The researchers examined urine samples from the subjects and tried to figure out if a biologic marker known as NNAL could predict cases of lung cancer.

研究人员对受试者的尿样进行了检测，试图寻找一种叫做NNAL的生物标记，这种标记可以看作是肺癌的前兆。

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Studies have found that laboratory animals with high concentrations of NNAL had higher rates of lung cancer, but its effect in humans has not been clear.

研究发现，高浓度NNAL的实验室动物有较高的肺癌发病率，但它对人类的影响尚不清楚。

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It releases into your body when you inhale smoke, quickly passes through the liver, gets metabolized and releases NNAL, a byproduct of NNK, into the bloodstream.

当你吸烟时，它会在身体里扩散，迅速穿过肝脏代谢并释放出NNAL，然后产生NNK，进入血液。

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