Patterns and disparities in indoor particulate matter levels in selected primary schools in Kigali, Rwanda

Air pollution is a global environmental and public health challenge. There is limited evidence about the air quality in Rwanda, and the concentrations of particulate matter (PM), namely PM_2.5 and PM₁₀ in schools have not been well documented. This study evaluated patterns and disparities in indoor PM levels in selected primary schools in Kigali, Rwanda. The study collected PM_2.5 and PM₁₀ concentrations from six classrooms in six selected primary schools during the regular school study period in the dry season. Data were collected using mobile air sensors (purple air/PA-II-SD air quality) and an observation checklist. A Kruskal-Wallis test was performed to assess the difference in PM_2.5 and PM₁₀ concentrations between the six schools. The post-hoc Mann-Whitney test was used to compare all group pairs. The results indicated a significant difference in both the indoor PM_2.5 concentration (H (5) = 41.01, p < 0.001) and the indoor PM₁₀ concentration (H (5) = 38.5, p < 0.001). The maximum concentration observed was 133.6 μg/m³ for PM_2.5 and 158.5 μg/m³ for PM₁₀. Schools in highly exposed areas tended to have higher concentrations of PM than schools in moderately exposed areas. Specifically, the daily average concentration of PM_2.5 in schools located in highly exposed areas ranged from 39 μg/m³ to 118 μg/m³, while PM₁₀ levels ranged from 44.0 μg/m³ to 126 μg/m³. In contrast, schools in moderately exposed areas had daily PM_2.5 average concentrations ranging from 32.0 μg/m³ to 111.0 μg/m³ and daily PM₁₀ average concentrations ranging from 38.0 μg/m³ to 119 μg/m³. Overall, the recorded values for both PM_2.5 and PM₁₀ in all sampled schools were higher than the World Health Organization air quality guidelines. Indoor air quality is poorer in schools situated in highly exposed areas. This study suggests interventions to improve school air quality for the benefit of school communities.