These are some edited extracts of a report done at the request of UN and backed fully by the US including some heavy funding for a product that is not supposed to kill off germs, viruses, bacteria and pathogens which subsequently kill people. - OF COURSE COLLOIDAL SILVER WORKS REVIEW THES FACTS....
Submitted to Jubilee
House
November 18, 2001
USAID Purchase Order
Number:
524-0-00-01-00014-5362
_______________________
Extracts from
__________________________________
Investigation
Colloidal Silver Impregnated Ceramic Filter
Report 2: Field
Investigations
__________________________________
_______________________
Daniele S. Lantagne
Alethia Environmental
1 Project
Background
1.1 Hurricane Mitch, USAID, and CACEDRF
In October 1998, Hurricane Mitch devastated Central America, causing
over 3,000 deaths in Nicaragua alone (USAID 2001, 2001a). An estimated 18 percent of the population of
Nicaragua was affected by Mitch, and water and wastewater systems serving
804,000 people suffered over US$560 million in damage. The Unites States provided US$22 million in
immediate humanitarian and food aid, and an additional US$8 million to start
reconstruction activities in health, agriculture, and micro-finance.
In May 1999, the United States Congress authorized US$621 million in aid
under the Emergency Supplemental Appropriations Act (USAID, 2001). These funds were authorized to support
reconstruction in countries affected by Hurricanes George and Mitch, and were
later authorized to cover Hurricanes Floyd and Lenny, as well as the earthquake
of January 1999. This appropriation
created an account named the Central American and Caribbean Emergency Disaster
Recovery Funds (CACEDRF).
USAID is responsible for administering US$586.8 million of the US$621
million allocated under CACEDRF (USAID, 2001a).
Of the total funds, US$94.1 million was allocated for economic
reactivation, public health, school rehabilitation, disaster mitigation, and
municipal restoration in Nicaragua. As
of June 30, 2001, a significant amount of progress on projects relating to
water supply and sanitation had already occurred (Table 1-1).
Table 1‑1: CACEDRF Successes Relating to Water Supply
and Sanitation in Nicaragua
|
Category |
Success |
|
Economic Reactivation |
57,000
households incorporated environmentally sustainable practices on their farms 8,000
hectares of watershed area protected |
|
Public Health |
2,440
wells rehabilitated or built 5,740
latrines constructed 600
seepage pits constructed 175
deep wells drilled in rural areas 10,000
training visits held to improve health behavior related to new water and
sanitation infrastructure 6
health clinics constructed |
|
School Rehabilitation |
196
schools scheduled for rehabilitation of wells and latrines |
|
Disaster Mitigation |
Cleaning
and stabilizing stream channels Construction
of drainage channels |
|
Municipal Restoration |
Projects
with local governments on storm drain systems, flood control, river deck
construction |
An additional goal of the rehabilitation program in Nicaragua is to
investigate point-of-use household water filtration systems (USAID,
2001b). To this end, USAID worked to
install 40,000 sand filtration units, supervised by Maria Alejandra
Bosche. Ms. Bosche found that follow-up
education was critical to the correct and continued use of the filter system
(Bosche, personal conversation).
Secondly, USAID contracted with Jubilee House Community (JHC) to study
the Potters for Peace (PFP) ceramic water filtration system. JHC, an intentional Christian community, is a
501(c)3 organization in North Carolina (JHC-CDCA, 2001). From 1979 – 1994, members of the community
worked on shelters for homeless and battered women, as well as other social and
justice issues, in North Carolina. In
1994, the community moved to Nicaragua, established the Center for Development
in Central America (CDCA), and began working with communities in
Nicaragua. After Hurricane Mitch,
JHC-CDCA began to work on reconstruction projects in Nueva Vida, a nearby
community swelled with displaced persons.
USAID provided funding and supplies to build housing, a medical clinic,
and latrines (USAID, 2001c). JHC and a
group of volunteers worked with the community to build these facilities, in
addition to a number of other projects.
One of these other projects is the promotion of the Potters for Peace
water filtration system to provide safe drinking water for families in Nueva
Vida.
JHC worked with PFP to contract Daniele Lantagne, Principal of Alethia
Environmental and Lecturer in Civil and Environmental Engineering at the
Massachusetts Institute of Technology, to complete the project. The project was divided into two
deliverables, one addressing the intrinsic effectiveness of the filter, and the
other addressing the performance of the filters under field conditions. Specifically the reports are to address the
following:
Report
1: Intrinsic Effectiveness of the
Potters for Peace
Ceramic
Filter
· Best
practices for colloidal silver application.
· Expected
filter flow rates with and without colloidal silver.
· Expected
lifetime per application of colloidal silver.
· Concentration
of silver in filtered water.
· Effects
of ingestion of the silver.
· Inactivation
of microbes as a function of the concentration of silver.
· Effectiveness
of silver in removing other pollutants commonly found in the area of
interest.
Completion
Deadline: December 21, 2001
The PFP Filter
Initial Filter Design
In 1981 the InterAmerican Bank financed a comparative study designed to
determine which of 10 appropriate technology filters could be best adapted to
the objectives of the project, which were (ICAITI, 1994):
1. to produce a domestic filter of suitable
capacity;
2. in a self-supporting manner;
3. whose production would foster economic
activity at low income levels; and
4. foster artisan activity.
ICAITI, an industrial research institute in Guatemala supported by the Organization for American States, was contracted
to complete the research and to choose a model.
Ten models were evaluated based on filtration flow, bacteriological
efficiency, ease of manufacture, availability of materials, final cost,
contribution to artisan activity, and ease of distribution. All but two models were discarded after
initial review because they did not meet basic criteria. The two models not discarded were:
1. Lathed clay filter with feldspar, sawdust, and colloidal silver impregnation; and
2. Lathed clay filter with sand, sawdust, and colloidal silver impregnation.
None of the ten models investigated utilized chlorine as a disinfectant.
Further research was then conducted on the two models that met the basic
criteria. This research, led by Fernando
Mazareigos, did extensive bacteriological testing over a 3 to 10 month
period. Results of this research
include:
1. Of 302 filtered samples analyzed, only 6.3
percent were above 1.0 coliforms per 100 mL of water. The method used for analysis was most
probable number.
2. Application of silver was determined
to be more uniform when applied by brush as opposed to filtering water
containing colloidal silver through the filtering element.
3. Frequent contamination was found both in the
first few runs of the filter (41 percent contaminated) and after handling the
element during sampling. This was
attributed to handling the filter and ICAITI recommended that users refrain
from touching the element during its useful life. Due to the omnipresent bacteria in the
environment “usage of the filter must be accompanied by sanitary and hygienic
practices in order to maximize the potential benefits to health.”
4. Flow in the filters gradually declined from
3.5 liters per hour on Day 1 to 1.97 liters per hour on Day 365. The report contained no information on
turbidity of the raw water supply.
5. ICAITI recommended not using the filter with
chlorinated water. No reason was
given.
Based on these results, ICAITI concluded that a
colloidal silver impregnated ceramic filter was the only design that met all
established criteria of the study. The
United Nations then included this filter in their Appropriate Technology
Resource Material Manual. ICAITI
concluded its study by producing a “Manual Para La Fabricacion De Filtros
Artesanales De Agua Potable.”
Table 0‑1: Worldwide Public Health Impact of Waterborne
Disease (WHO, undated)
|
Disease |
Morbidity (per year) |
Mortality
(deaths / year) |
Population
at risk |
|
Waterborne &
water-washed |
|
|
|
|
Cholera |
|
|
|
|
Diarrheal disease |
1,500 million
episodes in children under 5 |
4 million in
children under 5 |
over 2,000
million |
|
Enteric fevers |
500,000 cases |
25,000 |
|
|
Poliomyelitis |
204,000 |
25,000 |
|
|
Ascariasis
(roundworm) |
1,000,000 |
20,000 |
|
|
Leptospirosis |
|
|
|
|
Trichuriasis |
|
|
|
|
|
|
|
|
|
Water-washed |
|
|
|
|
Trachoma |
6 – 9 million
blind |
|
500 million |
|
Leishmaniasis |
400,000 new
infections / year |
|
350 million |
|
Relapsing fever |
|
|
|
|
Typhus fever |
|
|
|
|
|
|
|
|
|
Water-based |
|
|
|
|
Schistosomiasis |
200 million |
200,000 |
500 – 600 million |
|
Dracunculiasis |
over 10 million |
|
over 100 million |
|
|
|
|
|
The microorganisms that cause these waterborne diseases are classified
as bacteria, protozoa, viruses, and helminths (Levinson, 1996). These four organisms belong to different
kingdoms and are eukaryotic (containing DNA with a nuclear membrane),
prokaryotic (without a defined membrane), and noncellular (Table 3-2).
Table 0‑2: Biologic Relationships of Pathogenic
Microorganisms (Levinson, 1996)
|
Kingdom |
Pathogenic
Microorganism |
Type
of Cell |
|
Animal |
Helminths |
Eukaryotic |
|
Protist |
Protozoa Fungi |
Eukaryotic Eukaryotic |
|
Prokaryote |
Bacteria |
Prokaryotic |
|
|
Viruses |
Noncellular |
Bacteria are single-celled prokaryotic (without nucleus) members of the
eubacteria group (MEI, 1991). Although
they are not eukaryotes (with a defined nucleus), they have similar cell
chemistry to eukaryotes. Their size
varies from 0.3 to 100 μm in length, depending on their shape (Table 3-3). E. coli is a rod shaped bacteria that
is 0.5 μm in width and 2 μm in length.
Most of the bacteria are larger than the 1μm pore size that Potters for
Peace aims to maintain in their filter.
Table 0‑3: Bacteria Types and Size (adapted from MEI,
1991)
|
Shape |
Name |
Size |
|
Spherical |
cocci, coccus |
1 – 3 μm in diameter |
|
Rod |
bacilli, bacillus |
0.3 – 1.5 μm in width 1.0 – 10 μm in length |
|
Curved rod |
vibrios |
0.6 – 1.0 μm in width 2 – 6 μm in length |
|
Spiral |
spirilla |
up to 50 μm |
|
Filamentous |
|
up to 100 μm and longer |
Protozoa are single-celled eukaryotic (with a nucleus) organisms. They feed on bacteria and other microscopic
organisms. Giardia lamblia and cryptosporidium
are common disease-causing protozoa.
Protozoa range in size from 8 – 100 μm.
Viruses are parasitic particles consisting of a strand of genetic
material. They do not have the ability
to synthesize new compounds, and instead invade the host cell and redirect the
host genetic material to produce viral particles. Because they do not have the structure to
reproduce themselves, viruses are the smallest of the disease-causing
organisms, at 0.02 – 0.2 μm.
Helminths are worms that are part of the animal kingdom. Platyhelminthes (flatworms) and Aschelminthes
(flukes, tapeworms) are present in water bodies throughout the world, and enter
the human body to cause diseases such as trichinosis, hookworm, and roundworm
infestation.
Infectious agents commonly found in drinking water include members of
the bacteria, virus, protozoa, and helminth groups and cause diseases ranging
from diarrhea to jaundice to acute respiratory illnesses (Table 3-4).
Table 0‑4: Waterborne Disease-Causing Organisms (MEI,
1991)
|
Organism |
Disease |
Remarks |
|
Bacteria |
|
|
|
Escherichia coli |
Gastroenteritis |
Diarrhea |
|
Legionella pneumophila |
Legionellosis |
Acute respiratory illness |
|
Leptospira |
Leptospriosis |
Jaundice, fever |
|
Salmonella typhi |
Typhoid fever |
Fever, diarrhea |
|
Salmonella |
Salmonellosis |
Food poisoning |
|
Shigella |
Shigelloisis |
Bacillary dysentery |
|
Vibrio cholerae |
Cholera |
Heavy diarrhea, dehydration |
|
Yersinia enterolitica |
Yersinosis |
Diarrhea |
|
|
|
|
|
Viruses |
|
|
|
Adenovirus |
Respiratory disease |
|
|
Enteroviruses (67 types, including polio,
echo, etc.) |
Gastroenteritis, heart
anomalies, meningitis |
|
|
Hepatitis A |
Infectious hepatitis |
Jaundice, fever |
|
Norwalk agent |
Gastroenteritis |
Vomiting |
|
Reovirus |
Gastroenteritis |
|
|
Rotavirus |
Gastroenteritis |
|
|
|
|
|
|
Protozoa |
|
|
|
Balantidium coli |
Balantidiasis |
Diarrhea, dysentery |
|
Cryptosporidium |
Cryptosporidiosis |
Diarrhea |
|
Entamoeba histolytica |
Amebiasis |
Diarrhea, bleeding |
|
Giardia lamblia |
Giardiasis |
Diarrhea, nausea,
indigestion |
|
|
|
|
|
Helminths |
|
|
|
Ascaris lumbricoides |
Ascariasis |
Roundworm infestation |
|
Enterobius vericularis |
Enterobiasis |
Pinworm |
|
Fasciola hepatica |
Fascioliasis |
Sheep liver fluke |
|
Hymenolepis nana |
Hymenolepiasis |
Dwarf tapeworm |
|
Taenia saginata |
Taeniasis |
Beef tapeworm |
|
T. solium |
Taeniasis |
Pork tapeworm |
|
Trichuris trichiura |
Trichuriasis |
Whipworm |
Thus, a number of different organisms of varying size and pathology
contribute to waterborne disease throughout the world. Two mechanisms in the PFP filter contribute
to reduction of these organisms. The
first mechanism is filtration. The PFP
filter will trap any particle or organism that is larger than the pore size of
the filter. PFP aims to have a pore size
of 1 μm (1 micron). This would trap a
significant portion of bacteria, and all protozoa and helminths. However, viruses are smaller than 1 micron,
and thus would not be trapped.
To date, no studies have been completed analyzing the pore size of the
PFP filter. For Report 1 of this study
(December 2001), analysis of the pore size of the PFP filter and retention
rates of selected viruses and protozoa will be completed.
The second inactivation mechanism for organisms
contributing to waterborne disease utilized in the PFP filter is COLLOIDAL
SILVER.
Colloidal Silver as a Disinfectant
Silver is a soft, malleable metal, which is stable in water and oxygen
but attacked by sulfur compounds in air to form a black sulfide layer (CRC,
1997). The atomic number of silver is
47, its atomic weight is 107.868, and it exists in its common valence states of
Ag+, Ag2+, and the mineral form of argentite, Ag2S. Typical ambient concentrations of silver are
presented in Table 4-1. Silver is
present throughout the environment in small concentration (milligram to
nanogram), but is not essential for animal or plant life.
Table 0‑1: Typical Ambient Concentrations of Silver
(adapted from CRC, 1997)
|
Content |
Concentration |
|
Total Content in Soils |
0.03 – 0.9 mg/kg |
|
Soluble Content in Soils |
0.01 – 0.05 mg/kg in 1 N NH4AOC |
|
Content in Sea Water |
0.04 μg/kg |
|
Content in Fresh Water |
0.13 μg/kg |
|
Content in Marine Animals |
3 – 10 mg/kg |
|
Content in Humans |
Blood: < 2.7 μg/L Bone: 1.1 mg/kg Liver: <5 – 32 ng/g |
|
Content in Animals |
6 μg/kg |
|
Content in Plants |
0.01 – 0.5 mg/kg |
|
Content in Common Foods |
0.07 – 20 mg/kg |
|
Essentiality |
Plants: no Animals: no |
The daily dietary intake by humans is estimated at 0.0014 to 0.08 mg
(CRC, 1997). When the maximum CRC intake
per day (0.08 mg) is calculated over a 70-year lifetime, a total of 2.0 grams
of silver are ingested per person per lifetime.
0.08 mg / day 365 days / year 70 years = 2.0 grams / lifetime
Toxic intake for humans is 60 milligrams, while a lethal intake is 1.3
to 6.2 grams (CRC, 1997).
Silver Human
Health Standards and Regulations
World
Health Organization (WHO)
In their Guidelines for Drinking-Water Quality, 2nd Edition
(1993), the WHO addressed human health effects of silver and guidelines values
to prevent those effects.
WHO determined that:
1. The retention rate of silver in humans and
animals is only 0 – 10 percent. The
retained silver is mainly stored in the liver and skin. The half-life of silver in the liver is 50
days.
2. Silver is occasionally found naturally in
ground and surface water at 5 μg/L.
3. Average human intake of silver is 7.1 μg/day.
4. The acute lethal dose of silver nitrate
is a minimum of 10 grams.
5. Argyria is the only known human health effect
of silver, and “is a condition in which silver is deposed on skin and hair.”
Based on their research, the WHO recommended a guideline value for
silver of 10 grams per lifetime. This
is a NOAEL (no observed adverse exposure limit) standard. WHO concludes by stating “as the
contribution of drinking-water to this NOAEL will normally be negligible, the
establishment of a health-based guideline value is not deemed necessary.” In 1996, the WHO reiterated this
determination by designating silver as a “U” compound. “It is unnecessary to recommend a
health-based guideline value for these compounds [U compounds] because they are
not hazardous to human health at concentrations
normally found in drinking-water.”
However, the WHO addresses the fact that silver is often used as a
disinfectant, and in such cases, “the daily intake of silver from
drinking-water can constitute the major route of oral exposure.” Thus, WHO has established an additional
guideline value for when silver is “used to maintain the bacteriological
quality of drinking-water.” This
guideline states “higher levels of silver, up to 0.1 mg/L (this concentration
gives a total dose over 70 years of half the human NOAEL of 10 g) could be
tolerated in such cases without risk to health.”
Thus, the guideline value appropriate for use in analyzing the PFP
filter is 0.1 mg/L (or 100 μg/L) in the finished, filtered water.
United States
Environmental Protection Agency (USEPA)
The USEPA has also investigated silver to determine appropriate drinking
water standards. The USEPA recommends a
maximum intake of 5 μg/kg/day (1996). In
the average 70 kilogram adult, this is equivalent to 350 μg/day. This recommendation was established to
prevent argyria, “a medically benign but permanent bluish-gray discoloration of
the skin. Argyria results from the
deposition of silver in the dermis and also from silver-induced production of
melanin.” Argyria is “more pronounced
in areas exposed to sunlight due to photoactivated reduction of the metal”, and
“although the deposition of silver is permanent, it is not associated with any
adverse health effects.”
In addition, “no evidence of cancer in humans has been
reported despite frequent therapeutic use of the compound over the years.” Silver was used for centuries to treat
syphilis, and as an astringent in topical preparations.
The 2001 National Secondary Drinking Water Regulations recommends a
maximum silver concentration of 0.10 mg/L (or 100 μg/L), but specifically
states that “EPA recommends secondary standards to water systems but does not
require systems to comply. However,
states may choose to adopt them as enforceable standards.” These secondary non-enforceable guidelines
regulate “contaminants that may cause cosmetic effects or aesthetic effects in
drinking water.” The USEPA does not
address separate standards for use of silver as a disinfectant. It is of note that the USEPA secondary
standard is the same as the WHO guideline value for use of silver as a
disinfectant: 0.1 mg/L or 100 μg/L.
Colloidal
Silver and USFDA/USEPA Regulation
A colloidal solution is “a true solution that consists of colloidal
macromolecules and solvent and that is thermodynamically stable and readily
reconstituted after separation of the macromolecules from the solvent (Stenesh,
1996).” Furthermore, a colloid is “a
macromolecule or a particle in which at least one dimension has a length of 10-9
to 10–6 meters.” Thus,
colloidal silver is a stable solution of very small silver particles suspended
in distilled water or proteins.
Higher concentrations of colloidal silver (such as used by PFP) are
suspended in proteins because they would not be stable in water (Quinto, personal
conversation).
In 1999, the United States Food and Drug Administration (USFDA) issued a
ruling that “all over-the-counter (OTC) drug products containing colloidal
silver ingredients or silver salts for internal or external use are not
generally recognized as safe and effective and are misbranded. FDA is issuing this final rule because many
OTC drug products containing colloidal silver ingredients or silver salts
are being marketed for numerous serious disease conditions and FDA is not aware
of any substantial scientific evidence that supports the use of OTC colloidal
silver ingredients or silver salts for these disease conditions (Federal
Register, August 17, 1999).”
The burgeoning naturopathic market for colloidal silver in the United
States prompted this ruling. In a cease-and-desist
letter issued to Mr. Randy Winters, the USFDA quoted Mr. Winters’ web site as
stating, “colloidal silver has been proven to be useful against over 650
diseases, including cancer, without any known harmful side effects. It has been found to cause rapid regeneration
of damaged cells and tissues, subdue inflammation and promote faster healing
(FDA, 2000).” A simple web search for “colloidal
silver” leads to numerous sites advertising unsubstantiated healing properties,
and another set of sites selling home-based colloidal silver generation
machines.
On August 8, 2001, I spoke with Ms. Roma Egli, the colloidal silver
contact person at the USFDA, about the PFP filter and the use of colloidal
silver for disinfection. Ms. Egli said that
the USFDA does not deal with disinfection agents, and that the USEPA would
regulate the use of colloidal silver in this manner. As long as PFP does
not state that the filters are treating animals or humans for disease, and does
not state that the colloidal silver is an antibiotic, the product is not
regulated under the USFDA. She
also mentioned that colloidal silver is used for water disinfection on
transportation systems such as airplanes, trains, and boats. When asked, Ms. Egli did state that she has
seen argyria cases in people only using naturopathic colloidal silver. No case she has seen is as severe as Rosemary
Jacobs’, but she has seen permanently blue fingertips. Overall, Ms. Egli expressed the viewpoint
that the USFDA is concerned about labeling of colloidal silver as a medical
drug when there is no research to support such claims. They are not concerned with colloidal
silver as a disinfectant, and in fact Ms. Egli recommended that I talk with the
Silver Institute (a promoter of colloidal silver as an antibiotic) about
purchasing a generator to make colloidal silver in Nicaragua rather than
importing it from Mexico. Because the
generators are only capable of producing colloidal
silver in the ppm range, as opposed to the 3.2 percent solution
that PFP uses, this idea was determined to be not appropriate for PFP
.
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
I then spoke with Wade Travathan, of the USEPA, about colloidal silver
as a disinfectant. The EPA Office of
the Pesticide Program regulates disinfectants because microorganisms in
the United States are legally classified as pests. Thus, any product
that kills microorganisms is classified under federal law as a pesticide. Mr. Travathan said that there are current,
active products that are registered with EPA that use colloidal silver as a
disinfectant. To become registered
as a pesticide, you submit data that details toxicity and efficacy. You can refer to data that has already been
submitted by another company, by offering that company appropriate
compensation. The submission forms are
available on the web site and submission is free of charge. However, there is a
maintenance fee of US$1,000 dollars per year on your permit. The Office of the Pesticide Program can be
reached at www.epa.gov/pesticides.
Thus, with the appropriate permitting from the USEPA
Office of the Pesticide Program, and data supporting that the finished water
concentration of silver is less than the USEPA secondary standard of 100 μg/L,
a colloidal silver impregnated filter is a legal product to distribute and use
in the United States and meets all USA regulations.
Silver in
Ceramics
Potters for Peace is not the only organization to use silver as a
disinfectant in ceramic filtration units.
Basu (1982) in India soaked ceramic candle filters with a pore size of 6
– 31 microns, and a filtration rate of 3 – 4 liters per hour, in silver
salts. Filtered
water with this system was bacteria-free. Basu chose silver
over gold as the bacteriocide, and also tested candle filters with
finer pores that would capture the bacteria.
The filtration rate was so slow with these finer pores, however, that
the filters were “not of much practical value.”
Thus a larger pore size, combined with a disinfectant, is of more
practical value because the flow rate is high enough to provide enough water
for a family.
Mechanisms of
Action of Silver
Russell (1994) details the historic uses of silver, beginning with Aristotle advising Alexander the Great to boil
water and store it in silver or copper vessels to prevent waterborne disease on
his campaigns. In 1869, Ravelin reported that silver exerted its antimicrobial effect at very low
concentrations, an effect with was later termed “oligodynamic” or “active with
few” (Russell, 1994). In
1881, Crede advocated silver to prevent eye
infections in newborns, and silver drops were used to prevent gonorrhea of the
eye in newborns until very recently.
In 1920, the microbiological action of silver
was determined to be due to the Ag+ ions formed by
tarnishing, surface-oxidation, or electrical activation.
Today, silver is more commonly used as a drinking water and swimming
pool disinfectant in Europe than in the United States (Russell, 1994). Studies have shown that silver can be used
when chlorine is present for additional disinfection. Argyria, first reported in 1647, is less
common today but is still reported.
Three main mechanisms are responsible for bacterial inactivation with
silver (Russell, 1994):
1. Silver reacts with thiol (sulphydryl, SH)
groups in the bacterial cell
a. In structural groups
b. In functional (enzymic) proteins
2. Silver produces structural changes in
bacterial cell membranes
3. Silver interacts with nucleic acids
These three mechanisms are described in further detail in the following
sections. Although it is unknown at this
time which of these mechanisms is predominant in the PFP filter, laboratory data clearly shows that PFP filters impregnated
with colloidal silver remove 99 – 100 percent of bacteria
(CIRA-UNAN, various dates). Further
information on the mechanism of action of colloidal silver in the filter and
data on laboratory tests on the filter are presented in Report 2 (December
2001).
Heinig’s research on silver deposited on an inert surface is of special
note in relation to the PFP filter.
Heinig (1993) showed silver on a large inert surface area exhibited a
strong catalytic reaction with oxygen, which resulted in strong bactericidal
activity. The factors controlling the
rate of the catalytic reaction were: the
size and dispersion of the silver on the surface area of the bed, and the
volume of oxygen in solution. Heinig
found that bacteria and viruses were killed on contact without the need for the
release of metals into the water.
Silver as an
Enzyme Inhibitor
“Living cells are characterized by a complex and beautifully organized
pattern of chemical reactions mediated and directed by enzyme systems (Webb,
1963).” Webb continues by describing
the theory of inhibiting enzymes as a means to understanding the “energetics of
the cell.”
Directly distorting the pathways of
enzymically directed reactions by the introduction of a chemical substance is
one approach amongst others to alter metabolic activity. Other ways to alter metabolic activity
including changing the temperature or the pH, by irradiation of high pressure,
are nonspecific and seldom does one have any idea as to exactly what is
occurring in the complex protoplasmic matrix.
If one had to choose the most interesting and important characteristic
of enzyme inhibitors, what it is that makes them one of the most powerful tools
in so many fields of biological investigation, it would be their relative
specificity. The more we know about the
exact nature of the perturbation produced and the more selective this action
can be made, the more likely it is that clear interrelationships will emerge
and the goal of understanding the energetics of the cell be achieved.
A number of metals are known to inactivate the SH (sulfur-hydrogen, or
sulfhydryl, or thiol) bond in enzymes. Silver
is widely used in biochemistry applications to determine if an enzyme has a SH
group as part of its functional structure.
Webb’s summary of data collected on the action of silver on the SH bond
shows extremely varied inactivation depending on specific enzyme and
concentration (Table 4-2). These different reactivities could be attributed to an
electric field surrounding the SH group, steric factors
depending on where the SH group is in the protein structure, occurrence of
disulfide linkages, complexes of the SH group with surrounding groups, and
whether there is a single or double SH group.
Other SH inhibitors studied include mercury, arsenite, cadmium, iodine,
ferricyanide, and permanganate.
Although there exists a large variation, SILVER clearly inactivates
certain enzymes in sources that are responsible for waterborne disease (Table 4-2). Waterborne disease sources are boldfaced in
Table 4-2.
End of extracts
