Size Distribution of Chlorinated Polycyclic Aromatic Hydrocarbons in Atmospheric Particles

Approaches to the source evaluation of chlorinated polycyclic aromatic hydrocarbons in fine particles

Chlorinated polycyclic aromatic hydrocarbons (ClPAHs) have been recognized as novel hazardous pollutants; however, the dominant sources remain unclear. This study investigates the occurrences of ClPAHs in five stages of size-segregated particles collected from an urban site and evaluates the sources and factors affecting the concentrations using organic and inorganic source tracers. ClPAHs are the most frequently detected in the finest particle fraction (less than 1.1 µm; PM1.1), similar to polycyclic aromatic hydrocarbons (PAHs), hopanes, and levoglucosan (LEV). The concentrations of total ClPAHs in PM1.1 shows a significant correlation (p < 0.05) with those of total PAHs and specific hopanes but not to LEV and biogenic fatty acids; this suggests that ClPAHs dominantly originate from industrial activities and vehicular emissions. Heatmap analysis, including source tracers, is used to categorize the possible sources of ClPAHs into three types: ClPAH-specific sources, local industrial activities and vehicular emissions, and remote industrial activities. Furthermore, correlation network analysis is used to clarify the relationships between the pollutants.

Seasonal variation and size distribution of inorganic and carbonaceous components, source identification of size-fractioned urban air particles in Kuala Lumpur, Malaysia

This study aims to determine the inorganic and carbonaceous components depending on the seasonal variation and size distribution of urban air particles in Kuala Lumpur. Different fractions of particulate matter (PM) were measured using a Nanosampler from 17 February 2017 until 27 November 2017. The water-soluble inorganic ions (WSIIs) and carbonaceous components in all samples were analysed using ion chromatography and carbon analyser thermal/optical reflectance, respectively. Total PM concentration reached its peak during the southwest (SW) season (70.99 ± 6.04 μg/m³), and the greatest accumulation were observed at PM_0.5-1.0 (22%-30%, 9.55 ± 1.03 μg/m³) and PM_2.5-10 (22%-25%, 10.34 ± 0.81 μg/m³). SO₄^2-, NO₃^- and NH₄⁺ were major contributors of WSIIs, and their formation was favoured mainly during SW season (80.5% of total ions). PM_0.5-1.0 and PM_2.5-10 exhibited the highest percentage of WSII size distribution, accounted for 28.4% and 13.5% of the total mass, respectively. The average contribution of carbonaceous species (OC + EC) to total carbonaceous concentrations were higher in PM_0.5-1.0 (35.2%) and PM_2.5-10 (26.6%). Ultrafine particles (PM_<0.1) consistently indicated that the sources were from vehicle emission while the SW season was constantly dominated by biomass burning sources. Using the positive matrix factorization (PMF) model, secondary inorganic aerosol and biomass burning (30.3%) was known as a significant source of overall PM. As a conclusion, ratio and source apportionment indicate the mixture of biomass burning, secondary inorganic aerosols and motor vehicle contributed to the size-segregated PM and seasonal variation of inorganic and carbonaceous components of urban air particles.

Occurrence, potential source, and cancer risk of PM2.5-bound polycyclic aromatic hydrocarbons and their halogenated derivatives in Shizuoka, Japan, and Dhaka, Bangladesh

Because of their unintentional formation and low vapor pressure, polycyclic aromatic hydrocarbons (PAHs) and their halogenated derivatives (XPAHs) in the atmosphere are distributed primarily to aerosolized particles with an aerodynamic diameter less than 2.5 μm (PM_2.5). However, no information is available regarding the occurrence of PM_2.5-bound PAHs and XPAHs in Bangladesh, one of the most highly PM_2.5-polluted regions worldwide. In this study, we investigated the occurrence of PM_2.5-bound PAHs and XPAHs in the atmospheres of Dhaka in Bangladesh and Shizuoka in Japan (as a reference) and estimated their incremental lifetime cancer risks (ILCRs). In addition, we statistically estimated the potential sources of PM_2.5-bound PAHs and XPAHs by using principal component analysis and positive matrix factorization. The median concentration of total PM_2.5-bound PAHs and XPAHs in Bangladesh was 24.2 times that in Japan. The estimated potential sources of PAHs clearly differed between Japan and Bangladesh, whereas those of XPAHs were largely (>80%) unknown in both countries. The median ILCR in Bangladesh was 2.81 × 10^-3, which greatly exceeded the upper limit of acceptable risk (10^-4). These results indicate that comprehensive monitoring and control of atmospheric PM_2.5-bound PAHs and XPAHs are needed urgently, especially in highly polluted countries.

Characteristics of chlorinated and brominated polycyclic aromatic hydrocarbons in the Pearl River Estuary

The spatial distribution of halogenated polycyclic aromatic hydrocarbons (H-PAHs) (8 chlorinated PAHs (Cl-PAHs) and 9 brominated PAHs (Br-PAHs)), in the Pearl River Estuary (PRE) was investigated. The total concentrations of 17H-PAHs in sediment samples were ranged from 1.4 ng g^-1 to 40.9 ng g^-1 with an average concentration of 14.7 ng g^-1. The average H-PAH concentration in the suspended particulate matters (SPMs) (475.6 ng g^-1) was 30 times higher than that in the sediments (14.7 ng g^-1), and H-PAHs were rarely detected in the aqueous phase. The dominant H-PAHs in sediments were 9,10-dichloroanthracene (31.2%) and 9-chlorophenanthrene (32.0%); 2/9-chlorofluorene (27.4%) was prominent in surface SPMs, while no significant dominant congeners were found in bottom SPMs. Principal component analysis showed that the congener profiles of H-PAHs in sediments were different from those of SPMs especially for surface SPM samples which might be caused by point source discharges of H-PAHs from the coast of the PRE. In general, riverine inputs were the major source of H-PAHs in the PRE, and SPMs were important carriers for transporting H-PAHs. Diagnostic analyses showed that the H-PAHs might originate from waste incineration and automobile emissions in the Pearl River Delta (PRD).

PBDE emission from E-wastes during the pyrolytic process: Emission factor, compositional profile, size distribution, and gas-particle partitioning

Polybrominated diphenyl ether (PBDE) pollution in E-waste recycling areas has garnered great concern by scientists, the government and the public. In the current study, two typical kinds of E-wastes (printed wiring boards and plastic casings of household or office appliances) were selected to investigate the emission behaviors of individual PBDEs during the pyrolysis process. Emission factors (EFs), compositional profile, particle size distribution and gas-particle partitioning of PBDEs were explored. The mean EF values of the total PBDEs were determined at 8.1 ± 4.6 μg/g and 10.4 ± 11.3 μg/g for printed wiring boards and plastic casings, respectively. Significantly positive correlations were observed between EFs and original addition contents of PBDEs. BDE209 was the most abundant in the E-waste materials, while lowly brominated and highly brominated components (excluding BDE209) were predominant in the exhaust fumes. The distribution of total PBDEs on different particle sizes was characterized by a concentration of finer particles with an aerodynamic diameter between 0.4 μm and 2.1 μm and followed by less than 0.4 μm. Similarly, the distribution of individual species was dominated by finer particles. Most of the freshly emitted PBDEs (via pyrolysis) were liable to exist in the particulate phase with respect to the gaseous phase, particularly for finer particles. In addition, a linear relationship between the partitioning coefficient (K_P) and the subcooled liquid vapor pressure (P_L⁰) of the different components indicated non-equilibrium gas-particle partitioning during the pyrolysis process and suggested that absorption by particulate organic carbon, rather than surface adsorption, governed gas-particle partitioning.

Particulate matter 2.5 regulates lipid synthesis and inflammatory cytokine production in human SZ95 sebocytes

A large body of evidence indicates that particulate matter (PM)2.5 is associated with various negative effects on human health. However, the impact and molecular mechanism of PM2.5 on the skin have not been elucidated. Therefore, the present study aimed to investigate the effects of two types of PM2.5 [water-soluble extracts (W-PM2.5) and non-water-soluble extracts (NW-PM2.5)] on cell proliferation, cell cycle progression, lipid synthesis, and inflammatory cytokine production of human SZ95 sebocytes. The results demonstrated that NW-PM2.5 and W-PM2.5 exposure dose-dependently inhibited SZ95 sebocyte proliferation by inducing G1 cell arrest. Furthermore, NW-PM2.5 and W-PM2.5 significantly reduced sebaceous lipid synthesis and markedly promoted the production of inflammatory cytokines, including interleukin-1α (IL-1α), IL-6 and IL-8 in SZ95 sebocytes. Additionally, the expression of aryl hydrocarbon (Ah) receptor (AhR), AhR nuclear translocator protein (ARNT), as well as cytochrome P450 1A1 were significantly increased following PM2.5 exposure. Thus, these findings indicate that PM2.5 exerts inhibitory effects on cell proliferation and lipid synthesis, and stimulatory effects on inflammatory cytokine production and AhR signaling activation in human SZ95 sebocytes.

Oxidation of 1-chloropyrene by human CYP1 family and CYP2A subfamily cytochrome P450 enzymes: catalytic roles of two CYP1B1 and five CYP2A13 allelic variants

1. 1-Chloropyrene, one of the major chlorinated polycyclic aromatic hydrocarbon contaminants, was incubated with human cytochrome P450 (P450 or CYP) enzymes including CYP1A1, 1A2, 1B1, 2A6, 2A13, 2B6, 2C9, 2D6, 2E1, 3A4 and 3A5. Catalytic differences in 1-chloropyrene oxidation by polymorphic two CYP1B1 and five CYP2A13 allelic variants were also examined. 2. CYP1A1 oxidized 1-chloropyrene at the 6- and 8-positions more actively than at the 3-position, while both CYP1B1.1 and 1B1.3 preferentially catalyzed 6-hydroxylation. 3. Five CYP2A13 allelic variants oxidized 8-hydroxylation much more than 6- and 3-hydroxylation, and the variant CYP2A13.3 was found to slowly catalyze these reactions with a lower k_cat value than other CYP2A13.1 variants. 4. CYP2A6 catalyzed 1-chloropyrene 6-hydroxylation at a higher rate than the CYP2A13 enzymes, but the rate was lower than the CYP1A1 and 1B1 variants. Other human P450 enzymes had low activities towards 1-chloropyrene. 5. Molecular docking analysis suggested differences in the interaction of 1-chloropyrene with active sites of CYP1 and 2 A enzymes. In addition, a naturally occurring Thr134 insertion in CYP2A13.3 was found to affect the orientation of Asn297 in the I-helix in interacting with 1-chloropyrene (and also 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, NNK) and caused changes in the active site of CYP2A13.3 as compared with CYP2A13.1.