We can decrease TSNA by ways of reducing level of precursors.

可通过控制两种前体物质的各种途径来降低烟草TSNA。

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All factors of effective precursors will affect their form and accumulation of TSNA.

凡影响前体物质的因素，都会影响烟草tsna的形成、积累和含量。

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The pre cured tobacco leaves of growing and ripeness do not contain TSNA, and they are formed and accumulated during curing, aging after harvesting.

大田正常生长及成熟的青烟不含TSNA，是采收后在调制、贮存陈化过程中逐步形成和积累起来的。

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