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.

Why is UVC the most dangerous?

So while UVC is the most dangerous because it's the shortest wavelength, it's not a risk to the typical person because the sun's natural UVC emissions don't penetrate skin. Remember, they actually do not even penetrate earth's atmosphere naturally at all. UVC is absorbed completely by the ozone layer.

Is UV more dangerous than UVB?

The rays that are most damaging to our skin are called ultraviolet (UV) rays. There are two basic types of ultraviolet rays that reach the earth's surface—UVB and UVA. ... There are approximately 500 times more UVA rays in sunlight than UVB rays.