The sun and ultraviolet (UV) light

Tip: Even on a cloudy day you are still exposing your skin to both UVA and UVB radiation, so wear sunscreen even if the sun isn’t shining!

The ozone layer is an atmospheric layer around the Earth that blocks most (not all) of solar UV radiation. It is the Earth’s sunscreen!

UV Index is the level of solar radiation at the Earth’s surface. The index goes from 0-11. The higher the index value, the greater the potential that the sun will damage our skin and the less time it will take for the damage to occur. News reports usually give the UV Index daily as a reminder to protect our skin.

The sun gives off invisible radiation of ultraviolet light (UV). UV light is part of the solar emissions that include light, heat and UV radiation. UV radiation covers a wavelength range of 100-400 nm and is divided into three bands: Ultraviolet A, ultraviolet B and ultraviolet C. All three bands of UV radiation are classified as a human carcinogen, meaning that it induces cancer.

Ultraviolet A (UVA) has a long-wavelength, covering 315-400 nm and is not significantly filtered by the atmosphere. It makes up approximately 90% of the UV radiation that reaches the Earth’s surface. UVA rays can also harm the skin and penetrate the skin more deeply than UVB radiation. UVA rays damage the DNA of cells in the dermis, the second layer of skin, causing wrinkles and skin cancer.

Ultraviolet B radiation (UVB) covers a wavelength range of 280-315 nm and comprises 10% of the UV radiation that reaches the Earth’s surface. UVB rays are short, high-energy wavelengths that are absorbed by the epidermis, the outermost layer of skin. UVB rays affect the genetic material of the epidermis, which can cause damage that may lead to skin cancer, including melanoma. UVB radiation can also affect the body’s immune system and interfere with the skin’s ability to repair itself.

Ultraviolet C (UVC) is a short-wavelength radiation, covering 100-280 nm. All of solar UVC radiation is absorbed by the ozone layer and does not reach the Earth’s surface.
You should always always always put on sunscreen with a sun protection factor (SPF) of at least 30 before going outside. Even on an overcast day, UVA and UVB rays can damage your skin.
A sunscreen’s SPF is a laboratory measure that grades how much UVB a sunscreen can block. The measurement goes from 2 upwards.

Some factors that influence UV radiation levels include:
• altitude
• cloud cover
• surrounding surfaces
• latitude

Sunlight: A Story of Good and Bad
Good Effects of Sunlight
• Warmth
• Helps plants grow
• Synthesizes vitamin D in our body
• Kills germs
• Helps with mood
Bad Effects of Sunlight
• Sunburn
• Wrinkles
• Effects the immune system
• Skin cancer
• Damages the eyes

Fact: UV radiation does not only affect the skin. It can also have harmful effects on eye health. Cloudiness or cataracts appear to different degrees in most people as they age, but frequent unprotected sun exposure worsens their development.

Individual risk factors for skin cancer:
• fair skin
• blue, green or hazel eyes
• light colored hair (red, blonde or light brown hair)
•tendency to burn rather than suntan
•history of severe burns
•many moles
•freckles
•family history of skin cancer

Some people can sunburn easily when out in the sun without protection. Others may take much longer to burn, but they still need to protect themselves because the sun can still damage their skin.

Good sun habits:
• limit sun exposure between 10 am and 4 pm
• be in the shade whenever you can
• wear a hat and sunglasses when outside
• wear sunscreen every day
• wear a shirt with long sleeves when you can
• pay attention to the daily UV Index

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