It's amazing how people don't even bother to read the studies that they claim as evidence backing up their claims.
Firstly, as the brief at the top said, the studies used varying amounts of fluoride from 0.88 – 9.4 ppm. A litre of water is roughly 1,000,000 mg, so the conversion between ppm of fluoride and mg/litre just involves changing the symbol. As I've already said, the recommended amount of fluoride in water is 0.5-1.0 mg/l (or ppm in this case).
So the tests that use higher concentrations of fluoride are not representative samples of drinking water that has been fluoridated, and in fact the studies say this. They are listed as "studies reporting an association of high fluoride exposure and reduced IQ".
If you look at the table of results, the studies all involve comparing small levels of fluoride intake with high levels. The conclusions of the studies are that high levels of fluoride intake are dangerous and can lower IQs. For instance, one study compared 2.01 ppm to 5.55 ppm and found "...the mean IQ level of students exposed to high F drinking water was significantly lower than that of the students to a lower F level drinking water".
Other studies demonstrate no additional information that isn't already used, such as this one: "drinking water fluoride levels greater than 1.0 mg/L may adversely affect the development of children’s intelligence".
Ironically, one study showed that too little fluoride resulted in a lower IQ as well. "A child whose drinking water is above 2.0 mg/L or below 0.2 mg/L manifest intellectual deficits as compared to ‘normal’ control group."
Firstly, as the brief at the top said, the studies used varying amounts of fluoride from 0.88 – 9.4 ppm. A litre of water is roughly 1,000,000 mg, so the conversion between ppm of fluoride and mg/litre just involves changing the symbol. As I've already said, the recommended amount of fluoride in water is 0.5-1.0 mg/l (or ppm in this case).
So the tests that use higher concentrations of fluoride are not representative samples of drinking water that has been fluoridated, and in fact the studies say this. They are listed as "studies reporting an association of high fluoride exposure and reduced IQ".
If you look at the table of results, the studies all involve comparing small levels of fluoride intake with high levels. The conclusions of the studies are that high levels of fluoride intake are dangerous and can lower IQs. For instance, one study compared 2.01 ppm to 5.55 ppm and found "...the mean IQ level of students exposed to high F drinking water was significantly lower than that of the students to a lower F level drinking water".
Other studies demonstrate no additional information that isn't already used, such as this one: "drinking water fluoride levels greater than 1.0 mg/L may adversely affect the development of children’s intelligence".
Ironically, one study showed that too little fluoride resulted in a lower IQ as well. "A child whose drinking water is above 2.0 mg/L or below 0.2 mg/L manifest intellectual deficits as compared to ‘normal’ control group."
