What is the difference between UVA and UVB rays?
UVA is long wavelength (320-400 nm) UV and accounts for up to 95 percent of the solar UV radiation reaching the Earth’s surface, according to a press release from The Skin Cancer Foundation called “Shining Light on Ultraviolet Radiation”. It can penetrate into the deeper layers of the skin and has for years been thought to play a major part in skin aging and wrinkling. Importantly, recent studies strongly suggest that it may also initiate and exacerbate the development of skin cancers. UVA rays are present during all daylight hours and throughout the winter months.
Although UVA rays are less intense than short wavelengths, (UVB) they are present all year round and depending upon the time of the year, can be 30 to 50 times more prevalent than UVB rays. Furthermore, UVA radiation can penetrate glass and clouds. Thus we are exposed to large doses of UVA throughout our lifetime. UVB is the middle range of UV with wavelengths between 290-320 nm. It is very biologically active and is responsible for burning, tanning, and acceleration of skin aging, and plays a very key role in the development of skin cancer. The intensity of UVB varies by season, location and time of day. The most significant amount of UVB hits the U.S. between 10am and 4pm between April and October.