A Preliminary
Risk-Based Screening
Approach for Air Toxics
Monitoring Data Sets
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U.S. Environmental Protection Agency
Air, Pesticides, and Toxics Management Division ^£D sr
Atlanta, Georgia 30303 .x
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EPA-904-B-06-001
www.epa.gov/region4/air/airtoxic/
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October 2010 Cover Photo: Greg Noah/EPA
(Version 2)
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Disclaimer
The information and procedures set forth here are intended as a technical resource to those
conducting risk-based evaluations of air toxics monitoring data. This document does not
constitute rulemaking by the Agency, and cannot be relied on to create a substantive or
procedural right enforceable by any party in litigation with the United States. As indicated by the
use of non-mandatory language such as "may" and "should," it provides recommendations and
does not impose any legally binding requirements. In the event of a conflict between the
discussion in this document and any Federal statute or regulation, this document would not be
controlling.
The general description provided here may not apply to a particular situation based upon the
circumstances. Interested parties are free to raise questions and objections about the substance of
this methodology and the appropriateness of its application to a particular situation. EPA Region
4 and other decision makers retain the discretion to adopt approaches on a case-by-case basis that
differ from those described in this document where appropriate. EPA Region 4 may take action
that is at variance with the recommendations and procedures in this document and may change
them at any time without public notice. This is a living document and may be revised
periodically. EPA Region 4 welcomes public input on this document at any time. Comments
should be sent to Dr. Kenneth Mitchell (mitchell.ken@epa.gov).
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PART I:
BACKGROUND
The purpose of this document is to provide a
risk-based methodology for performing an
initial screen of air toxics monitoring data
sets in outdoor air. This methodology is
necessary because:
1. Many Region 4 State, local, and
tribal (R4 SLT) air agencies have
been collecting air toxics data for a
number of years;
2. These Agencies want to evaluate the
data sets to determine what the
results indicate with regard to the
potential for exposures of potential
public health concern;
3. The risk-based approaches for
evaluating air toxics have made
significant strides in recent years;
however, many R4 SLTs are still in
the process of developing their
expertise in this area. This maturing
expertise, as well as resource issues,
have had the effect of hindering
many R4 SLTs in their efforts to
develop a detailed risk evaluation of
their monitoring data sets;
4. As they work to develop their risk
assessment expertise [e.g., by
becoming more familiar with the full
details of the EPA's Air Toxics Risk
Assessment (ATRA) Reference
Library1], R4 SLTs need a concise
methodology that they can use to
efficiently screen existing monitoring
data sets to identify whether any
chemicals are potentially posing
exposures of public health concern in
specific geographic areas;
What This Preliminary Screening-Level
Methodology Is Not
This preliminary screening-level methodology is not
a substitute for a thorough risk assessment. Instead,
the application of this process will commonly result
in a "short list" of chemicals and geographic
locations that should be the focus of more rigorous
risk evaluation. This short list of chemicals are
characterized in this document as posing exposures
of potential public health concern and is only meant
to imply that the chemicals failed the screening
analysis. To clarify the actual level of concern posed
by any given chemical that fails the screen will
necessarily require a more in-depth risk analysis and
may even require the collection of additional data.
(Analysts may decide to carry all detected chemicals
through a subsequent risk assessment, whether they
fail the screen or not. While this is somewhat more
work, the availability of computer tools such as
spreadsheets and databases make this a relatively
trivial exercise. Carrying all chemicals through the
risk assessment process also has the benefit of further
clarifying for stakeholders which chemicals are the
likely risk drivers and which are likely not.)
Ultimately, this methodology is not an end in itself.
Instead, it should be viewed as a tool that can help
narrow the focus of SLTs to important chemicals and
locations as they work to strengthen their risk
assessment skills.
5. There is a need to standardize the
procedures used by R4 SLTs to
produce uniform risk-based screening
results. This document presents a
step in that direction.
It is expected that the application of this
screening-level methodology by R4 SLTs
will allow them to better address air toxics
issues by focusing their limited resources for
further analysis only on those geographic
areas and chemicals for which the available
data indicate a potential for exposures of
public health concern. The method may also
provide a risk basis for a decision to
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continue (or not continue) a given
monitoring effort. For example, monitoring
sites that consistently indicate a low
potential for exposures of public health
concern, by application of this screening
methodology, might reasonably be
discontinued and the monitoring resources
shifted to other locations. This methodology
will also help R4 SLTs better understand the
data quality objectives (DQOs) that
monitoring studies should meet for the
results to be used in a risk-based decision
making framework.
It should be noted that performing this
screening-level methodology in an adequate
fashion necessarily requires the analyst to
have already learned some of the
fundamentals of risk assessment (e.g.,
understanding data quality requirements for
air toxics monitoring data sets used in a risk-
based decision making framework). To that
end, this document attempts to point analysts
to key references that they should be familiar
with as they apply the methodology.
A. Overview of the Screening-Level
Methodology
The basic concept behind this risk-based
initial screening level methodology is to
evaluate air monitoring data sets using a
framework that is, by design, relatively
simple to perform yet conservative (i.e.,
health protective) in nature. This initial
screening methodology is designed, through
the use of conservative decisions, to identify
pollutants for which risks are unlikely to be
of concern. Accordingly, if all of the
monitoring data "pass the screen" using this
approach, the analyst may be able to
conclude that the monitoring results are
indicative of acceptably low risk and that a
more robust analysis (were one to be done)
would come to the same conclusion. Any
chemicals that do not pass the screening
criteria would become the primary focus for
any number of follow-up activities.
For example, decision makers might choose,
based on the screening level results, to
perform a more extensive analysis of these
failing chemicals to help confirm or deny the
outcome of the screening level assessment.
Specifically, a likely next step an analyst
will generally recommend for chemicals
failing the screen is to develop more rigorous
estimates of potential exposure, such as 95%
upper confidence limits (95% UCL) of the
arithmetic mean using the full set of
monitoring data, as described in the ATRA
Reference Library, Volume 1, Appendix I.
The analyst may also recommend the
application of an exposure model (see
www.epa.gov/ttn/fera\ and may also
indicate a need for additional air quality
monitoring or air dispersion modeling to
help clarify potential exposures and risks.
In some circumstances, decision makers may
choose "action oriented" alternatives to
respond to the screening results. For
example, consider a screening level
assessment that identifies a chemical of
potential public health concern that can
readily be linked to a specific source. If
there are inexpensive and available risk
reduction options for the emission source,
the decision makers may simply choose to
take actions to reduce potential exposures to
that chemical rather than perform further
analysis.
The basic steps of the screening process are
outlined below. The details of each of these
steps are discussed in detail in the sections
that follow.
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1. Identify the monitoring data sets to
be screened and the geographic areas
and time frames that the monitoring
data in question represent.
2. Assess the data to determine if they
are of sufficient quantity and quality
to perform the screen.
3. For each chemical detected at least
once in the data set, create a
statistical summary of the monitoring
results for that chemical. The
statistical summary will commonly
include the following: Number of
valid samples collected and
frequency of detection, the method
detection limits (MDLs), and range
of detected values.
4. For each detected chemical in the
data set, compare the maximum
monitored value to the suggested
chronic screening level value
provided in Appendix A and the
acute values provided in Appendix B
(the basis for using the maximum
value found as a surrogate for
exposure is provided in Part I,
Section D below). Summarize the
results of the comparison process in a
table. Highlight chemicals whose
maximum monitored values exceed
their respective screening values
(chronic and acute). For each
chemical whose maximum monitored
value exceeds a screening value,
review the full data set and determine
the percentage of detections that are
at or above the screening value.
Augment the results described in
Step 4 with ancillary information
about chemicals that fail the screen
(e.g., possible sources, applicable
regulations, estimated background
concentrations, NATA national scale
assessment results for the geographic
area, etc.).
Describe areas of uncertainty in the
analysis.
Based on the screening results
provided in Step 4, the ancillary data
developed in Step 5, and the
uncertainty analysis developed in
Step 6, develop a written description
of the analysis, including a discussion
about the possibility that a public
health threat exists that requires
further analysis. Include in this
discussion an overall statement of the
confidence in the results.
Systematic Planning
Systematic Planning is necessary to define the type,
quantity, and quality of data a decision maker needs
to make a decision and is performed before collecting
or generating environmental data. The Data Quality
Objectives (DQO) Process is an example of a
systematic planning process that assessors would use
to translate a decision maker's aversion to decision
error into a quantitative statement of data quality
needed to support a decision. EPA requires that a
systematic planning process such as the DQO process
be used for all EPA environmental data collection
activities.
For more information on EPA's quality program, see
www.epa.gov/quality.
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These steps are shown pictorially in Exhibit
1. An example is provided in Appendix D to
illustrate how to apply this methodology to
an air toxics monitoring data set.
At the end of the screening process, the
analyst will generally have sorted the
detected chemicals at each monitor into two
groups. The first group consists of
chemicals that "pass the screen." These
chemicals are below screening level
concentrations for both chronic and acute
exposures. Decision makers may decide to
pursue evaluation of these chemicals no
further.
The second group consists of chemicals that
"fail the screen." These chemicals are at or
above screening level concentrations for
chronic and/or acute exposures. These
chemicals, at a minimum, will commonly
require a more in-depth analysis (e.g., a more
detailed risk assessment) to clarify the
potential risks associated with the monitored
concentrations.
As noted previously, all detected chemicals
can easily be carried forward to the full risk
assessment given the available computer
tools to automate the process and the
analysts may choose to do so. The benefit of
carrying all detected chemicals forward is to
further clarify which chemicals are the likely
risk drivers and which are likely not. This
will also help avoid a potential
misperception by some stakeholders that
analysts are trying to "hide important data."
B. Derivation of Chronic Screening
Values
In this methodology, a chronic screening
value is used to indicate a concentration of a
EXHIBIT 1
Flow Diagram for Preliminary Risk-Based
Screening of Air Toxics Monitoring Data
STEP1
Identify Monitoring Data Sets to be Screened
STEP 2
Evaluate the Quantity and Quality of Data for
Screening-level Analysis
STEP 3
Develop Monitor-Specific Statistical Summaries for
Each Chemical Detected at Each Monitor
STEP 4
Screen Chemicals Against Chronic and Acute Screening
Values - Highlight Chemicals that Fail the Screen
STEP?
Write-up Analysis, including Statement of Overall
Confidence in the Results
chemical in the air to which a person could
be continually exposed for a lifetime
(assumed to be 70 years) and which would
be unlikely to result in a deleterious effect
(either cancer or noncancer health effects).
The suggested chronic screening values used
in this methodology are presented in
Appendix A. The starting point for the
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derivation of these screening values is the
Office of Air Quality Planning and
Standards' (OAQPS) list of recommended
chronic inhalation toxicity values for the
Hazardous Air Pollutants (HAPs).2
Specifically, the methodology uses the
OAQPS recommended inhalation unit risk
(IUR) value for cancer causing agents and
inhalation reference concentration (RfC) for
noncancer health effects3 as a starting point
and performs the following manipulations to
derive a final chronic screening value:
i. Chronic screening value for
"noncancer" (and in some cases,
cancer) health endpoints. For the
"noncancer" screening value (which
in some cases, is also a cancer
screening value), the chronic RfCs
were used as a starting point since
chronic RfCs are, by definition, an
estimate of the concentration of a
chemical in the air to which
continuous exposure over a lifetime
is expected to result in little
appreciable deleterious effects to the
human population, including
sensitive subgroups. However, most
ambient air contains a mixture of
chemicals which may result in a
cumulative hazard that is not
accounted for by assessing chemicals
on an individual basis. To account
for possible exposure to multiple
contaminants, the noncancer chronic
screening value for each chemical
was selected to be one tenth of its
chronic RfC [i.e., (0.1) x (RfC) x
(1000)]. Noncancer screening values
are presented in Appendix A as an air
Chronic vs. Acute
What's the Difference?
Chronic exposure is continuous or multiple
exposures that occur over an extended period of
time or a significant fraction of an animal's or
person's lifetime.
Chronic health effects are effects that occur as a
result of repeated or long term (chronic) exposures
(IRIS definition).
Acute exposure is one or multiple exposures
occurring within a short time frame relative to the
lifetime of an animal or person (e.g., approximately
24 hours or less for humans).
An acute health effect may occur within a short
period of time following an acute exposure, for
example, minutes to a few days. (Some acute
exposures may also lead to chronic health effects.)
The ATRA Library, Volume 1, Chapter 12 provides
details on chronic vs acute toxicity data.
n.
concentration in ug/m3. (Since RfCs
are reported as mg/m3 in the OAQPS
table, multiplication by 1000 is
necessary to convert mg to ug).
Calculating the noncancer screening
values in this fashion is conservative
since it is unlikely that a person
would be continuously exposed over
a lifetime to 10 chemicals that behave
in a lexicologically similar manner.b
Chronic screening value for cancer
health endpoints. For cancer, the
IUR for a chemical is used as a
starting point to derive an air
aNote that some RfCs are developed
to be protective of both cancer and
noncancer health endpoints.
bThis rationale has been previously
employed by Region III Superfund program
in their table of risk based concentrations -
http://www.epa.gov/reg3hwmd/risk/human/index.htm.
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111.
concenration corresponding to a
specific individual cancer risk level.
In this methodology, the cancer
screening risk level was selected as
one in one million (written 1E-06 or
IxlO"6) which is the lower end of the
cancer risk range cited in the 1989
Benzene NESHAP (approximately
1E-04 to approximately 1E-06) as the
range of risk used for regulatory
decision making for the air toxics
program.3 The 1E-06 level of risk
was also selected to take into account
the potential for simultaneous
exposure to multiple carcinogens.
Specifically, one would have to
experience the unlikely scenario of
continuous lifetime exposure to 100
cancer causing agents (all at a
concentration corresponding to a risk
level of 1E-06) to approach the upper
end of the above noted risk range
(approximately 1E-04). The chronic
screening value for cancer is
calculated by simply dividing the
IUR into a risk of one in a million
[(lE-6)/(IUR)]. Cancer screening
values are presented in Appendix A
as air concentrations in ug/m3.
Final chronic screening value for
both cancer and noncancer effects.
The final chronic screening value for
a chemical is simply the lower of the
concentration values calculated in
Steps i and ii above. The final
chronic screening values are
presented as an air concentration in
ug/m3. A quick review of Appendix
A shows that a number of chemicals
have no final chronic screening
value, indicating no data in the
toxicological references upon which
OAQPS relies for toxicity values.
Chapter 12 (Section 12.7) of Volume
1 of the ATRA Reference Library
discusses various approaches to
dealing with chemicals that have no
toxicity information.
The suggested screening levels in this
methodology were selected for the reasons
stated above and because this approach has
precedent in other risk-based environmental
programs (see footnote b). If a SLT decides
to use different screening levels, it is
encouraged to document why it chose an
alternate value and why the alternate value is
in line with the screening level concept (i.e.,
a simple approach counterbalanced with
conservative inputs and decision criteria).
[NOTE: The OAQPS Toxicity Values tables
are not static and changes are made from
time to time which may not be reflected in
the current version of this screening level
methodology. Analysts are encouraged to
routinely review the OAQPS Toxicity
Values tables for changes and to adjust the
screening levels presented here, as
necessary. This applies to both chronic and
acute values presented in Appendices A and
B.]
C. Derivation of Acute Screening Values
Many air pollutants can cause adverse health
effects after short-term (acute) exposure to
relatively high concentrations that last from
a few minutes to days. Depending on the
exposure circumstances and the chemicals
involved, acute exposures may be of greater
concern than chronic exposures. Appendix
B provides a discussion of how to perform
an acute risk-based screening level
evaluation along with a selection of available
acute toxicity values.
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D. Issues Regarding Risk-based Analysis
Using Monitoring Data
In this preliminary risk-based screening
approach, monitoring data are used to
represent exposure. The screening values
presented in Appendix A apply to
continuous lifetime exposures to the
general population, including sensitive
subpopulations (even though these values are
commonly derived from studies involving
discontinuous exposures). As such, it would
be most useful to have monitoring data that
are also representative of the same time
frame (i.e., continuous lifetime exposure).
This follows from the general risk
assessment principle that the time frames
associated with exposure data and toxicity
data should match in order for the two types
of data to be computationally combined in a
risk-based analysis.
That being said, monitoring samples are, as
noted above, most often collected
discontinuously over relatively short periods
of time (e.g., a 24 hour, 1 hour, or 15 minute
sample collected every 6 or 12 days for a
year). In a full scale risk assessment, the
analyst would usually perform a series of
mathematical computations to convert a
year-long set of monitoring data into a more
rigorous estimate of long term exposure.
Most commonly, the analyst would calculate
a 95% UCL of the arithmetic mean of the
monitoring data set (see ATRA Reference
Library, Volume 1, Appendix I). In some
cases, higher levels of analysis would rely on
air dispersion modeling (and perhaps
exposure modeling) to evaluate exposure,
while relying on monitoring data to evaluate
modeling results, look for gaps in the
emissions inventory, and confirm hotspots.
The various ways in which one can approach
a risk based analysis are provided in the
ATRA reference library. The text box on the
next page describes several common
approaches for evaluating exposures.
To avoid having to perform such calculations
for each chemical detected at a monitor in a
preliminary risk-based screen of the type
described here, a less onerous, yet
conservative alternate approach is necessary
to help identify the chemicals and locations
that are likely responsible for most of the
risk. The analyst could then focus any
subsequent refined analysis (i.e., in the full
risk assessment) on this subset of chemicals
and locations.
In this screening approach, the maximum
monitored sample result is used as a
conservative surrogate for long-term
exposure in the preliminary screening level
process. This is suggested since, in a full
scale risk assessment, one would usually not
use a higher value (i.e., the mathematical
development of more robust estimates of
chronic exposure using a full set of
monitoring data will generally lead to
estimated exposure concentrations at or
below the maximum monitored value found).
In short, using the maximum detected
concentration of a chemical as a surrogate
for long term exposure is a simple and
straightforward way to screen a large
monitoring data set and is expected to result
in a lessened chance that chemicals posing
exposures of potential public health concern
will be removed from further consideration.
(To more fully understand the utility of a
screening approach as a preliminary step in a
full risk analysis, it is important that analysts
become familiar with the process of
developing more robust long term inhalation
exposure concentrations and risk estimates.
Analysts are referred to the ATRA Reference
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Library, Volume 1, Part II and Appendix I to the analyst compares individual monitoring
learn more about this subject.) sample results to acute toxicity values to
evaluate the potential for acute exposures of
Finally, it should be noted that the analysis potential public health concern. This is
of acute concerns using air monitoring data discussed in detail in the following sections.
is the same for both screening level
evaluations and more robust risk
assessments; namely,
Approaches to Evaluating Exposure
For air toxics impact analysis, a variety of measures may be used to evaluate the potential exposures of a person
to a chemical in the air. Some measures are fairly crude and some are more refined. The most common
measures used to estimate exposure are listed below (generally, from most crude to most refined):
Pounds Released A very crude indicator of potential exposure because there is no information on
either fate and transport in the environment or on how people interact with the
contaminated air.
Ambient Concentration A better indicator of potential exposure (fate and transport are included) but still
lacks information on how people interact with the contaminated air. The quality of
the concentration estimate depends on the methods used to develop it (i.e., the
various types of monitoring or modeling used).
Exposure Model An even better indicator of potential exposure because it does include information
Refined Ambient on how people interact with the contaminated air. The quality of the information
Concentration depends on both the methods used to estimate ambient concentration as well as those
used to evaluate demographics and activity patterns.
Personal Exposure An even higher level of understanding of exposure, usually developed by personal
exposure monitoring.
The term exposure concentration is used to describe the concentration of a chemical in its transport or carrier
medium (i.e., an environmental medium or contaminated food) at the point of contact. This concentration can
be either a monitored or modeled value and may or may not have been refined by the application of an exposure
model.
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PART II: DETAILED SCREENING
METHODOLOGY
This Part provides the detailed method for
performing a risk-based screening of an air
toxics monitoring data set (see Part I,
Section A, Steps 1-7). Information is
provided on how to identify the monitoring
data set to screen, how to perform the actual
screen, and how to begin to interpret and
communicate the results. For brevity, the
reader is referred to the relevant sections of
the ATRA library for detailed information,
where necessary.
STEP 1: Identify the monitoring data sets
to be screened and the geographic areas
and time frames that the monitoring data in
question represent.
Gather together the monitoring data sets that
are to be evaluated in the screening
assessment. This will commonly be
comprised of the data collected at one, two,
or some small number of monitors placed in
and around a specific neighborhood or some
other relatively small geographic area (e.g.
monitors set up around a small town). At a
minimum, monitors to be included should all
be within the same airshed.0 The geographic
area the monitor was established to evaluate
(e.g., neighborhood scale, urban scale, etc.)
should be noted along with the analytes
Tor this screening level
methodology, an airshed means a geographic
area that, due to topography, meteorology,
and climate, shares the same air. The
segregation of monitors by airshed is used
here as a way to distinguish (on a coarse
geographic scale) potential exposure
scenarios from one another.
sampled by the monitor, the analytical
method used to evaluate the samples, and the
time frame of monitoring (i.e., frequency of
sample collection and length of time the
monitoring occurred). For chronic exposure
analysis, monitoring data sets should contain
a minimum of one year's data to allow for a
consideration of seasonal and source
variation. Only full year data sets should be
used for year-to-year comparisons (or at least
data sets that are comparable in terms of the
time frame monitored each year).
Note that some air toxics may have a strong
concentration gradient across a study area.
Concentration gradients depend on a number
of factors, including specific characteristics
of the sources in the area, area-specific
physical considerations such as terrain
effects and local meteorology, and
atmospheric chemistry. As such, it may be
helpful to develop a separate screening level
analysis for different groupings of monitors
in the same airshed if they are separated by a
reasonably large distance. For example, a
large urban area may have one group of
monitors located in a highly industrialized
mixed-use residential area and another group
of monitors located miles away in a non-
industrial residential area. From the
standpoint of assessing and communicating
what the monitoring results may indicate
from a risk perspective, it may be helpful to
perform separate screening analyses for the
different groups of monitors for these two
neighborhoods.
An additional consideration is the similarity
across the different areas with regard to
sources of the chemicals of interest and their
influence on the monitors. For example, if
two areas are similar in terms of land use,
types of sources, and chemicals emitted, the
analyst may wish to evaluate both groups of
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monitors within the same screening level
analysis. Ultimately, the analyst must take
into consideration the unique circumstances
of any given geographic area when deciding
what monitors to consider together in a
particular screening level analysis.
Once a set of monitors to be evaluated has
been identified, the data from all these
monitors could be combined into one large
data set. The advantage to this approach is
that only one screen needs to be performed
for each chemical. The drawback is that if
any chemical fails the screen (a likely event
for at least some ubiquitous chemicals), the
combined data set will have to be
disaggregated to identify the failing
monitor(s). On balance, it is recommended
that the screening process be performed on a
monitor-by-monitor basis.
STEP 2: Assess the data to determine if
they are of sufficient quantity and quality to
perform the screen.
The basis of this screening process is to use
monitoring data to assess potential exposures
to people in the vicinity of the monitor and,
thereby, the potential risk posed by the
exposures. As such, enough high quality
data that were developed specifically for the
purpose of assessing exposures are needed to
allow a meaningful risk-based screen to be
performed. In other words, to perform a
risk-based screen, the data should meet risk-
basedDQOs.
If an existing monitoring data set was
developed without risk-based DQOs in mind,
the data should be evaluated to assess their
utility for risk-based decision making. If the
analyst identifies any significant data
quantity or quality issues, the issues should
be articulated in the final report. In some
instances the analyst may recommend that
the risk screening not be performed at all.
[NOTE: The details of performing a data
quality assessment are significant and
analysts are encouraged to familiarize
themselves with the ATRA Reference
Library Volume 1, Chapters 6, 10, and
Appendix H, EPA's Quality System
documents4, and EPA's Guidance for Data
Useability in Risk Assessment5 before
evaluating monitoring data quality for a risk-
based screening analysis.]
As an example, consider an existing
neighborhood scale monitoring data set for
volatile organic compounds (VOCs) in
which samples were collected once every 12
days for 4 months. Several data quality
issues should be considered.
Issue 1 - Sample Frequency. The
Lake Michigan Air Directors'
Consortium (LADCO) and Midwest
Regional Planning Organization
recently completed a series of
analyses on existing air toxics
monitoring data to evaluate, among
other things, the minimum sampling
frequency needed to develop annual
averages within a specified level of
precision. The results of this work
helped inform the development of
DQOs for the new National Air
Toxics Trends Stations (NATTS).
The LADCO studies indicate, for
example, that the sampling frequency
to develop an annual average for
benzene should be a minimum of 1 in
6 days.6
10
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Issue 2 - Length of Sampling. The
4 month sampling regime will not
have captured the long-term
variability in air concentrations that
results from source emission changes
over time and meteorological
influences which can change
dramatically from season to season.
Issue 3 - Spatial
Representativeness of Samples.
The monitor was established to be
representative of the neighborhood
scale. But just how far beyond the
monitor are the sample results
accurate? Are the results
accurate out to one block away from
the monitor? Two blocks away?
One kilometer away? Does the
representativeness of a monitor vary
with distance by chemical type (e.g.,
volatile organic compounds versus
particulates)?
These are just a few of the issues that need to
be considered when deciding whether there
are limitations in the data set that should be
communicated to the risk manager in the
screening level write-up or whether the
screen should be performed at all. Analysts
are encouraged to become familiar with the
LADCO studies and other relevant
Is My Method Sensitive Enough?
When evaluating the quality of data for screening purposes, an important question to ask is "is my
sampling and analytical procedure sensitive enough?" For example, if the Appendix A screening
level for Chemical X is 0.5 ug/m3 but the method detection limit (MDL) for the compound (as
reported by the lab) was only 1.0 ug/m3, samples that are reported at "not detected" at the MDL may
actually have Chemical X present above the screening level (i.e., above 0.5 ug/m3), but below 1.0
ug/m3. In some cases, there may be no easy remedy to this problem (e.g., there is no readily available
method with sufficient sensitivity). In other cases, poor planning may have led to using a method
with inadequate sensitivity when a more sensitive method was available.
A related issue is how to treat "J-flagged data." A J-flagged value is a detection that occurs between
the MDL and the limit of quantitation for a given sample (the "sample quantitation limit" or SQL).
For screening purposes, J-flagged data are generally used "as is." That is to say, they are considered
to be positive detections that are present at the concentrations reported by the lab.
More information on MDLs, SQLs, and dealing with flagged data is provided in ATRA Volume 1,
Appendices H and I.
11
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monitoring and data quality literature in
order to better understand the evolving state
of the science and the data quality needs of
the end-users.
In summary, there is usually little (if
anything) to be done to enhance the quality
of existing monitoring data sets. If historical
data sets are used, the analyst should be
careful to fully explain the inherent
limitations associated with the data. New
monitoring efforts to evaluate risk should
identify and establish the relevant risk-based
DQOs before monitoring commences. This
will help ensure that sufficient high-quality
data are collected to allow the assessment
questions to be evaluated at a level that is
acceptable to the end users of the analysis.
STEP 3: For each chemical detected at
least once in the data set, create a
statistical summary of the monitoring
results for that chemical. The statistical
summary will commonly include the
following: Number of valid samples
collected and frequency of detection, the
method detection limits (MDLs), and
range of detected values.
Once a set of monitors has been identified
for the screening effort, the analyst should
develop statistical summaries for each
chemical detected at least once at each
monitor. A separate statistical summary
should be developed for each monitor (i.e., if
there are three monitors being screened,
there will be three statistical summary tables
providing information for each of the
detected chemicals at each monitor). A
suggested table format for statistical
summaries follows (see an example of how
to fill in this table in Appendix D):
Statistical Summary of Detected Chemicals
Monitor Number 101
Detected
Chemical
(CAS Number)
Frequency of
Detection
Laboratory-Specific
Method Detection Limit
(ug/m3)*
Range of Detected Values
(ug/m3)
*Analysts may also choose to include a column listing the range of SQLs found across samples for a given analyte
since the SQLs (not the MDLs) are typically used in the full risk assessment to evaluate long-term chronic exposures.
ATRA Volume 1, Appendix I discusses this issue in detail.
12
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Where:
Detected Chemical and CAS
Number is the name of the analyte
reported by the laboratory. The
Chemical Abstracts Service (CAS)
registry number reported by the lab
should also be included because it
can help sort out chemical
nomenclature differences that occur
between different laboratories and
between labs and regulatory chemical
lists.
Frequency of Detection is the
number of times a chemical is
detected in valid samples at a monitor
(including "J-flagged" values'1)
compared to the number of valid
samples collected. For example,
consider a data set in which 30
volatile organic chemical (VOC)
samples were collected but only 25
were determined to be valid (i.e., the
data validation process rejected 5
samples). In the 25 valid samples,
benzene was detected in only 20 of
the samples (15 detects above the
quantitation limit and 5 J-flagged
values below the quantitation limit).
In this example, the frequency of
detection would be reported as 20/25.
d"J" is a laboratory qualifier denoting
that there is a positive identification but that
the associated numerical concentration value
is an estimated quantity. These values are
used "as is" in the screening process (i.e., by
removing the J qualifier and using the
reported value as a detection at the reported
concentration).
Automating the Process
ProTJCL
Evaluating large air toxics monitoring data sets by
hand can be cumbersome and time consuming (and
may lead to mistakes). Fortunately, any number of
computer software packages are available to help
automate the process.
One such EPA software program, ProUCL, was
specifically designed to help evaluate environmental
data sets as part of the risk assessment process. For
example, ProUCL can calculate some of the
summary statistics useful for a risk-based screening
level assessment. ProUCL can also develop the
higher level statistics (e.g., 95% upper confidence
limits) needed to perform a refined risk assessment.
ProUCL is available from EPA's Technical Support
Center for Monitoring and Site Characterization
(http://www.epa.gov/nerlesdl/tsc/software.htm).
One use of the frequency of
detection is to quickly help determine
whether a chemical is routinely found
in the air. This information, in
conjunction with ancillary data such
as the presence of potential sources,
can help inform the next steps (if
any) that decision makers select. For
example, if a detected chemical
exceeds its chronic screening value,
but was infrequently detected (e.g.,
<10% of the time; see ATRA
Reference Library, Volume 1,
Appendix I) and further investigation
identifies no likely sources, the
decision makers may opt to pursue
this chemical no further.
Laboratory-Specific Method
Detection Limits. The MDL is
reported by the laboratory for each
detected chemical in the data set.
Providg the MDLs allows the analyst
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to quickly determine the ability of the
laboratory to detect a given chemical
above the screening level.
Range of Detected Values is the
range, for each chemical detected, of
concentrations actually detected and
reported by the laboratory. The
range should include the highest
(maximum) detection found and the
lowest detection found. J-values are
included. For example, in a data set
for benzene, if the maximum detected
value found was 2.3 ug/m3 and the
lowest detected value found was
0.05J ug/m3, the range would be
reported as "0.05J- 2.3".e
STEP 4: For each detected chemical in the
data set, compare the maximum monitored
value to the suggested chronic screening
level value provided in Appendix A and the
acute values provided in Appendix B.
Summarize the results of the comparison
process in a table. Highlight chemicals
whose maximum monitored values exceed
their respective screening values (chronic
and acute).
eNote that while some laboratories do
not routinely report detections between the
quantitation limit and the detection limit
(i.e., some labs do not report J-flagged
values), the J-flagged data are generally
considered necessary to perform this
screening approach (a data set would
generally be considered insufficient quality
for risk-based screening purposes if J-
flagged data have been purposefully
excluded).
For each chemical whose maximum
monitored value exceeds a screening value,
review the full data set and determine the
percentage of detections that are at or
above the screening value.
For this step, prepare a new table for each
monitor that shows the name and CAS
number of each detected chemical, the
maximum concentration detected, the
chronic and acute screening values, and an
indication of whether the maximum value is
greater than or equal to the screening values
(yes or no). An example table is provided
below. An example of how to fill in this
table is provided in Appendix D.
The chemicals that fail the screen become
the focus of the remaining steps of the
screening level assessment and may be the
focus of any subsequent analyses (e.g., a
more refined risk analysis). As noted
previously, the fact that a chemical fails the
screen only indicates that there is ^potential
for exposures of concern. A more refined
analysis will usually be required to clarify
the likelihood that these chemicals are
presenting exposures of concern.
STEP 5: Augment the results described in
Step 4 -with ancillary information about
chemicals that fail the screen (e.g., possible
sources, applicable regulations, estimated
background concentrations, NATA national
scale assessment results for the geographic
area, etc.).
For each of the chemicals that fails the
screen in Step 4, collect and present ancillary
information that will help decision makers
put the results in context. This can be done
in narrative style or in a table. For example,
provide information on possible sources that
14
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Summary of Screening Analysis for Detected Chemicals
Monitor Number 101
Detected
Chemical
(CAS
Number)
Maximum
Concentration
detected
(ug/m3)
Final
Chronic
Screening
Value from
Appendix A
(ug/m3)
Acute
Screening
Value from
Appendix B
(ug/m3)
Maximum
Concentration is
> Chronic
Screening Value
(Yes/No)?
(% Detections
Exceeding)1
Maximum
Concentration is
> Acute Screening
Value (Yes/No)?
(% Detections
Exceeding)1
1. If the maximum value found exceeds a screening value (chronic or acute), the full data set of valid samples for the chemical is
reviewed to determine the percentage of detections that, individually, are at or above the screening value. The % Detections
Exceeding is equal to the number of detections at or above the screening value divided by the total number of detections,
multiplied by 100.
may be responsible for these concentrations,
how these concentrations compare to other
similar geographic areas, and what (if
anything) is currently being done regarding
air concentrations of this chemical. Other
important issues are whether the local
community has articulated concerns about
air toxics in the past and whether any
relevant health studies have been performed
in the area (e.g., cancer statistics studies
performed by the Agency for Toxic
Substances and Disease Registry - ATSDR).
Some key information sources include:
• The National Emissions Inventory (or
more locally developed inventories)7;
• The Toxics Release Inventory8;
Permit files, including compliance
and enforcement information;
• The National Air Toxics Assessment
(NATA) national-scale assessment
estimates of HAP concentration by
geographic area;9
• Existing rules and future rulemaking
activities affecting sources;
Community complaints; and
ATSDR10 and local health
departments and universities.
(See the ATRA Reference Library, Volume
1, Chapters 2 and 4 for helpful information
on emissions inventories and air toxics rules
and regulations.)
STEP 6: Describe areas of uncertainty in
the analysis.
Reliable information may or may not always
be available for some aspects of the risk
screening process (indeed, scientific
uncertainty is an inherent part of any risk
based analysis). As such, risk managers
almost always have to make decisions using
assessments that are not as definitive in all
key areas as would be desirable. To try and
compensate for some of this uncertainty, the
risk screening process described here is
structured to be overtly conservative.
That being said, it is imperative that the
analyst encourage the end users (not only
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risk managers, but any other stakeholder,
including the media and the public) to not
only "look at the numerical answers" but
also to put them into context by clearly
describing the uncertainties associated with
the analysis and the impact the uncertainties
may have on the results. A description of
uncertainty in risk-based analysis is provided
in the ATRA Reference Library, Volume 1,
Chapters 3 and 13 (Chapters also discusses
another important concept in risk based
analysis - variability). Given the central role
of uncertainty and variability in risk-based
analysis and decision making, the analyst is
encouraged to become familiar with these
concepts and to keep them in mind
throughout both the development and
communication of the screening level
analysis results.
Some of the important questions to cover in
the uncertainty analysis include:
What geographic areas do the
monitoring results represent?
Are "hotspots" possibly present that
are not captured by the monitoring
results?
• Are there important chemicals
possibly present that were not
sampled?
Were sample frequency, sampling
duration, detection limits, and other
risk-based DQOs sufficient to allow a
scientifically sound screening of the
monitoring data set?
• Were any chemicals detected for
which screening values were not
available?
Were any conservative assumptions
made which may have overstated an
apparent problem (e.g., assuming all
chromium is hexavalent when the
local emissions inventory indicates
otherwise?)
Were any assumptions made which
may have understated an apparent
problem (e.g., having too few
monitors to provide a representative
evaluation of exposures across a
geographically large study area)?
If the monitoring data sets are
historical in nature, have local
conditions changed to such an extent
that the older data do not represent
current exposures?
Are there chemicals released from
nearby sources or detected in
monitoring samples which have the
potential to partition to other media
and present significant exposures
through pathways other than
inhalation (e.g., dioxin, mercury)?
STEP 7: Eased on the screening results
provided in Step 4, the ancillary data
developed in Step 5, and the uncertainty
analysis developed in Step 6, develop a
written description of the analysis,
including a discussion about the possibility
that a public health threat exists that
requires further analysis. Include in this
discussion an overall statement of the
confidence in the results.
Once the screening assessment has been
performed, the chemicals that fail the screen
identified, relevant ancillary information
collected, and an analysis of uncertainties
developed, the analyst should describe the
process and results in writing. The analyst
should be careful to provide enough
information so that any reader can follow the
logical progression the analyst took,
including how the evaluated data set was
identified, how the analysis was performed,
and how the conclusions were developed.
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The analyst should make sure to include
important assumptions and decisions made
throughout the process. A suggested report
outline is provided in Appendix C. Useful
background information on presenting risk-
based information is included in the ATRA
Reference Library, Volume 1, Chapter 13.
Analysts should also be familiar with the
EPA Science Policy Council's risk
characterization program documents which
discuss important aspects of writing and
communicating about risk (e.g., transparency
and clarity in discussions of potential risk).11
At the end of the written evaluation, the
analyst is encouraged to make statements
about their overall confidence in the
conclusions, including statements regarding
the air toxics that fail the screen and which
may require further evaluation (and,
conversely, whether chemicals that "pass the
screen" can reasonably be removed from
further consideration). These statements,
along with the full discussion of uncertainty
developed in Step 6 are key elements needed
by subsequent users of the analysis to
critically judge whether and how to use the
screening results in the decision making
process.
It is important to re-emphasize that the
resulting report from a preliminary screening
level analysis of this type is not a substitute
for a full risk characterization. The purpose
of developing a report that includes ancillary
data, an uncertainty discussion, and
statements about the analysts' confidence in
the conclusions is only to help decision
makers better understand the problem and
decide on next steps. Those next steps will
almost always include a more rigorous risk
evaluation of chemicals that, at a minimum,
failed the screen (e.g., developing 95% UCL
values from the full monitoring data set,
performing air dispersion and exposure
modeling, etc.) and may also include the
collection of additional data.
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APPENDIX A
CHRONIC SCREENING VALUES
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20 version 2
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As described in the main body of this
document, Appendix A provides chronic
inhalation screening values that are, for a
given entry, the lesser of screening values
for cancer and chronic noncancer health
effects. In order to make the process even
more straightforward for the screening
process (and at the same time remain
conservative), several additional simplifying
assumptions were made and incorporated
into this chronic screening value Appendix.
Specifically, several of the entries in
OAQPS's Toxicity Values Table 1 (see
http ://www. epa.gov/ttn/atw/toxsource/summ
ary.html) were combined into one entry in
this Appendix for screening level purposes.
The simplifications are as follows:
1. The OAQPS toxicity Table 1 entries
Antimony Compounds, Antimony
Pentoxide, Antimony Potassium
Tartrate, Antimony Tetroxide, and
Antimony Trioxide were condensed
into one entry (Antimony
Compounds) in this screening level
Appendix A. The toxicity data
utilized for this entry is that of
antimony trioxide, the only data
available for antimony or one of its
compounds in the OAQPS table.
2. The OAQPS toxicity Table 1 entries
Chromium (III) Compounds and
Chromium (VI) Compounds were
condensed into one entry (Chromium
Compounds) in this screening level
Appendix A. The toxicity data for
this entry is that of "Chromium (VI)
Compounds."
3. The OAQPS toxicity Table 1 entries
for Cyanide Compounds, Calcium
Cyanide, Copper Cyanide, Hydrogen
Cyanide, Potassium Cyanide,
Potassium Silver Cyanide, Silver
Cyanide, Sodium Cyanide, and Zinc
Cyanide were condensed into one
entry (Cyanide Compounds) in this
screening level Appendix A. The
toxicity value utilized for this entry is
that of hydrogen cyanide, the only
data available for cyanide or one of
its compounds in the OAQPS table.
The OAQPS toxicity Table 1 entries
for Mercuric Chloride, Mercury
(Elemental), Methyl Mercury, and
Phenylmercuric Acetate were
condensed into one entry (Mercury
Compounds) in this screening level
Appendix A. The toxicity data for
this entry is that of elemental
mercury. (Note that this screening
level methodology is focused on
inhalation only. As such, issues
associated with methyl mercury
ingestion are not incorporated into
this screening level Appendix A.)
The OAQPS toxicity Table 1 entries
for Nickel Compounds, Nickel Oxide,
Nickel Refinery Dust, and Nickel
Subsulfide were condensed into one
entry (Nickel Compounds) in this
screening level Appendix A. The
toxicity data for this entry is that of
"Nickel Compounds" for the
noncancer RfC and "Nickel
Subsulfide" for the cancer IUR.
The OAQPS toxicity Table 1 entries
for Selenium Compounds, Selenious
Acid, and Selenourea were
condensed into one entry (Selenium
Compounds) in this screening level
Appendix A. The toxicity data for
21
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this entry is that of Selenium
Compounds.
7. The OAQPS toxicity Table 1 entries
for Lindane (gamma-HCH), alpha-
Hexachlorocyclohexane (a-HCH),
beta-Hexachlorocyclohexane (b-
HCH), and technical
Hexachlorocyclohexane (HCH) were
condensed into one entry
[Hexachlorocyclohexane (HCH)] in
this screening level Appendix A.
The toxicity data for this entry is that
of lindane (gamma-HCH) for the
noncancer RfC and alpha-
Hexachlorocyclohexane (a-HCH) for
the cancer IUR.
Several other toxicity surrogates were used
for chemicals having no toxicity data, as
follows:
It should be noted that ethylene glycol
monobutyl ether was delisted from the list of
hazardous air pollutants (HAPs) on
November 29, 2004 (see Federal Register
Volume 69, Number 228, pp. 69320-69325).
Toxicity data for this chemical is presented
for informational purposes only.
Finally, it should also be noted that the
number of significant figures shown is
reflective of the number of significant
figures shown in the OAQPS toxicity table
from which these screening numbers were
drawn.
1. The toxicity value for "Cresols
(mixed)" was used as a surrogate for
each of the isomers o-, m-, and
p-cresol.
2. The toxicity value for "Xylenes
(mixed)" was used as a surrogate for
o- and m-xylenes.
3. The noncancer RfC for naphthalene
was used as a surrogate for the
noncancer toxicity of each of the
chemicals listed in the PAH grouping
(since none of these entries has a
unique RfC). Note that several of the
chemicals in the PAH grouping are
substituted.
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AppendixA Chronic Inhalation Screening Values
Based on OAQPS Toxicity Table 1
www.epa.gov/ttn/atw/toxsource/tablelxls
(4/27/2010)
Acetaldehyde
Acetamide
Acetonitrile
Acetophenone
Acrolein
Acrylamide
Acrylic acid
Acrylonitrile
Allyl chloride
Aniline
Antimony compounds (1)
Arsenic compounds
Arsine
Benzene
Benzidine
Benzo trichloride
Benzyl chloride
Beryllium compounds
Biphenyl
Bis(2-ethylhexyl)phthalate
Bis(chloromethyl)ether
Bromoform
1,3-Butadiene
Cadmium compounds
Captan
Carbaryl
Carbon disulfide
Carbon tetrachloride
Chloramben
Chlordane
Chlorine
Chloroacetic acid
2-Chloroacetophenone
Chlorobenzene
Chlorobenzilate
Chloroform
75-07-0
60-35-5
75-05-8
98-86-2
107-02-8
79-06-1
79-10-7
107-13-1
107-05-1
62-53-3
Various
7440-38-2
7784-42-1
71-43-2
92-87-5
98-07-7
100^4-7
7440-41-7
92-52-4
117-81-7
542-88-1
75-25-2
106-99-0
7440-43-9
133-06-2
63-25-2
75-15-0
56-23-5
133-90-4
57-74-9
7782-50-5
79-11-8
532-27^
108-90-7
510-15-6
67-66-3
Noncancer at
HQ = 0.1
ug/m3
9.E-01
6.E+00
2.E-03
6.E-01
1.E-01
2.E-01
1.E-01
1.E-01
2.E-02
1.5E-03
5.E-03
3.E+00
1.E+00
2.E-03
1.E+00
2.E-01
1.E-03
7.E+01
1.0E+01
7.E-02
1.5E-02
3.E-03
1.E+02
9.8E+00
Cancer at 1 x 10~6
Risk Level
ug/m3
4.5E-01
5.E-02
1.E-02
1.5E-02
2.E-01
6.3E-01
2.3E-04
1.3E-01
1.5E-05
2.7E-04
2.0E-02
4.2E-04
4.2E-01
1.6E-05
9.1E-01
3.E-02
5.6E-04
1.E+00
1.7E-01
1.E-02
1.3E-02
FINAL SCREENING
VALUE
ug/m3
4.5E-01
5.E-02
6.E+00
No Value
2.E-03
1.E-02
1.E-01
1.5E-02
1.E-01
1.E-01
2.E-02
2.3E-04
5.E-03
1.3E-01
1.5E-05
2.7E-04
2.0E-02
4.2E-04
No Value
4.2E-01
1.6E-05
9.1E-01
3.E-02
5.6E-04
1.E+00
No Value
7.E+01
1.7E-01
No Value
1.E-02
1.5E-02
No Value
3.E-03
1.E+02
1.3E-02
9.8E+00
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Appendix A Chronic Inhalation Screening Values
Based on OAQPS Toxicity Table 1
www.epa.gov/ttn/atw/toxsource/table1.xls
(4/27/2010)
Chloroprene
Chromium Compounds (2)
Chromium (Vl)trioxide,
chromic acid mist
Cobalt compounds
Coke Oven Emissions
m-Cresol (3)
o-Cresol (3)
p-Cresol (3)
Cresols (mixed)
Cumene
Cyanazine
Cyanide Compounds (4)
Acetone cyanohydrin
Cyanogen
Cyanogen bromide
Cyanogen chloride
Ethylene cyanohydrin
Thiocyanic acid, 2-
(benzothiazolylthio) methyl
est
2,4-D, salts and esters
DDE
1,2-Dibromo-3-
chloropropane
Dibutylphthalate
p-Dichlorobenzene
3,3'-Dichlorobenzidine
Dichloroethyl ether
1,3-dichloropropene
Dichlorvos
Diesel engine emissions
Diethanolamine
3,3'-Dimethoxybenzidine
p-Dimethylaminoazobenzene
126-99-8
Various
11115-74-5
7440-48-4
8007-45-2
108-39-4
95-48-7
106-44-5
1319-77-3
98-82-8
21725-46-2
Various
75-86-5
460-19-5
506-68-3
506-77-4
109-78-4
21564-17-0
94-75-7
72-55-9
96-12-8
84-74-2
106-46-7
91-94-1
111-44-4
542-75-6
62-73-7
DIESEL EMIS.
111-42-2
119-90-4
60-11-7
Noncancer at
HQ = 0.1
ug/m3
7.E-01
1.E-02
8.E-04
1.E-02
6.E+01
6.E+01
6.E+01
6.E+01
4.E+01
3.E-01
1.E+00
2.E-02
8.E+01
2.E+00
5.E-02
5.E-01
3.E-01
Cancer at 1 x 10~6
Risk Level
ug/m3
8.3E-05
1.6E-03
4.2E-03
1.0E-02
5.E-04
9.1E-02
2.9E-03
3.0E-03
3.E-01
1.2E-02
3.E-01
7.7E-04
FINAL SCREENING
VALUE
ug/m3
7.E-01
8.3E-05
8.E-04
1.E-02
1.6E-03
6.E+01
6.E+01
6.E+01
6.E+01
4.E+01
4.2E-03
3.E-01
1.E+00
No Value
No Value
No Value
No Value
No Value
No Value
1.0E-02
5.E-04
No Value
9.1E-02
2.9E-03
3.0E-03
3.E-01
1.2E-02
5.E-01
3.E-01
3.E-01
7.7E-04
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Appendix A Chronic Inhalation Screening Values
Based on OAQPS Toxicity Table 1
www.epa.gov/ttn/atw/toxsource/table1.xls
(4/27/2010)
3,3'-Dimethylbenzidine
Dimethyl formamide
N,N-dimethylaniline
1 ,1-Dimethylhydrazine
2,4-dinitrophenol
2,4-Dinitrotoluene
2,4/2,6-Dinitrotoluene
(mixture)
1,4-Dioxane
1 ,2-Diphenylhydrazine
Epichlorohydrin
1,2-Epoxybutane
Ethyl acrylate
Ethyl benzene
Ethyl carbamate
Ethyl chloride
Ethyiene dibromide
Ethyiene dichloride
Ethyiene glycol
Ethyiene oxide
Ethyiene thiourea
Ethyl idene dichloride (1,1-
Dichloroethane)
Formaldehyde
Diethylene glycol monobutyl
ether
Diethylene glycol monoethyl
ether
Ethyiene glycol butyl ether
(5)
Ethyiene glycol ethyl ether
Ethyiene glycol ethyl ether
acetate
Ethyiene glycol methyl ether
Ethyiene glycol methyl ether
acetate
Heptachlor
Hexachlorobenzene
Hexachlorobutadiene
119-93-7
68-12-2
121-69-7
57-14-7
51-28-5
121-14-2
25321-14-6
123-91-1
122-66-7
106-89-8
106-88-7
140-88-5
100-41-4
51-79-6
75-00-3
106-93^
107-06-2
107-21-1
75-21-8
96-45-7
75-34-3
50-00-0
112-34-5
111-90-0
111-76-2
110-80-5
111-15-9
109-86^
110-49-6
76-44-8
118-74-1
87-68-3
Noncancer at
HQ=0.1
ug/m3
3.E+00
7.E-01
3.6E+02
1.E-01
2.E+00
1.E+02
1.E+03
9.E-01
2.4E+02
4.E+01
3.E+00
3.E-01
5.E+01
9.8E-01
2.E+00
1.3E+03
2.E+01
3.E+01
2.E+00
9.E+00
3.E-01
9.E+00
Cancer at 1 x 10~6
Risk Level
ug/m3
3.8E-04
1.1E-02
5.3E-03
1.3E-01
4.5E-03
8.3E-01
4.E-01
3.4E-03
2.E-03
3.8E-02
1.1E-02
7.7E-02
6.3E-01
7.7E-02
7.7E-04
2.2E-03
4.5E-02
FINAL SCREENING
VALUE
ug/m3
3.8E-04
3.E+00
No Value
No Value
No Value
1.1E-02
5.3E-03
1.3E-01
4.5E-03
1.E-01
2.E+00
4.E-01
3.4E-03
1.E+03
2.E-03
3.8E-02
4.E+01
1.1E-02
7.7E-02
6.3E-01
7.7E-02
2.E+00
No Value
1.3E+03
2.E+01
3.E+01
2.E+00
9.E+00
7.7E-04
2.2E-03
4.5E-02
25
version 2
-------
Appendix A Chronic Inhalation Screening Values
Based on OAQPS Toxicity Table 1
www.epa.gov/ttn/atw/toxsource/tablelxls
(4/27/2010)
Hexachlorocyclohexane
(HCH)(6)
Hexachlorocyclopentadiene
Hexachlorodibenzo-p-dioxin,
mixture
Hexachloroethane
Hexamethylene-1 ,6-
diisocyanate
n-Hexane
Hydrazine
Hydrochloric acid
Hydrofluoric acid
Hydrogen sulfide
Hydroquinone
Isophorone
Lead compounds (7)
Tetra ethyl lead
Maleic anhydride
Manganese compounds
Mercury compounds (8)
Methanol
Methoxychlor
Methyl bromide
Methyl chloride
Methyl chloroform (1,1,1-
Trichloroethane)
Methyl ethyl ketone
Methyl isobutyl ketone
Methyl isocyanate
Methyl methacrylate
Methyl tert-butyl ether
4,4'-Methylene bis(2-
chloroaniline)
Methylene chloride
Methylene diphenyl
diisocyanate
4,4'-Methylenedianiline
Nickel compounds (9)
Nitrobenzene
Various
77-47-4
19408-74-3
67-72-1
822-06-0
110-54-3
302-01-2
7647-01-0
7664-39-3
7783-06-4
123-31-9
78-59-1
7439-92-1
78-00-2
108-31-6
7439-96-5
Various
67-56-1
72-43-5
74-83-9
74-87-3
71-55-6
78-93-3
108-10-1
624-83-9
80-62-6
1634-04-4
101-14-4
75-09-2
101-68-8
101-77-9
Various
98-95-3
Noncancer at
HQ = 0.1
ug/m3
3.E-02
2.E-02
8.E+00
1.E-03
7.E+01
2.E-02
2.E+00
1.4E+00
2.E-01
2.E+02
1.5E-02
7.E-02
5.E-03
3.E-02
4.E+02
5.E-01
9.E+00
5.E+02
5.E+02
3.E+02
1.E-01
7.E+01
3.E+02
1.E+02
6.E-02
2.E+00
9.E-03
9.E-01
Cancer at 1 x 10"6
Risk Level
ug/m3
5.6E-04
7.7E-07
3.E-01
2.0E-04
3.7E+00
3.8E+00
2.3E-03
2.1E+00
2.2E-03
2.1E-03
2.5E-02
FINAL SCREENING
VALUE
ug/m3
5.6E-04
2.E-02
7.7E-07
3.E-01
1.E-03
7.E+01
2.0E-04
2.E+00
1.4E+00
2.E-01
No Value
3.7E+00
1.5E-02
No Value
7.E-02
5.E-03
3.E-02
4.E+02
No Value
5.E-01
9.E+00
5.E+02
5.E+02
3.E+02
1.E-01
7.E+01
3.8E+00
2.3E-03
2.1E+00
6.E-02
2.2E-03
2.1E-03
2.5E-02
26
version 2
-------
Appendix A Chronic Inhalation Screening Values
Based on OAQPS Toxicity Table 1
www.epa.gov/ttn/atw/toxsource/table1.xls
(4/27/2010)
Noncancer at
HQ=0.1
ug/m3
Cancer at 1x10"'
Risk Level
ug/m3
FINAL SCREENING
VALUE
ug/m
2-Nitropropane
79-46-9
2.E+00
1.8E-01
1.8E-01
Nitrosodimethylamine
62-75-9
7.1E-05
7.1E-05
N-Nitrosomorpholine
59-89-2
5.3E-04
5.3E-04
Pa rath ion
56-38-2
No Value
Polychlorinated biphenyls
1336-36-3
1.E-02
1.E-02
Aroclor 1016
12674-11-2
No Value
Aroclor 1254
11097-69-1
No Value
Pentachloronitrobenzene
82-68-8
1.4E-02
1.4E-02
Pentachlorophenol
87-86-5
1.E+01
2.0E-01
2.0E-01
Phenol
108-95-2
2.E+01
2.E+01
p-Phenylenediamine
106-50-3
No Value
Phosgene
75-44-5
3.E-02
3.E-02
Phosphine
7803-51-2
3.E-02
3.E-02
Phosphorus, white
7723-14-0
7.E-03
7.E-03
Phthalic anhydride
85-44-9
2.E+00
Begin Polycyclic Aromatic
Hydrocarbons (PAHs) (10)
Acenaphthene
83-32-9
3.E-01
2.E+00
3.E-01
Acenaphthyiene
206-96-8
3.E-01
3.E-01
Anthracene
120-12-7
3.E-01
3.E-01
Benzo(a)anthracene
56-55-3
3.E-01
9.1E-03
9.1E-03
Benzo(b)fluoranthene
205-99-2
3.E-01
9.1E-03
9.1E-03
Benzo[j]fluoranthene
205-82-3
3.E-01
9.1E-03
9.1E-03
Benzo(k)fluoranthene
207-08-9
3.E-01
9.1E-03
9.1E-03
Benzo(g,h,i)perylene
191-24-2
3.E-01
3.E-01
Benzo(a)pyrene
50-32-8
3.E-01
9.1E-04
9.1E-04
Benzo(e)pyrene
192-97-2
3.E-01
3.E-01
Carbazole
86-74-8
3.E-01
1.8E-01
1.8E-01
beta-Chloronaphthalene
91-58-7
3.E-01
3.E-01
Chrysene
218-01-9
3.E-01
9.1E-02
9.1E-02
Dibenz[a,h]acridine
226-36-8
3.E-01
9.1E-03
9.1E-03
Dibenz[aj]acridine
224-42-0
3.E-01
9.1E-03
9.1E-03
Dibenz(a,h)anthracene
53-70-3
3.E-01
8.3E-04
8.3E-04
7H-Dibenzo[c,g]carbazole
194-59-2
3.E-01
9.1E-04
9.1E-04
27
version 2
-------
Appendix A Chronic Inhalation Screening Values
Based on OAQPS Toxicity Table 1
www.epa.gov/ttn/atw/toxsource/table1.xls
(4/27/2010)
Dibenzo[a,e]pyrene
Dibenzo[a,h]pyrene
Dibenzo[a,i]pyrene
Dibenzo[a,l]pyrene
7,12-
Dimethylbenz(a)anthracene
1 ,6-Dinitropyrene
1 ,8-Dinitropyrene
Fluoranthene
Fluorene
lndeno(1 ,2,3-cd)pyrene
3-Methylcholanthrene
5-Methylchrysene
1-Methylnaphthalene
2-Methylnaphthalene
Naphthalene
5-Nitroacenaphthene
6-Nitrochrysene
2-Nitrofluorene
1-Nitropyrene
4-Nitropyrene
Phenanthrene
Pyrene
End PAH Listings
1,3-Propane sultone
Propionaldehyde
Propoxur
Propylene dichloride
Propylene oxide
Quinoline
Selenium compounds (11)
Hydrogen selenide
Styrene
Styrene oxide
2,3,7,8-Tetrachlorodibenzo-p
dioxin
1 ,1 ,2,2-Tetrachloroethane
Tetrachloroethene
Titanium tetrachloride
Toluene
192-65-4
189-64-0
189-55-9
191-30-0
57-97-6
42397-64-8
42397-65-9
206^4-0
86-73-7
193-39-5
56-49-5
3697-24-3
90-12-0
91-57-6
91-20-3
602-87-9
7496-02-8
607-57-8
5522-43-0
57835-92-4
85-01-8
129-00-0
^^H
1120-71-4
123-38-6
114-26-1
78-87-5
75-56-9
91-22-5
Various
7783-07-5
100^2-5
96-09-3
1746-01-6
79-34-5
127-18-4
7550-45-0
108-88-3
Noncancer at
HQ = 0.1
ug/m3
3.E-01
3.E-01
3.E-01
3.E-01
3.E-01
3.E-01
3.E-01
3.E-01
3.E-01
3.E-01
3.E-01
3.E-01
3.E-01
3.E-01
3.E-01
3.E-01
3.E-01
3.E-01
3.E-01
3.E-01
3.E-01
3.E-01
^^^
8.E-01
4.E-01
3.E+00
2.E+00
8.E-03
1.E+02
6.E-01
4.E-06
2.7E+01
1.E-02
4.E+01
Cancer at 1 x 10~6
Risk Level
ug/m3
9.1E-04
9.1E-05
9.1E-05
9.1E-05
1.4E-05
9.1E-05
9.1E-04
9.1E-03
1.6E-04
9.1E-04
2.9E-02
2.7E-02
9.1E-05
9.1E-02
9.1E-03
9.1E-03
^^^m
1.4E-03
5.3E-02
2.7E-01
3.0E-08
1.7E-02
1.7E-01
FINAL SCREENING
VALUE
ug/m3
9.1E-04
9.1E-05
9.1E-05
9.1E-05
1.4E-05
9.1E-05
9.1E-04
3.E-01
3.E-01
9.1E-03
1.6E-04
9.1E-04
3.E-01
3.E-01
2.9E-02
2.7E-02
9.1E-05
9.1E-02
9.1E-03
9.1E-03
3.E-01
3.E-01
^^^M
1.4E-03
8.E-01
No Value
5.3E-02
2.7E-01
No Value
2.E+00
8.E-03
1.E+02
6.E-01
3.0E-08
1.7E-02
1.7E-01
1.E-02
4.E+01
28
version 2
-------
Appendix A Chronic Inhalation Screening Values
Based on OAQPS Toxicity Table 1
www.epa.gov/ttn/atw/toxsource/tablelxls
(4/27/2010)
2,4-Toluene diamine
2,4/2,6-Toluene
diisocyanate mixture (TDI)
o-Toluidine
Toxaphene
1 ,2,4-Trichlorobenzene
1,1,2-Trichloroethane
Trichloroethylene
2,4,5-Trichlorophenol
2,4,6-Trichlorophenol
Triethylamine
Trifluralin
Uranium compounds
Uranium, soluble salts
Vinyl acetate
Vinyl bromide
Vinyl chloride
Vinylidene chloride
m-Xyiene(12)
o-Xylene(12)
Xylenes (mixed)
95-80-7
26471-62-5
95-53^
8001-35-2
120-82-1
79-00-5
79-01-6
95-95-4
88-06-2
121-44-8
1582-09-8
7440-61-1
URANSOLS
108-05-4
593-60-2
75-01-4
75-35-4
108-38-3
95-47-6
1330-20-7
Noncancer at
HQ=0.1
ug/m3
7.E-03
2.E+01
4.E+01
6.E+01
7.E-01
3.E-02
2.E+01
3.E-01
1.E+01
2.E+01
1.E+01
1.E+01
1.E+01
Cancer at 1 x 10~6
Risk Level
ug/m3
9.1E-04
9.1E-02
2.0E-02
3.1E-03
6.3E-02
5.E-01
3.2E-01
4.5E-01
3.1E-02
1.1E-01
FINAL SCREENING
VALUE
ug/m3
9.1E-04
7.E-03
2.0E-02
3.1E-03
2.E+01
6.3E-02
5.E-01
No Value
3.2E-01
7.E-01
4.5E-01
3.E-02
No Value
2.E+01
3.1E-02
1.1E-01
2.E+01
1.E+01
1.E+01
1.E+01
29
version 2
-------
Table Notes
See the discussion at the beginning of this Appendix for a more full discussion of the following
endnotes.
(1) The toxicity data for this entry is that of antimony trioxide in the OAQPS chronic toxicity
values Table 1, the only data available for antimony or one of its compounds.
(2) The toxicity data for this entry is that of "chromium (VI) compounds" in the OAQPS
chronic toxicity values Table 1.
(3) The toxicity value for "cresols (mixed)" was used as a surrogate for o-, m-, and p-cresol.
(4) The toxicity value for this entry is that of hydrogen cyanide in the OAQPS chronic
toxicity values Table 1.
(5) Ethylene glycol butyl ether was delisted from the list of hazardous air pollutants (HAPs)
on November 29, 2004 ( see Federal Register Volume 69, Number 228, pp. 69320-69325).
Toxicity data for this chemical is presented for informational purposes.
(6) The toxicity data for this entry is that of "lindane (gamma-HCH) for the noncancer RfC
and "alpha-hexachlorocyclohexane (a-HCH)" for the cancer IUR in the OAQPS chronic
toxicity values Table 1.
(7) Note that the National Ambient Air Quality Standard (NAAQS) for lead is 1.5 ug/m3
(quarterly average). See http://www.epa.gov/air/criteria.html.
(8) The toxicity data for this entry is that of elemental mercury in the OAQPS chronic toxicity
values Table 1.
(9) The toxicity data for this entry is that of "nickel compounds" for the noncancer RfC and
"nickel subsulfide" for the cancer IUR in the OAQPS chronic toxicity values Table 1.
(10) The noncancer RfC for naphthalene in the OAQPS chronic toxicity values Table 1 was
used as a surrogate for the noncancer toxicity of each of the chemicals listed in the PAH
grouping (since none of the entries has a unique RfC). Note that several of the chemicals
in the PAH grouping are substituted.
(11) The toxicity data for this entry is that of selenium compounds in the OAQPS chronic
toxicity values Table 1.
(12) The toxicity value for "Xylenes (mixed)" was used as a surrogate for o- and m-xylenes.
30 version 2
-------
APPENDIX B
ACUTE SCREENING ANALYSIS
31 version 2
-------
(This page intentionally left blank.)
32 version 2
-------
The basic process for screening a monitoring
data set for potential acute exposure issues is
similar to the way the same data set is
evaluated for chronic issues (i.e., simply
comparing the maximum value found in the
data set to an identified screening value).
However, there are several key differences
between chronic and acute analysis of which
the analyst must be aware.
One difference is that in the chronic screen,
the screening value is the lower of values for
both cancer and noncancer health effects. In
acute analysis, only noncancer effects are
considered (OAQPS does not currently
recommend an evaluation of cancer
outcomes resulting from acute exposures).
Another key difference is that while there is
only one final screening value for chronic
analysis in Appendix A, there are multiple
possible acute screening values in Appendix
B against which to compare the monitoring
results. [Note that Appendix B only presents
the selection of available acute values
currently provided by OAQPS (see endnote
2 and the descriptions provided on that
webpage). If analysts use additional acute
values in their evaluation, they are
encouraged to document why they were
selected and how they were used.]
There are a number of issues that have led
OAQPS to simply identify a variety of acute
toxicity values for the HAPs, rather than
recommend one value for risk-based acute
analysis, including:
Acute toxicity values have been
developed for purposes that vary
more widely than chronic values.
Some types of acute values are
designed to be estimates of exposures
at or below which there is little risk
of adverse effects, while others are
intended to predict exposures at or
above which adverse effects could
occur.
• Some acute values are expressed as
concentration-time matrices (i.e.,
different allowable concentrations for
different exposure times), while
others are expressed as single
concentrations for a set exposure
duration.
• Some acute values may specifically
consider multiple exposures, whereas
others consider exposure as a
one-time event.
• Some sources of acute values are
intended to regulate workplace
exposures, assuming a population of
healthy workers exposed for a limited
period of time each day (i.e.,
children, seniors, or other sensitive
individuals are not considered). Such
occupational values may also
consider cost and feasibility, factors
that would be inappropriate for the
type of screening approach described
here. [See Chapters 12 and 13 of
Volume 1 of the ATRA Reference
Library for more detail on the subject
of acute toxicity value development
and acute risk characterization,
respectively. Analysts are
encouraged to read and become
familiar with this material and the
descriptive material associated with
the OAQPS acute toxicity values
table before proceeding.]
For this risk-based screening approach, a
toxicologist with experience in this area
should generally evaluate acute noncancer
hazard by comparing the maximum
monitored value to the variety of acute
values presented in this appendix and other
33
version 2
-------
relevant acute values, and then discussing
the comparisons by considering the
characteristics of the acute screening values,
such as their purpose, averaging time, and
health endpoints.
EPA is just beginning to develop acute
reference exposure values for some
pollutants [see, for example, U.S. EPA.
2004. Integrated Risk Information System
(IRIS); Announcement of 2004 Program;
Request for Information. FR 69(26)5971-
5976] which will lead to improvements in
acute risk assessment for air toxics.
In order to assist analysts understand and
apply the acute toxicity values appropriately,
a short explanation of each of the types of
values presented in Appendix B is provided
below. A more lengthy discussion of each is
provided in the ATRA Reference Library,
Volume 1, Chapter 12.
Sources of Acute Dose-
Response Information In
Appendix B
Hazard identification and dose-response
assessment information for acute exposure in
Appendix B was obtained from the following
sources:
US Agency for Toxic Substances
and Disease Registry (ATSDR). In
addition to its chronic minimum risk
levels (MRLs), ATSDR also
develops MRLs for acute exposure.
As with chronic values, acute MRLs
are estimates of human exposure to a
substance that is likely to be without
an appreciable risk of adverse effects
3.
(other than cancer) over a specified
duration of exposure, and can be
derived for acute exposures by the
inhalation and oral routes. Acute
MRLs are published as part of
pollutant-specific toxicological
profile documents, and also in a table
that ATSDR regularly updates and
distributes (available on-line at
http://www.atsdr.cdc.gov/mrls.html).
Unlike the one-hour focus of many of
the other values listed here, acute
MRLs are derived for exposures of 1
to 14 days.
California Environmental
Protection Agency (CalEPA)
CalEPA has developed acute dose-
response assessments for many
substances, expressing the results as
acute inhalation Reference Exposure
Levels (RELs). As with its chronic
RELs, CalEPA defines the acute REL
as a concentration level at (or below)
which no health effects are
anticipated. Most, but not all, of the
acute RELs are derived for exposures
of one hour. CalEPA's acute RELs
are available on-line at:
http://www.oehha.ca. gov/air/acute_re
Is/index.html.
National Advisory Committee for
Acute Exposure Guideline Levels
(NAC). EPAs Office of Prevention,
Pesticides and Toxic Substances
established the NAC in 1995 to
develop Acute Exposure Guideline
Levels (AEGLs) and supplementary
information on hazardous substances
for federal, state, and local agencies
and organizations in the private
sector concerned with emergency
34
version 2
-------
planning, prevention, and response.
The NAC/AEGL Committee is a
discretionary Federal advisory
committee that combines the efforts
of stakeholders from the public and
private sectors to promote efficiency
and utilize sound science.
The NAC published an initial priority
list of 85 chemicals for AEGL
development in May 1997 and has
since proposed AEGLs for additional
substances. The AEGLs for a
substance take the form of a matrix,
with separate ambient levels for mild
(AEGL-1), moderate (AEGL-2), and
severe (AEGL-3) effects. Each of
the effect levels are provided for as
many as four different exposure
periods, typically 0.5, 1, 4, and 8
hours. Appendix B provides only the
1-hour and 8-hour values for AEGLs
1 and 2 effect levels, and includes a
superscript that identifies whether the
value is final, interim, or proposed.
For more information on the AEGL
program, see
http ://www. epa.gov/opptintr/aegl/ind
ex.htm. (In the Appendix B table for
AEGLs: f = final i = interim p =
proposed.)
American Industrial Hygiene
Association (AIHA). AIHA has
developed emergency response
planning guidelines (ERPGs) for
acute exposures at three different
levels of severity of health effects.
These guidelines (available on-line
through the US Department of
Energy at
http://www.orau.gov/emi/scapa/teels.
htm) represent concentrations for
exposure of the general population
for up to 1 hour associated with
effects expected to be mild or
transient (ERGP-1), irreversible or
serious (ERPG-2), and potentially
life-threatening or lethal (ERPG-3).
Appendix B includes ERPG values
for ERPG 1 and 2 effect levels.
National Institute for Occupational
Safety and Health (NIOSH) As
part of its mission to study and
protect worker health, NIOSH
determines concentrations of
substances that are Immediately
Dangerous to Life or Health
(IDLHs). IDLHs were originally
determined for 387 substances in the
mid-1970's as part of the Standards
Completion Program (SCP), a joint
project by NIOSH and the
Occupational Safety and Health
Administration (OSHA), for use in
assigning respiratory protection
equipment. NIOSH is currently
evaluating the scientific adequacy of
the criteria and procedures used
during the SCP for establishing
IDLHs. In the interim, the IDLHs
have been reviewed and revised.
NIOSH maintains an on-line database
(http://www.cdc.gov/niosh/idlh/idlh-
1 .html) of IDLHs, including the basis
and references for both the current
and original IDLH values (as
paraphrased from the SCP draft
technical standards). Appendix B
provides IDLH values divided by 10
to more closely match the mild-effect
levels developed by other sources,
consistent with methodology used to
develop levels of concern under Title
III of the Superfund Amendments
and Reauthorization Act, and their
35
version 2
-------
use in the accidental release
prevention requirements under
section 112(r) of the Clean Air Act.
The IDLH/10 values have commonly
been used as "levels of concern" in
emergency planning programs such
as Clean Air Act 112(r).12 The
averaging time for the IDLH/10
values is one hour.
mild, transient effects (TEEL-1),
irreversible or serious effects (TEEL-
2), and potentially life-threatening
(TEEL-3). Consistent with DOE's
intent, Appendix B provides the
TEEL-0 and -1 concentrations for
substances that lack acute values
from other sources. The averaging
time for TEELs is 15 minutes.
U.S. Department of Energy (DOE).
DOE has defined Temporary
Emergency Exposure Limits
(TEELs), which are temporary levels
of concern (LOCs) derived according
to a tiered, formula-like methodology
(described at
http://www.orau.gov/emi/scapa/Meth
od_for_deriving_TEELs.pdf and
available on-line at
http ://www. atlintl. com/DOE/teels/tee
l/teel_pdfhtml). DOE has developed
TEELs with the intention of
providing a reference when no other
LOG is available. DOE describes
TEELs as "approximations of
potential values" and "subject to
change." The EPA's emergency
planning program (section 112(r))
does not generally rely on them, and
they are provided in the OAQPS
Table 2 (and in this Appendix) purely
to inform situations in which no other
acute values are available. For
example, a finding of an acute
exposure near a TEEL may indicate
the need for a more in-depth
investigation into the health effects
literature. TEELs are not
recommended as the basis of
regulatory decision-making. Like
ERPGs, TEELs are multiple-tiered,
representing concentrations
associated with no effects (TEEL-0),
36
version 2
-------
Acute Dose-Response Values for Screening
Risk Assessments (Based on OAQPS Toxicity
Table 2; 4/27/2010)
CHEMICAL NAME
Acetaldehyde
Acetamide
Acetonitrile
Acetophenone
2-Acetylaminofluorene
Acrolein
Acrylamide
Acrylic acid
Acrylonitrile
Allyl chloride
4-Aminobiphenyl
Aniline
Anisidine
Antimony compounds
Antimony pentafluoride
Antimony potassium tartrate
Antimony trihydride
Antimony trioxide
Arsenic chloride
Arsenic compounds
Arsenic oxide
Arsenic pentoxide
Arsine
Asbestos
Benzene
Benzidine
Benzol richloride
Benzyl chloride
Beryllium chloride
Beryllium compounds
Beryllium fluoride
Beryllium nitrate
Beryllium oxide
Biphenyl
Bis(2-ethylhexyl)phthalate
Bis(chloromethyl)ether
Bromoform
1,3-Butadiene
Cadmium compounds
CAS NO.
75-07-0
60-35-5
75-05-8
98-86-2
53-96-3
107-02-8
79-06-1
79-10-7
107-13-1
107-05-1
92-67-1
62-53-3
90-04-0
7440-36-0
7783-70-2
304-61-0
7803-52-3
1309-64-4
7784-34-1
7440-38-2
1327-53-3
1303-28-2
7784-42-1
1332-21-4
71-43-2
92-87-5
98-07-7
100-44-7
7787-47-5
7440-41-7
7787-49-7
13597-99-4
1304-56-9
92-52-4
117-81-7
542-88-1
75-25-2
106-99-0
7440-43-9
AEGL-1 (1-h)
mg/m3
81 '
22 ''
0.069 ''
4.4'
10 p
8.8 '
30 f
170 '
1500 ''
AE3L-1 (8-h)
mg/m3
81 '
22 ''
0.069 ''
4.4'
10 p
8.8 '
3.8 f
/
/
f
29'
/
/
1500 !
AE3L-2 (1-h)
mg/m3
490'
540 !
0.23 ''
140 !
130 p
170 '
46 f
7.7 '
3'
0.54 f
2600'
61 '
0.21 '
12000 ''
AE3L-2 (8-h)
mg/m3
200'
140 !
0.23 ''
41 ''
19 p
69 '
5.7 f
0.92 '
1.2'
0.064 f
640'
28'
0.094 '
6000 !
ERPG-1
mg/m3
81
0.069
4.4
22
9.4
170
5.2
1500
ERPG-2
mg/m3
490
0.23
140
77
130
0.54
2600
52
0.025
0.47
12000
MRL
mg/m3
0.0069
0.22
0.029
0.00003
PEL
mg/m3
0.47
0.0025
6
0.0002
0.00019
0.16
1.3
0.24
IDLH/10
mg/m3
360
84
0.46
6
19
78
38
5
5
0.5
0.96
160
5.2
0.4
880
440
0.9
TEEL-0
mg/m3
25
10
0.25
0.5
0.75
1.2
0.6
0.19
0.005
0.15
0.1
0.015
0.01
0.03
0.005
5
TEEL-1
mg/m3
75
30
0.75
1.5
0.75
4
1.5
0.56
0.5
0.5
0.1
0.04
0.025
0.075
10
37
version 2
-------
Acute Dose-Response Values for Screening
Risk Assessments (Based on OAQPS Toxicity
Table 2; 4/27/2010)
CHEMICAL NAME
Cadmium stearate
Calcium cyanamide
Captan
Carbaryl
Carbon disulfide
Carbon tetrachloride
Carbonyl sulfide
Catechol
Chloramben
Chlordane
Chlorine
Chloroacetic acid
2-Chloroacetophenone
Chloro benzene
Chlorobenzilate
Chloroform
Chloromethyl methyl ether
Chloro prene
Chromium (III) compounds
Chromium (VI) compounds
Chromium (VI) trioxide, chromic
acid mist
Chromium chloride
Chromium compounds
Cobalt bromide
Cobalt carbonate
Cobalt carbonyl
Cobalt chloride
Cobalt compounds
Cobalt hydrocarbonyl
Cobalt nitrate
Cobalt oxides (mixed)
Coke Oven Emissions
m-Cresol
o-Cresol
p-Cresol
Cresols (mixed)
Cumene
Cyanophos
CAS NO.
2223-93-0
156-62-7
133-06-2
63-25-2
75-15-0
56-23-5
463-58-1
120-80-9
133-90-4
57-74-9
7782-50-5
79-11-8
532-27-4
108-90-7
510-15-6
67-66-3
107-30-2
126-99-8
16065-83-1
18540-29-9
11115-74-5
10025-73-7
7440-47-3
7789-43-7
513-79-1
10210-68-1
7646-79-9
7440-48-4
16842-03-8
Co Nitrate
COBOXIDES
8007-45-2
108-39-4
95-48-7
106-44-5
1319-77-3
98-82-8
2636-26-2
AEGL-1 (1-h)
mg/m3
40 f
280 '
1.5 f
46'
250 !
AEGL-1 (8-h)
mg/m3
21 '
120 '
/
1.5 f
f
46'
;
250 !
AEGL-2(1-h|
mg/m3
500 f
1200 '
140 '
5.8 f
26 '
690 '
310 !
1.6 '
1500 !
AEGL-2(8-h|
mg/m3
160 f
510 '
57'
2.1 f
3.2 '
690 '
140 !
0.731
640 !
ERPG-1
mg/m3
40
280
1.5
0.13
ERPG-2
mg/m3
500
1200
5.8
310
1.6
0.13
MRL
mg/m3
0.2
0.49
PEL
mg/m3
6.2
1.9
0.21
0.15
IDLH/10
mg/m3
10
160
130
10
2.9
460
240
110
1.5
1.5
2
110
110
110
110
440
TEEL-0
mg/m3
0.03
0.5
5
23
35
0.075
1.5
1
0.2
0.12
0.27
0.12
0.15
0.075
0.1
1.2
TEEL-1
mg/m3
0.15
1.5
15
68
100
0.25
4
1.5
0.2
0.12
0.27
0.12
0.15
0.075
1.2
3.5
38
version 2
-------
Acute Dose-Response Values for Screening
Risk Assessments (Based on OAQPS
Toxicity Table 2; 4/27/2010)
CHEMICAL NAME
Cyanide compounds
Acetone cyanohydrin
Barium cyanide
Calcium cyanide
Copper cyanide
Cyanogen
Cyanogen bromide
Cyanogen chloride
Cyanogen iodide
Hydrogen cyanide
Potassium cyanide
Potassium silver cyanide
Potassium thiocyanate
Silver cyanide
Sodium cyanide
Zinc cyanide
2,4-D, salts and esters
DDE
Diazomethane
Dibenzofuran
^,J,4,/,0-
Pentachlorodibenzofuran
1 ,2-Dibromo-3-chloropropane
Dibutylphthalate
p-Dichlorobenzene
3,3'-Dichlorobenzidine
Dichloroethyl ether
1,3-Dichloropropene
Dichlorvos
Diesel engine emissions
Diethanolamine
Di ethyl sulfate
N,N-diethyl/dimethylaniline
CAS NO.
57-12-5
75-86-5
542-62-1
592-01-8
544-92-3
460-19-5
506-68-3
506-77-4
506-78-5
74-90-8
151-50-8
506-61-6
333-20-0
506-64-9
143-33-9
557-21-1
94-75-7
72-55-9
334-88-3
1 32-64-9
57117-31-4
96-12-8
84-74-2
106-46-7
91-94-1
111-44-4
542-75-6
62-73-7
EMIS.
111-42-2
64-67-5
Dialks
AEGL-1 (1-h)
mg/m3
7 r
3.8 "
4.3 "
2.2 f
0.99 "
AEGL-1 (8-h)
mg/m3
3.5 r
1.9 p
2.1 "
1.1 f
0.99 "
AEGL-2(1-h)
mg/m3
25 r
13 "
18 "
7.8 f
5.1 "
AEGL-2 (8-h)
mg/m3
8.7 r
4.7 '
9.2 "
2.8 f
5.1 "
ERPG-1
mg/m3
ERPG-2
mg/m3
1
7.8
MRL
mg/m3
12
0.018
REL
mg/m3
0.34
IDLH/10
mg/m3
2.5
5.5
10
400
90
58
10
TEEL-0
mg/m3
0.6
1.2
20
35
5
1
10
25
5
20
10
0.34
10
3E-05
0.0097
2.1
4.5
35
2
1.9
TEEL-1
mg/m3
2
4
44
100
5
3
35
25
5
20
30
1
30
8E-05
0.029
6.2
14
100
6
4.7
39
version 2
-------
Acute Dose-Response Values for Screening
Risk Assessments (Based on OAQPS
Toxicity Table 2; 4/27/2010)
CHEMICAL NAME
p-Dimethylaminoazobenzene
3,3'-Dimethylbenzidine
Dimethyl carbamoyl chloride
Dimethyl formamide
Dimethyl phthalate
Dimethyl sulfate
N,N-dimethylaniline
1,1-Dimethylhydrazine
4,6-Dinitro-o-cresol
2,4-dinitrophenol
2,4-Dinitrotoluene
2,4/2,6-Dinitrotoluene (mixture)
1,4-Dioxane
1 ,2-Diphenylhydrazine
Epichlorohydrin
1,2-Epoxybutane
Ethyl acrylate
Ethyl benzene
Ethyl carbamate
Ethyl chloride
Ethylene dibromide
Ethylene dichloride
Ethylene glycol
Ethylene imine (Aziridine)
Ethylene oxide
Ethylene thiourea
Ethylidene dichloride (1,1-
Dichloroethane)
Formaldehyde
Diethylene glycol monobutyl
ether
uietnyiene glycol monoetnyl
ether
Ethylene glycol ethyl ether
Ethylene glycol ethyl ether
acetate
CAS NO.
60-11-7
119-93-7
79-44-7
68-12-2
131-11-3
77-78-1
121-69-7
57-14-7
534-52-1
51-28-5
121-14-2
25321-14-6
123-91-1
122-66-7
106-89-8
106-88-7
140-88-5
100-41-4
51-79-6
75-00-3
106-93-4
107-06-2
107-21-1
151-56-4
75-21-8
96-45-7
75-34-3
50-00-0
112-34-5
111-90-0
110-80-5
111-15-9
AEGL-1 (1-h)
mg/m3
0.12'
61 '
22 '
210 P
34'
140 p
130'
1.1 f
AEGL-1 (8-h)
mg/m3
i
0.045 '
f
61 '
22 '
210 P
34'
140 p
35'
I
I
1.1 f
AEGL-2(1-h)
mg/m3
270 '
0.62'
7.4 f
1200'
91 !
410 P
150'
4800 P
180'
8.1 '
81 '
17 f
AEGL-2(8-h)
mg/m3
110 '
0.22'
0.93 f
360'
38 '
410 P
38'
2500 P
50'
0.83'
14 '
17 f
BRPG-1
mg/m3
6
22
34
200
1.1
ERPG-2
mg/m3
270
91
150
810
81
17
MRL
mg/m3
7.2
43
40
2
0.049
KB-
iTi g/m 3
3
1.3
0.055
0.37
0.14
IDLH/10
in g/m 3
150
200
3.6
50
3.7
0.5
5
180
28
120
350
1000
77
20
140
1200
2.5
180
TEBL-0
mg/m3
15
0.1
0.88
3
0.2
10
500
3.5
100
140
TEEL-1
mg/m3
50
0.3
2.6
7.5
0.6
30
500
10
150
410
40
version 2
-------
Acute Dose-Response Values for Screening
Risk Assessments (Based on OAQPS
Toxicity Table 2; 4/27/2010)
CHEMICAL NAME
Ethylene glycol methyl ether
acetate
Heptachlor
Hexachloro benzene
Hexachlorobutadiene
Hexachlorocyclopentadiene
Hexachlorodibenzo-p-dioxin,
mixture
Hexachloroethane
Hexamethylene-1 ,6-diisocyanate
Hexamethylphosphoramide
n-Hexane
Hydrazine
Hydrofluoric acid
Hydrogen sulfide
Hydroquinone
Isophorone
Lead acetate
Lead chloride
Lead compounds
Lead nitrate
Lead subacetate
Tetraethyl lead
Tetramethyl lead
Lindane (gamma-HCH)
alpha-Hexachlorocyclohexane (a-
HCH)
beta-Hexachlorocyclohexane (b-
HCH)
technical
Hexachlorocyclohexane (HCH)
Maleic anhydride
Manganese chloride
CAS NO.
110-49-6
76-44-8
118-74-1
87-68-3
77-47-4
19408-74-3
67-72-1
822-06-0
680-31-9
110-54-3
302-01-2
7664-39-3
7783-06-4
123-31-9
78-59-1
301-04-2
7758-95-4
7439-92-1
10099-74-8
1335-32-6
78-00-2
75-74-1
58-89-9
319-84-6
319-85-7
608-73-1
108-31-6
7773-01-5
AEGL-1 (1-h)
mg/m3
0.13 <
0.82 f
0.71 '
AEGL-1 (8-h)
mg/m3
1
0.13 <
0.82 f
0.46 '
AEGL-2(1-h)
mg/m3
12000 '
17 <
20 f
38 '
AEGL-2(8-h)
mg/m3
12000 '
2.1 <
9.8 f
24 !
ERPG-1
mg/m3
11
0.13
0.82
0.71
0.8
ERPG-2
mg/m3
32
17
20
38
8
M ra-
in g/m 3
58
0.016
0.098
REL
mg/m3
0.24
0.042
IDLH/10
mg/m3
3.5
390
6.5
2.5
5
10
4
4
5
1
TEEL-0
mg/m3
0.002
0.11
0.005
0.034
0.29
28
0.075
0.06
0.075
0.06
0.5
0.5
0.15
0.4
TEEL-1
mg/m3
0.006
0.2
0.015
0.1
0.92
28
0.2
0.2
0.22
0.2
1.5
1.5
0.5
6
41
version 2
-------
Acute Dose-Response Values for Screening
Risk Assessments (Based on OAQPS
Toxicity Table 2; 4/27/2010)
CHEMICAL NAME
Manganese dioxide
Manganese oxide
Manganese sulfate
methylcyclopentadienyl
Mercuric acetate
Mercuric chloride
Mercuric nitrate
Mercuric oxide
Mercury (elemental)
Methylmercuric dicyanamide
Mercury compounds
Methoxyethylmercuric acetate
Methyl mercury
Phenylmercuric acetate
Methanol
Methoxychlor
Methyl bromide
Methyl chloride
Methyl chloroform (1,1,1-
Trichloroethane)
Methyl hydrazine
Methyl iodide
Methyl isobutyl ketone
Methyl isocyanate
Methyl methacrylate
Methyl tert -butyl ether
4,4'-Methylene bis(2-
chloroaniline)
Methylene chloride
Methylene diphenyl diisocyanate
4,4'-Methylenedianiline
Naphthalene
Nickel acetate
Nickel carbonyl
CAS NO.
1313-13-9
1317-35-7
7785-87-7
12108-13-3
1600-27-7
7487-94-7
10045-94-0
21908-53-2
7439-97-6
502-39-6
HG CMPDS
151-38-2
22967-92-6
62-38-4
67-56-1
72-43-5
74-83-9
74-87-3
71-55-6
60-34-4
74-88-4
108-10-1
624-83-9
80-62-6
1634-04-4
101-14-4
75-09-2
101-68-8
101-77-9
91-20-3
373-02-4
13463-39-3
AEGL-1 (1-h)
mg/m3
690'
1300'
70'
180'
690'
AEGL-1 (8-h)
mg/m3
P
350 '
i
i
1300 '
f
f
70 <
180'
i
r
AEGL-2(1-h)
mg/m3
1.7p
2700'
820'
1900'
3300'
3.2 f
0.16 f
490'
2100 '
1900'
0.25 f
AE3L-2 (8-h)
mg/m3
0.33 p
680'
260'
780'
1700'
0.39 f
0.019f
200'
1400 '
210'
0.031 f
ERPG-1
mg/m3
690
1300
150
0.058
690
0.2
ERPG-2
mg/m3
2
2700
820
1900
3300
290
0.16
1900
2
M ra-
in g/m 3
0.19
1
11
7.2
2.1
REL
mg/m3
6E-04
28
3.9
68
14
IDLH/10
mg/m3
1
0.2
790
500
97
410
380
7.2
58
0.7
410
800
7.5
130
1.4
TEEL-0
mg/m3
0.3
0.25
0.5
0.6
0.01
0.035
0.04
0.025
0.015
0.015
0.1
310
0.11
0.081
TEEL-1
mg/m3
4
0.75
7.5
0.6
0.03
0.12
0.15
0.1
0.04
0.05
0.1
310
0.33
0.81
42
version 2
-------
Acute Dose-Response Values for Screening
Risk Assessments (Based on OAQPS
Toxicity Table 2; 4/27/2010)
CHEMICAL NAME
Nickel compounds
Nickel nitrate
Nickel oxide
Nickel refinery dust
Nickel subsulfide
Nickel sulfate
Nitrobenzene
4-Nitrobiphenyl
4-Nitrophenol
2-Nitropropane
Nitrosodimethylamine
N-Nitrosomorpholine
N-Nitroso-N-methylurea
Parathion
Polychlorinated biphenyls
Aroclor 1016
Aroclor 1221
Aroclor 1242
Aroclor 1248
Aroclor 1254
Aroclor 1260
Pentachloronitro benzene
Pentachlorophenol
Phenol
p-Phenylenediamine
Phosgene
Phosphine
Phosphorus, white
Phthalic anhydride
Acenaphthene
Anthracene
Benzo(a)anthracene
Benzo(b)fluoranthene
Benzo(k)fluoranthene
Benzo(g,h,i)perylene
Benzo(a)pyrene
Carbazole
beta-Chloronaphthalene
CAS NO.
7440-02-0
13138-45-9
1313-99-1
NI_DUST
12035-72-2
7786-81-4
98-95-3
92-93-3
100-02-7
79-46-9
62-75-9
59-89-2
684-93-5
56-38-2
1336-36-3
12674-11-2
11104-28-2
53469-21-9
12672-29-6
11097-69-1
11096-82-5
82-68-8
87-86-5
108-95-2
106-50-3
75-44-5
7803-51-2
7723-14-0
85-44-9
83-32-9
120-12-7
56-55-3
205-99-2
207-08-9
191-24-2
50-32-8
86-74-8
91-58-7
AEGL-1 (1-h)
mg/m3
58 '
AEGL-1 (8-h)
mg/m3
p
24'
f
f
AEGL-2 (1-h)
mg/m3
1.5 p
89 f
1.2 f
2.8 '
AEGL-2 (8-h)
mg/m3
0.48 "
46'
0.16 f
0.35 '
ERPG-1
mg/m3
58
ERPG-2
mg/m3
89
1.2
2.8
M ra-
ni g/m 3
0.02
PEL
mg/m3
0.006
5.8
0.004
IDLH/10
mg/m3
1
100
36
1
0.25
96
0.81
6
TEEL-0
mg/m3
3
0.75
2.5
0.25
0.75
3.5
12
0.015
1
0.2
0.2
1
0.2
0.5
0.3
0.5
0.1
0.4
2
0.1
0.2
0.2
10
0.2
0.75
0.2
TEEL-1
mg/m3
3
0.75
2.5
0.75
2.5
10
30
0.05
3
0.6
0.6
3
0.6
1.5
0.75
1.5
0.3
1.2
6
0.3
0.6
0.6
30
0.6
2.5
0.6
43
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Acute Dose-Response Values for Screening
Risk Assessments (Based on OAQPS
Toxicity Table 2; 4/27/2010)
CHEMICAL NAME
Dibenz(a,h)anthracene
Dibenzo[a,e]pyrene
Fluoranthene
Fluorene
lndeno(1 ,2,3-cd)pyrene
3-Methylcholanthrene
1 -Methylnaphthalene
2-Methylnaphthalene
2-Naphthylamine
1-Nitropyrene
Phenanthrene
Pyrene
1,3-Propane sultone
beta-Propiolactone
Propionaldehyde
Propoxur
Propylene dichloride
Propylene oxide
1 ,2-Propyleneimine
Quinoline
Quinone
Selenium compounds
Hydrogen selenide
Potassium selenate
Selenious acid
Selenium dioxide
Selenium disulfide
Selenium oxychloride
Selenium sulfide
Sodium selenate
Sodium selenite
Styrene
Styrene oxide
2,3,7,8-Tetrachlorodibenzo-p-
dioxin
1 , 1 ,2,2-Tetrachloroethane
Tetrachloroethene
Titanium tetrachloride
Toluene
CAS NO.
53-70-3
192-65-4
206-44-0
86-73-7
193-39-5
56-49-5
90-12-0
91-57-6
91-59-8
5522-43-0
85-01-8
129-00-0
1120-71-4
57-57-8
123-38-6
114-26-1
78-87-5
75-56-9
75-55-8
91-22-5
106-51-4
7782-49-2
7783-07-5
7790-59-2
7783-00-8
7446-08-4
7488-56-4
7791-23-3
7446-34-6
13410-01-0
10102-18-8
100-42-5
96-09-3
1746-01-6
79-34-5
127-18-4
7550-45-0
108-88-3
AEGL-1 (1-h)
mg/m3
110'
170'
85 ''
240 '
0.54 !
750 !
AEGL-1 (8-h)
mg/m3
110 '
170 '
i
i
85 !
240 '
0.54 ''
750 !
AEGL-2 (1-h)
mg/m3
620'
690'
28 ''
2.4 ''
550 ''
1600 '
7.8 !
4500 !
AEGL-2 (8-h)
mg/m3
260 '
200 '
2.8 ''
0.86 ''
550 ''
550 '
0.73 ''
2400 !
ERPG-1
mg/m3
170
85
240
5.1
750
ERPG-2
mg/m3
690
2.4
550
1600
7.8
1900
MRL
mg/m3
0.23
8.5
1.4
3.8
PEL
mg/m3
3.1
0.005
21
20
37
IDLH/10
mg/m3
180
95
10
0.1
0.33
300
69
100
190
TEEL-0
mg/m3
10
0.035
0.005
7.5
0.15
0.2
6
6
2.5
0.1
0.4
15
0.4
1.5
0.5
1.1
0.5
0.3
0.25
0.35
0.4
0.25
0.5
0.4
20
0.0006
TEEL-1
mg/m3
30
0.1
0.015
25
0.5
0.6
20
20
7.5
0.3
1
15
1.2
1.5
1.5
3.2
1.5
1
0.75
1
1.2
0.75
1.5
1.2
61
0.0015
44
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Acute Dose-Response Values for Screening
Risk Assessments (Based on OAQPS
Toxicity Table 2; 4/27/2010)
CHEMICAL NAME
2,4/2,6-Toluene diisocyanate
mixture (TDI)
2,4-Toluene diisocyanate
o-Toluidine
Toxaphene
1 ,2,4-Trichlorobenzene
1 ,1 ,2-Trichloroethane
Trichloroethylene
2,4,5-Trichlorophenol
2,4,6-Trichlorophenol
Triethylamine
Trifluralin
2,2,4-trimethylpentane
Uranium compounds
Uranium (IV) dioxide
Uranium hexafluoride
Uranium oxide
Uranium, soluble salts
Uranyl acetate dihydrate
Uranyl nitrate hexahydrate
Vinyl acetate
Vinyl bromide
Vinyl chloride
Vinylidene chloride
m-Xylene
o-Xylene
p-Xylene
Xylenes (mixed)
Xylenes (mixed)
CAS NO.
26471-62-5
584-84-9
95-53-4
8001-35-2
120-82-1
79-00-5
79-01-6
95-95-4
88-06-2
121-44-8
1582-09-8
540-84-1
7440-61-1
1344-57-6
7783-81-5
1344-59-8
URANSOLS
541-09-3
13520-83-7
108-05-4
593-60-2
75-01-4
75-35-4
108-38-3
95-47-6
106-42-3
1330-20-7
1330-20-7
AEGL-1 (1-h)
mg/m3
0.14 f
700 <
3.6 f
24'
640 !
560'
560 <
AEGL-1 (8-h)
mg/m3
0.071 f
410 <
f
24'
180 !
560'
560 <
AEGL-2(1-h)
mg/m3
0.59 f
2400 <
9.6 f
630'
3100 !
4000'
4000 <
AEGL-2 (8-h)
mg/m3
0.15 f
1300 <
1.2'
260'
21001
1700'
1700 <
ERPG-1
mg/m3
0.14
700
3.6
18
640
ERPG-2
mg/m3
1.1
2400
30
9.6
10
260
3100
M ra-
in g/m 3
11
1.3
8.7
8.7
RB.
mg/m3
2.8
180
22
22
22
22
IDLH/10
mg/m3
1.8
22
55
1
390
390
390
390
390
TEH.-0
mg/m3
1.8
0.5
37
10
10
0.025
350
0.05
0.075
0.1
22
20
TEEL-1
mg/m3
5.3
1
37
30
30
0.075
350
0.6
1
1.2
66
79
45
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APPENDIX C
SUGGESTED SCREENING REPORT OUTLINE
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47 version 2
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The following is a suggested report outline for a risk-based air toxics screening level analysis.
Analysts should feel free to modify this as necessary to meet the specific circumstances of their
analysis. However, analysts are encouraged to keep in mind that the types of information
highlighted in this outline are the minimum elements usually considered necessary to document
any basic air toxics risk-based screening level analysis.
Title Page
Authors, disclaimers, preface, etc.
1. Executive Summary
2. [Corresponding to Step 1] Background discussion (what is being done in the analysis, why is
it being done, description of monitoring data to be evaluated, including maps showing location
of monitors and nearby populations, sources, etc.)
3. [Corresponding to Step 2] Assessment of data quality
4. [Corresponding to Step 3] Statistical summaries, by monitor, of detected chemicals
5. [Corresponding to Step 4] Comparison of detected values to chronic/acute screening values;
identification of chemicals failing the screen
6. [Corresponding to Step 5] Collection and description of relevant ancillary data
7. [Corresponding to Step 6] Analysis and description of uncertainties
8. [Corresponding to Step 7] Conclusions
9. References
10. Appendices, as needed
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APPENDIX D
ABBREVIATED SCREENING EXAMPLE
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Abbreviated Screening Example
Note to reader - this example is not exhaustive in its explanation of how a full screening level
analysis should be performed and documented. Rather, it provides enough information to
illustrate for the reader the general logic behind a screening level analysis, including how to
fill in the various data tables.
1. Background
After several years of intermittent
complaints from the Hawkeye Downs
neighborhood of Ag County, a coalition of
county government, private community
organizations, and local industry
representatives has been formed to
investigate health risks from air pollution.
Specifically, residents of Hawkeye Downs
are concerned that a number of people in the
neighborhood may be sick because of the
emissions from four industrial sources in the
immediate vicinity of Hawkeye Downs.
Complaints include respiratory irritation and
cough. Cancer incidence in the county is
above the state and national average.
The Ag County Air Pollution Control
Agency (ACAPCA) began collecting air
toxics monitoring samples earlier this year at
a monitoring site within Hawkeye Downs
(see map, next page). The same air toxics
are also monitored by ACAPCA at an Army
Reserve site which is located in a rural area
far from any industrial or large mobile
sources. Meteorological data which are
representative of the county are also
collected at the Army Reserve monitor
location. At both monitoring sites, volatile
organic compound (VOC) and carbonyl
samples are collected as 24-hour composite
samples on the same l-in-6 day sampling
schedule. The sampling commenced in
January 2004, with the most recent samples
collected in early July 2004. A total of 30
samples has been collected during this period
at each of the monitoring sites. ACAPCA's
lab performs the analytical evaluation of the
samples, validates the results, and reports the
data to EPA. The lab has provided the first
six months of validated data to a subgroup
(the "risk assessment team") of the larger
community stakeholder group.
The community stakeholder group's ultimate
goal is to perform a risk assessment using
one full year's worth of monitoring data
(once it is available). In the meantime, the
risk assessment team would like to perform a
preliminary screen of the currently available
6-month's worth of monitoring data to
develop & preliminary picture of the
potential for exposure of the Hawkeye
Downs community to air toxics
concentrations of concern, according to the
procedures described in this screening-level
methodology.
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52
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Population Density for Ag County, USA
(US Census-2000)
( ) Monitoring site
A Facilities
•^j- Weather station/Toxics monitoring site
y\/County line
Roads
A/U.S. Interstate Highways
/\/ State Highways
/\/ City/County Roads
Population per square mile
0-2000
2001 - 5300
5301 - 11000
11001 -37000
| | Over 37000
| | Census tract boundaries
4 Miles
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53
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Note that, at a minimum, one full year's
worth of monitoring data is commonly
considered necessary to evaluate chronic
exposures. In this example, the stakeholders
are planning to collect and evaluate one full
year's worth of data using the risk
assessment procedures outlined in ATRA,
Volume 1, Part II; however, while the data
collection process is occurring, they have
decided to go ahead and screen the first 6-
months of data to help identify any potential
risk drivers as early in the process as
possible. They might find, for example, that
a chemical of known origin frequently
exceeds both an acute and chronic level
during the first 6-months of the monitoring
study and that this is sufficient justification
for the risk managers to act. Conversely, if
the first 6-months of data show infrequent
detections that are near or below the chronic
screening levels, the partial data set may
provide no strong basis for action (i.e.,
decision making would need to wait until the
completion of the full-year monitoring
study). Ultimately, analysts may chose to
perform exploratory analyses using only a
partial data set; however, they must be
careful to both understand and communicate
the associated limitations to the end users.
STEP 1: Identify the monitoring data sets
to be screened and the geographic areas
and time frames that the monitoring data
in question represent.
The geographic areas to be evaluated in this
screening level analysis consist of two
neighborhoods separated by approximately 4
miles. One monitor (the Hawkeye Downs
monitor) was established to be a
neighborhood-scale monitor. The other
monitor (the Army Reserve monitor) is in
the same airshed as the Hawkeye Downs
Monitor and was also established as a
neighborhood-scale monitor. Meteorological
data collected at the Army Reserve monitor
is considered to be representative of the
larger geographic region, including the
Hawkeye Downs neighborhood.
The risk assessment team, after reviewing
the purpose and placement of the monitors,
as well as the locations of known air toxics
emissions sources and meteorological
information, has decided to do the following
with regard to Step 1:
• Include both monitoring locations in the
screening level assessment since they are
within the same airshed and are in
reasonably close proximity to one
another.
• The meteorological data collected at the
Army Reserve site will be used to
evaluate meteorological conditions at
both sites.
• Keep the analytical data sets developed at
the two monitoring sites separate since
the two monitors likely represent two
distinct exposure scenarios. (Combining
data that represent different exposure
scenarios would obscure the overall
analysis.)
Ultimately, the team believes that evaluating
and communication information from both
sites as part of one screening level analysis
will provide clues to the nature and impact of
air toxics emissions sources in the
geographic area as a whole.
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54
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STEP 2: Assess the data to determine if
they are of sufficient quantity and quality
to perform the screen.
The data needs for this monitoring study
were established by a rigorous systematic
planning process that identified the purpose
of the monitoring study, the questions the
study will attempt to answer, and the
quantity and quality of data needed to
answer those questions within limits
acceptable to the decision makers. Based on
the specific data quality needs for the
assessment, a Quality Assurance Project Plan
(QAPP) was developed that establishes the
details of sample collection, transport,
analysis, data validation, and data reporting.
The QAPP also describes an established
QA/QC program for the project,
documentation requirements, and roles and
responsibilities of the people performing the
work. For the first 6 months of data
collection, the samples have been collected,
analyzed, validated, and reported in general
accordance with the QAPP. The risk
assessment team noted the following
exceptions:
• At the Hawkeye Downs monitor, one of
the 30 VOC samples was not collected
due to an instrument malfunction.
• At the Army Reserve monitor, two of the
30 VOC samples were invalidated during
the data validation process due to
laboratory contamination.
The QAPP states that a valid sample
collection rate of 90% is sufficient to
perform the risk assessment on a full year's
worth of data. As such, the risk assessment
workgroup judges the 6-month monitoring
data set to be of acceptable quantity and
quality for performing the risk-based
screening level analysis (the sampling effort
is on track to meet the goals of the QAPP,
including a 90% valid sample collection
rate).
STEP 3: For each chemical detected at
least once in the data set, create a
statistical summary of the monitoring
results for that chemical. The statistical
summary will commonly include the
following: Number of valid samples
collected and frequency of detection, the
method detection limits (MDLs), and
range of detected values.
In the Ag County study, only 4 chemicals
were detected at the Hawkeye Downs
monitor. The 4 chemicals are acetaldehyde,
methylene chloride, benzene, and vinyl
chloride. Three of these same 4 chemicals
were also the only chemicals to be detected
at the Army Reserve monitoring site. (Vinyl
chloride was not detected at the Army
Reserve site.)
The risk assessment workgroup reviewed the
validated analytical data for the samples
collected at the Hawkeye Downs monitor (30
carbonyl and 29 VOC samples) and at the
Army Reserve monitor (30 carbonyl and 28
VOC samples) and developed the following
statistical summaries for the two monitoring
sites:
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55
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Statistical Summary of Detected Chemicals
Hawkeye Downs Monitoring Site
Detected Chemical
(CAS Number)
Acetaldehyde
(75-07-0)
Methylene Chloride
(75-09-2)
Benzene
(71-43-2)
Vinyl Chloride
(75-01-4)
Frequency of
Detection
15/30
25/29
29/29
20/29
Laboratory-Specific
Method Detection Limit
(ug/m3)
0.016
0.045
0.014
0.024
Range of Detected Values
(ug/m3)
0.04J-0.35
0.9-4.5
0.2-2.2
0.03J-0.08
Statistical Summary of Detected Chemicals
Army Reserve Monitoring Site
Detected Chemical
(CAS Number)
Acetaldehyde
(75-07-0)
Methylene Chloride
(75-09-2)
Benzene
(71-43-2)
Frequency of
Detection
4/30
2/28
19/28
Laboratory-Specific
Method Detection Limit
(ug/m3)
0.016
0.045
0.014
Range of Detected
Values
(ug/m3)
0.02J - 0.09
O.U-0.7
0.05 - 1.2
Note that acetaldehyde and methylene dichloride were infrequently detected at the Army Reserve
monitoring site. From the lab reports, it is also noted that several detected concentrations at both
monitoring sites were below sample quantitation limits and flagged as J values.
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56
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STEP 4: For each detected chemical in
the data set, compare the maximum
monitored value to the suggested chronic
screening level value provided in
Appendix A and the acute values provided
in Appendix B. Summarize the results of
the comparison process in a table.
Highlight chemicals whose maximum
monitored values exceed their respective
screening values (chronic and acute). For
each chemical whose maximum monitored
value exceeds a screening value, review
the full data set and determine the
percentage of detections that are at or
above the screening value.
For the Hawkeye Downs monitoring site, the
risk assessment workgroup identified the
maximum value found for each chemical
detected from the statistical summary of the
data provided in Step 3 as well as the chronic
and acute screening values for each chemical
from Appendices A and B. They then
compared the maximum value found to the
chronic and acute screening values and
presented the results in a table (see below).
[Note that the group decided to use the
suggested screening levels provided in
Appendices A and B; however, they could
have chosen both different toxicity values
and screening risk levels (e.g., a chronic
noncancer screening level other than an HQ
= 0.1). In either event, risk assessment
teams are encouraged to document their
rationale for the selection of both toxicity
values and risk screening levels.] From this
table, the toxicologist on the stakeholder
team drew the following conclusions:
• Acetaldehyde. The maximum
concentration of acetaldehyde is below
the final chronic screening value from
Appendix A, indicating no apparent
concern for chronic exposure for this
chemical. Since the maximum value
found for this chemical is below its
chronic screening value, an acute analysis
was not performed. (Since chronic values
are usually not greater than acute values
and the maximum measurement is below
the chronic screening value, it is assumed
that acute exposures are not a concern.)
Therefore, the acute column is marked
"N/A" or "not applicable".
Vinyl Chloride. The maximum
concentration of vinyl chloride is below
the final chronic screening value from
Appendix A, indicating no apparent
concern for chronic exposure for this
chemical. Since the maximum value
found for this chemical is below its
chronic screening value, an acute analysis
was not performed. Therefore, the acute
column is marked "N/A" or "not
applicable".
Methylene Chloride. The maximum
concentration of methylene chloride is
above its chronic screening value. Only
some of the methylene chloride detections
at the monitor are above the chronic
screening value while others are below.
An evaluation of the 25 methylene
chloride detections at the Hawkeye
Downs monitor shows that 10 of the
samples are below the chronic screening
value and 15 are above. The frequency of
monitored values exceeding the chronic
screening value is, therefore: [(15 ^ 25) x
100 = 60%]. Depending on the amount
by which the measurements exceed the
chronic value and the magnitude of the
measurements that are lower than the
screening value, this may be indicative of
a potential chronic concern for this
chemical.
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57
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Summary of Screening Analysis for Detected Chemicals
Hawkeye Downs Monitor
Detected
Chemical
(CAS
Number)
Acetaldehyde
(75-07-0)
Methylene
Chloride
(75-09-2)
Benzene
(71-43-2)
Vinyl
Chloride
(75-01-4)
Maximum
Concentration
detected
(ug/m3)
0.35
4.5
2.2
0.08
Final
Chronic
Screening
Value from
Appendix A
(ug/m3)
0.45
2.1
0.13
0.11
Acute
Screening
Value
from
Appendix
B (ug/m3)
N/A
Various
(See
discussion
below)
Various
(See
discussion
below)
N/A
Maximum
Concentration is >
Chronic Screening
Value (Yes/No)?
(% Detections
Exceeding)1
NO
YES
(60% of detections
exceed the chronic
screening value)
YES
(100% of detections
exceed the chronic
screening value)
NO
Maximum
Concentration is>
Acute Screening
Value (Yes/No)?
(% Detections
Exceeding)1
N/A
NO
(See discussion
below)
NO
(See discussion
below)
N/A
1. If the maximum value found exceeds screening value (chronic or acute), the full data set of valid samples for the
chemical was reviewed to determine the percentage of detections that, individually, are at or above the screening
value. The % Detections Exceeding is equal to the number of detections at or above the screening value divided by
the total number of detections multiplied by 100.
With regard to the potential for acute
exposures to this compound, the team
reviewed the acute screening values for
this chemical in Appendix B and found
five values (EPRG-1 and ERPG-2 values,
an acute MRL, an acute REL, and an
IDLH/10). The team's toxicologist noted
that the 24-hour sampling time for the
monitor falls within the acute MRL
duration (24 hours to two weeks) and that
acute MRLs were developed to evaluate
exposures to the general public (see
http://www.atsdr.cdc.gov/mrls.html). The
toxicologist recommends, after
consideration of the characteristics of the
other acute toxicity values, such as their
purpose, duration, and health endpoints,
that evaluation of acute exposures should
be performed using only the acute MRL.
Since the maximum value found for
methylene chloride (4.5 ug/m3) is almost
two orders of magnitude smaller than the
acute MRL for this compound (2,100
ug/m3), the team concludes that acute
exposures do not appear to be an issue.
• Benzene. Benzene's maximum
concentration also exceeded its chronic
screening value. Since benzene was
detected in all samples (frequency of
detection = 29/29) and since the range of
detected values exceeds the chronic
screening value, it can be concluded that
100% of the detections are above the
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chronic screening value [percentage of
samples above the chronic screening
value = (29 -29) x 100 = 100%].
With regard to the potential for acute
exposures, the team reviewed the acute
screening values for this chemical in
Appendix B and found that there are
many available acute values. The team's
toxicologist noted that the 24-hour
sampling time for the monitor falls within
the acute MRL duration (24 hours to two
weeks) and that acute MRLs were
developed to evaluate exposures to the
general public (see
http://www.atsdr.cdc.gov/mrls.html). The
toxicologist recommends, after
consideration of the characteristics of the
other acute toxicity values, such as their
purpose, duration, and health endpoints,
that evaluation of acute exposures should
be performed using only the acute MRL.
Since the maximum value found for
benzene (2.2 ug/m3) is almost two orders
of magnitude lower than the acute MRL
for this compound (160 ug/m3), the team
concludes that there appears to be no
evidence of acute exposures of concern
for this chemical.
The chemicals failing the screen at the
Hawkeye Down monitoring site are,
therefore, benzene and methylene chloride
for chronic concerns.
The risk assessment workgroup prepared a
similar table for the Army Reserve
monitoring site (see below).
The Army Reserve monitoring results for
acetaldehyde and methylene chloride are
below their chronic screening values and no
acute exposure evaluation was performed.
The maximum concentration for benzene is
above the chronic screening level but not
above the acute MRL. Only some of the
benzene detections at the Army Reserve are
above the chronic screening value while
others are below. An evaluation of the 19
benzene detections at the Army Reserve
monitor shows that 10 of the samples are
below the chronic screening value and 9 are
above. The frequency of exceedance of the
chronic screening value is, therefore: [(9 -
19) x 100 = 47%].
The chemical failing the screen at the Army
Reserve monitoring site is, therefore,
benzene for chronic concerns.
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59
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Summary of Screening Analysis for Detected Chemicals
Army Reserve Monitor
Detected
Chemical
(CAS Number)
Acetaldehyde
(75-07-0)
Methylene
Chloride
(75-09-2)
Benzene
(71-43-2)
Maximum
Concentration
detected
(ug/m3)
0.09
0.7
1.2
Final
Chronic
Screening
Value from
Appendix A
(ug/m3)
0.45
2.1
0.13
Acute
Screening
Value from
Appendix B
(ug/m3)
N/A
N/A
Various
(See
discussion for
the Hawkeye
Downs
monitor)
Maximum
Concentration
is > Chronic
Screening
Value
(Yes/No)?
(% Detections
Exceeding)1
NO
NO
YES
(47% of
detections
exceed the
chronic
screening
value)
Maximum
Concentration is
> Acute
Screening Value
(Yes/No)?
(% Detections
Exceeding)1
N/A
N/A
NO
(See discussion
for the Hawkeye
Downs monitor)
1. If the maximum value found exceeds screening value (chronic or acute), the full data set of valid samples for the
chemical was reviewed to determine the percentage of detections that, individually, are at or above the screening
value. The % Detections Exceeding is equal to the number of detections at or above the screening value divided by
the total number of detections multiplied by 100.
STEP 5: Augment the results described in
Step 4 with ancillary information about
chemicals that fail the screen (e.g.,
possible sources, applicable regulations,
estimated background concentrations,
NATA national scale assessment results
for the geographic area, etc.).
This section of the analysis would focus on
only two chemicals - benzene and methylene
chloride (the two chemicals that fail the
screen). The risk assessment team would
develop information about the likely sources
of air emissions of these two chemicals, the
location of the sources, and the regulatory
status of the sources. They would also
gather information about estimated
concentrations/risks from the NATA national
scale assessment for comparison, the
locations and characteristics of local
populations in the area (noting especially
sensitive subpopulations and environmental
justice areas), and the possibility of upwind
sources outside the study area. Information
on citizen complaints and any medical,
epidemiological, or modeling studies would
also be important to note.
STEP 6: Describe areas of uncertainty in
the analysis.
The risk assessment workgroup is careful to
identify and describe the important areas of
uncertainty in their risk screening analysis.
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Some of the various questions they have
decided to cover in their uncertainty
evaluation include the following:
• Do the monitors provide a representative
estimate of exposure across the
neighborhoods which they are meant to
represent?
• Are there important chemicals possibly
present in air that were not sampled?
• The samples only cover 6 months of the
year and do not take into account seasonal
variation in meteorology or changing
source characteristics over time. How
might this impact the way in which the
screening results should be viewed?
• Are there chemicals released from nearby
sources which have the potential to
partition to other media and present
significant exposures through pathways
other than inhalation (e.g., dioxin,
mercury)?
• What are the uncertainties associated with
the underlying toxicological database of
the selected screening levels?
• Is there a potential for additive acute
effects (see ATRA Volume 1, Section
13.2.2.3)?
STEP 7: Eased on the screening results
provided in Step 4, the ancillary data
developed in Step 5, and the uncertainty
analysis developed in Step 6, develop a
written description of the analysis,
including a discussion about the possibility
that a public health threat exists that
requires further analysis. Include in this
discussion an overall statement of the
confidence in the results.
The risk assessment team collects all the
information it has developed together and
sits down to write its screening assessment
report. It decides to use the suggested
outline provided in Appendix C of this
screening level methodology. The group is
careful to provide only factual information
and not to make any judgements about risk
mitigation actions that should be taken to
respond to the screening level analysis (that
is the realm of the risk manager). However,
they appropriately make conclusions about
the potential for exposures of public health
concern, the populations that may be
affected and, if possible, the sources
primarily responsible for the potential
exposures. They also make sure to clearly
and thoroughly provide important details
about the strengths, weakness, and other
details of the analysis and to provide
statements about their confidence in their
conclusions. For example, in discussing the
screening values for the detected chemicals,
the analyst would discuss issues such as the
carcinogenic weight of evidence for detected
compounds and uncertainty factors used in
the derivation of reference concentrations.
They should also make recommendations
about further analyses that should be done to
clarify or reduce uncertainties in the screen.
It is particularly important for the analyst to
clarify that chemicals that fail the screen
pose exposures of potential concern and that
more robust and thorough analysis will likely
be required to clarify the nature of the risk.
Ultimately, the risk assessment team makes
sure their report is thorough, logical, clear,
and transparent so that the risk managers and
any other stakeholder interested in following
their analysis can understand what they did,
how they did it, why they did it the way they
did, and what they concluded.
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References
1. U.S. EPA. 2004. Air Toxics Risk Assessment Reference Library, Volume 1, Technical
Resource Manual. Office of Air Quality Planning and Standards (EPA-453-K-04-001A).
April (http://www.epa.gov/ttn/fera/risk_atra_main.html).
2. OAQPS Toxicity Values Table - http://www.epa.gov/ttn/atw/toxsource/summary.html
(note that these values are updated from time to time and changes in the OAQPS toxicity
tables may not be reflected in the current version of this screening level methodology).
3. U.S. EPA. 1989a. National Emission Standards for Hazardous Air Pollutants; Benzene.
Federal Register 54(177):38044-38072, Rule and Proposed Rule. September 14.
4. EPA's Quality System for Environmental Data and Technology website -
http ://www. epa. gov/quality/
5. U.S. EPA. 1992. EPA 's Guidance for Data Useability in Risk Assessment, Part A.
Office of Emergency and Remedial Response (9285.7-09A). April.
http://www.epa. gov/oswer/riskassessment/superfund_misc.htm
6. The Lake Michigan Air Directors Consortium, in conjunction with EPA has, over the
past few years been evaluating the historical air toxics monitoring data set (as well as
newer data sets) to clarify how best to perform air toxics monitoring. Their reports,
which can be viewed at http://www.ladco.org/toxics.htmL have helped inform the
sampling protocols that have been established for EPA's new National Air Toxics Trends
Sites (NATTS) monitoring network.
7. National Emissions Inventory website - http://www.epa.gov/ttn/chief/eiinformation.html
8. Toxics Release Inventory website - http://www.epa.gov/tri/
9. National Air Toxics Assessment website - http://www.epa.gov/ttn/atw/nata/
10. Agency for Toxic Substances and Disease Registry website - http://www.atsdr.cdc.gov/
11. EPA's Risk Characterization Program website - http://epa.gov/osa/spc/htm/2riskchr.htm
12. USEPA 1987. Technical Guidance for Hazards Analysis, Emergency Planning for
Extremely Hazardous Substances. EPA-OSWER-99-0001. USEPA, FEMAUSDOT.
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