A cleaner adjusts her face mask as she works in front of Beijing's Tiananmen Gate June 5, 2012. A senior Chinese official demanded on Tuesday that foreign embassies stop issuing air pollution readings, saying it was against the law and diplomatic conventions, in pointed criticism of a closely watched U.S. embassy index. The level of air pollution in China's heaving capital varies, depending on the wind, but a cocktail of smokestack emissions, vehicle exhaust, dust and aerosols often blankets the city in a pungent, beige shroud for days on end. REUTERS/David Gray (CHINA - Tags: ENVIRONMENT SOCIETY)