The windows, they do nothing?

June 26, 2008 12:27 AM

How much UV damage am I getting sitting in a classroom for 5 hours with a big window.

I am taking a class in Jerusalem this summer and spend 5 hours a day sitting against the far wall facing a big window. It's not direct sun, just bright light coming in through the window.

Picture One
Picture Two

Anyone have any idea how much UV radiation is getting through there? Do I need to be putting on subblock every two hours? (Meaning 3 times for every single class?) Is there anything I can put on in the morning that would last for 5 hours?

Is the glass blocking enough of the UV rays that I don't have to worry?

posted by andoatnp to health & fitness (5 answers total)

The windows, they do something, but it's not 100%.

UVA causes skin ageing and research has now shown that it is also likely to cause skin cancer. UVB causes redness and sunburn and is a major risk factor for all types of skin cancer.

Most glass used for windows blocks UVB but not UVA. This means that although glass greatly reduces the risk of sunburn, it does not prevent long term damage from UVA. So, if you are driving long distances or sitting in your conservatory every day for long periods of time, you need to make sure you are using sun protection on sunny days. (source)

Similar information is found on this site, but, another site seems to be less clear on the amount that filters through. It appears that the consensus is that glass filters out UVB radiation, therefore, you're unlikely to get sunburned. However, if you're generally concerned about skin cancer, you may want to consider using sunblock.

One interesting (and related) thing I've read lately is that people are generally not getting enough sun exposure lately, resulting in more problems due to vitamin D deficiency. It seems that you can end up with far worse conditions than skin cancer if you hide from the sun all your life.
posted by knave at 12:49 AM on June 26, 2008

there is a graph of the transmission spectrum of various window (usually soda-lime) glasses here. a better graph here (pdf - curve #3) shows that in the UVB range (which causes sunburn) transmission is only ~15% at worst and drops off quickly as you go to lower, more damaging, wavelengths.

since you are not in the direct light anyway, your chance of sunburn is then almost negligible. don't worry about it.
posted by sergeant sandwich at 2:45 AM on June 26, 2008

As the glass only blocks sunburn-causing rays and not cancer-causing rays, I would still put on a sunblock. Especially on sensitive areas like my face. Most sunblocks should last five hours no problem, especially if you're not sweating or swimming.
posted by GardenGal at 6:47 AM on June 26, 2008

If you aren't in direct sunlight, don't worry about it. The indirect light is much weaker than direct sunlight.
posted by ssg at 8:34 AM on June 26, 2008

Behind glass Sunburn is dangerous not the radiation.
posted by armadillo at 11:06 PM on June 26, 2008