Exposure and comparative risk assessment of PAHs in dust from roadside solid surfaces in three semiurban areas of Eastern Nigeria

Abstract

Settled road dust is a sink for polycyclic aromatic hydrocarbons (PAHs), which have hazardous effects on ecosystems. Sampled dust from the solid surfaces of Awka, Ekwulobia, and Rumuodomaya-Ogale, Eastern Nigeria, was collected between December 2019 and March 2020, sieved to obtain uniform particle size, subjected to solvent extraction, and subsequently purified using silica gel/Na₂SO₄ column. The extracts were analyzed using gas chromatography coupled with a flame ionization detector (GC-FID), and the measured PAH concentrations followed the decreasing order: Rumuodomaya-Ogale > Ekwulobia > Awka. Dusts from the Eze-Uzu junction, Ekwulobia roundabout axis, Victoria hospital premises, Eleme junction, and Elelenwo-Akpajo bypass had total PAH concentrations (μg g⁻¹) that ranged from 0.480–0.613, 0.672–0.926, 0.739–1.388, 1.497–7.915, and 1.423–7.037, respectively. The concentration of benzo(a)pyrene equivalent (BaPE) (μg g⁻¹) in dust samples varied across locations as follows: Eze-Uzu junction (0.0047–0.0690), Government house (0.0047–0.0689), Ekwulobia roundabout (0.0720–0.1942), Victoria hospital premises (0.0720–0.2291), Eleme junction (0.2570–1.4930), and Elelenwo-Akpajo bypass (0.2455–1.3934). Benzo(a)pyrene total toxicity equivalence (BaP-TEQ) values in dust of all the sampled locations indicated no cancer risk (CR) to residents, with benzo(a)pyrene as the main contributor. In all cases, CRing values were higher in children than in adults. PAHs in dust indicate contamination via vehicular emissions, waste burning, and incomplete diesel or gasoline combustion. The point source of PAH in the study areas—open waste burning and the explosion of diesel-laden vehicles—should be regulated.