BIOLOGICAL POLLUTION - Marine Pollution: What Everyone Needs to Know - page 185

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BIOLOGICAL POLLUTION
Where does microbial pollution come from?
Microbial pollution comes from sewage that has not been
properly treated. Fecal contamination is a concern because
some of the microbes it contains can cause illness. High levels
of pathogens may be present in effluent from sewage plants
that do not have secondary treatment. Older cities that have
combined sewer systems combining storm sewers and house-
hold and industrial waste can discharge untreated sewage
during heavy rains when the volume of water exceeds the
capacity of the system. There is no national record-keeping of
how many illnesses are caused by sewage releases, but it is
estimated that as many as 20 million people each year become
ill from drinking water containing pathogens from untreated
waste that entered the water upstream from drinking water
sources. Nonpoint runoff is another source of microbes into
coastal waters—from animal feces, livestock operations, or
dense concentrations of wild animals. Hepatitis A virus, and
pathogenic bacteria (e.g., Salmonella, Listeria monocytogenes,
Vibrio cholerae , and Vibrio parahaemolyticus ) have been reported
in coastal waters.
Microbiological contamination can build up in marine life
(shellfish) when sewage is released to coastal waters or arrives
in river flow. Bacteria and viruses from humans and animals,
usually attached to fine particulate matter, can affect bath-
ing water quality, another potential source of illness. A study
estimated that as many as four million people become sick