Editing Smog (section)

==== China ====
{{main|Beijing#Air quality}}
Joint research between American and Chinese researchers in 2006 concluded that much of [[Beijing]]'s pollution comes from surrounding cities and provinces. On average 35–60% of the [[ozone]] can be traced to sources outside the city. [[Shandong]] Province and [[Tianjin]] Municipality have a "significant influence on Beijing's air quality",<ref>David G. Streetsa, Joshua S. Fub, Carey J. Jangc, Jiming Haod, Kebin Hed, Xiaoyan Tange, Yuanhang Zhang, Zifa Wangf, Zuopan Lib, Qiang Zhanga, Litao Wangd, Binyu Wangc, Carolyne Yua, [https://web.archive.org/web/20130724181603/http://www.cee.mtu.edu/~reh/papers/pubs/non_Honrath/streets07.pdf Air quality during the 2008 Beijing Olympic Games]. Accessed 23 April 2012</ref> partly due to the prevailing south/southeasterly flow during the summer and the mountains to the north and northwest.