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

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