Scientists say they have found the component of cigarette smoke that causes lung cancer.
The study, published in Thursday's issue of the journal Science, says the factor is found in the tar of cigarette smoke. Pfeifer says scientists knew tobacco tar contained numerous possible cancer-causing agents, but now he says his team has pinpointed the exact one. The cells then started dividing abnormally, eventually leading to tumors. Researcher say the finding refutes the tobacco industry's long-standing claim that there is no scientific proof that cigarette smoking causes cancer, despite stacks of studies showing people who smoke are more likely to develop the disease. The U.S. Food and Drug Administration, which is attempting to regulate tobacco, also declined comment on the study.