Traffic influenced respiratory deposition of particulate polycyclic aromatic hydrocarbons over Dhaka, Bangladesh: regional transport, source apportionment, and risk assessment

Abstract

In Bangladesh, particularly in Dhaka, gridlock in the transportation network is such a typical occurrence that it is critical to have a thorough understanding of the magnitude of carcinogenic airborne toxins like polycyclic aromatic hydrocarbons (PAHs) along the city’s busy streets. In this study, we investigated the airway deposition of PM_2.5- and PM₁₀-bound 16 USEPA (United States Environmental Protection Agency) designated priority PAHs, their potential sources, and associated health risk. The samples were collected over seven high-traffic congestion areas in Dhaka during the monsoon (June–September 2021) and winter (December–February 2022) seasons and analyzed by gas chromatography–mass spectrometry (GC-MS). The winter season exhibited 2.7 and 2.3 times more PM_2.5- and PM₁₀-bound PAHs than the monsoon. The positive matrix factorization (PMF) identified vehicular emissions as the primary PAHs source, followed by biomass and coal combustion. The transboundary incursion of pollutants was predominant during winter, as almost 91% of the trajectories for air mass came from the neighboring country. An adult inhaled 9.70 μg of PAHs per day during winter, of which 1.22 μg entered the alveolar region of the pulmonary tract via PM_2.5 inhalation. The total B[a]P_eq values ranged from 31.0 to 145.1 ng/m3, substantially exceeding the WHO recommended limit (1 ng/m3). Lifetime lung cancer risk (LLRC) and incremental lifetime cancer risk (ILCR) for different age groups revealed that adults had a higher potential cancer risk due to long-term exposure. Overall, prolonged traffic emission increased the risk of lung cancer due to the deposition of carcinogenic B[a]P in the alveolar region (0.72–3.48 ng/h).

Graphical abstract