"Will there be any negative effects on the bathers?"
I am not sure if you can put it in the hot tub and gain a medicinal benefit.
Other ways to absorb M.M. (medical marijuana) are: vaping; tinctures; teas; rubbing in topically and also under the tongue (sublingually).
The edibles go through the digestive tract and lose some of the CBD good effects( anti-infammatory), and may emphasize the "psychoactive" effects.