UV Radiation

UV Radiation and SKIN
UVR is subdivided into ultraviolet A [UVA (315–400 nm)], ultraviolet B [UVB (280–315 nm)] and ultraviolet C [UVC (100–280 nm)].

Types of ultraviolet radiation and their General properties-

Ultraviolet A radiation (UVA)

-Approximately 90–99% reaches the earth’s surface
-Is not filtered by the stratospheric ozone layer in the atmosphere
-Long wavelength & low energy- can penetrate deeper into the skin
-Once considered harmless, but now believed to be harmful if one has excessive and long-term exposure
-Causes aging of the skin; induces immediate and persistent pigmentation (tanning)
-Passes through glass

Ultraviolet B radiation (UVB)

-Approximately 1–10% reaches the earth’s surface
-Filtered by the stratospheric ozone layer in the atmosphere
-Short wavelength & high energy- can penetrate the upper layers of the epidermis
-Responsible for causing sunburns, tanning, wrinkling, photoaging and skin cancer
-Carcinogenic and a thousand times more effective in causing sunburns than UVA
-Does not pass through glass

Ultraviolet C radiation (UVC)

-Filtered by the stratospheric ozone layer in the atmosphere before reaching earth
-Major artificial sources are germicidal lamps
-Burns the skin and causes skin cancer