While it has long been believed that fluoride has a half life of 3.5 hours (time to clear it from the body), experience of victims of fluoride poisoning suggests that the chemical's half life is much longer. When a community in Alaska was poisoned with fluoride due to a malfunction of the fluoridation equipment system, researchers noted that blood fluoride levels did not return to normal within 24 hours as would be expected. Nineteen days after the poisoning, mean blood levels of fluoride were 0.092 mg/L nearly three times the levels in the few non poisoned individuals residing in the same community (Fluoride, 1994; 27: 32-6).
Studies now show that, far from clearing quickly from the body, fluoride accumulates over time, reaching toxic levels as a person ages. Fluoride has a particular affinity for bones and has been widely linked to the development of osteoporosis and a high rate of hip fractures (JAMA, 1992; 268: 746-8; JAMA, 1990; 264: 500-2; JAMA, 1991; 266: 513). Accumulation of fluoride, which begins in infancy, can reach the lower levels of toxicity needed to produce bone damage after only 38 years. In fluoridated communities where the level of fluoride in the water is 4 ppm (the maximum allowable in water and far below that of toothpaste), many people will reach mid to high dose accumulation by this age.As a general rule, approximately half of each day's fluoride intake is retained. Healthy kidneys can eliminate only about 50 per cent of daily fluoride intake. The rest gets absorbed into calcified tissues such as bones and teeth as well as some organs. And remember: you get fluoride from other sources like food. To our horror, we discovered that even meal replacements, such as Fortisip by Nutricia intended for ill patients, contain 0.15 mg of sodium fluoride per 100 ml.