Northeastern China has been blanketed in thick smog since the weekend, with pollutant levels hitting 50 times higher than the WHO recommended limit. Levels of PM2.5, the tiny airborne particles considered most harmful to health, surged to 1000 against the recommended 25 micrograms per cubic metre within 24 hours, in Shenyang, the capital city of Liaoning province. The smog affected visibility and suspended flights. Heavy pollution covers 21 cities in northeast as dangerous particles reach highest levels. The Ministry of Environmental Protection said that traffic control measures had been in place since Friday. The Shenyang city government was initiating a “level one red alert” emergency response, the highest level, telling schools to stop organizing outdoor activities, and reminding residents to “take green transit”, stay indoors and “take health precautions”. Chronic pollution problem has been linked to hundreds of thousands of premature deaths on the mainland, and has become a major source of popular discontent with the government.