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Why does ultraviolet light cause skin cancer?

by | May 5, 2019 | Uncategorized | 0 comments

It has been proven that 99% of non-melanoma skin cancers and 95% of melanomas are caused by too much exposure to UV radiation from the sun or other sources such as sunbeds and sun lamps. But why? You hear about the dangers of UV exposure all the time, but today we’re going to look at the root causes behind the damage.

Let Associated Dermatologists help you get to know some important facts about this main factor that causes skin cancer. We’re a group of local dermatologists proudly serving Birmingham, Alabama and the surrounding areas.

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What is UV Radiation?

A form of electromagnetic radiation primarily from the sun. Although there are also several man-made sources such as tanning and welding torches, sunlight is the main natural source of UV rays.

What types of UV rays cause skin cancer?


UVA Rays

UVA rays penetrate deeply into the skin and that causes skin-aging in the form of genetic damage to the cells. This is the type of UV rays that are responsible for long-term skin damage such as wrinkles, blotchiness, and skin cancer. Tanning beds give off large amounts of UVA which is proven to increase the risk of skin cancer.

UVB Rays

The main cause of sunburns are the UVB rays which are a significant risk factor for skin cancer. This type has slightly more energy than UVA rays. UVB exposure can damage skin cells’ DNA directly because the rays penetrate into the epidermis or the top layer of the skin.As mentioned above, both types of UV rays damage the skin and cause skin cancer but UVB rays, are the more potent cause of at least some skin cancers. But still, there are no safe UV rays.

Factors affecting the strength of the UV rays

  • Time of the day – UV rays are the strongest between 10 am to 4 pm
  • Season of the year – They are stronger during spring and summer months
  • Latitude or the distance from the equator – exposure to UV rays goes down as you go further north or south in latitude
  • Altitude – Higher elevations are reached by more UV rays
  • Cloud cover – Some types of clouds can reflect UV light, increasing UV exposure. So it’s important to note that UV rays can get through even on a cloudy day.
  • Surface reflection – Water, sand, snow, pavement or grass can reflect UV rays onto your skin leading to increased UV exposure.

The amount of UV exposure a person gets depends on the strength of the rays, the duration of time the skin is exposed, and whether the skin is protected by sunscreen or clothing.

Who is at risk of skin cancer?

  • People who live in areas with year-round, bright sunlight
  • People who spend a lot of time outdoors without protective clothing or sunscreen
  • Children who get frequent sunburns increase the risk of skin cancer years or decades later

Other effects of UV rays

  • Sunburn
  • Tanning
  • Skin-aging
  • Wrinkles
  • Loss of skin elasticity
  • Dark patches or lentigos. Also called age or liver spots
  • Pre-cancerous skin changes e.g dry, scaly, rough patches called actinic keratoses
  • Cataracts and other eye problems
  • Immune suppression

In general, darker-skinned people are less likely to get skin cancer than light-skinned people. But still, they can get cataracts and also might face issues with immune suppression. That’s why EVERYONE should take measures to protect themselves from both UVA and UVB rays.

What are the Exact Reasons why UV Light Causes Skin Cancer?

As I mentioned earlier, we’re going to dig deeper than most articles and look at the exact mechanisms behind the link between UV exposure and skin cancer. The bottom line is that UV rays modify the expression of a large number of genes within skin cells. One well-known modification is the “signature mutations” to the p53 gene referenced in the abstract of this study. The p53 gene is responsible for helping to regulate cell cycles and is thus an important part of cancer suppression. Mutations to this gene can cause cells to grow uncontrollably. Changes to the Sonic Hedgehog pathway (yes that really is a thing!) specifically cause PTCH1 and SMO mutations which may contribute to Basal Cell Carcinoma. The action is different from the p53 gene mutation, but the end result is similar: cells are allowed to grow uncontrollably because the PTCH1 “off switch” is not properly limiting the cellular reproduction function controlled by the SMO signals.


Root Causes: As you can see above, genetic mutation and alterations to the signaling pathways of our DNA caused by both UVA and UVB rays contribute to the risk of skin cancer.

If you have questions about your skin condition, don’t hesitate to talk to a trusted dermatologist like Associated Dermatologists to get professional advice and expert opinion. Better safe than sorry!

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