Pesticides and Groundwater
CORNELL COOPERATIVE EXTENSION
Pesticides and Groundwater: A Guide for the Pesticide User
Nancy M. Trautmann and Keith S. Porter
Center for Environmental Research
Robert J. Wagenet
Department of Agronomy
Pesticide Contamination of Groundwater
Agricultural pesticide users traditionally have been concerned with protecting
crop yields by controlling pest infestations. Environmental concerns have
focused on protecting nontarget species, such as the birds whose eggs became
unviable because of DDT; this compound was removed from agricultural use in
1973. Within the past decade a new concern has emerged. In the late 1970s,
aldicarb was discovered in 96 wells on Long Island and DBCP
(dibromochloropropane) was found in more than 2,000 wells in California,
focusing attention on the question of how to control pests without contaminating
groundwater. Subsequent surveys have discovered more pesticide residues in
groundwater. In a recent study conducted by the U.S. Environmental Protection
Agency, forty-six pesticides were found in groundwater in twenty- six states as
a result of normal agricultural applications (table 1).
Once groundwater is contaminated, analyzing the problem and providing
alternative water supplies can be quite expensive. Since the discovery in 1979
of aldicarb in Long Island groundwater, for example, more than $3 million has
been spent measuring aldicarb concentrations in Long Island wells. Carbon
filtration units have been installed in more than 2,500 affected households, and
plans are being made to replace individual wells with expensive community water
supply systems. These huge expenses have helped to define and treat the problem,
yet have not corrected the underlying groundwater contamination.
Another possible consequence of pesticide contamination of groundwater is losing
the use of a particular pesticide. Aldicarb, for example, may no longer be used
on Long Island or in parts of California, Florida, Massachusetts, New Jersey,
and Wisconsin. Other compounds such as DBCP and EDB (ethylene dibromide) were
banned completely from agricultural use after their discovery in groundwater. Of
the forty-six pesticides recently found in groundwater, twelve are no longer
available for agricultural use.
Cleanup of groundwater contaminated by pesticides often is impossible, and the
contamination may last for many years. The cold temperatures and low microbial
activity in groundwater cause pesticide degradation to occur more slowly than at
the soil surface. The slow movement of groundwater means that it may take
decades for the contaminated water to flow beyond the affected wells. Even
determining which wells will be affected and for how long is a difficult
problem, necessitating expensive long-range monitoring to ensure the safety of
drinking water supplies. Clearly, the best solution is to keep pesticides out of
groundwater through careful storage, use, and disposal practices.
Most farm families rely on their own wells. Such private wells are rarely tested
or treated, and in many instances, they are located close to fields on which
pesticides have been applied. Groundwater supplying the wells may contain
pesticides that have been leached from the fields by rain, melted snow, and
irrigation water. It should be noted, however, that most pesticides have not
been found to leach, and certainly not all farm wells are contaminated. An
understanding of what causes some pesticides but not others to leach is crucial
in protecting groundwater quality.
Leaching of pesticides depends in part on the amount applied per acre per year;
where, when, and how it is applied; the solubility of the compound: how strongly
it is held by the soil; and how quickly it breaks down in the root zone. After a
pesticide is applied to a field, it meets a variety of fates (fig. 1. See fact
sheet). Some may be lost to the atmosphere through volatilization, carried away
to surface waters by runoff, or broken down in the sunlight by photolysis.
Pesticides in soil may be taken up by plants, degraded into other chemical
forms, or leached downward, possibly to groundwater. The remainder is retained
in the soil and continues to be available for plant uptake, degradation, or
leaching. How much pesticide meets each of these fates depends on many factors,
- the properties of the pesticide
- the properties of the soil
- the site conditions, including climate
- and management practices
Many pesticides bind strongly to soil and are therefore immobile. For those that
are mobile in soil, their leaching to groundwater can be thought of as a race in
time between their degradation into nontoxic by-products and their transport to
groundwater. If the pesticide is not readily degraded and moves freely with
water percolating downward through the soil, the likelihood of it reaching
groundwater is relatively high. If, however, the pesticide degrades quickly or
is tightly bound to soil particles, then it is more likely to be retained in the
upper soil layers until it is degraded to nontoxic by- products. Even if
degradation is slow, this type of pesticide is unlikely to pose a threat to
Table 1. Pesticides in current use that have been found in groundwater due to
normal agricultural operations
Health Maximum Median
Advisory States with Concentration Concentration
Chemical Name Level a Detections (ppb) (ppb)b
1 3-D 0.20c 1 270.00 123.00
2,4-D 70 2 49.50 1.40
Alachlor 1.5c 12 113.00 0.90
Aldicarb 10 7 315.00 9.00
Aldrin 2 0.10 0.10
Atraton 1 0.10 0.10
Atrazine 3.0 13 40.00 0.50
Bromacil 80 2 22.00 9.00
Carbofuran 36 3 176.00 5.30
Chlorothalonil 1.5c 2 12.60 0.02
Cyanazine 9.0 6 7.00 0.40
Dacthal 3500 1 1039.00 109.00
Diazinon 0.63 1 478.00 162.00
Dicamba 9.0 2 1.10 0.60
Diuron 14 1
Endosulfan 1 0.40 0.30
Ethoprop 1 12.60
Fonofos 14 2 0.90 0.10
Hexazinone 210 1 9.00 8.00
Linuron 1 2.70 1.90
Malathion 1 53.00 41.50
Methamidophos 1 10.50 4.80
Methomyl 175 1 9.00
Methyl parathion 2.0 1 256.00 88.40
Metolachlor 10 5 32.30 0.40
Metribuzin 175 4 6.80 0.60
Oxamyl 175 3 395.00 4.30
Parathion 1 0.04 0.03
Picloram 490 3 49.00 1.40
Prometon 100 1 29.60 16.60
Propazine 14 2 0.20 0.20
Simazine 35 7 9.10 0.30
Sulprofos 1 1.40 1.40
Trifluralin 2.0 4 2.20 0.40
a Proposed lifetime health advisory level
b Based on data from multiple studies, a single study, or a single well
c Lifetime exposure levels based on a 10-6 risk of causing cancer
Source: Williams (1988)
Experience in the past ten years has shown that certain properties of pesticides
are associated with leaching. As a result of many field and laboratory studies,
the U.S.Environmental Protection Agency has compiled a list of key chemical and
physical properties called threshold values (table 2). Compounds with properties
that do not satisfy the threshold values warrant extra attention because of
their relatively high potential for leaching to groundwater. The threshold
values provide only a rough guide, however. The herbicide simazine, for example,
is less soluble than the threshold value but nevertheless has been found in
groundwater in seven states.
Table 2. Threshold values indicating polential for groundwater contamination
Physical Property Threshold Value
Water solubility greater than 30 ppm
Henry's Law Constant less than lO-2 atm - m-3 mol
Kd less than 5, usually less than 1 or 2
Koc less than 300 to 500
Hydrolysis half-life more than 25 weeks
Photolysis half-life more than 1 week
Field dissipation half-life more than three weeks
Source: U.S. Environmental Protection Agency, 1986, Pesticides in Groundwater:
Solubility. Chemicals that dissolve readily in water are said to be
highly soluble. As water moves downward through soil, it carries with it water-
soluble chemicals. All other properties being similar, the pesticide with a
higher solubility has greater potential of being moved downward through the
soil, possibly leaching to groundwater.
Volatilization. Vapor pressure is a measure of the tendency of a compound
to become a gas. The higher the vapor pressure of a pesticide, the faster it is
lost to the atmosphere and the less that remains available for leaching. This
does not necessarily mean, however, that pesticides with high vapor pressures
pose no threat to groundwater. Some pesticides, such as soil fumigants, are
injected into the soil and therefore have limited exposure to the atmosphere. If
these compounds are highly soluble in water, they can be carried with soil water
to groundwater. EDB and DBCP, for example, are soil fumigants that have been
detected in groundwater in several states.
The likelihood of a pesticide to volatilize is a function of both its vapor
pressure and its solubility. This function is expressed by Henry's Law Constant
(H), the second threshold value in table 2:
H = vapor pressure
The lower the value of the Henry's Law Constant, the greater the leaching
potential of a pesticide. Examples of pesticides with high values for H and thus
low leaching potentials include trifluralin, triallate, phorate, and dieldrin.
Adsorption. The tendency of a pesticide to leach also depends on how
strongly it adsorbs to soil. Adsorption refers to the attraction between a
chemical and soil particles. Compounds that are strongly adsorbed onto soil are
not likely to leach, regardless of their solubility. They are retained in the
root zone where they are taken up by plants or eventually degraded. Compounds
that are weakly adsorbed, on the other hand, will leach in varying degrees
depending on their solubility.
Thc strength of sorption is a function of the chemical properties of the
pesticide, the soil type, and the amount of soil organic matter present. Kd and
Koc, the third and fourth threshold values listed in table 2, are measures of
pesticide adsorption on soils.
Kd, the adsorption partition coefficient, can be calculated by mixing soil,
pesticide, and water, then measuring the concentration of pesticide in solution
after equilibrium is reached (fig. 2. See fact sheet). The adsorption
coefficient is the ratio of pesticide concentration in the adsorbed phase to
that in solution:
Kd = concentration of chemical adsorbed
concentration of chemical dissolved
A wide range exists in pesticide partition coefficients. DDT, for example, has a
Kd value roughly 20,000 times as high as that for aldicarb and 1,500 times as
high as that for atrazine. This explains why aldicarb and atrazine have been
found in groundwater in agricultural areas while DDT has not.
The major drawback of using Kd to predict leaching of pesticides is that it is
highly dependent on soil characteristics. Organic matter is the most important
soil constituent determining pesticide retention. It therefore is useful to
adjust the Kd value by the percent organic carbon in the soil. This yields
another adsorption coefficient, Koc, which is relatively independent of soil
Koc = Kd
% organic carbon in soil*
* (percentage expressed as a decimal fraction)
Degradation. The final three threshold values listed in table 2 are
measures of a pesticide's rate of degradation, or chemical breakdown. The longer
the time before a compound is broken down, the longer it is available to treat
the target pest, be it weed or insect. Unfortunately, however, the pesticide
also is subject to leaching over this longer period of time.
One process through which pesticides degrade is photolysis, or breakdown caused
by exposure to sunlight. Another is hydrolysis, the reaction of a chemical with
water. Hydrolysis of pesticides occurs in the root zone and at slower rates in
groundwater. The third major form of pesticide degradation is through oxidation
and other reactions mediated by microorganisms in the soil.
The natural distribution of microbes in the soil has important implications for
managing pesticides. The vast majority of microbes live in the uppermost parts
of the soil. If a chemical leaches below the root zone, it encounters far fewer
microbes and is less likely to degrade before leaching to groundwater.
The final value in table 2, the field dissipation half-life, is an overall
empirical estimate of the length of time in which half of the original amount of
the applied pesticide will disappear. This estimate takes into account physical,
chemical, and biological degradation, plant uptake, and for highly volatile
pesticides, volatilization. The longer the half-life, the greater the length of
time the pesticide remains in the soil and, hence, the longer the opportunity to
Half-life is difficult to predict because it varies widely for each compound and
soil condition. Factors affecting half-life include:
- soil type
- soil temperature
- soil moisture content
- concentration of the chemical
- method of application
- chemical structure
- amount of sunlight
- microbial populations
Although half-life estimates provide a useful empirical measure of pesticide
degradation in soil, their use requires caution. Because half-life estimates are
highly dependent on the chemical, physical, and biological properties of the
soil being tested, they cannot be accurately extrapolated to soils under
different conditions. In general, degradation proceeds faster in moist soils
than in dry ones, but the changes in half-life are not consistent from one soil
Half-lives in subsoils are usually much longer than those for the root zone
because of the great reduction in microbial populations and the changes in
physical and chemical conditions. Once a pesticide gets into groundwater,
therefore, its degradation is likely to proceed at a slower rate than that
predicted by its half-life in the root zone.
Many soil characteristics affect leaching; the principal ones are:
- soil texture
- soil permeability
- soil organic matter content
- soil structure, including macropores
Soil texture is determined by the relative proportions of sand, silt, and clay.
Texture affects the movement of water through soil and, therefore, also the
movement of dissolved chemicals such as pesticides. The coarser the soil, the
faster the movement of percolating water and the lower the opportunity for
adsorption of dissolved chemicals. Soils with more clay and organic matter tend
to hold water and dissolved chemicals longer. These soils also have far more
surface area on which pesticides can be adsorbed. The coarser the soil texture,
therefore, the greater the chance of a pesticide reaching groundwater.
Soil permeability is a measure of how fast water can move downward through a
particular soil. Water moves quickly through soils with high permeability, so
frequent irrigation may be necessary. Because dissolved chemicals are
transported by percolating water, in highly permeable soils the timing and
methods of pesticide applications need to be carefully designed to minimize
Soil organic matter influences how much water is retained in the soil and how
well pesticides are adsorbed. Increasing the soil's organic content, such as by
applying manure or plowing under cover crops, therefore enhances the soil's
ability to hold both water and dissolved pesticides in the root zone.
Soil structure, the way soil particles are aggregated, also affects water
movement. Compared with compacted soil, loosely packed soil aggregates are more
likely to allow easy downward movement of water. Sometimes large openings
(macropores) resulting from physical processes such as animal borings or
freezing and thawing permit rapid water movement through fine-textured soils in
which water movement would otherwise be slow.
Conditions of the site also affect the potential for leaching of pesticides.
- depth to groundwater
- geologic conditions
- climate and irrigation practices
Depth to Groundwater. Depending on climate and local geology, groundwater
may be only a few feet below the soil surface. With such shallow depths to
groundwater, the filtering action provided by the soil and the opportunities for
degradation or adsorption of pesticides are low. Extra precautions are needed to
protect groundwater in such cases. If rainfall is high and soils are permeable,
water carrying dissolved pesticides may take only a few days to percolate
downward to groundwater.
The depth to groundwater does not remain constant over the course of the year.
It varies according to the amount of precipitation and irrigation, whether the
ground is frozen, and how much groundwater is being withdrawn by pumping.
Groundwater levels tend to fall in summer, when evaporation and plant uptake are
high, and in winter if recharge is hampered by frozen soils. Spring and fall
generally are times of greatest recharge and, therefore, also of highest water
table elevations. Such fluctuations in recharge quantities affect recharge
quality as well. The high water table elevations in spring, for example, mean
there is less possibility for soil filtration of pesticides leached from the
root zone by heavy spring rains.
Geologic Conditions. In addition to the depth to groundwater, it is
important to consider the permeability of the geologic layers between the soil
and groundwater. Gravel and other highly permeable materials allow water and
dissolved pesticides to percolate freely downward to groundwater. Layers of
clay, on the other hand, are much less permeable and thus inhibit the movement
of water. Groundwater quality is most vulnerable in areas where permeability of
geologic layers is rapid.
Regions with limestone deposits are particularly susceptible to groundwater
contamination because water with dissolved pesticides can move rapidly through
cracks in the bedrock underlying the soil, receiving little filtration or chance
for chemical degradation before reaching groundwater.
Topography. Whether water runs off the land surface or infiltrates into
the soil depends on topography, plant cover, and soil type. Surface run off is
greatest on land with steep slopes, sparse vegetation, and relatively
impermeable soils. Water that runs off hilltops and hillsides tends to collect
in depressions, where it sits until it evaporates or infiltrates into the soil.
In flat areas with permeable soils, water will infiltrate into the ground rather
than run off. Susceptibility to leaching is highest in flat or depressed areas
because of the greater chance for infiltration rather than runoff.
Climate and Irrigation Practices. Areas with high rates of rainfall or
irrigation are most susceptible to leaching of pesticides, especially if the
soils are highly permeable. If high rainfall or heavy irrigation occurs during
or shortly after the application of agricultural chemicals, the chemicals can be
quickly leached from the root zone. Once leached below the root zone, pesticides
cease to be available for effective action on the target pest and become
potential groundwater contaminants.
Management Practices. Another factor determining leaching potential is
the way in which a pesticide is applied. The injection or incorporation of a
pesticide into soil makes it readily available for leaching. The rate and timing
of a pesticide's application also are critical in determining whether it will
leach. The larger the amount used and the closer the time of application to a
heavy rainfall or irrigation, the more likely that any pesticide prone to
leaching will be lost to groundwater. When practicing chemigation, the risk of
pesticide leaching can be minimized by using the lowest amount of water needed
to activate the pesticide.
Many factors determine whether a pesticide will reach groundwater, including its
chemical properties, the soil type, the depth to groundwater, and the pesticide
management practices. By combining all these factors, the areas most vulnerable
and the practices most conducive to pesticide contamination of groundwater can
be determined (table 3).
Greatest care needs to be taken with pesticides that are highly soluble, do not
adsorb strongly to soil particles, and persist for a long time in soil. The
Environmental Protection Agency has established a list of such pesticides,
called suspected leachers, for which extra precautions should be used to prevent
contamination of groundwater. Some of these are listed in table 4.
Table 3. Factors indicating the greatest likelihood of groundwater
contamination by pesticides
sand and gravel
low organic matter content
shallow depth to groundwater
wet climate or extensive irrigation
depressions or flat areas where water collects
poor timing with respect to climate
overapplication (rate too high or application too frequent)
Recommended Applicator Practices
Pesticide applicators can minimize leaching by following these guidelines:
- Use pesticides only when necessary and in the minimum dose consistent with
effective pest management.
- Determine the soil type and its susceptibility to leaching before using
- Apply pesticides specifically to the target site,avoiding wells and surface
water such as ponds and streams.
- Choose pesticides with low susceptibility to leaching.
- Follow the storage, use, and disposal directions on the pesticicle label. If
regionally specific recommendations such as the l990 Cornell Recommends for
Field Crops are available, use these instead.
- Measure carefully, and stay within the recommended application rates.
- Properly calibrate and maintain application equipment.
- Avoid pesticide spills, and prevent back-siphoning of pesticide-contaminated
water into the water source.
- Properly dispose of any leftover pesticides, tank mixes, and rinse water
according to label instructions or Cornell Cooperative Extension
- Store pesticides safely, in the original labeled container and in a cool,
well-ventilated location away from wells, pumps, or other water sources.
- Maintain records of pesticide use to avoid overuse and to help plan future
- Delay irrigation at least one or two days after pesticide applications.
- Avoid irrigation runoff, especially in clay soils, to decrease erosion and
pesticide contamination of water supplies. Periodically inspect wells to ensure
that their location is distant from pesticide application sites and that the
well seals are properly constructed and maintained to prevent the entry of
- Spray-apply pesticides only under calm, no-wind conditions.
- Wherever possible, use Integrated Pest Management.
Integrated Pest Management.
Integrated Pest Management (IPM) seeks to reduce pesticide use to the minimum
level necessary to produce high-quality food and agricultural products while
protecting human health and environmental quality The New York State IPM program
operates under five objectives:
- To minimize crop losses caused by insects, weeds, and plant diseases.
- To optimize the use of cultural management techniques, biological pest controls,
and resistant varieties.
- To maximize the effectiveness of pesticide use.
- To reduce pest management costs.
- To minimize the development of pesticide resistance.
IPM encourages natural control with beneficial organisms such as predators,
parasites, and pathogens. Monitoring, or "scouting," is used to detect pest
infestations so that pesticide applications can be targeted to times of need.
Such field monitoring can significantly reduce pesticide use while protecting
crop yields. In New York State, for example, onion growers who followed IPM
thresholds based on weekly monitoring reports from field scouts were able to
reduce insecticide use by 54 percent and save $24 per acre in insecticide costs.
Thrips populations were 42 percent lower than those on farms that did not
participate in the field scouting program, and the quality of the harvested
onions was unaffected.
Most groundwater contamination problems are associated with pesticides applied
to control soil-dwelling pests such as nematodes, weeds, pathogens, and insects.
IPM programs of greatest importance in reducing groundwater contamination are
those that minimize the use of soil pesticides. Such methods include crop
rotation, fallowing, solarization, the use of resistant cultivars, and the use
of less persistent pesticides.
Studies have shown that nematode damage of cotton yields in California can be
fought just as effectively by rotating crops with resistant tomato cultivars as
by fumigating the soil before planting. Nematode-resistant potato varieties
likewise have reduced the need for pesticides on potato crops. To control the
golden nematode, growers formerly had to both fumigate the soil prior to
planting and apply other pesticides during the growing season. Using eleven
newly developed resistant varieties, New York State potato growers have reduced
pesticide use by 56,000 gallons over the past four years.
Various estimates suggest that the adoption of currently available IPM practices
would permit a 40 to 50 percent reduction in the use of insecticides within a
five-year period and a 70 to 80 percent reduction in the next ten years, without
sacrificing crop yield or grower profit. Lower pesticide use would accordingly
reduce the potential for groundwater contamination.
Table 4. Pesticides susceptible to leaching to groundwater
Chemical Name Common Trade Names
Acifluorfen Blazer, Tackle
Alachlor Alanex, Alanox, Alatox, Bronco, Lasso,
Aldrin Aldrex, Aldrite, Altox
Ametryn Ametrex, Evik, Gesapax, Trinatox
Atrazine Aatrex, Atratol, Bicep, Conquest,
Bromacil Hyvar, Krovar
Chlorothalonil Bravo, Daconil, Exotherm Termil
Cyanazine Bladex, Conquest, Extrazine
Dalapon Dalapon, DPA
Diazinon Knox Out, Basudin, Dazzel, Spectracide,
Dicamba Banvel, Marksman, Weedmaster
phenoxyacetic acid Envrert, Landmaster, Plantgard, Salvo,
Tordon, Weedar, Weed-B-Gon, Weedone, and
1,3-Dichloropropene D-D 92, Telone II Soil Fumigant
Diuron Karmex, Krovar
Fluometuron C-2059, Cotoran, Cottonex
Linuron Gemini, Lorox
Malathion Cythion, Malamar, Vegfru, Zithiol, and
Methomyl Lanate, Lanox, Methomex, Nudrin
Methyl parathion Penncap-M
Metolachlor Bicep, Dual, Turbo
Metribuzin Canopy, Lexone, Sencor, Turbo
Parathion Alkron, Phoskil,Soprathion, Thiophos, and
Picloram Grazon, Tordon
Propazine Gesamil, Milogard, Milo-Pro, Primatol,
Simazine Amizine, Princep, Simadex
Terbacil Geonter, Sinbar
Trifluralin Spike, Treflan
Although pesticide contamination of groundwater was unrecognized only twenty
years ago, it has emerged in recent years as a major factor in the development,
licensing, and use of pesticides in the United States. When pesticides do get
into groundwater, cleanup of the contamination usually is impossible. The
contamination can last many years and spread over a large area before dilution
and chemical decay eventually reduce the pesticide concentrations to levels
acceptable for drinking water. A major question facing modern agriculture,
therefore, is how to control pests and protect crop yields without allowing
pesticides to contaminate underlying groundwater.
Many factors determine whether a pesticide will leach to groundwater, including
pesticide properties, soil characteristics, site conditions, and management
practices. The pesticides most susceptible to leaching are those with high
solubility in water, low adsorption to soil, and long-term persistence. When
these pesticides are applied to sites with sandy soils, shallow depth to
groundwater, and either a wet climate or extensive use of irrigation, the risk
of groundwater contamination is high.
Pesticide applicators can take measures to help protect groundwater quality.
These include assessing the susceptibility of the site before using pesticides,
then tailoring pesticide applications to the particular site conditions. IPM
programs can help protect groundwater by promoting the use of a variety of
economically and ecologically sound pest control techniques rather than sole
reliance on chemical pesticides.
For Further Reading
Cohen, S.Z., S.M. Creeger, R.F. Carsel, and C.G. Enfield. 1984. Potential
pesticide contamination of groundwater from agricultural uses. In Treatment and
Disposal of Pesticide Wastes, ed. R.F. Kruger and J.N. Sieber, 297-325. ACS
Symposium Series no. 259. Washington, D.C.: American Chemical Society.
Cornell University and the New York State Department of Agriculture and Markets.
1987. New York State Integrated Pest Management Program, 1987 Annual Report.
Geneva, N.Y.: New York State Agricultural Experiment Station.
Graham-Bryce, I.J. 1981. The behavior of pesticides in soil. In The Chemistry of
Soil Processes, ed. D.J. Greenland and M.H.B. Hayes. Sussex, England: John Wiley
and Sons Ltd.
Marer,P.J., M.L. Flint, and M.W. Stimmann. 1988. The Safe and Effective Use of
Pesticides. University of California, Statewide Integrated Pest Management
Project, Division of Agriculture and Natural Resources, Publication 3324.
New York State College of Agriculture and Life Sciences. 1990. 1990 Cornell
Recommends for Field Crops. Ithaca, N.Y.: Cornell Cooperative Extension.
The Resource Center
PO Box 3884
Ithaca, NY 14852-3884
Email orders: firstname.lastname@example.org
Williams, W.M., P.W. Holden, D.W. Parsons, and M.W. Lorber. 1988. Pesticides in
Ground Water Data Base, 1988 Interim Report. Washington: U.S. Environmental
Protection Agency, Office of Pesticide Programs.
A Related Slide Set:
Porter, K.S., and M.W. Stimmann. 1988. Protecting Groundwater. A Guide for the
Pesticide User. Slide Set, Storyboard, and Manual for Instructors. (Available
from New York State Water Resources Institute, Cornell University, Ithaca, NY
Other fact sheets in this series include:
Modern Agriculture. Its Effects on the Environment (400.01) Nitrate: Health
Effects in Drinking Water (400.02) Pesticides: Health Effects in Drinking Water
(400.03) Groundwater: What It Is and How to Protect It (400.04) Water and the
Soil (400.05) Nitrogen: The Essential Element (400.06)
These fact sheets can be obtained from Cornell University Distribution Center, 7
Research Park, Ithaca, NY 14850.
Acknowledgments: Illustrations were drawn by Michelle McDonald, and Mary Jane
Porter served as production assistant. Funding was provided by the New York
Farmers' Fund. Many individuals reviewed the initial drafts, including Cornell
University faculty members, northeastern Cornell Cooperative Extension agents,
and employees of the U.S. Environmental Protection Agency and the U.S.