This is a topic with multiple facets. If you are looking for more info on suncsreens, here's what appears to me to be a reasonable discussion on their effectiveness and some possible risks: https://www.choice.com.au/health-and...ides/sunscreen

From my reading, Acrylic, which I think most/all canopies are made of can be made to block UV with additives, but in its pure form it does not. So it depends on the specifications of the acrylic that was used in the manufacture of your canopy. I found one reference that suggests Mecaplex, who make canopies for many gliders, use an acrylic that "blocks 95% of UV": https://www.dg-flugzeugbau.de/en/lib...nopy-dg-glider

If anyone has a spec sheet for the acrylic used in their canopy, that would be interesting data.