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UV-radiation
The visible light has a wavelength of 400 to 760 nm. Ultraviolet (UV) light in sunshine is divided into three bands, or wavelength ranges, which are referred to as UV-A (95% of UV radiation), UV-B and UV-C.
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UV-A
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UV-B
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UV-C
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Wavelength
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long (320 – 400 nm)
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medium (280 – 320 nm)
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short (200 – 280 nm)
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Energy
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low
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higher than UVA
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high
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Penetration
depth
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high, >50% penetrates
into dermis
penetrates through glass
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low, mostly up to the
epidermis
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lowest, absorbed by
the stratospheric
ozone layer,
not relevant on earth
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Effects
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-grayish instantaneous
-late pigmentation after 24 h
-one of main reasons for
premature skin ageing
-involvement in causation
of skin cancer
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-brown pigmentation after
24 h
-reddening of the skin
-involvement in causation
of skin cancer
-produces vitamin D on the
skin
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marked reddening of
skin
high damaging potential
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As described above, UV radiation has positive and negative effects on the skin
The formation of free radicals plays an important role in photoaging. These chemically active atoms or molecular fragments can damage the large molecules within cells. The skin contains several protective factors and mechanisms for neutralising free radicals called antioxidants, such as certain enzymes, vitamin E and vitamin C. Acute and chronic UV-exposure may lead to a decrease of antioxidants in the skin and to subsequent oxidative damage of cell structures, proteins, lipids and the DNA.
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