Safety of Iodine as a Disinfectant in Swimming Pools

to meet a request of the Cali¬ fornia State Department of Public Health for an evaluation of the effects of swimming in pools in which iodine is used as a disinfectant.The study was designed to ascertain if (a) blood iodine changes could be expected because of the possibility of the inhalation, ingestion, or absorption of iodine; (b) there would be signifi¬ cant evidence in the urine of any inhalation, in- gestion, or absorption of iodine; (c) eye inflam¬ mation might be expected to be associated with swimming in iodine-treated waters, and (d) iodine is effective as a disinfectant for swim¬ ming pools.Three outdoor swimming pools at the men's gymnasium of Stanford University were used in this study.These pools consist of a racing pool of 135,000 gallons capacity, a class-instruc¬ tion pool of 60,000 gallons capacity, and a div¬ ing pool of 190,000 gallons capacity.The pools were constructed in 1929 and have been in con¬ tinuous operation since that time.The filter system for these pools consists of two cylindrical horizontal sand filters, 14 feet long and 8 feet in diameter.The sand level is from 4 feet to 7 feet in depth, making a surface All four authors are members of the faculty of Stan¬ ford University, Stanford,