China's smoggy skies dominate international headlines and threaten public health, spurring China's top policy-makers to declare a "war on pollution." But where does  PM 2.5 pollution come from? And what pollution control solutions have actually been working?
 
We sit down with Tonny Xie, Director of the Secretariat for the Clean Air Alliance of China (CAAC), to explore how local governments implement air pollution control targets, how cities like Shenzhen and Taiyuan are adapting air pollution control strategies to local conditions, and how CAAC is helping connect cities with technologies that may help clean up China's hazy skies. Read more about CAAC on their website: http://en.cleanairchina.org/.