Particulate matter monitoring and source apportionment inside and outside schools in a Global South metropolis

Abstract

Globally, particulate matter (PM) air pollution is a significant threat to public health. The city of Port Harcourt, Nigeria, is heavily impacted by PM pollution through both natural and anthropogenic sources, including desert dust, vehicular emissions and gas flaring from crude oil processing and refining. Children are especially vulnerable to air pollution, and since they spend a large proportion of their time at school, this microenvironment is critical for their total air pollution exposure. Using low-cost sensors, PM were monitored in three schools in Port Harcourt. The PM_2.5 and PM₁₀ concentrations were, in almost all cases, significantly higher during the dry season compared to the rainy season, up to a factor of 3. Both PM_2.5 and PM₁₀ concentrations were also found to be greater than the annual WHO recommendations throughout the campaign, often exceeding the 24 hour recommendations, in some cases more than 5 times, for both the dry and rainy seasons. Indoor PM₁, PM_2.5 and PM₁₀ concentrations during the school day were significantly higher than outdoor concentrations highlighting the influence of indoor PM sources, in addition to the infiltration of outdoor sources. Source apportionment revealed consistent source patterns across both seasons, showing that outdoor emissions overwhelmingly dominated indoor air quality. Outdoor sources accounted for more than 95% of indoor PM_2.5 and for more than 60% of the indoor PM₁₀. The high PM level exposure during the dry season was significantly influenced by the Harmattan desert dust both inside and outside the schools. In the rainy season, local anthropogenic sources played a more significant role in the absence of the Harmattan effect. These results underscore the urgent need for targeted mitigation strategies within school environments and their surrounding communities to protect children's health and reduce the long-term burden of air pollution in Port Harcourt and other similar urban settings.