Boys who drink fluoridated water have an increased risk of a deadly bone cancer, a new study suggests.
Elise Bassin, DDS, completed the study in 2001 for her doctoral dissertation at Harvard, where she now is clinical instructor in oral health policy and epidemiology. The study finally was published in the May issue of Cancer Causes and Control.
Bassin and colleagues' major finding: Boys who grew up in communities that added at least moderate levels of fluoride to their water got bone cancer -- osteosarcoma -- more often than boys who drank water with little or no fluoride.
The risk peaked for boys who drank more highly fluoridated water between the ages of 6 and 8 years -- a time at which children undergo a major growth spurt. By the time they were 20, these boys got bone cancer 5.46 times more often than boys with the lowest consumption. No effect was seen for girls.
In a prepared statement provided to WebMD, Bassin says she "was surprised by the results."
"Having a background in dentistry and dental public health, [I] was taught that fluoride at recommended levels is safe and effective for the prevention of dental [cavities]," Bassin says in the statement. "All of [our analyses] were consistent in finding an association between fluoride levels in drinking water and an increased risk of osteosarcoma for males diagnosed before age 20, but not consistently for girls."
It's not surprising that Bassin found a risk for boys but not for girls. Osteosarcoma is about 50% more common in males than in females. And boys tend to have more fluoride in their bones than girls.
Caution About Study
However, a commentary accompanying Bassin's article warns to take her findings with a grain of salt. Ironically, it is from Harvard professor Chester W. Douglass, DMD, PhD. Douglass led Bassin's PhD committee, which approved of the study when it was presented as her doctoral dissertation.
Douglass warns that the Bassin study is based only on a subset of people exposed to fluoridated water. Preliminary results from the entire population of exposed individuals, Douglass writes, show no link between bone cancer and water fluoridation.
But Bassin specifically looked at the subgroup of people most likely to be affected by fluoridation: children. She limited her analysis to people who got bone cancer by age 20. That's because most cases of osteosarcoma occur either during the teen years or after middle age.
Fluoride collects in the bones. And it's particularly likely to accumulate in the bones during periods of rapid bone growth. So Bassin looked at fluoride exposures during childhood for 103 under-20 osteosarcoma patients and compared them with 215 matched people without bone cancer. Her study took into account how much fluoride was in the water in the communities where children actually lived and the history of municipal, well water, or bottled water use.
The Environmental Working Group, a nonprofit watchdog organization, says water fluoridation should stop until further research can refute or confirm Bassin's findings. Tim Kropp, PhD, is a senior scientist at EWG.
"About 65 percent of the U.S. water supply has added fluoride," Kropp tells WebMD. "With evidence this strong, it only makes sense to act on it. Right now, it makes the most sense to put fluoride in toothpaste, and not into our water. It's not like this is a huge contaminant that will cost billions of dollars to fix. We can just stop adding it to our water it if we want to."
According to the American Cancer Society, every year some 900 Americans -- 400 of them children and teens -- get osteosarcoma.
By Daniel J. DeNoon, reviewed by Louise Chang, MD
SOURCES: Bassin, E.B. Cancer Causes and Control, May 2006; vol 17: pp 421-428. Douglass, C.W. and Joshipura, K. Cancer Causes and Control, May 2006; vol 17: pp 481-482. Elise Bassin, DDS, prepared statement, provided by the Harvard University press office. Tim Kropp, PhD, senior scientist, Environmental Working Group, Washington, D.C.