Characteristics, source, and health risk assessment of aerosol polyaromatic hydrocarbons in the rural and urban regions of western Saudi Arabia

Abstract

Air quality represents one of the most important parameters determining indoor microclimate and human comfort. Thus, the current study reports a comprehensive study on the dominant sources, organic compositions, and potential health impacts of the polyaromatic hydrocarbons (PAHs) in the atmospheric particle matters (PMs) ranging from 2.5 µm (PM2.5) to 10 µm (PM10) size in the rural and urban regions of western (Jeddah city) Saudi Arabia collected over 1 year between 2014 and 2015. The levels of PAHs in two locations namely Obhur (Urban) and Hada Alsham (Rural) were monitored over 1 year (2014 and 2015) using the gas chromatography coupled mass spectrometry. The level of ƩPAHs in Obhur (819.25 ng/m3) has a significantly high concentration of PAHs compared to Hada Alsham (Rural) (675.26 ng/m3). Indeno(1,2,3-CD)pyrene was the major contributor with an average value of 215.66 ng/m3 followed by benzo[k]fluranthene with a concentration of 150.68 ng/m3, respectively. The major contributors were indeno[1,2,3-cd]pyrene, benzo[k]fluranthene, dibenzo[a,h] anthracene, benzo[g,h]perylene, and benzo[b]fluranthene are the major contributors with contributing percentages of 26.32, 18.39, 9.07, and 8.29%, respectively. The rest of all compounds were below 4%. The highest concentrations of PAHs in Obhur (1836.99 ng/m3) and in Hada Alsham (1107.40 ng/m3) were observed in winter in January 2014. PAHs with 4–6 aromatic ring components are primarily emitted by high temperature combustion. The average values for the BaA/(BaA + Chr) and Flt/(Flt + Pyr) ratios at Obhur were found 0.58 and 0.43 and at Hada Alsham were found 0.63 and 0.38, respectively, indicating that coal/ biomass burning is the major source of PAHs. Hada Alsham (rural area), the transportation system, is a significant contributor to the observed PAHs. These results reflect Saudi Arabia’s traffic load in both rural and urban areas. On road sites, the impact of petroleum combustion and vehicular emissions was also identified. The sum of the incremental lifetime cancer risk (ILCR) for all congeners for infants along the Obhur location was 2.13 × 10−6 and 1.38 × 10−6, respectively. ILCR values were less than 1.0 × 10−4, implying that PAH exposure posed an acceptable potential cancer risk in this study. Various local emission sources contributed more PAHs in many Saudi urban areas, increasing the risk of lung cancer, and the health risk. PAHs have an associated large surface area and are capable of deposition in the respiratory system with high efficiency. The total health risk assessment study also helps in alarming the toxicity at both the locations.