Horror stories of China’s pollution problems are all over the place, but now the smog is so thick that it’s blocking several of the nation’s 20 million surveillance cameras.

The dense clouds of smog that sometimes blanket cities in China have myriad ramifications: they close businesses and schools, force residents indoors for days at a time, and are a notorious health hazard. They’re reportedly also, as the Chinese government is now acutely aware, a danger to national security.