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.
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But during a recent visit to the dentist, my hygienist 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 occurred 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 of Columbia.
While a vocal minority of Americans remain skeptical, the ADA and most other health authorities remain convinced that fluoridation benefits the general population.
D.C. 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 cavities in adolescents by between 8 percent and 37 percent, and among adults by 20 percent 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.
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."
Still, a South Australia study conducted between 1991 and 1995 showed that children who drank only rainwater and bottled water had a 52.7 percent higher rate of cavities in their baby teeth than those who drank only public, fluoridated tap water.
Not all filtered or bottled waters are totally devoid of fluoride: Brita filters do not strip it out of tap water, and some bottled brands such as Nursery Water advertise that they add the mineral. The ADA has introduced a certification program for foods and beverages that are beneficial to oral health, including fluoridated bottled water, in part to encourage bottlers to provide optimally fluoridated water.
But many filters, including the reverse osmosis filter my husband and I bought from Watts Premier to more popular ones sold at Costco and Sam's Club, do counteract public fluoridation. Parents might decide they need to add that fluoride back in, through fluoride toothpaste or fluoride supplements. And that leaves the increasingly confused parents in a quandary: How do you make sure your children are getting enough -- but not too much -- fluoride?
Excessive fluoride consumption can cause fluorosis, which manifests itself in discolored teeth. And many dentists warn that while children should get into the habit of brushing once they have several teeth, they shouldn't use fluoride toothpaste until they are mature enough to spit out after brushing, which happens between the ages of 2 and 3. Even the Environmental Protection Agency is reviewing the maximum amount of fluoride it will allow in drinking water.
"There's not as easy an answer as we would like," Levy said. "And there are no simple answers on the horizon."
Palian, for example, prescribed a daily liquid sodium fluoride supplement of 0.5 milliliters for my son to swallow each day. The ADA recommends this sort of supplement for children who face a high risk of tooth decay, either because of genetics or diet.
But Martha Ann Keels, the division chief of pediatric dentistry at Duke University, said neither tablet nor liquid supplements are as effective as fluoride toothpaste in helping your teeth resist the impact of acid they're exposed to during the day.
"The main benefit of fluoride is topical: You put it on the enamel to recharge it," Keels said. "It's like putting shoe polish on your shoe."
So Keels recommends that her patients take a risk assessment survey created by the American Pediatric Dentistry Association to determine whether either a supplement or early exposure to fluoride toothpaste makes sense.
And in most cases, she favors putting what she and Levy call a tiny "smear" of fluoride toothpaste on the brush if your child may be too young to spit it out. They describe the smear as one-quarter the size of a pea, or a grain of rice.
"Even if they ingested all of it, it would be such a tiny amount it would have very little impact," Levy said. He cautioned that parents need to supervise the brushing process to ensure that the toothpaste is being evenly distributed, and ideally some of it is being spit out. "You need to start positively with prevention, and make sure you're careful about it."
And a range of other factors can also affect the development of cavities among children. If they are drinking bottled water instead of carbonated, sugared drinks, Pollick said, "then there would be perhaps less risk for tooth decay." But some recent immigrants from Central America are actually substituting sodas for tap water because they are skeptical of U.S. water quality, Keels said, which has the reverse effect.
And while it may take a few years to sort of out the science, Keels said, she and her colleagues are determined to find a better answer to the kind of question families like mine are now trying to sort out: "There's a huge drive toward wanting to get it right."