Joan Rose, Ph.D., is an Associate
Professor in the Department of Marine Sciences, College of Public
Health, University of South Florida. Her area of expertise is water
pollution microbiology. She has been involved in the
investigation of recent waterborne outbreaks of Cryptosporidium, and
she is well known for her participation in the NBC TV program
"Dateline" which focused on the Cryptosporidium outbreak in
Milwaukee. Dr. Rose has served on the National Academy of Sciences
committee and the Science Advisory Board for the EPA and was
recently invited to join the National Drinking Water Council. The
following is a synopsis of her presentation at a 1995 Conference in
In the U.S. we are
facing degradation of our waterways by pollutants and microbial
contaminants resulting in an average of one million cases of
waterborne disease per year. Microbial contaminants, such as
Giardia, Cryptosporidium, and the new Cyclospora, are causing major
outbreaks across the nation.
In the 1960's Giardia became a prevalent
contaminant of health concern that prompted the enactment of the Surface Water
Treatment Rule that stated that all surface water that may potentially be used
for drinking water must be filtered. Unfortunately, problems with Giardia,
viruses, newer protozoans (like Cyclospora) and especially Cryptosporidium, are
Chlorination has little effect on cysts and
protozoans like Cryptosporidium. We are also finding that merely filtering
surface water isn't solving the problem since most microbial outbreaks of this
sort are occurring in ground water sources (of all the waterborne outbreaks
between 1991-92, 77% occurred in wells). Even pristine water sources (which are
closed to human activity) are not safe from microbial contamination since
sources of microbial contaminants are not only human waste products, but also
Giardia can be killed by long contact with
chlorine, but Crypto is much more resistant. Filtration is the only effective
way to get Crypto out of the water. Often, unfortunately, "rapid filtration" at
the public utilities water treatment plants doesn't do the job, and Crypto makes
it through to the public's tap water.
Recently, a new cyst, Cyclospora, has made its
presence known. Like Crypto, it produces intestinal disorders and is resistant
to disinfection. Unlike Crypto, Cyclospora oocysts must be mature before they
are infectious (so, if the body clears the cysts before maturation, there will
be no infection). It is also larger in size than Crypto and is, therefore,
easier to filter out of the water.
Although most of the intestinal disorders caused
by microbial infection affect a large segment of the population only like a
stomach flu or traveler's diarrhea, over 5 million Americans (the
immunocompromised, the aged, infants, and pregnant women) are at a much greater
risk (possibly even of death). Emerging patterns of rainfall, sewage overflows,
and animal excrement are leading experts to believe that microbial outbreaks are
going to continue and probably worsen.
Filtration has become the focus for control of
these microorganisms. Disinfection had always been the major barrier for
control, but we are finding microorganisms that are resistant to disinfection.
Filtration has got to be the focus here.
The Risks of Microscopic
Organisms in Drinking Water
If you feel
that this article has been helpful please consider adding it as a
resource link on your website or blog!