Air pollution in Beijing hit levels hazardous to human health a majority of days in the past few weeks, and severe smog led to hundreds of flight cancellations and road closures last week. In some cases, traffic jams stretched as long as 30 miles and drivers were given emergency food and water handouts as they waited for visibility to return. Stores sold out of face masks and air purifiers, and bloggers posted photographs of the thick haze over the city blaming the Chinese government for failing to inform the public of the threat posed by air pollution. The U.S. embassy, which monitors pollution levels from its rooftop, reported hazardous pollution levels, with one day so polluted it was described as "beyond index." However, the China Environmental Monitoring Center released data showing that Beijing was "slightly" polluted, a discrepancy that, according to Bloomberg, could start a credibility argument that the Chinese government may lose. Mid-last week, a cold front swept away air pollution and levels dropped below "unhealthy" for the first time since December 3, but not before Beijing residents began independently taking pollution samples and posting the results online. Chinese officials claimed that air pollution levels were causing "confusion" and undesirable "social consequences" in 2009, according to leaked cables, and suggested that the embassy should consider limiting the availability of the data to Americans. Many Chinese citizens are now calling for increased disclosure of air pollution data. For the full story, see http://www.nytimes.com/2011/12/07/world/asia/beijing-journal-anger-grows-over-air-pollution-in-china.html?_r=1 and http://www.telegraph.co.uk/earth/earthnews/8938159/Chinese-lose-patience-with-pollution.html. For the story on citizen data collection, see http://news.yahoo.com/chinas-pollution-data-shrouded-official-fog-073658681.html. For the story on flight delays and economic impacts, see http://articles.latimes.com/2011/dec/07/world/la-fg-china-air-pollution-20111207.