, explosives 
manufacturers, and gas extraction and processing facilities). The 
average number of regulated substances per facility varies from one for 
cold storage facilities to six for highly complex manufacturing 
facilities.
    EPA estimates that the petition process under this rulemaking will 
cost a facility submitting a petition an average of $5,000. EPA 
estimates that there will be 11 petitions a year. EPA anticipates that 
the cost to the Federal government for processing and reviewing the 
petitions will be approximately equal to the cost to facilities for 
filing a petition. The total annual cost is estimated to be $110,000 
($5,000x2x11 petitions).

B. Regulatory Flexibility Act

    Pursuant to the Regulatory Flexibility Act of 1980, 5 U.S.C. 601 et 
seq., when an agency publishes a notice of rulemaking, for a rule that 
will have a significant effect on a substantial number of small 
entities, the agency must prepare and make available for public comment 
a regulatory flexibility analysis that considers the effect of the rule 
on small entities (i.e., small businesses, small organizations, and 
small governmental jurisdictions).
    The list rule, by itself, imposes only very minimal costs 
associated with the petition requirements for additions to, and 
deletions from, the list and for the documentation of mixtures; the 
majority of costs relate to actions that facilities with listed 
chemicals must undertake as a result of the risk management program 
rule. The risk management program regulation was proposed by EPA on 
October 20, 1993 (58 FR 54190); a discussion of the impacts on small 
entities is included on page 54212. The initial Regulatory Flexibility 
Analysis is contained in the combined economic analysis entitled 
Regulatory Impact Analysis in Support of Listing Regulated Substances 
and Thresholds and Mandating Risk Management Programs for Chemical 
Accident Prevention, as Required by Section 112(r) of the CAA, 
available in the docket. A revised economic analysis will be developed 
in conjunction with the final risk management program regulation.

C. Paperwork Reduction Act

    The information collection requirements contained in this rule have 
been approved by the Office of Management and Budget (OMB) under the 
provisions of the Paperwork Reduction Act, 44 U.S.C. 3501 et seq. and 
have been assigned control number 2050-0127.
    Public reporting for this collection of information in the petition 
process is estimated to be approximately 138 hours per response, 
including time for reviewing instructions, searching existing data 
sources, gathering and maintaining the data needed, and completing and 
reviewing the collection of information. EPA estimates that there will 
be 11 petitions a year. The total annual burden is estimated to be 
1,518 hours (138 hours  x  11 petitions).
    Send comments regarding the burden estimate or any other aspect of 
this collection of information, including suggestions for reducing the 
burden, to:

    Chief, Information Policy Branch, PM-223, U.S., Environmental 
Protection Agency, 401 M St. SW., Washington, DC 20460; and to the 
Office of Information and Regulatory Affairs, Office of Management 
and Budget, Washington, DC 20503, marked ``Attention: Desk Officer 
for EPA.''

D. Display of OMB Control Numbers

    EPA is also amending the table of currently approved information 
collection request (ICR) control numbers issued by OMB for various 
regulations. This amendment updates the table to accurately display 
those information requirements contained in this final rule. This 
display of the OMB control number and its subsequent codification in 
the Code of Federal Regulations satisfies the requirements of the 
Paperwork Reduction Act (44 U.S.C. 3501 et seq.) and OMB's implementing 
regulations at 5 CFR part 1320.
    The ICR was previously subject to public notice and comment prior 
to OMB approval. As a result, EPA finds that there is ``good cause'' 
under section 553(b)(B) of the Administrative Procedure Act (5 U.S.C. 
553(b)(B)) to amend this table without prior notice and comment. Due to 
the technical nature of the table, further notice and comment would be 
unnecessary. For the same reasons, EPA also finds that there is good 
cause under 5 U.S.C. 553(d)(3).

List of Subjects

40 CFR Part 9

    Environmental protection, paperwork reduction act.

40 CFR Part 68

    Environmental protection, Chemicals, Chemical accident prevention, 
Clean Air Act, Extremely hazardous substances, Intergovernmental 
relations, Hazardous substances, Reporting and Recordkeeping 
requirements.

    Dated: January 14, 1994.
Carol M. Browner,
Administrator.
    For the reasons set out in the preamble, title 40, chapter I, 
subchapter A, part 9 of the Code of Federal Regulations is amended, and 
title 40, chapter I, subchapter C, part 68 of the Code of Federal 
Regulations is added, as set forth below:

PART 9--OMB APPROVALS UNDER THE PAPERWORK REDUCTION ACT

    1. The authority citation for part 9 continues to read as follows:

    Authority: 7 U.S.C. 135 et seq., 136-136y; 15 U.S.C. 2001, 2003, 
2005, 2006, 2601-2671; 21 U.S.C. 331j, 346a, 348; 31 U.S.C. 9701; 33 
U.S.C. 1251 et seq., 1311, 1313d, 1314, 1321, 1326, 1330, 1344, 1345 
(d) and (e), 1361; E.O. 11735, 38 FR 21243, 3 CFR, 1971-1975 Comp. 
p. 973; 42 U.S.C. 241, 242b, 243, 246, 300f, 300g, 300g-1, 300g-2, 
300g-3, 300g-4, 300g-5, 300g-6, 300j-1, 300j-2, 300j-3, 300j-4, 
300j-9, 1857 et seq., 6901-6992k, 7401-7671q, 7542, 9601-9657, 
11023, 11048.

    2. Section 9.1 is amended by adding the new entry with a new 
heading to the table to read as follows:


Sec. 9.1  OMB approvals under the Paperwork Reduction Act.

* * * * *

------------------------------------------------------------------------
                                                             OMB control
                      40 CFR citation                            No.    
------------------------------------------------------------------------
                                                                        
                                  *****                                 
Chemical Accident Prevention Provisions:                                
  68.120 (a), (e), and (g).................................    2050-0127
                                                                        
                                  *****                                 
------------------------------------------------------------------------

    3. Part 68 is added to read as follows:

PART 68--CHEMICAL ACCIDENT PREVENTION PROVISIONS

Subpart A--General

Sec.
68.1  Scope.
68.3  Definitions.

Subpart B--Risk Management Plan Requirements [Reserved]

Subpart C--Regulated Substances for Accidental Release Prevention

68.100  Purpose.
68.115  Threshold determination.
68.120  Petition process.
68.125  Exemptions.
68.130  List of substances.

    Authority: 42 U.S.C. 7412(r), 7601.

Subpart A--General


Sec. 68.1  Scope.

    This Part sets forth the list of regulated substances and 
thresholds, the petition process for adding or deleting substances to 
the list of regulated substances, the requirements for owners or 
operators of stationary sources concerning the prevention of accidental 
releases, and the State accidental release prevention programs approved 
under section 112(r). The list of substances, threshold quantities, and 
accident prevention regulations promulgated under this part do not 
limit in any way the general duty provisions under section 112(r)(1).


Sec. 68.3  Definitions.

    For the purposes of this Part:
    Accidental release means an unanticipated emission of a regulated 
substance or other extremely hazardous substance into the ambient air 
from a stationary source.
    Administrator means the administrator of the U.S. Environmental 
Protection Agency.
    Article means a manufactured item, as defined under 29 CFR 
1910.1200(b), that is formed to a specific shape or design during 
manufacture, that has end use functions dependent in whole or in part 
upon the shape or design during end use, and that does not release or 
otherwise result in exposure to a regulated substance under normal 
conditions of processing and use.
    CAS means the Chemical Abstracts Service.
    DOT means the United States Department of Transportation.
    Process means any activity involving a regulated substance 
including any use, storage, manufacturing, handling, or on-site 
movement of such substances, or combination of these activities. For 
the purposes of this definition, any group of vessels that are 
interconnected, or separate vessels that are located such that a 
regulated substance could be involved in a potential release, shall be 
considered a single process.
    Regulated substance is any substance listed pursuant to section 
112(r)(3) of the Clean Air Act as amended, in Sec. 68.130.
    Stationary source means any buildings, structures, equipment, 
installations, or substance emitting stationary activities which belong 
to the same industrial group, which are located on one or more 
contiguous properties, which are under the control of the same person 
(or persons under common control), and from which an accidental release 
may occur. A stationary source includes transportation containers that 
are no longer under active shipping papers and transportation 
containers that are connected to equipment at the stationary source for 
the purposes of temporary storage, loading, or unloading. The term 
stationary source does not apply to transportation, including the 
storage incident to transportation, of any regulated substance or any 
other extremely hazardous substance under the provisions of this part, 
provided that such transportation is regulated under 49 CFR parts 192, 
193, or 195. Properties shall not be considered contiguous solely 
because of a railroad or gas pipeline right-of-way.
    Threshold quantity means the quantity specified for regulated 
substances pursuant to section 112(r)(5) of the Clean Air Act as 
amended, listed in Sec. 68.130 and determined to be present at a 
stationary source as specified in Sec. 68.115 of this Part.
    Vessel means any reactor, tank, drum, barrel, cylinder, vat, 
kettle, boiler, pipe, hose, or other container.

Subpart B--Risk Management Plan Requirements [Reserved]

Subpart C--Regulated Substances for Accidental Release Prevention


Sec. 68.100  Purpose.

    This subpart designates substances to be listed under section 
112(r)(3), (4), and (5) of the Clean Air Act, as amended, identifies 
their threshold quantities, and establishes the requirements for 
petitioning to add or delete substances from the list.


Sec. 68.115  Threshold determination.

    (a) A threshold quantity of a regulated substance listed in 
Sec. 68.130 is present at a stationary source if the total quantity of 
the regulated substance contained in a process exceeds the threshold.
    (b) For the purposes of determining whether more than a threshold 
quantity of a regulated substance is present at the stationary source, 
the following exemptions apply:
    (1) Concentrations of a regulated toxic substance in a mixture. If 
a regulated substance is present in a mixture and the concentration of 
the substance is below one percent by weight of the mixture, the amount 
of the substance in the mixture need not be considered when determining 
whether more than a threshold quantity is present at the stationary 
source. Except for oleum, toluene 2,4-diisocyanate, toluene 2,6-
diisocyanate, and toluene diisocyanate (unspecified isomer), if the 
concentration of the regulated substance in the mixture is one percent 
or greater by weight, but the owner or operator can demonstrate that 
the partial pressure of the regulated substance in the mixture 
(solution) under handling or storage conditions in any portion of the 
process is less than 10 millimeters of mercury (mm Hg), the amount of 
the substance in the mixture in that portion of the process need not be 
considered when determining whether more than a threshold quantity is 
present at the stationary source. The owner or operator shall document 
this partial pressure measurement or estimate.
    (2) Concentrations of a regulated flammable substance in a mixture. 
If a regulated substance is present in a mixture and the concentration 
of the substance is below one percent by weight of the mixture, the 
mixture need not be considered when determining whether more than a 
threshold quantity of the regulated substance is present at the 
stationary source. If the concentration of the regulated substance in 
the mixture is one percent or greater by weight, then, for purposes of 
determining whether more than a threshold quantity is present at the 
stationary source, the entire weight of the mixture shall be treated as 
the regulated substance unless the owner or operator can demonstrate 
that the mixture itself does not meet the criteria for flammability of 
flash point below 73 deg.F (22.8 deg.C) and boiling point below 
100 deg.F (37.8 deg.C). The owner or operator shall document these 
flash point and boiling point measurements or estimates.
    (3) Concentrations of a regulated explosive substance in a mixture. 
Mixtures of Division 1.1 explosives listed in 49 CFR 172.101 (Hazardous 
Materials Table) and other explosives need not be included when 
determining whether a threshold quantity is present in a process, when 
the mixture is intended to be used on-site in a non-accidental release 
in a manner consistent with applicable BATF regulations. Other mixtures 
of Division 1.1 explosives listed in 49 CFR 172.101 and other 
explosives shall be included in determining whether more than a 
threshold quantity is present in a process if such mixtures would be 
treated as Division 1.1 explosives under 49 CFR Parts 172 and 173.
    (4) Articles. Regulated substances contained in articles need not 
be considered when determining whether more than a threshold quantity 
is present at the stationary source.
    (5) Uses. Regulated substances, when in use for the following 
purposes, need not be included in determining whether more than a 
threshold quantity is present at the stationary source:
    (i) Use as a structural component of the stationary source;
    (ii) Use of products for routine janitorial maintenance;
    (iii) Use by employees of foods, drugs, cosmetics, or other 
personal items containing the regulated substance; and
    (iv) Use of regulated substances present in process water or non-
contact cooling water as drawn from the environment or municipal 
sources, or use of regulated substances present in air used either as 
compressed air or as part of combustion.
    (6) Activities in Laboratories. If a regulated substance is 
manufactured, processed, or used in a laboratory at a stationary source 
under the supervision of a technically qualified individual as defined 
in Sec. 720.3(ee) of this chapter, the quantity of the substance need 
not be considered in determining whether a threshold quantity is 
present. This exemption does not apply to:
    (i) Specialty chemical production;
    (ii) Manufacture, processing, or use of substances in pilot plant 
scale operations; and
    (iii) Activities conducted outside the laboratory.


Sec. 68.120  Petition process.

    (a) Any person may petition the Administrator to modify, by 
addition or deletion, the list of regulated substances identified in 
Sec. 68.130. Based on the information presented by the petitioner, the 
Administrator may grant or deny a petition.
    (b) A substance may be added to the list if, in the case of an 
accidental release, it is known to cause or may be reasonably 
anticipated to cause death, injury, or serious adverse effects to human 
health or the environment.
    (c) A substance may be deleted from the list if adequate data on 
the health and environmental effects of the substance are available to 
determine that the substance, in the case of an accidental release, is 
not known to cause and may not be reasonably anticipated to cause 
death, injury, or serious adverse effects to human health or the 
environment.
    (d) No substance for which a national primary ambient air quality 
standard has been established shall be added to the list. No substance 
regulated under Title VI of the Clean Air Act, as amended, shall be 
added to the list.
    (e) The burden of proof is on the petitioner to demonstrate that 
the criteria for addition and deletion are met. A petition will be 
denied if this demonstration is not made.
    (f) The Administrator will not accept additional petitions on the 
same substance following publication of a final notice of the decision 
to grant or deny a petition, unless new data becomes available that 
could significantly affect the basis for the decision.
    (g) Petitions to modify the list of regulated substances must 
contain the following:
    (1) Name and address of the petitioner and a brief description of 
the organization(s) that the petitioner represents, if applicable;
    (2) Name, address, and telephone number of a contact person for the 
petition;
    (3) Common chemical name(s), common synonym(s), Chemical Abstracts 
Service number, and chemical formula and structure;
    (4) Action requested (add or delete a substance);
    (5) Rationale supporting the petitioner's position; that is, how 
the substance meets the criteria for addition and deletion. A short 
summary of the rationale must be submitted along with a more detailed 
narrative; and
    (6) Supporting data; that is, the petition must include sufficient 
information to scientifically support the request to modify the list. 
Such information shall include:
    (i) A list of all support documents;
    (ii) Documentation of literature searches conducted, including, but 
not limited to, identification of the database(s) searched, the search 
strategy, dates covered, and printed results;
    (iii) Effects data (animal, human, and environmental test data) 
indicating the potential for death, injury, or serious adverse human 
and environmental impacts from acute exposure following an accidental 
release; printed copies of the data sources, in English, should be 
provided; and
    (iv) Exposure data or previous accident history data, indicating 
the potential for serious adverse human health or environmental effects 
from an accidental release. These data may include, but are not limited 
to, physical and chemical properties of the substance, such as vapor 
pressure; modeling results, including data and assumptions used and 
model documentation; and historical accident data, citing data sources.
    (h) Within 18 months of receipt of a petition, the Administrator 
shall publish in the Federal Register a notice either denying the 
petition or granting the petition and proposing a listing.


Sec. 68.125  Exemptions.

    Agricultural nutrients. Ammonia used as an agricultural nutrient, 
when held by farmers, is exempt from all provisions of this part.


Sec. 68.130  List of substances.

    (a) Explosives listed by DOT as Division 1.1 in 49 CFR 172.101 are 
covered under section 112(r) of the Clean Air Act. The threshold 
quantity for explosives is 5,000 pounds.
    (b) Regulated toxic and flammable substances under section 112(r) 
of the Clean Air Act are the substances listed in Tables 1, 2, 3, and 
4. Threshold quantities for listed toxic and flammable substances are 
specified in the tables.
    (c) The basis for placing toxic and flammable substances on the 
list of regulated substances are explained in the notes to the list.

     Table 1 to Sec. 68.130.--List of Regulated Toxic Substances and    
         Threshold Quantities for Accidental Release Prevention         
                  [Alphabetical Order--77 Substances]                   
------------------------------------------------------------------------
                                                   Threshold            
          Chemical name               CAS No.       quantity   Basis for
                                                     (lbs)      listing 
------------------------------------------------------------------------
Acrolein [2-Propenal]............        107-02-8      5,000  b         
Acrylonitrile [2-Propenenitrile].        107-13-1     20,000  b         
Acrylyl chloride [2-Propenoyl            814-68-6      5,000  b         
 chloride].                                                             
Allyl alcohol [2-Propen-l-ol]....       107-18-61     15,000  b         
Allylamine [2-Propen-l-amine]....        107-11-9     10,000  b         
Ammonia (anhydrous)..............       7664-41-7     10,000  a, b      
Ammonia (conc 20% or greater)....       7664-41-7     20,000  a, b      
Arsenous trichloride.............       7784-34-1     15,000  b         
Arsine...........................       7784-42-1      1,000  b         
Boron trichloride [Borane,             10294-34-5      5,000  b         
 trichloro-].                                                           
Boron trifluoride [Borane,              7637-07-2      5,000  b         
 trifluoro-].                                                           
Boron trifluoride compound with          353-42-4     15,000  b         
 methyl ether (1:1) [Boron,                                             
 trifluoro[oxybis[metane]]-, T-4-.                                      
Bromine..........................       7726-95-6     10,000  a, b      
Carbon disulfide.................         75-15-0     20,000  b         
Chlorine.........................       7782-50-5      2,500  a, b      
Chlorine dioxide [Chlorine oxide       10049-04-4      1,000  c         
 (ClO2)].                                                               
Chloroform [Methane, trichloro-].         67-66-3     20,000  b         
Chloromethyl ether [Methane,             542-88-1      1,000  b         
 oxybis[chloro-].                                                       
Chloromethyl methyl ether                107-30-2      5,000  b         
 [Methane, chloromethoxy-].                                             
Crotonaldehyde [2-Butenal].......       4170-30-3     20,000  b         
Crotonaldehyde, (E)- [2-Butenal,         123-73-9     20,000  b         
 (E)-].                                                                 
Cyanogen chloride................        506-77-4     10,000  c         
Cyclohexylamine [Cyclohexanamine]        108-91-8     15,000  b         
Diborane.........................      19287-45-7      2,500  b         
Dimethyldichlorosilane [Silane,           75-78-5      5,000  b         
 dichlorodimethyl-].                                                    
1,1-Dimethylhydrazine [Hydrazine,         57-14-7     15,000  b         
 1,1-dimethyl-].                                                        
Epichlorohydrin [Oxirane,                106-89-8     20,000  b         
 (chloromethyl)-].                                                      
Ethylenediamine [1,2-                    107-15-3     20,000  b         
 Ethanediamine].                                                        
Ethyleneimine [Aziridine]........        151-56-4     10,000  b         
Ethylene oxide [Oxirane].........         75-21-8     10,000  a, b      
Fluorine.........................       7782-41-4      1,000  b         
Formaldehyde (solution)..........         50-00-0     15,000  b         
Furan............................        110-00-9      5,000  b         
Hydrazine........................        302-01-2     15,000  b         
Hydrochloric acid (conc 30% or          7647-01-0     15,000  d         
 greater).                                                              
Hydrocyanic acid.................         74-90-8      2,500  a, b      
Hydrogen chloride (anhydrous)           7647-01-0      5,000  a         
 [Hydrochloric acid].                                                   
Hydrogen fluoride/Hydrofluoric          7664-39-3      1,000  a, b      
 acid (conc 50% or greater)                                             
 [Hydrofluoric acid].                                                   
Hydrogen selenide................       7783-07-5        500  b         
Hydrogen sulfide.................       7783-06-4     10,000  a, b      
Iron, pentacarbonyl- [Iron             13463-40-6      2,500  b         
 carbonyl (Fe(CO)5), (TB-5-11)-].                                       
Isobutyronitrile [Propanenitrile,         78-82-0     20,000  b         
 2-methyl-].                                                            
Isopropyl chloroformate                  108-23-6     15,000  b         
 [Carbonochloridic acid, 1-                                             
 methylethyl ester].                                                    
Methacrylonitrile [2-                    126-98-7     10,000  b         
 Propenenitrile, 2-methyl-].                                            
Methyl chloride [Methane, chloro-         74-87-3     10,000  a         
 ].                                                                     
Methyl chloroformate                      79-22-1      5,000  b         
 [Carbonochloridic acid,                                                
 methylester].                                                          
Methyl hydrazine [Hydrazine,              60-34-4     15,000  b         
 methyl-].                                                              
Methyl isocyanate [Methane,              624-83-9     10,000  a, b      
 isocyanato-].                                                          
Methyl mercaptan [Methanethiol]..         74-93-1     10,000  b         
Methyl thiocyanate [Thiocyanic           556-64-9     20,000  b         
 acid, methyl ester].                                                   
Methyltrichlorosilane [Silane,            75-79-6      5,000  b         
 trichloromethyl-].                                                     
Nickel carbonyl..................      13463-39-3      1,000  b         
Nitric acid (conc 80% or greater)       7697-37-2     15,000  b         
Nitric oxide [Nitrogen oxide           10102-43-9     10,000  b         
 (NO)].                                                                 
Oleum (Fuming Sulfuric acid)            8014-95-7     10,000  e         
 [Sulfuric acid, mixture with                                           
 sulfur trioxide]\1\.                                                   
Peracetic acid [Ethaneperoxoic            79-21-0     10,000  b         
 acid].                                                                 
Perchloromethylmercaptan                 594-42-3     10,000  b         
 [Methanesulfenyl chloride,                                             
 trichloro-].                                                           
Phosgene [Carbonic dichloride]...         75-44-5        500  a, b      
Phosphine........................       7803-51-2      5,000  b         
Phosphorus oxychloride                 10025-87-3      5,000  b         
 [Phosphoryl chloride].                                                 
Phosphorus trichloride                  7719-12-2     15,000  b         
 [Phosphorous trichloride].                                             
Piperidine.......................        110-89-4     15,000  b         
Propionitrile [Propanenitrile]...        107-12-0     10,000  b         
Propyl chloroformate                     109-61-5     15,000  b         
 [Carbonochloridic acid,                                                
 propylester].                                                          
Propyleneimine [Aziridine, 2-             75-55-8     10,000  b         
 methyl-].                                                              
Propylene oxide [Oxirane, methyl-         75-56-9     10,000  b         
 ].                                                                     
Sulfur dioxide (anhydrous).......       7446-09-5      5,000  a, b      
Sulfur tetrafluoride [Sulfur            7783-60-0      2,500  b         
 fluoride (SF4), (T-4)-].                                               
Sulfur trioxide..................       7446-11-9     10,000  a, b      
Tetramethyllead [Plumbane,                75-74-1     10,000  b         
 tetramethyl-].                                                         
Tetranitromethane [Methane,              509-14-8     10,000  b         
 tetranitro-].                                                          
Titanium tetrachloride [Titanium        7550-45-0      2,500  b         
 chloride (TiCl4) (T-4)-].                                              
Toluene 2,4-diisocyanate                 584-84-9     10,000  a         
 [Benzene, 2,4-diisocyanato-1-                                          
 methyl-]\1\.                                                           
Toluene 2,6-diisocyanate                  91-08-7     10,000  a         
 [Benzene, 1,3-diisocyanato-2-                                          
 methyl-]\1\.                                                           
Toluene diisocyanate (unspecified      26471-62-5     10,000  a         
 isomer) [Benzene, 1,3-                                                 
 diisocyanatomethyl-]\1\.                                               
Trimethylchlorosilane [Silane,            75-77-4     10,000  b         
 chlorotrimethyl-].                                                     
Vinyl acetate monomer [Acetic            108-05-4     15,000  b         
 acid ethenyl ester].                                                   
------------------------------------------------------------------------
\1\The mixture exemption in Sec. 68.115(b)(1) does not apply to the     
  substance.                                                            
                                                                        
Note: Basis for Listing:                                                
aMandated for listing by Congress.                                      
bOn EHS list, vapor pressure 10 mmHg or greater.                        
cToxic gas.                                                             
dToxicity of hydrogen chloride, potential to release hydrogen chloride, 
  and history of accidents.                                             
eToxicity of sulfur trioxide and sulfuric acid, potential to release    
  sulfur trioxide, and history of accidents.                            


     Table 2 to Sec. 68.130.--List of Regulated Toxic Substances and    
         Threshold Quantities for Accidental Release Prevention         
                    [CAS Number Order--77 Substances]                   
------------------------------------------------------------------------
                                                   Threshold            
       CAS No.               Chemical name          quantity   Basis for
                                                     (lbs)      listing 
------------------------------------------------------------------------
50-00-0.............  Formaldehyde (solution)....     15,000  b         
57-14-7.............  1,1-Dimethylhydrazine           15,000  b         
                       [Hydrazine, 1,1-dimethyl-].                      
60-34-4.............  Methyl hydrazine                15,000  b         
                       [Hydrazine, methyl-].                            
67-66-3.............  Chloroform [Methane,            20,000  b         
                       trichloro-].                                     
74-87-3.............  Methyl chloride [Methane,       10,000  a         
                       chloro-].                                        
74-90-8.............  Hydrocyanic acid...........      2,500  a, b      
74-93-1.............  Methyl mercaptan                10,000  b         
                       [Methanethiol].                                  
75-15-0.............  Carbon disulfide...........     20,000  b         
75-21-8.............  Ethylene oxide [Oxirane]...     10,000  a, b      
75-44-5.............  Phosgene [Carbonic                 500  a, b      
                       dichloride].                                     
75-55-8.............  Propyleneimine [Aziridine,      10,000  b         
                       2-methyl-].                                      
75-56-9.............  Propylene oxide [Oxirane,       10,000  b         
                       methyl-].                                        
75-74-1.............  Tetramethyllead [Plumbane,      10,000  b         
                       tetramethyl-].                                   
75-77-4.............  Trimethylchlorosilane           10,000  b         
                       [Silane, chlorotrimethyl-].                      
75-78-5.............  Dimethyldichlorosilane           5,000  b         
                       [Silane, dichlorodimethyl-                       
                       ].                                               
75-79-6.............  Methyltrichlorosilane            5,000  b         
                       [Silane, trichloromethyl-].                      
78-82-0.............  Isobutyronitrile                20,000  b         
                       [Propanenitrile, 2-methyl-                       
                       ].                                               
79-21-0.............  Peracetic acid                  10,000  b         
                       [Ethaneperoxoic acid].                           
79-22-1.............  Methyl chloroformate             5,000  b         
                       [Carbonochloridic acid,                          
                       methylester].                                    
91-08-7.............  Toluene 2,6-diisocyanate        10,000  a         
                       [Benzene, 1,3-diisocyanato-                      
                       2-methyl-]\1\.                                   
106-89-8............  Epichlorohydrin [Oxirane,       20,000  b         
                       (chloromethyl)-].                                
107-02-8............  Acrolein [2-Propenal]......      5,000  b         
107-11-9............  Allylamine [2-Propen-1-         10,000  b         
                       amine].                                          
107-12-0............  Propionitrile                   10,000  b         
                       [Propanenitrile].                                
107-13-1............  Acrylonitrile [2-               20,000  b         
                       Propenenitrile].                                 
107-15-3............  Ethylenediamine [1,2-           20,000  b         
                       Ethanediamine].                                  
107-18-6............  Allyl alcohol [2-Propen-1-      15,000  b         
                       ol].                                             
107-30-2............  Chloromethyl methyl ether        5,000  b         
                       [Methane, chloromethoxy-].                       
108-05-4............  Vinyl acetate monomer           15,000  b         
                       [Acetic acid ethenyl                             
                       ester].                                          
108-23-6............  Isopropyl chloroformate         15,000  b         
                       [Carbonochloridic acid, 1-                       
                       methylethyl ester].                              
108-91-8............  Cyclohexylamine                 15,000  b         
                       [Cyclohexanamine].                               
109-61-5............  Propyl chloroformate            15,000  b         
                       [Carbonochloridic acid,                          
                       propylester].                                    
110-00-9............  Furan......................      5,000  b         
110-89-4............  Piperidine.................     15,000  b         
123-73-9............  Crotonaldehyde, (E)- [2-        20,000  b         
                       Butenal, (E)-].                                  
126-98-7............  Methacrylonitrile [2-           10,000  b         
                       Propenenitrile, 2-methyl-].                      
151-56-4............  Ethyleneimine [Aziridine]..     10,000  b         
302-01-2............  Hydrazine..................     15,000  b         
353-42-4............  Boron trifluoride compound      15,000  b         
                       with methyl ether (1:1)                          
                       [Boron,                                          
                       trifluoro[oxybis[methane]]-                      
                       , T-4-.                                          
506-77-4............  Cyanogen chloride..........     10,000  c         
509-14-8............  Tetranitromethane [Methane,     10,000  b         
                       tetranitro-].                                    
542-88-1............  Chloromethyl ether               1,000  b         
                       [Methane, oxybis[chloro-].                       
556-64-9............  Methyl thiocyanate              20,000  b         
                       [Thiocyanic acid, methyl                         
                       ester].                                          
584-84-9............  Toluene 2,4-diisocyanate        10,000  a         
                       [Benzene, 2,4-diisocyanato-                      
                       1-methyl-]\1\.                                   
594-42-3............  Perchloromethylmercaptan        10,000  b         
                       [Methanesulfenyl chloride,                       
                       trichloro-].                                     
624-83-9............  Methyl isocyanate [Methane,     10,000  a, b      
                       isocyanato-].                                    
814-68-6............  Acrylyl chloride [2-             5,000  b         
                       Propenoyl chloride].                             
4170-30-3...........  Crotonaldehyde [2-Butenal].     20,000  b         
7446-09-5...........  Sulfur dioxide (anhydrous).      5,000  a, b      
7446-11-9...........  Sulfur trioxide............     10,000  a, b      
7550-45-0...........  Titanium tetrachloride           2,500  b         
                       [Titanium chloride (TiCl4)                       
                       (T-4)-].                                         
7637-07-2...........  Boron trifluoride [Borane,       5,000  b         
                       trifluoro-].                                     
7647-01-0...........  Hydrochloric acid (conc 30%     15,000  d         
                       or greater).                                     
7647-01-0...........  Hydrogen chloride                5,000  a         
                       (anhydrous) [Hydrochloric                        
                       acid].                                           
7664-39-3...........  Hydrogen fluoride/               1,000  a, b      
                       Hydrofluoric acid (conc                          
                       50% or greater)                                  
                       [Hydrofluoric acid].                             
7664-41-7...........  Ammonia (anhydrous)........     10,000  a, b      
7664-41-7...........  Ammonia (conc 20% or            20,000  a, b      
                       greater).                                        
7697-37-2...........  Nitric acid (conc 80% or        15,000  b         
                       greater).                                        
7719-12-2...........  Phosphorus trichloride          15,000  b         
                       [Phosphorous trichloride].                       
7726-95-6...........  Bromine....................     10,000  a, b      
7782-41-4...........  Fluorine...................      1,000  b         
7782-50-5...........  Chlorine...................      2,500  a, b      
7783-06-4...........  Hydrogen sulfide...........     10,000  a, b      
7783-07-5...........  Hydrogen selenide..........        500  b         
7783-60-0...........  Sulfur tetrafluoride             2,500  b         
                       [Sulfur fluoride (SF4), (T-                      
                       4)-].                                            
7784-34-1...........  Arsenous trichloride.......     15,000  b         
7784-42-1...........  Arsine.....................      1,000  b         
7803-51-2...........  Phosphine..................      5,000  b         
8014-95-7...........  Oleum (Fuming Sulfuric          10,000  e         
                       acid) [Sulfuric acid,                            
                       mixture with sulfur                              
                       trioxide]\1\.                                    
10025-87-3..........  Phosphorus oxychloride           5,000  b         
                       [Phosphoryl chloride].                           
10049-04-4..........  Chlorine dioxide [Chlorine       1,000  c         
                       oxide (ClO2)].                                   
10102-43-9..........  Nitric oxide [Nitrogen          10,000  b         
                       oxide (NO)].                                     
10294-34-5..........  Boron trichloride [Borane,       5,000  b         
                       trichloro-].                                     
13463-39-3..........  Nickel carbonyl............      1,000  b         
13463-40-6..........  Iron, pentacarbonyl- [Iron       2,500  b         
                       carbonyl (Fe(CO)5), (TB-5-                       
                       11)-].                                           
19287-45-7..........  Diborane...................      2,500  b         
26471-62-5..........  Toluene diisocyanate            10,000  a         
                       (unspecified isomer)                             
                       [Benzene, 1,3-                                   
                       diisocyanatomethyl-1]\1\.                        
------------------------------------------------------------------------
\1\The mixture exemption in Sec. 68.115(b)(1) does not apply to the     
  substance.                                                            
Note: Basis for Listing:                                                
aMandated for listing by Congress.                                      
bOn EHS list, vapor pressure 10 mmHg or greater.                        
cToxic gas.                                                             
eToxicity of sulfur trioxide and sulfuric acid, potential to release    
  sulfur trioxide, and history of accidents.                            


   Table 3 to Sec. 68.130.--List of Regulated Flammable Substances and  
         Threshold Quantities for Accidental Release Prevention         
                  [Alphabetical Order--63 Substances]                   
------------------------------------------------------------------------
                                                   Threshold            
          Chemical name               CAS No.       quantity   Basis for
                                                     (lbs)      listing 
------------------------------------------------------------------------
Acetaldehyde.....................         75-07-0     10,000  g         
Acetylene [Ethyne]...............         74-86-2     10,000  f         
Bromotrifluorethylene [Ethene,           598-73-2     10,000  f         
 bromotrifluoro-].                                                      
1,3-Butadiene....................        106-99-0     10,000  f         
Butane...........................        106-97-8     10,000  f         
1-Butene.........................        106-98-9     10,000  f         
2-Butene.........................        107-01-7     10,000  f         
Butene...........................      25167-67-3     10,000  f         
2-Butene-cis.....................        590-18-1     10,000  f         
2-Butene-trans [2-Butene, (E)]...        624-64-6     10,000  f         
Carbon oxysulfide [Carbon oxide          463-58-1     10,000  f         
 sulfide (COS)].                                                        
Chlorine monoxide [Chlorine             7791-21-1     10,000  f         
 oxide].                                                                
2-Chloropropylene [1-Propene, 2-         557-98-2     10,000  g         
 chloro-].                                                              
1-Chloropropylene [1-Propene, 1-         590-21-6     10,000  g         
 chloro-].                                                              
Cyanogen [Ethanedinitrile].......        460-19-5     10,000  f         
Cyclopropane.....................         75-19-4     10,000  f         
Dichlorosilane [Silane, dichloro-       4109-96-0     10,000  f         
 ].                                                                     
Difluoroethane [Ethane, 1,1-              75-37-6     10,000  f         
 difluoro-].                                                            
Dimethylamine [Methanamine, N-           124-40-3     10,000  f         
 methyl-].                                                              
2,2-Dimethylpropane [Propane, 2,2-       463-82-1     10,000  f         
 dimethyl-].                                                            
Ethane...........................         74-84-0     10,000  f         
Ethyl acetylene [1-Butyne].......        107-00-6     10,000  f         
Ethylamine [Ethanamine]..........         75-04-7     10,000  f         
Ethyl chloride [Ethane, chloro-].         75-00-3     10,000  f         
Ethylene [Ethene]................         74-85-1     10,000  f         
Ethyl ether [Ethane, 1,1'-oxybis-         60-29-7     10,000  g         
 ].                                                                     
Ethyl mercaptan [Ethanethiol]....         75-08-1     10,000  g         
Ethyl nitrite [Nitrous acid,             109-95-5     10,000  f         
 ethyl ester].                                                          
Hydrogen.........................       1333-74-0     10,000  f         
Isobutane [Propane, 2-methyl]....         75-28-5     10,000  f         
Isopentane [Butane, 2-methyl-]...         78-78-4     10,000  g         
Isoprene [1,3-Butadinene, 2-              78-79-5     10,000  g         
 methyl-].                                                              
Isopropylamine [2-Propanamine]...         75-31-0     10,000  g         
Isopropyl chloride [Propane, 2-           75-29-6     10,000  g         
 chloro-].                                                              
Methane..........................         74-82-8     10,000  f         
Methylamine [Methanamine]........         74-89-5     10,000  f         
3-Methyl-1-butene................        563-45-1     10,000  f         
2-Methyl-1-butene................        563-46-2     10,000  g         
Methyl ether [Methane, oxybis-]..        115-10-6     10,000  f         
Methyl formate [Formic acid,             107-31-3     10,000  g         
 methyl ester].                                                         
2-Methylpropene [1-Propene, 2-           115-11-7     10,000  f         
 methyl-].                                                              
1,3-Pentadinene..................        504-60-9     10,000  f         
Pentane..........................        109-66-0     10,000  g         
1-Pentene........................        109-67-1     10,000  g         
2-Pentene, (E)-..................        646-04-8     10,000  g         
2-Pentene, (Z)-..................        627-20-3     10,000  g         
Propadiene [1,2-Propadiene]......        463-49-0     10,000  f         
Propane..........................         74-98-6     10,000  f         
Propylene [1-Propene]............        115-07-1     10,000  f         
Propyne [1-Propyne]..............         74-99-7     10,000  f         
Silane...........................       7803-62-5     10,000  f         
Tetrafluoroethylene [Ethene,             116-14-3     10,000  f         
 tetrafluoro-].                                                         
Tetramethylsilane [Silane,                75-76-3     10,000  g         
 tetramethyl-].                                                         
Trichlorosilane [Silane,               10025-78-2     10,000  g         
 trichloro-].                                                           
Trifluorochloroethylene [Ethene,          79-38-9     10,000  f         
 chlorotrifluoro-].                                                     
Trimethylamine [Methanamine, N,N-         75-50-3     10,000  f         
 dimethyl-].                                                            
Vinyl acetylene [1-Buten-3-yne]..        689-97-4     10,000  f         
Vinyl chloride [Ethene, chloro-].         75-01-4     10,000  a, f      
Vinyl ethyl ether [Ethene, ethoxy-       109-92-2     10,000  g         
 ].                                                                     
Vinyl fluoride [Ethene, fluoro-].         75-02-5     10,000  f         
Vinylidene chloride [Ethene, 1,1-         75-35-4     10,000  g         
 dichloro-].                                                            
Vinylidene fluoride [Ethene, 1,1-         75-38-7     10,000  f         
 difluoro-].                                                            
Vinyl methyl ether [Ethene,              107-25-5     10,000  f         
 methoxy-].                                                             
------------------------------------------------------------------------
Note: Basis for Listing:                                                
aMandated for listing by Congress.                                      
fFlammable gas.                                                         
gVolatile flammable liquid.                                             


 Table 4 to Sec. 68.130.--List of Regulated Flammable Substances and Threshold Quantities for Accidental Release
                                                   Prevention                                                   
                                        [CAS Number Order--63 Substances]                                       
----------------------------------------------------------------------------------------------------------------
                                                                                           Threshold            
      CAS No.                            Chemical name                        CAS No.       quantity   Basis for
                                                                                             (lbs)      listing 
----------------------------------------------------------------------------------------------------------------
60-29-7.............  Ethyl ether [Ethane, 1,1'-oxybis-].................         60-29-7     10,000  g         
74-82-8.............  Methane............................................         74-82-8     10,000  f         
74-84-0.............  Ethane.............................................         74-84-0     10,000  f         
74-85-1.............  Ethylene [Ethene]..................................         74-85-1     10,000  f         
74-86-2.............  Acetylene [Ethyne].................................         74-86-2     10,000  f         
74-89-5.............  Methylamine [Methanamine]..........................         74-89-5     10,000  f         
74-98-6.............  Propane............................................         74-98-6     10,000  f         
74-99-7.............  Propyne [1-Propyne]................................         74-99-7     10,000  f         
75-00-3.............  Ethyl chloride [Ethane, chloro-]...................         75-00-3     10,000  f         
75-01-4.............  Vinyl chloride [Ethene, chloro-]...................         75-01-4     10,000  a, f      
75-02-5.............  Vinyl fluoride [Ethene, fluoro-]...................         75-02-5     10,000  f         
75-04-7.............  Ethylamine [Ethanamine]............................         75-04-7     10,000  f         
75-07-0.............  Acetaldehyde.......................................         75-07-0     10,000  g         
75-08-1.............  Ethyl mercaptan [Ethanethiol]......................         75-08-1     10,000  g         
75-19-4.............  Cyclopropane.......................................         75-19-4     10,000  f         
75-28-5.............  Isobutane [Propane, 2-methyl]......................         75-28-5     10,000  f         
75-29-6.............  Isopropyl chloride [Propane, 2-chloro-]............         75-29-6     10,000  g         
75-31-0.............  Isopropylamine [2-Propanamine].....................         75-31-0     10,000  g         
75-35-4.............  Vinylidene chloride [Ethene, 1,1-dichloro-]........         75-35-4     10,000  g         
75-37-6.............  Difluoroethane [Ethane, 1,1-difluoro-].............         75-37-6     10,000  f         
75-38-7.............  Vinylidene fluoride [Ethene, 1,1-difluoro-]........         75-38-7     10,000  f         
75-50-3.............  Trimethylamine [Methanamine, N, N-dimethyl-].......         75-50-3     10,000  f         
75-76-3.............  Tetramethylsilane [Silane, tetramethyl-]...........         75-76-3     10,000  g         
78-78-4.............  Isopentane [Butane, 2-methyl-].....................         78-78-4     10,000  g         
78-79-5.............  Isoprene [1,3,-Butadiene, 2-methyl-]...............         78-79-5     10,000  g         
79-38-9.............  Trifluorochloroethylene [Ethene, chlorotrifluoro-].         79-38-9     10,000  f         
106-97-8............  Butane.............................................        106-97-8     10,000  f         
106-98-9............  1-Butene...........................................        106-98-9     10,000  f         
196-99-0............  1,3-Butadiene......................................        106-99-0     10,000  f         
107-00-6............  Ethyl acetylene [1-Butyne].........................        107-00-6     10,000  f         
107-01-7............  2-Butene...........................................        107-01-7     10,000  f         
107-25-5............  Vinyl methyl ether [Ethene, methoxy-]..............        107-25-5     10,000  f         
107-31-3............  Methyl formate [Formic acid, methyl ester].........        107-31-3     10,000  g         
109-66-0............  Pentane............................................        109-66-0     10,000  g         
109-67-1............  1-Pentene..........................................        109-67-1     10,000  g         
109-92-2............  Vinyl ethyl ether [Ethene, ethoxy-]................        109-92-2     10,000  g         
109-95-5............  Ethyl nitrite [Nitrous acid, ethyl ester]..........        109-95-5     10,000  f         
115-07-1............  Propylene [1-Propene]..............................        115-07-1     10,000  f         
115-10-6............  Methyl ether [Methane, oxybis-]....................        115-10-6     10,000  f         
115-11-7............  2-Methylpropene [1-Propene, 2-methyl-].............        115-11-7     10,000  f         
116-14-3............  Tetrafluoroethylene [Ethene, tetrafluoro-].........        116-14-3     10,000  f         
124-40-3............  Dimethylamine [Methanamine, N-methyl-].............        124-40-3     10,000  f         
460-19-5............  Cyanogen [Ethanedinitrile].........................        460-19-5     10,000  f         
463-49-0............  Propadiene [1,2-Propadiene]........................        463-49-0     10,000  f         
463-58-1............  Carbon oxysulfide [Carbon oxide sulfide (COS)].....        463-58-1     10,000  f         
463-82-1............  2,2-Dimethylpropane [Propane, 2,2-dimethyl-].......        463-82-1     10,000  f         
504-60-9............  1,3-Pentadiene.....................................        504-60-9     10,000  f         
557-98-2............  2-Chloropropylene [1-Propene, 2-chloro-]...........        557-98-2     10,000  g         
563-45-1............  3-Methyl-1-butene..................................        563-45-1     10,000  f         
563-46-2............  2-Methyl-1-butene..................................        563-46-2     10,000  g         
590-18-1............  2-Butene-cis.......................................        590-18-1     10,000  f         
590-21-6............  1-Chloropropylene [1-Propene, 1-chloro-]...........        590-21-6     10,000  g         
598-73-2............  Bromotrifluorethylene [Ethene, bromotrifluoro-]....        598-73-2     10,000  f         
624-64-6............  2-Butene-trans [2-Butene, (E)].....................        624-64-6     10,000  f         
627-20-3............  2-Pentene, (Z)-....................................        627-20-3     10,000  g         
646-04-8............  2-Pentene, (E)-....................................        646-04-8     10,000  g         
689-97-4............  Vinyl acetylene [1-Buten-3-yne]....................        689-97-4     10,000  f         
1333-74-0...........  Hydrogen...........................................       1333-74-0     10,000  f         
4109-96-0...........  Dichlorosilane [Silane, dichloro-].................       4109-96-0     10,000  f         
7791-21-1...........  Chlorine monoxide [Chlorine oxide].................       7791-21-1     10,000  f         
7803-62-5...........  Silane.............................................       7803-62-5     10,000  f         
10025-78-2..........  Trichlorosilane [Silane,trichloro-]................      10025-78-2     10,000  g         
25167-67-3..........  Butene.............................................      25167-67-3     10,000  f         
----------------------------------------------------------------------------------------------------------------
Note: Basis for Listing:aMandated for listing by Congress.fFlammable gas.gVolatile flammable liquid.            

[FR Doc. 94-1556 Filed 1-28-94; 8:45 am]
BILLING CODE 6560-50-P