UV Sanitizing Light Wand

By Jeff Jumper - bio | email

LAKE CHARLES, LA (KPLC) – Using ultraviolet rays to sanitize your counters could replace all those chemical cleaners you use now.  The UV Sanitizing Light Wand is takes four double-A batteries which power a special light bulb to zap away harmful bacteria.  The bulb emanates a powerful wavelength of UV light to destroy bacteria.  We've set out to see if this light works.

I head to McNeese State University in Lake Charles to speak with Dr. Jay Comeaux, Assistant Professor of Biology & Health Sciences.  He contacted us about the wand after he purchased two at a local store.

Dr. Comeaux explains, "The goal of these wands is to disinfect surfaces using ultraviolet light.  If you shine ultraviolet light on microorganisms, it damages their DNA, and hopefully kills them."

So here's a little lesson on ultraviolet or UV light.  On the light spectrum, UV light has a shorter wavelength than light we see with our eyes, but a longer wavelength than X-Rays.  This shorter wavelength allows the ultraviolet light to pack more energy.  We've heard of UV-A & UV-B rays which come from the sun.  These rays are responsible for damaging skin cells in the form of sun burn and skin cancer.  The sun emits UV-C rays as well.  The UV-C rays from the sun rarely make it to our skin because ozone in the upper atmosphere absorbs all of these rays.  This wand utilizes a low dose of these higher energy UV-C rays.

Without direct or prolonged exposure to skin, the wand is very safe.  Plus, it has a built in switch to shut off the light when it's turned upside down.  Inherently, the wand has limitations.

"The UV Light won't penetrate deeply into substances, so it's only for superficial sanitizing," explains Dr. Comeaux.

The instructions claim it kills several types of household bacteria they label as target pests.  Dr. Comeaux prepared the following target pests: E-Coli, Salmonella, and Staphylococcus Aureus.  He generously coats several plates with these strains of bacteria.

We decide to test the effectiveness of the wand by varying the time of light exposure and the distance of the wand.  We covered half of the sample on each plate with cardboard to compare the treated with the untreated sides.  For each bacterium, we held the light at a half inch from the surface as instructed.  The recommended time is ten to twenty seconds, so we exposed the samples to UV light for one, five, ten, and twenty seconds.

Using strictly E-Coli samples, we held the time at twenty seconds changing the distance from a half inch to one, two, and four inches.  We placed the samples into the incubator to sit for two days.

"We'll be able to tell the difference in the amount of growth remaining on the plate," states Dr. Comeaux.

We returned after two days pass and check out our plates.  Immediately, we noticed a difference with some of the plates.

The plates held under the light for less than the minimum recommended time of 10 seconds showed full growth and no sanitizing on any of the plates.  All three of our samples grew with billions of bacteria across the entire plate with the one second and five second exposure times.

The plates exposed to the UV-C light for at least ten seconds at ½" displayed a remarkable difference.   The cultures show a nearly clean wipe of bacteria where the light exposed the plates in a thin strip about an inch wide.  The plates show discoloration where the bacteria colonized across the untreated part of the plate.  Where the light exposed the plate, there was a clear sanitized strip where all but a few small colonies of bacteria grew.  We found similar results with the plates exposed for 20 seconds at ½".

As far as our extra E-coli samples, we exposed the cultures with light for as constant twenty-seconds at distances of ½", 1", 2" and 4".  The ½" shows the same results as above.  At an inch however, the light sanitized a much larger area just as effectively.  The functionality dropped off completely at two inches and four inches though.

"As we got further and further away, the effectiveness dropped off dramatically," explains Dr. Comeaux.

So we determine the effectiveness depends on following the instructions closely.  Our best results come from a slight variation to the distance.

Dr. Comeaux says, "Ten seconds seems to be good, and it seems that an inch is more effective than a half inch."

We'd like you to keep in mind; our tests were done in near ideal circumstances with only three common bacteria on flat surfaces.  Not all applications will involve flat, impermeable surfaces.  Items such as cell phones or fabrics or spherical objects will not sanitize evenly.  Anywhere you can get a shadow from the light; you can run into loss of effectiveness.

Best put by Dr. Comeaux: "Our results may not be typical of what people would observe in other applications.

But our trials, under ideal conditions with three bacteria allow us to say that in most circumstances, the UV-C light technology of the UV Sanitizing Light Wand earns a YES for this week's "Does it Work?" test.  The UV Sanitizing Light Wand was on sale locally for about $10 when Dr. Comeaux purchased his.

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