Exposure to surfaces and objects that have been saturated in cigarette smoke, labeled as “third-hand smoke,” may be as deadly as smoking the cigarette itself.

A new study from the University of California, Riverside finds that the third-hand smoke that has soaked into the surfaces, objects and environment around people becomes increasingly toxic over time. Third-hand smoke is defined as the second-hand smoke that is allowed to settle on objects in any environment. Non-smoking children, co-workers, spouses and friends of smokers breathe in such carcinogens left in rooms exposed to smokers.

“We studied, on mice, the effects of third-hand smoke on several organ systems under conditions that simulated third-hand smoke exposure of humans,” Manuela Martins-Green, a professor of cell biology who led the study, said in a statement to UCR Today. “We found significant damage occurs in the liver and lung. Wounds in these mice took longer to heal. Further, these mice displayed hyperactivity.”