Secondhand smoke contains around 4000 types of harmful substances and the concentrations of these are even higher than that in the mainstream smoke . for instance , secondhand smoke contains 2 times more nicotin , 3 times more tar stimulant , 5 times more carbon monoxide and 50 times more carcinogenic substances 二手烟含有4000多种的有害物质，往往比主流烟还要多，例如：有2倍的尼古丁， 3倍焦油剌激物， 5倍的一氧化碳和50倍的致癌物质。
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Secondhand smoke contains around 4000 types of harmful substances and the concentrations of these are even higher than that in the mainstream smoke . for instance , secondhand smoke contains 2 times more nicotin , 3 times more tar stimulant , 5 times more carbon monoxide and 50 times more carcinogenic substances 二手烟含有4000多种的有害物质，往往比主流烟还要多，例如：有2倍的尼古丁， 3倍焦油剌激物， 5倍的一氧化碳和50倍的致癌物质。
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