A nonprofit public interest group says a report that charts human health problems near Great Lakes toxic sites has been hidden by the U.S. government for seven months because the findings might be too controversial.

The Center for Public Integrity obtained the 400-page report conducted by the U.S. Centers for Disease Control and Prevention and released parts of the draft on Thursday.

The report found evidence of increased infant mortality and cancer rates near 25 of 26 toxic hot spots around the Great Lakes, the so-called "areas of concern" that are in various stages of cleanup.

The hot spots include polluted areas of the Duluth-Superior harbor and adjoining areas -- including the St. Louis River-Interlake Tar site (Stryker Bay) and the Koppers Co. plant site in Superior, Wis.

The report found that, compared to "peer counties" and the national average, 21 of the 26 areas had elevated infant mortality rates, 17 had elevated breast cancer mortality rates, 16 had elevated rates of colon cancer, 12 had elevated rates of lung cancer, six had elevated rates of low birth weights and four had elevated rates of premature births.

The implication is that exposure to toxic substances found at the 26 sites -- including PCBs, lead, pesticides, dioxin, mercury and others -- might have contributed to the health issues. But the report is clear that those higher rates of disease can't necessarily be linked to toxic exposure from the areas of concern.

The report remains unreleased in the Agency for Toxic Substances and Disease Registry, a division of the CDC. Three U.S. Congress members on Thursday demanded that top CDC officials respond to claims they have stifled the Great Lakes report and wrongly retaliated against agency staff members who wanted to release the data.

ATSDR officials did not respond to attempts to reach them for comment Thursday.

The health study originally was requested in 2001 by the International Joint Commission, the joint U.S.-Canada agency that oversees Great Lakes and border waters issues, including pollution. Both Canadian and U.S. leaders of the commission have officially asked the CDC to release the report but have been rebuffed.

The report has undergone scientific peer review since 2004, and the full report was scheduled for release in July 2007. But the chief of the ATSDR at the time said the report was "well below expectations," and has refused to release it, according to a letter obtained by the Center for Public Integrity.

But scientists who helped research and review the report, along with key lawmakers, say the CDC has refused to release the final document in an attempt to avert public concerns about industrial pollution.

Dr. Peter Orris, a professor at the University of Illinois School of Public Health in Chicago and an original peer reviewer of the report, said he was asked to "re-review" the report by CDC officials who were concerned it would scare the public by making implied links between the toxic sites and increased rates of disease.

Orris said both the Great Lakes toxic site data and the public disease statistics are readily available to the public, he said, and it "makes sense" to bring the two together to see if there's any geographic overlap.

"Are there weaknesses in the data we have available? Yes. Does that merit withholding the information? Absolutely not," Orris said. "There are some interesting questions raised by this report that should help define our research agenda. But that's a decision each community should get to make on its own ... It's my opinion that people generally don't overreact and that, if anything, the public generally does not have enough information."

The Center for Public Integrity describes itself as a nonprofit organization "dedicated to producing original, responsible investigative journalism on issues of public concern." The Washington-based group is nonpartisan and nonadvocacy.