An oil refinery is seen in Norco, Louisiana in this August 15, 2008 file photo. Credit: Reuters/Shannon Stapleton

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.

The damage is that it distracts us, as a society, from actually acting on the things that are already in our grasp. I can take tobacco as the best example, said Colditz, noting that more than 20 percent of Americans still smoke despite nearly 50 years of cancer warnings.

And no state has even come close to banning smoking, although limits are going into place to restrict smoking in public.

We know that alcohol causes 4 percent (of cancers) and we deal with that to too little extent, as well, said Colditz, an expert in the epidemiology of cancer. Red meat is a known cause of colon cancer, he adds. We don't run out and ban all beef just because beef is a cause of colon cancer.


So it worries Colditz to see the two-member cancer panel -- Dr. LaSalle Leffall, professor of surgery at Howard University College of Medicine in Washington, and Margaret Kripke, an emeritus professor at the University of Texas M.D. Anderson Cancer Center -- recommend sweeping policy changes to focus on potential environmental causes of cancer.

Maybe up to 4 percent of cancer in the western world is caused by contaminants and pollution and yet we are chasing new, unknown causes rather that focusing on acting on what we know, he said. Things like this report are making it harder to move the nation to a healthier lifestyle.

Kenneth Cook, president of the Environmental Working Group, an activist group that conducts research into environmental health questions, disagrees with the assessment that chemical causes of cancer are only in the single digits.

As this prestigious body's report underscores, the federal government has failed to take aggressive action to protect people from chemicals that cause cancer, Cook said in a statement.

Cook hopes the report will prompt changes. The tide is shifting, thanks to irrefutable scientific research and a strengthening of political will in Washington.

But one government researcher, who asks not to be named, doubts it. In the past the President's Cancer Panel has not had much impact, the researcher said.

The panel was set up in 1971 as part of then-President Richard Nixon's war on cancer. It calls for more research into the potential chemical and environmental causes of cancer, including mobile phones and a plastic ingredient called BPA.

Such research is already under way and the agencies conducting it say it will take years and studying many thousands of people to tease out potential cancer signals.

One big problem -- people are soaked in chemicals, electromagnetic radiation, hormones and other known causes of cancer that can interact with thousands of genetic variations to start tumors growing -- or not. Figuring out whether any one ingredient is mutating a gene or set of genes in a certain way will be difficult.

The U.S. Centers for Disease Control and Prevention has a program to test 5,000 people each year for dozens of chemicals and to collate a database over time.

And last month researchers launched a giant study to track at least 250,000 people in five European countries for up to 30 years to see if there are any health effects from using mobile telephones.