UVA
The sun's rays reaching us here on planet earth consist of either UVA, UVB or UVC ultraviolet rays. 'A' rays are 320-400 nm, while UVB are only 290-320 nm. UVC rays are the shortest and are stopped by the ozone layer. The diagram below illustrates how the UV rays fit into the wider Electromagnetic Spectrum as well as their different lengths.
Wavelength (nm)
Historically, sunscreens were made to encourage us to obtain a great tan. However, since the advent of skin cancer research persuading us to wear sunscreen (or sunblock), most sunscreens were made to block the UVB rays only, the ones that cause sunburn. Until fairly recently, most sunscreens were not made to block the UVA rays.
So, having been encouraged to wear sunscreen, many people religiously apply them whenever spending time outdoors. In fact, they spend a longer time in the sun than they would normally without sunscreen, as they don't feel any sunburn effect. So, this in effect means that they get exposed to UVA rays for a longer time than they would normally. With the availability of higher and higher SPF products allowing individuals to spend greater amounts of time in the sun without burning, concerns have been raised about the adequacy of the related ultra violet 'A' protection of these products.
Over exposure to these rays accelerates the photo-aging process of your skin. When you spend a long time in the sun, unprotected from ultra violet A, this type of radiation can chemically transform and excite certain acids in your skin that then contribute to photo-aging pigmentation changes, fine lines and wrinkles.
Common signs of advanced photo-aging include extreme leathering, sagging, and wrinkling of the skin. Chances are you've seen men and women with skin that appears tough, coarse, creased with deep wrinkles, and of course are also very tanned. This is a prime example of someone suffering from sun damage due to too much exposure to UVA rays. These people tend to have been exposed to long hours in the sun over many years. Examples are those that work all day in the outdoors; participate in sports involving long hours in the sun; or even are just classic sun worshippers who like to lie for many hours in the sun to obtain a tan.
Some medical experts now believe that while UVA may not be directly responsible for skin cancer, the damage it does to the skin can enhance the UVB skin damage as well as further development of the skin cancer caused by the UVB ray exposure. In order to protect yourself and your family from the damaging effects of both ultra violet A and B rays, it is really important that you develop excellent sun care habits while accumulating good information to enable you to choose healthy sunscreen products. When applying the sunscreen, make sure you stay protected by reapplying your sunscreen after swimming or having sweated, or after a few hours in accordance with your SPF.
As a starter, choose a 'Broad Spectrum' sunscreen as it will provide protection from both ultra violet A and B rays. Beyond this, try and choose a sunscreen that contains ingredients that will help to boost the skins' natural ability to deal with the effects of the ultra violet A rays. These will typically include antioxidants.
The effect of sunlight on the antioxidants present in the skin is important. While moderate sun exposure actually helps to increase antioxidants present in the skin, inappropriate ratios of ultra violet A radiation or overexposure consumes and lowers the antioxidant levels in your skin.
No global consensus yet exists about the best method for measuring UVA protection although a huge amount of collaborative work has been done amongst various organizations to assess the different methods being used. A variety of methods have been proposed.
The following are the best known test methods for UVA certification:
