https://www.wnd.com/2021/09/face-masks-children-ineffective-dangerous/

Some highlights from this article, which lists a plethora of studies, (with working links!) makes three points:

1. Masks are ineffective after about 20 minutes, since moisture builds up on them in about that much time.

2. Face masks can actually be harmful! (the JAMA published research on masks taking only about three minutes to expose children to dangerous levels of CO2 is worth the read in itself! https://jamanetwork.com/journals/jamapediatrics/fullarticle/2781743 )

3. Wearing a used mask is riskier than wearing no mask at all: (Physics of Fluids study- https://aip.scitation.org/doi/10.1063/5.0034580