UVB rays, which affect skin's top layer, cause skin cancer and most sunburns. Although UVA and UVB rays pose the greatest risk for sun damage, people who work with welding torches or mercury lamps may be exposed to UVC rays, the most dangerous type of UV radiation.

Which is more harmful UVA or UVB?

UVA rays can penetrate your skin more deeply and cause your skin cells to age prematurely. ... The other 5 percent of UV rays are UVB. They have higher energy levels than UVA rays, and typically damage the outermost layers of your skin, causing sunburn. These rays directly damage DNA and are the cause of most skin cancers.

Which UV light is most dangerous for humans?

Short-wavelength UVC is the most damaging type of UV radiation. However, it is completely filtered by the atmosphere and does not reach the earth's surface. Medium-wavelength UVB is very biologically active but cannot penetrate beyond the superficial skin layers.