2021 No https://www.sciencedirect.com/science/article/abs/pii/S0013935121001110 Osborne Asia Australia Europe North America Experimental Elementary (K-5) Middle/Jr High (6-8) High School (9-12) Outdoor air pollution School Children Exposure Commuting Many of the included studies focused on nitrogen dioxide (NO2), and particulate matter (PM) both in the coarse and fine fraction, around schools across a range of countries. . Some studies also observed ozone (O3) and volatile organic chemicals (VOCs) outside schools. Our review identified that that children can encounter pollution peaks on the school journey, at school gates and in school playgrounds; that nearby traffic is a key determinant of concentrations outside schools; and that factors related to planning and urban design - such as the type of playground paving, and amount of surrounding green space - can influence school site concentrations.