What can UV radiation from the sun pass through? Can it be stopped?!

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Offline AJ153

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What can UV radiation from the sun pass through?  Can it pass through any of these materials Opaque/semi Opaque?
-  House glass (ones in everyday normal windows)
-  Cardboard  (used for packaging)
-  Paper
-  Plastic
-  Water
-  Cloth (Like window blinds)
-  Metal
-  Umbrella
As I grow older I'm more curious in UV protection  for home,car, and outdoors since my family has a history of skin problems caused by sun UV Radiation, I remember learning this in Chemistry class, but I totally forgot about what UV can penetrate through.
Thank you for reading.


Offline evan_au

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Earth's ozone layer filters out about 97% of ultraviolet light. The ozone layer is showing signs of recovery from CFC degradation after the Montreal Protocol.

Measuring & documenting UV blocking is complicated by the presence of 3 different kinds of UV (called UVa, b & c) at different wavelengths. They are absorbed by different amounts by different materials, and have different effects on the skin. http://en.wikipedia.org/wiki/Ultraviolet#Skin

Metals reflect all UV - so a metal roof is good protection. But beware - UV also reflects off many items in the environment, including air, clouds, water, snow and trees; just because you are shaded from direct sunlight by a metal roof does not entirely protect you from UV rays.

The best personal protection comes from sunscreen, which can be applied all over, like moisturiser cream. However, the common SPF labeling does not measure UVa protection. UVa does not cause sunburn, but it can still cause some DNA mutations, which may eventually result in skin cancer.

Glass absorbs a lot of UV: http://en.wikipedia.org/wiki/Transparency_and_translucency#UV-Vis:_Electronic_transitions

Cloth & clothing differs considerably in its UV protection. Clothes designed specifically as beachwear are sometimes designed and advertised as having quite high UV protection ratings; other clothes leave it unspecified, but in general, the more layers, the better protection.

As well as the intensity of the UV, duration of exposure is also important - if you are at risk, don't plan on spending all day in the Sun, even if you are wearing sunscreen.

If you have a family history of skin cancers, you should have a regular checkup by your GP, and point out any moles or marks that have changed.

If you manage to screen yourself entirely from UV, bear in mind that some UV light is important for Vitamin D synthesis - a few minutes per day of Sun exposure is recommended. With our modern indoor lifestyles, many people now need Vitamin D supplements for current health and long-term bone strength.