Number 05a
March 2013
Nitrates in Well Water
What are nitrates?
Nitrates occur naturally and are widespread in the
environment. They are produced by the oxidation
of nitrogen by microorganisms. Nitrates are
essential for plant growth and are present in all
vegetables and grains. Nitrates are colourless,
tasteless and odorless.
Nitrates should not be confused with nitrites.
Nitrites are mainly used as a food preservative,
especially in cured meats. Both nitrates and nitrites
can be a health hazard when consumed in food and
water.
How do nitrates get into well water?
Nitrates enter the ground water and make their way
into well water through many sources such as:
 agricultural activities (including over-
application of chemical fertilizers and animal
manure);
 wastewater treatment through septic systems or
leaking sewage lines;
 industrial processes;
 improperly functioning septic systems;
 motor vehicles; and
 some de-icing agents used at airports.
How do I know if there are nitrates in
my well water?
Since nitrates are colourless, tasteless, and
odorless, you cannot tell if you have nitrates in
your well water unless you test for it.
Nitrate levels in ground water may change over
time, especially after a heavy rainfall. High levels
(more than 10 milligrams per litre (mg/L) of
nitrates have been found in well water samples
throughout B.C., especially near heavily farmed
areas. In some cases, wells located near each other
may have different levels of nitrates, so you cannot
rely on test results from a neighbour’s well.
What are the health risks of high
nitrate levels?
Some evidence suggests that consuming high
levels of nitrates may be a health risk to pregnant
women, a developing fetus, babies under 6 months
of age, the elderly, and individuals with weakened
immune systems, or chronic heart, lung and blood
conditions.
In recent years, new studies have suggested there
can also be certain health risks for adults and
children who have had exposure to high levels of
nitrates.
Exposure to high levels of nitrates reduces the
amount of oxygen in the blood. This condition is
called methemoglobinemia. Babies under 6 months
are particularly at risk from drinking well water
high in nitrates. In severe cases, this can cause an
infant to turn a grey-blue colour, mainly around
the eyes and mouth due to the lack of oxygen in
their blood. Immediate medical attention is
necessary, as this serious condition can be fatal.
Babies who have diarrhea or a bacterial infection
are at greater risk of the harmful effects from high
nitrates levels.
What should I do if there is a
pregnant woman or baby in the
household?
Research continues on the effects of nitrates during
pregnancy. The safest choice for pregnant women
is to drink water that does not have high levels of
nitrates. To help keep your family safe you should:
 Have your well water tested for both nitrates
and coliform bacteria if there is an infant, a
pregnant woman, or a woman planning on
becoming pregnant in your household.
 Breastfeed your child if possible.
 Never feed your baby well water, or infant
formula mixed with well water, unless the well
water has first been tested safe for nitrates
levels. Ready-to-feed formula is recommended
if you are not breastfeeding and you do not have
a safe water source.
For more information on preparing infant formula,
see HealthLinkBC File #69b Formula Feeding
Your Baby: Safely Preparing and Storing Formula.
For more information on feeding infants, see
HealthLinkBC File #69c Baby’s First Foods.
How can I get my well water tested?
Testing of your well water for nitrates and
coliform bacteria can be done by a private
laboratory. Laboratories which provide this service
can be found in the yellow pages under
Laboratories - Analytical. Your local
environmental health officer may also be able to
give you a list of labs in B.C. that test drinking
water.
Most laboratory tests for nitrates give their results
in milligrams of nitrates, where the Guidelines for
Canadian Drinking Water Quality’s maximum
acceptable concentration for nitrates is 10 mg/L. If
laboratory test results give the level of actual
nitrate, rather than the level of nitrate(s) (i.e.
nitrate-nitrogen), then the Guidelines recommends
a maximum acceptable concentration of 45 mg/L
of nitrate.
If you get your water tested and are unsure how to
read the results, please call the environmental
health officer at your local health authority.
All wells should be tested for nitrates. For more
information on well water testing, see
HealthLinkBC File #05b Should I Get My Well
Water Tested?
What if my water is high in nitrates?
 commercially bottled water; or
 use an ion exchange or reverse osmosis
treatment system specifically designed to
remove nitrates, and where possible, should be
certified by NSF international or an accredited
agency.
It is important to note that boiling water will not
reduce or remove nitrates. Also, most counter-top
filtration units will not remove nitrates. There is no
substitute for having your water tested.
You should continually monitor your well water
for nitrates to make sure that your water is safe.
This should be done in addition to other
parameters such as free ammonia or total chlorine.
Shallow wells that are located in agricultural areas
are more likely to be contaminated with nitrates. It
is recommended that homeowners with these types
of wells test their water at least once a year, either
in the spring or fall, when concentrations are often
highest.
For more information
For more information on wells and quality well
water, see:
 The BC Ministry of Environment Nitrate in
Ground Water Fact Sheet at
www.env.gov.bc.ca/wsd/plan_protect_sustain/gr
oundwater/library/ground_fact_sheets/pdfs/no3(
020715)_fin2.pdf.
 Contact the environmental health officer at your
local public health authority (listed in the blue
pages of your phone book).
Homeowners that have nitrates test results
consistently above the acceptable concentrations
should consider the following:
 install a drinking water treatment device;
 use an alternative drinking water source; or
For more HealthLinkBC File topics, visit
www.HealthLinkBC.ca/healthfiles/ or your
local public health unit.
 relocate or drill a deeper well that has been
tested or verified and deemed to be a safe
supply.
Click on www.HealthLinkBC.ca or call 8-1-1
for non-emergency health information and
services in B.C.
It is especially important to consider the above
options if you are pregnant, have a baby under 6
months of age or have a health condition that puts
you at risk.
For deaf and hearing-impaired assistance, call
7-1-1 in B.C.
You should use 1 or more of the following water
sources for your drinking water:
Translation services are available in more
than 130 languages on request.
 water from a municipal distribution system;
 water from a nearby well that has been tested
safe for nitrates;