High-resolution patterns and inequalities in ambient fine particle mass (PM2.5) and black carbon (BC) in the Greater Accra Metropolis, Ghana

Abosede S Alli; Sierra N Clark; Jiayuan Wang; James Bennett; Allison F Hughes; Majid Ezzati; Michael Brauer; James Nimo; Josephine Bedford-Moses; Solomon Baah; Alicia Cavanaugh; Samuel Agyei-Mensah; George Owusu; Jill Baumgartner; Raphael E Arku

doi:10.1016/j.scitotenv.2023.162582

High-resolution patterns and inequalities in ambient fine particle mass (PM_2.5) and black carbon (BC) in the Greater Accra Metropolis, Ghana

Sci Total Environ. 2023 Jun 1:875:162582. doi: 10.1016/j.scitotenv.2023.162582. Epub 2023 Mar 3.

Authors

Affiliations

¹ Department of Environmental Health Sciences, School of Public Health and Health Sciences, University of Massachusetts, Amherst, USA.
² Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, London, UK; MRC Centre for Environment and Health, School of Public Health, Imperial College London, London, UK.
³ Department of Physics, University of Ghana, Accra, Ghana.
⁴ Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, London, UK; MRC Centre for Environment and Health, School of Public Health, Imperial College London, London, UK; Regional Institute for Population Studies, University of Ghana, Accra, Ghana.
⁵ School of Population and Public Health, The University of British Columbia, Vancouver, Canada.
⁶ Department of Geography, McGill University, Montreal, Canada.
⁷ Department of Geography and Resource Development, University of Ghana, Accra, Ghana.
⁸ Institute of Statistical, Social & Economic Research, University of Ghana, Accra, Ghana.
⁹ Institute for Health and Social Policy, McGill University, Montreal, Canada; Department of Epidemiology, Biostatistics, and Occupational Health, McGill University, Montreal, Canada.
¹⁰ Department of Environmental Health Sciences, School of Public Health and Health Sciences, University of Massachusetts, Amherst, USA. Electronic address: rarku@umass.edu.

Abstract

Growing cities in sub-Saharan Africa (SSA) experience high levels of ambient air pollution. However, sparse long-term city-wide air pollution exposure data limits policy mitigation efforts and assessment of the health and climate effects. In the first study of its kind in West Africa, we developed high resolution spatiotemporal land use regression (LUR) models to map fine particulate matter (PM_2.5) and black carbon (BC) concentrations in the Greater Accra Metropolitan Area (GAMA), one of the fastest sprawling metropolises in SSA. We conducted a one-year measurement campaign covering 146 sites and combined these data with geospatial and meteorological predictors to develop separate Harmattan and non-Harmattan season PM_2.5 and BC models at 100 m resolution. The final models were selected with a forward stepwise procedure and performance was evaluated with 10-fold cross-validation. Model predictions were overlayed with the most recent census data to estimate the population distribution of exposure and socioeconomic inequalities in exposure at the census enumeration area level. The fixed effects components of the models explained 48-69 % and 63-71 % of the variance in PM_2.5 and BC concentrations, respectively. Spatial variables related to road traffic and vegetation explained the most variability in the non-Harmattan models, while temporal variables were dominant in the Harmattan models. The entire GAMA population is exposed to PM_2.5 levels above the World Health Organization guideline, including even the Interim Target 3 (15 μg/m³), with the highest exposures in poorer neighborhoods. The models can be used to support air pollution mitigation policies, health, and climate impact assessments. The measurement and modelling approach used in this study can be adapted to other African cities to bridge the air pollution data gap in the region.

Keywords: Air pollution; Black carbon; Fine particulate matter (PM(2.5)); Ghana; Land use regression; Socio-economic status; Sub-Saharan Africa.

MeSH terms

Air Pollutants* / analysis
Air Pollution* / analysis
Carbon / analysis
Environmental Monitoring / methods
Ghana
Particulate Matter / analysis
Soot / analysis

Substances

Air Pollutants
Particulate Matter
Soot
Carbon

Grants and funding

MR/S019669/1/MRC_/Medical Research Council/United Kingdom