Two of the most toxic components of smog saw their readings exceed 1,000 on the air quality index in Shijiazhuang in China’s northern Hebei province on Monday, state media reported. One resident said her lungs felt “extremely uncomfortable” after she went walking outside for just a few minutes. The amount of PM2.5 and PM10 recorded in Shijiazhuang was greater than 1,000 micrograms per cubic metre at around 1pm, according to Xinhua. Both are types of suspended respirable particles that pose a risk to human health. The World Health Organisation recommends exposure to PM2.5 be limited to 25 micrograms per cubic metre over 24 hours, and 50 micrograms per cubic metre for PM10. Air pollution usually worsens in northern China during the winter, as coal is used to heat homes. Beijing issued a red alert for smog on Thursday, its first of the year, and 10 cities in Hebei have followed suit. Under China’s four-tiered warning system, a red alert will force suspension of factory production and school classes, as well as traffic reduction measures. Beijing’s ‘smog refugees’ flee the capital for cleaner air down south A cold front was forecast to gradually dispel the smog this week, but the pollution hasn’t shown any sign of weakening. One Shijiazhuang resident told Xinhua the air outdoors smelled like burning coal but was no less choking indoors. Pictures showing the darkened skies of Shijiazhuang have circulated on China’s social media. On Weibo, China’s version of Twitter, one use wrote: “Shijiazhuang is my hometown where I feel attached but I don’t know it as the haze gets worse … I cannot live without masks now and my body is starting to experience illness.” In another post, one commentator wrote: “It is said that even staying inside the house is unsafe today as smog exceeds the maximum air quality index. Seems like I will have to purchase more air purifiers!” Another commentator told the South China Morning Post she lived in the Shijiazhuang Hi Tech Industrial Development Zone and had travelled to the city’s Qiaoxi district, where she found the situation “equally horrible”. AND YOU THINK BEIJING IS POLLUTED? “I feel my lungs are extremely uncomfortable after walking outside a few minutes,” she said. In November last year, Shenyang, the capital of Liaoning province, saw its PM2.5 level exceed 1,000 micrograms per cubic metre.