Characterization of Indoor PM₂.₅ and Gas- and Particle-Phase Polycyclic Aromatic Hydrocarbons in Selected Households in Benin City, Nigeria
Keywords:
indoor air pollution; PM₂.₅; polycyclic aromatic hydrocarbons; household combustion; gasoline generators; cooking fuels; gas-particle partitioning; Benin City; NigeriaAbstract
Fine particulate matter (PM₂.₅) and polycyclic aromatic hydrocarbons (PAHs) can be elevated during indoor combustion, yet simultaneous measurements of particulate matter and gas- and particle-phase PAHs remain limited in Nigerian residential environments. This study characterized indoor PM₂.₅ and 17 PAHs in four selected households in Benin City, Edo State, Nigeria. Sampling was conducted in July and September 2026 across UGB1, UGB2, GRA1 and GRA2. PM₂.₅ was measured in occupied residences, while particle-bound and vapour-phase PAHs were collected using glass-fibre filters and polyurethane foam, respectively, and analysed by gas chromatography with flame-ionization detection (GC-FID). The reported sampling-period mean PM₂.₅ concentrations were 72.00 ± 14.53, 120.60 ± 25.58, 27.67 ± 0.58 and 40.67 ± 23.02 µg m⁻³ for UGB1, UGB2, GRA1 and GRA2, respectively. The observed concentrations were numerically higher than the WHO 2021 24-h PM₂.₅ guideline value of 15 µg m⁻³; however, they should not be interpreted as formal 24-h guideline exceedances because the sampling protocol did not establish standardized 24-h averages. The detected ΣPAH concentrations were 26.71, 35.87, 10.56 and 30.29 ng m⁻³ for UGB1, UGB2, GRA1 and GRA2, respectively. UGB1 had a greater detected vapour-phase contribution, whereas particle-phase PAHs accounted for the larger proportion of detected ΣPAHs in UGB2, GRA1 and GRA2. Benzo(a)anthracene recorded the highest individual detected concentration, reaching 12.63 ng m⁻³ in the GRA2 particle phase. Household fuel use and generator operation provided useful contextual information for interpreting the observed PAH profiles, although the small number of independent households and absence of paired outdoor measurements limit definitive source attribution. The findings provide preliminary evidence of substantial variation in indoor PM₂.₅ and gas- and particle-phase PAH profiles among selected households in Benin City and support the need for larger paired indoor–outdoor investigations.
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