Source Apportionment of Carcinogenic Polycyclic Aromatic Hydrocarbons in Urban Road Dust

Abstract

This study assessed and compared the concentrations of polycyclic aromatic 
hydrocarbons (PAHs) in road dust collected from various zones within Durban 
City, South Africa, including the city centre, residential areas, and industrial 
districts. The investigation aimed not only to quantify PAH levels but also to 
identify their likely sources and assess potential health risks. Measured 
concentrations of total PAHs varied across the different land-use areas: from 
77 to 1488.85 µg·kg⁻¹ in the city centre, up to 2108 µg·kg⁻¹ in residential 
areas, and between 138 and 1409 µg·kg⁻¹ in industrial zones. These variations 
reflect differing emission sources and traffic intensities across the city. To 
determine the origin of PAHs, several molecular diagnostic ratios were 
calculated, including phenanthrene/anthracene (0.03, 0.34, and 0.41), 
benz[a]anthracene/chrysene (0.99 and 0.85), 
benzo[b]fluoranthene/benzo[k]fluoranthene (1.51 and 1.53), and 
benzo[a]pyrene/benzo[e]pyrene (0.98 and 0.92). These ratios, alongside 
results from principal component analysis (PCA), indicated that the dominant 
sources of PAHs were related to the incomplete combustion of petroleum 
products—primarily vehicular emissions from gasoline and diesel engines. 
Furthermore, the study employed toxicity equivalency factors (TEFs) to 
estimate the carcinogenic potential of individual PAH compounds. Health risk 
assessments were conducted using the hazard index (HI) and incremental 
lifetime cancer risk (ILCR) metrics. Results indicated that, while PAHs were 
present in varying concentrations, the associated health risks—both non
carcinogenic and carcinogenic—were within acceptable limits, suggesting that 
road dust PAHs in Durban do not currently pose significant health concerns for 
the urban population.