So state them and report them. What specific dangers are you referring to? Do you have any sources to support this, or is it your own personal observations?
There have been studies regarding breathing, (I forget the names of the conditions as I had no idea what they meant) though iinm, the issues are rare and fairly minor, despite the fact that worn kids masks look absolutely revolting.
The main issues are harder to study, especially as their effects will take longer to manifest.
After speaking with parents, teachers, and principals from across the country with varying levels of masking required, from my own son who at most had a mask on his chin, to relatives who had their kids/students masked the entire day, the stress and anxiety it induces is real and extremely troublesome.
Kids are refusing to go to school, they've begun to throw daily temper tantrums, become sullen and withdrawn, and more. Teachers insist they are not able to absorb information as well, masks are significant boundaries in social development, and the like.
And then there is the massive feelings of responsibility and guilt if someone in the house does get covid despite the kid's masking.
I know this will be dismissed as anecdotal. And that's OK, I don't think I'll convince you. But the sheer number of people who express these things from every type of community you can imagine assures me the issues are real.
The amount of stress and anxiety I have before a flight picturing myself being in the next viral video because my 4 year old boy literally cannot keep his mask on for more than 20 minutes at a time is nuts. And I heard the same panic in the mom behind me on a flight with her 3 year old as she fought him the entire flight just this week, and I'm sure that's happening to hundreds every day. For what? How many cases have been traced to planes?