v>EPA
United State1;
Enwionmental Piotection
Aqency
Otlice of
Toxic Substances
Washington, DC 20460
EFA-560/11-80-010
May 1980
Toxic Substances
Proceedings of the
EPA Workshop on the
Environmental Scoring
of Chemicals
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ORNL/EIS-158
EPA-560/11-80-010
Contract No. W-7405-eng-26
PROCEEDINGS OF THE EPA WORKSHOP ON THE
ENVIRONMENTAL SCORING OF CHEMICALS
Washington, B.C.
August 13-15, 1979
Compiled by
Robert H. Ross
Health and Environmental Studies Program
Information Center Complex/Information Division
Oak Ridge National Laboratory
Oak Ridge, Tennessee 37830
and
Justine Welch
Assessment Division
Office of Toxic Substances
U.S. Environmental Protection Agency
Washington, D.C. 20460
Work sponsored by the Assessment Division, Office of Toxic Substances,
U.S. Environmental Protection Agency, Washington, D.C. 20460, under Inter-
agency Agreement No. 78-D-X0453.
Project Officer
Justine Welch
Date Published: May 1980
OAK RIDGE NATIONAL LABORATORY
Oak Ridge, Tennessee 37830
operated by
UNION CARBIDE CORPORATION
for the
DEPARTMENT OF ENERGY
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This report has been reviewed by the Office of Toxic Substances, U.S.
Environmental Protection Agency, and approved for publication. Approval
does not signify that the contents necessarily reflect the views and
policies of the U.S. Environmental Protection Agency, nor does mention
of trade names or commercial products constitute endorsement or recom-
mendation for use.
This document is available through the National
Technical Information Service (NTIS), Springfield,
Virginia 22161, Telephone No. (703) 557-4650.
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CONTENTS
Figures v
Tables vii
Preface ix
Abstract xi
1. Introduction 1
2. San Antonio Environmental Subgroup Summary 4
3. Integration of Scoring Systems of Environmental Subgroups ... 4
4. Testing and Modification of the Integrated System 19
5. Testing the Modified Scoring System 30
6. Discussion and Conclusions 30
Appendix 36
References 37
FIGURES
1. Toxicity matrix for proposed scoring system 5
2. Data needed for estimation of environmental concentrations . . 25
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TABLES
1. Chemicals used to test scoring system 3
2. Scoring system for environmental toxicity 6
3. Scoring system for bioaccumulation in aquatic species 7
4. Scoring system for persistence, bioaccumulation potential,
and mobility 8
5. Scoring system for environmental concentration 9
6. Ecosystem components of scoring system 10
7. Format for displaying exposure and fate of chemicals 12
8. Format for displaying effects 13
9. Format for displaying hazard evaluation 15
10. Comparison of separate scoring exercises 20
11. Revised format for displaying effects 22
12. Revised format for displaying hazard evaluation 23
13. Format for displaying environmental exposure 26
14. Phase-one scoring format for displaying effects 27
15. Toxicity multipliers of environmental exposure scores 29
16. Toxicity multipliers determined by scoring of test
chemicals 31
17. Environmental exposure scores of test chemicals 32
18. Integration of toxicity multipliers with environmental
exposure scores 33
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PREFACE
This report is a product of the Health and Environmental Studies
Program (HESP) of the Information Center Complex (ICC), Information
Division, Oak Ridge National Laboratory (ORNL). It was prepared for the
Assessment Division, Office of Toxic Substances, U.S. Environmental
Protection Agency (EPA).
Appreciation is extended to Tim Ensminger, HESP manager, and Helga
Gerstner, ICC manager, for their support during the preparation of this
report. The advice and support of Justine Welch, EPA project officer
and cocompiler, are gratefully acknowledged. Thanks are also given to
Pat Hartman, typist, and Sherry Hawthorne, editor, of the ICC Publica-
tions Office, for preparing the manuscript for publication. Special
appreciation is given to the workshop participants for their ideas and
comments from which this report was prepared.
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ABSTRACT
The environmental scoring of chemicals is viewed by the U.S. Envi-
ronmental Protection Agency as a tool to assist in the ranking or order-
ing of the universe of chemicals that are under the jurisdiction of the
Toxic Substances Control Act. The purpose of scoring is to identify
most of the chemicals that have a high probability for requiring review
for regulation or testing. This report describes a three-day workshop
held in Washington, D.C., August 13-15, 1979, to develop an environmental
scoring system. Initial discussions centered on the determination of a
safety factor (calculated as the concentration at which an effect is
observed divided by environmental concentration) that would allow a
numerical score to be assigned to a chemical to reflect its potential
hazard. Further discussion, however, indicated that the environmental
concentration of a chemical is usually not available and that the esti-
mation of an environmental concentration is not readily accomplished;
therefore, a scoring system was developed that does not require environ-
mental concentrations. This system relates environmental exposure to
toxicity by using a multiplier (3*, 2x, or lx) which is assigned on the
basis of the concentration at which an effect is observed. The applica-
bility of the scoring system is demonstrated by scoring selected chemicals.
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1. INTRODUCTION
The Toxic Substances Control Act (TSCA) mandates the U.S. Environ-
mental Protection Agency (EPA) to control substances that are harmful to
human health or the environment. In addition, it enables the agency to
require testing on existing poorly characterized chemicals that may pre-
sent unreasonable risks to human health or the environment or that have
significant production volume, human exposure, or environmental release.
The Interagency Testing Committee (ITC) was established by TSCA and
instructed to recommend to EPA a list of priority chemicals that should
be considered for testing.
The EPA and ITC require a system to assist them in ranking or order-
ing the universe of TSCA chemicals so that chemicals with the greatest
need for control and testing are identified and reviewed first. Scoring
is viewed as a tool to assist in the ordering at an early stage in the
assessment process. As such, scoring serves to identify chemicals that
should receive additional scientific review; it should not be used to
make ultimate regulatory decisions.
Because scoring is a screening tool, it assumes some compromise be-
tween completeness and speed. The accuracy of the ranking depends on
having a complete data base, yet investment of elaborate resources in
this area defeats its purpose as a screen. The necessary simplicity of
scoring acknowledges that some chemicals will slip through the screen,
and additional scientific judgment is needed to add those problem chemi-
cals that the scoring system could not accommodate. The purpose of
scoring is to identify most of the chemicals that have a high probability
of requiring review for regulation or testing.
The Assessment Division of EPA is that part of the Office of Toxic
Substances responsible for the first phases of evaluating chemicals
under TSCA, including their selection. It shares ITC's need for a sys-
tem to rank TSCA chemicals requiring testing, but the system used by the
Assessment Division should also select chemicals possibly needing control.
To some extent the current ITC system, which uses positive scores to de-
note documented hazards and negative scores to denote suspected hazards,
can accommodate both goals.
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Shortly after it was formed ITC developed a scoring system to rank
chemicals in order of their need for testing (Federal Register, 1977).
Chemicals from a variety of source lists received exposure scores and
biological effects scores that covered seven subfactors dealing with
human health and ecological concerns. Recognizing a need for an evalua-
tion of the system, ITC conducted a workshop in February 1979 in San
Antonio, Texas, to examine the scoring method of each of the subfactors,
to assess the means used for weighing and combining the scores, and to
recommend revisions, if needed.
The environmental scoring system that took shape at the February
1979 ITC workshop consisted of three segments: environmental (biotic)
effects, environmental fate, and ecosystem effects. Due to lack of time
in February, certain elements of the scoring system were not completed,
and the three segments were not integrated.
Sharing a common need to examine the environmental scoring system
and similar logic and information needs in this area, the Assessment
Division and ITC cooperated to complete the environmental effects scor-
ing system. The Assessment Division with the support of ITC sponsored
a workshop August 13-15, 1979 to integrate the components developed at
the ITC February 1979 workshop and to test the scoring system on several
chemicals (listed in Table 1). The Health and Environmental Studies
Program of the Oak Ridge National Laboratory, through an interagency
agreement, arranged the workshop and supplied dossiers on the chemicals
in Table 1 for use by workshop participants (see Appendix). Information
in the dossiers was the primary data source for the scoring exercises.
This report of the proceedings of the August 1979 workshop includes
an explanation of the scoring system and how it might be used by those
persons responsible for developing a priority ranking of chemicals need-
ing further assessment for possible testing or control. To understand
the full development of the system, the reader is directed to the orig-
inal ITC scoring system (Federal Register, 1977) and the report from the
ITC workshop held in February 1979 (TSCA-ITC Workshop, 1979).
Two major points stressed by participants throughout the workshop
were the necessity of having at least a minimal amount of data on a
chemical before scoring could occur and the necessity that a scoring
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Table 1. Chemicals used
to test scoring system
Ammonia
Chlordane
Diethyl hexylphthalate
Hexachlorocyclopentadiene
Leptophos
Linear alkyl sulfonate
Nitrilotriacetic acid
Quinaldine
Tetraethyllead
2,4-Xylenol
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system be relatively simple. The evolution of the scoring system as
described in this report reflects these two concerns.
2. SAN ANTONIO ENVIRONMENTAL SUBGROUP SUMMARY
At the San Antonio Workshop in February 1979, the environmental
subgroups on toxicology (E..) and fate and chemistry (E~) developed
separate scoring systems, and the third environmental subgroup (£)
identified areas of consideration for scoring ecosystem effects. (This
third subgroup concluded its task at a June 13, 1979 meeting in Washing-
ton, D.C.) Figure 1 shows the E.. matrix which, when completed using the
criteria for scoring environmental toxicity in Table 2 and the criteria
for scoring bioaccumulation in Table 3, permits a hazard value to be de-
rived by totaling the numbers in the matrix. In many cases both nega-
tive and positive numbers will appear in the table and should be added
separately to give a negative total and a positive total. The negative
number indicates that data exist which suggest a possible hazard, where-
as the positive number indicates a documented hazard.
Tables 4 and 5 show the scoring system criteria selected by the
fate and chemistry subgroup. Final scores are reached by adding the
negative (suspected hazards) and positive (documented hazards) scores
separately. It should be noted that both the toxicology subgroup and
the fate and chemistry subgroup used the parameter of bioaccumulation,
and both also require either estimated or measured environmental concen-
trations to arrive at a final score. (Subgroup E.. used estimated con-
centrations; subgroup E~ used measured concentrations.)
Areas of consideration identified by the ecosystem effects subgroup
(E») are given in Table 6. The scoring rules for these parameters are
too detailed for complete presentation in this report but can be found
in the reported proceedings of the San Antonio Workshop (TSCA-ITC Work-
shop, 1979).
3. INTEGRATION OF SCORING SYSTEMS OF ENVIRONMENTAL SUBGROUPS
The charge for the first day of the August 1979 workshop was to
integrate the individual scoring systems developed by the three subgroups
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ORNL-DWG 80-9048
LETHALITY
GROWTH/DEVELOPMENT
REPRODUCTION
BIOACCUMULATION
OTHER TOXICOLOGICAL
EFFECTS
MICROBES,
ALGAE,
PLANTS
INVERTEBRATES
FISH
BIROS,
MAMMALS
Fig. 1. Toxicity matrix for proposed scoring system.
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Table 2. Scoring system for environmental toxicity
Score Criterion
h c
+3 Known ECSO less than the EEC
+2 Known EC50 between the EEC and 10 times the EEC
+1 Known EC50 between 10 and 100 times the EEC
0 Known EC50 greater than 100 times the EEC
-1 Estimated EC50 greater than 10 times the EEC
-2 Estimated ECSO between 1 and 10 times the EEC
-3 Estimated ECSO less than the EEC
Does not include bioaccumulation, which is given
in Table 3.
^The numerals designating the scores are not an
arithmetical series of integers: +3 and -3 both desig-
nate levels of greatest effect.
iEEC = estimated environmental concentration.
Estimated values will be based on structure/activity
relationships or data on related organisms.
Source: TSCA-ITC Workshop, 1979, Table 1, p. 48.
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Table 3. Scoring system for
bioaccumulation in aquatic species
Score Criterion
+3 Measured BCFa greater than 10,000
+2 Measured BCF between 1,000 and 10,000
+1 Measured BCF between 100 and 1,000
0 Estimated BCF less than 100
-1 Estimated BCF between 100 and 1,000
-2 Estimated BCF between 1,000 and 10,000
-3 Estimated BCF greater than 10,000
BCF = bioconcentration factor, which
is the concentration in tissue or animal
divided by the concentration in water.
^Estimate based on the n-octanol/water
partition coefficient.
Source: TSCA-ITC Workshop, 1979,
Table 2, p. 48.
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Table 4. Scoring system for persistence, bioaccumulation
potential, and mobility
Score
+3
+2
+1
0
-1
-2
Persistence
Infinite
Up to 1 year
1 to 8 weeks
Up to 1 week
Suspected low;
no data
Suspected high;
no data
Bioaccumulation
potential
High
Appreciable
Low
Negligible
Suspected low;
no data
Suspected high;
no data
Mobility
High
Medium
Low
Negligible
Suspected low;
no data
Suspected high;
no data
Based on the n-octanol/water partition coefficient
Source: TSCA-ITC Workshop, 1979, Table A, p. 60.
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Table 5. Scoring system for environmental concentration
Environmental Concentration
Score
+3
+2
+1
0
-1
-2
Soil
10 ppm
1 to 10 ppm
0.1 to 1 ppm
<0. 1 ppm
Suspected low;
no data
Suspected high;
no data
Water
1 ppm
0.1 to 1 ppm
0.01 to 0.1 ppm
<0.01 ppm
Suspected low;
no data
Suspected high;
no data
Air
1,000 ng/m3
100 to 1,000 ng/m3
10 to 100 ng/m3
<10 ng/m3
Suspected low;
no data
Suspected high;
no data
Source: TSCA-ITC Workshop, 1979, Table 5, p. 60.
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10
Table 6. Ecosystem components
of scoring system
Primary production
Secondary production
Population changes
Nutrient cycles
Ecosystem structure and function
Diversity/simplicity
Endangered species and habitat
Source: Adapted from TSCA-
ITC Workshop, 1979, Figure 1,
p. 65.
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11
(E-. , E_, and E_) so that areas of overlap and omissions were resolved
and the three operated well together. This integrated or combined scor-
ing system could be used to develop a priority ranking of chemicals; the
chemicals receiving high scores in the ranking were those that would
receive additional review to determine what, if any, testing or control
is necessary.
By the close of the first day's session, an integrated system was
developed that the participants considered a starting point for assess-
ing the chemicals listed in Table 1, realizing, however, that modifica-
tions would be made as a result of tests of the scoring system performed
during the workshop. Tables 7, 8, and 9 show the components of the
integrated system. The table for displaying exposure and fate (Table 7)
is somewhat similar to Tables 4 and 5, which were developed at the San
Antonio Workshop, in that all three tables consider essentially the same
parameters of release rate, redistribution potential, and degradation.
The release rate can be defined as the combined amount of a chemical
released to a given medium (note in Table 7 the exclusion of sediment
and biota; chemicals enter these compartments either through the soil,
air, or water) from manufacture, use, and disposal. The values for
release rates are expressed in Ibs/yr and are entered for the appropri-
ate medium in Table 7.
The redistribution potential indicates the likelihood that a chemi-
cal that has entered the environment through one medium (air, water, or
soil) will be distributed to one or both of the other two or to the
sediment and biota. As indicated in Table 7, the redistribution poten-
tial in any compartment is primarily a function of its physical proper-
ties. The important parameters that determine the redistribution of a
chemical in the environment are the air/water distribution coefficient,
the water/soil distribution coefficient, and the water/biota distribution
coefficient.
The air/water distribution coefficient (B ) may be determined either
by direct measurement,
_ concentration in air (mg/liter)
c concentration in water (mg/liter) '
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or by appropriate treatment (see MacKay, Shiu, and Sutherland, 1979) of
vapor pressure and water solubility data with special attention to the
applicability of Henry's law and Raoult's law.
The water/soil distribution coefficient can be either measured
directly or estimated from information on water solubility or the
octanol/water partition coefficient. For organic compounds a good cor-
relation has been found empirically to exist between the octanol/water
partition coefficient (K ) and K , where
ow oc
K
K = - °. .. - x 100
oc % organxc carbon in soil
(Karickhoff, Brown, and Scott, 1979) and K, is the measured soil adsorp-
tion coefficient:
v - mg chemical/kg soil
d mg chemical/liter water
Since there is a good correlation between K and K (0.98 for the
O \v OC
organic compounds studied by Karickhoff and coworkers), reasonable esti-
mates of K can be made from K if the calculations for K cannot be
oc ow oc
performed (Karickhoff, Brown, and Scott, 1979).
The water/biota distribution coefficient (bioconcentration factor,
or BCF) can be measured directly or estimated with the use of appropriate
egression equations from water solubility or the octanol/water parti-
Ion coefficient (K ). The appropriate regression equations are:
log BCF =0.76 log K - 0.23
ow
aquatic organisms that contain approximately 8% lipids (Veith et al.
by Federal Register, 1979) and
log K = 5.00 - (0.670 log S) ,
ow
,s
aqueous solubility in umol/liter (Chiou et al., 1977)
-------
17
Chemicals released to the environment will accumulate somewhere un-
less they degrade and lose their chemical identity. Degradation routes
are highly specific for each chemical, but certain generalizations can
be made in terms of media:
1. Air
For organic chemicals, atmospheric degradation may depend on direct
photolysis (adsorption of light followed by decomposition) or secondary
reactions (attack by reactive atmospheric components: OH radical, ozone,
oxygen atoms, etc.)- Of these, degradation by OH radical attack appears
to be the most prevalent (Pitts et al., 1978). Attack by OH can be
measured directly in the laboratory or estimated by structure/activity
relationships. In general, any organic molecule with C-H bonds or C=C
bonds will be subject to degradation by OH radical attack (hydrogen sub-
traction or addition to the double bond). Alternatively, the photo-
degradation of chemicals can be studied in smog chamber type studies
using artificial light. In any event, the desired outcome is an estima-
tion of the lifetime of the chemical in the atmospheric environment,
expressed in terms of half-life, t%.
2. Water
Chemicals may degrade in water via a variety of mechanisms, the
most prevalent of which are hydrolysis and biodegradation. Aqueous
photodegradation is also important for some chemicals. A variety of
measurement techniques are used to obtain an estimation of the lifetime
of a chemical in water, expressed as t%. It is to be noted that removal
from water by other mechanisms (such as volatilization, adsorption, and
bioaccumulation) was considered as redistribution.
3. Soil
Degradation of organic compounds in soil is usually via biodegrada-
tion. Direct measurement techniques, often involving li|C-labeled com-
pounds, may be used. Further, biodegradation rates in aqueous systems
-------
18
are often used as estimates of degradation rates in soil. The desired
output is an expression of the lifetime of a chemical in soil. Mobility
of the chemical in soils, e.g., soil adsorption, is considered in the
discussion of redistribution potential.
The principal reason for inclusion of data on release rate, redis-
tribution potential, and degradation potential in Table 7 is to estimate
environmental concentrations. Two approaches to estimating environmental
concentrations are mathematical modeling and benchmark chemicals. With
each approach, the data on release rate, redistribution potential, and
degradation are used, but in somewhat different ways. The mathematical
model fits existing data to the equations and derives the environmental
concentration. The benchmark chemical approach, however, compares exist-
ing data on the environmental parameters of a chemical under study with
a reference chemical whose environmental parameters and concentrations
are known; such comparisons allow estimates of concentration based on
the similarity of the environmental parameters of the chemical under
consideration and the reference (benchmark) chemical. A more powerful
approach is to combine the mathematical model and the benchmark chemical
method. The mathematical model is used to predict the environmental
concentrations of both the benchmark chemical and the chemical under
study. Output from the model then allows a more realistic extrapolation
of the environmental concentration of the benchmark chemical to the con-
centration expected for the new compound. If a measured concentration
is known, however, there is no need for an estimation. Importance is
placed on the environmental (exposure) concentration because it is the
denominator in the equation used to assign scores to biotic effects:
lowest effect concentration ,. ,.
: = safety factor.
exposure concentration
The lowest effect concentration (i.e., lowest concentration in which an
effect is observed) is entered into Table 8. This table is essentially
a compilation of Fig. 1 (toxicity matrix) and Table 6 (ecosystem pro-
cesses) with the addition of the abiotic column. Upon completion of
Table 7 the exposure concentration is available.
-------
19
After Tables 7 and 8 are completed, the safety factor is determined,
as indicated in the above equation, by dividing the lowest effect concen-
tration by the appropriate estimated or measured exposure concentration
(e.g., effect concentration in fish is divided by concentration in water).
This value is compared with the scoring criteria in Table 3 to obtain a
numerical value, which is placed appropriately in Table 9 to show hazard
evaluation. If more than one exposure concentration is available for a
given medium, then the choice of which one to use as the denominator in
calculating the safety factor depends on whether the worst case or best
case is to be reflected. The lower the exposure concentration, the
greater the safety factor, and the greater the exposure concentration,
the lower the safety factor. After Table 9 is completed, the scores can
be totaled and compared with other chemical hazard evaluation scores for
priority ranking. It should be emphasized that the information entered
into Tables 7 and 8 is raw data and values entered into Table 9 are
numerical data based on comparisons of the safety factor with the criteria
in Table 3.
4. TESTING AND MODIFICATION OF THE INTEGRATED SYSTEM
On the second day of the conference, the participants met to identify
problems in the use of the integrated system (Tables 7, 8, and 9) and to
determine the consistency of the scores from two independent groups. Par-
ticipants were divided into two groups, each having access to basically
the same information (chemical dossiers), and asked to score the same
four compounds (leptophos, chlordane, diethylhexylphthalate, and nitrilo-
triacetic acid) using the scoring system as presented in Tables 7, 8, and
9.
After both groups had scored the compounds, they reconvened and com-
pared their scores (Table 10). It was soon evident that discrepancies
existed, especially with the scores for chlordane and leptophos. During
the ensuing discussion several reasons for these discrepancies became
clear. Group one had added bioaccumulation to Table 9 and, when a bio-
accumulation factor was reported, compared it with the range of values in
Table 3 to obtain a value for Table 9; group two did not use bioaccumula-
tion. Another discrepancy was that group one did not use negative numbers
-------
20
Table 10. Comparison of separate
scoring exercises
Group 1 Group 2
Chlordane +19, -6 +12, -8
Leptophos +8 0, -24
Nitrilotriacetic acid 0 0, -1
Diethyl hexylphthalate +8, -3 +8, -6
-------
21
(representing estimated or suspected hazards) to the extent that group two
did; instead, group one left most of the entries blank when there were in-
sufficient data. After some discussion, the scoring system was adapted as
follows to resolve these discrepancies.
1. Bioaccumulation was included on the hazard evaluation matrix.
2. Simulated ecosystem data were omitted from the hazard evaluation
matrix because of the difficulty of interpretation of data and
the inability to incorporate these data into the ecosystem com-
ponent as indicators or predictors.
3. The birds and mammals category was split so that bird data and
mammal data could be considered separately. This facilitates the
use of mammal data generated for human health effects evaluation.
4. The lowest "no effect" value was used to derive the hazard evalua-
tion score in each long-term component (Tables 8 and 9). Where
"no effect" information is absent and for short-term effects, the
lowest concentration producing an effect should be used.
5. The subheadings under ecosystem processes were omitted. They were
not used during the scoring exercises because there were no avail-
able data.
6. For given environmental exposure concentrations, the use of the
lowest detected value will result in the largest (least conservative)
safety factor, whereas the use of the greatest detected value will
result in the smallest (most conservative) safety factor.
7. In categories where effect and "no effect" data are absent, no
score should be assigned. A score should be assigned only when
the data exist or can be extrapolated from another category or a
similar chemical.
As a result of the changes noted in points 1, 2, 3, and 5, Tables 8 and
9 were modified as shown in Tables 11 and 12, respectively. The second
day closed with a brief discussion that emphasized the importance of the
estimated environmental concentration since most chemicals do not have
adequate monitoring data and therefore no measured environmental
concentrations.
-------
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The final day of the workshop began with a continuation of the pre-
vious afternoon's discussion concerning the estimation of the environ-
mental concentration. A presentation was given which outlined the
parameters involved in predicting an environmental concentration (Fig. 2)
and demonstrated the complexity of making such predictions; for many
chemicals much of the needed information is unavailable and at present
not easily estimated.
After this presentation and a reminder that the proposed scoring
system was to serve as a screen and not as a substitute for risk assess-
ments, the requirement of having the environmental concentration was
eliminated. It was agreed that using measured or estimated environmental
concentrations was highly desirable but such a constraint would drastically
limit the number of chemicals that could be screened. Efforts were then
made to design a scoring system that could make use of exposure indicators
without requiring estimated or measured concentrations. Consequently, a
major modification occurred in the existing scoring system as it appears
in Tables 7, 11, and 12. Table 7 was altered to the Table 13 format,
with the most significant change being the omission of environmental
concentrations. At one point the mobility and persistence scores in
Table 13 were additive; however, trial chemical scoring indicated that
in some cases the spread in scores between two compounds whose mobility
and persistence were greatly different was not as significant as when
the scores were multiplied. For example, compound A has a mobility score
of 2 and a persistence score of 2, and compound B has a mobility score of
4 and a persistence score of 4; by addition, compound A has a combined
mobility and persistence score of 4 and compound B a score of 8, whereas
by multiplying the scores, compound A still has a score of 4 but compound
B has a score of 16. The workshop participants decided that the increased
range of scores obtained by multiplying persistence and mobility scores
was preferable.
Since simplicity was one of the desired attributes of the scoring
system, the essential categories from Table 11 were condensed, as shown
in Table 14. With the elimination of the requirement for environmental
concentrations, the safety factor (calculated as the effect concentration
divided by the environmental concentration) could not be used; therefore,
-------
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Table 13. Format for displaying environmental exposure
Release volume (Ibs/year) 108 10s 10*
Score 3a 2 1
Release distribution Global National Local
Score 321
Mobility Persistence
score score
Soil
Air
Water
Bioaccumulation0 P >105 P = 500-10* P = 1-500 P <1
Score 4 3 21=
Total score =
lumbers are potential points for subfactors of the environmental exposure score.
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pected data). However, values are added as absolutes.
^Scored on a scale of 1 to 4. For mobility 4 = easily dispersed among three media,
3 = easily dispersed between two media, 2 = easily dispersed through one medium, and 1 =
negligible dispersal. For persistence 4 = infinite, 3 = up to 1 yr, 2 = 1 to 8 wk, and
1 = up to 1 wk. Scores may be negative, indicating suspected mobility or persistence;
however, values are multiplied as absolutes.
P represents the octanol/water partition coefficient.
-------
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the hazard evaluation table (Table 12), which depended upon the safety
factor for its values, was also eliminated. Also pertinent to the eli-
mination of Table 12 is the fact that a hazard evaluation of a chemical
is really not necessary for this first phase, or initial ranking of
chemicals for further review. From this point on, the scoring system
was viewed as having two phases; the first phase would consist of a
priority ranking of chemicals to be considered for further review and
as such would not require environmental concentrations. Phase two would
be a hazard evaluation of the highest priority chemicals as identified
in phase one and would require environmental concentrations.
Since the use of the safety factor was not needed for this first
phase, a new way to relate environmental exposure and toxicity had to be
developed. After some discussion a set of threshold levels of concern
was developed (Table 15) that could be used to complete Table 14 and as
multipliers (3*, 2x, or lx) of the environmental exposure scores from
Table 13. When using the information in Table 15 one should use the
lowest effect concentration from a given set of raw data on the toxic
effects of a compound if the greatest potential toxicity of a chemical
is to be represented. This is because the lower the effect concentra-
tion the higher the multiplier (see Table 15). Also, when the multi-
pliers from Table 14 are applied to the environmental exposure scores
that result from completing Table 13, the choice of terrestrial values
(plants, birds, or mammals) to be used as a multiplier of the soil mobil-
ity and persistence score and the choice of aquatic values (microbes,
plants, invertebrates, or fish) to be used as a multiplier of the water
mobility and persistence score are somewhat arbitrary. The only consid-
eration is that for a given set of terrestrial and aquatic multipliers,
the smaller the multiplier used, the smaller the final score for that
chemical. If one wishes to present the worst case situation then the
largest multiplier should be used. In the following section, in which
the scoring system is tested, the mean toxicity multiplier is used.
There is no direct multiplier for the air mobility and persistence score;
however, the biological effects of a chemical are in many cases the
result of atmospheric transport to the terrestrial or aquatic media.
-------
29
Table 15. Toxicity multipliers of environmental exposure scores
Terrestrial species
(mg/kg)
Acute0 <50
Aquatic species Other
(mg/liter) (ppm)
<1 <50 (water)
<5 (air)
<500 (soil)
Multiplier
3x
3x
>50 <1,500
>1,500
<100 >50 <1,000 (water)
>5 <100 (air) 2*
>500 <10,000 (soil)
>100 >1,000 (water)
>100 (air) lx
>10,000 (soil)
Chronic
a
<500
>500
<0.01 <50 (water)
<5 (air) 3x
<500 (soil)
>0.01 <0.5 >50 <1,000 (water)
>5 <100 (air) 2x
>500 <10,000 (soil)
>0.5 >1,000 (water)
>100 (air) lx
>10,000 (soil)
Values for acute toxicity are either LD50s, LCsos, or GRsos (50% growth
reduction), depending on the particular organism. Values for chronic toxicity are
concentrations at which an effect is observed. Terrestrial chronic values represent
concentrations in diets.
^"Bacteria and plants.
-------
30
The terrestrial and aquatic multipliers thus indirectly influence the
final toxicity rating of those chemicals whose release is primarily to
the atmosphere.
5. TESTING THE MODIFIED SCORING SYSTEM
Adhering to the criteria in Tables 13 and 15, ammonia, linear alkyl
sulfonate, 2,4-xylenol, tetraethyllead, quinaldine, and hexachlorocyclo-
pentadiene were scored by using information provided in the chemical
dossiers. Table 16 shows the multipliers that were determined, and
Table 17 gives the fate and chemistry (environmental exposure) scores
for these chemicals. It should be noted that the blanks in Table 16
(indicating no data) are to be expected; they do not serve as indicators
of areas that should be examined for testing. The final table (Table 18)
shows the integration of the toxicity multipliers from Table 13 with the
environmental exposure scores from Table 15 and gives the final scores;
the mean terrestrial and aquatic multipliers from Table 16 were applied,
respectively, to the soil and to the water scores in Table 17. A rank-
ing of the chemicals in Table 17 (nonintegrated data) according to de-
creasing environmental exposure, scores gives tetraethyllead = hexachloro-
cyclopentadiene > quinaldine > ammonia > linear alkyl sulfonate > 2,4-
xylenol. After integration of the toxicity multiplicity factors (Table
18), the order then becomes hexachlorocyclopentadiene > tetraethyllead >
quinaldine > ammonia > 2,4-xylenol > linear alkyl sulfonate. Thus, the
order changes, but not significantly. This is especially apparent when
the integrated scores of those compounds that decided the changes in the
ranking are examined (Table 18); the scores for linear alkyl sulfonate
and 2,4-xylenol are very similar, as are the scores for tetraethyllead
and hexachlorocyclopentadiene.
6. DISCUSSION AND CONCLUSIONS
Some of the more significant discussions by the workshop partici-
pants concerned the following.
1. What is the minimum data set required for scoring as well as the
expertise (types of disciplines) necessary for scoring?
-------
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34
2. Is the scoring exercise a team or an individual effort?
3. How much time is required to effectively score a chemical?
4. What are the drawbacks of the scoring system?
One of the assets of the phase-one scoring system is that a chemical
can be scored with only minimal information. Ideally, the completion of
all parameters in Tables 13 and 14 is desired; however, a score can be
obtained even if some information is not available, as is demonstrated
with the six examples in Table 16. Essential to the phase-two (hazard
evaluation) scoring system, in addition to biological effects data, is
the environmental concentration. The discussion of the scarcity of com-
pounds with measured environmental concentrations and the difficulty in
estimating these concentrations emphasized the importance of the phase-
one scoring system. The phase-one system can distinguish chemicals that
need additional assessment from those that do not; the need for environ-
mental concentrations (measured or estimated) can then be placed as high
priority for those compounds selected for further assessment.
The participants thought that a team approach was probably needed
to score chemicals because of the breadth of disciplines involved and
the necessity of combining separate fate and effect scores. In addition,
the lack of pertinent data for many chemicals necessitates sound scientif-
ic judgment, and therefore the final score for a chemical should reflect
a concensus of scientific opinion. Regardless of how many people are
involved in the scoring exercise, the workshop participants felt, approxi-
mately 15 minutes would be necessary to effectively score one chemical,
although the rate of scoring would be directly related to individual
scoring experience.
Some possible drawbacks to the system that were mentioned include
(1) the lack of systematic identification of specific data gaps, (2) the
lack of identification of potential degradation products or metabolites,
and (3) the failure to make judgments concerning the quality of the data.
In addition, the use of any systematic chemical screening process involves
some degree of error. Professional judgment should be exercised to elimi-
nate as much of the error as possible.
In conclusion, the final scoring system, as presented in Tables 13,
14, and 15 and demonstrated in Tables 16, 17, and 18, is relatively
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35
simple and requires minimal information needs. In addition, the system
is recognized as a first cut or first phase approach, the primary pur-
pose of which is to provide a heirarchy of chemicals for consideration
for additional assessment. As such it is not a substitute for a hazard
evaluation scheme, which is considered a phase-two assessment.
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36
APPENDIX
Participants
Ken Dickson
Institute of Applied Sciences
Denton, Texas
Tim Ensminger
Oak Ridge National Laboratory
Oak Ridge, Tennessee
Jim Gillett
U.S. Environmental Protection Agency
Corvallis, Oregon
Judy Hushon
MITRE Corporation
McLean, Virginia
Richard Kimerle
Monsanto Company
St. Louis, Missouri
Bob Moolenaar
DOW Chemical
Midland, Michigan
Rod Parrish
EG&G, Bionomics Marine Research
Laboratory
Pensacola, Florida
Walt Rosen
U.S. Environmental Protection Agency
Washington, D.C.
Bob Ross
Oak Ridge National Laboratory
Oak Ridge, Tennessee
Phil Schneider
Dupont Corporation
Newark, Delaware
Art Stern
U.S. Environmental Protection Agency
Washington, D.C.
Richard Tucker
Enviro Control, Inc.
Rockville, Maryland
Richard K. Tucker
U.S. Environmental Protection Agency
Washington, D.C.
Chuck Walker
U.S. Fish and Wildlife Service
Washington, D.C.
Justine Welch
U.S. Environmental Protection Agency
Washington, D.C.
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37
REFERENCES
1. Chiou, C. T., V. H. Freed, D. W. Schmedding, and R. L. Kohnert.
1977. Partition Coefficient and Bioaccumulation of Selected
Organic Chemicals. Environ. Sci. Technol. 11(5):475-478.
2. Federal Register. 1977. 42(197) :55026.
3. Federal Register. 1979. 42(52) :15973.
4. Karickhoff, S. W. , D. S. Brown, and T. A. Scott. 1979. Sorption
of Hydrophobic Pollutants on Natural Sediments. Water Res. 13:
241-248.
5. MacKay, D., W. Y. Shiu, and R. P. Sutherland. 1979. Determination
of Air-Water Henry's Law Constants for Hydrophobic Pollutants.
Environ Sci. Technol. 13(3):333-337.
6. Pitts, J. N., Jr., A. M. Winer, G. J. Doyle, and K. Darnall. 1978.
Reactivity Scale for Atmospheric Hydrocarbons Based on Reaction
with Hydroxy Radical. Environ. Sci. Technol. 12(1):100-102.
7. TSCA-ITC Workshop. 1979. Scoring Chemicals for Health and Ecolog-
ical Effects Testing. Enviro Control, Inc., Rockville, Maryland.
113 pp.
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38
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1 REPORT NO.
EPA-560/11-80-010
3. RECIPIENT'S ACCESSION-NO.
4 TITLE AND SUBTITLE
Proceedings of the EPA Workshop on the
Environmental Scoring of Chemicals
5. REPORT DATE
May 1980
6. PERFORMING ORGANIZATION CODE
7 AUTHOR(S)
Robert H. Ross anH Justine Welch
8. PERFORMING ORGANIZATION REPORT NO.
ORNL/EIS-158
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Health and Environmental Studies Program
Information Center Complex/Information Division
Oak Ridge National Laboratory
Oak Ridge, Tennessee 37830
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
78-D-X0453
12. SPONSORING AGENCY NAME AND ADDRESS
Assessment Division
Office of Toxic Substances
U.S. Environmental Protection Agency
Washington. D.C. 20460
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The environmental scoring of chemicals is viewed by the U.S. Environmental
Protection Agency as a tool to assist in the ranking or ordering of the universe
of chemicals that are under the jurisdiction of the Toxic Substances Control Act.
The purpose of scoring is to identify most of the chemicals that have a high prob-
ability for requiring review for regulation or testing. This report describes a
three-day workshop held in Washington, D.C., August 13-15, 1979, to develop an envi-
ronmental scoring system. Initial discussions centered on the determination of a
safety factor (calculated as the concentration at which an effect is observed divided
by environmental concentration) that would allow a numerical score to be assigned to
a chemical to reflect its potential hazard. Further discussion, however, indicated
that the environmental concentration of a chemical is usually not available and that
the estimation of an environmental concentration is not readily accomplished; there-
fore, a scoring system was developed that does not require environmental concentra-
tions. This system relates environmental exposure to toxicity by using a multiplier
(3X, 2x, or lx) which is assigned on the basis of the concentration at which an
effect is observed. The applicability of the scoring system is demonstrated by
scoring selected chemicals.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Scoring Systems
Workshop
Environmental Exposure
Environmental Toxicity
Environmental Effects
Scoring Systems
13 DISTRIBUTION STATEMENT
Unlimited Release
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
38
20 SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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