Groundwater in the Great Lakes Basin

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PATHOGENS
Bacteria, viruses and protozoans are the main categories
of pathogens encountered in groundwater. Prions
represent an emerging concern. The U.S. Safe Drinking
Water Act amendments of 1996 required the U.S.
Environmental Protection Agency (EPA) to identify
every five years new chemicals and microorganisms
for potential regulation. The Contaminant Candidate
List (CCL), based on information about known and
suspected health risks and the occurrence of the
contaminant in water, addresses 13 microorganisms
including Aeromonas hydrophila, adenoviruses, Coxsackie
viruses, and Helicobacter and the blue green algae toxins
associated with Cyanobacteria (LeChevallier et al.,
1999; Balbus, Embrey and Parkin, 2002). The CCL
requires that information on health risks and occurrence
in water (potential exposure) be acquired and,
with that information, the development of rules for
these contaminants’ control may ensue.
Bacteria
The bacteria of greatest concern in groundwater
include Escherichia coli (including O157:H7),
Campylobacter and Helicobacter. These bacteria primarily
originate from sewage, animals and animal manure
(Table 1).
Enterohemorrhagic E. coli O157:H7 causes waterborne
diseases ranging from mild, watery or bloody diarrhea
to life-threatening conditions, such as hemolytic uremic
syndrome (HUS) and thrombotic thrombocytopenic
purpura (TTP) (Tserenpuntsag, Chang, Smith and
Morse, 2005). Two to seven percent of infected individuals
develop HUS and, of those, 33% are left with
chronic renal failure and 3% to 5% die. The population
most likely to develop TTP – the elderly – experience a
mortality rate as high as 50%. Health Canada estimates
that about 90,000 illnesses and 90 deaths are associated
with drinking water each year (American Society for
Microbiology, 1999). Evidence suggests that irrigation
wells near four spinach farms may have played a role
in the E. coli bacterial outbreak that tainted bagged
spinach and subsequently killed three people and
sickened at least 205 people in 2006 (Windsor Star,
2007).
Campylobacter jejuni causes a spectrum of diseases in
humans. Infection starts in the GI tract but can become
extraintestinal, particularly in immunocompromised
hosts (Blaser, 1997; Ketley, Guerry and Panigrahi, 1996).
In clinical reports describing primary infections with
C. jejuni in developed countries, infection with mucosal
disease predominates with symptoms of diarrhea,
abdominal pain and blood in the stool. Infection with
systemic spread, infection without disease with shortterm
bacterial persistence and infection with resistance
and no bacterial persistence occur infrequently. In some
cases the disease spectrum includes severe inflammatory
illness, mild secretory diarrhea or an asymptomatic
carrier state.
Helicobacter pylori (gram-negative, micro-aerophilic
bacterium) is a ubiquitous microorganism infecting
half the world’s population. As the primary cause of
peptic ulcers, chronic gastritis and associated with
MALT lymphoma and stomach cancer, the World
Health Organization classified it as a Class I carcinogen
(Blaser, 1996; Aruin, 1997). About 50% of the U.S. population
are thought to be symptomatic or asymptomatic
carriers, even though the source of human infection is
not well understood. Water supplies contaminated
with fecal material may be a potential source of H. pylori
transmission (Hulten, Enroth, Nystrom and Engstrand,
1998). The association between consumption of
untreated groundwater positive for H. pylori and infection
in the community has been demonstrated (Rolle-
Kampczyk et al., 2004).
Triclosan overuse is cited as one of the key factors in
widespread development of antimicrobial resistance
(Environmental News Service, 2005; Eckardt, personal
communication). It is used as an antibiotic in a broad
range of products from textiles and plastics to cleaning
and personal care products (Williams, 2006). Over 95%
of triclosan in consumer products eventually goes down
the drain. Widespread use has led to the appearance
of triclosan residues in umbilical cord blood of infants
and in the breast milk of nursing mothers (Williams,
2006). According to a British Environment Agency
(2006) report, triclosan is present in sewage effluent
and sewage sludge, and it also has been found at some
groundwater monitoring sites. The U.S. EPA considers
triclosan a high risk for human health and the environment
(Williams, 2006).
Historically, major epidemics of cholera and typhoid
fever were correlated to improper disposal of wastewater.
Dr. John Snow (1813-1858) was the first to make
a linkage between human waste contamination of the
city water supply and a devastating cholera epidemic
in London, England. When he famously removed the
pump handle from the community well, the cholera
epidemic halted. Snow published a brief pamphlet,
On the Mode of Communication of Cholera, suggesting that
cholera is a contagious disease. Snow postulated that
water contaminated with human body excreta was a
means of disease transmission (CDC, 2006).
The relationship between disease and water transmission
prompted major water monitoring initiatives.
In a seminal study in 1918, the International Joint
Commission carried out the most extensive bacte-