Little did I know that filtering my family's tap water might put our teeth at risk.

Two years ago, when I was pregnant and reporting on how the federal government was unwilling to regulate the rocket-fuel component perchlorate in drinking water, my husband and I decided to install a reverse osmosis filter in our kitchen tap. Since D.C. tap water has come under fire for its high levels of everything from lead to hexavalent chromium, it seemed like a sensible move.

But during a recent visit to the dentist, my hygenist remarked she had started noticing a rise in tooth decay among children who drank only filtered or bottled water, presumably because they were not drinking fluoridated water. And it suddenly occured to me: Neither was my 20-month-old son, with his 17 teeth.

As Americans' consumption of bottled water has risen - it has doubled over the past decade - it is reducing the daily exposure Americans get to the mineral that helps prevent tooth decay. And while researchers have yet to do a comprehensive study of what impact this is having, especially on children, many dentists and pediatricians believe the issue deserves serious examination.

"I think it would be good to look at," said Howard Pollick, a clinical professor in the Department of Preventive and Restorative Dental Sciences at the University of California at San Francisco and a spokesman for the American Dental Association.

Prodded by studies showing that fluoride significantly reduced tooth decay, U.S. municipalities began adding it to public drinking water systems in the 1940s. Today, about 65 percent of Americans get fluoridated tap water, including 95 percent of people in Virginia, 99 percent in Maryland and 100 percent in the District.

While a vocal minority of Americans remain skeptical, the ADA and most other health authorities remain convinced that fluoridation benefits the general population.

District dentist Pierre Palian, who treats my family, told me that after utilities started fluoridating public water supplies, "the cavities rate was cut in half. The only thing they could attribute it to was fluoridating the water."

The Centers for Disease Control and Prevention identifies fluoridation of public drinking water as one of the top 10 public health achievements of the 20th century, noting that studies show it reduces cavitities in adolescents by between 8 and 37 percent, and among adults by 20 to 40 percent.

But when it comes to getting greater precision, researchers are faced with the problem that most people in the United States don't take their children to the dentist before age 3, and most drink water from a mix of sources. As a result, it's difficult to measure the impact of fluoride on children's teeth.

How much is too much?



Steven M. Levy, a professor in the preventive and community dentistry department at the University of Iowa's dental school, has been studying the fluoride intake of a group of young adults since birth.

"Those who had more bottled water had a slight tendency to have more decay in the baby teeth, but we had very small numbers," said Levy, whose study participants are now ages 15 to 18. "It wasn't a definitive study."