Frequently asked questions about microtoxâ

Frequently Asked Questions about MICROTOX
for Drinking Water Surveillance

Q: What is the Microtox System?
Microtox toxicity testing technology is a biosensor-based measurement system for toxicity
and provides an effective way to monitor for either accidental or deliberate contamination of
water supplies. Microtox Test Systems are based upon the use of luminescent bacteria
known as Vibrio fischeri which produce light as a by-product of normal metabolism. Any
inhibition of normal metabolism, such as that caused by toxicity, results in a decreased rate of
luminescence. The higher the level of toxicity, the greater the inhibition of light production.

The Microtox Acute Toxicity Test is being used to monitor drinking water supplies in many
countries and major U.S. cities where either accidental or deliberate contamination is a
concern. The Test can be completed in as little as 15 minutes, allowing for a quick response
to changes in water quality.
The Microtox Test System quickly reveals any changes in the level of toxicity of drinking
water. This provides for an effective means of water supply surveillance when supplies
are monitored regularly at strategic points.
Microtox® Toxicity Test Systems are uniquely suited for drinking water surveillance because they provide rapid screening and confirmation results, which are cost-effective and easy to perform. With more than 500 peer-reviewed scientific articles and more than 1,700 instruments sold worldwide, the Microtox® Toxicity Test System is the standard for rapid toxicity screening and analysis. Q: Has the system been used before for drinking water surveillance during sensitive
Yes. The US Army Corps of Engineers and the Washington Aqueduct system are
currently using Microtox systems to monitor the drinking water that is supplied to the
Pentagon to protect the civilian and military personnel working there from the terrorist
threat of contaminated drinking water.
Also, during the Olympic Games in Atlanta in 1996 and in Los Angeles in 1984, in many cities
during the 1991 Gulf War, and again during the Democratic National Convention in Los
Angeles in 2000, Microtox systems were used for continuous surveillance of drinking water
treatment and distribution systems.

Q: What Chemicals does Microtox test for?
Nearly 20 years of scientific studies have documented the sensitivity of Microtox to
more than a thousand different simple and complex chemicals. Microtox responds to a
very broad range of toxicants and classes of chemical agents including metals,
pesticides, fungicides, rodenticides, chlorinated solvents, industrial chemicals, and
similar materials.
Table 1: Partial list of toxic compounds detected by Microtox Systems
Arsenic *
Mercury *
Sodium Cyanide *
Potassium Cyanide *
Aflatoxin *
Lindane *
Malathion *
Flouroacetate *
Parathion *
Cadmium *
* Indicates specific chemical and biological threats specifically identified by name by the US Air Force in the study “Chemical and Biological Warfare Threat: USAF Water Systems at Risk” Major Donald Hickman, US Air Force Counterproliferation Center, September 1999.
Q: Aren’t these chemicals difficult for a terrorist to obtain?

A: No. Terrorists need not be sophisticated to use these agents. Many of these
compounds are commonly used, inexpensive, and easy to obtain over the counter in
large quantities. Sodium cyanide is highly toxic in small doses and is easily obtainable
from numerous suppliers to the mining and metals industries. It is not possible to
prevent a terrorist from gaining access to these and other common compounds, but it is
possible to detect if they have been introduced into a city’s water system.
Q: Why not just test for specific chemicals?

A: Practical experience with wastewater pretreatment studies has shown that chemical-
specific measurements identify true toxicity in unknown samples only about 20% of the
time. While chemical-specific tests can be sensitive and precise, they are also very
narrow and will not detect toxicants for which the analyst is not specifically looking.
Unanticipated toxicants usually go undetected, because time, cost, and incomplete
knowledge prevent chemical-specific testing from being a practical screen for toxicity. In
addition, even when the chemical constituency of a sample is known in detail, its
effective toxicity cannot reliably be calculated; different chemicals in a complex sample
often work synergistically or antagonistically to increase or decrease toxicity. Chemical-
specific tests are most useful for identifying particular chemicals after a sample is known
to be toxic.

Q: Will Microtox detect the presence of organisms like salmonella in drinking water

A: Using the portable Deltatox system with its ATP detection capabilities, an analyst
can quickly determine the total ATP – Adenosine Triphosphate – in a sample. ATP is
present in all bacteria and other microorganisms and serves as an efficient marker for
microbial contamination of finished and source water samples. The assay is non-
specific in that it will not determine the species of the organism present but it will rapidly
provide an indication of contamination from microorganisms.
Using this ATP detection capability along with the toxicity detection capabilities of the
system provides for a very effective rapid analytical tool for emergency response
situations, allowing you to rapidly screen samples for chemical and microbial
Q: Can Microtox provide a clear “FAIL” indication, i.e., a test saying “DON’T DRINK

A: Yes. If the light loss caused by exposure to the sample is clearly outside the range of
acceptable error, the water is toxic and further testing to determine the cause is

Q: Is the system portable?
Yes. The Microtox Test can be performed either in a laboratory using a bench-top
instrument or in the field using the portable DeltaTox instrument. The portable
instrument is especially important for drinking water systems with remote drinking water
sources that are difficult to guard with security forces and conventional means.

Q: How does a drinking water system use Microtox?
A typical application by many drinking water treatment systems across the country
involves testing the water at the source, at the treatment plant, and at strategic points
along the distribution system. The sampling and analysis usually occurs from once to
multiple times per shift and samples are collected at numerous points such as the intake
from the water source (reservoir, river, etc.), various points throughout the treatment
process, before and after chlorination, and at key points in the distribution piping.


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