The authorities in the Chinese capital, Beijing, have issued their highest smog warning so far this year. The "orange level" alert declared on Sunday is the second highest possible, requiring factories to cut production.
Air pollution is a chronic health-risk for those living and working in the capital and other major Chinese cities. Some reports suggest that visibility has fallen to a few hundred metres in some places.
At noon on Sunday, the air pollution monitor operated by the US Embassy in Beijing reported that the intensity of the poisonous, tiny particles of PM 2.5 reached more than 400 micrograms per cubic metre in some of the worst-affected areas. The World Health Organization considers 25 micrograms per cubic metre to be a safe level.
Coal-powered industries and heating systems, as well as dust from construction sites, all contribute to the smog which has been exacerbated by humidity and a lack of wind.
Air pollution is a perennial problem in China's northeast which is home to many heavy industries including coal mining. Earlier this month, China's state media and many residents criticised high pollution levels in the north-eastern city of Shenyang.
The People's Daily said PM 2.5 levels exceeded 1,400 micrograms per cubic metre. Activists said that may have been the "worst ever" air quality seen in the country.
Earlier this year China's environment ministry announced that only eight out of the country's 74 biggest cities had passed the government's basic air quality standards in 2014. Most of the cities found to have the worst air were in the northeast.
China is attempting to cut pollution but still relies heavily on coal for its energy and industrial needs.
中國都城北京的專家們，已宣布了迄今為止最高的霧霾警報。周日頒布的“橙色級”警報是二級警報，而且有關部分還請求工場削減臨盆。
氛圍汙染對付在都城和其他重要都會生存和事情的人來講，是一種慢性康健危害。有報導指出，在一些處所，能見度已降低到幾百米。
周日正午，美國駐北京大使館操縱的氛圍汙染監測儀表現，在一些受影響最緊張的地域，可吸入顆粒物，即PM2.5，每立方米跨越了400微克。而天下衛生構造以為平安規模是每立方米25微克。
煤炭產業和供熱體系，和修建工地的塵土，都邑因濕度和風力減小而加重霧霾的構成。
對付以煤礦為主能源的東北重產業基地，汙染是個永久的題目。本月初期，中國官方媒體和很多住民批駁了中國東北都會沈陽的重度汙染。
國民日報稱，沈陽的可吸入顆粒物，即PM2.5，到達了1400毫克每立方米。部門激進人士乃至表現，這是天下“最差”的氛圍質量了。
本年初期，中國情況部宣告，2014年，在中國的74個大都會中，唯一8個到達了當局劃定的根本氛圍質量尺度。氛圍汙染最緊張的都會大多半都處於中國東北部。
中國正在盡力削減汙染，然則今朝仍舊依附煤作為重要產業能源。
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