Some of the specialists I have discussed this with are docs as well as being specialists in water treatment. Your assumption is not correct. Chlorine and chlorinated compounds are the most widely used disinfectant in municipal water systems the world over. Iodine based water disinfection has been used globally for water disinfection for decades. There is tons of information on this topic on the Web or at your local library and most of the authoritative wilderness medical texts also cover the subject.