I have a toaster oven / convection oven / air fryer combo and it doesn’t suffer from this issue.

Mainly, what I was trying to point out is aside from the grease issue that was pointed out, there’s nothing special about air fryers. Any issue aside from grease buildup would also affect convection ovens, which have existed for a long time with no ill effects noted. It’s just an electric heating element and a fan, they’re not doing anything that special. I don’t think they’re going to be found to be dangerous in the future.