1. d Aerosol and Environmental Division , Institute of Earth Environmental, Chinese Academy of Science , Xian , China
2. a Division of Atmospheric Sciences , Desert Research Institute , Reno , Nevada , USA
3. b Department of Environmental Health Sciences , Columbia University, New York , New York , USA
4. c Columbia Center for Children's Environmental Health , Columbia University, New York , New York , USA
5. e Department of Civil and Structural Engineering , Hong Kong Polytechnic University , Kowloon , Hong Kong