&EPA
United States
Environmental Protection
Agency
Off ice of Water (WH-550)
EPA 570/9-90-002
June 1990
Your Drinking Water:
From Source to Tap
EPA Regulations
and Guidance
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CONTENTS
Introduction 1
What Is the Source
of My Drinking Water? 2
What Kinds of Chemicals
or Other Contaminants
Might Be Present in My Drinking Water? 5
What Levels of These Contaminants
Are Cause for Concern? 7
Who Ensures That My Drinking Water Is Safe? 9
How Can I Check on
My Own Drinking Water Supply? 12
How Can I Get More Information?.. ..14
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INTRODUCTION
Safe drinking water is a resource
that often is taken for granted. It is
so abundant and inexpensive that
we fill our glasses without a second
thought about how the water got to
our taps. Each person uses approxi-
mately 168 gallons a day, with each
gallon costing less than 1716 of a
cent. We don't realize that our water
runs so clear only because we enjoy
one of the best water treatment sys-
tems in the world. And we don't
realize that water is a resource that
must be protected.
Drinking water has not always been
safe in this country. Less than a cen-
tury ago, serious illnesses such as
cholera and typhoid fever were
frequently transmitted by drinking
water. Then, in 1908, chlorine was
introduced as a disinfectant in U.S.
water supplies to control disease-
causing microorganisms. By mid-
century, the number of deaths from
typhoid fever and cholera had
dropped significantly.
Now that we have the technology to
protect our water supplies, disease
epidemics are rarely spread by
drinking water in this country. The
challenge of keeping our drinking
water safe, however, is far from
over. For example, water supplies
can be contaminated with naturaliy
occurring chemicals as well as with
manmade chemicals common to our
industrial society, such as herbicides
or pesticides. We have also
increased our ability to measure low
levels of chemicals in water. As a
result, we have become aware that
long-term exposure to some chemi-
cals, even at low levels, can poso .1
health risk and thus must be con-
trolled.
In response to these concerns, the
U.S. Congress enacted the Safe
Drinking Water Act in 1974. This
Act required the U.S. Environ-
mental Protection Agency (EPA) to
develop a national program to pro-
tect public water supplies. EPA was
also given the authority to establish
national standards for known or
suspected drinking water contami-
nants.
The Safe Drinking Water Act only
regulates water systems serving 25
or more persons on a regular basis
or systems with 15 or more service
connections. Private water sources
(for example, a private well) are not
regulated by the Federal govern-
ment.
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Purpose of This Pamphlet
The Safe Drinking Water Act is
designed to ensure that you have
clean water to drink. Most water
flowing from taps in the United
States is safe, but occasionally some
problems can occur — for example,
an accidental spill, problems with
the maintenance of a water treat-
ment facility, or ineffective treat-
ment resulting iii contamination.
This pamphlet is designed to
answer questions you might have
about your water, such as/WTiere
does it come from? How is it protected
from contamination? Topics that are
covered include:
• Sources of drinking water
• The kinds of chemicals and other
contaminants that can be found in
drinking water
• How scientists determine an
acceptable level for a chemical in
drinking water
• How the government establishes
laws and guidelines to limit
potentially dangerous chemicals
or other contaminants in water to
specific concentration levels
• What to do if you have questions
or doubts about your drinking
water
WHAT IS THE
SOURCE OF MY
DRINKING WATER?
Surface Water
versus Ground Water
About half the people in the United
States obtain their drinking water
from surface waters such as lakes,
rivers, and reservoirs. The rest get
their water from wells or springs
that are filled by ground water,
which is water that lies under-
ground in saturated layers of sand
or fractured rock. The water filters
down through the sand, soil, and
rock until it is stopped by a solid
barrier, such as a deposit of clay.
Water then collects in the spaces
between sand particles or in the
cracks and cavities in rocks. These
geologic formations are called
aquifers.
Recycling of Water Sources
Both surface and ground waters
undergo a cycle of loss and replen-
ishment (Fig. 1). Water evaporates
from surface bodies of water, or it
flows out — for example, from a
lake into a river into the sea. Atihe
same time, these surface bodies are
replenished by stream and river
inflow, rain, and melting snow. This
cycling of water protects our surface
water bodies by carrying away pol-
lutants. New pollutants, however,
can be carried into a body of water
by the same cycle.
Ground water also cycles, though at
a much slower rate than surface
waters. Because of the slowness of
this cycle, contamination of ground
water is extremely difficult to
reverse.
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RIVERS, STREAMS
GROUNDWATER FLOW
OCEAN
FIGURE 1
Surface Water Cycle
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Call Your Water Supplier
for Information
To learn whether your drinking
water comes from the surface or the
ground, your simplest option is to
call the company that supplies your
water (check your water utility bill
for a number). Questions you may
wish to ask include:
• Does my water come from surface
or ground water?
• If ground water, how deep is the
well?
• Are any sources of pollutants
nearby (for example, chemical
waste sites, industrial discharges)
that may threaten the purity of my
water?
• If so, what steps are being taken,
and by whom, to protect the water
from contamination?
Even if your water is from a private
well, a local water supplier could
provide useful information regard-
ing water quality in the area and
tilting options.
FIGURE 2
Sources of Drinking Water Contamination
SEPTIC
TANK
LEAKS
PRIVATE
WELL
WASTE
DUMP
SITES
GROUNDWATER PATH
CONTAMINANTS
F=n
H
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WHAT KINDS OF
CHEMICALS OR OTHER
CONTAMINANTS
MIGHT BE PRESENT IN
MY DRINKING WATER?
Minerals Naturally
Present in Water
All drinking water sources contain
minerals dissolved from the earth.
In moderate amounts, some of these
minerals are desirable because they
enhance the quality of the water (for
example, give it a pleasing taste). A
few, such as zinc, are beneficial
nutrients that contribute to your
good health when present in small
amounts. Other chemicals, however,
are undesirable above a certain
level, either because they cause bad
taste or odor (such as excess iron,
manganese, or sulphur) or because
they may be potentially harmful to
your health.
Chemical Pollutants
Water supplies can contain a variety
of chemicals that may pose a health
risk. These contaminants are usually
the result of human activity (Fig. 2).
Most effects of the chemicals on
human health are associated with
long-term, or chronic, exposure
rather than short-term exposure.
Some possible sources of surface
water or ground water contamina-
tion include:
• Leakage from waste disposal,
treatment, or storage sites
• Discharges from factories, indus-
trial sites, or si-wage treatment
facilities
INTENTIONAL
DISCHARGE
AND ILLEGAL
DUMPING
. I
HERBICIDE,
PESTICIDE,
AND FERTILIZER
L*~.1
Ft
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CHEMICALS TO ADJUST HARDNESS
CHEMICALS TO REMOVE SEDIMENT
FIGURE 3
Chemicals Added to
Drinking Water
CORROSION
CONTROL
DISINFECTANT
• Leaching and runoff from aerial
or land application of pesticides
and fertilizers on yards or fields
j
• Accidental spills of chemicals
• Leaching in the water distribution
system (e.g., lead from pipes or
solder in copper service connec-
tions)
• Illegal dumping of
chemical/industrial wastes
• Leakage from underground --tor-
age tanks
• Geologic formations or soils natu-
rally high in certain minerals/
chemicals
Microbiological Organisms
Many types of microorganisms are
present in your drinking water.
Those that cause a public health
concern, however, are primarily
associated with the intestine — for
example, certain kinds of bacteria,
viruses, or parasitic protozoans.
These organisms enter public water
supplies when the source water is
contaminated with human or ani-
mal wastes. It's also possible for
these organisms to enter the water
distribution system through faulty
cross-connections with wastewater
piping. The most common health
effects you might experience from
this type of contamination are gas-
trointestinal disorders (for example,
cramps and diarrhea).
Chemicals Intentionally
Added to Water
Certain chemicals such as disinfec-
tants are intentionally added to
drinking water (Fig. 3). The primary
reasons for treating water are to
inactivate contaminants such as
microorganisms that pose a health
risk and to improve the aesthetic
qualities of water. The most com-
monly added disinfectant is chlo-
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rine, which is used to kill infectious
organisms such as bacteria and
viruses. Disinfection with chlorine
or a similar chemical is essential to
prevent the outbreak of diseases
such as giardiasis, salmonellosis, or
dysentery.
Treating surface waters usually
involves the following steps: disin-
fection, coagulation (adding chemi-
cals to enhance removal of dis-
solved and suspended solids), floc-
culation (gentle stirring to clump
particles), sedimentation (gravita-
tional settling of heavier particles),
filtration (separating out lighter par-
ticles), and then a second disinfec-
tion step to inhibit microbial
regrowth in the distribution system
(Fig. 4). For groundwater supplies,
some systems may include a disin-
fection step, but most treatment is
primarily for taste and odor control.
Other chemicals besides those used
for disinfection or sediment
removal are sometimes added to
water. These are used to adjust the
hardness (which determines how
easily you can wash off soap lather)
or to control the corrosive action of
water on household pipes and
plumbing fixtures. The levels of
these chemicals improve the water
quality and are not considered
harmful to health.
WHAT LEVELS
OF THESE
CONTAMINANTS
ARE CAUSE FOR
CONCERN?
Experimental Studies
for Identifying Levels
of Concern
Information on the toxicity of con-
taminants usually comes from
experimental studies with laborato-
ry animals (Fig. 5). Sometimes infor-
mation is also available from obser-
vations of humans who have been
exposed to the chemical, either acci-
dentally or in the workplace. Scien-
tists use these studies to determine
the amount of a chemical that can
cause an undesirable health effect,
as well as the amount that does not.
From these data, they calculate the
highest level of that contaminant
that is acceptable in your drinking
water. These levels are set to protect
health and include a margin of
safety.
Identifying Contaminants
of Concern
The types of contaminants found in
your water depend on:
• Your geographic location
• The source of your water
• The treatment your water receives
* The effectiveness of that treatment
• The plumbing materials in your
home (as a source of lead)
iu**~ 1
Pi
»*•
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c
.
DISINFECTION
To Kill Infectious
Organisms
COAGULATION
To Facilitate Removal
of Impurities
FLOCCULATION
To Clump Particles
c
C1
l>
^=
SEDIMENTATION /FILTRATION
To Remove Impurities
DISINFECTION
To Inhibit Microbial Regrowth
TESTING
DISTRIBUTION
TO CUSTOMERS
FIGURE 4
Typical Steps in Drinking Water Treatment
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DATA FROM ANIMALS
HEALTH-
BASED
CRITERIA
OR
GUIDELINE
DATA FROM HUMANS
(Epidemiological Studies)
FIGURE 5
Development of Health-Based
Criteria (MCLGs) and Guidelines
(Health Advisories)
Just because a contaminant is in
your water, however, does not mean
you will experience adverse health
effects. That depends on the follow-
ing factors:
• The nature of the contaminant —
some are not hazardous even at
high concentrations while others
cause problems at much lower
levels; also interaction between
chemicals can alter the risk posed
by a single chemical
• The level of the contaminant —
many contaminants are found in
water at levels far below the con-
centration that would cause any
harm
• Your susceptibility
• How long you may have been
exposed to contaminated water
(for example, days, months, or
years)
WHO ENSURES THAT
MY DRINKING WATER
SUPPLY IS SAFE?
Laws and Guidelines Set by
the Federal Government
The states are working with EPA to
implement the Safe Drinking Water
Act, which was amended in 1986 to
cover an even wider range of con-
taminants. EPA sets the acceptable
standards for contaminants in
drinking water, and in most cases,
the states have the primary respon-
sibility for enforcing those stan-
dards or guidelines. States may set
standards for contaminants at levels
more stringent than those set by
EPA. In addition, states may regu-
late chemicals that are not regulated
by the federal government.
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Contaminant levels established by
EPA include (Fig. 6):
• Maximum Contaminant Level Goals
(MCLGs). The MCLGs are non-
enforceable health goals that serve
as the basis for the enforceable
standards. MCLGs are aspirational
goals based solely on an evalua-
tion of possible health risks and
exposure and provide a margin
for public safety. For chemicals
that may cause cancer in humans,
such as benzene, the goal is zero.
• Maximum Contaminant Levels
(MCLs). These levels are legally
enforceable standards that apply
to public drinking water supplies.
They are set as close to the
MCLGs as feasible, taking into
account available analytical
methods of detection and water
treatment capabilities as well as
the cost of achieving various con-
centration levels of contaminants.
• Health Advisories (HAs). Health
Advisories are nonenforceable
and provide guidance to public
health officials for unregulated
contaminants that may be found
in drinking water. HAs list con-
centrations of contaminants that
would be acceptable for exposures
of varying duration (one day, ten
days, longer-term, or lifetime).
The One-Day and Ten-Day Health
Advisories are primarily intended
to help public health officials eval-
uate the magnitude of a public
health risk resulting from an
accidentat'chemical spill or an
emergency contamination situa-
tion. The Longer-term and Life
time Health Advisories provide
guidance for persistent water
contamination situations. The
Lifetime Health Advisory is
derived in the same way as the
MCLG.
• Secondary Maximum Contaminant
Levels (SMCLs). SMCLs identify
the levels at which taste, odor, or
staining from chemicals in water
may become undesirable. They
are not based on health risks.
These standards are also not
enforced by EPA, but can be
enforced by the states.
• Individual states can also estab-
lish additional guidelines (such as
groundwater standards) that are
enforceable.
The regulations and Health Advi-
sories are conservative estimates
that provide a margin of safety
designed to protect even the
most sensitive members of the
population. EPA and the states
are continually developing and
revising the standards or guidelines
for contaminants of possible
concern in drinking water. The
values established are based on the
best scientific information available
at the time. To obtain a list of
standards and Health Advisories
see details on page 14.
Cooperation of EPA, States,
and Water Suppliers to Meet
the Regulations
Water supplied to you by public
water systems must meet all the
regulations established by EPA and
your individual state. Typical
SDWA State programs require
water suppliers to take the follow-
ing steps:
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MCLs
/ /
MAXIMUM
CONTAMINANT
LEVEL GOAL
(MCLG)
v v
) r
MAXIMUM
CONTAMINANT
LEVEL
(MCL)
(^CTICALITY)
ONE-DAY HEALTH ADVISORY
TEH-DAY HEALTH ADVISORY
LONGER-TERM HEALTH ADVISORY
LIFETIME HEALTH ADVISORY
SMCLs
SECONDARY
STANDARDS
FIGURE 6
Drinking Water Contaminant Levels Set by EPA
and Factors Influencing Their Derivation
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• Regularly test water in drinking
water supplies for the presence of
contaminants that could cause
negative health effects
• Maintain records of microbiologi-
cal and chemical test results
• Compare contaminant concentra-
tions to MCLs
• Notify the public through the
news media or a statement in
your water bill of any chemical
concentration that exceeds the
MCL and indicate the health sig-
nificance of the violation
The test records maintained by the
water suppliers are public informa-
tion. This protocol is designed to
help your state actively protect the
quality of your drinking water.
HOW CAN I CHECK ON
MY OWN DRINKING
WATER SUPPLY?
Gather More Information
Your water supplier, state health
official, regional EPA office, or state
agency responsible for regulating
water should be able to answer the
following questions:
• Does my water contain measur-
able levels of any pollutants of
possible health concern?
• Do the levels of the chemicals pre-
sent in my water meet all existing
federal and state regulations and
guidelines? Can I receive a copy
of recent test results for last year
or the previous few years?
• How often have requirements not
been met, and what is being done
to solve any problems? Has a vari-
ance or exemption been issued?
If your water is supplied by a utility,
you can gather a lot of information
before you decide to test your
water. On the other hand, if your
water is supplied by a private well,
you'll be able to gather less infor-
mation, and testing may be the only
way to determine your water's
quality.
Before you have your water tested,
ask local experts — water treatment
plant officials, the planning or zon-
ing board, and state and local health
and environmental agencies — for
advice concerning which contami-
nants should be evaluated. The
potential source of contamination
may help identify which contami-
nants to test for.
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Private wells may be especially sus-
ceptible to certain types of contami-
nation. If you use a septic tank to
treat your wastewater, a malfunc-
tioning system can contaminate
your well. Also, if you dispose of
hazardous household substances
(such as pesticides or paints) down
your drain, your septic tank can
malfunction and contaminate your
well. In rural areas, seepage and
runoff of fertili/ers and pesticides
can also contaminate private wells.
Test Your Water
Choose an EPA-certified indepen-
dent lab, and be sure to follow the
sampling and preservation tech-
niques the lab recommends for tak-
ing water samples. If the samples
are not collected, stored, and ana-
lyzed correctlv, the results mav be
.
misleading. For lab recommenda-
tions and cost estimates, contact
your local, county, or state public
health department or your state
agency responsible for regulating
the quality of drinking water.
Interpret the Results
of Your Test
Contact your water supplier, the
agency in your state that regulates
drinking water, or EPA for assis-
tance in interpreting the results ot
tests on your water supply. These
agencies will compare the concen-
trations reported in your test with
appropriate MCLs, HAs, or state
guidance levels.
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HOW CAN I GET MORE INFORMATION?
You can get more information about the quality of your drinking water
from your local water supplier, your state health department, the agency in
your state responsible for drinking water, or your regional EPA office. The
phone numbers of the EPA regional offices an- provided on the next page.
You can also call the EPA Safe Drinking Water I lotline with this toll-free
number: l-8W~12
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U.S. EPA Region 1
Connecticut, Maine, Massachusetts,
New Hampshire, Rhode Island,
Vermont
John F. Kennedy Federal Building
Room 2203
Boston, MA 02203
(617) 565-3610
U.S EPA Region 2
New Jersey, New York, Puerto Rico,
Virgin Islands
26 Federal Plaza Room 900
New York, NY 10278
(212) 264-1800
U.S. EPA Region 3
Delaware, District of Columbia, Mary-
land, Pennsylvania, West Virginia,
Virginia
841 Chestnut Street
Philadelphia, PA 19107
(215) 597-8227
U.S. EPA Region 4
Alabama, Florida, Georgia, Kentucky,
Mississippi, North Carolina, South
Carolina, Tennessee
345 Courtland Street NE
Atlanta, GA 30365
(404) 347-2913
U.S. EPA Region 5
Illinois, Indiana, Michigan, Minnesota,
Ohio, Wisconsin
230 South Dearborn Street
Chicago, IL-60604
(312) 886-0245
U.S. EPA Region 6
Arkansas, Louisiana, New Mexico,
Oklahoma, Texas
1201 Elm Street
Dallas, TX 75270
(214) 655-7160
U.S. EPA Region 7
Iowa, Kansas, Missouri, Nebraska
726 Minnesota Avenue
Kansas City, KS 77101
(913) 551-7032
U.S. EPA Region 8
Colorado, Montana, North Dakota,
South Dakota, Utah, Wyoming
One Denver Place-Suite 1300
999 18th Street
Denver, CO 80202-2413
(303) 293-1430
U.S. EPA Region 9
Arizona, California, Hawaii, Nevada
1235 Mission Street
San Francisco, CA 94103
(415) 705-2111
U.S. EPA Region 10
Alaska, Idaho, Washington, Oregon
1200 Sixth Avenue
Seattle, WA 98101
(206) 442-1631
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EPA Region Phone Number
1 (617) 565-3610
2... , (212)264-1800
3 (215) 597-8227
4 „ (404) 347-2913
5 ..„. ....(312) 886-0245
EPA Region Phone Number
6 ...........(214)655-7160
7 .,.,.....(913)551-7032
8 ,,.......(303) 293-1430
9 (415)705-2111
10 ........(206)442-1631
State Region
Alabama 4
Alaska 10
Arizona 9
Arkansas 6
California 9
Colorado 8
Connecticut 1
Delaware 3
District of Columbia 3
Florida 4
Georgia 4
Hawaii 9
Idaho 10
Illinois 5
Indiana 5
Iowa 7
Kansas 7
Kentucky 4
Louisiana 6
Maine 1
Maryland 3
Massachusetts 1
Michigan 5
Minnesota ^ 5
Mississippi 4
Missouri 7
Montana 8
Nebraska 7
State Region
Nevada 9
New Hampshire 1
New Jersey 2
New Mexico 6
New York 2
North Carolina 4
North Dakota 8
Ohio 5
Oklahoma 6
Oregon 10
Pennsylvania 3
Rhode Island 1
South Carolina 4
South Dakota 8
Tennessee 4
Texas 6
Utah 8
Vermont 1
Virginia., 3
Washington 10
West Virginia 3
Wisconsin 5
Wyoming 8
American Samoa 9
Guam 9
Puerto Rico 2
Virgin Islands „ 2
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