UC Riverside

Thirdhand smoke (THS), which recently emerged as a potential health hazard, is the residue left on surfaces when secondhand smoke clears. It contains volatile organic compounds (VOCs), nicotine and related alkaloids, and chemicals formed during aging such as tobacco specific nitrosamines. The purpose of this dissertation was to evaluate the cytotoxicity of THS using in vitro models. A protocol was optimized to extract THS from fabrics into cell culture medium at room temperature for 1 hour. This protocol was effective for evaluating cytotoxicity of the extracts using mouse neural stem cells (mNSC) in the MTT assay. Fresh THS extracts from terrycloth exposed to 133 cigarettes over 11 months killed mNSC, disrupted motility and the cytoskeleton, and caused fragmentation and vacuolization of cells. THS aged at room temperature for 5 months no longer killed mNSC, indicating that the above effects were caused by VOCs that were lost from THS during aging. Twenty-five VOCs in THS were screened for cytotoxicity to mNSC and adult lung cells, and acrolein was identified as the most toxic VOC. Acrolein killed mNSC and adult lung cells at 10-5 M and decreased proliferation at 10-6 M by affecting the expression of TFDP 1, CASP 3, ANAPC 2, and WEE1, genes involved in cell cycle regulation. A smoker’s car was then simulated, and car seat cover and carpet were exposed to low levels cigarette smoke for 1 month. THS from these fabrics induced single strand DNA breaks in mNSC and adult skin cells. Terrycloth exposed to THS in an indoor chamber became more cytotoxic with longer exposure and lost toxicity after aging in the absence of fresh smoke. Because proteins enhanced extraction of cytotoxic chemicals, infants mouthing THS contaminated objects may have elevated intake of THS toxicants due to proteins in their saliva. Batches of THS that did not affect cell survival/proliferation caused stress-induced mitochondrial hyperfusion, increased mitochondrial membrane potential, increased ATP production; increased oxidative stress; and decreased expression of genes involved in mitochondrial function. These data show that relatively low levels of THS can disrupt cellular functions and have the potential to adversely impact health.