"WASHINGTON -- A cancer report that concludes Americans are under constant assault from carcinogenic agents has heartened activists, who hope that finally government and policymakers will pay attention to their concerns.

But the report from the President's Cancer Panel on Thursday has underwhelmed most mainstream cancer experts and drawn only a puzzled response from the White House. Even members of Congress who usually are eager to show they are fighting to protect the public have been mostly silent.

Cancer experts say for the most part that we already know what causes most cases of cancer and it's not pollution or chemicals lurking in our water bottles. It's tobacco use and other unhealthy behaviors, says Dr. Graham Colditz of the Washington University School of Medicine in St. Louis.

"The lack of physical activity, weight gain, obesity clearly account for 20 percent or more of cancer in the United States today," Colditz said in a telephone interview.

The report, he said, gives people an excuse to ignore the risk factors most in their control."

Maggie Fox reports for Reuters May 10, 2010. [2]