Title : Geochemical characterisation, health risk estimates and source apportionment of fine inhalable particles (PM2.5) in informal and low-income housing of the Western Cape, South Africa
Abstract:
Low socioeconomic conditions in economically disadvantaged settlements of the Western Cape have led to overcrowded living environments with implications for indoor air quality. This study investigated the chemical composition and sources of fine particulate matter (PM2.5) from November 2022 to March 2024 across 18 locations and 108 households. Indoor PM2.5 was monitored using low-cost PurpleAir sensors alongside Ultrasonic Personal Air Sampler (UPAS) equipped with polytetrafluoroethylene (PTFE) membrane filters for geochemical analysis by inductively coupled plasma mass spectrometry (ICP-MS) and particle morphological analyses by scanning electron microscopy (SEM). Median levels of twenty-four-hour PM2.5 concentrations were notably higher in winter (50.3 µg/m3) than in summer (30.7 µg/m³) and ranged from 27.0 µg/m³ to 94.6 µg/m³ across the different sites. Diurnal peaks were observed between 15:00 and 20:00. The concentrations of Al, Fe and Zn were higher among the quantified elements in the PM2.5, while potentially toxic elements including Pb, As, Se, Cd, Cr, Cu and V were also detected. The calculated hazard index and carcinogenic risk indicated low overall health risks. Among the detected elements, As and Cd contributed most to the hazard index whereas Zn dominated the carcinogenic risk. Most of the PM2.5 were irregular in shape (55%), semi rounded and cubic (23%) or rounded (13%). Mineral dust particles contributed 30% to the total PM2.5. The calculated enrichment factors for Zn, Pb, As, Cd, Cu, Ba, Cr, and Ni suggested a strong anthropogenic influence on PM2.5. Positive Matrix Factorisation identified mixed sources; traffic emissions and solid waste burning (58%), resuspended dust (24%), and chromium plating/metal processing (18%). These findings emphasise that strengthened combustion regulations, regionally aligned emission standards and greater awareness of waste burning may serve to reduce indoor PM2.5 and associated health risks.
Keywords: Indoor air pollution; Particulate morphology; toxic metals; Health risk
