Here at Beijing's Tiananmen Square, guards are busy keeping up with the return of thick smog. Haze mixed with a sandstorm on Thursday (February 28) to blanket the capital in toxic levels of air. A reading of hazardous particulate matter - or PM 2.5 - showed levels well beyond recommended daily intake. Air quality fell to the worst on record in January. It's become a major challenge for new leader Xi Jinping, who'll become president at the National People's Congress (NPC) next week. Residents here call for action. SOUNDBITE: (Mandarin) 40-YEAR-OLD BEIJING RESIDENT HU JING, SAYING: "Smog had already been forecast but now there's a sandstorm mixed with it! So I can't open my eyes or mouth. Just look at me! I'm heavily dressed from head to toe! If this weather continues in Beijing it will certainly damage everyone's health. So I hope leaders at the NPC attach importance to this problem." State TV warned drivers to take care as visibility dropped to around 500 metres (1,640 feet). Cities in surrounding provinces also suffered poor air.