Distribution of polycyclic aromatic compounds among various phases in an urban road microenvironment of a tropical megacity

Abstract

Quantitative research on characteristics of PAHs prevalent in urban road microenvironments (URM) is vital to emphasize the seriousness of health risks and reduce exposure among commuters and nearby residents, especially in Indian cities where the traffic emissions (exhaust and non-exhaust) are the major contributors to atmospheric particulates in an urban area. The present research investigates the distribution and correlation of Polycyclic Aromatic Hydrocarbons (PAHs) found in various phases (PM₁₀, PM_2.5, resupendable road dust (RRD) and gaseous phase) at urban road microenvironment (URM) using Two-way ANOVA analysis. The sources and health risk associated with PAH exposure is also estimated. PM₁₀ and PM_2.5 samples were collected on the kerbside using high-volume samplers, and RRD was collected at eight contrasting locations using EPA AP-42 methodology. A total of 64 PAHs were analyzed using GC-MS and incremented life cancer risk (ILCR) was estimated for children and adults by calculating toxicity equivalents using three different approaches. Average PAHs concentration varied from 75 to 175 μg/g for PM₁₀, 30–80 μg/g for PM_2.5, and 01–03 μg/g for RRD. Gaseous phase ∑PAH was found to be in the range of 0.5–2.75 μg/m³. It was found that high molecular weight PAHs such as Coronene, Pyrene, Indeno(1,2,3-c,d)pyrene and Benzo ghi perylene were the major contributing compounds in the urban road microenvironment. A strong correlation between PAHs bound to PM₁₀ and RRD was found at all the sampling locations. Further, ILCRs of total cancer risk due to inhalation of PM were in the range of 1.61E-05 to 2.05E-03. However, the risk due to exposure to RRD was within an acceptable risk of 1E-06. The current study highlights the scientific backing for RRD-specific regulations, which are currently absent, to control non-exhaust emissions in India.