&EPA National Pesticide Survey
Nitrate
What is
Nitrate?
How Does
Nitrate
Behave In
Soil and
Ground
Water?
How Does
Nitrate Get
into Ground
Findings of
the National
Pesticide
Survey
Wtr»t»
The U.S. Environmental Protection Agency (EPA) has completed its five-year
National Survey of Pesticides in Drinking Water Wells (NPS), a study of the presence
of 127 pesticides, pesticide degradates, and nitrate in community water system (CWS)
wells and rural domestic drinking water wells. Nitrate was the contaminant most
detected in the Survey. This fact sheet provides an overview of nitrate and its
potential health effects, a summary of the concentrations of nitrate detected in CWS
wells and rural domestic drinking water wells, and guidance on both treating and
preventing well contamination.
The method selected by EPA for nitrate analyzed samples for the combined
presence of nitrate and nitrite, which are reported as a single concentration of nitrate
measured as nitrogen. Therefore, the analytical results for nitrate in this Fact Sheet do
not distinguish between nitrate and nitrite.
Nitrate, typically found in soil and water, is a naturally occurring inorganic ion.
Nitrate also occurs naturally in a number of foods, particularly vegetables. The major
source of nitrate in cultivated soils is from inorganic fertilizers. Fertilizers containing
nitrogen are applied to soils to enhance plant growth and are necessary in the
synthesis of plant proteins. Other sources of nitrate in soil and water include septic
systems, animal wastes, plant residues, and fixation from the atmosphere.
Nitrate is normally more stable than nitrite and is therefore much more abundant
in the soil. Because nitrate is weakly retained by the soil, it is mobile and moves at
virtually the same speed as water through soil. Nitrate is very soluble in water and
has a very high potential to migrate through soil to ground water. Nitrate is not
volatile, meaning that it does not readily evaporate from water into the air. Once it
enters water, it is likely to remain there until it is used by plants or other organisms.
Among the major sources of nitrate in soil and water are agricultural and home
lawn and garden uses of nitrate fertilizers. Other nitrogen-containing fertilizers such as
manure, ammonium sulfate. and urea also contribute nitrate to soil and water.
AddUonal important sources of contamination by nitrate include the following:
runoff from fields treated with nitrogen fertilizer,
animal manure from feedlots, dairies, and poultry farms;
leaching from irrigated fields;
septic tank wastes; and
sewage sludge.
Nitrate (measured as nitrogen) was the most commonly detected anatyte in NPS
welts. Based on the results of the NPS, EPA estimates that nitrate is present, at or
above the analytical detection level of 0.15 mg/L used in the Survey, in about 49,300
(52.1%) CWS wells and 5,990,000 (57.0%) rural domestic wetis nationwide.
Considering the precision of the Survey, EPA estimates that the number of CWS wells
NPS NKrt
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What Health
Effects Might
Be Caused
by Nitrate in
Drinking
Water?
How is Water
Treated to
Remove
Contami-
nants?
6,700,000. Nitrate is measured in milligrams per liter (mg/L) which is equivalent to
parts per million (ppm). Nitrate concentration can be reported either as nitrogen (the
nitrogen portion of nitrate) or as nitrate ion (10 mg/L of nitrogen is equivalent to 45
mg/L of nitrate). The maximum concentrations of nitrate detected were 13 mg/L in
CWS wells sampled by the Survey and 120 mg/L in rural domestic wells sampled by
the Survey. The median concentrations of detectable nitrate in CWS wells and rural
Domestic wells nationwide was approximately 1.6 mg/L
EPA estimates that about 1,130 (1.2%) CWS wells and 254,000 (2.4%) rural
domestic wells nationally contain concentrations that exceed EPA's proposed
Maximum Contaminant Level (MCL) and Health Advisory Level (HAL) of 10 mg/L
MCLs are discussed more fully under Health Effects. EPA notified well owners and
operators within 24 hours when detections were above hearth-based guidelines or
standards. Considering the precision of the Survey, EPA estimates that the number of
CWS wells with detectable levels of nitrate above the MCL could be a low as 370 or as
high as 2,600, and the number of rural domestic wells could be as low as 122,000 or
as high as 464,000.
No/vCtnccr Effect*: EPA has set a regulatory level for nitrate (as nitrogen) in
drinking water at 10 mg/L This level includes a margin of safety to protect human
health. EPA believes that water containing nitrate at or below this level is acceptable
for drinking every day over the course of one's lifetime, and does not pose any health
concerns.
In infants, exposure to nitrate levels in excess of 10 mg/L may result in a blood
condition called methemoglobinemia Methemoglobinemia, also known as blue baby
syndrome, is characterized by a reduced ability of the blood to cany oxygen. This
could result in a severe oxygen deficiency, and could lead to death. Methemoglob-
inemia related to drinking water contaminated with nitrate has only been observed in
infants, especially those with gastrointestinal disorders, up to the age of 3 - 6 months.
Cancer effects: Data from laboratory studies are inadequate for EPA to determine if
nitrate can increase the risk of cancer in humans.
Standard: EPA sets enforceable standards for public water systems, called MCLs.
These regulatory standards set achievable levels of drinking water quality to protect
human health. The proposed MCL for nitrate (as nitrogen) is 10 mg/L (proposed as of
May 22,1989). EPA has also proposed MCLs for Nitrite (as nitrogen), 1 mg/L and for
both nitrate and nitrite (as nitrogen), 10 mg/L
Nitrate can be detected in drinking water by a laboratory using an EPA
method such as #353.2. If nitrate (as nitrogen) is detected in well water, and
confirmed by retesting to be above 10 mg/L consult your State or County health
officiate. They may advise periodic retesting to get an accurate overall picture of the
water quality because seasonal precipitation changes and changes in fertilizer use can
cause variations in the amount of chemicals found in drinking water wells. They may
also advise using an alternative drinking water supply (such as bottled water) on a
temporary basis (especially for infants), treating the water, or drilling a new or deeper
well. If you receive your well water from a community water system, and suspect that.
your water is contaminated, contact your State public water supply agency. Public
water suppliers are required to notify customers if the drinking water that they deliver
contains a contaminant that exceeds its MCL
You may also be able to treat your well water to remove nitrate and other
contaminants. Treatment technologies that are currently used to remove nitrate from
water include ion exchange, distillation, and reverse osmosis. These techniques are
not necessarily appropriate in every situation. Conventional coagulation and lime
softening are not effective treatment methods for the removal of this contaminant.
NPS Nitnt*
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How Can
Water
Contamina-
tion be
Prevented?
State or County hearth officials should be able to provide advice on the best approach
to follow.
Several steps may be taken to prevent nitrate from entering wells, such as
eliminating its direct entry through the well wall, drilling a new well, modifying or
reducing fertilizer use, improving management of animal wastes in feed lots and other
locations, property locating, installing and operating septic systems, or hooking up to
municipal sewage systems.
Eliminate Direct Entry Through the Well Wall
If nitrate is detected in well water, it may be entering the ground water through
the well itself rather than through the soil. If the well is old or poorly constructed, or if
there are visible cracks in the casing, obtain expert advice on whether or not
improvements can be made to the well. In addition, investigate simple methods of
capping the well or seaJing it at the surface to prevent entry. Do not conduct any
chemical mixing activities near the well and use check valves to prevent back
siphonage if you use well water to mix fertilizers (a spill could lead to direct
contamination of the well).
Drill a New Well
If the soil surrounding the well is the source of contamination, drilling a new or
deeper well may make sense if water can be drawn from a deeper, uncontaminatea
aquifer. Unfortunately, it often is difficult to know the quality of the ground water
without drilling or extensive testing. Seek expert advice before you drill.
Learn More about Fertilizer Ute and Proper Manure Management
If you or others Irving near you use fertilizers extensively or keep animals on the
land, you should consider attending training courses on how to reduce practices that
can degrade ground water quality. You may find that you can eliminate or lessen the
frequency or quantity of your fertilizer usage by choosing alternative methods.
Contact your State or County agriculture department for schedules and additional
information.
Properly Locate, Install, and Operate Septic Systems
Improperly located, installed, and operated septic systems are frequently
identified as the cause of ground-water contamination. Because local conditions and
system design, use, and maintenance vary greatly, It is difficult to take one single
action to ensure that your septic tank is not a source of ground-water contamination.
You may minimize the potential for contamination by observing the following general
rules:
• locate the septic system downgradient from nearby wells (the
minimum safe distance is generally 100 feet);
• take into account the type of soil in which the waste water will
drain;
• ensure that there is adequate distance between the bottom of the
drain field and the underlying water table;
• provide an adequately sized area for the drain field;
• switch drain fields annually if the system is provided with alternate
drain fields;
• ensure that the volume and type of discharges are compatible with
the design of the septic system;
• pump the septic tank regularly; and
• do not use solvents to clean drain pipes.
NPS NKnti
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Why Was the
National
Pesticide
Survey
Conducted?
Where to Go
for More
Information
Bibliography
EPA conducted the Survey to determine the frequency and concentration of
pesticides, pesticide degradates, and nitrate in drinking water wells nationwide and to
examine the relationship between the presence of pesticides in drinking water wells
and patterns of pesticide use and ground-water vulnerability. The Survey sampled
566 community water system wells and 783 rural domestic wells for 127 pesticides.
pesticide degradates, and nitrate. The wells were selected as a representative
statistical sample to provide nationwide estimates of the presence of pesticides and
nitrate in drinking water wells, and are not meant to provide an assessment of
pesticide contamination at the local, County, or State level.
This fact sheet is part of a series of NPS outreach materials, fact sheets and
reports. The following additional fact sheets are available through EPA's Public
Information Center (401 M Street SW, Washington, DC 20460, (202) 382-2080):
Sumy Da$lgn
Survey Anatytat
Quality A$turance/
Quality Control
Analytical Method*
Summary Remits
Fact Sheet for each
detected analyte
Project Summary
Gloatary
How SPA Will Ute
The NPS Results
Additional information on the Survey and on pesticides in general can be
obtained from the following sources:
U.S. EPA Safe Drinking Water Hotline
1-800-426-4791 (In Washington, DC (202) 382-5533)
Monday-Friday, 8.30 am to 4:30 pm Eastern Time
National Pesticide Telecommunications Network
1-800-858-7378
24 hours a day
U.S. EPA Office of Pesticide Programs (OPP) Docket
Public Information Branch (H7506C)
401 M Street, SW
Washington, DC 20460
Telephone: (703) 557-2805
National Technical Information Service (NTlS)
5285 Port RoyaJ Road
Springfield, VA 22161
(703) 487-4650
Information on regulation of
pesticides in drinking
water
Information on hearth
effects and safe
handling of pesticides
Background documents
for Survey (available
for review)
Copies of the
NPS Phase I Report
(available 1991)
and
NPS Phase II Report
(when available)
If you are concerned about the presence of pesticides and nitrate in your
private water well, contact your local or State health department. Other experts in
your State environmental agency or agriculture and health departments may also be
helpful to you. rf you receive your drinking water from a community water system and
have questions about your water quality, contact your local community water system
owner/operator or the State water supply agency.
Meteter Publications. Farm Chemicals Handbook. Ohio: Meister Publications, i 990.
U.S. Environmental Protection Agency. Hearth Advisory Summaries. January 1989.
U.S. Environmental Protection Agency. Nitrate/Nitrite Health Advisory. March 1987.
U.S. Environmental Protection Agency, Office of Ground-Water Protection, Septic Systems
and Ground-Water Protection: A Program Manager's Guide and Reference Book. Jury
1986. EPA 440/6-86-006.
U.S. Environmental Protection Agency, Office of Ground-Water Protection, Septic Systems
and Ground-Water Protection: An Executive's Guide, Jury 1986.
NPS NHnit
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