What is Ultraviolet Radiation
Ultraviolet radiation is a type of energy produced by the sun, as well as some artificial / manmade sources. While it has some benefits for people, including the creation of Vitamin D, it also can cause health risks.
The sun emits 3 kind of UV radiation: UVA, UVB and UVC.
UVC Radiation
UVC radiation has a shorter wavelength and is absorbed by our atmosphere, also called our ozone layer, never reaching earth.
UVB Radiation
UVB radiation is most associated with sunburns. While UVB radiation is largely filtered by the earth’s atmosphere, its medium wavelength allows the rays to strike the top layer of our skin, the epidermis.
Sunscreens were first developed to protect us from UVB light, and now with broad spectrum sunscreens, UVA light as well. The Sun Protection Factor (SPF) on sunscreens lists how long it would take the suns rays to redden your skin when using the product, compared to the time it would take without it. However, it is important to note that the SPF only measures protection from UVB light, not UVA.
The amount of UVB radiation that reach the Earth’s surface depends on latitude, altitude, time of year and other factors. In general, in the United States, the more harmful UVB radiation occur during the hours of 10:00AM to 4:00PM. Even on a cloudy day you can be sunburned by UVB radiation, so it’s always a good idea to check the UV Index when planning outdoor activities.
In addition to sunburns, the UVB radiation can also cause skin cancer and premature aging.
UVA Radiation
Unlike UVB and UVC radiation, UVA radiation is not filtered at all by the earth’s atmosphere and accounts for 95% of the UV radiation reaching the earth. Its rays can also pass through glass and cloud cover. UVA rays are less intense, but their longer wavelength allows it to penetrate the skin more deeply, causing skin cancer and premature aging.
Only sun screens that are “broad spectrum” can protect against UVA radiation.
