Third-hand smoke is the residue that clings to surfaces long after the second-hand smoke from a cigarette has cleared out.
Now, researchers say third-hand smoke causes significant genetic damage in human cells.
They also found that chemicals in samples exposed to chronic third-hand smoke exist in higher concentrations and cause more DNA damage, than samples exposed to acute third-hand smoke.
Researchers say the results of the study suggest residue becomes more harmful over time.