Effect of Iodinated Water Supplies on Thyroid Function

Iodine, long recognized as an effective agent for providing potable water, was used as the means of disinfecting the water supply of an entire prison community. The general health and thyroid function of representative inmates were assayed before and during usage of iodinated water for 9 months. Water containing 1 mg of iodine/I induced a marked decrease in RAI uptake, but PBI values of test subjects changed relatively little until the iodide concentration was increased to 5 mg/l. However, serum thyroxine concentrations remained unchanged irrespective of the amount of iodine in the water. No evidence of hypersensitivity or other adverse effects of iodine were detected during this study. At a concentration of iodine (1 mg/l) adequate to provide bacteriological control of the water, only 2 of 15 inmates tested had impaired “organification” of thyroidal iodide. Ancillary studies on nonprison personnel indicated that swimming in iodinated water (5 mg iodide/l) induced no change in any of the parameters of thyroid function. Increasing use of iodine in public swimming pools constitutes a source of iodine of which physicians should be aware. The present study demonstrates the long-term tolerance of individuals to an iodinated water supply, and it may be that this relatively simple means of water disinfection will have wide usage in underdeveloped countries.