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Comparison between average annual pollutant concentrations and absences by geographical characteristics. Each circle represents a school location and its corresponding annual pollutant concentrations or absence rate: (A) fine particulate matter (PM2.5) vs. latitude, (B) ozone vs. latitude, (C) absences vs. latitude, (D) PM2.5 vs. elevation, (E) ozone vs. elevation, and (F) absences vs. elevation.
