Science on Prolonged Wearing of Mask.

You will appreciate the quote below:

“When you do a study, not only do you need to identify the adverse  effects, but you need to determine the exposure to these conditions. If a  person works a 40 hrs week and he commutes by public transport we can  say that this person will wear a mask on average for 45 hrs per week.  This doesn’t take into account all the other public places the person  needs to wear a mask, such as the groceries or restaurants. So let’s  assume the average North American is forced to wear a mask for 50 hrs  per week. How do we evaluate the health hazards of a 30% oxygen  impairment for 50 hrs per week over a 4 to 6 months period or more?” –  G. V.