2018 No https://doi.org/10.1016/j.jeem.2018.10.002 Chen, Siyu Asia Observational Epidemiology Study Modeling Students Elementary (K-5) Middle/Jr High (6-8) High School (9-12) Carbon Monoxide (CO) Particulate Matter (PM) Ozone (O3) Sulfur dioxide (SO2) Absenteeism Respiratory symptoms Air pollution Student health School absence China Air quality standards Using data from 3,000+ schools in China, study linked daily air pollution and temperature inversions to respiratory illnesses and student absences. Results showed harmful effects even below air quality standards, highlighting need for stronger environmental policies to protect children’s health and attendance.