A new study has found that tobacco companies knew that cigarettes contained a radioactive substance called polonium-210, but hid that knowledge from the public for over four decades. "Having these elements in cigarettes is bad, because they're linked to tar, and can't be expelled from the lungs, and stay in a patient's body for longer periods of time," said Aditi Satti, a pulmonologist at Temple's School of Medicine. "This can increase your chances of lung cancer."