Ozone pollution in Beijing
北京的臭氧污染
Ozone has overtaken PM2.5 to become the top air pollutant in Beijing, Tianjin and Hebei in nearly half of the bad air days in summer, according to an air quality report released by the Ministry of Environmental Protection.
环保部空气质量报告显示，入夏以来，京津冀地区的近半数污染日内，臭氧均代替PM2.5成为空气首要污染物。
The levels of ozone in some districts of suburb Beijing have surpassed 300 micrograms per cubic meter in recently days, as an average level of more than 200 micrograms in eight hours is defined as "pollution".
按照空气质量标准，臭氧8小时平均浓度超过200微克/立方米即为污染，但北京部分郊区近日臭氧浓度超过了300微克/立方米。

Ground level ozone is created by a chemical reaction between sunlight and emissions from vehicles, thus hot, sunny days see a rise in the pollutant.
汽车排放的尾气，在阳光辐射下会发生化学反应，在近地面生成臭氧，因此气温炎热、阳光强烈的夏季易发生臭氧污染。
Inhaling ozone can irritate the lungs and cause wheezing and coughing.
臭氧被人体吸入后会刺激肺部，引发气喘和咳嗽。