|How Does the Sun Couse Skin Cancer?|
Around 30 Australians are diagnosed with melanoma every day and more than 1,200 die from the disease each year.
While small amounts of ultraviolet (UV) radiation are required for the production of vitamin D to keep bones and muscles strong and healthy, skin can burn from just 15 minutes of exposure to the summer sun.
In 2009, the World Health Organization (WHO) classiﬁed the whole ultraviolet spectrum and the use of solariums as carcinogenic to humans, placing them in the same category as asbestos and tobacco. The majority of skin cancers in Australia are thought to be caused by exposure to UV radiation in sunlight.
The sun emits three different types of UV radiation: UVA, UVB and UVC. While UVC rays are filtered by the ozone, 10% of UVB and 95% of UVA rays reach the earth’s surface.
What is UV?
There are 2 main types of UV rays that damage our skin. Both types can cause skin cancer:
- UVB is responsible for the majority of sunburns.
- UVA penetrates deep into the skin. It ages the skin, but contributes much less towards sunburn.
A third type of UV ray, UVC, could be the most dangerous of all, but it is completely blocked out by the ozone layer and doesn’t reach the earth's surface.
What is sunburn?
Sunburn is a clear sign that the DNA in your skin cells has been damaged by too much UV radiation. Getting sunburn, just once every 2 years, can triple your risk of melanoma skin cancer.
Sunburn doesn’t have to be raw, peeling or blistering. If your skin has gone pink or red in the sun, it’s sunburnt. For people with darker skin, it may just feel irritated, tender or itchy.
You can’t feel UV rays – the heat from the sun comes from infrared rays, which can’t burn you. This is why people can still burn on cool days.
What happens to my skin when it burns?
Too much UV radiation from the sun or sunbeds can damage the genetic material (the DNA) in your skin cells. If enough DNA damage builds up over time, it can cause cells to start growing out of control, which can lead to skin cancer.
Your body has ways of repairing most of the damage. But it is not perfect – some damaged DNA can be left behind. Your body's attempt to repair this damage is what causes the painful symptoms of sunburn.
Skin cancer growth
The top layer of skin, the epidermis, contains three different kinds of cells:
- squamous cells that make up the top outer layer of the skin
- basal cells that make up the lower layer and produce new skin cells as old ones die off
- melanocytes are the bottom layer of the epidermis that produce pigment called melanin, which gives the skin its colour.
Cancer begins when normal cells change and grow uncontrollably. The tumour can be benign (non-cancerous) or malignant (cancerous, and can spread to other parts of the body).
The three major types of skin cancer – melanoma, squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) – are defined by the cell type of the skin from where they develop.
Can skin cancer spread?
Melanoma and non-melanoma skin cancers can be invasive. As well as growing across the surface of the skin, tumours can sometimes grow down through the layers of skin. If the tumour grows through the wall of a blood or lymph vessel, cancer cells can break off and spread to other parts of the body. This is why skin cancer is usually easier to treat successfully when it is caught at an early stage.