While silver is known for its antibacterial properties, so are other heavy metals, but silver just happens to be one of the lightest and easiest to manage, to my understanding. The following sites are some that point to the general antibacterial capabilities of all heavy metals:
- Connective tissue responses to some heavy metals. I. Sodium loaded ion exchange beads as a control: histology and ultrastructure concludes, "This system provides a valid control for studies of the effects of metal cations on tissue inflammation and repair--free from anionic complications, surface phenomena or systemic interference."
- The study on "Heavy metal resistance in clinical isolates of Pseudomonas aeruginosa" states, "A correlation between silver ion resistance and concurrent mercury and cadmium ion resistance was observed, suggesting a possible linkage between resistance towards various metal ions."
- Correlation between multiple antibiotic resistance and heavy-metal tolerance among some E.coli strains isolated from polluted waters states, "The phenotypic data shows the direct association between multiple antibiotic and heavy-metal resistance for E. coli strains in polluted water."
- SUSCEPTIBILITY OF ARCOBACTER BUTZLERI TO HEAVY METALS states,
The susceptibility of 50 strains of Arcobacter butzleri isolated from chicken liver , mussels , river water  and bovine , duck  and pelicans  feces to mercury (Hg), chromium (Cr), silver (Ag), nickel (Ni), cobalt (Co), iron (Fe), manganese (Mn), molybdenum (Mo) and lead (Pb) was determined. All the strains were resistant to Mo, Mn, Ni, Co, Pb and Fe and susceptible to Hg, Ag and Cr. MIC values showed high variability, indicating a non homogeneous behavior among the strains."
The last item above is showing that some of the bacteria are becoming as resistant to heavy metal treatments as to other forms of medical intervention. This was a running theme once I started delving more deeply into what silver does, and doesn't do.
Another on this theme was the following: Immunotoxicology in wood mice along a heavy metal pollution gradient, which states that, "Heavy metal concentrations in liver tissue indicated that exposure to silver, arsenic, cadmium, cobalt and lead decreased with increasing distance from a non-ferrous smelter. Host resistance to the endoparasite Heligmosomoides polygyrus decreased with increasing exposure, while the abundance of tick larvae and the nematode Syphacia stroma was unrelated to heavy metal exposure. " and I began to look at the accumulation of heavy metals in the body, as that is where it all starts, as proponents claim that agryia has nothing to do with toxicity of silver.
A case of argyria after colloidal silver ingestion states, "Histological examination of skin biopsy specimen, which showed perieccrine brown-black granules, verified that colloidal silver rather than a prescribed medication was the source of the patient's dyspigmentation."
SUMMARY. We found that silver, either as silver metal or silver chloride, exerted toxic effects on the smooth muscle of isolated cannulated hamster cheek pouch arterioles. Silver initially stimulated the smooth muscle, producing a marked vasoconstriction. The vessels then dilated back to control diameters. Once the arterioles began to dilate, they became refractory to norepinephrine or potassium stimulation. We caution the use of silver in the presence of smooth muscle, especially when tissue mass is small or free protein concentration is low. (Che Res 53: 105-108, 1983)
Myoclonic status epilepticus following repeated oral ingestion of colloidal silver: "The authors report a case of a 71-year-old man who developed myoclonic status epilepticus and coma after daily ingestion of colloidal silver for 4 months resulting in high levels of silver in plasma, erythrocytes, and CSF. Despite plasmapheresis, he remained in a persistent vegetative state until his death 5.5 months later. Silver products can cause irreversible neurologic toxicity associated with poor outcome."
Having had experience trying to find good chemo drugs to counter the effects of lymphoma that has crossed the blood brain barrier, I can verify that this is no easy feat. Silver is a conductor of electricity, and so far, the studies I am running across, such as the last one above, are to do with organs that implement electrical impulses as they function in the body. Do you think there might be a problem here?
Our personal interest in animals has drawn us to information such as the following paper listing six studies:
EFFECTS OF THE INTRAVENOUS INJECTION OF COLLOIDAL
SILVER UPON THE HEMATOPOIETIC SYSTEM
IN DOGS written in Decmeber, 1930, made the following statement:
1. Colloidal silver has no specific action on the bone marrow in dogs but is a systemic poison which may cause anorexia, weakness, loss of weight, anemia, and death.
2. Hemolysis can be demonstrated after large doses of colloidal silver and the anemia presumably is due in part at least to a destruction of red blood cells in the peripheral circulation.
3. The colloidal silver, injected intravenously, is deposited as granules almost exclusively in the cells of the reticulo-endothelial system after the manner of particulate substances.
4. Repeated injections of non-lethal amounts of this substance are invariably followed by hyperplasia of the bone marrow. In no case was aplasia found.
5. Large single doses of this material cause rapid death in 12 hours or less characterized by pulmonary edema and congestion.
6. An initial increase in the number of erythrocytes and leucocytes may occur following smaller amounts of silver, but repeated injections cause a considerable anemia, without a definite increase in the leucocytes
and with no signs of blood platelet deficiency.
If the above link doesn't want to work, the information is included at the International Program on Chemical Safety, (WHO), site that also states the following:
" Silver toxicity is manifested in a variety of forms, some proven others suspected. Proven forms include: argyria, gastrointestinal irritation, renal and pulmonary lesions. Suspected forms include, among others (ill-defined) arteriosclerosis (Casarett and Doull, 1975)."
If you do want to take the risk of using colloidal silver, the EPA has recommendations, based upon scientific studies and papers such as the following statement:
"Hepatic necrosis and ultrastructural changes of the liver have been induced by silver administration to vitamin E and/or selenium deficient rats (Wagner et al., 1975; Diplock et al., 1967; Bunyan et al., 1968). Investigators have hypothesized that this toxicity is related to a silver-induced selenium deficiency that inhibits the synthesis of the seleno-enzyme glutathione peroxidase. In animals supplemented with selenium and/or vitamin E, exposures of silver as high as 140 mg/kg/day (100 mg Ag/L drinking water) were well- tolerated (Bunyan et al., 1968). "
Another article that is of great concern to me, as a consumer, is the one put out by the FDA/CVM in February of 1997:
"FDA has received reports that products containing colloidal silver are being promoted for
use in the treatment of mastitis and other serious disease conditions of dairy cattle, as well as for
various conditions of companion animals. For example, FDA’s Center for Veterinary Medicine
has received reports from the Agency's regional milk specialists and State inspectors that colloidal silver products have been found on some dairy farms. Also, recent articles in some farm
newspapers and journals promote the use of colloidal silver in treating mastitis and claim that no
milk discard is needed."
In the past I have run across the reference material that confirms the following statement made by Linda Aronson, DVM on page 15, "Product warning: Silver Colloidal Products" , in fact, you will possibly run across confirmation elswhere on this site, but her statement relates specifically to pets:
"Research has shown that silver accumulates throughout the body especially in the skin, liver, spleen and adrenals, but also in the brain and muscle tissue. If there are inflamed or damaged mucous membranes silver absorption increases. Silver accumulated in the subepithelium can cause a permanent, irreversible blue gray discoloration of the skin. Brain deposition has resulted in epileptic seizures and coma after daily ingestion for 4 months - despite most manufacturers claiming daily ingestion is safe and protects against pathogens. "
There are other sites with information such as the following, which I will add to as time permits:
Consumer Advisory: U.S. Department of Health and Human Services
The Physicians Desk Reference: "Current research makes it clear that there are no safe uses for over-the-counter silver products."
Effect of preinduction of metallothionein on tissue distribution of silver and hepatic lipid peroxidation: "Silver ion causes a number of toxic effects, it decreases the activities of lactate dehydrogenase and glutathione peroxidase, and the peroxidation of membrane lipids. Silver ions complex strongly to sulfhydryl groups and the effects of preinduction of metallothionein, a sulfur-rich protein, on silver administration in rats were examined. The preinduction of metallothionein decreased the mortality of mice following silver administration. A major portion of the incorporated silver in the liver was bound to the basal membrane and cellular components, and the distribution of silver into cytosol was small. The preinduction of metallothionein decreased the amount of bound silver in the membrane and increased the distribution of silver in the cytosol; in addition, it depressed silver-induced lipid peroxidation in liver."
Silver products for medical indications: risk-benefit assessment: CONCLUSIONS: We emphasize the lack of established effectiveness and potential toxicity of these products.
Analytical findings in a fatal poisoning with silver compound: The toxicological analysis of the postmortem material for silver performed by the flame AAS method (stomach, 2.43 micrograms/g; intestines, 1.12 micrograms/g; liver, 6.29 micrograms/g; kidney, 4.85 micrograms/g; spleen, 30.1 micrograms/g; heart, 10.8 micrograms/g; lung, 14.8 micrograms/g; and brain, 0.61 microgram/g) confirmed fatal silver compound poisoning.