This will be hard to forget next time you want to light up. Even scientists are shocked by the results of a study in the Chemical Research in Toxicology journal that shows the first few puffs of a cigarette can lead to immediate genetic mutations of a smoker's DNA. Researchers say that such rapid results are essentially the same as "injecting the substance directly into the bloodstream." Examining 12 smokers, scientists followed pollutants called polycyclic aromatic hydrocarbons or PAHs. One in particular, phenanthrene, trashed the subjects' DNA just 15 to 30 minutes after they smoked, "causing mutations that can cause cancer." The study was funded by the National Cancer Institute and the results serve as a stark warning to people considering smoking.