Importance of surface charge of soot nanoparticles in determining inhalation toxicity in mice.

Physicochemical properties of nanoparticles are important in regulating nanoparticle toxicity; however, the contribution of nanoparticle charge remains unclear. The objective of this study was to investigate the pulmonary effects of inhalation of charged soot nanoparticles. We established a stably charged nanoparticle generation system for whole-body exposure in BALB/c mice, which produced positively charged, negatively charged, and neutral soot nanoparticles in a wide range of concentrations. After a 7-day exposure, pulmonary toxicity was assessed, together with proteomics analysis. The charged soot nanoparticles on average carried 1.17-1.35 electric charges, and the sizes for nanoparticles under different charging conditions were all fixed at 69 ~ 72 nm. We observed that charged soot nanoparticles induced cytotoxic LDH and increased lung permeability, with the release of 8-isoprostane and caspase-3 and systemic IL-6 in mice, especially for positively charged soot nanoparticles. Next, we observed that positive-charged soot nanoparticles upregulated Eif2, Eif4, sirtuin, mammalian target of rapamycin (mTOR), peroxisome proliferator-activated receptors (PPAR), and HIPPO-related signaling pathways in the lungs compared with negatively charged soot nanoparticles. HIF1α, sirt1, E-cadherin, and Yap were increased in mice's lungs by positively charged soot nanoparticle exposure. In conclusion, carbonaceous nanoparticles carrying electric ions, especially positive-charged, are particularly toxic when inhaled and should be of concern in terms of pulmonary health protection.

Measuring voluntary responses in healthcare utilization during the COVID-19 pandemic: Evidence from Taiwan.

Healthcare has been one of the most affected sectors during the coronavirus disease 2019 (COVID-19) pandemic. The utilization of related services for non-COVID-19 diseases fell dramatically following the point at which the virus broke out; however, little is known about whether this observed decline in healthcare use was due to voluntary behaviors or enforced measures. This paper quantifies the spontaneous change in healthcare utilization during the pandemic. We utilize a county-by-week-level dataset from Taiwan's National Health Insurance (NHI) record, covering the entire Taiwanese population, and a difference-in-differences design. Our results indicate that even if there were no human mobility restrictions or supply-side constraints, people voluntarily reduced their demand for healthcare, due to fears of contagion, or COVID-related precautionary behaviors. We find that the number of outpatient visits (inpatient admissions) decreased by 19% (10%) during the pandemic period (February to May 2020). Furthermore, the demand response of healthcare for Influenza-like illness (ILI) was much greater and more persistent than for non-ILI, thereby suggesting that the substantial decline in accessing healthcare was induced by positive public health externality of prevention measures for COVID-19. Finally, we find that the demand for healthcare services did not get back to the pre-pandemic baseline, even when there were no local coronavirus cases for 253 consecutive days (mid-April to December 2020) in Taiwan.

JUE insight: Demand for transportation and spatial pattern of economic activity during the pandemic.

Using traffic data from Taiwan for 2020, we quantify how the COVID-19 outbreak affected demand for public and private transportation. Despite there being no governmental restrictions, substantial shifts in travel modes were observed. During the peak of the pandemic in Taiwan within the study period (mid-March 2020), railway ridership declined by 40% to 60%, while highway traffic volume increased by 20%. Furthermore, railway ridership was well below pre-pandemic levels, though there were no locally transmitted cases in the eight-month period from mid-April to December. These changes in traffic patterns had implications for spatial patterns of economic activity: retail sales and nighttime luminosity data show that during the pandemic, economic activity shifted away from areas in the vicinity of major railway stations.

Insights to the 3D internal morphology and metal oxidation states of single atmospheric aerosol particles by synchrotron-based methodology.

The morphology and metal oxidation states of atmospheric aerosols are pertinent to their formation processes and ensuing interactions with surrounding gases, vapors and other environments upon deposition, such as human respiratory tract, soil and water. Although much progress has been made in recent years through single-particle techniques, considerably less is known with respect to the three-dimensional (3D) internal morphology of single atmospheric aerosol particles due to the limited penetration depth of electron microscopy. In this study, for the first time, a novel synchrotron-based transmission X-ray microscopy (TXM) methodology has been developed to visualize the 3D internal chemical mixing state and structure of single particles. The results show that the TXM is more applicable to the imaging of solid particles containing high-density elements, e.g., iron (Fe), aluminum (Al), silicone (Si), carbon (C) and sulfur (S), and/or solid particles of sizes larger than about 100 nm. In addition, the TXM is capable to reveal the fine 3D topographic features of single particles. The derived 3D internal and external information would be difficult to discern in the 2D images from electron microscopy. The TXM 3D images illustrate that aerosol particles exhibit complex internal mixing state and structure, e.g., homogeneously-, heterogeneously-mixed, multiple inclusions, fibrous, porous, and core-shell configuration. When coupled with the synchrotron-based X-ray fluorescence spectrometry (XRF) and absorption near-edge spectroscopy (XANES) of an X-ray nanoprobe in the energy range of 4-15 keV, the 3D morphology of single particles is further supplemented with the spatial distribution and oxidation sates of selected elements, including Fe, vanadium (V), manganese (Mn), chromium (Cr) and arsenic (As). The presented cross-platform, synchrotron-based methodology shows promise in complementing existing single-particle techniques and providing new insights to the heterogeneity of single-particle micro-physicochemical states relevant to the aerosol chemistry, optical properties, and their environmental and health impacts.

Impacts of hazardous metals and PAHs in fine and coarse particles with long-range transports in Taipei City.

This study assessed the impact on air quality and health risk by long-range transported (LRT) PM2.5-10- and PM2.5-bound metals and PAHs in Taipei City, Taiwan. Several methods with receptor aerosol measurements were used to quantify the effect of LRT. The hybrid single particle lagrangian integrated trajectory model (HYSPLIT) was used in conjunction with the potential source contribution function (PSCF) to distinguish the LRT aerosols. By using a general linear model (GLM) with a marginal mean and positive matrix fraction (PMF), this study also evaluated the annual increased level of LRT (AIRLRT) for each source contribution to the concentration and the resultant health risk of particle-bound metals and polycyclic aromatic hydrocarbons (PAHs). The LRT influenced fine-sized metals and PAHs rather than coarse-sized ones. We found that the level of PM2.5-bound toxic metals (Pb, Cd, and As) and PAHs (Benzo[a]pyrene and dibenzo[a,e]pyrene) could increase by 90% under the influence of LRT in 2014, while an AIRLRT value of 25% for the PM2.5 mass concentration was observed. Overall, the excess cancer risk (ECR) resulting from PM2.5-bound metal and PAH exposures was 6.40 × 10-5 in relation to coal combustions (20.7%), traffic-related emissions (59.7%) and re-suspended aerosols (19.6%). Among these contributors, LRT-related metals and PAHs in PM2.5 accounted for 51% of the total ECR.

PM2.5- and PM10-bound polycyclic aromatic hydrocarbons (PAHs) in the residential area near coal-fired power and steelmaking plants of Taichung City, Taiwan: In vitro-based health risk and source identification.

We investigated spatial and season variations in particle-bound PAH concentrations, identified their potential sources and estimated resultant health risk of activate toxicity pathways in a residential area near coal-fired power and steelmaking plants. Both atmospheric PM2.5 and PM10 samples (n = 94) were simultaneously collected for summer and winter in the Wuqi and Shalu districts of Taichung City, central Taiwan. The principal component analysis (PCA) measure was used to evaluate the sources of particle-bound PAHs. The health risk of PAHs-activated toxicity pathways was estimated through a probabilistic model in cooperation with high-throughput screening (HTS) in vitro assays and measurement data for children and adults. No spatial difference, but significant seasonal variation, in PAH concentrations for PM2.5 (summer = 1.7 ng m-3 and winter = 4.7 ng m-3) and PM10 (summer = 2.1 ng m-3 and winter = 4.8 ng m-3) between two sites was observed, where both sites shared the similar PAH patterns in congener concentrations. PAH contents in the fine mode (PM2.5) of ambient particles are predominant while coarse mode (PM2.5-10) PAHs is negligible. Children with particle-bound PAH exposures have a relatively high health risk of aryl hydrocarbon receptor (AhR)-mediated adverse outcomes than adults, in particular in the winter period, while the activations of Nrf2 and p53 pathways are insignificant. Vehicle emission (67.1%), unburned petroleum (15.0%), steel industry and stationary emission (6.1%), and oil combustion + cooking oil fume (5.6%) associated with PM2.5-bound PAHs were apportioned. The emission from the Taichung coal-fired power plant is rarely attributable to particle-bound PAHs of the study area based on results of spatiotemporal variation of PAHs, wind direction, and source apportionment.

Characterization of particulate-phase polycyclic aromatic hydrocarbons emitted from incense burning and their bioreactivity in RAW264.7 macrophage.

This study investigated the effects of particle-bound polycyclic aromatic hydrocarbons (PAHs) produced from burning three incense types on and their bioreactivity in the RAW 264.7 murine macrophage cell line. Gas chromatography/mass spectrometry was used to determine the levels of 16 identified PAHs. Macrophages were exposed to incense particle extracts at concentrations of 0, 3.125, 6.25, 12.5, 25, 50, and 100 µg/mL for 24 h. After exposure, cell viability and nitric oxide (NO) and inflammatory mediator [tumor necrosis factor (TNF)-α] production of the cells were examined. The mean atomic hydrogen (H) to carbon (C) ratios in the environmentally friendly, binchotan charcoal, and lao shan incenses were 0.69, 1.13, and 1.71, respectively. PAH and total toxic equivalent (TEQ) mass fraction in the incenses ranged from 137.84 to 231.00 and 6.73-26.30 pg/µg, respectively. The exposure of RAW 264.7 macrophages to incense particles significantly increased TNF-α and NO production and reduced cell viability. The cells treated with particles collected from smoldering the environmentally friendly incense produced more NO and TNF-α compared to other incenses. Additionally, the TEQ of fluoranthene (FL), pyrene (Pyr), benzo[a]anthracene (BaA), chrysene (Chr), benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF), benzo[a]pyrene (BaP), indeno[1,2,3-cd]pyrene (INP), dibenz[a,h]anthracene (DBA), and benzo[g,h,i]perylene [B(ghi)P] had a significant correlation (R2 = 0.64-0.98, P < 0.05) with NO and TNF-α production. The current findings indicate that incense particle-bound PAHs are biologically active and that burning an incense with a lower H/C ratio caused higher bioreactivity. The stimulatory effect of PAH-containing particles on molecular mechanisms of inflammation are critical for future study.

Ambient PM2.5-bound polycyclic aromatic hydrocarbons (PAHs) in Changhua County, central Taiwan: Seasonal variation, source apportionment and cancer risk assessment.

This study investigates PM2.5-bound PAHs for rural sites (Dacheng and Fangyuan) positioned close to heavy air-polluting industries in Changhua County, central Taiwan. A total of 113 PM2.5 samples with 22 PAHs collected from 2014 to 2015 were analyzed, and Positive Matrix Factorization (PMF) and diagnostic ratios of PAHs were applied to quantify potential PAH sources. The influences of local and regional sources were also explored using the conditional probability function (CPF) and potential source contribution function (PSCF) with PMF-modeled results, respectively. Annual mean concentrations of total PAHs were 2.91 ± 1.34 and 3.04 ± 1.40 ng/m3 for Dacheng and Fangyuan, respectively, and their corresponding BaPeq were measured at 0.534 ± 0.255 and 0.563 ± 0.273 ng/m3 in concentration. Seasonal variations with higher PAHs found for the winter than for the spring and summer were observed for both sites. The lifetime excess cancer risk (ECR) from inhalation exposure to PAHs was recorded as 4.7 × 10-5 overall. Potential sources of PM2.5-bound PAHs include unburned petroleum and traffic emissions (42%), steel industry and coal combustion (31%), and petroleum and oil burning (27%), and unburned petroleum and traffic emission could contribute the highest ECR (2.4 × 10-5). The CPF results show that directional apportionment patterns were consistent with the actual locations of local PAH sources. The PSCF results indicate that mainly northeastern regions of China have contributed elevated PM2.5-bound PAHs from long-range transports.

Characterization of polycyclic aromatic hydrocarbon emissions in the particulate and gas phase from smoldering mosquito coils containing various atomic hydrogen/carbon ratios.

The polycyclic aromatic hydrocarbon emissions in particulate and gas phases generated from smoldering mosquito coils containing various atomic H/C ratios were examined. Five types of mosquito coils were burned in a test chamber with a total airflow rate of 8.0 L/min at a constant relative humidity and temperature. The concentrations of individual PAHs were determined using the GC/MS technique. Among the used mosquito coils, the atomic H/C ratio ranged from 1.23 to 1.57, yielding total mass, gaseous, and particulate PAH emission factors of 28.17-78.72 mg/g, 26,139.80-35,932.98 and 5735.22-13,431.51 ng/g, respectively. The various partitions of PAHs in the gaseous and particulate phases were in the ranges, 70.26-83.70% and 16.30-29.74% for the utilized mosquito coils. The carcinogenic potency of PAH emissions in the particulate phase (203.82-797.76 ng/g) was approximately 6.92-25.08 times higher than that of the gaseous phase (26.27-36.07 ng/g). Based on the analyses of PAH emissions, mosquito coils containing the lowest H/C ratio, a low oxygen level, and additional additives (i.e., CaCO3) are recommended for minimizing the production of total PAH emission factors and carcinogenic potency.

Characterization of polycyclic aromatic hydrocarbon emissions in the particulate phase from burning incenses with various atomic hydrogen/carbon ratios.

Polycyclic aromatic hydrocarbons in the particulate phase generated from burning various incense was investigated by a gas chromatography/mass spectrometry. Among the used incenses, the atomic H/C ratio ranged from 0.51 to 1.69, yielding the emission factor ranges for total particulate mass and PAHs of 4.19-82.16 mg/g and 1.20-9.50 µg/g, respectively. The atomic H/C ratio of the incense was the key factor affecting particulate mass and the PAHs emission factors. Both the maximum emission factor and the slowest burning rate appear at the H/C ratio of 1.57. The concentrations of the four-ring PAHs predominated and the major species among the 16 PAHs were fluoranthene, phenanthrene, pyrene, and chrysene for most incense types. The benzo[a]pyrene, benzo[a]anthracene, benzo[b]fluoranthene, and dibenzo[a,h]anthracene accounted for 87.08-93.47% of the total toxic equivalency emission factor.

Incorporation of sciadonic acid into cellular phospholipids reduces pro-inflammatory mediators in murine macrophages through NF-κB and MAPK signaling pathways.

Sciadonic acid (SCA; Δ5,11,14-20:3), a non-methylene-interrupted polyunsaturated fatty acid (NMIFA), can substitute for arachidonic acid (AA) and reduce prostaglandin E2 (PGE2) synthesis in macrophages. However, little is known about how SCA exerts its anti-inflammatory effects. The objectives of this study were to purify SCA from seeds of Podocarpus nagi and investigate mechanisms underlying the modulatory effects of SCA on inflammatory responses in murine RAW264.7 macrophages. We describe how high-purity SCA (>98%) can be obtained using argentated column chromatography. SCA was dose-dependently incorporated into cellular phospholipids, and increasing SCA incorporation correlated with decreases in the proportions of AA, total monounsaturated fatty acids (MUFA) and total saturated fatty acids (SFA). SCA decreased production of PGE2 (29%), nitric oxide (NO) (31%), interleukin-6 (IL-6) (34%) and tumor necrosis factor-α (TNF-α) (14%). The suppression of pro-inflammatory mediators was due, in part, to decreased expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). SCA incorporation suppressed nuclear factor-kappa B (NF-κB) translocation and phosphorylation of mitogen-activated protein kinases (MAPK), including extracellular signal-regulated kinase (ERK), p38 and c-Jun N-terminal kinase (JNK). These findings indicate that by altering the cellular fatty acid composition SCA can modulate the responsiveness of macrophages to LPS through inactivation of NF-κB and MAPK pathways.

Applying open-path Fourier transform infrared spectroscopy for measuring aerosols.

This paper examines the feasibility of using Open-Path Fourier Transform Infrared Spectroscopy (OP-FTIR) to measure aerosols. The extinction spectra of water, ammonium nitrate, and ammonium sulfate aerosols were first simulated with various particle size distributions (geometric mean ranged from 2 to 10 microm; geometric standard deviation ranged from 1.1 to 2.5) based on the Mie theory. An optimization procedure was developed to retrieve the geometric mean and standard deviation of the aerosols size distributions from the spectra, assuming that the complex refractive index is known. To test sensitivity, we also added 4%, 7%, and 10% noise levels to the spectra and compared the reconstruction results. In the experimental study, water aerosols were generated by a two-fluid nozzle inside a cylindrical chamber (3325 cm(3)). The extinction spectrum was collected with a modified FTIR and the size distribution information was retrieved following the same optimization procedure as the one used in the simulation study. The optimization procedure developed in this study reconstructed the size distribution reasonably well for particles with known refractive index (i.e. homogeneous or internally mixed aerosols). The results were robust with the added noise levels up to 10%, after removing inaccurate estimates with the use of the censoring criteria for reconstructed GSD < 1.3, reconstructed GM < 2.5 microm and GSD < 1.5, and reconstructed GM > 10 microm. With regard to externally mixed aerosols, the reconstructed results were sensitive to the noise within the measuring systems, although most ambient aerosols were internally mixed. The reconstructed size distribution in the chamber experiment had a GM of 3.85 microm and GSD of 1.70. The simulation results were applied to support this reconstruction result. We conclude that OP-FTIR can be used to measure aerosols and screen for the right region for a more detailed aerosol measurement campaign.