Most people are well aware of what time in the sun does to your skin, and the dangers that UVA and UVB rays pose to your health. However, if you stay indoors all day but by a window, are you still exposed to those sun rays? Can you top up your vitamin D while in the car? These are more difficult questions to which there are many myths floating around. Let’s take a look at what exactly can get through a window, and if it could have an effect on our health.
What do glass windows block?
There are three types of rays emitted from the sun – UVA, UVB and UVC. We don’t need to worry about UVC rays because these get blocked by the earth’s atmosphere. Both UVA and UVB rays can be harmful to the skin, causing a sun tan, sun burn or even cancer. However it is worth bearing in mind that we need some UVB rays to generate vitamin D.
Generally, ordinary glass such as the glass windows in your home can filter out UVB rays but not UVA sun rays. This means that sitting by the window on a sunny day will not increase your vitamin D intake – you’ll have to be outside to soak up the sun rays. However, you would still be exposed to UVA rays which are responsible for sun tans and freckles, and could cause long term damage.
This has led to dermatologists recommending that people should protect themselves from sunlight if they will be by a window for a long period of time – such as driving in a car. A study reported in the New York Times found that 74% of people at a skin cancer clinic had tumours on the driving side of their body, posing a possible link between the amount of time spent driving in the sun and developing skin cancer.
So can you burn through windows?
A double glazed window will block the majority of the sun’s UV rays, but not all of them. Glass blocks the most harmful rays which usually cause sunburn, so it is very unlikely that you’ll get burnt from sitting in your conservatory for a couple of hours. However, remember that some sun rays do get through glass, and although exposure to them may not result in sunburn, they can penetrate deep and cause skin damage.
Of course, in the UK climate it is unlikely we’d be basking in sunlight for long! But if you are worried about skin damage, in the summer you should wear sunscreen every day even if you don’t go outside.