ASSESSMENT OF SOURCE-SPECIFIC TOXICITY WEIGHTING OF FINE PARTICULATE MATTER (PM2.5) IN IKWERRE LOCAL GOVERNMENT AREA OF RIVERS STATE, NIGERIA
Keywords:
Source-specific, toxicity, weighting, particulate matter and health riskAbstract
This study assessed the chemical constituent, sources, and toxicity-related health risks of fine particulate matter (PM₂.₅) in two urban communities: Aluu and Isiokpo, within Ikwerre Local Government Area, Rivers State, Nigeria. PM₂.₅ samples were collected using low-volume air samplers fitted with size-selective PM₂.₅ inlets and pre-weighed quartz-fiber filters during both dry and wet seasons, and subsequently analyzed for particulate mass, trace metals, polycyclic aromatic hydrocarbons (PAHs), and water-soluble ions. The results revealed elevated PM₂.₅ concentrations, with mean values of 46.0 µg/m³ in Aluu and 48.4 µg/m³ in Isiokpo, exceeding the World Health Organization 24-hour guideline and indicating degraded air quality with increased potential for adverse respiratory and cardiovascular effects. The level of trace metals, including Pb (0.10–0.11 µg/m³), Cd (0.005–0.006 µg/m³), and Zn (0.07–0.08 µg/m³), reflected significant contributions from vehicular traffic, industrial activities, and fuel combustion sources.The concentrations of Total polycyclic aromatic hydrocarbons ranged from 0.028 to 0.035 µg/m³, with benzo[a]pyrene levels suggesting the presence of carcinogenic combustion-derived pollutants. Water-soluble ions (SO₄²⁻, NO₃⁻, NH₄⁺, and Cl⁻) occurred at moderate levels, while an ionic imbalance (−44%) indicated anion dominance and the likely presence of unmeasured alkaline cations. Principal Component Analysis (PCA) as a source apportionment tool, identified two dominant components explaining 81.2% of total variance, representing primary combustion-related emissions and secondary inorganic aerosol formation. Toxicity was assessed using toxic equivalency factor (TEF)-based modelling, including toxic equivalent (TEQ) and mutagenic equivalent (MEQ) approaches. The results implied moderate carcinogenic and mutagenic potentials, while non-carcinogenic risks remained below acceptable thresholds. Overall, this study provides important baseline data on PM₂.₅ toxicity in Ikwerre LGA, underscoring the need for continuous air-quality monitoring and targeted emission-control smechanisms in the Niger Delta region.
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