Will wonders never cease?: A hypochondriac surfer...Courtesy RickydavidIronic, isn’t it? Silver kills werewolves, werewolves hate silver…and yet these ancient enemies are more alike than they ever knew.

As we all know, materials start to get a little crazy when they approach the nano scale. Try as I might to crush bacteria to death with my silverware (beats washing it), silver on the flatware scale is not a very effective antimicrobial material.

When you get down to the nano scale, however, where silver particles are just a few billionths of a meter, it’s no longer like chasing down flagellates with a spoon. Really, nothing is quite like chasing down flagellates with a spoon, but all comparison is lost in the case of nano-silver.

It has been known for years now that nanoparticles of silver are able destroy harmful bacteria. The nanoparticles generate unique chemicals, known as “highly reactive oxygen species,” which inhibit the growth of bacteria. This is great, because we all hate those harmful bacteria. Nano-silver, for instance, is already found in certain fabrics to destroy odor-causing bacteria, and some high-tech washing machines generate tiny particles of silver for essentially the same reason.

Unfortunately, it’s becoming clear that these glittery little assassins may be the enemy of all bacteria, harmful and helpful.

It’s like this: we’d all love werewolves if they just spent their days tearing apart mummies, because mummies are gross and dangerous. But when werewolves start ripping into other more beneficial monsters, like Frankensteins, well, then they tend to lose favor. Frankensteins may be gross, but they have good hearts.

These tiny silver particles, according to researchers at the University of Missouri, have been ripping into Frankensteins. It’s been observed that nano-silver kills off beneficial, benign bacteria, like that used for wastewater treatment. As consumer use of nano-incorporating products increases, so to will the amount of artificial nano particles in the waste stream. Eventually this could kill off vital microbial species in rivers, streams, and lakes, as well as those used in wastewater treatment. There may be indirect consequences as well—for instance, the “sludge” byproduct of wastewater treatment is frequently used as land-application fertilizer. If silver nanoparticles accumulate in high enough levels in this sludge, they could end up seriously damaging the soil we use to grow our food crops.

This isn’t to say that we should necessarily halt our use of nano products, but it’s a reminder of how little we still know about nanotechnology. While we’ve had hundreds of years to learn to learn the ins and outs of deal with werewolves, nanotechnology is still pretty mysterious.

The University of Missouri will soon be launching a second study to determine the levels at which silver nanoparticles become toxic, and to exactly what extent they harm microbes in wastewater.