The first meta-analysis of water fluoridation studies – The York Review – was conducted in 2002 and found that the data on efficacy was limited and of low quality. [1]
A point to be considered here is that the institutionalised belief in water fluoridation for the half-century which preceded the York Review was apparently not grounded in much solid scientific enquiry, if any.
This review was conducted 3 years after the CDC published "Ten Great Public Health Achievements in the 20th Century", which included water fluoridation as one of these great achievements.
Another curiosity of this public health belief was the guideline that water fluoridation levels need to vary in a region based on temperature. This was because it is apparently a predictor of water consumption amounts by small children.
Colder climates were meant to have higher levels of fluoride (up to 1.2 ppm) because people apparently drink less water, and warmer climates were meant to have lower levels (0.7 ppm), because they drink more water.
It indicates that consumption is a very important factor in considering additive levels, and that all other factors are less important than climate.
This was codified in a 1957 paper "Determining optimum fluoride concentrations" (Galagan and Vermillion) [2] which includes their scientific formula:
parts per million of fluoride = 0.34 / E
"Where E is the estimated average daily water intake for children through 10 years of age in ounces per pound of body weight. It may be calculated from the estimation equation E=-0.038+0.0062 temperature, where temperature is the mean maximum temperature in degrees Fahrenheit."
This seems to reflect the kind of scientific rigour behind this belief, and perhaps the absurdity of the formula is why the US DHHS updated their guidelines in 2015 to settle on a flat 0.7 ppm regardless of climate [3].
A point to be considered here is that the institutionalised belief in water fluoridation for the half-century which preceded the York Review was apparently not grounded in much solid scientific enquiry, if any.
This review was conducted 3 years after the CDC published "Ten Great Public Health Achievements in the 20th Century", which included water fluoridation as one of these great achievements.
Another curiosity of this public health belief was the guideline that water fluoridation levels need to vary in a region based on temperature. This was because it is apparently a predictor of water consumption amounts by small children.
Colder climates were meant to have higher levels of fluoride (up to 1.2 ppm) because people apparently drink less water, and warmer climates were meant to have lower levels (0.7 ppm), because they drink more water.
It indicates that consumption is a very important factor in considering additive levels, and that all other factors are less important than climate.
This was codified in a 1957 paper "Determining optimum fluoride concentrations" (Galagan and Vermillion) [2] which includes their scientific formula:
parts per million of fluoride = 0.34 / E
"Where E is the estimated average daily water intake for children through 10 years of age in ounces per pound of body weight. It may be calculated from the estimation equation E=-0.038+0.0062 temperature, where temperature is the mean maximum temperature in degrees Fahrenheit."
This seems to reflect the kind of scientific rigour behind this belief, and perhaps the absurdity of the formula is why the US DHHS updated their guidelines in 2015 to settle on a flat 0.7 ppm regardless of climate [3].
[1] https://www.nature.com/articles/4801410
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2031310/?page=1
[3] https://www.federalregister.gov/documents/2015/05/01/2015-10...