FATE. THE ENVIRONMENTAL FATE CONSTANTS
INFORMATION SYSTEM DATABASE
by
Heinz P. Kollig1
Karen J. Hararick1
Brenda E. Kitchens1
1 Environmental Research Laboratory
U.S. Environmental Protection Agency
Athens, CA 30613-0801
and
1 Computer Sciences Corporation
c/o Environmental Research Laboratory
U.S. Environmental Protection Agency
Athens, GA 30613-0801
ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
ATHENS, GA 30613-0801
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DISCLAIMER
The informaCion in this document has been funded wholly or in pare by the
United States Environmental Protection Agency. It has been subject to the
Agency's peer and administrative review, and it has been approved for
publication as an EPA document. Mention of trade names or commercial products
does not constitute endorsement or recommendation for use by the U.S.
Environmental Protection Agency.
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FOREWORD
As environmental controls become more costly to implement and the
penalties of Judgement errors become more severe, environmental quality
management requires more efficient analytical tools based on greater knowledge
of the environmental phenomena to be managed. As part of this Laboratory's
research on the occurrence, movement, transformation, impact, and control of
environmental contaminants, the Measurements Branch provides physical,
chemical, and microbial rate and equilibrium constants for use in mathematical
models of pollutant behavior.
Assessment of potential risk posed to humans by man-made chemicals in the
environment requires the prediction of environmental concentrations of those
chemicals under various scenarios. Models and other risk assessment
techniques frequently require the use of physical and chemical process data to
estimate the transport and transformation of specific chemicals. To meet this
data need, an online database, called FATE, has been developed to provide the
user with reliable and environmentally realistic fate constants.
Rosemarie C. Russo, Ph.D.
Director
Environmental Research Laboratory
Athens, Georgia
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ABSTRACT
A new online database, designated Che FATE database, has been developed
for the interactive retrieval of kinetic and equilibrium constants that are
needed for assessing the fate of chemicals in the environment. The database
contains values for twelve parameters, but may not contain a value for each
/}*l«j
parameter for each chemical. As of Jxner 1991, the database contained values
for about 200 chemicals. Unique features of the database include experimental
data that are extracted only from primary references, and pertinent
experimental conditions that are entered into the database to assure the user
of the credibility and applicability of a value. A newly developed computer
program is used to extrapolate hydrolysis rate constants to a standard format.
Acidic, basic and neutral contributions are combined to calculate che overall
hydrolysis rate constant, k*. and the half-life of the chemical at 25'C and pH
7. The data are also reported as second-order acidic and basic rates and a
first-order neutral rate at 25°C. Products of transformation are listed for
degradation processes when available. A newly developed computerized expert
system will be applied to compute accurate fate constant values. The expert
system has the capability of crossing chemical boundaries to cover all organic
compounds.
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TABLE OF CONTENTS
ABSTRACT iv
INTRODUCTION 1
PROBLEMS WITH CURRENTLY AVAILABLE DATA 3
Experimental Data 3
Estimated Data 7
THE DATABASE MANAGEMENT SYSTEM 9
FATE DATABASE ._ 10
Database Files 11
Fate Constants 11
Sources of Data 12
RATE Program 12
Methods of Data Retrieval 14
CAS number 14
SMILES notation 14
Molecular Formula 15
Preferred and Common Names 15
Reference Number 16
DATABASE MENU SYSTEM 17
Update of FATE 17
Data Retrieval from FATE 17
Screen to Report from CAS File 18
Screen to Report from REF File 18
Screen to Report from' FATES File 19
Sample Report 19
DISCUSSION and CONCLUSION 20
ACKNOWLEDGMENT 21
REFERENCES 22
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INTRODUCTION
Assessment of potential risk to human health and to the environment posed
by chemicals requires the prediction of environmental concentrations of those
chemicals under different scenarios. Risk assessment frequently requires the
use of physical and chemical process data to estimate the transport and
transformation of specific chemicals in the environment. This information is
subsequently used for regulating the allowable concentrations of specific
chemicals in .ground water wells, air emissions, hazardous waste sites, etc.
The need for specific rate and equilibrium constants for chemicals that
have potential environmental impact has grown in tandem with the production of
new chemicals by the chemical industry. Approximately 1600 new chemicals or
formulations are submitted to EPA's Office of Toxic Substances (OTS) each year
for premanufacturing review, and approximately 75,000 chemicals are potential
candidates for review under the OTS existing chemicals program. Relatively
few of the required fate constants have been .measured experimentally and
published, and many of the published fate constants are of questionable
reliability or applicability. Data being used for environmental and human
risk assessment for regulatory purposes must be of known reliability for the
assessment to have validity.
As laboratory instrumentation has improved and experimental procedures
have become more sophisticated, the environmental fate constants that have
been measured in the laboratory have become more reliable. However, no matter
what the objectives of the research, the experimental protocol, the sampling
procedures, and the chemical and statistical analyses of the data remain
critical aspects of the research and affect the reliability of fate
constants1. Therefore, literature values of fate constants vary, sometimes
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considerably*-1, and often several values are reported for the same chemical
parameter by different laboratories. Data evaluation systems have been
suggested1"' as a mechanism to assist the user in deciding which one of many
values might be the most reliable. However, the investigator who measured the
fate constant is the only one who can actually ensure the accuracy of the
data. The reliability of the fate constant can be evaluated by others only by
examining the research protocol and experimental conditions provided by the
author.
The inherent complexity in measuring physical and chemical properties,
especially those of hydrophobic chemicals, makes the measurement process a
difficult and, therefore, expensive one. Even if the prohibitively high costs
of the measurement processes could be ignored, the need for data will never be
completely satisfied through laboratory studies because of the time involved.
For these reasons, reliable computational techniques are needed to estimate
physical and chemical properties. Computational techniques will generate
values more rapidly at a fraction of measurement costs and will eventually
satisfy the need for much of the required data.
In this project, we developed an online database that provides the user
with reliable and environmentally realistic fate constants. We ensure the
quality of the data by: a) applying objective screening criteria to determine
whether a value should be entered into the database, and giving the user
pertinent experimental conditions, b) entering into the database literature
values from primary sources only, and c) entering into the database computed
values based on estimation techniques that use both fundamental chemical
structure theory and conventional techniques based on property-reactivity
correlations that are carefully screened for applicability before use.
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Potential users should write to Heinz P. Kollig, U.S. EPA, College Station
Road, Athens, GA, requesting a user's application form.
PROBLEMS WITH CURRENTLY AVAILABLE DATA
Experimental Data
Currently, computerized databases are being constructed to provide
experimental fate constant data that are more conveniently accessible to the
scientific community. As these databases have been compiled or used, it has
become obvious that data cannot simply be taken from the scientific literature
and used without extensive knowledge of the process under investigation and
the conditions under which the investigations were conducted4-7.
Many early experiments were conducted using investigative criteria that
were different from the stringent criteria needed for assessments today. For
example, some hydrolysis rate studies were conducted under uncontrolled or
undocumented hydrolytic conditions, using phrases such as 'distilled water' or
'room temperature', or conditions that could not be extrapolated to
environmental situations, such as with co-solvents. This criteria problem
results partially from the fact that most data-in the literature were obtained
without standard protocols and in mechanistic research where absolute and
precise fate constant values were not the major objectives of the research.
The result has been that much published data cannot be used to generate valid
environmental assessments without considerable mathematical manipulation, if
they can be used at all. Often, when the toxic chemical in question has been
in use for decades, reported aqueous solubility values, partition
coefficients, and other parameters will range over several orders of
magnitude1-'.
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In any reporting situation, there is always the chance that data were
miscalculated, transposed, published with less than (<), greater than (>),
positive (+) or negative (-) signs missing, decimal point placed incorrectly.
or any number of other problems resulting from repeated citation of other-
Chan-primary sources. For example, we needed the octanol/water partition
coefficient, K.,,, for acenaphthene, CAS number [83-32-9]. A quick search in a
secondary publication revealed a value of -2.02 for the log KO,, and included
the primary reference. Because of our knowledge of the KM values for
structurally similar compounds, we viewed the value of -2.02 as questionable.
When we obtained the primary source, it listed a value of 3.98 for the log
KO.. Clearly, without knowledge of the process, one might use a frequently
reported and cited value that is off by six orders of magnitude, demonstrating
the importance of obtaining values from primary sources.
Obtaining a primary publication can be a frustrating process, however.
The frustration involved in locating the primary reference is illustrated by
the following example. A value was needed for the water solubility of
2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD). A fate constant database showed
a value of 0.317 x 10'* rag/L and gave a 1984 reference notation with the
comment that the authors- obtained the value from a second author who published
in 1983. No journal was referenced for the second (1983) author. A search
with CAS ONLINE for the second author revealed no listing under the author's
name published in 1983. The referenced 1984 publication, in this instance,
showed two tables of properties for TCDO. Neither table gave the value that
appeared in the fate constant database (0.317 x 10° mg/L) for the water
solubility. The first table, Table A, gave a value of 0.2 x 10'* mg/L and
referenced an EPA treatise; the treatise, in turn, referenced the World Health
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Organization 1977 and a second source as Che suppliers of all data in Table A.
The treatise, however, did not differentiate between the two sources for
individual values. The second source identified the value found in Table A
(0.2 x 10~* mg/L) but referenced personal communication with workers at Dow
Chemical Company. We did not contact the Dow Chemical Company. Table B gave
a value of 7.91 x 10'4 rag/L for the water solubility of TCDD and referenced a
symposium held in Germany in 1985. Proceedings of the symposium were
published in 1986 and this reference revealed that the water solubility had
actually been determined experimentally. Figure 1 shows a flow diagram of
this search to provide a graphic understanding of the effort involved. The
paradox concerning this search was that the paper containing the information
extracted for Table B was published in 1984, but referenced a paper that was
presented in 1985 and published in 1986.
Figure 1. Flow of search for the primary source of TCDD
Database Search
0.317 x 10-1 mg/L
1984 Reference p 1983 Reference
Listed two Tables incomplete,
not obtainable
Table A Table B
0.2 x 10° mg/L 7.91 x 10'* mg/L
EPA Treatise 1985 Symposium
/ N 4
WHO Second Source Symposium
1977 0.2 x 10-' mg/L Proceedings 1986
i Primary Source
Pers. Comm.
Dow Chemical
Additionally, an inconsistent use of exponents and significant figures
gives the impression that the reported water solubility values, 0.2 x 10'' and
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7.91 x 10'*, are about three orders of magnitude apart. The difference, of
course, is only 25 times; nevertheless, the difference is significant. The
important question becomes, which value is correct? A third reference
corroborated the 7.91 x 10'* mg/L value from Table B. Because both values
were verifiable experimentally, the 7.91 x 10"' mg/L value was considered more
reliable. It is noteworthy to mention that corroborative information often is
not available and that adequate experimental, analytical or statistical
information is sometimes not provided by authors. Whatever the reason, if
information is missing, the value's assessed credibility decreases.
What can be said about the quality, accuracy, or applicability of data?
Consider the dilemma of an exposure or risk assessment modeler who is
confronted with the information provided in Table 1. Because these reported
values span several orders of magnitude, the range for the octanol/water
partition coefficient is 8.2 x 10* for p.p'-DDT and 1.6 x 10* for dieldrin and
each set of values has a standard deviation larger than the mean. A modeler
would prefer to be given one "best estimate" fate constant value for each
chemical because he may not have the resources available for determining which
value would be the best to use. Unfortunately, the accuracy of a reported
value cannot be fully evaluated. Accuracy depends on the skill and expertise
of the researcher, on the maintenance condition and precision of the
equipment, and on the repeatability of the experiment. The thoroughness of
the documentation of a report can be evaluated, however, and thus suggest the
confidence with which a reported value can be used*. Applicability can only
be determined by knowing the conditions under which the experiment was
conducted. If the value is to be used in an environmental risk assessment,
then the value must have been determined in a manner that permits
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extrapolation to environmentally realistic conditions for the assessment to
have validity.
Table 1. Experimental octanol/water partition
coefficients for p.p'-DDT and dieldrin
(literature survey)
Name
p.p'-DDT 9.5 x 10'
1.2 x 10'
8.2 x 10'
Dieldrin 1.2 x 10'
2.5 x 10»
1.6 x 10*
Estimated Data
Because of the high cost of laboratory measurement (estimated to be more
than $10,000 per parameter), there has been a recent trend toward estimating
fate constants'. In addition, the inherent complexity in measuring physical
and chemical properties, especially of hydrophobia chemicals, makes the
measurement process difficult. Even if the prohibitively high cost of the
measurement process could be ignored, there will always be a shortage of
experimental data because of time constraints. For these reasons,
computational techniques to estimate physical and chemical properties have
been developed. Computational property estimation techniques can generate
values at a small fraction of measurement costs, and it is likely that much of
the published data of the future will come from the application of these
methods.
The largest compilation of property estimation methods was made by Lyman
et al.10 Most of Lyman's methods are based on property-reactivity
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correlations and allow estimation of a number of constants, but relationships
often hold only within limited families of chemicals. If the estimation is
done for a chemical within a family for which a relationship was established,
the value can be very reliable. For a non-established relationship, however,
the estimated value can be off by one or more orders of magnitude. As stated
earlier, so can experimental values. Thus, a user evaluating data from
application of predictive techniques must fully appreciate the range and
limitations of the techniques themselves no matter how easy it is to generate
such estimates. It is noted that some of these estimation methods have been
fully automated11'" and only require the input of a CAS number for most
chemicals.
A promising new computational method for predicting chemical reactivity
is the computer expert system SPARC Performs Automated Reasoning in Chemistry
(SPARC)", being developed by scientists at ERL-Athens and the University of
Georgia. This system uses algorithms based on fundamental chemical structure
theory to estimate parameters and uses an approach that combines principles of
quantitative structure-activity relationships, linear free energy theory, and
perturbation theory from quantum chemistry. The goal for SPARC is to compute
a value that is as accurate as a value obtained experimentally for a fraction
of the cost required to measure it. Once established, the expert system
should be able to estimate environmental fate constants with remarkable
accuracy because the computation will be based on molecular theory with an
increasing database to "train" the system and refine its algorithms. This
contrasts with conventional estimation techniques that are based on
correlations or other relationships that have been shown to incorporate
inherent errors. Reliable experimental data with good documentation are still
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necessary, however, for further testing, training, and validation of SPARC.
THE DATABASE MANAGEMENT SYSTEM
A prototype of FATE was developed with d-BASE III Plus using a relational
file structure as a preliminary step in the analysis of system size and
database design requirements. The prototype contained the CAS number and
chemical name information of 2000 chemicals and a complete reference database
of 320 references. The objective of the analysis was to determine an
efficient file structure and programming language that could be used on the
VAX to develop the programs and menus necessary to manipulate the chemical
database files.
An evaluation was performed to determine the requirements of FATE by
defining the relationships of the data elements to one another, the required
field types and dimensions, the key fields that were necessary for indexing,
and the scope of the reporting and maintenance requirements.
A design specification for FATE was prepared by the Computer Sciences
Corporation, under EPA contract, without regard to specific hardware and
software implementation platforms. They determined that the design
specifications for data storage, interactive data entry, and data retrieval
were of a standard nature and that the database could be implemented with any
one of many fourth-generation database management systems. The recommendation
was that a fourth-generation language would be preferable to a third-
generation language for database development because of advantages in
development time, ease of enhancement, and ease of maintenance. It was
further recommended that FOCUS be used as the software to develop the chemical
database because FOCUS software was already installed on the Athens VAX and
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because FOCUS was currently the EPA standard database management system.
FOCUS is a fourth-generation language composed of several languages and
utilities that are used for specific operations on the data files. FOCUS
allows the use of scientific notation and the development of relational or
hierarchical files, and contains keyed indexes with pointers for the linkage
of the files.
The FOCUS-based FATE database is installed on the ERL-Athens VAX and
operates within the VMS (Virtual Memory System) operating system.
FATE DATABASE
Currently, FATE contains published fate data for approximately 200
chemicals obtained only from primary references plus selected fate constants
derived from computational techniques applied at ERL-Athens. It is hoped that
reliable data computed with SPARC will soon close the void of missing fate
data that exists today, at a fraction of the cost and time of obtaining the
values experimentally.
Database Files
The FATE database system consists of three data files. The CAS file
contains CAS numbers (Chemical Abstract Service), molecular formulae, SMILES
notations (Simplified Molecular Identification and Line Entry System)14'11, and
chemical and common names. The REF file contains reference numbers and
complete citations. The FATES file is cross-referenced to the other files and
contains the data for the fate parameters.
Five fields in the CAS file are indexed: CASNUMBER, CASFORMULA,
CASSMILES, CASNAME and CASCOMMON. The database can be searched for an entry
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in any one of the indexed fields.
Two fields in Che REF file are indexed: REFNUMBER and REFAUTHOR1. The
database can be searched for an entry in either one of the fields, or for one
of the secondary authors.
The FATES file is cross-referenced to the CAS and REF files, and can,
therefore, be searched for an entry by all of the indexed fields.
Fate Constants
The database contains fields for entry of the following twelve face
constants:
fate code symbol fate parameter
04 HO Henry's law constant
05 kh hydrolysis rate constant
06 pK. ionization constant
07 Ko. octanol/water partition coefficient
08 KOO organic carbon normalized
sediment/water partition coefficient
10 kd direct (aqueous) photolysis rate
constant
11 Kp sediment/water partition coefficienC
13 P. vapor pressure
14 S, water solubility
21 (x molar absorptivity
26 4>t aqueous photolysis reaction quantum
yield
27 k,,10 biodegradation rate constant
Sources of Data
The open literature is the source of primary references for the
experimental data included in the FATE database.
Face constant data for some of the twelve processes are estimated by our
staff with computational techniques, using che SMILES notation to define the
molecular structure of a chemical. We use the QSAR" (Quantitative Structure-
Activity Relationships) System and SPARC" (SPARC Performs Automated Reasoning
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in Chemistry) for estimating data.
The QSAR system contains estimation routines that have been modified from
the routines written by Lyman et al." It can be searched by CAS number or
SMILES notation and provides the estimated values in a table format.
The expert system SPARC uses computational algorithms based on
fundamental chemical structure theory and allows estimation of values for any
parameter that depends upon molecular structure. Unlike methods based on
property-reactivity correlations, this capability crosses chemical family
boundaries to cover all organic compounds. SPARC eventually will contain
estimation routines for most, if not all, of the twelve parameters that are
included in Che FATE database.
Rate Program
Measured hydrolysis data are analyzed Initially with RATE, a FORTRAN
program that was developed at ERL-Athens. RATE is used to extrapolate data to
a standard format.
The RATE program requires the entry of several first-order rate constants
over a range of pH values. Individual data points consist of three
parameters, the first-order rate constant, the temperature, and the pH at
which the rate was measured. The program uses the Arrhenius equation, a
standard temperature of 25°C and an assumed energy of activation of 20.000
cal/mol to transform the data and produce a plot of pH versus log k. The ploC
of the data is used to determine whether there ere acidic, basic or neutral
contributions to the rate constant. Superimposed on the plot are the lines of
slope - +1 and slope - -1. Data points that fall parallel to the line of
slope - -1 contribute to the acidic portion of the rate constant. Data points
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that fall parallel to the line of slope - +1 contribute to the basic portion
of the rate constant. Data points that are horizontal on the plot are neutral
to pH.
The transformation section of the program determines the data points that
will be included in the array to be analyzed as acid, base or neutral, and the
energy of activation that will be used for each analysis. If the data array
for each pH category contains first-order rate constants that have been
measured at different temperatures, a linear regression is used with the
Arrhenius plot to calculate a more accurate energy of activation. The data
are ultimately reported as second-order acidic and basic rates and a first-
order neutral rate at 25°C.
In the half-life section of the program, the acidic, basic and neutral
contributions are combined to calculate the overall hydrolysis rate constant,
k,,, and the half-life of the chemical at 25° C and pH 7.
Methods of Data Retrieval
Interactive users of the FATE database system can query the database by
CAS number, by SMILES notation, by molecular formula, by a substring of the
preferred chemical name, by a substring of the common names, by the REFerence
number, and by primary or secondary authors from the reference publications.
a) CAS Number
The most efficient method of data retrieval from the FATE database is by
entry of the CAS number. The CAS Registry number has no chemical
significance, and the numbers have been assigned in sequential order as
substances have been entered into the CAS Registry System for the first time.
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For this reason, CAS numbers provide unique identification of chemicals that
are independent of nomenclature. CAS numbers are separated by hyphens into
three groups in Che Registry System, but the FATE database has been designed
to contain numerical characters without hyphens. A CAS-checking algorithm is
incorporated in the code of the FOCUS program that allows the CAS file to be
updated. Whenever a new CAS number is entered in the database, it is verified
for validity with the CAS-checking algorithm.
b) SMILES Notation
Data may be retrieved from the FATE database by use of the SMILES
notation to define a chemical. SMILES notation is based on the principles of
molecular graph theory and is a chemical notation language specifically
designed for computer use by chemists14-li. SMILES notation provides unique
identification of a chemical substance based on a connection table thaC
represents the topological structure of the chemical. Therefore, the SMILES
notation does have chemical significance. Computer programs are available to
draw the chemical structure, based on the SMILES notation. In SMILES
notation, the hydrogen atoms are suppressed, aromatic atoms are represented by
lower case characters and non-aromatic atoms are represented by upper case
characters. The FATE database contains a subroutine that will translate
legitimate SMILES notation entered by the user on the data selection screen
into the unique code that has been stored in the database before the data
search is initiated.
c) Molecular Formula
The FATE database may be searched by molecular formula, but formulas are
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not unique and all chemicals with Che same formula will be retrieved. Element
symbols are arranged within the total formula according to the Hill System1*
for carbon-containing compounds, where C for carbon appears first, followed by
H for hydrogen, then the remaining symbols are alphabetically detailed. For
non-carbon-containing compounds, all symbols are arranged alphabetically.
d) Preferred and Common Names
Chemical-Abstracts-preferred index names, up to 250 characters in length,
have been entered in the CAS file as they appear in the Chemical Abstracts
Service Registry Handbook. These names were based on the Chemical Abstracts
Eighth, Ninth, Tenth and Eleventh Collective Index Period nomenclature
policies. The CAS file can be searched by any string up to 20 characters in
length contained in a CAS name. If the first character of the search string
is upper case and the rest lower case, the program will look for that string
at the beginning of each CAS name. If all characters of the search string are
lower case, the entire CAS file will be searched for the presence of the
string imbedded in all CAS names. The report will contain all hits for the
20-character string.
Some chemical names are preceded by numeric or positional designations,
such as D- or L-, .alpha.-, etc. The prefix characters have been included in
a separate field for each CAS number. The prefix is not included in the
search for the CAS preferred index name.
The CAS file can also be searched by common name. The search string will
be an exact match of any string up to 50 characters in length. Upper and
lower case rules apply as detailed above, except that prefixes are included in
the search. The database may contain up to ten common names for a given
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chemical. The report will contain all hits for the 50-character string.
e) Reference Number
The reference citations contained in the REF file are indexed by a unique
REF number. The REF number consists of one upper case letter, the first
initial of the primary author's last name, and a sequential number. The
database may be searched by a single reference number, a range of reference
numbers, the name of the primary author, or any of the names of the secondary
authors.
DATABASE MENU SYSTEM
Update of FATE
FOCUS programs that allow the database to be updated have restricted
access, and can only be used by the database management team.
Data Retrieval from FATE
The FOCUS menu and reporting program can be accessed by any outside user
who obtains an account and a password for the FATE database. Initial contact
with the database is established by logging onto the restricted FATE account
on the ATHENS VAX. Transactions from the FATE database can be captured on and
printed from the personal computer of the user. Printing capabilities are not
available for any users from the ATHENS VAX because of the restricted access
to the FATE account. After logging onto the ATHENS VAX. the user obtains the
following menu:
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ENVIRONMENTAL FATE CONSTANTS
INFORMATION SYSTEM
FATE CONSTANTS REPORTS
CAS File Report
Reference File Report
Face Constants, Reference Report
Quit
ENTER: C, R, F or Q
To respond to the menu, select the first letter of the function desired
and press Enter or Return, or use the arrow key to move the highlight bar.
When C for CAS File Report is selected the following screen will appear:
CAS FILE LISTING SELECTION SCREEN
Use the TAB key to move down the screen
CAS Number:
Formula:
Smiles:
CAS Name:
Common:
- Press
RETURN for the report PF1: Help Menu
PF2: Clear the screen PF3: Return to Main Menu
The three selection screens in FATE have access to the same Help Menu.
The Help Menu, PF1, provides information about database fields, PF key
functions, etc. The PF2 key can be used to clear the screen of data that have
been entered previously.
When R for Reference File Report is selected from the Main Menu, the
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following selection screen will appear:
REFERENCE SELECTION SCREEN
Use Che TAB key to move down Che screen
Single Reference Number or Range: To:
Primary Author:
Secondary Author:
Press
RETURN for Che report PF1: Help Menu
PF2: Clear the screen PF3: Return Co Main Menu
When F for Face Constants, Reference Report is selected from the Main
Menu, Che following selecCion screen will appear:
FATE CONSTANTS, REFERENCE SELECTION SCREEN
Use Che TAB key Co move down Che screen
CAS Number:
Formula:
Smiles:
CAS Name:
Common:
REF Number:
pK(a):
H(c):
P(v):
S(w):
K(p):
K(oc):
K(ow):
k(d):
0(r):
E(l):
k(h):
k(bio):
Press RETURN for Che report PF1: Help Menu
PF2: Clear the screen PF3: Return to Main Menu
A sample report for Che hydrolysis rate constanC kh, for
1,1,2,2-CeCrachloroeChane, CAS number [79-34-5] follows:
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Face Data, References as of 12/26/90 Page 1
PF7 Co scroll backward RETURN Co go forward PF3 Co aborc reporC
CAS Number: 79345 FATE Code: OS FATE Reference: C00000165
Analytical Method: GLC Estimating Program:
Medium: buffered disc. H20 pH: see comments
Experimental Temperature: 95.00 C
Produces: [79-01-6]
Comments: 1st order races were meas. over Che pH range 5 Co 9 aC 11 Cemp.
Data were extrapolated Co IsC and 2nd order races ac 25°C wich Che
RATE program. Ea(base) was estimated as 21.2 kcal/mol or 88.8
kJ/mol.
half-life
k(acid)
k(base)
k(h), PH 7
k(neutral)
: 98 day
: 0.0/M-yr
: 2.6E7/M-yr
: 2.6/yr
: 0.0/yr
(25 C)
(25 C)
(25 C)
(25 C)
(25 C)
FATE Reference: C00000165
Authors: Cooper, William J.; Mehran, Moscafa;
Rlusech, David J.; Joens, Jeffrey A.
Dace: 1987
Tide: Abiotic transformation of halogenated organics. 1. Elimination
reaction of 1,1,2,2-tetrachloroethane and formation of 1,1,2-
crichloroechene.
CiCation: Environ. Sci. Technol. 21(11):1112-1114.
DISCUSSION and CONCLUSION
The development of Che FATE database grew ouc of the need for face
constants in chemical risk assessment. The literature searches that were
conducCed in response Co EPA requests for data revealed that few values were
available, ChaC many publications lacked sufficient documentation Co decermine
data credibility, and that many data were determined under environmencally
unrealistic condicions. More importantly, very few authors determined the
products of Che degradation processes. Risk should be assessed for Che
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"persistent" chemical(s) and not for the "transient" parent compound or
intermediate products alone17.
A support activity was organized at ERL-Athens to provide equilibrium and
kinetic constants for critical chemicals (and their transformation products)
whose environmental transport and transformation must be assessed. This
activity involves conducting literature searches for measured data,
postulating transformation pathways and products, performing laboratory
measurements of fate constants, and estimating values using computational
techniques as required.
The FATE database was developed to eliminate a number of the problems
that were experienced in this support. As a result, FATE users will find
values that can be used with confidence for up to twelve rate and equilibrium
constants. Data are screened for applicability to environmental assessment,
and only data from primary sources are entered. If a value was determined in
a manner that prevents extrapolation to environmental conditions or lacks
sufficient documentation to ascertain environmental applicability, it will not
be entered into the database. Transformation products are listed when
available. Chemical hydrolysis rate constants are extrapolated to a standard
format with a computer program developed at ERL-Athens. Acidic, basic and
neutral contributions to the rate constant are combined to calculate the
overall hydrolysis rate constant, Ic*, and the half-life of the chemical at
25"C and pH 7. In addition, hydrolysis data are reported as second-order
acidic and basic rates and a first-order neutral rate at 25°C. For critical
chemicals, when measured data cannot be located, laboratory measurements may
be performed at ERL-Athens. Data are also computed whenever an applicable
technique is available, using both conventional techniques, e.g. QSAR, and the
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newly developed SPARC expert system.
Future emphasis with the FATE database will be on data computed with
SPARC. This expert system has the capability of crossing chemical boundaries
to provide estimates for all organic chemicals and will generate reliable
values for a fraction of the cost and time it takes to determine an
experimental value.
ACKNOWLEDGMENT
The authors would like to express their appreciation for the assistance
and recommendations in the development of the database to Computer Sciences
Corporation, especially Mr. Matthew P. Holway.
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partition coefficients (K,. ) of 61 organophosphorus and carbamate
insecticides and their relationship to respective water solubility (S)
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Barich, A. Liu and T. Mill, 1984. Elements of a quality database for
environmental fate assessment. Final Report, EPA Contract No. 68-03-
2981, SRI International Project 2073, Work Assignment No. 6. Unpublished
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Washington, D.C.
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6. H. P. Kollig, 1988. Criteria for evaluating the reliability of
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system located on the VAX cluster in the National Computer Center in
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Medicinal Chemistry Project.
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reactivity — the ultimate SAR. U.S. Environmental Protection Agency,
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14. E. Anderson, G. D. Veith, and D. Weininger, 1987. SMILES: a line
notation and computerized interpreter for chemical structures. U.S.
Environmental Protection Agency, Duluth, MN. EPA/600/M-87-021.
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17. H.. P. Kollig, 1990. A fate constant data program. Toxicol. and Environ.
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