See? (Thanks, xkcd!)
As for the community in the Denver study, over the past few decades the use of electrical appliances in their homes has actually increased while Leukemia rates have dropped. However, deaths from child neglect, gunshots, and stabbings have also increased in low income communities, so really cancer just passed the buck on this one.
Let's face it: any time you start putting shit in people's water supply, they're going to complain. You could put forward a program to dribble in a little Cristal at the water treatment plant just to class things up, and you'd get protestors the next day.
So for the past century, many people have been convinced that the plan to dilute fluoride into water supplies is evil somehow, everything from granting the government mind control powers to disposing of toxic waste. Every time a country talks about adding fluoride to its water, alarmists bombard the public with propaganda against it.
Knowing is half the planet -- or whatever. Ah fuck it.
So in 1990, when the US National Toxicology Program (NTP) did a study on the effects of fluoridated water on laboratory rats (evidently rats were responsible for some grievous atrocity back on the planet Scientistune and revenge is being exacted in our world) and found that there was evidence of a higher rate of bone cancer, it loosened the bowels of everyone in the anti-fluoride movement.
The whispers of conspiracy intensified when it was alleged that a scientist working for Colgate had possibly tampered with the results of a major study in 2006 that demonstrated a link between fluoridated water and the appearance of bone cancer in boys, which is way more nefarious than any of us ever expected toothpaste to be.
Why It's Bullshit
His eyes are closed because he's dead.
More than 50 different studies have attempted to prove a link between fluoridated water and cancer since that 1990 study, and found what all of the studies prior to that also found, which is that there's no evidence of a link between fluoridated water and cancer.
Like the power line thing, what makes it difficult is that there are infinite other possible causes for cancer so rates go up and down on their own. You may find one community where rates went up, only to find that they were also, say, drinking coolant spilled from nuclear submarines. But as a whole they could find no increase in cancer in communities that have fluoridated water verses the ones that don't.
Basically, the International Agency for Research on Cancer, United States Public Health Service, National Research Council, National Health Service, and the US Centers for Disease Control and Prevention have all agreed there that fluoride in your tap water won't give you cancer. Then again, if you believe in the conspiracy, those are exactly the type of people the conspirators would hire to reassure you.
So they can control your mind.
Read more from Joe at For Us.. By Other People.