Indoor air quality in school classrooms is a major pediatric health concern because children are highly susceptible to adverse effects from xenobiotic exposure. Fine particulate matter (PM2.5) emitted from mining waste deposits within and near cities in northern Chile is a serious environmental problem. We measured PM2.5 in school microenvironments in urban areas of Chanaral, a coastal community whose bay is contaminated with mine tailings. PM2.5 levels were measured in six indoor and outdoor school environments during the summer and winter of 2012 and 2013. Measurements were taken during school hours on two consecutive days. Indoor PM2.5 concentrations were 12.53-72.38 mu g/m(3) in the summer and 21.85-100.53 mu g/m(3) in winter, while outdoor concentrations were 11.86-181.73 mu g/m(3) in the summer and 21.50-93.07 mu g/m(3) in winter. Indoor/outdoor ratios were 0.17-2.76 in the summer and 0.64-4.49 in winter. PM2.5 levels were higher in indoor microenvironments during the winter, at times exceeding national and international recommendations. Our results demonstrate that indoor air quality Chanaral school microenvironments is closely associated with outdoor air pollution attributable to the nearby mine tailings. Policymakers should enact environmental management strategies to minimize further environmental damage and mitigate the risks that this pollution poses for pediatric health.