Indoor and outdoor PM2.5 in schools of Santiago, Chile: influence of local climate zone (LCZ) environment

Abstract

This study measured PM2.5 concentrations in 30 schools in Santiago, Chile. Sampling of schools was random with respect to local climate zones (LCZ). Low-cost PM2.5 sensors were installed both indoor and outdoor. The outdoor sensors’ data were highly correlated with the closest regulatory air quality monitoring station (median R-2 = 0.62, IQ range: [0.5, 0.71]). Indoor and outdoor PM2.5 levels were highly correlated (median R-2 = 0.91, IQ range: [0.76, 0.95]) because of natural ventilation conditions. There was no significant difference between the average PM2.5 in classrooms located far (30 mu g/m(3)) and near (30.4 mu g/m(3)) the street (p = 0.9), suggesting little PM2.5 spatial variability within schools’ boundaries. High classroom infiltration factors (F-inf) were estimated (median F-inf = 0.9, IQ range: [0.82, 0.98]). Public schools had significantly (p < 0.05) higher indoor concentrations than private ones in each season (57.1 and 39.3 g/m(3) in autumn, 43.1 and 35.2 mu g/m(3) in winter, 16.9 and 12.6 mu g/m(3) in spring). In winter season schools in zones with dense midrise buildings (LCZ2) had higher average outdoor PM2.5 concentrations (55.8 mu g/m(3)) than those in zones with open arrangements of midrise buildings (LCZ5) (48.3 mu g/m(3)) – p = 0.06. In spring season, outdoor average concentration was higher for schools in a dense mix of tall buildings (LCZ1) (22.5 mu g/m(3)) in comparison to those in open mid-rise buildings (LCZ5) (16.7 mu g/m(3)) – p = 0.02. Hence, higher building density (LCZ classification) due to limited air circulation promotes higher outdoor and indoor PM2.5 in schools. This should be considered in future urban planning.