GRAND RAPIDS, Mich.—The great American assault on tooth decay began here 63 years ago, earning Grand Rapids a special place in the annals of dental history: the first city in the world to fluoridate its public water system.

So it is more than a little head-scratching that fluoride, the chemical widely credited with dramatically cutting cavities and promoting oral hygiene, is having its scientific credentials questioned in the city that literally swallowed it first.

The belated questioning of fluoride in the most unlikely of places stems partly from unsettled questions—some new, some old—about possible links to cancer and thyroid and kidney problems if too much fluoride is ingested. But the push here mirrors a spreading nationwide awareness and re-examination of the health impact of a wide variety of chemicals added to food, health-care products and water, as well as the use of pesticides.

Unusual findings

Local and state governments around the nation are taking a second — and in some cases a first — look at chemical practices and their potential impact. A county in Utah has stopped encouraging people to flush unused prescription drugs down the toilet because they might contaminate the water system. That action was taken after a report from the U.S. Geological Survey found chemicals from prescription drugs in streams and rivers.

A Tribune examination of Chicago’s drinking water this year found traces of pharmaceuticals and personal-care products.

In California, several communities are cracking down on aerial pesticide spraying because of its potential impact on humans and animals. Experts predict that in-depth examinations of chemicals formerly considered benign will become more frequent.

“I think this pattern has been growing because there is better environmental health research that draws connections between low levels of chemical exposure and changes in our bodies,” said Dr. Howard Hu, chairman of environmental health sciences at the University of Michigan.

“As the research has become more sophisticated, it shows that environmental toxicants can do other things beyond just kill you—they can stunt your growth, change behavior and increase the risk of cardiovascular disease,” Hu said.

‘On my radar screen’

Fluoride fights stretch back more than a half-century. Recent studies, though, suggest a possible link to thyroid trouble and problems for people on dialysis. The U.S. Centers for Disease Control and Prevention maintains that water fluoridation is a safe and cost-effective way to prevent tooth decay, but some scientists say questions about the long-term impact cannot be dismissed.

Recent studies, while not conclusive, convinced Corky Overmyer, the director of environmental sustainability for Grand Rapids, that a review was needed to study fluoride’s impact on the 11 communities served by the city’s water system.

“This has been on my radar screen for a while,” said Overmyer, who several years ago led the effort to remove chlorine from the city’s water. Overmyer insists he has drawn no conclusions about the safety of fluoride.

Grand Rapids commemorates the 1945 fluoridation with a 30-foot sculpture in the heart of downtown, and the questioning of fluoride has stirred controversy. Dentists have doubted or condemned the effort, and the Grand Rapids Press counseled caution in an editorial.

Grand Rapids, long known as a furniture-making city, is working to reinvent itself as a center of medical research. The timing of the fluoride examination is, at best, awkward because some of the most prominent groups in the medical establishment—the American Dental Association, the American Medical Association and the CDC—have endorsed fluoride.

“They tend to look at little bits of information that are taken out of context,” Dr. Howard Pollick, a dentist and chief spokesman for the ADA, said of fluoride opponents.

Overmyer said he is taking heat.

“I had no idea [fluoride] was that sensitive an issue,” he said, noting he has “teeth marks” in his backside from his dentist and the city’s mayor, who declined to return phone calls to discuss fluoride.

About two-thirds of Americans, including those in Chicago and most major metropolitan areas, are served by fluoridated water. Resistance to fluoride usually is localized, with battles occurring in small towns. In May, voters in two Massachusetts towns overwhelmingly rejected efforts to fluoridate the water.

The Internet has effectively re-energized the former ragtag group of activists by making new information—valid or not—instantly available.

And the re-examination by Grand Rapids, the mother of fluoride, has provided an unanticipated boost for opponents.

“If Grand Rapids falls, that could be the beginning of the end of fluoride,” said Paul Connett, a retired chemistry professor and director of the Fluoride Action Network, which advocates against fluoridation.

There is strong political and medical resistance to reversing the fluoride policy. Dr. Tim Gietzen, who has practiced dentistry in Grand Rapids for 30 years, said he can tell which of his patients grew up with fluoridated water just by looking in their mouths.

Gietzen said fluoride should remain in the water system “unless someone is causing problems.”

That’s the question to be pursued by Overmyer, who said, “I’m just trying to be honest and open, and I’ve become a lightning rod.”