It's bad chemistry
Are you kidding me? Water is made from hydrogen and oxygen. It can be broken down by radiation and possibly reformed into O2, O3 (ozone), H2, and H2O2 (hydrogen peroxide).
Claiming water is capable of "forming about every type of toxic substance around in quantity" solely in the presence of radiation is about as loony a scientific claim as those of Barry D. While ozone and peroxide are toxic in large enough quantities most toxic compounds are organic containing mostly carbon or contain much higher molecular weight inorganic chemicals such as arsenic, Tin, and lead.
Regards,
Mark