UVA and UVB What Is It And What Does It All Mean?

Sunlight is a part of the radiation given off by the sun and ultraviolet (UV) light or radiation is a part of that. The sun’s rays contain three types of (UV) light: UVA, UVB and UVC. Nearly all skin cancers are caused by exposure to the sun or UV light/radiation, so we have to protect ourselves from it as best we can.


The ultraviolet light in sunlight damages the DNA in the skin cells, as well as causing premature ageing of the skin and eye damage (including cataracts). This damage can happen years before a cancer develops. We do need a small amount of sunlight to create vitamin D but during the summer months we get enough sun with a few minutes exposure outside peak times (10am to 4pm). And during the winter months two to three hours a week is enough.


UVA makes up most of our natural sunlight (up to 95 percent).  We can think of it as the part that causes ageing as it penetrates deeper, resulting in damage. Studies over the last 20 years have shown it contributes and may even initiate the development of skin cancer. One thing you may not be aware of is that UVA is present with relatively equal intensity during all daylight hours and throughout the year. It can even penetrate clouds and glass so we need UVA protection every day.

You may think a tan protects you but think again. Tanning or darkening of the skin is due to melanin being produced by pigment cells. The cells make this in an attempt to protect you from further UV damage and so your skin becomes darker. So a tan or darkening is a sign the skin has already been damaged. The good news is that the UVA protection in a sunscreen will help defend the skin against photoageing – changes to skin caused by chronic UVA and UVB exposure – and potentially skin cancer, so our advice is to slap it on!


UVB light can also burn the skin and cause skin reddening. It is the main cause of non melanoma skin cancer basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), which slowly develops in the upper layers of the skin (read our skin cancer facts for more information) .The intensity of UVB varies during the day and the year. But it can burn your skin all year round and reflective surfaces, such as water, bounce back 80 percent of the rays so they hit the skin twice2. These rays, unlike UVA, do not significantly penetrate glass and a sunscreen with a high SPF (sun protection factor) will help block UVB rays and prevent the skin from burning and damage that can cause skin cancer.


UVC is filtered out by the ozone layer, so we don’t need to worry about it – phew!


A UV index is a measure of how strong the UV is and we are very lucky to have this information live courtesy of Bermuda Cancer and Health Centre and the Bermuda Weather Service link to page.


To protect your skin, we suggest the following:


  • Tint windows of cars to protect from UVA;
  • Avoid being outside during the high risk times of day between;
  • 10am and 4pm and refer to the UV index on www.weather.bm;
  • Understand your skin index and the types of protection you need to prevent sun damage;
  • Use sunscreen and hats, UPF (ultraviolet protection factor) clothing and sunglasses if you are out in the sun; and
  • Ensure infants under six months don’t have direct sun exposure as the use of sunscreen for them is not recommended by paediatricians.