Toxic Effects of Ultraviolet Radiation on the Skin
Skin damage from sun exposure is caused by ultraviolet (UV) radiation. Not all the sun’s rays have the same effects. Some wavelengths of UV radiation penetrate the skin more deeply than others.
Realising this difference has prompted researchers to question whether some types of UV rays mainly cause wrinkles and brown spots (sometimes called “age spots” or “liver spots”) while others speed the development of skin cancer. The wavelengths of UV radiation fall between those of visible light and x-rays. The sun’s UV radiation reaches the earth in three main wavelengths.
- UVC. is wavelength is the shortest of the three. It also has the highest energy level and is the most damaging. UVC rays are capable of destroying the skin, but they’re usually absorbed in the atmosphere by the ozone layer before they reach the earth’s surface. In the 1970s, concerns about holes in the ozone layer led to global bans of ozone-depleting chemicals; the ozone layer now appears to be repairing itself.
- UVB. These rays are slightly longer and lower in energy than UVC rays, so they’re less damaging to skin. They make up around 5% of the ultraviolet radiation that reaches the earth’s surface. UVB rays penetrate the epidermis, and the visible result of their damage is a sunburn. Experts generally believe that the more often you’ve been sunburned, the more likely you are to develop melanoma. Research suggests that UVB rays cause a distinctive genetic mutation that permits unabated cell growth, giving rise to cancer. In fact, more than 90% of squamous cell cancers have this specific mutation.
- UVA. The rays with the longest range of wavelengths, called UVA, also play a role in photoaging and in the development of skin cancer. About 95% of the UV radiation that reaches the earth’s surface is UVA. Because of their longer wavelength, these rays penetrate more deeply into the dermis. Only about 10% of UVB rays reach the dermis, but researchers believe that 50% of UVA rays do so.