(Reuters) - Americans are being "bombarded" with cancer-causing chemicals and radiation and the federal government must do far more to protect them, presidential cancer advisers said on Thursday. U.S. | Health Although most experts agree that as many as two-thirds of cancer cases are caused by lifestyle choices like smoking, poor diet and lack of exercise, the two-member panel said many avoidable cancers were also caused by pollution, radon gas from the soil and medical imaging scans. "The incidence of some cancers, including some most common among children, is increasing for unexplained reasons," wrote the two panel members, 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. Cancer is the No. 2 killer of Americans, after heart disease. Kripke and Leffall, both appointed by President George W. Bush, decided in 2008 to focus a report on potential environmental links to cancer. "The American people -- even before they are born -- are bombarded continually with myriad combinations of these dangerous exposures," they wrote in a letter to President Barack Obama at top of the report. "The panel urges you most strongly to use the power of your office to remove the carcinogens and other toxins from our food, water, and air that needlessly increase healthcare costs, cripple our nation's productivity, and devastate American lives." A White House spokesman indicated he had not yet seen the report and the National Cancer Institute declined comment. KNOWN RISKS The American Cancer Society said the report downplayed known risks that cause most cases of cancer including tobacco, obesity, alcohol, infections, hormones and sunlight. "The report is most provocative when it restates hypotheses as if they were established facts," the society's Dr. Michael Thun said in a statement. "For example, its conclusion that 'the true burden of environmentally (pollution) induced cancer has been grossly underestimated' does not represent scientific consensus." The American Chemistry Council, an industry group, agreed and said the report underemphasized prevention efforts. The report, available at pcp.cancer.gov, offered some of its own advice to consumers. For instance, the report said that although large studies have found no links between cell phone use and cancer, people would be prudent to wear headsets and make calls quickly. The report delighted environmental groups that have been pressing for more regulation of chemicals. "It is very gratifying to see this remarkable report that addresses those concerns," said Julia Brody, executive director of the Silent Spring Institute. "The 40-year war on cancer has been called for what it is ... a failure," Jeanne Rizzo, president and chief executive of the Breast Cancer Fund, which advocates about links between chemicals and breast cancer, told reporters in a telephone briefing. New Jersey Democratic Senator Frank Lautenberg said he hoped the report would help boost support for a bill requiring closer regulation of chemicals. "My Safe Chemicals Act will require testing of all chemicals, and take substances off the market if the manufacturer cannot prove they are safe," he said.