A School of Dental Medicine professor cleared last month of allegations that he covered up links between fluoride and bone cancer is listed as a million-dollar benefactor of the school’s new research and education building.

The revelation has led one environmental advocacy group to suggest that a recent Harvard investigation of the professor, Chester W. Douglass, may have been compromised due to the professor’s status as a patron of the school.

The Washington-based Environmental Working Group, which initially brought the accusations against Douglass, said on Friday that the professor’s donation discredits the impartiality of Harvard’s review.

“There is nothing wrong with donating a million dollars to your employer, but it does create a potentially serious conflict of interest when the recipient of the million dollars is investigating the ethics of the donor,” the group’s senior vice-president, Richard Wiles, said in a statement.

Douglass did not respond to repeated requests for comment at his home and office. Likewise, officials at the School of Dental Medicine and Harvard Medical School did not respond to e-mails and phone calls over the weekend.

The Environmental Working Group alleged in 2005 that Douglass had suppressed the research of one of his students, Elise Bassin. Her research found an increased risk for osteosarcoma, a form of bone cancer, in young boys drinking fluoridated water. Douglass’s own studies found no connection between fluoride consumption and an increased likelihood of the cancer.

While the panel of senior Harvard professors conducting the investigation did not take a position on the cancer link, they stated that Douglass “did not intentionally omit, misrepresent, or suppress” Bassin’s findings.

Douglass also serves as the editor of a journal produced by fluoridated-toothpaste maker Colgate.

But the Harvard investigators reported that Douglass’s involvement with Colgate did not violate federal guidelines. In addition, the investigators said, the U.S. Department of Health and Human Service’s Office for Research Integrity oversaw Harvard’s review of Douglass and determined that no further investigation would be necessary.

The documents related to Harvard’s investigation have not been released.

In both the 2004 and 2005 fiscal years, Douglass gave between $1,867 and $2,499 to the School of Dental Medicine, according to annual reports posted on the school’s website.

The reports do not mention Douglass’s million-dollar gift to the school, but his name is emblazoned on a plaque in the lobby of the new 60,000-square-foot research and education building at 190 Avenue in Boston. On the plaque Douglass and his wife, Joy, are listed as one of six benefactors giving $1 million or more to the school.

—Staff writer Javier C. Hernandez can be reached at jhernand@fas.harvard.edu.