VG is an organic compound that our lungs metabolize, as previously mentioned. Windows do not metabolize anything.
If our lungs did not metabolize VG, and it built up like it can on windows, then most of us would be dead by now, after a year or so of vaping. Something must be working.
For those worried that 40 years from now, we will suddenly learn that we are drowning in unmetabolized VG, consider this...
Many of us long term (30-40+ years) quit smoking and started vaping when our lungs had deteriorated to the point where if we kept smoking we believed that within 5 years or so we would be hauling O2 bottles around. We believed that because we were intimately familiar with the effects that continued loss of lung capacity was having on us.
Now, let's assume vaping is as bad for us as smoking, in terms of lung degradation such as COPD. When we stopped smoking the clock did not reset to zero. If one were to believe, based on their assessment of their lung degredation, that 5 more years of smoking would land them in full blown emphysema land, and if vaping would result in the same thing in a never smoker after 40 years, then another 5 years of vaping, on top of their prior smoking history, should result in the same outcome.
But in fact, people ready to order O2 bottles quit smoking, started vaping, and their lung capacity has only increased. So I have a lot of trouble with the "we haven't done this long enough to know" card. People here have been vaping for 5-7 years now, many of them were in bad shape when they started vaping, but we are not hearing about people continuing to experience the continued lung degradation that we would expect.