Short-term exposure to ambient particulate matter and outpatient visits for respiratory diseases among children: A time-series study in five Chinese cities

Meng Li, Jie Tang, Huihua Yang, Lei Zhao, Ya Liu, Haoli Xu, Yali Fan, Jun Young Hong, Zhen Long, Xiaojuan Li, Jianduan Zhang, Wenting Guo, Miao Liu, Liangle Yang, Xuefeng Lai, Xiaomin Zhang