But increasingly, people are asking, “At what cost to our health and environment?”
Not All Silvers Are Created Equal
Centuries ago, the ancient Egyptians and Persians stored their water in silver containers to keep it clean and fresh. The Romans and Greeks knew it had powerful antibacterial properties and used it for healing wounds. American pioneers would toss silver coins into their water casks for purification, and during World War I, silver compounds were used to prevent the spread of infection.
Smaller concentrations of silver have been used in medicine over the years, as well. Colloidal silver – in which microscopic particles are suspended in distilled water or other liquid – may be the most familiar, having been popular in some circles of natural medicine.
As small as those particles are, though, they are a million times bigger than nanoparticles. To put that in perspective, think of the difference in size between a shirt button and the great state of Texas. That button is the nanoparticle.
Such particles behave very differently from their “macro” counterparts. In a traditional chemical reaction, elements bind mostly with surface molecules, while the interior remains stable. Nanoparticles are all surface, highly reactive and eager to bind. In its macro state, aluminum, for instance, is fairly stable; nano-aluminum, on the other hand, will explode when exposed to air.
What We Don’t Know About Nanosilver > What We Do Know
For all the time we’ve known about the beneficial uses of silver, we’ve also known that it can be toxic to humans and the environment alike – even in its macro form. Unfortunately, no one yet knows too much about the effects of nanosilver, though based on what we do know, there’s ample room for concern. Their incredibly small size – comparable to that of a virus – allows them to pass through cell walls, the blood brain barrier and the placental wall, possibly impeding cell function and ultimately contributing to disease.
Exposure to silver nanoparticles has been associated with “inflammatory, oxidative, genotoxic, and cytotoxic consequences”; the silver particulates primarily accumulate in the liver,[6] but have also been shown to be toxic in other organs including the brain.[7] Nano-silver applied to tissue-cultured human cells leads to the formation of free radicals, raising concerns of potential health risks.[8]
Such concerns have led to both independent and EPA studies, which have shown that pure nansoilver causes chromosomal and growth defects in fish embryos and insect larvae. Another concern is that with the onslaught of these nanoparticles in our lives, they may build up in the body over time, aggregate and become as toxic as their macro counterparts.
As an antimicrobial, nanosilver is none too particular about which kind of bacteria it destroys. It affects both beneficial and harmful bacteria. Again, to what effect, we don’t yet know. At the same time, there’s already evidence that some species are already adapting and thriving as “superbugs” in its presence.
If Ever There Were a Case for the Precautionary Principle…
Much more research needs to be done, but that presents some unique challenges, as well. For one, nanoparticles are so tiny that only incredibly powerful microscopes can find them.
Also, how they break down in the environment varies greatly depending on how much is released at once, what kind of environment they are in, and what they are bound to. Research from Duke University’s Center for the Environmental Implications of NanoTechnology (CEINT) found that in an aquatic system, a large dump of nanosilver quickly stabilized and aggregated, making the system toxic. In a slow, steady release into soil, on the other hand, nanosilver initially broke down only to accumulate over time.
Of course, this also makes one fact glaringly obvious: Nanosilver does not just go away.
“My suspicion, based on the limited amount of work that’s been done, is that nanoparticles are way less toxic than DDT,” says Richard Di Giulio, an environmental toxicologist researching nanoparticle science for CEINT. “But what’s scary about nanoparticles is that we’re producing products with new nanomaterials far ahead of our ability to assess them.”
The precautionary principle says that if there is cause for concern but no scientific consensus as to whether an action will be harmful or not, we should hold off until those who want to do the action prove it will not, in fact, cause harm. The responsibility is theirs.
Based on what we’ve seen thus far, we think it would be wise to start practicing this with nanosilver.
Image via Environmental Health Perspectives
(“Nanosilver: Weighing the Risks and Benefits”)