A thick grey pall hangs over Beijing's Tiananmen Square on Monday, blocking out much of the sunlight.<br/> <br />Two weeks after air pollution in the Chinese capital reached record-breaking levels, smog shot back up to conditions considered "hazardous".<br/> <br />The headquarters of China's state CCTV all but disappeared from view at a distance of just 300 metres.<br/> <br />Beijing's official air quality monitoring system showed noon readings of around 350 on an index that measures particulate mass in the air.<br/> <br />A level of more than 300 is considered dangerous, while the World Health Organization recommends a daily level of no more than 20.<br/> <br />By 1pm a reading from the U.S. embassy in Beijing peaked at 423.<br/> <br />This fed up resident said she wanted the government to "sort out the environment".<br/> <br />Emissions from factories and heating plants, fumes from millions of vehicles and the burning of coal often conspire to blanket the city in a pungent haze that can become trapped in certain weather conditions.<br/> <br />Extreme air pollution is known to cause cardiopulmonary disease, lung cancer and acute respiratory infections.
