I needed to disable self sign-ups because I’ve been getting too many spam-type accounts. Thanks.
Vitamin D, good or rat pioson?
The ratio of UVA:UVB hitting the Earth's surface changes throughout the day with sun angle and weather. There's no fixed ratio. I've been using a Sperti Vitamin D lamp for 2 years now and haven't experienced any burning sensation, and I'm a white person living in Alaska, so my skin is about as pale as skin gets without being albino. Probably a good idea to be cautious if you didn't feel good using it, but if you want UVB exposure to produce Vitamin D naturally, the Sperti is probably the safest lamp. UVA is supposedly the part of the spectrum most responsible for skin cancers and skin damage, although you still wouldn't want to sit in front of intense UVB for more than the suggested time, which is 1-5 minutes approximately every other day. Most glass windows filter UVB but not UVA which is why you can get a sunburn from light passing through glass but not make Vitamin D from that light.