Air date: December 4, 2011

Host: Eric Metcalf

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I’ve spent a fair amount of my life trying to destroy the bacteria and viruses in my environment. I can’t see them, but I can feel them. So I was delighted to recently find a battery-powered germ-killing gadget in the pharmacy. It’s an ultraviolet light the size of a cell phone. The idea is that you can flip it open and wave it over keyboards, phones, and shopping-cart handles to kill the germs on them.

Frankly, it looked too good to be true, especially when discounted from $14 to $3. I called Anne Maczulak, the author of The 5-Second Rule and Other Myths About Germs, to break the inevitable bad news.

So, I asked her: does UV light really kill germs?

"It does, absolutely. It’s been used for many years. It’s very effective in killing germs under certain circumstances. Water treatment plants that produce your drinking water use UV lights more and more, they’re trying to get away from chlorine and some of the chemicals and they are trying to go toward less-invasive things like UV light."

But the light on this little gadget looks pretty feeble. Is it actually doing anything?

"It probably can damage some of the bacteria; it affects viruses, fungal spores. It’s pretty wide-ranging, so it has some activity. Here’s the thing that’s a bit of a caveat. Usually you have to hold it in place for at least 2 minutes to really be assured that you’re killing germs in the very spot you’re focusing on. Unfortunately, just waving it over the surface of the keyboard or countertop may not be sufficient."

As I was waving this thing over my desk, I could almost hear the cries of entire civilizations of germs dying in mass extinction. Apparently, though, they were just taunting me.

You’ve spent years finding ways to kill germs. Do you ever feel, you know, guilty about it?

"Bacteria have been here long before we have, and they’ll be here long after we leave the planet, so I’m not too worried about them."

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I’m Eric Metcalf, keeping my eye out for a bleach-powered flamethrower.

Additional Resources:

• Find out how UV light kills germs at the Scientific American website.