In 1991 the United States Congress asked NASA to investigate the hazard posed today by large impacts on Earth.
1991年，美国国会要求美国国家航空和航天管理局调查大型天体撞击对如今的地球所造成的危害。
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Environmentalists and local governments are increasingly concerned about the toxic hazard posed by old electronic devices and the cost of safely recycling those products.