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
                                                        ^
EPA-904-B-06-001
www.epa.gov/region4/air/airtoxic/
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                                                         5>

October 2010                                         Cover Photo: Greg Noah/EPA
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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
                                  version 2

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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
                                  version 2

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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
                                             13
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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
                                 version 2

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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
                                             15
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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.
                                            16
                                 version 2

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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.
                                            17
                                 version 2

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                18                                   version 2

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APPENDIX A
CHRONIC SCREENING VALUES
                   19               version 2

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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
                         version 2

-------
       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.
                                           22
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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
23
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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
24
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)
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
version 2

-------
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
version 2

-------
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
version 2

-------
APPENDIX C
SUGGESTED SCREENING REPORT OUTLINE
                   46               version 2

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(This page intentionally left blank.)
                47                                   version 2

-------
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
                                           48                                    version 2

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(This page intentionally left blank.)
                49                                   version 2

-------
APPENDIX D
ABBREVIATED SCREENING EXAMPLE
                   50                version 2

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(This page intentionally left blank.)
                51                                   version 2

-------
                          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.
 For Demonstration Purposes Only
 Fictionalized Data
                                   version 1.2
52

-------
                    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
For Demonstration Purposes Only
Fictionalized Data
53
                                     version 1.2

-------
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.
 For Demonstration Purposes Only
 Fictionalized Data
                                    version 1.2
54

-------
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:
 For Demonstration Purposes Only
 Fictionalized Data
                                   version 1.2
55

-------
                       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.
 For Demonstration Purposes Only
 Fictionalized Data
                                   version 1.2
56

-------
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.
 For Demonstration Purposes Only
 Fictionalized Data
                                   version 1.2
57

-------
                  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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                  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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