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How Can I Sanitize My Smartphone and My House?

Sanitation is on everyone's minds right now. What's the best way to clean your (probably gross) phone, your home, and your own hands? Do you need antibacterial soap?

By
Sabrina Stierwalt, PhD
6-minute read
Episode #367
The Quick And Dirty
  • UV sterlizers are very effective at killing germs, including viruses and bacteria, on household surfaces and especially smartphones.
  • You should only use vodka (and other alcohols) as a sterlizer if it is more than 120 proof.
  • Antibacterial soap is no better at fighting off viruses than regular soap, which works by breaking germs apart.
  • Avoid hoarding supplies. All the hand sanitizer in the world will not protect you if your neighbor does not have access to the same supplies.

We all know our smartphones are disgusting. We take them everywhere—including the bathroom—which means we lay them down everywhere. We breathe on them. We touch them with dirty hands. But you can’t exactly soap up your smartphone as you sing happy birthday for twenty seconds, so how do you get your potentially-pathogen-carrying phone clean?

In a study published in 2018, researchers tested six different ways of sanitizing your smart phone against bacterial pathogens: two different UV-C devices (that's devices that use ultraviolet or UV light), alcohol spray containing 70% ethanol, ammonium disinfectant spray, wipes containing sodium hypochlorite (like Clorox bleach wipes), and delicate-task wipes marketed for cleaning electronics. They found all six methods reduced the number of bacteria detected on the smartphones. 

UV-C sanitizers were the most effective, removing more than 90% of the bacteria. Evidence shows the light effectively kills viruses as well.

But some methods were more effective than others. Both UV-C sanitizers were the most effective, removing more than 90% of the bacteria. The alcohol spray, bleach wipes, and ammonium spray were next, eliminating between 80-90% of the bacteria. Least effective were the delicate task wipes at less than 65% gone. Note this particular study was focused on bacteria, but the evidence shows the light effectively kills viruses as well.

The types of UV sterilizers used in this study are easily purchased online and for reasonably affordable prices. You can also purchase UV sterilizing wands that can be used to cover surfaces of any shape. I got one last year as a joke for a friend who is the tidiest person I know, and now, as hand sanitizer flies off the shelves, that wand may be the best thing I’ve ever gotten him.

Look for devices that provide doses of UV-C light at 60 mJ/cm2 (that’s a measure of energy per unit area) or more. Read the instructions for the appropriate exposure time and distance you should place between the wand and the object you wish to sterilize. 

How does UV light work to sanitize my stuff?

So, how does UV light sterilization work? A certain kind of ultraviolet light—that’s light at shorter wavelengths or higher frequencies than our eyes can see—known as UV-C light actually changes the structure of the DNA of a virus’s cells so that it can’t reproduce. If it can’t reproduce, it can’t start a new colony and spread. 

UV-C light has been tested as a sterilizer in hospitals and proven to be extremely effective. In one study, researchers tested 229 surfaces in hospital rooms used by 39 different, highly contagious patients. After the patients were discharged, but before hospital personnel came into the room to clean it, they tested surfaces before and after applying a dose of UV-C light. They were specifically after three superbugs and found the UV-C light removed 98% of the antibiotic-resistant VRE or vancomycin-resistant enterococci and 98% of the Acinetobacter. The light also removed 93% of Clostridium difficile, also known as C. diff. (Avid listeners may remember that C. diff. infections can be treated with a fun fecal transplant.) Overall, using the UV-C light eliminated 91% of the colonies of all of the pathogens they detected in the rooms. 

UV-C light actually changes the structure of the DNA of a virus’s cells so that it can’t reproduce. If it can’t reproduce, it can’t start a new colony and spread.

So why aren’t we bathing in UV-C all the time? Well, unfortunately for us, UV-C light also causes skin cancer and cataracts and is generally very dangerous for human tissue. When we talk about sunscreen, we usually talk about protecting our skin from the wrinkle-inducing UV-A rays and the sunburn-causing UV-B rays. Although the sun produces plenty of UV-C light too, that UV-C light is almost completely absorbed by our atmosphere. We don’t have to worry too much about getting cooked by UV-C rays from the sun when we step outside. But we also can’t, say, leave our smartphone outside on a sunny bench and hope it will be germ-free after an hour. UV-A and UV-B light are better at penetrating the Earth’s atmosphere, but they are also lower frequency (and thus lower energy) than UV-C light. That means they don’t have the same germicidal abilities.

The UV sterilizing systems used in hospitals use broad-spectrum UV-C light (meaning light emitted over a range of frequencies or wavelengths that are all classified as UV-C, or roughly in the range of 200 to 280 nanometers). Such spectra would most certainly wreak havoc on our bodily tissues, which means they're not safe for us humans. But recent research suggests that using UV-C light with a narrow range of wavelengths still has the same germ-fighting power but without as many of the harmful side effects. Essentially the light rays are too limited to penetrate through human skin but still easily attack the much smaller bacteria and viruses.

You can't leave our smartphone outside on a sunny bench and hope it will be germ-free after an hour.

A study from 2018 showed that continuous low doses of UV-C light emitted near 222 nanometers effectively killed airborne flu viruses without harming human tissues. Researchers released H1N1 droplets into a chamber and then exposed those droplets to UV-C light in the narrow range of 207 to 222 nanometers. 95% of the viruses were rendered inactive by the narrow range light, just as they would have been if exposed to a broad spectrum UV-C light. An earlier study by the same group had shown the 222-nanometer light also killed the methicillin-resistant bacteria MRSA without damaging the skin. What would flu season look like if we could put one of these emitters in every school, airport, airplane, and hospital? 

Can I use vodka?

As hand sanitizer gets harder and harder to find, people are turning to make-your-own recipes, many of which call for vodka. But when it comes to disinfecting with vodka, or any alcohol for that matter, concentration is key. According to the CDC, our cleaning solution has to be at least 60% alcohol (in other words, ethanol) to be an effective sanitizer. Hand sanitizers with lower levels of alcohol may not kill as many types of germs or may not kill them at all but instead simply slow down their growth. 

According to the CDC, our cleaning solution has to be at least 60% alcohol (in other words, ethanol) to be an effective sanitizer.

Tito’s Handmade Vodka put out a warning on Twitter asking consumers not to use its brand for any DIY sanitizers because their products are only 40% alcohol. Keep in mind that an alcohol’s proof gives twice its ethanol content by volume. So a vodka that is 80 proof is 40% alcohol. Other vodka brands like Everclear are 120 proof or 60% alcohol, but that’s still the bare minimum level when it comes to germ-fighting. 

Is antibacterial soap better than regular soap?

When it comes to washing your hands, antibacterial soap doesn’t do any more than regular soap to kill viruses. It's right there in the name—the antibacterial nature of antibacterial soap is meant to fight bacteria but is not necessarily any better at fighting viruses like SARS, COV-2, or the virus behind the disease COVID-19. Soap works to kill germs by breaking them apart chemically and through the mechanical disruption (that’s all the rubbing for 20 seconds). Hand sanitizer is a good option only when you don’t have access to soap and water. 

When you go to get supplies, don’t hoard. All the hand sanitizer in the world will not protect you if your neighbor does not have access to the same supplies.

One of the most important tips when it comes to sanitizing your things is, when you go to get supplies, don’t hoard. Stopping the spread of coronavirus and other viruses and bacteria means that everyone has to be protected. All the hand sanitizer in the world will not protect you if your neighbor does not have access to the same supplies. The time to look out for each other and protect each other is now.

About the Author

Sabrina Stierwalt, PhD

Dr Sabrina Stierwalt earned a Ph.D. in Astronomy & Astrophysics from Cornell University and is now a Professor of Physics at Occidental College.

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