What are the effects of UVA light on skin?

The effect of UVA light on skin was thought to be negligible. However, 95% of the UV radiation reaching the earth's surface consists of UVA, which is known to penetrate deeper than UVB into the epidermis and the dermis. It is now strongly believed that UVA can cause severe long term damage.

Recent studies have shown that chronic exposure to UVA can cause, similar to UVB radiation, structural damage in DNA, skin cells, & cellular proteins, lipids and carbohydrates.

The UVA radiation is divided into two subsets:
UVAII 320 - 340 nm
UVAI 340 - 400 nm

Since the UVA I & UVA II have long wavelenghts, they are able to penetrate deep into the skin's dermis causing damage to the collagen and elastic fibers which give skin its shape, definition and suppleness, thus causing wrinkling and eventually premature skin aging.

What Protects Against UVAI & UVAII Rays?