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。

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Objective To study the effect of low-level ozone on growth and development of mice.

目的研究低浓度臭氧对小鼠生长发育的影响。

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While the atmosphere's ozone protects us from the sun's rays, ground-level ozone is a pollutant.

大气层中的臭氧保护我们免受阳光的辐射，而地面的臭氧是一种污染物。

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WMO scientists assess and monitor air pollutants such as ground-level ozone,smog, particulate matter, sulfur dioxide and carbon monoxide.

VOA: standard.2009.03.23

Scientists think they have identified one key reason why ground-level ozone remains stubbornly high in Europe.

BBC: London's clue to stubborn ozone levels

At ground level ozone is a dangerous pollutant, but at altitude it blocks the passage of harmful ultraviolet light.

ECONOMIST: Atmospheric science: Fake flakes | The

Ms. Jackson late last year delayed a decision on whether to tighten the government's limits on ground-level ozone, a primary ingredient in smog.

WSJ: EPA Tangles With New Critic: Labor