吸烟之所以危害健康是因为烟草中含有多种损害健康的化学物质，包括60来种致癌物质、烟碱、砷、一氧化碳和尼古丁。

Tobacco smoke is hazardous because it contains a number of unhealthy chemicals, including some 60 carcinogens (cancer-causing agents), tar, arsenic, carbon monoxide and nicotine.

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这些尼古丁替代品中的烟碱含量足以刺激心脏。

The amount of nicotine in these nicotine substitutes can be enough to excite the heart.

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这些尼古丁替代品中的烟碱含量足以刺激心脏。

The amount of nicotine in these nicotine substitutes can be enough to excite the heart.

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