Editor’s Note:

Thursday, OPB aired the following story about fluoride science.  The story misstated where the American Cancer Society stands on water fluoridation. According to a Cancer Society spokesperson, the group has taken no position on water fluoridation. OPB regrets the error. 

The story also contained information about a study that summarized the findings of 27 studies on intelligence tests of fluoride-exposed children. OPB quoted a faculty member from the Harvard School of Dental Medicine about the study. The study’s authors were unavailable for comment when OPB first researched the story. Now, the study’s authors, with the Harvard School of Public Health, say that faculty member made a statement based on incorrect information about the study. 

Here’s what the authors say about their research:

Twenty-five of the studies were carried out in China. Fluoride released into the ground water in China in some cases greatly exceeded levels that are typical in the U.S. In general, complete information was not available on all 27 studies, and the researchers identified some limitations. 

On average, the study found that children with higher fluoride exposure showed poorer performance on IQ tests. The average loss in IQ was reported as a standardized weighted mean difference of 0.45, which would be approximately equivalent to seven IQ points.

The researchers conclude that these results do not allow them to make any judgment regarding possible risk at levels of exposure typical for water fluoridation in the U.S. On the other hand, they say, neither can it be concluded that no risk is present. They therefore recommend further research.

The Fluoride Debate: A Closer Look At The Science

In the middle of the 20th century, researchers learned high levels of naturally occurring fluoride in towns like Colorado Springs were causing children’s teeth to grow in brown and mottled.

They also noticed their teeth were surprisingly resistant to decay.

So in 1945, Grand Rapids, Michigan, agreed to add small amounts of fluoride to its water. A study found the rate of cavities among children there dropped 60 percent — and the U.S. Surgeon General has supported fluoridation since the 1950s. So, the debate has been running for decades.

One of the latest studies to raise hackles came out of Harvard University, last year. Researchers dug through dozens of previous studies and concluded that there is “the possibility of an adverse effect of high fluoride exposure on children’s neurodevelopment.”

Kim Kaminski: “We’re seeing negative health effects at very low levels of fluoride.”

Kim Kaminiski is fight[ing] to stop fluoridation with Clean Water Portland.

Kim Kaminski: “I mean we can talk all day about parts per million, but the bottom line is, when we start putting it in our drinking water, that’s the major exposure that most people have.”

Repeated calls and emails last fall to the study’s U.S. author, Anna Choi of the Harvard School of Public Health, were not returned. But Dr. Myron Allukian of the Harvard School of Dental Medicine said the study was flawed.

Myron Allukian: “What they did was they looked at 27 Chinese studies, they said they’re poorly done studies, and they say but when we put them all together in high fluoride areas, as much as 10 times what it is here in the United States, we get a half point difference in IQ.”

That’s not enough to indicate a problem, said Allukian.

Myron Allukian:  “A half-point difference in IQ is meaningless. That’s like saying, we measured all the people in New York and Chicago, and in New York they were a half-millimeter taller.”

But perhaps the most controversial fluoride study came out in 2006.  It found that, “For males less than 20 years old, fluoride levels in drinking water during growth, is associated with an increased risk of osteosarcoma.”

Osteosarcoma is a bone cancer.

Kaminiski of Clean Water Portland says the 2006 study prompted her to start digging into the whole fluoride issue.

Kim Kaminski: “This was peer-reviewed and published. It was a very solid study. And at the time, being a mom it was very concerning to me.”

Dr. Catherine Hayes of Health Resources in Action was an advisor for the 2006 study. She said that while it was peer reviewed, it was exploratory.

Catherine Hayes: “And it was done using a data set that was not as… involved in terms of the questions and they didn’t have any bone samples from cases or controls.”

Still, the study raised enough eyebrows that a follow-up was done.

Hayes was a co-author on that follow-up. She’s now a professor at Tufts University’s School of Dental Medicine.

She says that instead of just gathering information about previous cases of osteosarcoma, researchers looked at actual samples of bone from people who had the cancer.

Catherine Hayes: “In that study, the bone was carefully examined amongst individuals who had the osteosarcoma and those that did not. And there was no difference in the amount of fluoride in the bone. And that’s really significant, because now we’re not estimating fluoride intake, we’re really measuring it.”

So as far as Hayes is concerned, it means there’s no link between osteosarcoma and fluoride.

But fluoride opponents like Kaminiski aren’t buying it. They say the study’s other co-author, Chester Douglass, received payments from the toothpaste company Colgate-Palmolive.

Hayes said the allegations against Douglass don’t hold water.

Catherine Hayes:  “He was thoroughly investigated by Harvard University, a very extensive investigation and found completely innocent of any wrong doing.  His involvement with Colgate is as someone who provides educational information to them. And there is absolutely no relationship between his consulting work with Colgate and his research.”

Suffice it to say, whether you’re talking to scientists, activists or health policy experts, it’s easy to get bogged down in the details.

The list of organizations that endorse water fluoridation is long and authoritative — the American Medical Association, the National Institutes of Health and the American Cancer Society.  But Portland’s anti-fluoride campaign has attracted some big names too —  the local chapter of the Sierra Club, a scientist from the National Academy of Sciences Fluoride Committee, and consumer advocate Ralph Nader.

Even the local chapter of the NAACP came out against it.

Committee chair Clifford Walker says for him, it comes down to who you can trust.

Clifford Walker: “You hear the arguments on both sides, but you become suspect of governments telling you it’s okay.”

For example Walker says infants fed formula mixed with fluoridated water risk being over exposed. He cites the American Dental Association and the Centers for Disease Control.

The CDC’s website does say mixing infant formula with fluoridated water on a regular basis may increase the chance of a child developing mild enamel fluorosis — that is faint white markings on teeth.

But the American Dental Association says mild fluorosis doesn’t affect the health of a child or its teeth.

And besides the agencies say, parents can use purified bottled water to lessen the possibility.

But Walker says that’s a problem.

Clifford Walker: “A lot of times the income challenged people are not using the distilled or purified water, but they’re mixing it from tap water.”

The American Academy of Pediatrics website says that once a child’s adult teeth come in — around 8-years-of-age — the risk of developing fluorosis is over.