Developing a Black Carbon-Substituted Multimedia Model for Simulating the PAH Distributions in Urban Environments

Atmospheric benzo[a]pyrene in the Yangtze River Delta, China: pollution level and lung cancer risk in 2016 and future predictions

The Yangtze River Delta (YRD) has undergone widespread polycyclic aromatic hydrocarbon (PAH) pollution. In this study, we simulated the spatial distribution of atmospheric benzo[a]pyrene (BaP, the most carcinogenic PAH) in the YRD in 2016 and 2030 under different emission scenarios using a 3-D atmospheric transport model and evaluated the lung cancer risks posed by BaP during the study years. The purpose of this study is to suggest targeted policy recommendations for policy-makers to mitigate BaP pollution through numerical simulation. Our results showed that the average BaP concentration in the YRD was 0.30 ng/m3 in 2016; however, a significant spatial variation was observed, with the highest BaP concentration in Shanghai (0.59 ng/m3). The population-weighted incremental lifetime lung cancer risk (PILCR) was 6.67 × 10-6 in 2016, whereas it ranged from 2.70 × 10-6 to 1.05 × 10-5 in 2030 under the five emission scenarios. A higher future population density in the YRD region could increase lung cancer risk. In all scenarios, Shanghai had the highest number of lung cancer cases (range: 208-476). The results suggest that BaP pollution could be effectively improved through the synergistic effect of reducing activity levels and improving technology. Finally, we provide specific suggested pollution control strategies (e.g., accelerating the use of clean energy in rural areas) for atmospheric BaP in the YRD.

Modeling multimedia fate and health risk assessment of polycyclic aromatic hydrocarbons (PAHs) in the coastal regions of the Bohai and Yellow Seas

Using an improved multimedia fate model, this study simulated the spatial distributions, partitioning behaviors, and mass exchanges of PAH₁₆ (16 species with priority by the USEPA) in multiple environmental compartments in the coastal regions of the Bohai and Yellow Seas, Northern China. The model predictions generally matched well with the measured results, as the deviations of most points were within one order of magnitude in the air, freshwater, and 3 soil compartments. The estimated concentrations of ΣPAH₁₆ in the northern part were higher than those in the southern part, which was consistent with the emissions of each part. Approximately 97.6% of the ΣPAH₁₆ mass was distributed in soils; therefore, soils served as the dominant sink of PAH₁₆. The estimated net flux of ΣPAH₁₆ from air to soil ranged from 0.4 to 10.7 mg/m²/year (an average of 3.2 mg/m²/year), and the estimated flux of deposition from air to soil fell in the range of 0.4-10.8 mg/m²/year (an average of 3.2 mg/m²/year), which served as the dominant process at the air-soil interface. The estimated net flux of ΣPAH₁₆ from air to freshwater ranged from -15.3 to 9.4 mg/m²/year (an average of -0.3 mg/m²/year), and the reversed volatilization flux from freshwater to air ranged from 0.01 to 21.1 mg/m²/year (an average of 3.7 mg/m^2/year). This situation indicated notable spatial variations and volatilization as the main process affecting the direction of net flux at the air-freshwater interface. Deterministic risk assessment and probabilistic risk assessment were conducted. The overall health risks of the studied regions were acceptable, while the excess lifetime cancer risk (ELCR) by air inhalation was greater than that by soil ingestion. CAPSULE: Multimedia fate model-predicted distributions and compositions of PAH₁₆ in different compartments, compartmental exchange fluxes and directions, and deterministic and probabilistic ELCR via different exposure pathways were assessed.

Spatially resolved environmental fate models: A review

Spatially resolved environmental models are important tools to introduce and highlight the spatial variability of the real world into modeling. Although various spatial models have been developed so far, yet the development and evaluation of these models remain a challenging task due to several difficulties related to model setup, computational cost, and obtaining high-resolution input data (e.g., monitoring and emission data). For example, atmospheric transport models can be used when high resolution predicted concentrations in atmospheric compartments are required, while spatial multimedia fate models may be preferred for regulatory risk assessment, life cycle impact assessment of chemicals, or when the partitioning of chemical substances in a multimedia environment is considered. The goal of this paper is to review and compare different spatially resolved environmental models, according to their spatial, temporal and chemical domains, with a closer insight into spatial multimedia fate models, to achieve a better understanding of their strengths and limitations. This review also points out several requirements for further improvement of existing models as well as for their integration.

Application of a fugacity model to estimate emissions and environmental fate of ship stack PAHs in Shanghai, China

The understandings of environmental activities and regional inventory of ship stack PAHs are very limited in Shanghai due, in part, to the lack of source-segregated analysis. To address this, measured PAHs in organic film on ship surfaces were employed to reconstruct concentrations in various compartments through a fugacity model to investigate the level, transport, fate and annual emission of ship stack PAHs in Shanghai. The results revealed that ship stack PAHs results in 11.2-181 ng L^-1 and 71.0-1710 ng g^-1 in water and sediment of Shanghai, respectively. After being released into air, ship stack PAHs mainly concentrated in organic films and sediments while sunk in water and sediment. Crucial mass transfer pathways include deposition of airborne and sediment PAHs. The mass loss of ship stack PAHs was primarily through air advection, followed by degradation in sediment. The ship emissions (53.7 tons annually) accounted for approximate one tenth of the regional total in Shanghai (in 2017). Additionally, shipping was estimated to release 127 tons of PAHs annually into the Shanghai section of Yangtze River. Our results suggest our fugacity-based approach can be used to estimate the regional emissions and inventory of ship stack PAHs in the surrounding environment.

NOD-like receptor signaling pathway activation: A potential mechanism underlying negative effects of benzo(α)pyrene on zebrafish

Benzo(α)pyrene (BaP) is one of typical polycyclic aromatic hydrocarbons (PAHs) in aquatic environments and has been shown to cause toxic effects to aquatic animals. Although the negative effects of BaP have been investigated, the potential toxic mechanisms remain uncharacterized. To explore the potential mechanisms mediating the toxic effects of BaP, zebrafish (Danio rerio) were exposed to BaP for 15 days and the toxic effects of BaP in zebrafish liver were investigated using physiological and transcriptomic analyses. After 15-day BaP exposure, zebrafish liver exhibited abnormalities including increased cytoplasmic vacuolation, inflammatory cell infiltration, swelled nuclei and irregular pigmentation. BaP exposure also induced oxidative stress to the liver of zebrafish. Transcriptomic profiles revealed 5129 differentially expressed genes (DEGs) after 15-days of BaP exposure, and the vast majority of DEGs were up-regulated under BaP treatment. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses suggest that genes related to immune response were significantly dysregulated. Furthermore, the nucleotide-binding, oligomerization domain (NOD)-like receptor signaling pathway was significantly enriched and most of the genes in this pathway exhibited enhanced expression after BaP exposure. These results partially explained the mechanisms underlying the toxic effects of BaP on zebrafish liver. In conclusion, BaP has the potential to induce physiological responses in zebrafish liver through altering associated genes.

Exposure to polycyclic aromatic hydrocarbons (PAHs) in people living in urban and rural areas as revealed by hair analysis

Some polycyclic aromatic hydrocarbons (PAHs) are carcinogenic and mutagenic to humans. However, little is known about PAH exposure to people living in urban and suburban areas through comparative studies. Some studies have indicated that human hair can be used as a noninvasive biomarker of PAH exposure. Therefore, we collected hair samples from 66 volunteers from Nanjing and Ningbo, China, to detect PAH concentrations in this work. The highest levels in the hair samples were found in phenanthrene > anthracene > naphthalene among the parent PAHs. Sixteen parent PAHs showed higher concentrations in the samples from Nanjing than in the samples from Ningbo. Significantly higher levels of some PAHs were observed in male hair than in female hair in Nanjing, and in hair from smokers than in hair from non-smokers in both Nanjing and Ningbo. In addition, there was a significant effect of the age on the concentration of low-molecular-weight PAHs and ∑PAHs in human hair in both Nanjing and Ningbo. Studying the inter-chemical associations between these PAHs indicated similarities and differences between Nanjing and Ningbo.