Which UV Wavelength is Most Dangerous – UVA, UVB or UVC?

Most of us have heard of ultraviolet (UV) light. Thanks to sunscreens ads and common knowledge, we also know that there are dangers associated with UV light exposure. But did you know there are different types of UV light?

UVA, UVB, and UVC light are all subsets of ultraviolet lighting that occur naturally. However, each have their own intensities and properties that make them better suited to different types of applications. Below, the experts with Action Services Group explain the differences between UVA, UVB, and UVC light, as well as the dangers associated with them and the best way to protect yourself.

Understanding the Differences

Light wavelengths are measured in nanometers (nm). Different wavelengths affect visibility and intensity. Visible light, for example, are those which range between 380nm and 780nm.

UV light, however, falls just short of this. In fact, when talking about UV light, you are only discussing light with wavelengths that measure between 100 nm to 400 nm. As mentioned above, this is broken into subcategories known as UVA, UVB, or UVC.


UVA wavelengths fall between 315 nm and 400 nm. These are the longest forms of UV wavelengths. UVA wavelengths are those that are most likely to cause skin aging and wrinkles. Why? Because UVA rays are some of the only ones that occur naturally, leaving humans exposed for longer periods of time.

UVA rays have been linked to cancer as they are able to penetrate the skin’s dermis layer quickly, which is why they are known to help tan the skin. Unlike UVB and UVC wavelengths, UVA rays are also able to penetrate through glass and clouds. This means your windshield and windows provide little protection from exposure. (Hence the reason experts in the medical field always urge you to apply sunscreen, even if you are not spending a day at the beach!)


UVB refers to light with wavelengths between 280 nm and 315 nm. While fewer of these rays penetrate the earth’s ozone layer, those that do are more intense than UVA light. Because of this, UVB light is often cited as the source that causes sunburn. In fact, UVB rays can burn the top layer of your skin, known as the epidermis layer, in as little as 15 minutes.

UVB wavelengths can vary based on the time of day, as well as the season. This is because they typically only break through the ozone layer while the earth is closest to the sun. Because they can damage the skin, UVB wavelengths have been known to age skin and lead to skin cancer.


UVC wavelengths are the shortest on the UV spectrum; they range from 100 nm to 280 nm. Because of this, they are also the most intense UV wavelengths. However, the earth’s ozone fully blocks these wavelengths from entering our atmosphere.

Although natural UVC wavelengths do not reach the earth’s surface, artificial sources still exist. Applications, while important, should still be used with caution with proper measures taken to prevent prolonged exposure.

You probably have more questions, some of which might not be answered in this blog. Have you reviewed our Ultraviolet Lighting FAQ page? It answers questions on safety, fixture types, what UVC disinfects, and much more! Still have more questions? Schedule a Call with one of our UV Lighting Specialists, by clicking the button below.

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Artificial UVC

For the most part, the earth’s atmosphere prevents wavelengths below 350 nm, which means that most of all UV light must be artificially created. (Of the UV light that does enter the earth’s atmosphere, 95% are UVA wavelengths and the remaining 5% are UVB.)

You may find yourself asking why artificially UVC lighting would be desired. After all, knowing the dangers associated with UVA and UVB lighting may make it seem foolish to artificially create an even more intense UVC light source. However, there are many different UVC applications that exist today and require the use of an artificial source. Many of these applications are quite common and you are likely familiar with them. This includes things like:

We have all heard the dangers related to tanning beds. From sunburns and irritated eyes to aged skin and even skin cancer, the dangers of a tanning beds are well known. (It should be noted that most modern tanning beds use UVA lights, however, older models are still in use and should be avoided.) Use of these beds is a choice and can be avoided.

However, welding torches and lasers may not be so easily avoided, especially when your job relies on these items. While there is still a risk of exposure, professionals wear protective equipment that can prevent damages resulting from exposure. (Welders masks, thick gloves and other such equipment can ensure skin and eyes are protected.)

Of all the applications listed above, however, you may find yourself least familiar with germicidal UVC lighting. Let’s take a closer look at the benefits associated with this application.

There are a lot of terms in this blog, and you might not be up to date on your UVC terminology. So, what is Ultraviolet Germicidal Irradiation or Germicidal UVC Lighting? You can find out the answer to those questions and more here!

The Benefits of Germicidal UVC

UV light is known to damage, if not kill microorganisms. How? UV wavelengths are able to damage the RNA and DNA of microorganisms in a way that prevents them from multiplying. This, in turn, leads to the elimination of these microorganisms as they are no longer able to reproduce and spread.

UVA wavelengths are the least effective when it comes to disinfection. UVB, which is slightly more intense, can help disinfect some minor illnesses and bacteria. Of all the UV wavelengths, however, UVC is considered the strongest and most effective. (In fact, even illnesses that are considered drug-resistant are known to die once exposed to UVC lighting.) While tests related to COVID-19 are still underway, all other types of illnesses that have been studied after UVC exposure have been unable to survive.

You may find yourself asking why opt for germicidal UVC light over chemical or household cleaners? Several different types of microorganisms are known to become resistant to chemical disinfectants. It is also impossible to apply the same level of cleanliness each time a surface is cleaned. Exposure to a germicidal UVC light source, however, is all-encompassing and consistent, ensuring the same level of disinfection after every use.

Germicidal UVC lighting has existed for decades. Although primarily only used in hospitals to help prevent the spread of illnesses and diseases, plenty of other institutions and applications have been developed. For example, airports, schools and universities, and fitness centers have all started to use UVC lighting to help sanitize and disinfect surface areas and equipment to slow the spread of illnesses. Used in air ducts, attached to walls and ceilings, and even installed in water sources, UVC fixtures can help stop the spread of microorganisms on a surface, in the air, and under water.

We have several blogs that breakdown the benefits of UVC Disinfection Lighting as it pertains to different industries. We highly suggest reviewing our entire UV Lighting Blog Series. You might also want to take a look at our Workplace Safety Series for additional avenues of layered protection against the Coronavirus.

Dangers of UV Light

We have talked about the range in UV wavelength intensities. All are capable of causing skin irritation, tans, and burns, as well as the potential for premature aging, cancer, and even eye damage. But which is truly the most dangerous?

There really is not one, concise answer to this question. UVA wavelengths, while being the least intense, are ones we are exposed to every day. This means they are most likely to cause long term damages since many of us fail to take preventative measures. (After all, do you apply sunscreen before going for a drive? These rays penetrate your windshield, exposing your eyes and skin to their dangers the entire time.) UVB rays, which also penetrate the earth’s atmosphere, are more intense. While they are more likely to cause sunburn, they take a certain level of exposure before this occurs. (However, intense sunburns can lead to extreme and permanent damages to your skin more quickly than years of UVA exposure.) Because of this, UVB exposure is more likely to lead to skin cancer than UVA or UVC light.

Protect Yourself

Broad-spectrum sunscreen, clothing, and sunglasses can help prevent damages caused by UVA and UVB light. Because UVA light can penetrate your glass and clouds, experts recommend sunscreen applications even when indoors or going out on cloudy days. Reapplication of sunscreen, which is also overlooked, is equally as important since the skin eventually absorbs the initially applied protective layer and leaves you exposed.

Because UVC applications are more targeted, precautions can be taken as needed. If you decide to use a tanning bed, make sure you utilize the recommended protective goggles as your eyelids provide little protection. Professional face masks, such as those worn by welders, are specifically made to prevent eyes and faces from being exposed to UVC wavelengths. When using germicidal UVC lighting, it is often recommended that applications occur when the room is unoccupied or when protective clothing and eyewear is used.

UVC Lighting with Action Services Group

While there are some dangers of UV light, protective measures can ensure safe applications. This is particularly true when it comes to germicidal UVC lighting, which has become even more important in these uncertain times.

If you are interested in learning more about how UVC disinfection lighting may help your business, contact Action Services Group today by calling 610-558-9773 or email info@actionservicesgroup.com! You can also schedule a call by clicking the button below.

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