Politics. Perchlorate occurs naturally around the world and even on Mars. I'm concerned about many other pollutants, but not perchlorates. Human beings have been extremely high doses of the substance as the standard-of-care for several thyroid diseases for decades without any of the awful effects that activists are alleging. The studies I've read about don't even begin to suggest cause-and-effect.
Possible toxicity. California has more stringent regulations than most other states and has warning s against perchlorate and other chemicals that other states don't worry about. Follow these cautionary indications to be extra safe.