举例来说，1997年，美国环保署意图降低地表臭氧量标准——一种部分由石油精炼排放的污染物造成的污染。
In 1997, for instance, the E.P.A. moved to reduce surface ozone, a form of pollution caused, in part, by emissions from oil refineries.
地表臭氧和颗粒污染物是人类健康的最大威胁。
Ground level ozone and particle pollution are the greatest threat to human health.
地表臭氧和颗粒污染物是人类健康的最大威胁。
Ground level ozone and particle pollution are the greatest threat to human health.
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