Three of five city commissioners have said they're in favor of adding fluoride to Portland city water. The Centers for Disease Control and Prevention says fluoride is a safe and healthy way to effectively prevent tooth decay. But opposition is vocal and intense.
There are two fluoride studies that opponents often raise at public hearings, like the one scheduled for Portland City Council Thursday afternoon.
The list of organizations that endorse fluoridation is long and authoratative. Think: the American Medical Association, Kaiser Permanente, the National Institutes of Health and the American Cancer Society.
But there are a number of scientific, medical and environmental professionals who raise questions about possible risks.
Kim Kaminiski of Clean Water Portland says that fluoridation is a conspiracy.
"These are byproducts of the phosphate fertilizer industry. We're talking about sodium fluoride, we're talking about sodium fluorosilicate … And they are put into our drinking water. We cannot dump them in the ocean, we cannot dump them in the river. We cannot put them into a landfill. The phosphate fertilizer industry would have to pay very high costs to dispose of them in a toxic waste facility," says Kaminiski.
But fluoride occurs naturally. And as with any compound, it's the dose that's important.
For example, one ibuprofen pill can relieve pain, a massive overdose can cause cardiac arrest.
As far as being a byproduct of the fertilizer industry, Kylie Menagh-Johson of the Everyone Deserves Healthy Teeth Coalition says a fluoride ion is a fluoride ion, no matter where it comes from.
"The standards that are used in this country to monitor the drinking water are very high and ensure that there are no contaminants," says Menagh-Johson.
But perhaps dueling spokeswomen aren't going to make this debate much clearer.
Instead, let's consider the science.
In the middle of the 20th century, researchers learned that 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 that these kids' teeth were surprisingly resistant to decay.
So in 1945, Grand Rapids, Michigan, agreed to an experiment by adding small amounts of fluoride to its water. An 11-year study by the U.S. Surgeon General found the rate of cavities among children there dropped 60 percent.
The controversy has lasted ever since.
The latest study to raise hackles just came out of Harvard. It went through information from 27 previous studies and concluded that there is "…the possibility of an adverse effect of high fluoride exposure on children’s neurodevelopment."
Kim Kaminiski of Clean Water Portland says she believes fluoride affects children's IQ levels.
"We're seeing negative health effects at very low levels of fluoride. 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," says Kaminiski.
Repeated calls and emails to the study's U.S. author, Anna Choi of the Harvard School of Public Health, were not returned. But the study did conclude that more research was needed.
Doctor Myron Allukian of the Harvard School of Dental Medicine says the study had other problems too.
"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," says Allukian. "Well, 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."
Mayor Sam Adams, who supports fluoridation, points out in a letter to residents that Portland would fluoridate water at 0.7 parts per million, while the studies done in China looked at fluoride exposure up to 11.5 parts per million.
Allukian says he's planning to ask the authors to distribute a letter saying the study should not be linked with fluoridation levels in this country.
Perhaps the most controversial fluoride study to hit the news also came out of Harvard, but in 2006. The study 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 that's what prompted her to start looking into fluoride."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," says Kaminiski.
Dr. Catherine Hayes of Health Resources in Action was an advisor for the 2006 study. She was an associate professor at the Harvard School of Dental Medicine at the time. She says that while it was peer reviewed, it was exploratory.
"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."
But that study did raise enough eyebrows to warrant a follow-up.
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, they looked at actual samples of bone from people who had the cancer.
"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," says Hayes.
So as far as Hayes is concerned, it means there's no link between osteocarsoma and fluoride.
But anti-fluoride activists like Kaminiski remain unconvinced. They say the study's co-author, Chester Douglass, received payments from the toothpaste company Colgate.
Hayes says that shouldn't make any difference.
"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," says Hayes.
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.
In his letter explaining why he supports fluoridation, Mayor Adams says there have been more than 3,000 studies on fluoridation, and the majority found it to be safe and effective.
Barbara Gooch of the CDC says there's a good reason the federal agency is pushing fluoridation: "Because it reduces tooth decay by about 25 percent in children and adults."
About one third of Oregonians' drinking water is fluoridated, compared to about two thirds in Washington. The Oregon Health Authority says the rate of untreated tooth decay among Oregon's children is double that of Washington.