I am sorry that I have to ask a further question of chem geek but I think he maybe is one of the few persons on this forum that may be able to distill an answer from this technical paper on:
"Human & Environmental Risk Assessment on ingredients of
European household cleaning products
It discusses the toxicity of HEDP and is way beyond my understanding.
Any others of you that feel up to the task please chime in.
The reason for asking this question is that I plan to up the maintenance sequestrant level to 60 or 70 ppm, as measured by Jack's Sequestrant Test Kit, maybe even higher if it is safe enough, using Jack's Magic Purple Stuff, an HEDP sequestrant, to control iron staining. I am trying to find out at what level using Jack's Purple Stuff it might be too high, and therefore unsafe. The "Purple Stuff does add phosphates to the pool. I think and hope the answer can be found in this paper.
Jack's Magic Purple Stuff MSDS (Material Data Safety Sheet) is here:
This link speculates it contains 20% HEDP:
Thank you to those that might help.