Cellular effects of thirdhand tobacco smoke from smokers' homes.

After the cigarette is extinguished, many toxic compounds remain in the environment and accumulate in the air or on surfaces. This exposure is termed thirdhand smoke (THS) and its risks are poorly known. The aim of the study was to evaluate the cellular effects of THS from smokers' homes. Papers were placed in nine smoker's home and three nonsmoker's homes. An area equivalent to the paper size was cleaned with a cotton wipe. A549, Hep-2 and 3T3 cells were exposed to THS for 24 h and cellular functions were assessed by MTT, neutral red (NR) reuptake and trypan blue exclusion assays. High levels of nicotine were found in samples from smokers' homes. Cellular proliferation was similar in almost all samples after THS exposure. Few changes in the cellular functions were observed, mainly higher mitochondrial activity, in paper samples. We are able to detect markers of THS collected from smokers' homes, but a clear evidence of cellular toxicity cannot be demonstrated by the present assays. This is the first study to evaluate the cellular effects of THS samples collected from smokers' homes.