Concentration, source identification and risk assessment of atmospheric polycyclic aromatic hydrocarbons at a kindergarten school in Kigali, Rwanda

• We characterize PAHs at Kindergarten School in Sub-Saharan Africa. • PAHs exceeded the levels reported in kindergarten schools in high-income countries. • Wood burning and diesel traffic emissions were the primary sources of PAHs. • Cancer risk level significantly exceeded the WHO safe limit. • Policies to address air quality at African schools are urgently required. Africa has the world’s youngest population, with 40 % aged between 0 and 15 years, and it remains the region most affected by air pollution. In many African cities, kindergarten schools are often located in high-density and polluted urban environments with high levels of hazardous pollutants, including atmospheric polycyclic aromatic hydrocarbons (PAHs). Compared to the rest of the world, limited studies have quantified the exposure to and associated health risks of PAHs in schools in Africa. This study first characterizes and identifies sources of atmospheric PAH and assesses the health risks at a kindergarten school in Rwanda. Fine particulate matter (PM 2.5 ) was collected during the dry and wet seasons using a mini-volume air sampler, and 16 PAHs were characterized using gas chromatography. The total mean concentration of 16 PAHs was higher in the dry season (52.7 ± 21.9 ng/m 3 ) than in the wet season (49.5 ± 14.7 ng/m 3 ) and exceeded the levels reported in kindergarten schools in high-income countries. Source analysis using PAH diagnostic ratios and correlation analysis of PAHs with black carbon from biomass burning and fossil fuel showed that wood burning for cooking fuel and diesel traffic emissions were the main sources of PAHs at the kindergarten school. The estimated cancer risk level significantly exceeded the World Health Organization’s safe limit and indicates that children at kindergarten in Rwanda are exposed to high levels of toxic PAHs. Immediate attention is required, and schools should consider implementing policies and interventions to reduce children’s exposure to air pollution at kindergarten schools.