I listen to AirPods, closed headphones and speakers. None of them have ever caused an infection. I don't listen for many many hours without stopping for a break though. I don't think any of us do. The batteries won't hold out long enough. This whole "dangerous thing" is silly. It doesn't exist in practice.
There is no problem with volume either. Danger from "delivering sound into the ear canal" is a myth. AirPods do not create much volume at all. They are not dangerous.