By Dr. Mallika Marshall

BOSTON (CBS) – You’ve probably heard of second-hand smoke but what about third-hand smoke?

A new study finds that residual chemicals from tobacco smoke can persist on indoor surfaces like furniture, carpets, and clothing even if no one has smoked there for many years.

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Researchers at Drexel university in Philadelphia analyzed the air in a non-smoking, unoccupied classroom over the course of a month.

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They themselves were surprised when they found a significant amount of chemical residue associated with tobacco smoke.

The concern is that these potentially harmful chemicals could be absorbed through the skin, ingested or inhaled and can move through buildings easily through the HVAC system.

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Studies done on mice have shown these particles could have health effects but more research needs to be done on humans.

Dr. Mallika Marshall