Fifty years after the first U.S. Surgeon General's report in 1964 warned about the link between smoking and lung cancer, research continues to identify more diseases that are directly caused by smoking. Cigarette smoke contains thousands of compounds, including 69 known to be carcinogens, chemicals that are directly involved in causing cancer. They are carried through the blood to many organs," said Stanton Glantz, director of the Center for Tobacco Control Research and Education at the University of California at San Francisco, who was not involved in compiling the report. In colorectal cancer, tumors often originate in the glands and the cells that cover the inside of the bowel.