Greenpeace East Asia activists projected the words "Blue Sky Now!"onto a facade of the Drum Tower, an iconic historic building in Central Beijing Oct.10. PM2.5 (fine particles) concentration levels in Beijing have stayed above 250 micrograms per cubic meter for more than 40 hours. The World Health Organization's guideline for 24-hour PM2.5 concentration is 25 micrograms per cubic meter. Greenpeace East Asia calls on the Chinese government to accelerate its efforts against air pollution, and reminds affected residents to use proper protection.[Photo by Yang Di / Greenpeace]