Students exposure assessment towards PM number concentration while commuting from different transport modes during school timings

Among the various daily activities, commuting to school is considered as an important activity for the students. While commute, students are exposed to elevated particle concentrations that make significant contributions to their daily personal exposures. Present study compares the student exposure towards particle number concentration (PNC) and inhaled doses while commuting from different transports during morning (MT) and afternoon (AT) trips. PNC was measured from four different transport modes: two-wheeler (2W), three-wheeler (3W), passenger car (PC) and school bus (SB) during summer and winter seasons. In summer season, average total PNC was highest for 3W and SB during MT (5.53E+07 # m−3) and AT (5.29E+07 # m−3) trips respectively. However, in winter season, 3W has the highest average total PNC during MT (1.04E+08 # m−3) and AT (7.92E+07 # m−3) trips. Ventilation settings greatly influence the in-cabin PNC and found to be highest under window open (WO) scenario for PC and least under WO and window closed scenarios for SB during MT and AT trips respectively. The PNC exposure varies significantly with student seating positions inside SB and followed different trends during MT (front > middle > rear) and AT (rear > front > middle) trips. The mixed-effect multivariate linear regression model was used to estimate the effects of multiple predictor variables that influence the PNC measured from different transport modes while commuting. Background concentration (PNC) and meteorological variables (wind speed, ambient temperature and relative humidity) were important predictors of PNC measured while commuting and explained the variability between 0.04–27.31%.