Two Chinese marathon runners raise a placard which says, 'We want health, not pollution!', in Chinese by the Tiananmen Square at the Beijing Marathon. The runners decide to pull out of the marathon due to the heavy pollution. Despite the high level of pollution, with a PM2.5 (fine particulate matter) index showing as high as 405 or 'hazardous levels' at the start of the race, the organisers did not suspend or cancel the international event. The World Health Organisation says the daily pollution levels should not exceed an average of 25µg/m3 of fine particulate matter.