The Role of Risk Assessment In Title III Outlined *
by Fred Hauchman, EPA Health Effects Research Laboratory
NATICH
NEWSLETTER
&ERA 453N92009
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
®¥£\[?[P£\ U
State and Territorial Air Pollution Program Administrators
Association of Local Air Pollution Control Officials
Produced by the National Air Toxics Information Clearinghouse January 1992
Title III of the 1990 Clean Air
Act Amendments (CAA) establishes
a control technology-based program
to reduce stationary source emis-
sions of hazardous air pollutants
(HAPs). The new air toxics provi-
sions avoid some of the difficulties
experienced under the previous
Federal regulatory program for
toxic air pollutants by deferring
formal quantitative risk assess-
ments until a post-control evalua-
tion phase. While this approach
represents a change from the risk
assessment-based approach of the
1977 CAA, information on the
health and environmental effects of
HAPs will play an important role
in the decision-making process
under the new legislation.
The Great Waters Program,
required by Section 112(m) of the
Clean Air Act Amendments of
1990, has made significant pro-
gress in its first year. The coopera-
tive EPA/National Oceanic and At-
mospheric Administration (NOAA)
program is charged with identify-
ing and assessing the extent of at-
mospheric deposition of hazardous
air pollutants (HAPs) to the Great
Lakes, Chesapeake Bay, Lake
Champlain, and coastal waters (see
Figure 1). Specific goals of the pro-
gram that will culminate in a report
Provisions with Risk Assessment
Activities Listed
Several provisions in Title III
involve risk-related activities that
range in complexity from hazard
assessments of individual chemi-
cals to detailed source-specific risk
assessments that consider health
and environmental effects and ex-
posure. These provisions include:
•	establishing lesser quality
emission rates to define ma-
jor sources (Section 112(a));
•	revising the list of HAPs
(Section 112(b));
•	establishing, prioritizing, and
revising the list of source
categories for regulation (Sec-
tion 112(c) and (d));
•	recommending additional
to Congress in 1993 (with biannual
updates thereafter) include:
•	describing how atmospheric
deposition contributes to total
pollutant loading;
•	identifying HAP-caused en-
vironmental and human health
effects and listing the HAPs
sources;
•	determining whether HAP
loadings cause or contribute
to water quality violations or
violations of the Great Lakes
Water Quality Agreement; and
(continued on page 3),
legislation to address the risk
remaining after controls (Sec-
tion 112(f));
•	ranking of HAPs to use in
source modification decisions
(Section 112(g));
•	identifying HAPs of concern
for the Early Reduction Pro-
gram (Section 112(i));
•	developing the urban area
source strategy (Section
112(k));
•	conducting special studies
like the Great Lakes and
Coastal Waters Study (Sec-
tion 112(m)); and
•	developing chemical accident
prevention regulations and
guidance (Section 112(r)).
(continued on page 2)
Program Update
In This Issue...
Illinois' Air Tbxics Selections
Process Described 4
OAQPS Releases Emission
Estimation Resources 6
OHE A Adds Air Component
to Integrated Modeling
Evaluation System 7
Eastern States Pursue Cali-
fornia Auto Standards 8
Air RISC Updates
DireC&ry" 10
Clean Air Act Activities: Great Waters
by Carol Jones, EPA Office of Air Quality Planning and Standards

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Risk Assessment (continued from page 1)
Other activities mandated by
Title III include the National
Academy of Sciences' (NAS) study
to review EPA's risk assessment
methodology (Section 112(o)) and
the EPA report to Congress on
methods used for assessing the
risk associated with exposure to
HAPs (Section 112(f)). Additional-
ly, Section 303 of Title III estab-
lishes the Risk Assessment and
Management Commission, which
must evaluate the policy implica-
tions of risk assessment and risk
management under Federal laws to
prevent cancer and noncancer
health effects resulting from ex-
posure to hazardous substances.
Risk Assessment Issues Described
The successful implementation
of Title III will require EPA to ad-
dress provision-specific and cross-
cutting risk assessment issues.
These issues relate to the widely
recognized problem that substan-
tial gaps exist in the scientific data
bases that serve as the foundation
for risk assessment. The major
issues can be grouped into two fun-
damental and interrelated prob-
lems in risk assessment: (1) the
limited available information on
health effects, environmental ef-
fects, and exposures; and (2) the
need for new and improved risk
assessment methodologies.
The health and environmental
effects data for many HAPs are in-
adequate. A lack of sufficient data
exists in such areas as carcinogeni-
city, reproductive and developmen-
tal toxicity, pulmonary toxicity,
neurotoxicity, and immunotoxicity.
Inadequate experimental dose-
response data may preclude the
quantitative assessment of cancer
risk for many of the potential car-
cinogens listed. Major data gaps
exist with regard to the health ef-
fects associated with short-term
exposure and the adverse environ-
mental effects on aquatic life,
wildlife, and other natural resources.
There is also a need for additional
information on pollutant sources,
ambient exposure levels, and at-
mospheric transformation pro-
cesses and products.
Uncertainty in the risk assess-
ment process is related not only to
the problem of inadequate health
and exposure data, but also to the
lack of understanding about the
underlying physical, chemical, and
biological processes that determine
exposures and effects. Information
on these processes provides the
scientific basis for many of the
methods and models that are used
in risk assessment, such as in ex-
trapolating data from animals to
humans, from high dose to low
dose, or from one route of ex-
posure to another. Areas where
new or improved risk assessment
methodologies are needed include:
•	dose-response models for
cancer and noncancer effects,
including predictive models
of dose (i.e., physiologically
based pharmacokinetic
models) and of effects
(biologically based dose-
response models);
•	methods for assessing non-
cancer risks at levels above
the inhalation reference con-
centration (RfC);
•	methods for assessing cancer
and noncancer risk from
short-term exposures;
•	improved methods for assess-
ing exposure to mixtures of
chemicals;
•	improved methods for ex-
posure assessment, consider-
ing such factors as indirect
exposures, indoor/outdoor
relationships, human activity
patterns, and atmospheric
transformation processes; and
•	methods for ecological risk
assessment.
The availability of adequate
data and the use of scientifically
defensible risk assessment method-
ologies are issues in many of the
Title III provisions mentioned
above. For example, assessing the
relative risk of all of the 189 car-
cinogens and noncarcinogens for
Section 112(g) may be difficult
with limited health data. The ur-
ban area source program and the
(ireat Lakes and Coastal Water
program require EPA to identify
the most important pollutants of
concern, identify sources of pollu-
tion, and develop effective control
strategies. To fulfill these require-
ments, sufficient health and en-
vironmental effects data for speci-
fic pollutants will be needed. New
and improved risk assessment
methodologies will be particularly
useful in conducting the detailed
residual risk assessments that are
required under the residual risk
provision.
The EPA and NAS studies are
expected to address many of the
issues described above. Issue resol-
ution through continued research
and methods development will in
part determine the successful im-
plementation of Title III.
For additional information,
contact Fred Hauchman, U.S. EPA
Health Effects Research
Laboratory, Research Triangle
Park, North Carolina 27711 or
(919) 541-3893 or (FTS) 629-3893,
or Dennis Pagano, U.S. EPA Office
of Air Quality Planning and Stan-
dards, Research Triangle Park,
North Carolina 27711 or (919)
541-0502 or (FTS) 629-0502.
*Adapted from a paper by Fred
Hauchman published in "Air Toxics
Issues in the 1990s - Policies,
Strategies, and Compliance," Pro-
ceedings of the International Air
and Waste Management Association
Conference held April 3-5, 1991,
Pittsburgh, PA.
2

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Great Waters Program (continued from page 1)
• describing regulatory revisions
needed to assure protection of
the waters.
Activities to date have focused
on determining the issues, science
and research methods regarding
atmospheric deposition to aquatic
systems, identifying available in-
formation sources, and preparing a
program strategy, which is under-
going final EPA internal review.
State representation has been
valuable in the development of the
strategy. The Great Waters Program
has prepared three draft background
reports - a literature review, data
inventory, and chemical assessment
- which are also under review.
The literature review is a compre-
hensive overview of the "state of
the knowledge" on atmospheric
deposition to aquatic systems. The
data inventory lists data collection
efforts that could be incorporated
into the Great Waters program.
The chemical assessment identifies
Title III chemicals that are, or are
likely to be, problematic when de-
posited into aquatic systems, based
on aquatic toxicity, human toxicity,
bioaccumulation potential, and per-
sistence. The program has also
established high priority tasks.
One example is the basic character-
ization of processes such as dry de-
position mechanisms or the influ-
ence of an urban plume on total
deposition.
Plans for the first report to
Congress are now underway. The
report will present a summary of
the state of knowledge on atmos-
pheric deposition to aquatic systems,
especially loading, sources, and ef-
fects; the strategy for developing
data currently unavailable; progress
made to date in achieving objectives;
and any conclusions that can be
drawn considering available data.
For further information on the
Great Waters Program, contact
Melissa McCullough, U.S. EPA,
PAB, at (919) 541-5646 or (FTS)
629-5646.
Figure 1.
Waters included under Section 112(m) and from which monitoring sites will be selected.
Pugct Sound
Cisco Bay, MK
Massachusetts/
Cape Cod Bays, MA
Buzzards Bay, MA
Nuraganiett Bay, MA
l^ong Island Sound, CT and NY
New York/
New Jersey Harbor, NY and NJ
Delaware Bay, NJ and PA and DH
Albemarle-Pamlico Sounds, NC
Indian River Lagoon, FL
Tamp^Bay, FL
Saraspu Bay, FL
3

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Illinois' Air Toxics Selection Process Described
by Dr. Thomas Hornshaw, Illinois Environmental Protection Agency
In 1987, Illinois began its toxic
air contaminant (TAC) control pro-
gram by directing the Illinois En-
vironmental Protection Agency
(IEPA) to develop a list of chemi-
cals that met the Illinois General
Assembly's definition of TAC and
were not controlled at the Federal
level. TACs are defined as "any air
contaminant which may cause or
significantly contribute to an in-
crease in serious irreversible or in-
capacitating reversible illness, or
may pose a significant threat to
human health or the environment."
Listing criteria are proposed in
Part 232 "Toxic Air Contami-
nants" of the Illinois Administra-
tive Code, which is being con-
sidered by the Illinois Pollution
Control Board. The fourth hearing
was held on January 7, 1992.
Carcinogens are automatically
listed and include chemicals con-
sidered to be known or probable
human carcinogens by the American
Conference of Governmental In-
dustrial Hygienists, the Interna-
tional Agency for Research on
Cancer, the National Toxicology
Program, and those listed by the
U.S. EPA's Integrated Risk Infor-
mation System. Noncarcinogens
are selected through a toxicity
scoring process.
The Toxicity Score is divided
into two separate determinations of
a chemical's potential to cause
adverse noncarcinogenic effects:
the Acute Lethality Score (range 0-
3), which estimates the potential of
a chemical to contribute to an in-
crease in sudden death; and the
Chronic Toxicity Score (range 0-6),
which estimates the potential of a
chemical to contribute to an in-
crease in serious irreversible or in-
capacitating reversible illness. The
toxicity score is the sum of the two
scores; chemicals with toxicity
scores of 3 or higher are listed.
The Scoring Process Described
The Acute Lethality Score is
derived from the acute LC50 and
LD50 data on rats that are listed in
the Registry of Toxic Effects of
Chemical Substances (RTECS).
The preferred route of exposure is
inhalation. Scores corresponding to
the LC50 and LD50 results are
given in Table 1. The Chronic Tox-
icity Score requires that a subacute
or chronic toxicity study be selected
upon which the score will be bas-
ed. This study will yield a Lowest
Toxic Dose Score and a Severity of
Effects Score, which are multiplied
together to determine the Chronic
Toxicity Score.
The Lowest Toxic Dose Score
is based on the Lowest Observed
Adverse Effect Level (LOAEL),
which is the lowest dose determin-
ed in the study to have caused an
adverse effect. The LOAEL is
assigned a score according to Table
2. The Severity of Effects Score is
derived from a matrix that encom-
passes both the organ and organ
system affected and the severity of
the effect on that organ/organ
system. It weights the Chronic
Toxicity Score so that chemicals
producing serious health effects on
vital organs or organ systems
receive the highest scores. Three
categories of organs/organ systems
are considered:
• those for which impairment
or loss is fatal or usually can-
not be compensated for by
the body; which prevent the
transmission of genetic
material; or which produce
an adverse reproductive out-
come (Category I);
(continued on page 5)
Table 1.
Acute Lethality Scores
Inhalation Concentration

(LCs(l)a (mg/m !)
Acute Lethality Score
<500
3
500-4,999
2
5,000-50,000
1
>50,000
0
If the above data are not available:
Oral Doseb (LD;o)

(mg/kg)
Acute Lethality Score
<50
3
50-499
2
500-5,000
1
>5,000
0
a Listed concentrations were derived from the Superfund
Amendments and Reauthorization Act (SARA). Section 313, which designates LC-0 con-
centrations of less than 500 mg/m:t as "Extremely Hazardous."
b Listed concentrations were adapted from the EPA Pesticide Signal Word Labeling
Category Criteria of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA).
4

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Illinois' Air Toxics Selection (continued from page 4)
•	those for which impairment
or loss may be fatal but that
can be compensated for by
drug or replacement therapy;
which adversely affect the
immune function that may be
life threatening; which
change the composition or
function of blood constituents
that may be life threatening;
or which cause certain fetotoxic
effects (Category II); and
•	those for which impairment
or loss is not life threatening
but may result in functional
or emotional handicaps;
which adversely affect the
immune function but are not
life threatening; and which
change the composition or
function of blood that are not
life threatening (Category III).
The severity of the effect is
evaluated for each organ/organ
system according to four levels:
serious irreversible or reversible
effects, and non-serious irreversi-
ble or reversible effects (see Table
2). These are defined as follows:
•	A serious effect is an in-
capacitating condition, or a
condition that significantly
contributes to an increase in
mortality.
•	A non-serious effect is a non-
incapacitating condition, or a
condition that is unlikely to
contribute to an increase in
mortality.
•	An irreversible effect is one
that is permanent, or would
require medical treatment to
correct.
•	A reversible effect is a tem-
porary effect.
Examples of serious, irreversi-
ble, Category I effects that would
receive the highest score of 6 are
lung or liver failure and severe cen-
tral nervous system depression. At
the other end of the spectrum,
health effects that would be con-
sidered non-serious, reversible,
Category III effects that would be
assigned a score of 1 include rever-
sible lesions of nasal mucosa and
low white or red blood cell counts.
How Toxicity Scores Are Derived
The derivation of toxicity
scores for cyclohexanone ex-
emplifies the process. The Acute
Lethality Score is based on rat in-
halation LC50 of 32,111 mg/m3
reported in the RTECS data base.
Therefore, the Acute Lethality
Score is 1. The Chronic Toxicity
Score is the product of the Lowest
Toxic Dose Score, 2/3, from a 31.3
mg/kg/day dose that caused barely
demonstrable liver and kidney
degeneration in rabbits via inhala-
tion, and the Severity of Effects
Score of 4 because the degenera-
tion was regarded as a Non-serious,
Reversible, Category I effect. The
result is (2/3 x 4), or 2 and 2/3.
The Toxicity Score is (1 + 2 and
2/3), or 3 and 2/3, therefore,
cyclohexanone would be a listed
chemical.
Applying the scoring process
to a master list of chemicals, IEPA
has produced a tentative list of 266
TACs. The Illinois regulations are
due to be finalized September 26,
1992, which will formally create
the TAC list.
For more information on the
scoring process, contact Dr.
Thomas Hornshaw, Illinois En-
vironmental Protection Agency,
(217) 785-0830.
Table 2.
The Chronic Toxicity Score Derivation
Lowest Toxic Dose Scores'
LOAEL Values

(mg/kg/day)
Lowest Toxic Dose Score
<5
1
5-50
2/3
>50
1/3
Severity of Effects Scores'*

Organ Category
Level of Effect
I II III
Serious Irreversible
6 .5 4
Serious Reversible
5 4 3
Non-serious Irreversible
4 3 2
Non-serious Reversible
3 2 1
No Observed Effect
0 0 0
a This numeric score is based upon best professional judgment, in order to weight the lowest
dose of a contaminant that causes an observable adverse health effect. It is derived from this
relationship to LOAEL values.
b The listed scores were adapted from EPA's Noncancer Risk Work Group, and appear in Ap-
pendix 2 of "Unfinished Business: A Comparative Assessment of Environmental Problems."
The values were adapted to the scoring process in order to relate the seriousness of an affect
with the relative importance of an organ or organ system.
5

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OAQPS Releases Emission Estimation Products
The Emission Inventory Branch
(EIB) in EPA's Office of Air Quality
Planning and Standards (OAQPS)
has recently released a new emis-
sion estimating product, the 1991
editions of the SPECIATE and
XATEF data management soft-
ware, and a report on locating and
estimating styrene emissions.
Air CHIEF CD-ROM Released
The EIB's newest emission
estimating product is the Air
Clearinghouse for Inventories and
Emission Factors (Air CHIEF)
Compact Disk-Read Only Memory
(CD-ROM). Air CHIEF provides
information on estimating air emis-
sions of criteria and toxic pollu-
tants from selected sources. Air
CHIEF contains data from four
sources: AP-42; the "Locating and
Estimating" series of reports; the
VOC/PM Speciation data base
management system (SPECIATE);
and the Crosswalk/Air Toxic Emis-
sion Factor data base management
system (XATEF). Air CHIEF pro-
vides information on air emissions
and emission factors from a single
data base, rather than having to use
25 reports and two data base man-
agement systems. The system is de-
signed for easy access and retrieval
of emission estimates by pollutant
or source description. Using the
CD-ROM will assist air pollution
control agencies and others in lo-
cating potential sources of air toxics
and estimating resulting emissions.
The Beta version of Air CHIEF
is being released with a user's
manual. The EIB welcomes com-
ments, which should be directed to
Anne Pope (see below). Air CHIEF
will be updated annually, with the
next update scheduled for release
in spring of 1992.
Users will need an IBM PC1M
compatible computer with an EGA
or VGA monitor, MS-DOS™ version
3.0 or higher, 640 KB free RAM, 2
MB expanded memory, a CD-ROM
drive, an interface card, and Micro-
soft DOS CD-ROM Extensions
(MSCDEX).
1991 Versions of XATEF and
SPECIATE Released
The 1991 editions of the
VOC/PM speciation data base
management system (SPECIATE)
Version 1.4 and the Crosswalk/Air
Toxic Emissions Factor data base
management system (XATEF) Ver-
sion 1.2 are now available, which
contain new data and corrections.
Both systems are for the same
users as the Air CHIEF CD- ROM,
are updated annually, and provide
easy access and retrieval of emis-
sion estimation data by pollutant
source description.
Fifteen new VOC profiles for
jet engines were added to the 1991
edition of SPECIATE, which con-
tains about 700 species profiles for
both VOCs and PM. By applying
the species profiles to either total
VOC or PM emission estimates,
the weight percentage of specific
VOCs or the elemental composi-
tion of PM can be estimated for
the source categories covered in
the system. About 1,700 new emis-
sion factors for 46 new pollutants
and 21 new industrial processes
were added to the 1991 edition of
XATEF, which contains toxic air
pollutant/source crosswalk data
and air toxic emission factors. The
crosswalk data identify the types
of compounds that may be poten-
tially emitted from a source cate-
gory. The crosswalk indicates the
potential for a pollutant/source
association based on literature in-
formation, existing inventories, and
other available data. The cross-
walk data in XATEF include pollu-
tant names, Chemical Abstract
Service (CAS) Numbers, Standard
Industrial Classification (SIC)
Codes, and emitting Source Class-
ification Codes (SCCs). XATEF
also contains 7,600 emission fac-
tors for over 300 compounds and
more than 500 source categories.
The systems are designed for
use on an IBM PCTM compatible
computer. They are each distributed
on one 5V4-inch high-density dis-
kette, or they may be downloaded
from the Clearinghouse for Inven-
tories and Emission Factors
(CHIEF) Bulletin Board System
(BBS), a sub-board of the OAQPS
Technology Transfer Network* A
user's manual for each system ac-
companies a system diskette and
explains the uses and limitations of
the data and the use of the data
management software.
The SPECIATE and XATEF
data bases require an IBM PCIVI
compatible machine with MS-DOS1M
version 3.0 or later, 640 KB of free
RAM, and a high- density 5'A-inch
external disk drive. SPECIATE re-
quires a fixed disk with at least 8
MB of storage, and XATEF, at
least 20 MB of storage. These data
bases can be downloaded from the
CHIEF BBS.
Details appear below on obtain-
ing the SPECIATE and XATEF
user's manuals entitled Volatile
Organic Compound (VOC)/ Par-
ticulate Matter (PM) Speciation
Data System User's Manual, Ver-
sion 1.4 (EPA-450/4-91-027) and
Crosswalk/Air Toxic Emission Fac-
tor Data Base Management System
User's Manual, Version 1.2
(EPA-450/4-91- 028).
Styrene Emission Report Published
The EIB has recently publish-
ed the report Locating and Esti-
mating Air Emissions from Sources
of Styrene, Interim Report (EPA-
450/4-91-029). This report will
assist in locating potential styrene
sources and estimating the result-
ing styrene emissions.
This report contains available
process descriptions, process varia-
tions, and emissions release points
for styrene sources. It also presents
available emissions data, including
emission factor estimates, that in-
dicate the potential for styrene re-
leases from these sources. Over-
views of procedures for source
sampling and analysis of other air
toxic emissions from these sources
are also provided.
An interim edition of this docu-
(continued on page 7)
6

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(continued from page 6)
merit is being released. The final
report will include the results of
EPA's testing program that is
underway for unsaturated polyester
resin fabricators who produce
cultured marble bathroom fixtures.
How to Obtain More Information
Single copies of the Air CHIEF
CD, SPECIATE, and XATEF are
available to government agencies
from Anne Pope, EPA, OAQPS,
EIB, MD-14, Research Triangle
Park, North Carolina 27711, (919)
541-5373 or (FTS) 629-5373. For
private (for profit) requesters, the
Air CHIEF CD will be available
for a fee through the Government
Printing Office (GPO), and the
1991 editions of SPECIATE and
XATEF will be available for a fee
from the National Technical Infor-
mation Service (NTIS).
Single copies of the styrene
report are available by writing the
EPA Library at MD-35, Research
Triangle Park, North Carolina
27111, or by calling (919) 541- 2777
or (FTS) 629-2777. This report will
be available for a fee through NTIS.
No order numbers had been
assigned to the reports available
through NTIS when this Newsletter
went to press.
For a listing of other air toxic
emission reports, a brochure is
available entitled "Tools for Esti-
mating Air Emissions of Criteria
and Toxic Pollutants." This bro-
chure provides an overview of the
EPA's air emissions estimating
tools. For further information on
the Air CHIEF CD, SPECIATE
and XATEF, these reports, or the
brochure, contact Anne Pope.
*See related articles in the September
1990 and January 1991 Newsletters.
OHEA Adds Air Component to
Integrated Modeling Evaluation System
by Rich Walentowicz, EPA Office of Health and Environmental Assessment
EPA's Office of Health and En-
vironmental Assessment (OHEA)
has added an air component to the
Integrated Modeling Evaluation
System (IMES), developed to assist
exposure and risk assessors in
making informed decisions on fate
or dispersion models and their pre-
dictions. The use of fate models to
estimate contaminant concentra-
tions is an integral part of expo-
sure and risk assessments as well
as in reviewing these assessments.
Determining the most appropriate
model to use has long been a con-
cern to risk assessors and man-
agers. IMES is available to assist
users in resolving these concerns.
The IMES is a computer tool
that can provide a one-step ap-
proach for model information and
selection. This system is the result
of integrating several OHEA proj-
ects addressing exposure and fate
models. On September 24, 1986,
EPA published the "Guidelines for
Estimating Exposures" in the
Federal Register. Subsequently,
OHEA prepared a series of tech-
nical support documents to assist
users in selecting appropriate air,
surface water, and ground water
models. The development of IMES
followed and OHEA drew from
these documents, integrating this
information with other projects
that had addressed exposure and
fate models.
Three different modules form
the basis of IMES: the Selection,
Validation, and Uncertainty
Modules. The Selection Module,
the principal focus of the system,
allows users to obtain a list of
models in different media and to
select the most appropriate models
for the application or scenario of
interest. In the Selection Module,
the user responds to questions
related to site characteristics.
The Validation Module re-
trieves background information on
models and their validation status.
The module is connected to an ex-
tensive data base explaining ex-
plicit features of the various models
and their bibliographies and ap-
plications. Development of more
information for this module will
begin in February 1992.
The Uncertainty Module com-
pares model predictions with field
data sets and determines relative
bias, coefficient of variation, and
standard deviation ratio. Due to
field data limitations, this capabili-
ty is available for only a subset of
surface water models. A key fea-
ture of this module is the graphical
presentation of the information ob-
tained from uncertainty studies to
present statistical relationships.
The Validation Module con-
tains detailed information on about
100 models and descriptive state-
ments on over 300 models. The
Selection Module offers users over
130 models within the three dif-
ferent media. In the air compo-
nent, a user will find about 40
models, two of which, TSCREEN*
and DEGADIS, have air toxics
applications.
The system is easy to use and
contains context-sensitive help
screens so that little, if any, written
documentation is required. The
help screens within the current
version of IMES assist users in
understanding terms and concepts.
In addition, several graphical help
profiles are included and will form
(continued on page 8)
7

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OHEA
(continued from page 7)
the basis of future graphical train-
ing in modeling concepts. IMES
also is now being converted to a
Microsoft Windows1Menvironment.
The system now refinires
slightly over 5MB of storage space
on a hard disk and at least an EGA
monitor. It fits on two diskettes,
which also include the user's
manual, "Guide to Using the In-
tegrated Modeling Evaluation
System" (OHEA-E-336), and a
stand-alone demo, all of which are
compressed. The user's manual is
in WordPerfect 5.1IM format and
can be searched and/or selectively
printed. The demo provides a brief
introduction and some training in
the use of IMES.
For more information on IMES,
contact Rich Walentowicz, U.S.
EPA, Office of Health and En-
vironmental Assessment, 401 M
Street SW, Washington, D.C.
204BO, or call (202) 260-8922 or
(FTS) 260-8922.
Eastern States Pursue California Auto Standards
In October 1991, the Ozone
Transport Commission, which con-
sists of NESCAIJM States* Dela-
ware, Maryland, Pennsylvania,
Virginia, and the District of Col-
umbia, agreed to propose adoption
of California's aggressive motor
vehicle exhaust emissions stan-
dards to reduce smog and toxic air
pollution levels across the region.
This action is a follow-up to the
1989 NESCAIJM agreement to
adopt the California vehicle emis-
sions standards. Since that time,
California has adopted new, more
stringent standards.**
Implementing the California
LEV program in the Northeast
states is viewed as significantly
more cost effective than other air
pollution control measures such
as reducing emissions from in-
dustry beyond the levels man-
dated in the Clean Air Act or
implementing strict transporta-
tion control measures.
All Ozone Transport Commis-
sion members except Delaware
also signed a Memorandum of
Understanding (MOU) to request
Federal reformulated gasoline for
all their nonattainment areas. By
implementing this measure,
hydrocarbon emissions, including
benzene, will be reduced by 15
percent in 1995 and by 25 percent
in 2000. Reductions of other air
toxics are also expected.
The Ozone Transport Commis-
sion was formed by the Clean Air
Act Amendments of 1990 (CAA)
in response to the severe summer-
time smog problem when millions
of people in the Northeast are ex-
posed to unhealthy air pollution
levels. The levels are attributable
in large part to motor vehicles (the
region accounts for approximately
20 percent of the U.S. vehicle fleet),
the largest source of hydrocarbons,
nitrogen oxides (NOx), carbon mon-
oxide (CO), and toxic air pollutants.
Massachusetts and New York
have taken the lead in promoting
(continued on page 9)
Provisions of the California LEV Program
The CARB established the LEV standards to achieve significant reductions in
VOCs, NOx, and other pollutants in response to its ozone nonattainment problem.
Under the LEV program, four new categories of vehicles certified to increasingly
stringent emission standards will be introduced over the next decade: transitional
low emission vehicles (TLEVs), low emission vehicles (LEVs), ultra-low emission
vehicles (ULEVs) and zero emission vehicles (ZEVs). Compliance with the TLEV,
LEV, and ULEV standards will be achieved through a combination of advanced
vehicle emission control technology and reformulated gasoline or other clean-
burning fuels. ZEVs are defined as vehicles with no direct exhaust or evaporative
emissions; only battery-powered electric vehicles are expected to be oipable of cer-
tifying to this standard in the near term.
Beginning in Model Year 1994, vehicle manufacturers will be required to meet
progressively more stringent fleet average non-methane organic gas (NMOG) stan-
dards. Manufacturers will be allowed to meet the fleet average standards by certi-
fying vehicles to any combination of TLEV, LEV, ULEV, ZEV, or conventional
vehicle standards, as long as their sales-weighted NMOG emissions do not exceed
the prescribed fleet average in a given year. The California LEV program includes
a banking and trading component that permits manufacturers to earn marketable
credits and offset poor vehicle sales or overly optimistic sales projections for a cer-
tain model year by utilizing credits previously earned by that manufacturer or
competitor.
Potentially significant additional benefits are likely to accrue under the LEV
program as a result of advanced on board diagnostics, warranty recall, and the fact
that ZEVs have no evaporative emissions. The projected emission benefits do not
include the impact of enhanced inspection and maintenance programs.

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California Auto Standards (continued from page 8)
regionwide adoption of this motor
vehicle control strategy. Both states
have formally proposed regulations
to adopt the California Low Emis-
sion Vehicle (LEV) program (see
inset) and have already conducted
regulatory hearings.
In September 1991, NESCAUM
completed an analysis that compared
the exhaust emission benefits asso-
ciated with implementing the
stringent California LEV program
in the Northeast states to the future
Federal vehicle control program as
mandated in the CAA. The results
showed significant additional ex-
haust emission benefits of the Cali-
fornia LEV program (see Table 1).
Although total emissions from motor
vehicles are projected to decrease
under both programs from 2000
through 2005, emissions under the
Federal program after 2005 are
estimated to rise again as the in-
crease in vehicle miles travelled
begins to offset the emission stan-
dards benefits. Under the Califor-
nia LEV program, fleetwide emis-
sions continue to decline through
2015 as new LEVs replace older,
higher-polluting vehicles. The
NESCAUM study assumes that
EPA will fully implement the man-
dates of the CAA according to the
prescribed schedule and that the
California Air Resources Board
(CARB) program will not change
during the study period.
Implementing the California
LEV program in the Northeast
states is viewed as significantly
more cost effective than other air
pollution control measures such as
reducing emissions from industry
beyond the levels mandated in the
Clean Air Act or implementing
strict transportation control mea-
sures. The NESCAUM report esti-
mates that the more aggressive ex-
haust emission requirements will
increase the price of a new car by
up to $170.
For more information, contact
Arthur Marin at NESCAUM at
(617) 367-8540.
*Northeast states for Coordinated
Air Use Management (NESCAUM)
states include Connecticut, Maine,
Massachusetts, New Hampshire,
New Jersey, New York, Rhode
Island, and Vermont; Connecticut is
continuing to evaluate the benefits of
the California standard.
* *See related article in the March
1990 Newsletter.
Table 1
NESCAUM Total Projected Light-Duty
Vehicle Exhaust Emissions for NESCAUM States1



Percent


California
Reduction
Year/pollutant
Federal
LEV
from Federal
2000



VOCh
457
438-446
2.4-4.2
NOxh
558
541-543
2.7-3.0
CO1
10,057
9948-9979
0.8-1.1
Benzene'1
3,47(1
3288-3385
2.6-5.4
1,3-Butadiene'*
419
391
6.7
Formaldehyde'1
1,161
1098-1126
3.0-5.4
2005



voc
385
278-336
12.7-27.8
NO
X
495
403-428
13.5-18.6
CO
9,632
8389-9116
5.4-12.9
Benzene
3,011
2067-2598
13.7-31.3
1,3-Butadiene
364
252-297
18.6-30.8
Formaldehyde
1,011
689-876
13.4-31.9
2010



VOC
393
197-316
19.6-49.9
NO
X
495
331-386
22.0-33.1
CO
10,004
7483-9180
8.2-25.2
Benzene
3,082
1458-2456
20.3-52.7
1,3-Butadiene
356
161-283
20.6-54.8
Formaldehyde
1,019
475-832
18.4-53.4
2015



VOC
419
156-322
23-63
NOx
524
308-387
26-41
CO
10,621
7101-9610
10-33
Benzene
3,278
1179-2517
23-64
1,3-Butadiene
385
131-297
23-66
Formaldehyde
1,093
344-848
22-65
a These estimates assume benefits from a regionwide enhanced inspection/maintenance program.
b Emission estimates are in tons per summer day.
' Emission estimates are in tons per winter day.
d Emission estimates are in tons per year, based on summer day emission estimates.
9

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Air RISC Updates Directory
The Air Risk Information Sup-
port Center (Air RISC), in continu-
ing support to State and local air
pollution control agencies on health,
exposure, and risk assessments, is
updating its "Directory of Informa-
tion Resources." The directory is a
reference tool intended to be used
as a starting point for identifying
relevant information and contacts
in health, exposure, and risk assess-
ment. It is divided into four sec-
tions: Information Resources - 19
primary and secondary sources of
information sponsored by the EPA
(e.g., clearinghouses and hotlines);
Key EPA Offices - primary EPA of-
fices involved in some aspect of
health, exposure, and/or risk
assessments; EPA Regional Infor-
mation Resources - addresses of the
10 EPA Regional Offices, a map of
states covered by each region, and
regional contacts in the four key
subject areas of air toxics, library
services, Superfund, and RCRA.
Key Reference Materials - listing of
resources such as health, exposure,
and risk assessment documents,
occupational safety and health
references, and chemical-specific
profile documents.
The directory also includes an
index and an appendix of data
bases containing health, exposure,
and risk assessment information
on air pollutants.
To receive a copy of the Air
RISC directory when completed in
early 1992, call the Air RISC
Hotline at (919) 541-0888 or (FTS)
629-0888, or write to Air RISC,
U.S. EPA, OAQPS, MD-i:),
Research Triangle Park, North
Carolina 27711.
The NAT1CU Newsletter is published six times a year by the Nafi<>nal Air Toxics Information Clearinghouse. The Newsletter is prepared
by Radian Corporation under EPA Contract Number 68-1)1-0125, Worft-^iKiiment 1-1. The EPA Editor is Carol Jones, EPA Office of Air Quality
Planning and Standards, Research Triangle Park, North Carolina 27711, Telephone: (919)541-5341. The Radian Project Director is Linda Cooper,
Radian Corporation, P. (). Box 13000, Research Triangle Park, North Carolina 27709, (919)5 11-9100.
The Newsletter is distributed free of charge. To report address changes, write Meredith Haley, Radian Corporation, P. (). Box 13000, Research
Triangle Park, North Carolina 27709
The views expressed in the NATICI1 Newsletter do not necessarily reflect the views and policies of the Environmental Protection Agency.
Mention of trade names or commercial products does not constitute any endorsement or recommendation for use by EPA.
Printed on recycled paper.
Carol Jones
Pollutant Assessment Branch
U.S. Environmental Protection Agency
MD-13
Research Triangle Park, NC 27711
FIRST CLASS MAIL
U.S. Postage Paid
E.P.A.
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