A recent story from blog Mind the Science Gap got us thinking about the pitfalls of overusing antibacterial soap. The active bacteria killer in those soaps, Triclosan, is just about everywhere these days--it shows up in everything from pizza cutters to toothpaste. It's possible that Triclosan isn't entirely healthy for us; worse, overuse may potentially be making some bacteria immune to Triclosan, and that's a whole new mess. But overuse of Triclosan doesn't mean we should stop caring about hygiene and let any old bacteria get us sick--we simply need to remember that there are other solutions out there that can kill bacteria. Like brass doorknobs, for example.

Fact: Frequently touched surfaces (especially in public places) are like safe havens for bacteria. Or breeding pools. Or discos, depending on how you like to visualize germs massing for an attack on your immune system. When our hands are unclean, we touch these services, depositing whatever germs we're carrying around with us. A lesser-known fact is that certain metals, such as brass, actually sterilize themselves after a certain period of time, making them ideal materials for surfaces like doorknobs.



It's called the oligodynamic effect. Wikipedia defines the effect as "a toxic effect of metal ions on living cells, algae, molds, spores, fungi,viruses, prokaryotic and eukaryotic microorganisms, even in relatively low concentrations." A study from the National College of Kathmandu in Nepal elaborates:

"The exact mechanism of this action is still unknown but some data suggest that the metal ions denature protein of the target cells by binding to reactive groups resulting in their precipitation and inactivation. The high affinity of cellular proteins for the metallic ions results in the death of the cells due to cumulative effects of the ion within the cells (Benson 2002). Similarly, silver inactivates enzymes by binding with sulfhydryl groups to form silver sulfides or sulfhydryl-binding propensity of silver ion disrupts cell membranes, disables proteins and inhibits enzyme activities (Thurman & Gerba 1988; Semikina & Skulacher 1990). The study also suggest that positively charged copper ion distorts the cell wall by bonding to negatively charged groups and allowing the silver ion into the cell (Hambidge 2001). Silver ions bind to DNA, RNA, enzymes and cellular proteins causing cell damage and death."