Hi RO,
I am not sure if your question can be adequately addressed without knowing
what amounts of these chemicals are being used.  We were concerned about
toxicity too, and ended up going with Jim Arjuna's "Haven Spa."
http://www.havenspas.com/  I just have to plug this company -- their product
is so superior, and I feel we are getting the lowest levels of chemical
exposure possible.  The website tends to look like an engineering masters
thesis in places, but I think you'll find that a welcome change after the
shallow sales tactics of spa dealerships.  They ship just about anywhere
too.  Good luck.
CK

Ro <[log in to unmask] wrote:
"...I have a question.  For health and therapy reasons, we're looking at
getting a home spa/hot tub.  I need the heated water to work with
relaxing tendons drawing up from RSD, among other things.  Does anyone
here have an idea of how the various chemical treatments might be from
a paleo-healthful perspective?  ...Thanks, Ro"