Sun's effect on human skin

As you no doubt know, exposure to sunlight causes vitamin D to be produced in your skin. But only a portion of the solar spectrum, known as ultraviolet B (UVB), that has this effect. Other parts of the solar spectrum can have very different and even harmful effects .
Malignant melanoma has been increasing at an exponential rate in indoor workers since before 1940. The reason may be indoor exposure to UVA radiation. Unlike UVB, which is blocked by glass, UVA can pass through windows.