The American Environmental Protection Agency (EPA) had also commissioned a large number of studies on humans and animals on the consequences of oral ingestion of aqueous chlorine dioxide solutions or had summarised them from the literature.
Result: even 100 times the concentration of ClO2 as legally allowed in our drinking water shows no adverse effects on humans and animals. Here, the 100-fold concentration refers to a much higher limit value in the USA than, for example, in Germany, since there are often not so many treatment stages provided.
Note: The dose concentrations of the most commonly used oral intake protocol, MMS-1000 or CDS-1000, are generally well below these tested and declared safe levels.
Wikipedia on the toxicity of chlorine dioxide solutions
Higher organisms are relatively insensitive to chlorine dioxide ingestion by ingestion.
. For example, in a study on humans at the no negative changes were observed in ten healthy men after a single ingestion of 24 mg chlorine dioxide in one litre or 2.5 mg chlorite in 500 ml of water. This is a factor of ten or one hundred higher than the maximum values for drinking water treatment in Germany of 0.2 mg per litre of drinking water.” (Source: Link and Archive, as of June 8, 2014).