UVA and UVB Rays Broad spectrum UV radiation has been acknowledged as a human carcinogen by both the National Institutes of Health and the World Health Organization.
UV wavebands are categorized by their wavelength.
The two types of UV rays that reach the earth's surface are UVA and UVB.
Both types of rays do damage to your skin, but in different ways.
Characteristics of UVA Rays:

• Accounts for up to 95% of the solar radiation that reaches the earth.
  
• Have long wavelengths measuring roughly 320 to 400 nm.
  
• Penetrates into the deeper layer of the skin.
  
• Present year round, even in winter.
  
• Goes through clouds as well as glass.
  
• Is a major factor in skin aging and wrinkling.
  
• May also cause the development of skin cancer.
  

Characteristics of UVB Rays:

• Responsible for tanning, sunburn, and redness.
  
• Wave lengths are within the middle range of UV - between 290 to 320 nm.
  
• Mainly penetrates only the epidermis.
  
• Varies with the seasons, geographic location and time of day.
  

A few decades ago, tanning with baby oil was popular.
Most people did not know about or care to use sun screen.
Today, people are aware of the damage the sun can do to your skin such as pre-mature aging and skin cancer.
So how do you protect your skin from these sun rays and the damage they cause? The best line of defense is to stay out of the sun when the UV rays are the strongest - during the hours of 10:00 am to 4:00 pm.
However, it you are out during this or any time:

• Protect yourself with a broad spectrum (UVA and UVB) sunscreen that has a SPF of 20 or higher.
  
• Make sure to apply enough sun screen to all areas of your skin.
  
• Apply sun screen at least 30 minutes before going out into the sun and re-apply every 2 hours.
  
• Wear UV-blocking sun glasses to protect your eyes.
  
• Stay in the shade when possible.
  
• Wear protective clothing - ex.
  Wide brim hat, long sleeve shirt, UV rated clothing.
  
• Keep your sun screen cool.
  A sun screen's effectiveness will lessen when left to get hot.
  

Don't just assume you are safe, because it is cloudy or you are in the water.
UVA and UVB rays pass through clouds and water, and are just waiting to make you age before your time.
Also, check your local UV index when you are planning a day outside.
The UV index measures the amount of UV radiation reaching the earth.
It is a number between 1 and 10 with 10 being the strongest.
You can find your local UV index by visiting epa.
gov/sunwise/uvindex.
html.
Be sure to use a good UVA and UVB protective sunscreen.
While a product's SPF is important, research has shown that protecting from both types of UV rays is just as important.
Older sunscreens protected the skin from UVB rays, but as science has learned, it is the UVA rays which play a bigger role in the cause of skin cancer.
Today's sun screens combine several different ingredients for UVA and UVB protection.
Broad spectrum sun screens contain traditional UVB filters and newer UVA filters such as avobenzone (Parsol 1789).
Although, avobenzone becomes unstable with exposure to sunlight, and therefore less effective, recent advances have solved this problem.
Newer products now contain the trademarked names "Helioplex" and "Mexoryl SX".
So look for products with these ingredients and have a safe, fun time in the sun!