UV Rays

The main cause of skin cancer is too much UV ray exposure. UV rays are invisible. The sun, tanning bed lamps and some workplace equipment produces UV rays.

Types of UV rays

There are three types of UV rays:

1. UV-A rays

UV-A rays make up most of the sun’s natural light.  They cause immediate tanning, premature aging and wrinkling of the skin.  These rays weaken the immune system and are common in tanning beds. 

2. UV-B rays

UV-B rays cause the most damage to skin.  They burn and tan skin, causing damage that lasts longer.

3. UV-C rays

The ozone layer absorbs UV-C rays so they do not reach earth. They are not a concern for humans.

Effects of UV rays

Too much exposure to UV rays from the sun and tanning beds causes more than just skin damage. Too much exposure to UV rays causes other effects such as:

  • Blindness – damage to the retina and increased risk of cataracts
  • Cold sore outbreaks
  • Darkened freckles or more freckles
  • More moles - causing increased risk of skin cancer
  • Scars – surgery to remove skin cancer can leave large visible scars
  • Skin cancer
  • Sunburn – one blistering sunburn before age 18 doubles the risk of skin cancer later in life
  • Sun spots – changes to skin colour over time; often light brown or black
  • Wrinkles – weakened skin leading to wrinkled, leathery skin

UV ray exposure in childhood and adolescence greatly increases the chances of developing skin cancer later in life.

UV Index

Environment Canada's UV Index is a measure of how strong the sun's UV rays are on a particular day.Check Hamilton’s UV Index for today.

How you should change your activities for each level of UV Index

  • The higher the UV Index number is, the stronger the UV rays are and the greater the need to protect yourself.

UV Index: 0 to 2
Level: Low

What to do to protect yourself:

  • Wear sunglasses on bright days
  • If you are outside for more than one hour, cover up and use sunscreen
  • Reflection off snow can almost double UV strength, so wear sunglasses and apply sunscreen on your face in the winter

UV Index: 3 to 5
Level: Moderate

What to do to protect yourself:

  • Cover up - wear a hat, sunglasses and sunscreen, especially if you will be outside for 30 minutes or more
  • Look for shade in the middle of the day when the sun is strongest

UV Index: 6 to 7
Level: High

What to do to protect yourself:

  • Cover up - wear a hat, sunglasses and sunscreen, especially if you will be outside for 30 minutes or more
  • Limit time in the sun between 11 am and 4 pm
  • Find shade in the middle of the day when the sun is strongest

UV Index: 8 to 10
Level: Very high

What to do to protect yourself:

  • Cover up - wear a hat, sunglasses and sunscreen, especially if you will be outside for 30 minutes or more
  • Limit time in the sun between 11 am and 4 pm
  • Find shade in the middle of the day when the sun is strongest

UV Index: 11+
Level: Extreme

What to do to protect yourself:

  • A UV Index higher than 11 is rare in Canada
  • The UV Index can reach 14 or higher in the tropics and southern USA
  • Cover up - wear a hat, sunglasses and sunscreen, especially if you will be outside for 30 minutes or more.
  • Limit time in the sun between 11 am and 4 pm
  • Find shade in the middle of the day when the sun is strongest
  • White sand, water, snow, and other bright surfaces reflect UV and increase UV exposure