UVA destroys Vitamin D in the body (many previous hints of this).
Window glass block most of UVA, but ALL of UVB – thus getting UV thru glass appears to decrease your levels of vitamin D.
This may be one of the reasons that truckers live much shorter lives:

UVA without UVB : lowering of vitamin D levels.
UVA + UVB: net increase in blood levels of vitamin D.

UVB only: larger net increase (a single hint that it might be 6x this has not been confirmed).
Some bulbs have just UVB.
There is a way to block all but UVB:i.e. block UVA and visible and IR (Heat) – see below: