Chester Douglass, who heads Harvard's Department of Oral Health Policy and Epidemiology, received a $1.3 million grant in 1992 from the National Institute of Environmental Health Sciences to conduct a study of fluoride exposure and osteosarcoma, a rare form of bone cancer.

Douglass' 1992-1999 study found that the odds of having osteosarcoma after drinking fluoridated water were "not statistically different" from those who drank non-fluoridated water.

But Elise Bassin, a doctoral student who Douglass supervised, reported in her 2001 thesis that boys who drink fluoridated water appear to have an increased risk of developing the bone cancer. Her findings were based on some of the same people used in Douglass' study.

The Environmental Working Group, an advocacy group based in Washington, D.C., filed an ethics complaint against Douglass last month after discovering that Douglass cited Bassin's research in his final grant report. In it, he said her work supported his claim that there was no significant risk from fluoridated water, even though Bassin had found a strong link between fluoride levels in tap water and an increased osteosarcoma risk for boys.

Richard Wiles, senior vice president of the environmental group, also said there is a conflict of interest between Douglass' research and his position as editor-in-chief of The Colgate Oral Health Report, a quarterly newsletter funded by Colgate-Palmolive Co., which makes fluoridated toothpaste.

"It's safe to say that he appears to be one of the leading members of the fluoride apologists group of scientists," Wiles said. "Clearly, the fluoride-using industry, the dental industry, has an interest in the image of fluoride as being a healthy, good thing."

A woman who answered the phone on Wednesday at Douglass' office said he was on vacation and unavailable for comment.

Harvard Medical School spokesman John Lacey said the school will work with the National Institute of Environmental Health Sciences to review Douglass' research.

"The Harvard School of Dental Medicine takes all allegations of misconduct seriously and has a standard system for reviewing allegations of research impropriety. The school is assembling an inquiry committee to review the questions raised concerning the reporting of this work," the school said in a statement.

Christine Bruske, a spokeswoman for NIEHS, said the institute is reviewing the letter it received from the Environmental Working Group alleging "scientific misconduct" by Douglass.

Bassin declined to comment when reached at her home Wednesday.

Her thesis has not yet been published and is not available to the public. The environmental group, which obtained Bassin's thesis, cited excerpts in a letter to sent to Douglass last month.

"Among males, exposure to fluoride at or above the target level was associated with an increased risk of developing osteosarcoma," Bassin wrote. "The association was most apparent between ages 5-10 with a peak at 6 to 8 years of age."

Douglass' study looked at men and woman of all different ages who drank fluoridated tap water. Bassin looked at the boys and girls used in Douglass' study and verified fluoride levels in tap water for each year of the child's life.

"She found the strongest association ever between fluoridated tape water and bone cancer among boys," said Wiles.

Fluoridation of tap water in the United States began in the 1950s and was seen as an effective way to fight tooth decay.

Controversy over the practice began to grow in the 1970s after a study found a high incident in bone structure defects in Newburgh, N.Y., one of the first communities in the country to fluoridate its water, when compared with the rate in the non-fluoridated town of Kingston, N.Y.

A study completed in 1991 by the U.S. Public Health Service found that the rates of osteosarcoma were significantly higher among males under 20 who lived in fluoridated communities than in communities with non-fluoridated water.

Several other major studies have reached the opposite conclusion, including a 1995 study by the New York State Department of Health that found fluoride exposure does not increase the risk for childhood osteosarcoma.

Wiles said the Environmental Working Group is not opposed to fluoridated toothpaste because most of the fluoride in toothpaste has contact with the teeth and is not ingested. He said when fluoride is ingested through tap water, it can stimulate growth at the end of bones, where osteosarcoma occurs.

"I think the industry realizes that the public may not make the distinction," Wiles said. If fluoride gets a big black eye in tap water then the public is going to wonder about this fluoride in my toothpaste."