UV-A solar radiation is scarcely attenuated by stratospheric ozone. Thus, the contribution of this spectral range to total UV radiation reaching at Earth’s surface is very high (about 90%). Although UV-A rays are less energetic, and so less dangerous than UV-B rays, the former can also induce detrimental effects on human health. For instance, a shocking case of “Unilateral dermatoheliosis” has been published in The New England Journal of Medicine. A 69-year-old man shows this syndrome which is associated with photo-damaged skin. He drove a delivery truck for 28 years and the left side of his face was particularly vulnerable to UV-A rays transmitted through window glass.
You can read the research note and see the striking photo at:
http://www.nejm.org/doi/full/10.1056/NEJMicm1104059