Shanghai air pollution hovers near index's limit

Thick smog enveloped Shanghai yesterday, with the air staying "heavily polluted" all day, according to the official index - a first since autumn began.

Photos shared by residents on social media showed a murky sky - an image usually associated with the city's long-time competitor, Beijing, or "Grey-jing" as some have taken to calling it.

The air quality index exceeded 200 at 4am and stood at 255 as of 8pm, according to the Shanghai Environmental Monitoring Centre. Any index reading of 300 or above is classified as severely polluted.

The average concentration of PM2.5, tiny particulates that pose the biggest threat to health, stood at about 200 micrograms per cubic metre over a 24-hour period - a reading that is eight times what the World Health Organisation deems safe.

People remarked online they were shocked Shanghai was "catching up" with Beijing, which has suffered from heavy air pollution for years.

"First it was our much pricier number plates, now Shanghai is again beating Beijing," one resident wrote on Sina's Weibo, referring to the financial hub's pricey vehicle registrations.