Size-specific PAHs and Associated Health Risks over a Tropical Urban Metropolis: Role of Long-range Transport and Meteorology

Debajyoti Ray,Abhijit Chatterjee,Sibaji Raha,Abhinandan Ghosh,Sanjay K. Ghosh

doi:10.4209/aaqr.2019.06.0312

Abstract

ABSTRACT The polycyclic aromatic hydrocarbons (PAHs) are considered as an important class of organic pollutants in the urban atmosphere to pose serious health hazards. A comprehensive study was conducted during the dry seasons of 2017–2018 to understand the impacts of local sources, meteorology, boundary layer dynamics, and long-range transport, on the size-specific particulate PAHs (Coarse: 10–2.1 µm; Superfine: 2.1–1.1 µm; Accumulation: 1.1–0.4 µm and Ultrafine: < 0.4 µm). Samples were collected over Kolkata (22.33°N and 88.20°E), a megacity of the lower Indo-Gangetic Plain (IGP). Wintertime distributions of all PAHs were exclusively unimodal with their maximum abundance in accumulation mode, whereas the 4,5 and 6-ring PAHs showed additional coarse mode peaks during post-monsoon and pre-monsoon. The Concentration Weighted Trajectory model has identified the middle IGP and the Eastern Ghats as the potent PAH source regions for the receptor site. Meteorology significantly influenced, in minimizing the contributions of transported PAHs from biomass burning regions of Eastern Ghats during pre-monsoon. On the contrary, meteorology favored the PAHs accumulation from local emissions and long-range transport during winter and post-monsoon. Source apportionment by positive matrix factorization model identified unburned petroleum, incineration, fossil fuel and coal burning as possible major sources of size-specific PAHs. Additionally, based on benzo(a)pyrene equivalent concentrations, the incremental lifetime cancer risk (ILCR) values were estimated for four human age groups. In general, ILCR values were influenced by the accumulation mode, and they were highest for all size ranges during winter. The estimated upper limit of ILCR (9.26 × 10–6) exceeding the carcinogenic benchmark level (1 × 10–6), draws attention towards the adverse impacts of wintertime ultrafine PAHs on human health in Kolkata, where poor air quality is already a major concern.

Highlights

Polycyclic aromatic hydrocarbons (PAH) are unpreventable byproducts of fuel, garbage and biomass combustion
Role of Meteorology and Long-range Transport We showed earlier that atmospheric particulate PAH load over Kolkata is mainly influenced by the boundary layer dynamics as well as ambient meteorology (Ray et al, 2017)
The findings of this study demonstrate that the major sources of PAHs over Kolkata were unburned petroleum, solid waste incineration, petrol, diesel, and coal burning

Summary

Introduction

Polycyclic aromatic hydrocarbons (PAH) are unpreventable byproducts of fuel, garbage and biomass combustion. They are one of the most prominent organic pollutants in the atmosphere with adverse effects on human health and have been ranked within the top ten positions out of 275 hazardous chemicals in the priority list of hazardous substances by the Agency for Toxic Substances and Diseases Registry In addition to molecular weight (i.e., lighter or heavier), the health-damaging potential of the PAHs can be classified based on their accumulation and abundances in different aerosol sizes. The efficiency of the PAHs in reaching to the tracheobronchial or alveolar region of the human respiratory tract and even to the bloodstream (Kajiwara et al, 2007; Monsalve et al, 2013; Velali et al, 2016) enhances as the substrate aerosol size decreases. The population-based cohort studies using a quantitative assessment of PAH exposure revealed intrauterine growth restriction inducing low birth weight (Choi et al, 2012; Polanska et al, 2014), fatal ischemic heart disease (Burstyn et al, 2005), enhanced risk of asthma in children (Al-Daghri et al, 2013; Karimi et al, 2015) and cancer in humans (Boada et al, 2015).

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