The mean blood lead levels in the 12-to-19-year-olds were 1.5 micrograms per deciliter in 1991 to 1994 and 1.1 micrograms per deciliter from 1999 to 2000, researchers say.

研究人员说，从1991年到1994年，12至19周岁美国人的平均血铅水平在0.015微克每毫升；1999年到2000年这一数字变为0.011微克。

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High levels of lead (at least 10 micrograms of lead per deciliter of blood) can lead to brain and nervous system damage, behavioral and learning problems and sluggish growth.

高浓度的铅(每分升血液中含铅10毫克以上)会导致脑部和神经系统受损，导致行动和学习能力方面的问题，还可能使发育缓慢。

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Currently, ten micrograms of lead per decileader (deciliter) of blood is what Federal Health officials in the United States call a level of concern.

最近，美国联邦健康署公布每十分之一公升血液含有10微克铅就是危险含量。

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