United States	Air and Radiation	May 1993
Environmental Protection Research Triangle Park, NC 22711 EPA 453/N-93-003
Agency	(MD-13)
xvEPA IV IATICH
I Newsletter
National Air Toxics Information Clearinghouse
NATICH BBS Now On-Line*
by Vasu Kilaru, EPA Office of Air Quality Planning and Standards
If! ThlS ISSUe...	The NATICH data base can now be
accessed via EPA's Technology Transfer
EPA Einds Success with Negotiated	Network Bulletin Board System (TTN
Rulemaking...	4 BBS). The on-line service started in
March and is available to any interested
1991 TRI Data Release to Include	user for the Price of a Phone calL
New Data	6	Clearinghouse data base was
established to provide a centralized,
EPA's RIHRA Program Studies	accessible system to store and maintain
#ncer Modeling	6 Federal, State, and local air toxics pro-
gram data. It contains information on the
development and implementation of air
toxics programs, agency names and con-
tacts, and ongoing air toxics research.
State and local agencies use the Clear-
inghouse information to support the
complex decisions needed to regulate
toxic air pollutants.
The NATICH data base has been
stored on the IBM mainframe at EPA's
National Computer Center since 1984.
To streamline and improve the accessi-
bility of NATICH to its users, the Clear-
inghouse staff began adding portions of
the data base to the TTN BBS in March.
The following information is now avail-
able:
•	agency contacts;
•	program descriptions;
(continued on page 2)
Frequently Used
Acronyms
CAA - Clean Air Act Amend-
ments of 1990
HAPs - Hazardous Air Pollutants
OAQPS - Office of Air Quality
Planning and Standards
TRI - Toxics Release
Inventory
'""V 11993
Northeast States Continue to Pursue
Regional Adoption of the California
LEV Program*
States in the Northeast continue to
move forward in their efforts to adopt
and implement the California low emis-
sion vehicle (LEV) program throughout
the region in spite of continued opposi-
tion from automakers.** Maine recently
became the third Northeast State to
adopt the LEV standards (see Table 1),
joining Massachusetts and New York.
Approximately 60 percent of the vehicles
in the eight-state NESCAUM*** region
and 35 percent of vehicles in the entire
Northeast Ozone Transport Region
(OTR)**** are registered in these three
States. Other OTR States are actively
pursuing LEV programs through regula-
tory and legislative initiatives.
In October 1991, California submit-
ted a waiver request to EPA for their
LEV program that sets standards more
stringent than Federal standards.*****
(continued on page 2)
Produced in	/ AU\[p(D©
conjunction State and Territorial Air Pollution Program Administrators
with Association of Local Air Pollution Control Officials

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NATICH BBS (continued from page 1)
•	ambient air concentration guidelines
and standards;
•	pollutant research;
•	methods development;
•	nonhealth-related impacts;
•	permit information;
•	source tests;
•	ambient monitoring;
•	emissions inventories;
•	bibliographic citations; and
•	ongoing research and regulatory
development activities.
The NATICH BBS also features com-
munications options for downloading
publications lists, Clean Air Act (CAA)
information such as the list of Section
112 hazardous air pollutants (HAPs) and
physical properties of HAPs, and current
and some past issues of the NATICH
Newsletter. BBS users can also access
summary files from the EPA's Toxics
Release Inventory** System (TRIS),
which contains multimedia release infor-
mation for over 300 toxic chemicals
reported by industry under the Emer-
gency Planning and Community Right-
to-Know Act of 1986.
To implement the BBS method of
access, Clearinghouse staff condensed
the data stored to reduce data redundan-
cies and improve system performance.
For example, permit information is now
reported by pollutant or source category
(industry type, i.e., by Standard Indus-
trial Classification or SIC Code), rather
than by individual permit, which elimi-
nates duplicate data and summarizes
information for users. Similar streamlin-
ing was done for ambient air monitoring
and source testing information.
Additional functions and continued
improvement are planned for NATICH
BBS. An interactive on-line data entry
capability is scheduled to be available in
May. State and local agencies are
encouraged to use this upcoming data
entry capability to keep their information
current. In the past such data was only
entered once a year.
The OAQPSTTN is available 24
hours per day, except for Mondays fron^
8 a.m. to 12 p.m. Eastern Standard Time
when it is down for routine maintenance
and backup. Users with a computer and
modem can access the TTN by calling
(919) 541-5742. The following configura-
tion is required for the communication
software: 8 data bits, 1 stop bit, no parity,
full duplex, and a terminal emulation of
VT 100, VT 102, or American National
Standards Institute (ANSI). For further
general information about the TTN or
how to access it, call the TTN hotline,
(919) 541-5384.
T1h> Clearinghouse staff welcomes
comments and suggestions regarding
the NATICH BBS or any aspect of its
operations. Contact Vasu Kilaru, U.S.
EPA, OAQPS, MD-13, Research Triangle
Park, North Carolina 27711, or call (919)
541-0850.
*See related articles in the March 1992
and March 1993 Newsletters.
* *See related article in this issue.
line specifications. The court held that
States were not legally bound to adopt
California's gasoline specifications in
order to adopt the LEV standards.
However, the court agreed with the
automakers that New York's decision not
to adopt the California reformulated
gasoline specifications as part of the LEV
program violated the CAA because it
would necessitate the production of a
"third vehicle," which is neither a
"Federal" car nor a "California" car. The
court upheld the automaker's argument
that catalytic converters on LEVs in New
York would degrade more rapidly than
those in California, because commercial
gasoline sold in the Northeast has a
higher sulfur content than that sold in
California (sulfur restrictions are more
stringent in California than in the
Northeast States). The automakers cited
potential warranty and recall implicatio
resulting from the use of different fuel
formulations. They argued that because
(continued on page 3)
California LEV Program (continued from page 1)
In January 1993, EPA issued an uncon-
ditional waiver for California's LEV pro-
gram. Significantly, the EPA refused a
request by the automakers to make the
granting of the waiver conditional on the
commercial availability of California's
Phase 2 reformulated gasoline. Auto-
makers had raised concerns about possi-
ble warranty and recall implications asso-
ciated with the effects of differing fuel
formulations (i.e., the California refor-
mulated, Federal reformulated, or indus-
try average fuels) on engine or emission
control equipment. EPA's decision to
issue the unconditional waiver is particu-
larly important to Northeast States who
are adopting the LEV standards and have
opted to participate in the Federal refor-
mulated gasoline program. The Federal
gas program is likely to be somewhat
less stringent than California's. However,
the Northeast States view adoption of the
LEV standards in conjunction with
Federal reformulated gasoline as a signif-
icant means to control auto emissions
and improve air quality.
In July 1992, the automakers filed a
Federal law suit with six specific counts
against New York challenging several
components of the LEV regulations pro-
posed by the Department of Environ-
mental Conservation (NY DEC). In
January 1993, the court found in favor
of the automakers on four counts and in
favor of the NY DEC on two counts.
Two key issues in the suit were the
legal relationship between fuels and
emission standards and the legality of
the zero emission vehicle (ZEV) man-
date.
In regard to the first issue, the
automakers argued that New York's
decision not to adopt California's refor-
mulated gasoline program in conjunc-
tion with the LEV standards violated
the CAA. The court found in favor of
New York on this count citing the fact
that California's waiver request per-
tained only to the LEV standards and
did not address the reformulated gaso-
2

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California LEV Program (continued from page 2)
Table 1.
Chronology of California LEV Program Adoption
Date
Milestone
September 28, 1990
California adopts LEV standards
October 4, 1991
California submits request to EPA for Waiver of Federal Preemption
October 29, 1991
OTR States sign Memorandum of Understanding to adopt LEV standards throughout the Northeast
January 31, 1992
Massachusetts becomes first State to join California in adopting LEV program
March 23,1992
New York adopts LEV regulations
July 9, 1992
MVMA files suit against New York's LEV regulations in U.S. District Court in Binghampton, New York
January 8, 1993
EPA grants California an unconditional Waiver of Federal Preemption
January 22, 1993
U.S. District Court in Binghampton, New York, issues decision on New York LEV suit
January 27, 1993
Maine adopts LEV regulations
February 9, 1993
New York files Notice of Motion for Reargument and Stay of LEV decision
March 10, 1993
Maine is served with papers in LEV suit brought by the AAMA and AIAM
April 9, 1993
AAMA, AIAM, and the Massachusetts State Automobile Dealers Association file a Federal
suit in Massachusetts to block implementation of the LEV standards
tthe need to replace key emission con-
>1 components during the useful life of
the vehicle, they would have to install the
catalytic converters differently in vehicles
bound for New York than those intended
for California, consequently, requiring
the production of a third vehicle.
On the second issue, the legality of
the ZEV mandate, New York's regula-
tions are identical to California's. Both
require that 2 percent of new vehicles
produced for sale in their respective
States in 1998 must certify as ZEVs. 'Hie
mandate increases to 5 percent of new
vehicles in 2001, and to 10 percent in
2003. The court agreed with the auto-
makers that this provision in the New
York regulations violated the CAA
because it constituted a restriction in the
sale of the three other categories of Cali-
fornia vehicles (transitional LEVs, LEVs,
and ultra-LEVs). Basically, automakers
argued that the ZEV-mandated percent-
ages would restrict the sales of these
three other categories of vehicles
^fcuired under California's LEV prgram.
The State of New York has filed a
motion for reargument in hopes that the
court will reconsider its LEV decision.
Air quality officials in New York and other
OTR States believe that the court decision
is flawed and that it will be overturned
based on a reexamination of existing
information. In fact, a special commission
appointed in Massachusetts to review that
State's LEV regulations voted in early
March not to change their regulations.
However, automakers filed a Federal suit
to block implementation of the LEV stan-
dards in Massachusetts in April. Also, the
Maine Board of Environmental Protection
adopted the LEV program after the court
ruling in New York. Plaintiffs opposed to
Maine's LEV program have already
served the State with papers to initiate a
lawsuit. In addition, the legislatures in
both New Jersey and Maryland have
recently passed LEV bills since the New
York court decision.
For more information, contact Arthur
Marin at NESCAUM at (617) 367-8540.
*See related articles in the March 1990
and January 1992 Newsletters.
* *The Motor Vehicle Manufacturers
Association (MVMA) originally repre-
sented both domestic and foreign auto-
makers. It separated after legal action
was initiated into the American
Automobile Manufacturers Association
(AAMA) and Association of International
Automobile Manufacturers (AIAM).
* * *The eight States comprising the
Northeast States for Coordinated Air Use
Management (NESCAUM) region are
Connecticut, Maine, Massachusetts, New
Hampshire, New Jersey, New York, Rhode
Island, and Vermont.
*** *The OTR includes the eight
NESCAUM States, Pennsylvania,
Delaware, Maryland, Virginia, and the
District of Columbia.
**** *Section 209(b) (1) of the 1990
Clean Air Act Amendments (CAA) pro-
vides that any State that adopted motor
vehicle emission standards before
March 30, 1966, that are equal to or more
stringent than Federal standards can
request and receive an EPA waiver certify-
ing this. California is the only State that
meets this eligibility requirement for
receiving waivers.
3

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EPA Finds Success with Negotiated Rulemaking
Although the EPA follows a strict
public notice and participation strategy in
the development of regulations, approxi-
mately 80 percent of its resulting
"major" regulations are subject to litiga-
tion, and implementation may be delayed
for years. To see if there was a better
way to develop some of the more than
200 regulations normally in the works,
the EPA established the Regulatory
Negotiation Project in 1982. Its goal was
to investigate the potential for using
negotiation in developing better pro-
posed rules and reducing the nearly
inevitable uncertainty and delay in imple-
mentation that accompany litigation.
A regulatory negotiation (or "reg
neg") is an innovative way to develop
proposed rules. A federally chartered
advisory committee is convened with
representatives from all affected parties
including industry, State and local offi-
cials, environmental groups, and the
EPA. The members negotiate on behalf
of their constituencies and attempt to
reach consensus on exact language or
agreement on core conceptual principles
that can be used as the basis of a pro-
posed rulemaking. EPA agrees to use
the consensus as the basis of its pro-
posed rule. The negotiations are chaired
by a neutral facilitator whose role is to
keep the parties moving toward consen-
sus. Once a proposed rule is published,
the negotiation is completed, and the
Administrative Procedures Act and other
relevant statutes govern the remainder of
the rulemaking process.
EPA views regulatory negotiation as
a win-win strategy. The Agency gains in
developing a more environmentally effec-
tive, innovative, and pragmatic rule,
which reduces litigation costs and delay
in rule implementation. The regulated
industries are able to participate more
fully in the development of a rule, reduc-
ing uncertainty about what will be
required and leading to rules that are
more understandable. State and local
agencies, often responsible for imple-
menting programs to enforce EPA rules,
are able to build in administrative needs.
Environmental and public interest
groups concerned about reducing pollu-
tants in the environment and represent-
ing the "little guy," are all able to voice
their concerns and impact the propose^
regulations more fully and openly than
under traditional informal notice and
comment rulemaking.
Since establishing the program,
nearly a dozen regulatory negotiations
have been completed with a strong suc-
cess record. Only three did not achieve
final consensus, and for the two rules
where litigation occurred in spite of the
negotiation, the cases were decided in
EPA's favor. Table 1 summarizes the sta-
tus of these negotiated rules.
It is not feasible for the Agency to
conduct negotiations for all preproposal
rules under development. EPA's Regu-
latory Negotiation Project, directed by
Chris Kirtz, screens rules to identify
those that are good candidates for nego-
tiation. Criteria include an identifiable
and limited set of issues, a reasonably
limited and discernable balance of inter-
est groups, and a data base sufficient for
meaningful discussion of issues. A nego-
tiation may be initiated if the Agency
believes it is to mutual advantage and
that the interested parties can negotiati-
(continued on page 6)
Table 1.
EPA Negotiated Rulemaking Status as of April 1993
Rules
Standard/EPA Office
Negotiation Status
Rulemaking Status
Notes
Nonconformance Penalties
for Heavy-Duty Trucks
CAA/Office of Mobile
Sources (OMS)
First met 6/84
Consensus reached 10/84
Proposed 3/85
Promulgated 8/85
Only 13 comments on proposal;
all supportive. No litigation.
Emergency Pesticide
Exemptions
Federal Insecticide,
Fungicide & Rodenticide
Act (FIFRA)/Office of
Pesticide Programs (OPP)
First met 8/84
Consensus reached 1/85
Proposed 4/85
Promulgated 1/86
19 comments received.
No litigation to date.
Farmworker Protection
Standards
FIFRA/OPP
First met 11/85
Committee unable to achieve
consensus but continued
informally.
Proposed 7/88
Promulgated 8/92
100's of comments received
and reviewed before pro-
mulgation.
Woodburning Stoves
New Source Performance
Standard/OAQPS
First met 3/86
Consensus reached 8/86
Proposed 2/87
Promulgated 2/88
50 comments received. 1
No litigation to date.
(continued on page 5)
4

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Negotiated Rulemaking (continued from page 4)
Table 1.
EPA Negotiated Rulemaking Status as of April 1993 (continued)
Rules
Standard/EPA Office
Negotiation Status
Rulemaking Status
Notes
Resource Conservation and
Recovery Ad (RCRA) Minor
Permits Modification
RCRA/Office of Solid
Waste
First met 9/8(i
20 of 21 members
concurred 2/87
Proposed 9/87
Promulgated 9/88
55 comments received.
No litigation to date.
Underground Injection of
I iazardous Wastes
Hazardous and Solid Waste
Amendments of 1984/Office
of Drinking Water
First met 9/8(i
Good agreement but not
total consensus in 3/87
Proposed 8/87
Promulgated 7/88
30 comments received.
Litigation did not involve the
use of reg neg and was decided
in EPA's favor.
Asbestos in Schools
Asbestos Hazard
Emergency Response Act
of 1986/Office of Toxic
Substances (OTS)
First met 2/87
20 to 24 members came to
agreement 2/87
Proposed 4/87
Promulgated 10/87
130 comments received.
Litigation by nonsignatories.
Ruled in EPA's favor.
Fugitive Emissions from
Equipment I-eaks
National Emission
Standard for Hazardous
Air Pollutants
(N ESHAP) /OAQ PS
First met 9/89
Consensus reached 10/90
Proposed 12/92
Promulgation expected
Included in Hazardous
Organic NESHAP proposal;
one of the first maximum
achievable control tech-
nology (MACT) standards.
I^ead-Acid Battery Recycling
Toxic Substances
Control Act/OTS
First met 1/91
EPA suspended negotiations
5/91 to develop additional
cost and risk estimates.
Rulemaking suspended
EPA decided risk/benefits
gain insufficient to regulate
at this time.
Oxygenated and
Reformulated Fuels
CAA/OMS
First met 3/91
Consensus reached 8/91
EPA issued rules to use
more ethanol in 10/92
President Bush ordered EPA
to reconsider rules to provide
greater use of ethanol in 9/92;
further action anticipated.
Coke Oven Batteries MACT
Standards
NESHAP/OAQPS
First met 2/92
Consensus reached 10/92
Proposed 12/92
A smaller group within the
committee drafted rule and
preamble.
Disinfection By-Products
Safe Drinking Water
Act/Office of Water
First met 11/92
Completion expected 9/93
Pending outcome of
negotiation
Possible risk trade-offs,
complex technological issues
are unique.
Architectural and Industrial
Maintenance Coatings
CAA/OAQPS
F irst met 10/92
Completion expected 9/93
Pending outcome of
negotiation
First consumer product
rule/negotiation under § 183(e).
Revision of Hazardous
Waste Manifest
RCRA/Office of Policy
Planning and Evaluation
First met 10/92
Completion expected 9/93
Pending outcome of
negotiation
Negotiation result of
ASTSWMO3 petition to
standardize varying State
manifests.
"Association of State and Territorial Solid Waste Management Officials.
5

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Negotiated Rulemaking (continued from page 4)
in good faith to resolve the issues with-
out compromising fundamental or stated
goals, principles, or values.
The public is encouraged to partici-
pate by suggesting candidate rules for
regulatory negotiation. Candidate rules
recommended by the public will be eval-
uated by the same criteria.
For information regarding any of the
specific negotiations summarized in
Table 1 or for general information, rec-
ommendations, or comments, contact
Chris Kirtz, Director, Regulatory
Negotiation Project (PM-223Y), U.S.
EPA, 401 M Street, S.W., Washington,
D.C. 20460, or call (202) 260-7565.
1991 TRI Data Release to Include New Data
by William Wallace, EPA Office of Pollution Prevention and Toxics
EPA's Office of Pollution Prevention
and Toxics (OPIT) has scheduled
release of the 1991 data in its Toxics
Release Inventory (TRI) data base in late
May. The 1991 release includes new
data on source reduction and recycling
activity from facilities required to file
Form R for Reporting Year (RY) 1991
Oanuary 1 to December 31, 1991).
This is the fifth year that information on
routine and accidental releases of toxic
chemicals to the environment has been
available.
The Pollution Prevention Act of 1990
requires eight new types of data to be
reported for RY 1991 on the TRI Form
R, under Part II, Section 8, "Source
Reduction and Recycling Activities." All
facilities subject to the mandatory TRI
reporting requirements must include the
following information on a facility-by-
facility basis for each toxic chemical:
• quantities entering waste streams
prior to treatment, recycling, or dis-
posal or that are otherwise released
to the environment, the percentage
change from the previous year, and
similar estimates for the next 2 years;
•	quantities recycled, similar estimates
for the next 2 years, and the recy-
cling process used;
•	the percentage change in the quantity
recycled from the previous year to
the current reporting year;
•	source reduction practices;
•	techniques used to identify source
reduction opportunities;
•	a production index (i.e., the ratio of
production in the reporting year to
production in the previous year);
•	amounts of chemicals released
through catastrophic events, remedial
actions, or other one-time events not
associated with production processes;
and
•	the amount of chemical that is treated
and the percentage change from
the previous year.
The first reports containing this
expanded information were due to EPA
and the States by July 1, 1992. At the
close of business on April 8, 1993, the
Agency's mainframe TRI data base was
frozen (no additional changes were per-
mitted) for one week to produce com-
puter tape extracts of the data. These
extracts were provided to organizations
including the National Library of
Medicine (NLM), Government Printing
Office (GPO), and National Technical
Information Service (NTIS) for creation
of publicly available data products, such
as compact disks or computer diskettes
with data available on a State-by-State
basis, and reports including the com-
bined national report, the 1991 Toxics
Release Inventory Public Data Release
(EPA 700S-93-002).
All RY 1991 Form R report data
received through February 19, 1993, are
included in the public data release. Data
quality assurance activities continued
until the freeze date and included resolv-
ing outstanding Notices of Non-Compli-
ance, correcting any data entry errors,
investigating invalid codes and other pos-
sible data discrepancies, and entering
Form R revisions received from facilities.
For further information, contact
Steve Newburg-Rinn or Ruby Boyd at
U.S. EPA, OPPT, TS-793, 401 M Street,
S.W., Washington, D.C. 20460, or call
(202) 260-3757.
EPA's RIHRA Program* Studies Cancer Modeling
by Marc J. Mass, EPA Health Effects Research Laboratory
This is the second article in a series
that focuses on current activities supported
by RIHRA to advance the scientific basis
for risk assessments for all regulatory
programs.
In 1986, EPA issued Carcinogen Risk
Assessment Guidelines that supported
the use of the linearized multistage
(LMS) model as essentially the default
mathematical procedure for performing
high-dose to low-dose extrapolations in
carcinogen risk assessments. However,
the 1992 draft revisions to these guide-
lines give substantial latitude to use
other models. The updated guidelines
will apparently stress that the mecha-
nism of carcinogenesis should be consid-
ered when determining the quantitative
methods to use when extrapolating from
high to low doses. The revised guide-
lines also allow the use of models other
than the LMS when sufficient information
regarding a carcinogen's mechanism of
action permits mathematical description
that is concordant with the biological
events in the carcinogenesis process.
EPA's Research to Improve Health
Risk Assessments (RIHRA) program hcg
been aware of the Agency's desire to ™
(continued on page 7)
6

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RIHRA Program (continued from page 6)
plore the utility of low-dose extrapola-
n models other than the LMS model
for carcinogen risk assessments, espe-
cially biologically based dose-response
(BBDR) models. Non-BBDR models
such as the LMS (a modification of the
Armitage-Doll model**) use as variables
only the dose and tumor incidence.
Therefore, such non-BBI)R models do
not consider other factors that may dras-
tically affect tumor incidence over time
such as the number of cells susceptible
to carcinogenic insult at the time of expo-
sure, the rate at which
carcinogen-induced changes occur in
these cells, the growth rates of these
altered (premalignant) cells into tumors,
and the rate at which these cells die.
The Moolgavkar-Knudson (MK)
multistage model is a BBDR model that
considers the additional parameters
above. Researchers believe it may be
capable of making more accurate risk
extrapolations than the LMS model at
low doses. The MK model has been
used to predict tumor incidences in
^>man populations where there are
Ranges in the age-related incidences of
cancer, particularly in tumor types where
hormonal fluctuations cause cell prolifer-
ation rates to change over time in the tar-
get organ. Non-BBDR models typically
were unable to predict tumor incidences
accurately in such tissues. Also, the MK
model allows consideration of the effects
of carcinogens that operate by genotoxic
mechanisms (carcinogen-induced
changes in DNA), or by nongenotoxic
mechanisms (effects on cellular differen-
tiation processes).
EPA's Health Effects Research
Laboratory (HERL) has established a
cooperative research agreement with
internationally known cancer researcher
Dr. Henry Pitot at the University of
Wisconsin's McArdle Laboratory for
Cancer Research to experimentally
derive the parameters needed to use the
MK model with a rat liver carcinogenesis
protocol. The data that the laboratory
generates is being used by EPA'S Office
of Health and Environmental Assess-
ment (OHEA) to test how well the MK
model performs high- to low-dose extrap-
olations.
Deriving parameters for the MK can-
cer incidence model requires the use of
experimental protocols in which early,
carcinogen-induced changes can be read-
ily recognized. Relatively few animal car-
cinogenesis systems meet this criterion.
A rat liver carcinogenesis protocol was
chosen because it has been used produc-
tively for many years to understand steps
in the carcinogenesis process. In a sim-
plified scheme, rat liver cells exposed to
carcinogens grow into a mass called an
altered hepatic focus (AHE) that is
thought to eventually give rise to a
tumor. By counting the number of AHFs
after a dose of carcinogen, measuring the
rate of growth (or recession) of the AHE,
and the number of resultant tumors com-
pared to the AHE, it is possible to derive
some of the parameters of the MK can-
cer incidence model.
Will other high- to low-dose BBDR
extrapolation models be useful to the
Agency in performing more accurate
quantitative carcinogen risk assess-
ments? EPA researchers believe so and
OHEA scientists have already compared
BBDR and non-BBDR high- to low-dose
extrapolation models using experimental
data from a rat liver carcinogenesis study
using dinitrotoluene. They showed
clearly that the use of different extrapola-
tion models would affect unit risk esti-
mates for dinitrotoluene exposure. Such
advances made in BBDR low-dose
extrapolation modeling for cancer may
benefit risk assessments used in all areas
of regulation.
For further information on this
RIHRA project, contact Marc J. Mass,
Ph.D., U.S. EPA Carcinogenesis and
Metabolism Branch (MD-68), HERL,
Research Triangle Park, North Carolina
27711. For further information on
RIHRA, contact John Vandenberg, Ph.D.,
RIHRA Director, at the same address
except for MD-51, or call (919) 541-4527.
*See related articles in the July 1991 and
January 1993 Newsletters.
* *The Armitage-Doll model was among
the earliest quantitative risk assessment
models developed, and was used in the
1950s to study the relationship of cigarette
smoking and lung cancer.

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'Hie NA T1CH Newsletter is published six limes a year by Ihe National Air Toxics Information Clearinghouse. The
Newsletter is prepared by Radian Corporation under EPA Contract Number 68-1)1-0125, Work Assignment 2-14. The EPA
Editor is laurel Driver, EPA Office of Air Quality Planning and Standards, Research Triangle Park, North Carolina 27711,
Telephone (919) 541-2859. The Radian Project Director is Linda Cooper, Radian Corporation, P.O. Box Box 13000, Research
Triangle Park, North Carolina 27709, (919) 541-9100.
The Newsletter is distributed free of charge. To report address changes, write Meredith Haley, Radian Corporation, P.O.
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BULK RATE
Postage and Fees Paid
E.P.A.
G-35
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Environmental Protection Agency
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$300
EPA 463/N-93-003
May 1993

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