An integrated approach for generating rich city-wide air pollution data in growing Sub-Saharan African cities: Implementing transferable protocol in Kigali, Rwanda

Cities in sub-Saharan Africa (SSA) are undergoing significant economic and urban expansion. The rapid urban growth is shaping land use, housing, transportation, and energy for household and commercial use. Consequently, air pollution from diverse local and regional sources and with complex space-time patterns has emerged as a major environmental health concern for cities in SSA. Yet, limited city-scale data are a barrier to climate and health impact assessment as well as policy formulation and evaluation to reduce air pollution.   We are implementing and testing the transferability of Pathways to Equitable Health Cities measurement protocol for Accra in Kigali, Rwanda. The protocol is designed to generate rich environmental pollution data in SSA cities. Both Accra and Kigali are representative of the rapid urbanization and economic transformation that are happening across SSA. We have assembled and integrated multiple low-cost, low-power, lightweight sensors that have been validated in prior studies to measure integrated and real-time fine particulate matter (PM2.5), black carbon (BC), and oxides of nitrogen (NO2 and NO) concentrations at city-scale. Initiated in November 2022, our year-long measurement campaign utilizes a network and combination of ‘fixed’ (n=10) and ‘rotating’ (n =120) monitoring sites. The sites represent variety of land uses and emission sources, including background, road traffic, commercial, industrial and residential areas, and neighbourhood socioeconomic classes. The fixed sites are monitored continuously for one year to capture temporal (annual and seasonal) patterns, whereas the rotating sites are monitored for one week (in groups of four per week) to capture spatial variations in the pollutant concentrations. In addition to the air pollutants, we are also collecting data on environmental noise and weather variables (i.e. temperature, relative humidity and wind speed/direction) to aid in the analyses. The Kigali initiative is being implemented in partnership with AIMS-Rwanda and the Rwanda Environment Management Authority (REMA) to promote capacity building within the government.   Planned analyses involve the use state-of-the-art models, including spatial statistics, deep/machine learning approaches, to capture highly resolved temporal and spatial variations as well as socioeconomic inequalities in pollution levels across Kigali city and to identify sources and their relative contributions. The data form the basis of future climate change and air pollution forecasting and health impact assessment as well as policy evaluation and emission reduction scenarios in the city.