Exposure to excessive fluoride during hemodialysis.

The safety of fluoridated community water supplies for dialysate and long-term intermittent hemodialysis has been questioned since 1965 [1]. The only significant means of clearing fluoride from body fluids are renal excretion and incorporation into bone [2]. When dialysate is prepared with fluoridated water, fluoride ion moves along a concentration gradient from dialysate to blood [3, 4]. Because renal excretion is defective or absent in such patients, the fluoride administered during dialysis is incorporated into the skeleton. Under these conditions, serum fluoride concentrations increase progressively, and the bone content of fluoride rises above values obtained in persons with normal renal function who drink water that is fluoridated [3—6] (the serum fluoride concentration in normal persons who drink water with a fluoride concentration of 53 LM [1 ppm] is 0.7 0.4 LM [mean SD]). Although it has not been established that fluoridated dialysate adversely affects the bone of patients maintained by hemodialysis, this possibility exists, particularly in patients who have been exposed to such a dialysate for many years. This and other problems associated with various substances in tap water have made deionization of water used for dialysate a common practice. Unfortunately, if the deionizer is improperly maintained, the fluoride content of the water may actually increase as the deionizer becomes exhausted. Methods and Results. To determine whether the excessive use of a deionizer could result in elution of retained fluoride, polystyrene tubing (224 mm long, 8 mm I.D.) was filled with resin taken from an ion exchanger (Illgo-Way) supplied by the illinois Water Treatment Company, Rochester, Illinois. Tap water