{"id":6036,"date":"2018-06-11T14:19:45","date_gmt":"2018-06-11T06:19:45","guid":{"rendered":"https:\/\/smartairfilters.com\/?p=6036"},"modified":"2026-05-20T12:50:35","modified_gmt":"2026-05-20T04:50:35","slug":"analysis-shows-ozone-levels-rising-across-china","status":"publish","type":"post","link":"https:\/\/smartairfilters.com\/en\/blog\/analysis-shows-ozone-levels-rising-across-china\/","title":{"rendered":"Ozone Pollution: Often Invisible, Always Dangerous"},"content":{"rendered":"

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When summer rolls around, enticing blue skies often draw people outside. Throw on top the fact that most cities in China have less PM2.5 pollution in the summer<\/a>, what\u2019s stopping us from heading outside?<\/section>\n
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Ozone Pollution on Rise Across China<\/h2>\n
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Ozone has been on a steady increase<\/a> across China in recent years. To assess China’s ozone situation, Smart Air analyzed 2019 ozone levels for 12 of China\u2019s major cities. \u00a0We found that during summer months (May-August) in 2019, 83%<\/strong><\/span> of the cities analyzed had ozone levels exceeding the WHO standard. Only one city was below the WHO limit: Shenzhen.<\/section>\n
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Averaging across the entire year, 25%<\/span><\/strong> of cities exceeded the WHO limit (Tianjin, Wuhan, Guangzhou). However, three other cities were not far off the limit (Beijing, Changsha, and Shanghai).<\/section>\n
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China’s ozone performance is still far better than its particulate pollution performance. For PM2.5, 100% of cities<\/strong> failed to meet the WHO annual limit<\/a>. Thus, is ozone really such a big risk? Turns out, ozone turns up just at the worst time.<\/section>\n
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How Does Ozone Pollution Vary Throughout The Year?<\/h3>\n<\/section>\n
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Using Beijing<\/strong> as an example, ozone is\u00a0highest from May to August.<\/strong> Ozone reaches almost two times<\/span><\/strong> the WHO limit of 100\u00b5gm\/m\u00b3 in June.<\/section>\n
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Shanghai<\/strong>\u00a0shows the same monthly pattern, although it\u2019s less pronounced. Shanghai’s ozone reaches 30% above<\/strong> <\/strong><\/span>the WHO limit from May to July<\/strong>.<\/section>\n
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Where Does Ozone Pollution Come From?<\/h3>\n

Ozone Pollution = Exhaust + Sunlight<\/strong><\/p>\n<\/section>\n

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Ozone tends to peak during the summer because two important ingredients \u2013 heat and sunlight \u2013 are more common in the summer. When sunlight hits pollutants from cars, other vehicles, and power plants, it reacts to form ozone.<\/section>\n
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Ozone typically peaks in the hottest, sunniest part of the day. In most places, that’s around noon or early afternoon. For example, in Rio de Janeiro, Brazil, ozone peaks at 2:30pm.<\/section>\n
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\"Ozone<\/section>\n
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Ozone Turns up Just at the Worst Time<\/h3>\n<\/section>\n
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The health effects of ozone can be pretty serious.\u00a0Ozone causes coughing<\/a>, asthma, and long-term damage that increases the chance of heart attacks and cancer. What\u2019s more, on sunny and warm days, we often spend more time outside, which means we\u2019re more exposed to more ozone in the air.<\/section>\n
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Health Effects of Ozone: Children More at Risk<\/h3>\n<\/section>\n
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Children breathe more rapidly and have more lung surface area for their body size<\/a> compared to adults, which means they take in more air per minute and inhale more air for their size. Pound-for-pound, children breathe 50% more air than adults<\/a>.<\/section>\n
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Children are also more likely to have asthma. Thus, ozone harms children even more than adults.<\/section>\n
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What Are The Official Ozone Pollution Limits?<\/h3>\n<\/section>\n
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The World Health Organization\u2019s\u00a0limit for ozone is 100\u03bcg\/m\u00b3<\/strong><\/span><\/a>. Beijing\u2019s ozone often surpasses that limit, such as the day before this article was written, when levels reached 1.4 times the WHO ozone limit.<\/section>\n
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Two apps give easy access to local ozone data. The AirVisual App and Blue (Weilan) Map App both report ozone readings.<\/section>\n
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Is Ozone a Problem Indoors?<\/h3>\n<\/section>\n
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Since the source of most ozone is from vehicles and power plants, most ozone comes from outdoors, not indoors. What\u2019s more, fortunately, ozone is highly unstable. When ozone comes into contact with indoor surfaces, it gets removed from the air<\/a>.<\/section>\n
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In homes that have air conditioning and windows closed, studies have found that ozone is typically less than 10%<\/strong> of outdoor ozone levels<\/a>. But if you have a central air system that brings in outdoor air, ozone levels will be higher. And if the doors and windows open, studies have found indoor ozone is about 50%\u00a0to\u00a075%<\/strong> of outdoor levels<\/a>.<\/section>\n
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Can I Remove Ozone From My Home?<\/h3>\n<\/section>\n
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Studies have shown that\u00a0activated carbon filters can reduce ozone<\/a>. However, it is harder to remove than particulate. Compared to HEPA filters, most carbon filters are nowhere near as effective at capturing ozone. HEPA filters can remove\u00a099% of particles from a single pass of air<\/a>. For ozone,\u00a0researchers estimate<\/a>\u00a0the average carbon filter removes about 60% of ozone in a single pass.<\/section>\n
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Another challenge is that most carbon filters need to be changed more frequently than particle filters.\u00a0<\/section>\n
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What Should I Do When Ozone Is High?<\/h3>\n<\/section>\n
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The United States Environmental Protection Agency recommends that people:<\/section>\n
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