9 A needle trap sampler (NTS) packed with 60-80 mesh divinylbenzene (DVB) 10 adsorbent inside a 22-gauge stainless steel needle, was used as a micro sampling 11 device to extract chemical compounds in electronic cigarette (e-cigarette) aerosol. The 12 air samples were analyzed using a gas chromatography (GC)-mass spectroscopy (MS) 13 system to determine its constituents. Based on the experimental results, e-cigarette 14 smokers are exposed to high concentrations of nicotine (146±51 mg m -3 ) in

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... a long 15 session. If the e-cigarette liquid leaks through the filter of the cartridge of an e-16 cigarette, the user is exposed to nicotine of very high concentration of 914 mg m -3 . 17 Other main compounds in the smoke of e-cigarettes are vegetable glycerin, propylene 18 glycol and triacetin. The concentration of nicotine in the secondhand aerosol is lower 19 than 1 mg/m 3 (around 0.43-1.74 mg m -3 ). 20 21