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Why Block Out UV? What's the Science

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Tuesday, January 29, 2013 - 2:30pm

People believe that regular window glass blocks all UV radiation from the Sun. This is not true. Many people wear sunglasses and sunblock to protect them from UV but do not realize that UV also enters their homes and businesses through their windows and can cause them harm.

What is UV?
The Sun emits a great amount of energy. This energy includes the visible light that everyone enjoys. UV is a type of radiation that has a shorter wavelength than visible light and can cause damage to organisms on a cellular level. The ozone layer is a protective barrier in our stratosphere that absorbs most UV radiation, but not all of it. UV radiation comes in three types:

UVC: Completely absorbed by the ozone layer and oxygen.
UVB: Partially absorbed by the ozone layer.
UVA: Not absorbed at all by the ozone layer.

You have probably heard that we are losing portions of the ozone layer. This is true. Human activity releases chemicals into the atmosphere that depletes ozone. This has always happened but people have accelerated the amounts following the Industrial Revolution. This results in more UV reaching the Earth's surface. The ozone layer's thickness can also vary based on the time of year or weather.

Other factors can affect the amount of UV we receive, such as the angle of the Sun. At noon and during summer, the Sun's rays have a shorter distance to travel through our atmosphere and less UV can be absorbed before it hits us. UV is also stronger the closer you are to the equator and the higher your altitude, as the Sun's rays have a shorter distance to travel. Finally, cloud cover can block some, but not all, UV rays.
 
Effects of UV:
UV causes damage on the cellular level in human beings and this can lead to health problems.
This is caused by UVA and UVB radiation penetrating and damaging your skin cells. The cells die and the body gets rid of these and brings in new cells. This is what happens when your skin starts to peel. The real problems begin when cells are damaged but do not die.

The damaged cells act abnormally and do not function properly. This can lead to cancer. UV rays can also damage eye cells and lead to reduced vision or blindness. The effects of cellular damage are cumulative, meaning that damage builds up over a long period of time.

Methods for limiting UV exposure:

Solar blinds and shades: An inexpensive way to block UV rays while still letting in light. Solar blinds and shades come in a variety of styles and colors, so many people prefer this as a more traditional way of treating windows.

UV glass: A more expensive, but effective way of blocking UV. This specialized glass is made with UV blocking properties built-in. Many office buildings use this method of blocking UV to protect their employees but it doesn't look very good in a home.

UV film or coatings: Materials that can be applied to existing windows in your home. This is basically the same concept as car window tinting. More difficult to implement than solar blinds but just as effective in blocking UV.

Find out what type of windows you have and then take action to limit your exposure to UV. A little bit of preventative action right now can go a long way towards keeping you safe and healthy in the future.  

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