UV-A

Description

UV-A is a spectrum of Ultra-Violet Radiation with a wavelength from 320 nm to 380 nm (nanometers).  UV-AI is from 320 - 340 nm and UV-AII is from 340 - 380 nm.  Compared with UV-B there is thirty times more UV-A in the Ultra-Violet Radiation spectrum.

Environmental UV-A levels are more constant (do not fluctuate as much) than UV-B levels throughout the day and also throughout the year.

UV-A (unlike UV-B) is capable of penetrating through glass.

Cytokines

 UV-A may stimulate the production of Interleukin 12.  ^[1]

Cytokines

 UV-A exposure may inhibit the production of Tumor Necrosis Factor (TNF).  ^[2]

Aging Process

 Excessive exposure to UV-A may accelerate the Aging Process of the Skin - accelerated Aging of the Skin caused by UV-A Radiation is usually known as Photoaging and this process appears to occur as a result of Singlet Oxygen Free Radicals generated by UV-A.  ^[3]

Cells

 UV-A may decrease Gap Junction communication between Keratinocytes.  ^[4]

Eyes/Vision

 Excessive exposure of the Eyes to UV-A may increase the risk of Cataracts.

Immune System

 Excessive exposure of the Skin to UV-A may cause some types of Skin Cancer:  ^[5]

 Excessive exposure of the Skin to UV-A may cause Basal Cell Carcinoma.

Metabolism

 UV-A may stimulate the production of large numbers of Singlet Oxygen Free Radicals and much of the damage inflicted by UV-A is caused by these Singlet Oxygen Free Radicals.  ^[6]

Skin

 UV-A Radiation exposure may cause Immediate Tanning (i.e. transient, short-term Tanning) that occurs as a result of UV-A Radiation oxidizing the Skin's existing Melanin (compared to True Tanning which occurs as a result of UV-B Radiation stimulating the production of new Melanin).

 Although UV-A exposure does not cause Sunburn, excessive exposure to UV-A may damage the Subcutaneous Tissue of the Skin and its supportive Collagen, i.e. it may accelerate the Aging Process of the Skin (photoaging, which manifests as Wrinkles) - it is now believed that UV-A is the most damaging spectrum of Ultra-Violet Radiation.  ^[7]