Conference Paper 1)
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IDENTIFICATION OF CYTOTOXIC CHEMICALS IN THIRDHAND SMOKE Vasundhra Bahl*1,2, Suzaynn Schick 3, Mohamad Sleiman4, and Prue Talbot1
1 Department of Cell Biology and Neuroscience, University of California, Riverside, 2 Environmental Toxicology Graduate Program, University of California, Riverside, 3 Department of Medicine, University of California, San Francisco, 4Indoor Environment Group, Lawrence Berkeley National Laboratory
Little information is available on the health effects of thirdhand smoke (THS).
Our work evaluates the adverse effects of THS on mouse neural stem cells, an in vitro model for the neonatal brain. Cytotoxicity was studied using the MTT assay which evaluates conversion of a tetrazolium salt to a colored formazan by mitochondrial reductases. Terry cloth exposed to cigarette smoke for 110 hours over 1 year was stored at room temperature to allow aging of THS, and extracts were prepared after different times of aging. THS aged for 11 months on terry cloth was cytotoxic to mNSC, causing complete cell death in the MTT assay at the highest dose; however, cytotoxicity was lost when the terry cloth was aged for an additional 5 months. Another sample of terry cloth was exposed to cigarette smoke for 19.5 hours over 1 month. The THS extract obtained immediately after the smoking period was cytotoxic to mNSC in the MTT assay causing 50% cell death at the highest dose, but lost its activity when allowed to age for an additional 45 days. These results indicate that as little as 1 month of accumulation of THS is sufficient to produce cytotoxicity and that this toxicity is lost with aging.
The decrease in cytotoxicity could be due to loss of volatile organic chemicals (VOC) that are present in cigarette smoke or degradation of chemicals. Authentic standards of VOC present in THS were tested individually and in combination to determine which could contribute to cytotoxicity. Out of the chemicals tested to date, 2,5-dimethylfuran (DMF) and acrolein were cytotoxic in the MTT assay. Combining up to 5 chemicals together did not affect the dose response curves.
Because of their high volatility, an additional trial was performed with each chemical being replaced at 4 hour intervals for 48 hours. Dose response results were not affected except for DMF which had increased potency in this experiment.
These results are consistent with the conclusion that DMF and acrolein contributed to the cytotoxicity observed in the terry cloth extracts.
FUNDING: Tobacco-Related Disease Research Program of California
JUSTIFICATION: Identification of two cytotoxic chemicals in thirdhand smoke could affect public health policies and remediation of environments containing thirdhand smoke.
CORRESPONDING AUTHOR: Prue Talbot, PhD, Professor, UCR, Cell Biology & Neuroscience, Spieth Hall, Riverside, CA 92521, United States, Phone: 951-827-3768, Email: email@example.com