Common Contaminants in Urban Watersheds - Urban Watersheds: Geology, Contamination, and Sustainable Development - page 263

• Irregular heartbeat
• Nonfatal heart attacks
• Premature death in people with heart of lung disease
An additional concern is the potential exposure to other contaminants sorbed onto
PM, which are then ingested or inhaled. This topic will be covered in greater detail in
Chapter 10.
7.8.13 Bacteria, Parasites, and Viruses
Although we do not always think of bacteria, parasites, and viruses as everyday environ-
mental contaminants, they are common in urban areas and can cause many diseases and
adverse health effects. They can contaminate water supplies and are also present in the air
we breathe, in soil, on and within food, and building surfaces. Therefore, because they are
so widespread and can produce adverse health effects, we will cover the basics.
Bacteria are organisms made up of just one cell. They are capable of multiplying them-
selves through a process called “binary fission,” whereby a single bacterium grows to
approximately twice its normal size and then splits into two daughter cells that are exact
copies of the original bacterium. Bacteria live everywhere, even inside most organisms.
Most bacteria are harmless and some are beneficial by destroying other harmful bacteria
within our bodies (Madigan et al. 2008). However, some may cause disease such as tuber-
culosis. One of the more common harmful bacteria is a group called E. coli , which is short
for Escherichia coli . Most E. coli are harmless but a strain called serotype O157:H7 can cause
food poisoning in humans. Three basic shapes of bacteria exist—rounded, rod shaped,
and spirals. E. coli bacteria are rod-shaped.
The ability for E. coli to survive for a brief period outside the body creates the potential
for the bacteria to spread and infect other people. The spread of E. coli usually occurs when
there is poor sanitation or when untreated sewerage is discharged from municipal waste-
water treatment plants, which occasionally occurs during flood events (USEPA 2009k).
Adverse health effects from exposure to E. coli bacteria typically include gastroenteritis,
urinary tract infections, skin rashes, and neonatal meningitis (USEPA 2009k).
A virus is a subcelluar infectious agent capable of replicating itself inside the cells of
another organism (Madigan et al. 2008). They are typically 100 times smaller than a bacte-
rium. Viruses consist of two parts: (1) DNA or RNA molecules carrying genetic informa-
tion and (2) a protein coat protecting the genes. Some viruses may also have an outside
layer of fat surrounding them while they are outside a cell. Viruses spread in many ways,
including aerosol routes (coughing and sneezing), through infected or contaminated water,
and exchange of body fluids. Viruses cause diseases such as the common cold, influenza,
chickenpox, mumps, ebola, and HIV.
A parasite is an organism living on or within a different organism (the host) at the
expense of the host organism. Common examples of parasites causing adverse health
effects in humans are Cryptosporidium and Giardia; both may cause severe intestinal
disorder (Center for Disease Control 2009). Exposure to these two parasites occurs by
consuming affected water (Center for Disease Control 2009). In humans, Giardia creates
uncomfortable, but curable gastrointestinal symptoms, whereas Cryptosporidium can cre-
ate life-long gastrointestinal symptoms in persons with weak immune systems and may
result in death.