There is a 1982/1984 WHO (World Health Organization) study of oral ingestion of an aqueous chlorine dioxide solution in 10 men with various ingestion protocols and doses over 12 weeks. This included blood pressure, breath rate, pulse, mouth temperature, and EEG, as well as extensive blood and urine analyses were performed.
Result: No significant side effects were measured.
Note: The duration of Jim Humble’s most used Application Protocol 1000 is 4 weeks, only 1/3rd of the period tested!
(Source: Link and Archive and publication in Enviromental Health Perspectives Vol.46, 1982)