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Smog the silent killer 「霾」 葬健康

(added on 2016/12/23)

%copy; 2016 SpatioEpi.com
Data source: CMA, NBS, PRC government
Map created by CUHK SpatioEpi Group


Every year when winter comes, cities in northern China often have to face serious smog weather. In 2016, the adverse weather began from Chengdu in late November, followed by worsened situations in December in the capital city Beijing and nearby provinces. Up to 17th December, a total of 23 cities had issued the "red alert", the highest level of the four-tier smog warning system. Bad weather led to school suspension and air traffic cancellation. Apart from impacting daily life, citizens' health was also seriously threatened. In Beijing, there were reports of children admitted to hospital due to respiratory diseases.

The map shows the 23 cities that had issued red smog alert, their respective population size and the atmospheric concentration of PM2.5 reported by China Meteorological Administration on 16th December. The accumulation of environmental pollutants was particularly serious around the capital. This is the combined effect of (1) intensive pollutant emission from the industrialized and developed North China plain and (2) failure of air pollutants to disperse in the mountainous region in the west.

This map was created with data collected from China Meteorological Administration and National Bureau of Statistics of the People’s Republic of China.




Related Article

Particulate matter (PM) 懸浮粒子

Particulate matter represents a complex mixture of small particles and liquid droplets suspended in the air. Major sources of particulate matter include construction activities, road dust re-suspension and combustion.

Particulate matter with aerodynamic diameter smaller than 10 micrometres (μm) (PM10) is already small enough to pass through nose and respiratory tract and enter our lungs. Chronic exposure to particulate matter increases the risk of cardiovascular and respiratory diseases, or even lung cancer. Those particulate matter smaller than 2.5 μm (PM2.5), also known as fine suspended particles, is especially harmful. It is one of the most important parameters for air pollution monitoring.

In Hong Kong, Air Quality Health Index (AQHI) was introduced to replace the late Air Pollution Index in December 2013 from Environmental Protection Department, HKSAR. Individuals with lung and heart disease, influenza, asthma, elderly people and children are sensitive to PM. They are advised to reduce physical exertion and outdoor activities and avoid prolonged stay in areas with heavy traffic when AQHI is at high health risk category or higher.


氣動力學直徑小於十微米的顆粒物可以經鼻腔及呼吸道進入肺部,長期暴露於此類可吸入顆粒物會增加患上心血管病、呼吸系統疾病甚至肺癌等風險。 其中小於2.5微米的懸浮粒子,亦稱微細懸浮粒子,尤其有害。它是衡量空氣污染指標的其一重要成份。

香港政府環境保護署於2013年12月以空氣質素健康指數代替舊有的空氣污染指數。心肺疾病、感冒或哮喘患者與及長者和小童都可能對可吸入顆粒物特別敏感,當空氣質素健康指數健康風險級別為高或以上水平時 ,他們都應減少體力消秏及戶外活動,亦應避免長時間在交通繁忙的街道上逗留以減少顆粒物的吸入數量。

Smog 霾

What is smog? 什麼是霾?

Smog (a word formed by combining smoke and fog) is a product of intensive air pollution. In urban cities, combustion of fuels and vehicles on the road lead to the generation of air pollutants. These include particulates, oxides of nitrogen and carbon monoxide, causing diffuse pollution to occur. Occasionally when the wind speed is low and where temperature inversion occurs at higher altitude, pollutants could be trapped at the origin of emission, leading to their accumulation in the air. Sunlight may further trigger reactions and turn some of the primary pollutants into secondary pollutants such as ozone. The resulting smog is toxic and highly oxidizing. Prolonged exposure to smog may cause health hazards such as asthma, cancers, heart diseases and even death. In recent years in northern China, with increasing amount of coal being burnt during winter, smog has become more common. The Ministry of Environmental Protection planned to maintain PM2.5 level below 73 μg/m³ in Beijing-Tianjin-Hebei region by 2017.

霾、或霧霾(其英文smog是由smoke煙及fog霧所組成)是由嚴重空氣污染所造成的環境現象。在市區城市,燃燒化石燃料及行駛中的汽車會產生大量污染物。這些污染物包括懸浮粒子、氧化氮及一氧化碳,在空氣中造成擴散性污染。 當天氣結合低風速及逆溫效應時,污染物便會於排放地積聚。陽光進一步將這些空氣污染物轉化為具毒性及強氧化力的化合物如臭氧。在霧霾天氣底下,長期吸入這些污染物會對身體組成嚴重影響,如哮喘、癌症、心臟病甚至死亡。近年於中國北方,由於冬天的燃煤需求不斷增加,導致霧霾出現更加頻繁。有見及此,國家環境局計劃將京津冀地區的PM2.5水平於2017年終前維持每立方米73微克水平。

How does smog warning work in China? 中國的霾預警如何運作?

In 2013, the China Meteorological Administration revised the previous smog warning system into a blue-yellow-orange-red four-tier signal in ascending order of seriousness. Red alert, the most serious warning, denotes the occurrence of at least one of the following conditions now or within the next 24 hours: (1) smog with relative humidity (R.H.) <80% and visibility lower than 1000m; (2) smog with R.H.⩾80% and visibility below 1000m, PM2.5 concentration>250μg/m³; (3) smog with visibility lower than 5000m, PM2.5 concentration>500μg/m³


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