Geoscience Reference
In-Depth Information
Viruses usually, but not always, attach themselves to larger particles, which can be effectively
filtered out by standard microbial filters, so these types of filters offer significant protection
against viruses even though their pore size is far larger than the size of the virus.
Parasites
Parasites live off the bodies of host organisms for at least part of their life cycles. Parasites may
be microscopic, such as malaria or trichinosis. Single-celled animals like
Giardia
and
Crypto-
sporidium
can be considered parasites. Some parasites are several inches long, such as liver
flukes, or several feet long, such as intestinal tapeworms. Parasites remain the scourge of many
millions of people throughout the third world and infect a surprisingly large percentage of the
Western world. Research scientist Hulda Regehr Clark believes that twentieth-century solvents
tend to collect in some of the organs of our bodies and make them unusually good hosts for a
variety of parasites (Clark 1995, 332). According to Clark, these solvents, and the parasites
they nurture, contribute significantly to high rates of cancer. In the West, most parasites appear
to be picked up through contact with house pets or while preparing raw meat. In the third
world, parasites are often spread by eating raw meat or through poor sanitation and lack of wa-
ter treatment. Usually parasites do not kill their hosts, but sap health, body strength, and vital-
ity. (See any of Dr. Clark's topics or chapter 9 in
When Technology Fails
for low-tech solutions
to parasite infections.)
Parasites are killed by boiling, chlorine dioxide treatment, and UV sterilization, but may
survive iodine and traditional chlorine treatments if they are in cyst form. Their relatively large
size makes them easy to filter out of contaminated water. All known parasites are filtered out of
the water by filters rated at 2 microns or less.
Chemical and Radioactive Contaminants
Potentially harmful chemical contaminants in our drinking water include heavy metals, such as
arsenic and lead from industrial pollution or naturally occurring deposits in deep well water, or-
ganic compounds from various industries or chlorine treatment of surface water, and nitrates
and pesticides from modern farms. In some parts of the world, pollutants also include radioact-
ive contamination from the refining of radioactive materials or industrial accidents, such as the
partial meltdown of the reactor at Chernobyl.
Organic compounds are large molecules that consist of chains of carbon and hydrogen
atoms with various other atoms attached to them. The modern world has invented huge num-
bers of organic compounds and refined and concentrated many other naturally occurring organ-
