Air pollution remains a major environmental health burden in rapidly urbanizing Nigerian communities, with limited data on ultrafine particulate matter and associated toxicants. This study assessed PM₁.₀, trace metals, and polycyclic aromatic hydrocarbons (PAHs) across four microenvironments in Isiokpo, Rivers State: a traffic corridor (Site A), a residential–commercial zone (Site B), a market area (Site C), and a peri-urban background site (Site D). PM₁.₀ samples were collected using portable optical particle counters and analyzed for trace metals (Pb, Cd, Ni, V, Fe, Mn, Cu, Zn, Cr) via atomic absorption spectrophotometry, while PAHs were determined using GC–MS. Results showed clear spatial variations driven by traffic and combustion activities. PM₁.₀ concentrations were highest at the traffic corridor (46.2 µg/m³), followed by the market (42.5 µg/m³) and residential, commercial zone (39.8 µg/m³), with the lowest at the background site (28.4 µg/m³). Trace metals mirrored this pattern, with elevated Pb (78.6 ng/m³), Fe (485.7 ng/m³), and Zn (91.4 ng/m³) at Site A, indicating contributions from vehicular brake wear, lubricants, fuel additives, and resuspended dust. Σ₁₆PAHs were highest at Site A (42.7 ng/m³) and lowest at Site D (21.9 ng/m³), while benzo[a]pyrene ranged from 4.33 ng/m³ to 2.04 ng/m³, reflecting urban combustion sources. Overall, vehicular traffic and informal combustion significantly degrade air quality in Isiokpo, increasing exposure to toxic ultrafine particles with carcinogenic and mutagenic potential. The findings underscore the need for integrated air quality management, vehicular emission controls, improved urban planning, and continuous monitoring to safeguard public health.