Secondhand smoke has killed millions of people, but new research out of the Lawrence Berkeley National Laboratory shows that something called "thirdhand" smoke might be just as dangerous. 

Thirdhand smoke is the residue left behind on walls, hair, and clothing after someone smokes. In the study, researchers exposed baby mice to materials contaminated with thirdhand smoke residue and found that they had a harder time gaining weight and had negative changes in their blood cell counts, when compared to mice not exposed to the residue. 

Read More:

National Geographic: Thirdhand Smoke Is Real-And Risky to Your Health

Scientific American: What is third-hand smoke? Is it hazardous?

University of California: Investigating link between thirdhand smoke and cancer