Groundwater quality is an issue which needs attention because of
the potential hazard associated with contamination of our
nation's water supplies. The United States depends on farmers and
the agricultural industry to maintain current production levels
of food and fibre. As a result, they make extensive use of
fertilizers, pesticides, and other chemicals to control disease
while promoting plant and animal growth. The negative aspect of
the use of these chemicals is their possible transport into
groundwater which supplies about 25%. of the nation's fresh
water. Accurate information on the possible contamination of
groundwater by agri-chemicals is needed for intelligent planning
by management, government, and industry. Such information can
only be obtained by creating and testing various hypotheses which
attempt to describe chemical mobility. This can be accomplished
by designing computer models which integrate and incorporate the
latest scientific knowledge allowing simulations of environmental
impact. Among these processes are physical, management, crop
growth, nutrient, soil chemistry, and pesticide processes.
The pesticide processes include many physicochemical
relationships. In order to simulate these processes, complete and
accurate data on the properties of each chemical used must be
available for input into the model. Without complete and accurate
data, the accuracy, and hence value, of the model is severely
At present there is no definitive database of properties of chemicals used as pesticides. There are a number of compilations of data on pesticides, including Handbooks which are either devoted completely or partially to data on pesticides. However these sources or databases are incomplete in their scope of information and also lack criteria for defining the quality of the data reported. In addition, the data are often reported without mentioning the temperature at which the parameters were obtained, nor in the original source. These databases also have data gaps which limit their usefulness for many modeling activities. This research project is designed to produce a pesticide database containing the highest quality data available.
A definitive database of pesticide properties will be created
with a well defined, step-wise systems approach. The overall
steps are as follows:
1. Establish a Pesticide Properties Database (PPD) National
Research Project Coordination Team (NRPCT).
2. Design the database, search the literature, obtain data from
other sources, and enter the data into the database.
3. Evaluate the data (accuracy, quality, and completeness)
according to established or newly developed criteria. Data will
be evaluated in an objective manner, using a series of expert
systems which will be developed for that purpose.
4. Fill in the data gaps by calculating missing properties using
existing or newly developed theoretical techniques which have
been validated for the various classes of compounds found in the
5. Disseminate the database.
6. Maintain and update the database.
1. Establishment of a PPD National Research Project Coordination
A team of scientists from ARS, other government agencies, and
industry has been established to provide leadership and facilitate
the team coordination. The team will function under the guidance of
the ARS National Program staff (NPS) representatives. The team
members will consist of scientists from the Systems Research
Laboratory and the Pesticide Degradation Laboratory in Beltsville,
Missouri, the Southeast Watershed Research Laboratory in Tifton,
Georgia, scientists from other government agencies, and scientists
from universities and industry (from companies belonging to the
National Agriculture Chemical Association (NACAI). Representatives
from the EPA Office of Toxic Substances, Office of Pesticide
Program and US Geological survey are also being asked to serve on
the team. A representative from the International Union of Pure and
Applied Chemistry (IUPAC) Pesticide Commission will also be asked
to serve on the team. IUPAC participation is important as part of
the evaluation of the database and the distribution of the database
to the scientific community. The team will use the System Research
Laboratory's Agricultural Systems Research Resource (ASRR) computer
conferencing software for continuing discussions. The conference.
"PESTICIDE DATABASE" has been established and all interested parties
are being invited to join the conference, which can be accessed by
direct dial, Telenet, or Arpanet.
The PPD NRPCT will approve the plans submitted to the group by the
Team Leader and generally oversee the activities to assure that
they are on target, on time, and are supporting ARS objectives and
other groundwater needs of the U.S.A. When necessary the PPD NRPCT
will meet, although most of the work is expected to be done locally
and via computer conferencing.
2. Design the database and search the literature, obtain data from
other sources, and enter the data into the database.
The first 30 compounds have been chosen for the database from a
prioritized list of compounds being studied by the ARS. These are
Figure 1. Many additional compounds are to be added in the
next year as data are received by members of NACA who have agreed
to voluntarily contribute data to the project: The data being
submitted by industry to this project are the same as those
provided to the states of California and Arizona under those
states' pesticide registration laws. The initial list of some 40
properties (fields or data elements) which are to be included in
the database have been chosen and the information associated with
each item has been defined. This will include chemical names, CAS
Registry Number (CAS RNI, and other identifiers, and variables
(temperature, pressure, pH, and so forth), as well as important
chemical properties such as solubility, vapor pressure, various
partition coefficients, and rate constants. Details on the data
elements, format, and access to the ARS ASRR computer system are
available upon request from the senior author (SRH).
The dgasell computer database management system, coupled with the Clipper software, has been chosen for implementation of data entry, updating, search, and retrieval. Dgasell is so widely used and by using Clipper we are able to provide a royalty-free search system for IBM PC compatible computers, other software would have required royalty fees and would have involved other non-technical complications which would have made the world-wide dissemination of the PPD more difficult.
To date most of the effort has been expends searching the
literature and obtain any data from other sources. Cooperation from
industry has been essential to the project's progress. The need
for data evaluation has been pointed up most strikingly by data
on the solubilityof the insecticide fenthion. We have found that
for almost 30 years the solubility of fenthion has been reported
in handbooks as about 55 ppm, whereas the correct solubility (run
under proper experimental conditions) is actually 4.2 ppm. This
difference of a factor of almost 15 is too great to be ignored.
Table 2 shows the summary of the solubility values reported for
After a year of work on the first evaluated database of pesticide
properties we feel that the goals of the project can be
accomplished, but that more time than originally anticipated will
be required, as the available data are more difficult to obtain
and are less reliable than first anticipated. An interim database
of values obtained will be our first goal, followed closely by
proper evaluation of the database, with appropriate data quality
 Heller, S. R., Scott, K, and Bigwood, D. W.,
The Need for Data
Evaluation of Physical and Chemical Properties of Pesticides,
Envirn. Sci. Tech., submitted.