"There are no known harmful effects from ingestion of water that has had fluoride added to it at or about 0.7-1.2 milligrams/liter. No systematic reviews of the literature have shown any negative health effects from ingestion of water fluoridated in or near this therapeutic range."Connett says, This assertion is dangerously misleading because it: a) Confuses the difference between concentration and dose. Harm has been found at doses that are commonly experienced in populations drinking artificially fluoridated water. For example, a child drinking 2 liters of water at 1 ppm (the average level used in fluoridation) will get a higher dose than a child drinking one liter of water at 1.9 ppm, the threshold for lowering of IQ in one published study. b) Ignores that most basic health studies have not been conducted in countries practicing fluoridation. The absence of study is not the same as absence of harm.