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Giardia
– Controlling a Waterborne Parasite
Despite efforts by the U.S. EPA to make drinking water safe,
disease-causing organisms, called pathogens, still remain
a threat in some areas. In particular, Giardia can cause outbreaks
of giardiasis, an intestinal illness that can cause nausea,
anorexia, fever, and severe diarrhea. The symptoms can last
for several days, and giardiasis can be treated with antibiotics.
If left untreated, the body will naturally rid itself of the
parasite within a few months in most cases. To reduce the
chances of outbreaks, EPA established an acceptable level
for Giardia in drinking water in the Surface Water Treatment
Rule, promulgated in 1989. In November 1998, the agency plans
on establishing regulations that further regulate the parasite.
* What is it?
* What does it do?
* How does it get into drinking water?
* Don't water treatment plants eliminate
it?
* Is it in well water?
* What is EPA doing to eliminate Giardia
in drinking water?
* What can you do?
What
is it?
Giardia is a pathogenic parasite that is commonly found in
lakes and rivers, particularly those contaminated by sewage
and animal wastes. The parasite exists as a cyst, an egg-shell-like
covering that protects the microorganism from such hazards
as chlorine, a disinfectant. The cyst also protects the microorganism
from destruction outside the host, leaving it viable in water.
When this water is ingested, viable cysts can infect their
new hosts.
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What
does it do?
Giardia causes giardiasis, an intestinal illness. When water
contaminated with Giardia cysts is ingested, stomach acid
dissolves the cyst and frees the microorganism inside. The
microorganism usually infects the upper intestinal tract and
causes discomfort. Although most people can recover from a
case of giardiasis, the illness can be life-threatening to
some people, such as infants, the elderly, pregnant women,
or those with compromised immune systems.
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How
does it get into drinking water?
Giardia is typically found in surface water bodies, like lakes,
reservoirs, rivers, and streams. It is found in human and
animal fecal matter, so water bodies that are contaminated
with sewage or animal waste likely contain Giardia. For this
reason, water sources near farms are particularly vulnerable
to Giardia contamination. Shallow aquifers that are recharged
by surface water may also be susceptible to Giardia contamination.
But generally, only surface water sources are affected by
the cyst. If you do not know where your drinking water comes
from, call your water utility and ask. Surface water sources
are much more likely to become contaminated with Giardia than
underground aquifers.
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Don't
water treatment plants eliminate it?
Current EPA drinking water standards require the removal or
disinfection of Giardia. The current national primary drinking
water standards require treatment plants to both filter and
disinfect water to ensure 99.9% of the Giardia cysts are removed
or disinfected. But sometimes the protective cyst prevents
water treatment plants from killing the microorganism with
disinfection. To effectively control Giardia, the cysts must
be physically removed from drinking water.
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Is
it in well water?
Giardia can be found in well water, particularly if the well
is located on a farm. But the most common sources of Giardia
are surface water sources, like rivers, streams, lakes, and
reservoirs.
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What
is EPA doing to eliminate Giardia in drinking water?
In 1989, EPA passed the Surface Water Treatment Rule. Among
other things, this rule regulates certain pathogenic microorganisms
in drinking water, including Giardia lamblia and viruses.
Water treatment plants must remove 99.9% of Giardia and 99.99%
of the viruses. In fact, the rule set a maximum contaminant
level goal (MCLG) for Giardia at zero. But this goal cannot
be achieved with cost-effective treatment technologies.
Unfortunately, the Surface Water Treatment Rule did not adequately
address the removal of pathogenic organisms from highly contaminated
source waters (i.e., 99.9% removal of Giardia from highly
contaminated water would still contain a significant amount
of the microorganism). For these reasons, among others, EPA
proposed to amend the Surface Water Treatment Rule in 1994.
In 1996, Congress amended the Safe Drinking Water Act, the
law on which all drinking water regulations are based. Part
of these amendments require EPA to take into consideration
the effects of drinking water contaminants on vulnerable populations,
such as infants, the elderly, pregnant women, and those with
compromised immune systems. Consequently, EPA is now seeking
public input into how to select a treatment technology to
reduce Giardia in drinking water. EPA plans on finalizing
the new Surface Water Treatment Rule in November 1998.
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What
can you do?
If you think your water may be susceptible to Giardia contamination,
or if you are concerned about the possible health effects
of contamination, EPA recommends you consider one of three
options:
1. Boil your drinking and cooking water for at least one minute.
2. Install a filter under your sink that is certified by the
National Sanitation Foundation to remove Giardia. The filter
cartridge should be a carbon block with micron size of 1.0
or smaller.
OMNI's CBF1 and CBF3 filters are NSF certified to remove
99.99% of the Giardia cysts from your drinking water.
3. Purchase bottled water, but be sure this water had been
adequately filtered or otherwise treated. This is a more expensive
and not necessarily effective option.
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