The Great Lakes is home to some 30 million people and 80
Global transportation:  The food supply comes from all
percent of the shoreline is privately owned.  Of the 31 Areas
over the world, thus leading to a distribution of
of Concern, 61 percent are impaired for swimming and 29
pathogens (i.e. Cyclospora) and people are much
more mobile and can transverse the globe in less than
percent impaired for drinking water, respectively.  The
24 hours, bringing infections with them.
factors influencing the potential public health risks
associated with water quality impairment and microbial
contaminants are no doubt at play in this basin.
Antibiotic resistance:  Due to the widespread applica-
tion of antibiotics in medicine and in agriculture,
7.6
antibiotic resistance is spreading.  The World Health
Waterborne pathogens can pose significant threats to
Organization has recently reported (WHO 2001)  that
aquatic ecosystems and diverse water supply needs for
increasingly drug-resistant infections throughout the
drinking, recreation, agriculture and aquaculture through-
out the Great Lakes region.  Instead of attempting to directly
world are threatening to make once-treatable diseases
detect the presence of many possible pathogens in water,
incurable (http://www.who.int/emc/amr.html).
efforts to monitor the microbial quality of water have largely
Zoonotic transmission:  More animals and changes in
focused on detecting the presence of fecal indicator micro-
agricultural practices may lead to greater chances for
organisms such as total coliform bacteria or Escherichia coli.
microbial transmission and spread from animals to
At present, the approach for making many microbial water
humans.
quality decisions in the Great Lakes region is based upon use
of fecal bacteria indicator tests; the ability to culture fecal
Evolution of pathogens:  RNA viruses for example,
bacteria in the laboratory; and the use of periodic water
during replication are lack repair mechanisms and can
sampling regimes. While this can be a practical approach to
evolve quickly.
a difficult challenge, it is increasingly recognized as being
inadequate to ensure the safety of water supplies.
Improved diagnostic tools:  Diseases previously not
recognized or microorganisms that are not culturable
Existing microbiological indicators such as total coliforms
can now be studied through the use of powerful
have been shown at times to be poor indicators of fecal
molecular tools.
contamination. While the coliform E. coli is recognized as a
better indicator of fecal pollution, its ecology in aquatic
ecosystems is often different from other waterborne
The factors described above apply to the growing list of
pathogens such as viruses and protozoa. The differences in
waterborne pathogens.  In the Great Lakes there are a
persistence, means of transmission, or susceptibility to
number of other factors associated with the risk of new
drinking water treatment lessen the value of coliforms as a
pathogens and impacts on water quality and health.
predictor of the possible presence of diverse waterborne
Table 1 gives an example of some of these.
pathogens.
TABLE 1
Examples of Some Factors Influencing Water Quality and Health Risks
Factor
Outcome
Exposure issue
Health Issue
Population and
Increase in people
More wastes discharges.
Greatest  access is to urban beaches.
Land-use Change
and animals, more runoff.
More urbanization.
Sensitive populations at risk. (e.g. immuno-
CAFOs
compromised, elderly, and young).
Zoonotic pathogens.
Infrastructure
Aging wastewater and
More untreated wastes
High loads of pathogenic bacteria,
drinking water systems.
entering waterways.
parasites and viruses
combined sewer overflows,
storm sewer overflows.
Transportation
Agents spread globally
Ballast waters bring in
Known ecosystem risks and cholera
contaminants
suspected in South America.  Fecal coliforms
found in ballast waters.
Climate
Increased storms and
Impacts movement and
Increased waterborne disease risks associ-
droughts
survival of pathogens
ated with rain, storms, and temperature.
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