Guardian: The government was today challenged on the number of premature deaths caused by poor air quality as new figures suggested it may be three times higher than previously claimed. The Campaign for Clean Air in London (CCAL) has written to the health secretary, Alan Johnson, to ask for clarification on the “full extent” of the health impact of poor air quality in Greater London. The group’s query comes in the wake of a report by the European Environment Agency, published last month, …