The smog in China is at its thickest and most dangerous level ever recorded, say environmental campaigners. Photographs revealed buildings disappearing into the sky and neon signs floating ominously in mid-air as swathes of smog engulfed the city of Changchun, the capital of Jilin province in the northeast.

The harmful pollution particles known as PM2.5, widely regarded as having a highly detrimental effect on health, were at a level of 860 micrograms per cubic metre, reports AFP. The World Health Organisation recommends a maximum level of 25 micrograms, meaning that the smog is just under 35 times more harmful in Changchun than it should be. Howeverin Shenyang, a city close to Changchun, levels of PM2.5 reportedly rose to between 1,125 and 1,400 micrograms. That’s 50 times over the recommended limit. Authorities in Changchun called a state of emergency and instructed schools to cancel any outdoor activities and advised residents – who already routinely wear masks out of the house – to stay inside.

According to AFP, the smog is so bad in Changchun that one resident thought buildings were on fire. Shops have sold out of face masks, hospitals were reportedly flooded with patients suffering from respiratory problems and flights had to be cancelled as pilots were unable to see.

What are we doing to our planet? The United Nations Climate Change Conference will be held in Paris, from November 30 to December 11.