United States         Science Advisory Board      EPA-SAB-EEC-97-012
      Environmental         Washington DC         September 1997
      Protection Agency



4>EPA AN SAB REPORT:  REVIEW



      OF THE SECTOR FACILITY



      INDEXING PROJECT (SFIP)
      PREPARED BY THE

      ENVIRONMENTAL ENGINEERING

      COMMITTEE (EEC)

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                              September 30, 1997

EPA-SAB-EEC-97-012

Honorable Carol M. Browner
Administrator
U.S. Environmental Protection Agency
401 M Street, SW
Washington, DC 20460

            Subject:     An SAB Review: Review of the Sector Facility Indexing
                        Project (SFIP)

Dear Ms. Browner:

      On April 29, 1997 a Subcommittee of the SAB's Environmental Engineering
Committee met to review the technical aspects of the Agency's Sector Facility Indexing
Project (SFIP). The SFIP incorporates the emissions data from the Toxics Release
Inventory (TRI) and couples them with toxicity weighting factors to obtain an index
which not only takes into account the reported quantities of the chemical but also takes
into account the chronic human health hazards associated with this chemical,  without
considering exposure.  The SAB was asked to examine the technical underpinnings of
the use of toxicity weighting factors in the SFIP.

      The Subcommittee applauds the Agency in its efforts to use existing data in
moving away from simple total mass releases  in the TRI data base to something that
makes more sense from a toxicological and risk point of view.  Clearly, using the
modified Hazard Ranking System (HRS) scoring methdology is a step in the right
direction. It is also apparent - to the SAB and to  the Agency - that the resulting
procedure falls short of generating estimates of actual risk, since it does not consider
ecological effects, acute effects, or anything about exposure.  And yet, for some
screening purposes, the procedure might be helpful in a limited way.  A scientific risk-
based approach would have to include consideration of these other factors as well.

      In short, the Subcommittee concluded that  by adopting  the SFIP, the Agency
was taking only the first step that would get to  actual risk. Members generally agreed
that it is important to use available scientific information to transform  the limited facility
release data into toxicity-weighted data in order to get closer to assessing the risks
involved.  Members disagreed on whether this transformation, by itself, was sufficient
progress  to establish a firm scientific basis for the use of the SFIP.

      The review of the SFIP was the first chance that the SAB has had to interact with
the Office of Enforcement and Compliance Assistance (OECA).  We accommodated

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their request by including it in an already tightly scheduled meeting.  As a result,
looking at the matter in retrospect, the Board did not have the opportunity to fully
explore the context and plans that the Agency has for using the SFIP.  Therefore, our
conclusions are somewhat more circumspect than they otherwise might have been, as
evidenced by these quotations from the report:

      a)    "The SFIP is a process that is getting to risk, but it is not there yet."

      b)    "Whether the SFIP is sufficiently useful for the limited purposes to which
            the Agency wants to put it...is a policy call that the Agency must make."

      We enjoyed the opportunity to review this project and to interact with a new
office. We are grateful to the OECA Staff for their preparation, presentation, and
patience in helping us  understand the project. It was reassuring to see that they were
fully aware of the related projects being conducted elsewhere in the Agency.

      We look forward to interacting with OECA again and look forward to the
response of the Assistant Administrator of the Office of Enforcement and Compliance
Assistance (OECA).

                               Sincerely,
                                    /signed/
                              Dr. Genevieve Matanoski, Chair
                              Science Advisory Board
                                    /signed/
                              Dr. Ishwar Murarka, Chair
                              Environmental Engineering Committee

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                                   NOTICE

      This report has been written as part of the activities of the Science Advisory
Board, a public advisory group providing extramural scientific information and advice to
the Administrator and other officials of the Environmental Protection Agency.  The
Board is structured to provide balanced, expert assessment of scientific matters related
to problems facing the Agency.  This  report has not been reviewed for approval by the
Agency and, hence, the contents of this report do not necessarily represent the views
and policies of the Environmental Protection Agency, nor of other agencies in the
Executive  Branch of the Federal government, nor does mention of trade names or
commercial products constitute  a recommendation for use.

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                                 ABSTRACT
      On April 29, 1997 a Subcommittee of the SAB's Environmental Engineering
Committee met to review the technical aspects of the Agency's Sector Facility Indexing
Project (SFIP). The SFIP incorporates the emissions data from the Toxics Release
Inventory (TRI) and couples them with toxicity weighting factors to obtain an index
which not only takes into account the reported quantities of the chemicals but also
takes into account the chronic human health hazards associated with these chemicals,
without considering exposure.  The SAB was asked to examine the technical
underpinnings of the use of toxicity weighting factors in the SFIP. The charge
consisted of two questions:

      a)    "...Does the modified Hazard Ranking System (MRS) scoring methodology
            used by the indicators reflect accepted scientific procedures and evidence
            regarding the relative ranking of chemical toxicity?"

      b)     "...is it acceptable to use toxicity weights to provide additional contextual
            information regarding the human health hazards associated with pollutant
            releases?

      The Subcommittee applauded the Agency's efforts to move beyond the total
mass emissions in an attempt to characterize facilities by using the modified Hazzrd
Ranking System scoring methodology.  They agreed that the SFIP is a process that is
"getting to risk," but it is not there yet.  Whether or not the SFIP is sufficiently useful for
the limited purposes to which the Agency wants to put it, in the light of the limitations
identified in Subcommittee's discussion, is a policy call that the Agency must make.

      A number of the members of the Subcommittee prepared written material to
capture their views. These extensive comments are included in an Appendix to this
report and are commended to the Agency:

      a)    As a demonstration of the breadth of views on these issues.

      b)    For their individual, not Subcommittee-endorsed, insights and
            suggestions for improving the current SFIP.
KEYWORDS:      Sector Facility Indexing Project, SFIP, Toxics Release Inventory,
                  TRI, weighting factors

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            U.S. ENVIRONMENTAL PROTECTION AGENCY
                        Science Advisory Board
             Environmental Engineering Committee (FY97)

CHAIR
Dr. Ishwar P. Murarka, Land & Groundwater Protection & Remediation, Environmental
      Group, Electric Power Research Institute, Palo Alto, CA

MEMBERS
Dr. Edgar Berkey, Center for Hazardous Materials Research, Pittsburgh, PA

Dr. Calvin C. Chien, Corporate Remediation, E. I. DuPont Company, Wilmington, DE

Dr. Nina Bergan French, SKY+, Oakland, CA

Dr. Hilary I. Inyang, Center for Environmental  Engineering and Science Technologies
      (CEEST), University of Massachusetts, Lowell, MA

Dr. James H. Johnson, Jr., School of Engineering, Howard University, Washington, DC

Dr. Jo Ann Lighty, College of Engineering, University of Utah, Salt Lake City, UT

Dr. John P. Maney, Environmental Measurements Assessment, Hamilton, MA

Dr. James W. Mercer, GeoTrans, Inc., Sterling, VA

Ms. Lynne M. Preslo, Technical Programs, Earth Tech, Long Beach, CA

Dr. Wm. Randall Seeker, Energy & Environmental Research Corp., Irvine, CA

Science Advisory Board Staff
Dr. Donald G. Barnes, Staff Director, Science Advisory Board (1400), U.S. EPA,
      Washington, DC  20460

Ms. Kathleen W. Conway, Designated Federal Official, Science Advisory Board (1400),
      U.S. EPA,  Washington, DC 20460

Mrs. Dorothy M. Clark, StaffSecretary, Science Advisory Board (1400), U .S. EPA,
      Washington, DC  20460

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                 U.S. Environmental Protection Agency
                        Science Advisory Board
                 Environmental Engineering Committee
                     Special Topics Subcommittee
      Use of Toxicity Weighting Factors in the OECA/SFIP Review
                              April 29, 1997

CHAIR
Dr. Ishwar P. Murarka, Land & Groundwater Protection & Remediation, Environmental
      Group, Electric Power Research Institute, Palo Alto, CA

MEMBERS
Dr. William J. Adams, Kennecott Utah Copper Corp., Magna, UT

Dr. Stephen L. Brown, R2C2 Risks of Radiation and Chemical Compounds, Oakland,
      CA

Dr. Linda E. Greer,  Natural Resources Defense Council, Washington, DC

Dr. Richard Kimerle, Monsanto Company (Retired), St. Louis, MO

Dr. John P. Maney,  Environmental Measurement Assessment, Hamilton, MA

Dr. Thomas E. Natan, Environmental Information Center, Washington, DC

Dr. Lauren Zeise, Reproductive and Cancer Hazard Assessment Section, California
      Environmental Protection Agency, Berkeley, CA

Science Advisory Board Staff
Dr. Donald G. Barnes, Staff Director, Science Advisory Board (1400), U.S. EPA,
      Washington,  DC 20460

Ms. Kathleen W. Conway, Designated Federal Official, Science Advisory Board (1400),
      U.S. EPA, Washington, DC 20460

Mrs. Dorothy M. Clark, Staff Secretary, Science Advisory Board (1400), U .S. EPA,
      Washington,  DC 20460
                                    IV

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                        TABLE OF CONTENTS
1.  EXECUTIVE SUMMARY	 1

2.  INTRODUCTION	 2
     2.1 Background 	 2
     2.2  Charge to the Science Advisory Board	 3
     2.3  Response to Specific Charge Elements	 3
           2.3.1  First Charge Element  	 3
           2.3.2 Second Charge Element	 4
     2.4  Overall Response to the Issue behind the Charge Questions  	 5
     2.5  Other Technical Comments  	 6

REFERENCES CITED	 R -1

APPENDIX A 	 A -1
APPENDIX B 	 B -1

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                         1.  EXECUTIVE SUMMARY
      On April 29, 1997 a Subcommittee of the SAB's Environmental Engineering
Committee met to review the technical aspects of the Agency's Sector Facility Indexing
Project (SFIP). The SFIP incorporates the emissions data from the Toxics Release
Inventory (TRI) and couples them with toxicity weighting factors to obtain an index
which not only takes into account the reported quantities of the chemicals but also
takes into account the chronic human health hazards associated with these chemicals,
without considering exposure.  The SAB was asked to examine the technical
underpinnings of the use of toxicity weighting factors in the SFIP. The charge
consisted of two questions:

      a)    "...Does the modified Hazard Ranking System (MRS) scoring methodology
            used by the indicators reflect accepted scientific procedures and evidence
            regarding the relative ranking of chemical toxicity?"

      b)     "...is it acceptable to use toxicity weights to provide additional contextual
            information regarding the human health hazards associated with pollutant
            releases?

      The Subcommittee applauded the Agency's efforts to move beyond the total
mass emissions in an attempt to characterize facilities by using the modified Hazzrd
Ranking System scoring methodology.  They agreed that the SFIP is a process that is
"getting to risk," but it is not there yet.  Whether or not the SFIP is sufficiently useful for
the limited purposes to which the Agency wants to put it, in the light of the limitations
identified in Subcommittee's discussion, is a policy call that the Agency must make.

      A number of the members of the Subcommittee prepared written material to
capture their views. These extensive comments are included in an Appendix to this
report and are commended to the Agency:

      a)    As a demonstration of the breadth of views on these issues.

      b)    For their individual, not Subcommittee-endorsed, insights and
            suggestions for improving the current SFIP.

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                             2.  INTRODUCTION
2.1  Background

      Many aspects of the Agency's activities center around risk and reduction of risks
to human health and the environment.  The so-called "risk assessment/risk
management (RA/RM)" paradigm articulated by the National Research Council (NRC)
(1) has served as a valuable tool for focusing the Agency's regulatory program (2), its
outreach program (3), and its science program (4).

      In its quest to identify and reduce risks, the Agency continues to analyze many
of its existing data bases.  One particularly large data base relating to chemicals in
manufacturing industries is the Agency's Toxics Release Inventory (TRI)(5).  For the
past decade certain industries have submitted estimates of releases of chemicals from
their facilities.

      The mere existence of the TRI has helped to galvanize actions to reduce waste
generation and releases that might otherwise not have been taken.  For example, when
confronted with the TRI data,  certain industries were energized, for a variety of motives,
to commit to reducing those emissions; cf., the 33/50 program (6) and the Project XL
(7). In addition, the availability of the data in the TRI, coupled with citizens right-to-
know programs (8), has also informed and empowered local citizens to become more
involved in identifying and reducing risks in their own communities.

      Recently (9), the TRI program has been expanded by the Agency to cover  more
chemicals, more industries, and more facilities. Therefore, the data base will become
even broader and more complete in the future.  Consequently, the Agency and others
are exploring new ways in which these data can be used to  help fulfill the mission of the
Agency. For example, the Office of Pollution Prevention and Toxics is developing a
technique that combines TRI release data , chronic human health effects (but not
ecological effects) information, and exposure data  (including analysis and generic
computer transport and fate models) to generate "risk indicators" that would be useful
to a number of Agency programs. This technique,  the TRI Relative  Risk-Based
Environmental Indicators Project, was the subject of a July,  1997, Environmental
Engineering Committee review that will result in a separate report by the Committee
later this year.

      The subject of this EEC report is the Office of Enforcement and Compliance
Assistance's (OECA) somewhat less extensive effort, the Sector Facility  Indexing
Project (SFIP). The  SFIP incorporates the TRI emissions data and toxicity weighting
factors (taken from the TRI Relative Risk-Based Environmental Indicators Project) in a
system designed to generate an index which not only takes  into account the reported

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quantities of the chemicals but also takes into account the chronic human health
hazards associated with those chemicals, without considering exposure.  The SAB was
asked to examine the technical underpinnings of the use of toxicity weighting factors in
theSFIP.

2.2 Charge to the Science Advisory Board

      In general, the charge is a set of specific questions that guide-but do not
confine-the SAB's review of an issue. That is, the SAB will provide answers to the
charge questions, to the degree that it can. At the same time, the SAB may include
additional comments/insights in their report, depending upon the dynamics of the
particular review panel and the topic under review.

      In this case, the SAB Staff worked with OECA Staff and the Chair of the EEC to
develop a focused charge of two questions to guide the review:

      a)    "The SFIP uses chronic human health toxicity weights adopted from the
            TRI Relative Risk Environmental Indicators.  Does the modified Hazard
            Ranking System  (MRS) scoring methodology used by the indicators
            reflect accepted scientific procedures and evidence regarding the relative
            ranking of chemical toxicity?"

      b)    "EPA currently uses unweighted  TRI pounds to evaluate pollutant
            releases from individual facilities. As a first step towards incorporating
            relative risk in this evaluation, is it acceptable to use toxicity weights to
            provide additional contextual information regarding the human health
            hazards associated with pollutant releases?"

      The Subcommittee developed consensus responses to these charge questions
(Section 3), provided additional perspective on the SFIP (Section 4 and associated
Appendix I, and submitted individual insights that may help the  Agency in dealing with
the SFIP (Section 5 and associated Appendix  II).

2.3 Response to Specific Charge Elements

      2.3.1  First Charge Element

                  "The SFIP uses chronic human health toxicity weights adopted
            from the TRI Relative Risk-Based Environmental Indicators.  Does the
            modified Hazard  Ranking System (MRS) scoring methodology used by the
            indicators reflect  accepted scientific procedures and evidence regarding
            the relative ranking of chemical toxicity?"

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      The MRS scoring system is simply a crude tiering/grouping/"binning" of chemical
toxicity information that was useful in screening abandoned waste sites.  The
procedure can be used in a related way here in this instance, but there are underlying
limitations of which the user must be aware; e.g.,

      a) Only chronic human effects are considered.

      b) There is no consideration of multiple effects.

      c) There is no consideration of severity of effect.

      d) There is no consideration of ecological effects.

      e) There is no consideration of exposure.

A more technically defensible approach would be to deal with the hazard information
for each chemical separately and group/bin the materials at the end of the analysis.
The Subcommittee did not have time to explore how grouping/binning would affect the
results of a screening application.

      2.3.2 Second Charge Element

                   "EPA currently uses unweighted TRI pounds to evaluate pollutant
             releases from individual facilities. As a first step towards incorporating
             relative risk in this evaluation, is it acceptable to use toxicity weights to
             provide additional contextual information regarding the human health
             hazards associated with pollutant releases?"

      The application of toxicity information to release amount estimates in order to
transform them into some type of toxicity emission data is a step towards getting to, but
falling short of, risk. The procedure does provide some additional information
regarding chronic health hazards associated with pollutant releases. At the same time,
it is important to note that the procedure does not get to risk (i.e., generate risk
numbers) and care must be taken  lest the results be interpreted as such.

      In reaching the policy judgment as to whether or not to utilize this product in the
SFIP, a number of factors should be kept in mind:

      a) Only chronic human effects are considered.

      b) There is no consideration of multiple effects.

      c) There is no consideration of severity of effect.

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      d) There is no consideration of ecological effects.

      e) There is no consideration of exposure.

2.4 Overall Response to the Issue behind the Charge Questions

      The Subcommittee appreciated the Agency's interest in using available
information to make decisions that are more risk-based than would otherwise be the
case. Using toxicity information in some appropriate fashion is a step in the right
direction. At the same time, the Subcommittee agreed that the approach used in the
SFIP does not address risk, perse.  (The reasoning leading to this conclusion is laid
out explicitly in Appendix I).

      The Subcommittee concluded that by adopting the SFIP, the Agency was taking
only  the first step that would get to actual risk.  Members generally agreed that it is
important to use available scientific information to transform the limited facility release
data into toxicity-weighted data in order to get closer to assessing the risks involved.
Members disagreed on whether this transformation, by itself, was sufficient progress to
establish a firm scientific basis for the use of the SFIP.

      The question remains, however, "Where does taking this first step get the
Agency?" There was a range of views expressed among the Subcommittee members.
Some argued that it is better not to take a step until a more fully risk-based approach is
available.  Other members felt that it is better implement the first step now as a part of a
screening procedure than to continue to deal with the raw mass emission  data.

      In the end, the Subcomittee agreed that the issue of whether or not to take the
single first step is a policy question, not a technical question. Issues impacting the
Agency's policy decision include factors such as

      a)    The availability, suitability, and viability of the OPPT TRI Indicators
            project.
      b)    The level of support provided by any submerged rock; for example, in any
            particular case, physical-chemical considerations could provide rough
            estimates as to whether exposure considerations would be likely to
            reverse toxicity-based estimates of potential risk or not.

      c)    The usefulness of a stand-alone hazard product for some additional
            purposes.

The Subcommittee articulates some of the specific shortcomings and opportunities for
improving the SFIP in Section 5 below and its associated Appendix II.

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      As a bottom line, the Subcommittee agreed that the SFIP is a process that is
getting to risk, but it is not there yet. Whether or not the SFIP is sufficiently useful for
the limited purposes to which the Agency wants to put it, in the light of the
Subcommittee's discussion, is a policy call that the Agency must make.
2.5 Other Technical Comments

      A number of the members of the Subcommittee prepared written material to
capture their views.  These extensive comments are included in the Appendix II to this
report and are commended to the Agency: a) as a demonstration of the breadth of
views on these issues; and b) for their individual, not Subcommittee-endorsed, insights
and suggestions for improving the current SFIP.

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                          REFERENCES CITED
1. National Research Council, "Risk Assessment in the Federal Government: Managing
the Process," National Academy Press, Washington, DC, 1983.

2. Ruckelshaus, W.,  "Managing Risk in a Free Society, " Princeton Alumni Weekly,
March/, 1988, pp. 18-23.

3. USEPA, "Workshop on Risk and Decision Making", Office of Policy Planning and
Evaluation, 1985

4. USEPA, "Strategic Plan for the Office of Research and Development", Office of
Research and Development, EPA/600/R-96/059, May, 1996

5. Federal Register, February 16, 1988, Vol. 53, pp. 4500-4540; Web:
www.epa.gov/opptintr/tri

6. 33/50 Program.  1992.  Forging an Alliance for Pollution Prevention. US EPA, Office
of Prevention, Pesticides, and Toxic Substances, EPA-741-K-92-001, August 1992.

7. Federal Register, April 23, 1997, Vol 62,  pp. 19872-19882; Web:
www.epa.gov/projectXL

8. The Emergency Planning and Community Right-to-Know Act. 1995.  US EPA, Office
of Pollution Prevention and Toxics. EPA745/K-95-002, August 1995.

9. Federal Register, May 1, 1997, Vol. 62, pp. 23834-23892; Web:
www.epa.gov/opptintr/tri
                                    R-1

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                               APPENDIX A

    CONCEPTUAL BACKGROUND TO RESPONSE TO THE CHARGE

      In order to understand the SAB's response to the charge, it is important to
understand first a) the components that are contained in the assessment of risk and b)
the goal and process of the SFIP.

1 Components of Risk Assessment

      As defined by the NRC, risk assessment consists of four parts, each of which
addresses a particular question:

      a) Hazard Identification (HI):
            "Is this material toxic; i.e., what, if any, types of toxicities are associated
                 with exposure to the material?"

      b) Dose-Response Assessment (DRA):
            "How toxic is it?

      c) Exposure Assessment (EA):
            "Who is exposed to this material, how often, to how much, and for how
                  long?"

      d) Risk Characterization (RC):
            "So what; i.e., what are the estimates of risk (and uncertainties) to
                  exposed populations?"

      The TRI data base provides some-but certainly not all-information that is
needed to answer these risk questions about "the material".  This acknowledged
limitation results because the TRI only provides a simple estimate of annual amounts of
releases of chemicals to air, water, and land, To consider risk fully, there are many
other issues that would have to be considered.  For example, the HI question of a full
risk assessment covers not only the identity and amount of the material but also all
adverse effects (both human health and ecological; both acute and chronic), all toxic
endpoints (e.g., cancer, reproductive effects, and population impacts), and all data
sources (e.g., in vitro, in vivo, epidemiological, and field data).

      To make the point in another way, performing a risk assessment requires key
pieces of information including toxicity information ti; cf., HI and DRA above) and
exposure information, which, in this  case, includes amount released (ar) and other
                                    A-1

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important exposure information (ei), such as environmental transport and fate, as well
information about populations exposed:

      RISK = F[(ti) x (ar) x (ei)]                                                [1]

In this construct, it is clear that  in addition to the ar information that is provided by the
TRI data base, both ti and ei, must be evaluated in order to say anything definitive
about risk.  It is also clear that if either ti or ei is zero, then the RISK is zero.

      It is important to understand that, in addition to the given ar information, SFIP
focuses only on the ti factor for human health in the RISK equation, gathering
information found in the Agency's Integrated Risk Information System (IRIS),  Health
Effects Assessment Summary Tables (HEAST), and similar sources.  Therefore, by
explicitly not considering ei, the SFIP cannot-nor does it purport to-say anything
definitive about the risk involved with a particular facility.  Instead, the SFIP is taking
some toxicity information and using it to convert the TRI mass emission data  into some
crude measure of toxicity-weighted emission.  In order to estimate the actual  risk, one
would have to gather and evaluate ei, which the SFIP deliberately does not do.
(However, the OPPT TRI Relative Risk-Based Environmental Indicators Project
subsequently reviewed by the EEC does address the question of exposure.)

      The SFIP deliberately constrains the scope of its considerations by focusing
solely on human chronic effects. While the TRI data could arguably be amenable to
some level of treatment for chronic ecological consequences, the yearly estimate
format precludes consideration  of acute effects for both human and ecolgoical
receptors.

Table I summarizes the "what's in and what's  out" of the SFIP regarding risk.
                                     A-2

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                                  TABLE I

                 INFORMATION NEEDED TO EVALUATE RISK
                  (Information considered in SFIP is underlined)
 1. Amount emitted (ar)

 2. Toxicity information on the emissions
       a. Human (ti)
             1) Acute
             2) Chronic
       b. Ecological
             1) Acute
             2) Chronic

 3. Exposure information on the emissions (ei)
       a. Who is exposed
       b. To how much, how often
2. The Goal and Process of the SFIP

      If so few components of risk assessment are included in the SFIP, one might
question the motive behind the SFIP exercise in the first place.  Simply put, the SFIP
seeks "to go part way toward risk "rather than wait for a more complete estimate of the
risk.

      By way of explanation, consider that the goal of the SFIP is to identify-through
an admittedly rough screening procedure-those facilities that may be posing the
greatest human health risks, when only information about toxicity and amounts of
released material are available. For example, consider the case of hypothetical Plants
A and B releasing equal quantities of different materials, Chemical  X and Chemical Y,
each year; cf., Table II
                                     A-3

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                                  TABLE II

        HYPOTHETICAL TRI DATA FOR TWO HYPOTHETICAL FACILITIES

          FACILITY         EMISSION        ANNUAL RELEASE

              A             Chemical X            1000tons/yr
      On its face, it might appear that the two facilities are equal in their potential for
posing a risk, in that each of them is releasing 1000 tons of material each year.  And
yet, as noted above, there is not enough information upon which to reach such a final
judgment. For example, there is no definitive nor distinguishing ei.  In addition, the
identity of the materials as Chemical X and Chemical Y might lead to information on
relative toxicity of the two compounds and, therefore, the  relative potential for risk.  For
example, if Chemical X were a persistent, bioaccumulative, high potency carcinogen
while Chemical Y were a comparatively short-lived,  low potency carcinogen, one might
anticipate that Facility A would likely pose a greater chronic risk than would Facility B.
However, the actual risks presented would depend on the specific exposure conditions
in the two cases.

      That is, one could imagine a case in which

      a)    Facility A is releasing Chemical X in a remote area with a very low
            population, and

      b)    Facility B is releasing Chemical Y in a more populated area.

Under these conditions, the potential risk posed by Facility B might be greater than that
for Facility A;  i.e,. the reverse of what might have  been anticipated from toxicity
considerations alone.  (To be more definitive, we would have to have additional
information, such as the environmental transport and fate of the Chemicals X  and Y
and the activity patterns and susceptibility of the respective populations.)

      In short, if one were willing to set the exposure issues aside in this case, one
could use toxicity information (e.g., cancer potency values and  reference doses) to
transform the TRI data into some type of toxicity-weighted index for screening purposes
that could be used as an indicator of risk potential, accepting the fact that the  missing
site-specific exposure information-if known-could significantly alter the validity of the
conclusions from the screen.
                                     A-4

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      This approach is the one utilized by the Agency in the SFIP.  The TRI reported
quantities are transformed by applying modified scores first used in the Agency's
Hazard Ranking System (MRS) for screening potential candidates for the National
Priority List of Superfund sites.
                                     A-5

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                               APPENDIX B

       COMMENTS BY INDIVIDUAL SUBCOMMITTEE MEMBERS
      These comments, ideas, and suggestions are those of the individual
Subcommittee members who authored them and should not be construed as
representing Subcommittee-endorsed positions. The Subcommittee consensus is
contained in the body of the report per se.

1. DR. WILLIAM ADAMS

1.1 Response to question #1

      Scoring and ranking procedures are by their very nature subjective.  There are
now more than 100 different scoring techniques for prioritizing and screening chemicals
for different purposes.  Recently, many of these procedures were reviewed  and some
principles developed which lay the groundwork for developing and assessing scoring or
ranking approaches (SETAC Scoring workshop, 1996).  The value of a given
methodology is often determined by its ease of use, its ability to help interpret masses
of data, and its broad scale acceptance.  This presumes that the approach has a good
scientific basis.  The SFIP Toxicity Weighting approach has significant limitations both
in the design of the toxicity ranking factors and in the data which are obtained from the
TRI data base.

      The following describe some of the limitations associated with the proposed
toxicity weighting factor approach.

      The Hazard Ranking System (MRS) and the Toxicity Release Inventory (TRI)
form the basis for the current approach. Neither of these systems were designed to be
used for human health or ecological risk assessment. The MRS is a screening level
tool and the data collected and used in that system are designed for screening level
decisions. It is an approach which is based primarily on exposure estimates, not risk or
relative risk.  The TRI reports chemical release on an annual basis for the purpose of
informing the community on chemicals used and released into the on a facility-to-facility
basis.  The  data most often are not collected and reported in a way that is useful  for
accurate risk-based decisions, even at the screening level.

      The current approach confuses risk, relative risk, and hazard. Risk estimates
are based on the relative relationship between exposure concentrations and effect
concentrations and require both components.  The current approach uses release
amounts data weighted by a toxicity factor (hazard) in an effort to provide a relative
risk-based score for each facility of interest.  The information for both exposure and

                                     B-1

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effects are unknown in this procedure and, hence, one would have to conclude that the
(relative) risk is therefore unknown.  The current approach is not transparent relative to
the assumed population at risk, the assumed effects, or the assumed exposure.
Without clearly stating the assumptions and providing sufficient validation to support
them it is impossible to determine the accuracy of the approach.  For screening level
approaches to be effective there has to be some level of confidence that the approach
provides a degree of confidence in the screen. Additionally, no information is provided
on the uncertainty or accuracy of the scores generated in the weighted scoring
procedure.

      The question as to whether or not TRI release data are more  informative when
multiplied by a toxicity factor has not been adequately addressed. In some cases this
appears to be true, in other it does not.  The weighting approach is a subjective ranking
system and it lacks sufficient depth to provide an accurate scoring approach.

      The weighting approach for carcinogens assumes that thresholds are not
appropriate for any of the chemicals. This is not consistent with the  state-of-the-
science and does not reflect the Agency's position on all chemicals.  Clearly this is
inappropriate for essential metals which may also cause cancer at high doses.

1.2 Response to question #2

      The proposed toxicity weighting approach to evaluating TRI data has significant
limitations as a first step towards incorporating relative risk  in the evaluation.  Pounds
released multiplied by a toxicity factor does not constitute a risk index. Agency risk
assessment guidelines for both human  health and the environment are based on the
premise that risk is a measure of the potential for exposure concentrations to exceed
known  effect concentrations.  Both components must be measured and used with some
degree of accuracy to develop reasonable risk statements.  This is true even for
screening level assessments.  The current approach does not measure or estimate
exposure in a meaningful way.

      Additionally, the effects data (toxicity weighting factors) also have serious
limitations.  The methodology handles the scores in an additive manner.  Scores for
both non-carcinogens and carcinogens are added together and scores for non-
carcinogens that have different modes of action are also added. This approach makes
it difficult to sort out where the real hazards exist.  The proposed approach also ignores
the fact that some carcinogens clearly appear to have thresholds, it uses only the most
sensitive endpoint,  and it uses weighting factors for some chemicals which appear to
be excessively large. It was noted during the SAB review that the weighting factors for
sulfuric acid and  ammonium sulfate appear to be considerably overstated.
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      In summary, the weighted hazard information gives the appearance of providing
risk-based information which aggregates and presents data in a way which is easily
understood, when in fact it does not present risk information at all. The hazard scoring
numbers have the potential to be very misleading in many cases. The use of TRI
information in a way that assumes that the reported poundage somehow equates to risk
is not providing the public with accurate information on risk.

      I recommend that the Agency develop an alternative procedure that accurately
estimates or measures both exposure and effects and which allows for quantitative risk
estimates associated with chemical  releases to the environment. Such an approach
will be defensible, will provide the public with information that is factual, and will assist
industry to focus its pollution prevention efforts in the proper place.  The ability to
develop such an approach is well within the Agency's grasp. The Toxicity Indicators
Program is nearing completion and may be useful towards that end.  Finally, in my
view, the Agency should incorporate additional stakeholder review in the process of
interpreting the TRI data and IRIS effects data for risk assessment purposes. This will
ensure the accuracy of the data and utility of the final overall methodology.

2.  DR. STEVE BROWN

      The MRS methodology was designed to help decide whether hazardous waste
sites should be placed on the National Priorities List for Superfund status.  Due in part
to earlier SAB input, EPA restructured the procedure so that both the carcinogenic
potency and chronic toxicity scales would be stepwise proportional to risk (presuming
the input toxicity information was reasonably accurate, at least in a relative sense).
This change was an improvement from the old MRS system in which the steps were
unevenly related to risk.

      Although the MRS methodology is not seriously flawed, I recommend that  EPA
consider three further improvements. First, the toxicity values from IRIS, HEAST, and
the disposition process should be used directly rather than rounded by assigning them
to bins an order of magnitude wide.  Second, the carcinogenic potency values should
be converted  to "Risk Specific Doses" (RSDs) by dividing the potency into the risk
value selected to be equivalent to exposure at the Reference Dose (RfD) - currently
one in ten thousand or 10"4.  Then both the RSDs and RfDs can be divided  into the TRI
release figures to yield indexes, obviating the need to use two different scales for
indexing. The units would be lbs-kg-day/(mg-yr), which could be converted to Ibs or kg
by using appropriate conversion factors. Third, the final indexes should be shown to no
more than one significant figure; EPA should consider using categories at that point
rather than specific values for the toxicity-weighted releases. For example, "A" could
include any facility indexed above 1011 lbs-kg-day/(mg-yr), "B" indexes between 1010
and 1011, and so on.
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      Several related issues were raised in the statements by the public and in our
discussions. My findings on them are presented below.

2.1    Issue:  Because the MRS toxicity weighting scheme was developed for a
      different purpose, it should not be used in the OECA SFIP.
      Finding: Although I agree with the premise that the objective must be considered
in determining the scientific validity of a procedure, the MRS and SFIP objectives are
not sufficiently different to invalidate the use of the MRS system,  especially if our
recommendations for improvement are accepted.

2.2    Issue:  The toxicity weights should be binned rather than derived directly
      from the toxicity values because the latter would imply more accuracy than
      justified and because a small change in toxicity values would usually not
      change the bin assignment.

      Finding: Neither argument is sound.  Binning the toxicity values loses information
and can make artificial distinctions between chemicals that fall just on either side of a
cut point. Binning, if done at all, should be done at the end of the process. Presenting
up to 11 significant figures in Attachment (5) is unwarranted when the input information
has been binned to less than 1 significant figure. If a toxicity value should change and
move across a cut point, binning can improperly exaggerate the magnitude of the
change. Reindexing will be done no more than annually, when the new TRI data
become available. At that time, all the toxicity numbers will have to be re-checked for
changes. It is little additional work to change the weighting factors accordingly.

2.3     Issue: The discounting of Category C carcinogens relative to Categories A
      and B is arbitrary.

      Finding: I do not disagree with the idea behind discounting the potencies of
Category C carcinogens: the probability that the substance will be carcinogenic in
humans at the potency derived from animal studies is likely less than for Category A or
B carcinogens. Therefore, it may be appropriate to discount them.  However, the
magnitude of the discount factor is not derivable from any current scientific data and
must be a policy decision.

2.4    Issue:  Reference Doses are derived for substances that are presumed to
      have thresholds of toxicity, whereas carcinogenic potency factors are
      derived under the assumption of linear, no-threshold risk. Therefore, they
      must be treated differently.

      Finding: The contention is certainly true if the SFIP indexes were to be construed
as risks.  EPA maintains that they will not, and are for priority-setting and information
purposes only. For the latter purpose, one can argue that the magnitude of the RfD is

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an indicator not of risk but of the likelihood that the RfD will be exceeded in some
person if a release of a fixed magnitude occurs, all else equal.  In this sense it is
equivalent to the likelihood that the release will create a cancer risk in some person in
excess of the benchmark risk (now 10"4).

2.5   Issue: The equivalence risk level of 10"4 is arbitrary and may be
      inappropriate.

      Finding: I agree that the level is a policy call and not a scientific decision. It is
similar in many respects to the Superfund action criteria, which recommend remediation
if total cancer risk exceeds 10"4 or exposure to non-carcinogens exceeds a Hazard
Index of 1.0. Lowering the equivalence level to 10"5 or 10"6 would have the effect of
focusing more attention on facilities with carcinogens, while raising it would focus more
attention on sites with non-carcinogens.

2.6   Issue: Summing indexes over chemicals or media of release may be
      inappropriate.

      Finding: It is true that toxicologists generally advise against summing Hazard
Quotients (estimated  dose/RfD) over chemicals that do not have the same endpoint
and mechanism of action.  However, if one adopts the probability viewpoint about the
significance of the indexes, then a site with several chemicals is more deserving of
attention than one with only one chemical with a similar index. Regarding summing
over media, the underlying (unstated)  assumption is that a release is just as likely to
result in a dose of a given magnitude,  independent of medium of release. That
assumption is critical  to the whole SFIP toxicity weighting scheme, and therefore
summing adds no additional difficulties. I  doubt that summing or simply reporting the
highest index will be much  different if EPA adopts my suggestion to bin the output
indexes.

2.7   Issue: The toxicity  weights derived from the disposition process (DP) are
      less reliable than those from IRIS and HEAST.

      Finding: Lacking a good description of the DP  (or, for that matter, of the HEAST
process), I am unable to conclude much about the validity of the toxicity weights
derived from it.  I do not disagree with the idea of supplying toxicity values for the
chemicals  in TRI but not evaluated in IRIS or HEAST, but I was surprised at several of
the weights shown in  Attachment (3).  The Agency should provide a description  of the
DP and indicate on Attachment (3) the source  of the toxicity information (IRIS, HEAST,
or DP).  Moreover, it should review the values  with an independent group of
toxicologists (within or outside the Agency) to  identify any that seem  unusual and verify
whether the interpretation of the base  information was appropriate.  Some of the
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substances worthy of review are sulfuric acid, ammonium sulfate, aluminum, lead,
manganese (inhalation), and zinc.

2.8   Issue: The use of inhalation toxicity values for releases to air and oral
      toxicity values for all other releases may not be justified.
      Finding: While intermedia transfers can greatly affect the correct toxicity factor(s)
to use for a medium  of release, the Subcommittee has no quarrel with EPA's decision
to divide the weights in this manner as a first step.

2.9   Issue: Particularly with respect to RfDs, the severity of the endpoint can
      differ substantially from one chemical to another.

      Finding: This problem is acknowledged, but is endemic to the current process of
developing RfDs, and OECA cannot be expected to deal with it in the SFIP.

                         Relative to Charge Element #2

      I agree with the premise that risk is a better indicator of priorities for enforcement
attention or for informing the public about facilities in their communities than is the
simple use of release estimates from the TRI.  The use of toxicity weights is a step in
the right direction, but the Agency could be even more forceful in its explanation that
the resulting indexes may have little to do with risk even in a relative sense.

      As with the first charge,  several related issues were raised. My findings on them
are presented below:

2.9   Issue: The assumptions behind the indexing project are not well explained.

      Finding: In producing the toxicity-weighted TRI release information as a means
of informing the public and setting OECA priorities, EPA is implicitly making some
assumptions about the facilities. Essentially, EPA assumes that,  save for the identities
of the chemicals released and  the amounts released to different media, all facilities are
the same.  For example, the emissions  to air are released at the same height and with
the same buoyancy,  the meteorological conditions are identical, the temporal pattern of
release is the same,  the most exposed  person is located at the same distance and
downwind direction,  and that person has identical patterns of activity that influence his
or her exposure. Such assumptions need to be explained in greater detail and their
influence on relative risk rankings needs to be honestly revealed.

2.10  Issue: Towards which  definition of "risk" the indexing  project is attempting
      to advance is not clear.
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      Finding: The term "risk" is interpreted differently in different contexts. By
creating an index that uses only release quantities and toxicity weights, EPA is
implicitly moving toward a ranking based on individual risk to a highly exposed
individual, a definition that is probably appropriate from  an environmental equity
perspective. By not including population as another weighting factor, EPA is implicitly
moving away from a population risk or incidence definition that might be more
appropriate from a public health perspective.

2.11  Issue: The public may be confused or misled  by the toxicity-weighted
      release calculations and the indexing project  results should not be
      released.

      Finding: I heard contrasting views on this subject which I do not have the
expertise to resolve. Although EPA has offered many caveats regarding the
information, it could do more to reduce the possibility of misinterpretation, for example
by including the caveats on Attachment (5). It also might consider using a focus group
to see how the public interprets the results.

2.12  Issue: EPA should not issue a toxicity-weighted release index but should
      wait for an index that better approximates risk.

      Finding: I agree that toxicity-weighting is a step in the right direction, but note
that it may be a small  step. The Subcommittee was not unanimous in recommending
for or against release  of the indexes at this stage of development.  Why OECA is taking
a somewhat different approach from the OPPT TRI Indicators project and attempting an
earlier completion was not clear to me.

2.13  Issue: TRI and toxicity information should not be used to target
      enforcement activities.

      Finding: The Subcommittee was not charged with such policy issues.  However, I
do not disagree with the premise that facilities posing the most risk might be the  best
place to start when  enforcement and compliance resources are limited.

2.14  Issue: The TRI data, not just the toxicity data, may be substantially
      inaccurate.

      Finding: The Subcommittee did not specifically address this issue.  Binning the
output estimates as suggested above under the response to Charge (1) would help to
alleviate concerns about the TRI.

2.15  Issue: The units used to report the results in Attachment (5) are incorrect
      or misleading.

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      Finding: It would be more accurate to label the column of Total Toxicity
Weighted Release as being in Ibs, because the toxicity weights are alleged to be
dimensionless.  The proposal to use toxicity information directly would also result in
numbers with a dimension of mass, but the numerical values would be different.
Choosing the actual unit (Ibs vs. tons, for example) can make the numbers seem
smaller or larger to the unwary.
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3. DR. LINDA GREER AND MR. TOM NATAN

      These written comments supplement the discussion held on April 29, 1997 in a
special Topics Subcommittee meeting of the Environmental Engineering Committee of
the Science Advisory Board. At that meeting, EPA staff presented a component of its
Sector Facility Indexing Project - the use of toxicity weighting - for SAB review and
comment. Both of us work extensively with the publicly available information provided
in the Toxic Release Inventory as well as with the lay public concerning pollution
around facilities in their neighborhoods.  This topic is of great importance  to the public's
right to know, and we are pleased to have this opportunity to highlight our thoughts in
writing.

      When a community becomes concerned about an industrial facility in its midst,
or, for that matter, when we in the national environmental community begin research  on
a particular plant or industry, our line of inquiry is approximately the following:

      a)    How many pounds of waste and emissions are reported from this facility?

      b)    How "bad" are these chemicals and their releases for human health and
            the environment?

      c)    How would these releases affect people in the area?

      TRI has, to date, been an invaluable resource in answering our first important
question, which  concerns simple environmental loading.

      Beyond loading, however, it has been difficult to systematically assess the level
of hazard of  releases in  reported TRI, because we have lacked any sort of scoring
mechanism that indicates relative hazard of the reported compounds. The toxicity
weighting factor project developed in the Office of Enforcement and Compliance
Assurance (OECA) responds to this gap by providing methods to evaluate the potential
hazard of TRI wastes and releases in an objective and methodologically transparent
way.  It thus  allows us to answer the second question about TRI emissions important to
communities and environmental groups.

      Several participants commented during our meeting that reporting on hazard
alone, without taking exposure into account, was not desirable. Their primary concern
was that the  public would be confused about hazard information that  was  presented in
the absence of information about exposure.  We strongly disagree with  these
comments.  First of all, many people are interested in pollutant loading  per se, and not
in a risk calculation, because they distrust exposure calculations.  Others  are interested
in waste and emissions per se because they are concerned with pollution prevention
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opportunities at the plant. In both of these cases and several others, information on
hazard distinct from "risk" is valuable.

      Furthermore, as evidenced in the string of questions most commonly raised by
the public, people will not be confused with information on hazard. To the contrary, the
sophisticated public, which includes many of those who currently use TRI data,
understand very well the difference between hazard and risk and would find the
information more useful in a disaggregated state than combined.  For the lay public not
experienced in TRI and pollution issues, we are confident that EPA can explain the
limitations of hazard data in a way that is readily comprehensible, as it has explained
the limitations of simple environmental loading in the TRI to date. We should not
under-estimate the ability of the public to come to grips with technical information such
as this, especially if the information is accompanied  by an explanation of its usefulness
and limitations. The public has proved itself fully capable of understanding these sorts
of distinctions and, in fact, intuitively understands the differences between the terms
"hazard" and "risk".  People know, for example, that  rattlesnakes are dangerous but
pose no threat to them if they are not  in a rattlesnake habitat!  In addition, the
combination of hazard information and releases will  provide another tool for
communities to determine the impact of environmental improvements at facilities in their
neighborhood where the potentially exposed populations don't vary much - essentially
providing a surrogate for the exposure piece not included in the indexing project.

      Finally,  it is not just the public and the environmental community that will find
disaggregated hazard information useful.  Industry itself, when trying to set priorities for
voluntary reductions of its TRI wastes and emissions, undoubtedly often finds itself
uncertain as to which of its chemicals most merit reductions from a human health and
environmental perspective.  The toxicity weighting factors will help those individuals in
industry interested in reducing their company's environmental "footprint" to select waste
streams for pollution prevention assessment and emission control. Certainly they
would want to understand the environmental fate, transport, and ultimate risk posed by
their wastes. But they will also  find useful information on the inherent hazard of these
compounds, in order to consider occupational exposure scenarios as well as impact
across diverse environmental media.  The hazard information will thus add an important
component to waste minimization and pollution prevention planning which is currently
based almost exclusively on savings in raw material costs.

      The dangers in waiting until the exposure piece is done before releasing this
valuable hazard weighting scheme are thus two-fold. First,  it will unnecessarily delay
transmission of a valuable EPA work product. Second, it will obfuscate some of the
important differences between hazard and risk which we all are concerned to highlight.
Thus, we strongly urge the issuance of the Toxicity Weighting Factors without delay.
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We have a few other "fine points" that merit attention, although none of them rise to a
level of concern that should delay the issuance of this document.

      a)    Ecological hazard.  As we noted at the meeting, we are concerned with
            the exclusive focus on human health and the absence of ecological
            hazard weighting factors.  We understand that the ecological factors are
            on a slower track and will ultimately be a part of the toxicity weighting
            package. We urge that EPA continue to place high priority on this task,
            since there are several notable TRI compounds, such as copper and
            nickel,  which are disproportionately toxic to some ecosystems.

      b)     "Binning". Several commentors, including the Environmental Defense
            Fund, objected to the clustering of compounds into bins which reflect
            order of magnitude differences in the hazard they pose.  However, there
            are pluses as well as problems associated with this approach.  We
            believe that on balance, the "binning" should be maintained as in the draft
            presented, because the use of the actual toxicity number associated with
            a compound would give a false sense of accuracy to the hazard numbers.
            In our limited experience with risk assessments based on TRI data, it  is
            rare that a change lower than one order of magnitude in toxicity numbers
            has any bearing on the outcome.

      c)    Non-IRIS compounds. The toxicity portfolios of a small number of
            chemicals on the TRI are not sufficiently mature for those chemicals to be
            found in the  EPA IRIS data base.  In response, EPA has made its best
            effort, using  expert judgment, to assign a hazard score to that chemical.
            We are fully  supportive of EPA's decision in this area. It would not serve
            the public interest to simply "punt" on a chemical that is not in IRIS and
            would leave  a false impression that chemicals with inadequate  toxicity
            information are not as toxic as those that are found in the IRIS data base.
            Although we recognize that a full IRIS work-up is  better than individual
            efforts for this project,  the fact that the Sector Facility Indexing Project is
            only clustering chemicals into bins by order of magnitude, combined with
            the fact that  gaping holes in the hazard data base would be misleading to
            the public, compels us to support  EPA's decision  in this area. We urge
            that EPA make it a high priority to work on TRI chemicals that are not in
            the IRIS data base, especially those generated and emitted in large
            quantities, to resolve outstanding  issues associated with their toxicity. In
            the meantime, this project should move forward and not wait.

      In sum, we are very pleased with the work that was presented to us on the Use
of Toxicity Weighting Factors in the Sector Facility Indexing Project and urge that the
document be released expeditiously.
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4. DR. RICHARD KIMERLE

4.1 Overall Comments

      The Sector Facility Indexing Project (SFIP) and the use of the chronic human
health weighting factors needs much improvement before it can be accepted as
technically sound enough to provide any benefit to the public, regulatory agencies, and
dischargers. However, we do need a tool to effectively sort out, priorities, and
communicate potential human and ecological health risk associated with TRI
discharges  and all releases.  Industry will then be able to focus their pollution
prevention resources on the chemical discharges having the  greatest potential adverse
impact on ecological and human health.

      I believe (and I hope the SAB review Panel can agree) the proposed Sector
Facility Indexing Project must undergo a major revision incorporating better science.  In
its current form, SFIP cannot be defended as scientifically sound enough for use even
as an "interim step toward the longer term goal of more complete  risk-based modeling
that will factor in chemical fate, transport and exposure". To draw any conclusions and
communicate those conclusions to regulatory agencies and the public is not
scientifically sound.  The reasons the procedure is not acceptable is that only chronic
human health factors are used without including the recognized factors of chemical
fate, transport, exposure, ecological, other human health effects, exposure, and most
importantly, risk assessment.

      It would not be that difficult, nor should it take very long, to seek the input of
other chemical scoring and ranking procedures found within and outside the EPA and
develop the comprehensive risk based approach which is needed. Canada, Michigan
DNR, EPA Indicators model, and the University of Tennessee under an EPA grant have
already developed procedures that are more risk based than  the current SFIP
procedure.  The Society of Environmental Toxicology and Chemistry (SETAC) held a
workshop and will be publishing a book on the scientific practices of chemical scoring
and ranking.

4.2 Specific Comments

      a)    The SFIP chemical scoring and ranking approach that is most likely to be
            accepted by the technical community is one that is risk based right from
            the start.  That is, any and all decisions on chemicals would be founded in
            the accepted risk assessment paradigm where data on toxicological
            effects and potential for exposure are both available to derive at a risk
            characterization conclusion. To use only toxicity or  only exposure leads
            to confusion and rejection by the scientific community. The results from
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            risk based assessment are easiest to explain to public and most helpful to
            the risk management decisions, both regulatory and industrial.

      b)    Ecological health effects were an obvious omission and I believe that this
            to be an essential part of any chemical scoring procedure.  The above
            mentioned chemical scoring approaches all have a method to include
            ecological data and a manner similar to the human health approach.

      c)    I believe that the SFIP procedure should include commonly practiced
            chemical fate modeling procedures to appropriately modify the total TRI
            chemical releases.  These procedures are quite routine and have been
            used in many of the published chemical scoring and ranking publications.

      d)    An overall algorithm should be considered that scores (1) acute and
            chronic toxicity for human health; (2) acute and chronic toxicity of aquatic
            and terrestrial organisms; (3) total pounds released; (4) chemical fate
            losses; and (5) potential for exposure to populations. Other factors can
            also be included. When the algorithm is "transparent", it is possible to
            generate a single score for each chemical at each discharge site and then
            look into the data base for a better understanding of the source of the
            scores and sub-scores.

      e)    Every chemical scoring and ranking  procedure has numerous
            characteristics that make the procedure look to be arbitrary.  It is not until
            some runs and sensitivity analyses are made on real data under real
            conditions that one can gain confidence that the scoring model provides
            useful data. Therefore appropriate real data analyses need to be a part
            of the development of an approach.

5.  DR. JOHN MANEY

5.1  Charge Element #1

      Does the Hazard Ranking System scoring methodology used by the indicators
      reflect accepted scientific procedures and evidence regarding the relative
      ranking of chemical toxicity.

      5.1.1 HRS Model as applied to Operating Facilities

      The Agency proposes to use the Hazard Ranking System (HRS) to calculate a
proportional weighting factor for chronic human toxicity. The HRS  has proven to be a
useful tool for preliminary screening of abandoned hazardous waste sites.  The HRS
uses a conservative screening model that uses information from  preliminary
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assessments (PA) and rudimentary site investigations (SI) to determine if a site should
be included on the National Priority List.  The MRS is designed to favor false positives
as opposed to false negatives. There is a key difference however, between the
intended use and that of the proposed use of the MRS by the SFIP. The MRS was
designed to estimate releases from abandoned waste sites, not operating facilities.

      It is also important to note, that as described in the SAB review documents, the
Agency is not proposing to employ the MRS model but is proposing to employ only that
portion of the MRS model that pertains to chronic human toxicity and excludes those
portions of the MRS that address acute toxicity, environmental effects, exposure routes
and receptors.

      The Agency's decision to employ only a portion of the MRS and the fact that the
MRS is applied to operating facilities leads one to conclude:

      a)    That the toxicity-weighted annual release numbers are not an accurate
            measure of hazard or toxicity, are at best relative and should only be used
            by those familiar with the assumptions of the MRS and the limitations of
            the data.

      b)    All data tables and reports should be properly qualified with legends and
            notations indicating that the toxicity-weighted data are not accurate
            representations of risk to the public or the environment and  use of the
            data as a screen, to make comparisons or to establish priorities should be
            restricted to those familiar with the MRS model, underlying assumptions
            and the fact that the reported data only address the human chronic
            toxicity of releases for TRI-specified compounds.

      5.1.2  Toxicity Values used to estimate Weighting Factors

      Based on testimony presented at the  SAB meeting, the Agency should review
the validity of the slope factors and RfDs used to weight release data. This review
should be initiated with an evaluation of the toxicity data for lead, zinc and aluminum.

      5.1.3  Releases from Off-Site Shipments

      The Agency's intention is to employ the SFIP toxicity-weighted data for a number
of applications including the following:

      a)    Evaluate low and high toxicity chemicals within a given industry.

      b)    Compare across facilities
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      c)    Focus pollution prevention

      d)    "identify high performing facilities that can be recognized under the
            Environmental Leadership Program"

      e)    "taking a more holistic, multi-media perspective"

      The above uses conflict with the Agency's intention of only examining "on-site"
releases.  This on-site focus can result in data-use limitations,  if significant amounts of
chemicals are transferred off-site to POTWs or RCRA TSDFs and later result in
releases.  Section 40 CFR 372.85  (b)(16) of the EPCRA-TRI regulations require that
facilities supply "information on transfers of chemicals in wastes to off-site locations".
This information includes the annual amount of transferred chemicals, the
concentration of the chemicals in the waste before treatment, and the type and
efficiency of treatment.  The SFIP needs to track these off-site  transfers to properly
perform intra-facility and inter-facility comparisons and to ensure a significant off-site
release is  not overlooked.  The off-site transfers can be tracked in a column separate
from on-site releases.  To facilitate comparisons the off-site data could be corrected for
treatment efficiency and  subjected  to fate and transport models to estimate a release.
Although, this mechanism for including off-site shipments may  not be ideal, it should
increase the accuracy of comparisons and offer the data user additional information.
Using this approach will  still allow on-site releases to be tracked separately. However,
the Agency must consider off-site shipments to use the toxicity-weighted data for the
previously stated applications.

      5.4.1  Issues Raised by Other Members of the Subcommittee

      a)    Other subcommittee  members proposed inclusion of environmental
            effects into the weighting of the TRI data.  I agree with this approach, but
            strongly recommend  that the environmental effects not be combined with
            the human chronic toxicity factor. The TRI release data should be
            weighted twice, once for chronic toxicity and once for environmental
            effects and the data should be reported in separate columns. The
            separate columns would prevent loss of information and would facilitate
            use by those who may only be interested in human health or
            environmental effects. The presence of the two columns and possibly
            another two columns for off-site shipments would help  to capture the true
            complexity of the data evaluation and minimize misuse.

      b)    I agree with the proposal to employ actual slope factors and RfDs as
            opposed to the use of order-of-magnitude bins. This procedure would not
            round-off until reporting the final toxicity-weighted value, which would then
            be rounded to 1 significant figure.
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6. DR. LAUREN ZEISE

6.1 General Findings/Comments

      The general approach, development of indicators of hazard by weighting dose
surrogates by toxicity measures, is scientifically sound. The approach is a significant
advance over the previous one of using pounds released, without regard to the relative
toxicity of the chemicals released.

      Further, the adoption by the Agency of the scoring methodology from the
modified Hazard Ranking System is reasonable.  Nonetheless I have reservations
about some aspects of the methodology, and is therefore proposing improvements for
the Agency's consideration. I believe these modifications can be made without
substantial expenditure of additional resources or undue  delay in implementation.

6.2 Specific Findings/Comments

      a)    Proportionality of Weights and Toxicity Measures

      The toxicity weights assigned are roughly proportional to the degree of toxicity.
To the extent feasible, this should be the case, with the caveat that severity of effect
should be considered. For example,  in cases where the RfD is based on an effect
which is not life-threatening, a smaller toxicity measure should be considered than if
the opposite were true.  The Agency decided not to consider severity in its proposed
procedure, indicating that a subjective evaluation of relative severity would be required.
I believe this can be mitigated by clear criteria and by considering only two or three
categories of severity, and by reviewing documentation serving as the basis for the
addition of the chemical to the TRI.

      b)    Categorical weights

      I agree with the Agency that dose response relationships are typically not known
with accuracy, and that there are often significant uncertainties associated with RfDs
and cancer slopes.

      Nonetheless, the adoption of categorical weights, rather than toxicity weights
directly proportional to cancer slopes and indirectly proportional to RfDs, introduces
additional imprecision. The amount introduced in some instances may result in
misleading rankings. The disadvantage of giving the impression of accuracy can be
addressed farther downstream in the exercise by for example, rounding of the toxicity
weighted releases.

      c)    Scheme for A, B and C carcinogens


                                     B-16

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      The proposal of using cancer slopes to assign toxicity scores for C carcinogens,
but reducing their score by an order of magnitude below A/B carcinogens having the
same slope is, in my judgment, reasonable.
      The same approach could be used in the event that the suggestion for a
continuous, rather than categorical, toxicity weighting scheme is adopted.

      d)    Toxicity  scores derived from data from secondary sources

      When toxicity values are not available in IRIS or HEAST, the Agency derived
toxicity weights from information in secondary sources. At least one of the secondary
sources noted in the Agency documentation is not adequate for this purpose
(Hazardous Substances Database). During the meeting on April 29 several
examples were raised of toxicity weights that did not seem credible, particularly for
some agents for which acute effects have been a concern.
      Greater (internal) peer involvement and review of values derived from secondary
sources is needed, and alternative approaches, including expedited approaches using
primary literature, should be considered. Other arms of the Agency, such as the
National Center for Environmental Assessment, could be of great assistance.

      e)    Harmonization across cancer and non-cancer endpoints

      The development of a single scale on which to compare facilities is appealing,
and the proposed procedure seems reasonable.  It is difficult to endorse this approach
without a better understanding of its implications.  The comparability of values among
non-carcinogens is unclear given the variety of uncertainty factors applied and of
endpoints serving as the basis for the derivation.  In addition, the current approach
does not provide ways of accounting for periodic large releases versus low continuous
releases in developing toxicity weighted release values. Until there is more experience
and understanding  of the toxicity weighted releases, the toxicity weighted scores for
cancer endpoints should be totaled and reported separately whenever totals across
cancer and non-cancer endpoints are reported.
                                     B-17

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