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Pesticides In
Drinking-Water Wells
This booklet is intended for
people who drink water that
comes from a well and who are
concerned that pesticides may be
present in their drinking water.
The booklet provides a step-by-step
explanation of how pesticides can
enter drinking-water wells, the
types of health concerns that
pesticides can pose, advice on
testing your water supplies, and
actions that can be taken if
contamination is found. Sources of
further information and assistance
are listed at the back of the
booklet.
Nearly half of all Americans get
their drinking water from private
or community wells that tap
ground water. Our dependence on
ground water to meet drinking
water needs is growing.
Withdrawal of ground water is
increasing at twice the rate of
surface water, and this trend is
expected to continue. In some rural
areas, ground water accounts for
up to 95 percent of the water used
for domestic purposes.
Until the late 1970s, it was
generally believed that ground
water was fairly well protected
from pesticide contamination by
layers of topsoil, subsoil, rock, and
clay. Nevertheless, pesticides can
enter ground water. When that
happens, there may be a potential
risk to the health of those who
drink and use that water.
In response to this potential
threat, the U.S. Environmental
Protection Agency (EPA) has
undertaken a number of activities.
The pesticides EDB and DBCP have
been banned based on health
:oncerns and evidence that they
leach into ground water; regulatory
measures are under development
for Aldicarb; and in 1988, EPA
proposed a strategy for
"Agricultural Chemicals in Ground
Water." Numerous drinking water
standards and guidelines are being
established for pesticides. In
addition, in a major effort to
determine the extent of the
problem of pesticides in drinking
water wells, EPA has undertaken a
National Pesticide Survey of
drinking water wells.
Ground water is the vast underground
accumulation of water reservoirs that
supplies wells and springs. Geologic
formations containing ground water are
called aquifers.
Bedrock
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What Are Pesticides?
How Are They
Regulated?
A pesticide is a chemical
substance used to kill or
control a pest. "Pest" is a simple
catchall term that includes
undesired insects, weeds, rodents,
fungi, bacteria, and other
organisms. Thus, the term
"pesticides" includes insecticides,
herbicides, nematicides, acaracides,
rodenticides, and fungicides.
Pesticides are regulated by the
federal government as well as by
the states. At the federal level,
pesticides are regulated by EPA
under the Federal Insecticide,
Fungicide, and Rodenticide Act
(FIFRA). Under FIFRA, EPA
registers thousands of pesticide
products for a multitude of uses in
and around homes and buildings,
on trees and shrubs, on golf
courses, and for agricultural pest
control. No pesticide may be
legally sold or used in the United
States unless its label bears an EPA
registration number and
establishment number.
If EPA approves the use of a
pesticide, the approval extends
only to specific uses. The
pesticide's label explains where and
how the pesticide may be used. A
number of pesticides are registered
and labeled as "restricted use"
pesticides. Only certified
applicators may use these
materials.
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Pesticides are subject to extensive
scientific testing before being
registered for the first time to
ensure that, when used according
to label directions, they will not
present unreasonable risks to
human health or the environment.
EPA reserves the right to require
additional data at any time if new
information raises questions about
the pesticide's health or
environmental effects. FIFRA also
requires the re-registration of
pesticides first registered before
today's health and environmental
tests were required and before
pesticides were known to leach
into ground water. Using current
scientific standards, EPA is
re-examining health and
environmental safety information
for the approximately 600 major
active ingredients contained in
some 25,000 registered pesticide
products.
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tsfe, , AMteprfa^eas fertnd Jn
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othej>
states'. -,' '' -'
In Horida, mpre than 1900 weHs
have feeen shiit'down a& drinking
water sources because of • s
canteminationt»y Etl^te^ ,,
Dibromicle r oxiraately
one-quarter of the tisaMe
water,
A number of slates,
Califomiaj Florida, Maryland,
Minnesota^ Iowa, Mew York,
Washington, and Wisconsin,
undertaken studies of pesticides in
ground water. In 1985 EPA
estimated that at least 17
pesticides have been detected in
the ground water of 23 states as a
result of agricultural practices. In
1988, EPA reported that normal
agricultural use had apparently
led to residues of 46 different
pesticides in the ground water of
26'states: -''••••'•'• • . _ ••'••'• - ..
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How Do Pesticides
Get Into
Drinking-Water Wells?
Pesticides can enter ground
water both directly and
indirectly. Direct contamination
may occur from pesticide spills
around a poorly sealed well,
back-siphoning during spray tank
filling or chemigation (application
of pesticides through irrigation
systems), or improper storage and
disposal of pesticides or pesticide
containers. Indirect contamination
can occur when pesticides move
down through the soil into the
ground water. This may occur in
pesticide mixing areas or disposal
areas, or as a result of normal
application.
The extent to which
ground-water contamination can
occur as a result of normal crop
application depends on a variety of
factors: the type of pesticide used,
how the pesticide is applied
(application method, frequency,
and quantity), the characteristics of
the soil, and the geology of the
area. These factors, working singly
or in combination, will determine
how quickly the pesticide will
move through the soil and how
fast it will break down. The best
way to determine whether
pesticides have entered a water
supply is to take samples of the
water and have them tested in a
laboratory.
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Do Pesticides
In Drinking Water
Pose A Health Concern?
Pesticides can be harmful to you
if you are exposed to a
sufficient amount. Most people are
exposed to some pesticide residues
in food products. In addition,
people who use and handle
pesticides may be exposed to them
through breathing in pesticide
fumes or through skin contact.
Pesticide levels in drinking water
normally result in a much lower
exposure than exposure through
food or through handling pesticide
products. There are three ways in
which you can be exposed to
pesticides in drinking water:
• by ingestion—either by drinking
the water directly or eating foods
cooked with the water;
• by breathing in pesticide fumes
in the shower or when cooking or
washing; and
• by absorbing the pesticides
through the skin during
showering, swimming, or washing.
The degree to which pesticides
may affect the human body
depends on:
1. The toxicity of the
pesticide—Pesticides can cause a
range of possible harmful effects,
extending from a mild headache to
skin rashes to long-term effects on
internal organs, cancer, and death.
Pesticides diluted in water are
much less dangerous than the pure
compound; however, even minute
quantities of some chemicals in the
water may be cause for concern.
2. A person's exposure to the
pesticide—Exposures are based
upon the amount of the pesticide
in the water, the amount of water
to which a person is exposed, the
weight of the person, and the
length of time the person is in
contact with this water.
3. The health status of the
individual—People with health
problems, older people, infants and
children, and pregnant women
may be more susceptible to
pesticide hazards than the general
population.
What this means is that
pesticides may or may not pose
different types of health risks,
depending on the circumstances.
Different pesticides have different
effects on humans. Moreover,
exposure to a small amount of a
pesticide over a long period of time
can have a different effect than a
one-time exposure to a large
amount of a pesticide.
Further more, certain exposures of
pesticides in drinking water may be
too high for children but acceptable
for adults. These different
situations call for different risk
assessments and different types of
remedies.
Because there are so many
factors involved in considering the
risks posed by each pesticide, EPA
has developed technical guidance
documents that provide detailed
assessments for particular
pesticides.
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EPA's
Health Advisory
Guidance
EPA has developed guidance
documents called Health
Advisories to assist federal, state,
and local officials in responding to
the contamination of drinking
water by pesticides and other
chemicals. The Health Advisory
documents contain information on
health risks and treatment
technologies, and are updated by
EPA's Office of Drinking Water as
new information becomes available.
The Health Advisory documents
specify Health Advisory levels,
which represent the concentrations
of a contaminant in water that may
safely be consumed over a specific
time period. EPA sets Health
Advisory levels for short-term
exposures such as one day and ten
days, longer-term exposures of
greater than ten days up to several
years, and lifetime exposures.
These Health Advisory levels are
based on health effects (other than
cancer) that were found in animals
given high doses of the pesticides
in laboratory studies.
For pesticides believed to cause
cancer in humans, EPA does not
calculate a Lifetime Health
Advisory level. Instead, EPA
calculates the increased risks of
cancer that are associated with
different concentrations and
exposures to the pesticide. The
risks that are typically presented in
a Health Advisory document range
from an increased risk of 1
additional cancer case in a
population of 10,000 people
exposed to the pesticide, to the risk
of 1 additional cancer case in a
population of 1 million people
exposed. For more information on
Health Advisories, contact the Safe
Drinking Water Hotline at
1-800-426-4791.
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"Is My Well Water Safe Testing
To Drink?" And Retesting
Usually—yes! Sometimes,
however, there is no simple,
clear-cut answer. Detection of a
small amount of a pesticide in your
water sample may serve as a
warning or cautionary signal, like a
yellow traffic light.
For example, if water samples
from your well consistently show 5
micrograms of Atrazine per liter,*
and the Lifetime Health Advisory
for Atrazine is 3 micrograms per
liter, this would not necessarily
mean that any harm would occur,
because Health Advisories have a
built-in margin of safety. Your risk
of adverse health effects would
depend on your health, how long
you will be exposed to the water,
and whether any additional
contaminants might be present.
Exposure to several pesticides or
other hazardous chemicals together
may multiply the effects of any
single chemical.
In such a situation, EPA would
recommend that you consider
taking action to assure a safer
water supply. A first step would be
to contact your state or county
officials for advice. The Health
Advisories would serve as
guidelines to help both you and
the experts you consult determine
how to respond in your individual
situation.
* Micrograms per liter are the units of
measurement for contaminants in water,
equivalent to parts per billion.
Testing drinking water for
pesticides is more complex than
routine tests for minerals or
bacteria. Pesticide testing requires
more specialized equipment and
training, since pesticides generally
occur only at very low levels in
ground water. If you are concerned
about pesticide contamination of
vour well, first contact your state
or county officials and find out
whether contamination problems
have been reported by other
residents in the area. Also find out
which pesticides and fertilizers are
commonly used nearby. If
contamination has been confirmed
in your area, you should have your
well tested.
For advice on testing services,
contact your state or county
officials, state university
laboratories, or your EPA Regional
Office (listed at the back of this
booklet). Be sure to obtain the
services of a certified testing service
or laboratory. Know the costs
beforehand! Costs for water
analysis for pesticides vary from
one commercial laboratory to the
next. For analysis of a single water
sample for one or two pesticides, a
laboratory may charge between
$100 and $150. The cost per sample
is usually somewhat less if several
water samples are analyzed at the
same time. The testing cost for
nitrates is about $30.
Many commercial laboratories
offer a standard screening test for a
number of pesticides and related
compounds regulated under the
Clean Water Act; before
proceeding, you should check with
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Taking
Action
your state or county officials as to
whether it is appropriate to test
your water for these chemicals.*
If your well has been tested and
pesticides have been found, EPA
recommends that you have the
well retested. This is because
changes in rainfall, in pesticide
use, or in water withdrawals from
your well or wells nearby can cause
wide variations in the levels of any
pesticides found in your well at a
specific time. Retesting may
provide you with a better overall
picture of your water quality.
Upon retesting, if a pesticide is
detected in your well water at or
below EPA's Health Advisory level,
you should continue to have your
well checked periodically. Ask your
state or county health officials for
advice on how often retesting
should be done. If a pesticide is
present above the Health Advisory
level, you should consult your state
or county health officials for advice
on action to limit your exposure to
the pesticide.
Finally, if you have reason to
believe that your neighbors share a
ground-water source containing
pesticides, they should be informed
of the potential risks and
encouraged to have their wells
tested.
'Commercial water testing laboratories
may not be able to repeat exactly the
procedures used to analyze water samples
for the National Pesticide Survey. EPA
developed these procedures specifically
for the survey in order to test for a large
number of pesticides simultaneously.
However, most laboratories should be
able to retest your water for any specific
pesticides that may have been found in
your well water.
There is no economical way to
clean up contaminated water
while it is in the ground. Instead,
your options for taking action will
likely be to treat the water, dig a
new or deeper well, or switch to an
alternative water supply.
Your choice among these options
should be based on an expert
evaluation of the source of the
problem and a realistic assessment
of the costs involved in each
option. You may be able to connect
with a public water supply. In
some cases, digging a new or
deeper well may be a reasonable
solution. In other parts of the
country, this may be infeasible
and/or extremely costly. EPA
suggests that you proceed only
with the advice of impartial
experts, such as your state or
county health officials.
Treating
The Water
It may be possible to treat your
drinking water to reduce the
pesticides and nitrates present.
However, not all available
treatment techniques will be
effective in reducing particular
pesticides. EPA's Health Advisory
Summaries identify treatment
methods that may be effective for
each individual pesticide.
The most common types of home
treatment devices currently on the
market are briefly described in the
box on the next page. Prices shown
are for 1988, and may vary by
geographic region. The treatment
systems require periodic
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monitoring and maintenance to
ensure the unit's efficiency. Annual
operating costs for a household can
range from $30 to $350. When
looking to purchase or lease home
water treatment equipment,
research the products available.
Check performance capabilities,
warranty, maintenance provisions,
and general operation. Deal with a
professional and be an educated
consumer!
Some community water systems
also use treatment methods,
including reverse osmosis, ion
exchange, oxidation, and air
stripping, to treat contaminated
water. More commonly, if there is
contamination, community water
systems will close down the
contaminated well, or blend the
water with water from other wells
until acceptable water quality is
reached, or use conventional
treatment methods involving
coagulation, sedimentation, and
nitration to remove particulates and
other contaminants.
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Digging
A New Well
Digging a new or deeper well may
make sense if you are able to draw
water from a deeper, clean aquifer.
Unfortunately it often is difficult to
know the quality of the ground
water in different aquifers without
drilling or extensive testing.
It is highly recommended that
expert advice be sought before you
drill! Your county extension agent,
or officials from your state
geological or water survey or
environmental agency can advise
you on whether the pesticides in
your water are widely used in the
county and are likely to be
contaminating the aquifer. Local
well drillers can advise you on the
feasibility of installing a new or
deeper well.
The cost of a new well will
depend on the depth of the well,
the materials used to construct the
well, and the installation method.
An estimated cost of a new well is
between $3.50-$4.50 per inch
diameter per foot of depth, plus
casing and pump costs. (This
estimate is based on a well up to 8
inches in diameter and up to 300
feet deep; costs will be higher if
these dimensions are exceeded.)
Try to get more than one estimate
before proceeding.
Alternative
Water Sources
What else can you do? Two other
possibilities are purchasing bottled
water and hooking up to a public
water supply. Sometimes bottled
water is a useful temporary
alternative until a new permanent
water supply can be secured. The
cost of bottled water in 1988 was
about $7 to $15 per week for a
family of four, assuming each
person used 2 liters per day for
drinking water only. The cost to
hook up to a public water supply
will depend on the distance to a
water main, the housing density in
the area, and water payments.
Households connected to public
water systems may need to pay a
service charge for their water.
Eliminating
Direct Entry Of
Pesticides
Through The Well
It is possible that if pesticides are
contaminating your well water,
they are entering the ground water
through the well itself rather than
through the soil. If the well is old
or poorly cemented or if there are
visible cracks in the casing, you
may wish to obtain expert advice
on whether improvements to the
well are possible. Simple methods
of capping the well or sealing it at
the surface could prove effective in
eliminating further contamination.
In any case, if you use well
water to mix large amounts of
pesticides, no mixing activities
should be done near the well, since
a spill might lead to direct
contamination of the well. If you or
others living near you use
pesticides extensively, you should
consider attending training courses
in pesticide use given by your state
or county agricultural department.
10
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Where Can I Get
More Information?
Following is a sampling of
publications and a partial list of
organizations that may help you
obtain more information. Please
note that these lists are not
comprehensive and are not
necessarily endorsed by EPA.
Publications
"A Drop to Drink." Bruce
Webendorfer. Country Journal.
September 1988.
"Chemical Risk: A Primer."
Information Pamphlet. American
Chemical Society Department of
Government Relations and Science
Policy, 1155 16th Street NW,
Washington, DC 20036. 1984.
"Citizen"s Guide to Pesticides"
and "Citizen's Guide to Drinking
Water." U.S. Environmental
Protection Agency, 401 M Street
SW, Washington, DC 20460. Free.
"Drinking Water: A Community
Action Guide." Concern, Inc. 1794
Columbia Rd. NW, Washington,
DC 20009. 1988. $3.00
"Groundwater & Environmental
Pollution Self-Help Checklist for
Farmsteads and Farm Fields" and
"Protecting our Groundwater, a
Grower's Guide," available from
your state or county Farm Bureau
office.
"Guidance Document on the
Management of Pesticides in
Groundwater." Office of Drinking
Water, U.S. EPA. 401 M Street
SW, Washington, DC 20460.
Draft, September 1988. Free.
"Is the Water Safe to Drink?"
Consumers Union. 256
Washington Street, Mt. Vernon,
NY 10553. 1987. $16.00.
"Pesticides and Groundwater: A
Health Concern for the Midwest."
Freshwater Foundation. 2500
Shadywood Road, Box 90,
Navarre, MN 55392. 1987.
"Pesticides in Groundwater:
Background Document." U.S.
EPA. 401 M St. SW, Washington,
DC 20460. 1986. Free.
"Protecting Groundwater: A
Guide for the Pesticide User."
Slide Set Storyboard and Manual
for Instructors. Keith S. Porter and
Michael W. Stimmann. 468
Hollister Hall, Cornell University,
Ithaca NY 14853. Sponsored by
USDA and U.S. EPA. May 1988.
$75.00.
"Safety on Tap: A Citizen's
Drinking Water Handbook."
League of Women Voters
Eduction Fund. 1730 M Street
NW, Washington, DC 20036. 1987.
$7.95.
"Testing for Toxics: A Guide to
Investigating Drinking Water
Quality." R. Wilson. U.S. Public
Interest Research Group. 215
Pennsylvania Ave. SE,
Washington, DC 20003. 1986.
$5.00
Organizations
American Public Health
Association, 1015 15th Street NW,
Washington, DC (202) 789-5600.
American Water Works
Assocation, 6666 West Quincy
Avenue, Denver, CO 80235 (303)
794-7711.
League of Women Voters, 1730 M
Street NW, Washington, DC (202)
429-1965, and local chapters.
11
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National Agricultural Chemicals
Association, 1155 15th Street NW,
Washington, DC (202) 296-1585.
National Coalition Against the
Misuse of Pesticides, 530 7th
Street SE, Washington, DC (202)
543-5450.
Natural Resources Defense
Council, 122 East 42nd Street NY,
NY 10168 (212) 949-0049.
National Rural Water Association,
P.O. Box 1428, Duncan, OK 73534
(405) 252-0629.
National Water Well Association,
6375 Riverside Drive, Dublin, OH
43017(614)761-1711.
Water Quality Association, 4151
Naperville Road, Lisle, IL 60532
(312) 369-1600.
Contacts
State or County Health
Department
State Department of Agriculture
State Pollution Control or
Environmental Protection Agency
County Extension Office
Soil Conservation Service District
Office
EPA Regional Office
For further information on treatment technologies, drinking water
quality, and EPA's Health Advisories, call toll-free, Monday thru
Friday, 8:30 A.M. to 4:30 P.M. E.S.T:
EPA's Safe Drinking Water Hotline
1-800-426-4791
(in Washington, D.C., call 382-5533).
Information on the health effects of pesticides and pesticide
poisonings is available toll-free, 24 hours a day, from:
National Pesticide Telecommunications Network
1-800-858-7378
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EPA Regional Offices and States Covered
EPA Region 1
JFK Federal Building
Boston, MA 02203
(617) 565-3424
Connecticut, Massachusetts,
Maine, Neu' Hampshire,
Rhode Island, Vermont
EPA Region 2
26 Federal Plaza
New York, NY 10278
(212) 264-2515
Neu< Jersey, Neu' York,
Puerto Rico, Virgin Islands
EPA Region 3
841 Chestnut Street
Philadelphia, PA 19107
(215) 597-9370
Delaware, Maryland,
Pennsylvania,
Virginia, West Virginia,
District of Columbia
EPA Headquarters
401 M Street S.W.
Washington, D.C. 20460
(202) 382-4454
EPA Region 4
345 Courtland Street, N.E.
Atlanta, GA 30365
(404) 347-3004
Alabama, Florida, Georgia,
Kentucky, Mississippi, North
Carolina, South Carolina,
Tennessee
EPA Region 5
230 South Dearborn Street
Chicago, IL 60604
(312) 353-2072
Illinois, Indiana, Michigan,
Minnesota, Ohio, Wisconsin
EPA Region 6
1445 Ross Avenue
Dallas, TX 75202
(214) 655-2200
Arkansas, Louisiana, New
Mexico, Oklahoma, Texas
EPA Region 7
726 Minnesota Avenue
Kansas City, KS 66101
(913) 551-7003
Iowa, Kansas, Missouri,
Nebraska
EPA Region 8
One Denver Place
999 18th Street, Suite 1300
Denver, CO 80202-2413
(303) 293-1692
Colorado, Montana, North
Dakota, South Dakota, Utah,
Wyoming
EPA Region 9
75 Hawthorne Street
San Francisco, CA 94105
FTS 8-848-1305
DDD (415) 744-1305
Arizona, California, Hawaii,
Nevada, American Samoa,
Guam, Trust Territories of the
Pacific
EPA Region 10
1200 Sixth Avenue
Seattle, WA 98101
FTS 8-399-1107
DDD (206) 553-1107
Alaska, Idaho, Oregon,
Washington
United States Environmental Protection Agency
Regional Organization
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