Human Bio 11

* Ultraviolet radiation has three different wave lengths – UV-A, UV-B, and UV-C.

UV-A starts the tanning process before the skin burns and has the least cancer risk.

UV-B the tan is darker and longer lasting but tends to produce burns before it tans. It is a known cancer risk.

UV-C has most energy but the least penetrating. Dead layers of skin stop UV-C radiation, but it is dangerous to living cells having carcinogenic effects.

The sun produces rays….

Ultraviolet Spectrum

100-280 280-210 310-400

UVC UVB UVAX rays Visible

Skin Cancer

Skin Cancer

• The major factor in skin cancer formation is sun exposure

• Skin type is also important in dictating how the skin reacts to the sun

Basal Cell Carcinomas

• Commonest skin cancer in Caucasian populations

• Major cause is sun exposure• Common sites on face and trunk• Not metastatic

Squamous cell carcinoma• Second most common skin cancer in Caucasian

populations• Caused by sun exposure - chronic sun exposure• Most at risk are those with pale skin who burn in

the sun• Commonest on sun exposed areas• Pre-cancerous lesion is the solar keratosis• Metastatic potential - to regional lymph nodes,

then liver, lungs etc

Melanoma

• Third most common skin cancer• Caused by severe intermittent bouts of sun

exposure• Found on sun exposed and non-exposed sites• Second most common cancer to affect young

women• High metastatic potential - local, lymph nodes,

lung, liver and brain

Melanoma

• 30% arise in a pre-existing mole– Features to look out for are asymmetry of the

mole, irregular shape and irregular colour

How can we prevent long term skin damage?

• Avoid sun• Avoid midday sun• Use photo-protective

clothing, hats etc• Use sunblocks

SandSEA

How sunscreen works

• Work either by reflecting or absorbing UV rays

• Most sunscreens protect us from UV-A and UV-B.

• Ingredients like zinc oxide or titanium oxide reflect or scatter ultraviolet (UV) radiation.

• Octyl methoxycinnamate (OMC) or oxybenzone absorb UV radiation, dissipating it as heat.

Sun Protection Factor

• Indication of the amount of time it is safe to spend in the sun without burning

• Ex: an SPF of 10 would allow an exposure ten times greater than normal