Statistical analysis, source apportionment, and toxicity of particulate- and gaseous-phase PAHs in the urban atmosphere

Exposures to polycyclic aromatic hydrocarbons among adults and children: Contributions from multiple pathways and sources

Polycyclic aromatic hydrocarbons (PAHs) exist ubiquitously in the natural environment; however, studies seldom evaluate health risks from aggregate exposures to PAHs from multiple environmental media. This study aimed to estimate the doses and risks of 16 priority PAHs in soil and air for both children and adults and quantify their contributors. Soil and ambient air samples were collected at 50 and 8 sites, respectively, in Memphis, Tennessee, USA. Grab soil samples were taken from the upper 2 inches of the soil and air samples were collected every 12 days for over one year. The sum concentration of 16 PAHs (ΣPAH) averaged 7.6 ± 15.0 mg/kg (range 1.5-98.8 mg/kg) in soil and 73.6 ± 25.3 ng/m3 (range 47.0-121.2 ng/m3) in air. Source apportionment identified five broad sources of soil and airborne PAHs: vehicle emissions, petrogenic sources, coal combustion, emissions from coal tar, and natural gas combustion. For children aged 3-6 years, the average daily dose (ADD) of ΣPAH was 58.3 ng/kg-day, with 66%, 27%, and 7% from inhalation, ingestion, and dermal contact, respectively. The lifetime cancer risk from all PAHs was 0.42 × 10-6, with ingestion being the primary contributor (75%). For adults aged 21-30 years, the ADD of ΣPAH was 46.2 ng/kg-day, with contributions of 67%, 31%, and 2% from dermal contact, inhalation, and ingestion, respectively. The lifetime cancer risk from all PAHs was 0.55 × 10-6, mainly due to dermal contact (96%). Vehicle emissions, petrogenic sources, and coal combustion together contributed over 85% of the cancer risk. The findings provided bases for designing effective exposure controls, including source control and personal behavioral changes.

Source identification of polycyclic aromatic hydrocarbons (PAHs) in river sediments within a hilly agricultural watershed of Southwestern China: an integrated study based on Pb isotopes and PMF method

Polycyclic aromatic hydrocarbons (PAHs) in sediments represent a pervasive environmental issue that poses significant ecological risks. This study employed a combination of geographic information systems, diagnostic ratios, correlation analysis, Pb isotope ratios, and positive matrix factorization (PMF) to elucidate the potential sources of 16 priority PAHs in river sediments from a hilly agricultural watershed in Southwestern China. The results indicated that PAHs concentrations ranged from 55.9 to 6083.5 ng/g, with a mean value of 1582.1 ± 1528.9 ng/g, reflecting high levels of contamination throughout the watershed. The predominant class of PAHs identified was high molecular weight (HMW) PAHs. Diagnostic ratios and correlation analysis suggested that the presence of PHAs is likely attributed primarily to emissions from industrial dust and combustion of coal and petroleum. Furthermore, correlation analysis revealed a significant association between Pb and PAHs, indicating potential shared sources for both pollutants. Additionally, Pb isotopic analysis demonstrated that aerosols may be the primary contributor to Pb accumulation within this environment. Given the similarity in origins between Pb and PAHs, it can be inferred that PAHs predominantly originate from aerosols associated with coal combustion, industrial dust emissions, and vehicle exhaust. This inference is further supported by PMF results which yielded consistent findings with those derived from Pb isotopes analysis. Moreover, PMF estimated three major sources contributing 57.63%, 23.57%, and 18.80%, respectively. These findings provide novel insights into identifying the sources of PAHs in river sediments within hilly agricultural watersheds in Southwest China, thereby establishing a scientific foundation for enhancing environmental quality in agricultural regions.

Leaf ecological traits (morphology and gas exchange) and polycyclic aromatic hydrocarbons concentrations in shrubs and trees: A meta-analysis approach

The leaves of trees and shrubs can capture atmospheric pollutants such as polycyclic aromatic hydrocarbons (PAHs), and the capacity of uptake depends on the leaf traits. Although numerous studies have measured PAH concentrations in leaves of woody plants and the variability in leaf traits, few have investigated the relationship between these factors. We conducted a literature review to summarize the available information on this topic and found that five types of leaf traits have been studied, with those associated with leaf morphology and gas exchange being the most common. However, the results of the studies are often contradictory. To address these discrepancies, we conducted a meta-analysis to examine how PAH uptake by woody species is affected by leaf ecological traits associated with morphology (leaf area, specific leaf area [SLA], leaf thickness and leaf width/length ratio [W/L]) and with gas exchange (stomatal conductance, leaf carbon isotopic signature [δ13C] and stomatal density). The meta-analysis included studies involving at least two different species with comparable PAH concentrations. Many of the studies did not examine the relationship between ecological traits and PAH concentration, and those that did often involve different traits. We therefore used the TRY Plant Trait Database data as the standard source of trait data. Relationships were analyzed by determining differences regarding PAHs and traits and calculating Spearman correlations and their significance. The leaf morphology traits were more closely correlated with PAH concentrations than the gas exchange traits. Thus, morphological traits such as SLA and leaf area can be considered significant predictors of PAH uptake, especially for particulate-associated PAHs. Gas exchange traits showed less consistent correlations, indicating the complexity of factors influencing PAH uptake in leaves. This study highlights the importance of considering multiple leaf traits in order to better understand and predict PAH uptake in woody plants.

Impact of Atmospheric Conditions and Source Identification of Gaseous Polycyclic Aromatic Hydrocarbons (PAHs) during a Smoke Haze Period in Upper Southeast Asia

Gaseous polycyclic aromatic hydrocarbons were measured in northern Thailand. No previous studies have provided data on gaseous PAHs until now, so this study determined the gaseous PAHs during two sampling periods for comparison, and then they were used to assess the correlation with meteorological conditions, other pollutants, and their sources. The total concentrations of 8-PAHs (i.e., NAP, ACY, ACE, FLU, PHE, ANT, FLA, and PYR) were 125 ± 22 ng m-3 and 111 ± 21 ng m-3, with NAP being the most pronounced at 67 ± 18 ng m-3 and 56 ± 17 ng m-3, for morning and afternoon, respectively. High temperatures increase the concentrations of four-ring PAHs, whereas humidity and pressure increase the concentrations of two- and three-ring PAHs. Moreover, gaseous PAHs were estimated to contain more toxic derivatives such as nitro-PAH, which ranged from 0.02 ng m-3 (8-Nitrofluoranthene) to 10.46 ng m-3 (1-Nitronaphthalene). Therefore, they could be one of the causes of local people's health problems that have not been reported previously. Strong correlations of gaseous PAHs with ozone indicated that photochemical oxidation influenced four-ring PAHs. According to the Pearson correlation, diagnostic ratios, and principal component analysis, mixed sources including coal combustion, biomass burning, and vehicle emissions were the main sources of these pollutants.

Substantial Changes in Selected Volatile Organic Compounds (VOCs) and Associations with Health Risk Assessments in Industrial Areas during the COVID-19 Pandemic

During the COVID-19 pandemic, governments in many countries worldwide, including India, imposed several restriction measures, including lockdowns, to prevent the spread of the infection. COVID-19 lockdowns led to a reduction in gaseous and particulate pollutants in ambient air. In the present study, we investigated the substantial changes in selected volatile organic compounds (VOCs) after the outbreak of the coronavirus pandemic and associations with health risk assessments in industrial areas. VOC data from 1 January 2019 to 31 December 2021 were collected from the Central Pollution Control Board (CPCB) website, to identify percentage changes in VOC levels before, during, and after COVID-19. The mean TVOC levels at all monitoring stations were 47.22 ± 30.15, 37.19 ± 37.19, and 32.81 ± 32.81 µg/m³ for 2019, 2020, and 2021, respectively. As a result, the TVOC levels gradually declined in consecutive years due to the pandemic in India. The mean TVOC levels at all monitoring stations declined from 9 to 61% during the pandemic period as compared with the pre-pandemic period. In the current study, the T/B ratio values ranged from 2.16 (PG) to 26.38 (NL), which indicated that the major pollutant contributors were traffic and non-traffic sources during the pre-pandemic period. The present findings indicated that TVOC levels had positive but low correlations with SR, BP, RF, and WD, with correlation coefficients (r) of 0.034, 0.118, 0.012, and 0.007, respectively, whereas negative correlations were observed with AT and WS, with correlation coefficients (r) of -0.168 and -0.150, respectively. The lifetime cancer risk (LCR) value for benzene was reported to be higher in children, followed by females and males, for the pre-pandemic, pandemic, and post-pandemic periods. A nationwide scale-up of this study's findings might be useful in formulating future air pollution reduction policies associated with a reduction in health risk factors. Furthermore, the present study provides baseline data for future studies on the impacts of anthropogenic activities on the air quality of a region.