What are the health risks of hearing aids with Bluetooth capability? Should a couple hours a week of using hearing aids as Bluetooth devices be avoided or would that be harmless?

Exposure to such electromagnetic frequencies for only several hours per week would not likely produce pathology within a human being. But it is difficult to give precise recommendations here, because of the wide variability of individual vulnerability. So it is a good general rule of thumb to avoid dependency on the wireless sound technologies and use wired earphones or earplugs, as these will be inherently safe.