EDITED (to show specific part from discussion and to add link from whence it came)
http://optimox.com/pics/Iodine/IOD-05/IOD_05.html
For example, dis[in]ffection of water for human consumption and in swimming pools is far superior, safer, and less expensive with the use of Iodine at 1 to 2 ppm, that with the use of chlorine and its derivatives at the same concentrations.16-19 However, unfounded concern about the adverse effects of Iodine at these levels on the thyroid gland,20-22 and vide infra has prevented the widespread use of Iodine for these applications, with toxic chlorine and its derivatives used by default. All studies published so far favor iodine over chlorine for treatment of municipal waters and swimming pools, "Because of the increasing difficulty experienced by many communities in achieving satisfactory disinfection of public water supplies with acceptable concentrations of chlorine, a feasibility study on the use of iodine for this purpose was undertaken."19 "The effectiveness, ease of administration and palatability were prime reasons for considering iodine as a disinfectant of community water supplies... effective bacteriological control of the water was maintained by all concentrations of iodine used in this study."17 "At an iodine concentration of 1 mg/liter ( 1 ppm), the water met all standards for safety and palatability (1962 USPHS Drinking Water Standards)... During the five years in which this study was conducted no instances of urticaria or iodism were observed."19 "No evidence of iodine induced allergic phenomena was detected during this study."17 "Comparative data indicate that disinfection of an Olympic-size swimming pool can be accomplished with iodine at half the dose of chlorination... Use of the iodinated swimming pool caused no significant changes in either the RAI uptakes or PBI concentrations."19 The advantage of iodine over chlorine as a disinfectant in the treatment of municipal waters is that it could be used as a disinfectant and also as a source of a very important essential element. It is obvious that the benefits of such an approach would outweigh the risks, based on the studies mentioned above.

When different groups of competitive swimmers were asked about their preference between chlorine and iodine as a disinfectant of swimming pools,19 they overwhelmingly chose iodine. None preferred chlorine. "All members of the swimming teams of five universities who participated in AAWU swimming championships that were held in the Stanford pools were asked to express their opinions of iodine-treated water as compared with chlorine-treated water... Seventeen of the 20 freshmen and varsity swimming members expressed a preference for the iodine-treated pool in respect to eye irritation. The other three had no preference, but none preferred the chlorine treatment. Of the championship-swimming contestants, 48 preferred the iodine-treated pool, five had no preference, but none preferred the chlorine-treated pool... Twenty-eight of the subjects who had been exposed to the iodine-treated water for one month were examined by the three physicians of the research staff, each of whom made his observations independently of the others. Twenty-seven of the swimmers examined received a completely negative rating for eye irritation. In only one student was a mild conjunctivitis found on medical examination. This student wears contact lenses and stated that his eye irritation had improved in a miraculous way since the pool had been treated with iodine."