UV radiation (especially UVC radiation) is readily absorbed by human DNA and has sufficient energy to damage it and create mutations. This is why the stratospheric ozone layer is so important – an intact ozone layer prevents the UVC radiation from striking the Earth and filters 95% of the UVB radiation. As atmospheric ozone concentrations decrease, the amount of UVC (and UVB) radiation reaching the earth increases, and the risk for mutations, cell destruction, and subsequent cancer increases.
UVB rays are absorbed primarily by the epidermis. UVB rays produce the redness and burning seen during sun exposure. These rays cause direct DNA mutations and generate oxygen free-radicals that can destroy and mutate cells and cause skin cancer. Sunscreen is an effective barrier against UVB rays.
UVA rays penetrate deeper into the dermis. UVA rays generate free radicals that damage collagen and elastin. It is UVA rays that are responsible for the aging process, including wrinkles, dyspigmentation, freckles, and loss of elasticity. Until recently, most sunscreens did not provide adequate protection against UVA rays.
But as bad as overexposure to UV can be, there are health benefits to be had if UV exposure can be moderated:
⌾ UV radiation is a good source of vitamin D which is important in the regulation of calcium metabolism, insulin secretion, blood pressure, and immunity. Vitamin D is also important to the body’s production of serotonin - a chemical that positively affects mood.
⌾ Moderate UV exposure increases the amount of the pigment melanin in the skin. Melanin absorbs both UVA and UVB radiation, protecting the skin from DNA damage.
⌾ UVB radiation can be used to treat skin conditions such as eczema, dermatitis, jaundice, psoriasis, and vitiligo.
⌾ UVC radiation can be used for a variety of industrial sterilization and disinfection applications as well as to purify water.