UV awareness

The dangers of UV exposure

In addition to radiating light and heat, the sun emits invisible ultraviolet (UV) rays. Most of these UV rays never reach the Earth. Two exceptions are UVA and UVB rays, which are what are referred to when we are talking about UV exposure.

UVA rays constitute approximately 90-95% of the rays that reach the Earth’s surface.

• They are present year-round.
• They penetrate deeper into the skin’s layers.
• They cause tanning.
• They are associated with visible signs of premature aging, such as wrinkles and skin discolouration.

UVB rays make up only about 5-10% of the rays that reach us.

• They primarily affect the skin’s outer layer.
• They are the primary cause of sunburns (even on cloudy days!) and the signs of premature aging.

Understanding the UV index

The UV index is used to measure the intensity of the sun’s UV rays. In Canada, that intensity is rated on a on a scale of 1 to 11 (with 11 being the highest value). The daily UV index forecast is a prediction of the maximum UV strength for the day, which is usually reached in the early afternoon.

Level	UV index	Precautions
Low	1 to 2	Minimal sun protection required for normal activities. Wear sunglasses on sunny days. If you are outside for more than one hour, cover up and use sunscreen.
Moderate	3 to 5	Take precautions. Cover up, wear a hat and sunglasses, and apply sunscreen – especially if you are otside for 30 minutes or longer. Find shade around midday, when the sun is at its strongest.
Elevated	6 to 7	Protection needed. Avoid sun exposure between 11 a.m. and 4 p.m. Take every precaution: seek shade, wear a hat and sunglasses, and apply sunscreen.
Very elevated	8 to 10	Additional precautions needed. Avoid the sun between 11 a.m. and 4 p.m. Take every precaution: seek shade, wear a hat and sunglasses, and apply sunscreen. Unprotected skin will be damaged and can burn quickly.
Extreme	11 or more	Take all precautions. Avoid the sun between 11 a.m. and 4 p.m. Cover up, wear a hat and sunglasses, and apply sunscreen. Unprotected skin will be damaged and can burn in just a few minutes.

Factors that affect your exposure to UV rays

• Time of day
  UV rays are strongest when the sun is at its highest in the sky (usually from 11 a.m. to 4 p.m.).
• Time of year (season)
  Here in Canada, the sun's UV rays are strongest during the summer months (May to August). It's important to remember that UV rays reach the Earth every day, year-round (yes, even in winter!).
• Type of surface
  Concrete, sand water and snow can reflect 85% of the sun's rays back at you.
• Elevation
  The higher the elevation, the greater your exposure to UV rays.
• Location
  UV rays are strongest as you near the Equator.
• Exposure time
  The longer you are out in the sun, the more you are exposed to UV rays.
• What you are wearing
  Exposed and unprotected skin absorbs more UV rays.
• Your skin type
  If you have fair skin, as well as light-coloured eyes and hair, you're likely to burn more easily when exposed to UV rays.