Objective This study was aimed at comparing cardiorespiratory fitness (CF), measured as VO 2 max, amongst school children exposed to varying levels of particulate matter (PM 10), and air pollution in Bogotá, Colombia. Methods This was a cross-sectional study; it involved 1,045 children aged 7-12 attending four public schools served by different public transit routes and systems. Three schools were classified as being highly polluted (HP) and one slightly polluted (SP). The children and their parents were surveyed to collect data regarding their socio-demographic characteristics, physical activity habits and respiratory disease