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The Indochina biomass burning (BB) season in springtime has a substantial environmental impact on the surrounding areas in Asia. In this study, we evaluated the environmental impact of a major long-range BB transport event on 19 March 2018 (a flight of the High Altitude and Long Range Research Aircraft (HALO; https://www.halo-spp.de, last access: 14 February 2023) research aircraft, flight F0319) preceded by a minor event on 17 March 2018 (flight F0317). Aircraft data obtained during the campaign in Asia of the Effect of Megacities on the transport and transformation of pollutants on the Regional to Global scales (EMeRGe) were available between 12 March and 7 April 2018. In F0319, results of 1 min mean carbon monoxide (CO), ozone (O3), acetone (ACE), acetonitrile (ACN), organic aerosol (OA), and black carbon aerosol (BC) concentrations were up to 312.0, 79.0, 3.0, and 0.6 ppb and 6.4 and 2.5 µg m−3, respectively, during the flight, which passed through the BB plume transport layer (BPTL) between the elevation of 2000–4000 m over the East China Sea (ECS). During F0319, the CO, O3, ACE, ACN, OA, and BC maximum of the 1 min average concentrations were higher in the BPTL by 109.0, 8.0, 1.0, and 0.3 ppb and 3.0 and 1.3 µg m−3 compared to flight F0317, respectively. Sulfate aerosol, rather than OA, showed the highest concentration at low altitudes ( m) in both flights F0317 and F0319 resulting from the continental outflow in the ECS. The transport of BB aerosols from Indochina and its impacts on the downstream area were evaluated using a Weather Research Forecasting with Chemistry (WRF-Chem) model. The modeling results tended to overestimate the concentration of the species, with examples being CO (64 ppb), OA (0.3 µg m−3), BC (0.2 µg m−3), and O3 (12.5 ppb) in the BPTL. Over the ECS, the simulated BB contribution demonstrated an increasing trend from the lowest values on 17 March 2018 to the highest values on 18 and 19 March 2018 for CO, fine particulate matter (PM2.5), OA, BC, hydroxyl radicals (OH), nitrogen oxides (NOx), total reactive nitrogen (NOy), and O3; by contrast, the variation of J(O1D) decreased as the BB plume's contribution increased over the ECS. In the lower boundary layer ( m), the BB plume's contribution to most species in the remote downstream areas was %. However, at the BPTL, the contribution of the long-range transported BB plume was as high as 30 %–80 % for most of the species (NOy, NOx, PM2.5, BC, OH, O3, and CO) over southern China (SC), Taiwan, and the ECS. BB aerosols were identified as a potential source of cloud condensation nuclei, and the simulation results indicated that the transported BB plume had an effect on cloud water formation over SC and the ECS on 19 March 2018. The combination of BB aerosol enhancement with cloud water resulted in a reduction of incoming shortwave radiation at the surface in SC and the ECS by 5 %–7 % and 2 %–4 %, respectively, which potentially has significant regional climate implications.

Air pollution is typically at its lowest in Taiwan during summer. The mean concentrations of PM10, PM2.5, and daytime ozone (08:00–17:00 LST) during summer (June–August) over central Taiwan were 35–40 µg m−3, 18–22 µg m−3, and 30–42 ppb, respectively, between 2004 and 2019. Sampling analysis revealed that the contribution of organic carbon (OC) to PM2.5 could have exceeded 30 % in urban and inland mountain sites during July in 2017 and 2018. Frequent episodes of air quality deterioration occur over the western plains of Taiwan when an easterly typhoon circulation interacts with the complex topographic structure of the island. We explored an episode of air quality deterioration that was associated with a typhoon between 15 and 17 July 2018 using the Weather Research Forecasting with Chemistry (WRF-Chem) model. The results indicated that the continual formation of low-pressure systems or typhoons in the area between Taiwan and Luzon island in the Philippines provided a strong easterly ambient flow, which lasted for an extended period between 15 and 17 July. The interaction between the easterly flow and Taiwan's Central Mountain Range (CMR) resulted in stable weather conditions and weak wind speed in western Taiwan during the study period. Numerical modeling also indicated that a lee side vortex easily formed, and the wind direction could have changed from southwesterly to northwesterly over central Taiwan because of the interaction between the typhoon circulation and the CMR. The northwesterly wind coupled with a sea breeze was conducive to the transport of air pollutants from the coastal upstream industrial and urban areas to the inland area. The dynamic process for the wind direction changed given a reasonable explanation for why the observed SO42- became the major contributor to PM2.5 during the episode. SO42- contribution proportions (%) to PM2.5 at the coastal, urban, and mountain sites were 9.4 µg m−3 (30.5 %), 12.1 µg m−3 (29.9 %), and 11.6 µg m−3 (29.7 %), respectively. Moreover, the variation of the boundary layer height had a strong effect on the concentration level of both PM2.5 and ozone. The lee vortex and land–sea breeze, as well as the boundary layer development, were the key mechanisms in air pollutant accumulation and transport. As typhoons frequently occur around Taiwan during summer and fall, their effect on the island's air quality merits further research attention.

Ammonium and nitrate are major N-containing aerosol components. The deposition of N-containing aerosols has impacts on regional ecology and the biogeochemical cycle. In this study, aerosols in a rural cloud forest (Xitou in Taiwan) were studied using 15N and 18O isotope analysis to assess the sources and formation pathways of the local N-containing aerosols linking to a metropolitan. Aerosol samples of different size ranges were collected using a micro-orifice uniform deposit impactor (MOUDI) on a half-day basis in December 2018. The chemical functional groups were analyzed using a Fourier-transform infrared spectroscopy with attenuated total reflection (FTIR-ATR) technique, while the isotope analysis was performed using a gas chromatography–isotope ratio mass spectrometer (GC–IRMS). The average measured aerosol concentration (PM10) was 0.98 (ranging from 0.15 to 3.31) and 0.25 (ranging from 0.00 to 1.51) µg m−3 for NH4+ and NO3-, respectively. In general, a higher concentration than nighttime was observed during the daytime by a factor of 1.5–6, likely due to the transportation of pollutants from upper-stream urban and industrial regions through the local sea breeze combined with valley wind. The presence of fog can further elevate the concentration by a factor of 2–3, resulting from the stronger inversion and lower boundary layer height. The higher NH4+ concentration in fine particles under foggy conditions corresponds to submicron-sized NO3- formation via aqueous-phase dissolution with NH4+ neutralization. Furthermore, the higher RH during fog events shifted the mass distribution of aerosol functional groups to a larger mode size. By comparing the δ15N value directly or through the analysis using a statistical isotope mixing model, MixSIAR, NH4+ probably originated from the industries, coal-fired power plants (CFPPs), or fertilizer plants, while NO3- might be contributed from the CFPP, industrial or urban sources. The overall δ18O of NO3- is +72.66 ‰ ± 3.42 ‰, similar to that in other winter Asian studies, suggesting the major formation pathway via O3 oxidation (δ18O=+72.5 ‰ to 101.67 ‰). However, a lower δ18O (<+67 ‰) for particles less than 0.56 µm during foggy daytime suggests the local contribution via the peroxyl radical oxidation before partitioning into aerosol phase under foggy conditions. Overall, the δ15N and δ18O distribution profiles as a function of particle size in the studied rural forest site reveal the evolution of aerosol composition from remote coastal regions with chemical processes along the transport process, which can be further affected by weather conditions such as fog events.

To understand isotope distributions of PM

Background Air pollution, especially fine particulate matter (PM), can cause brain damage, cognitive decline, and an increased risk of neurodegenerative disease, especially alzheimer’s disease (AD). Typical pathological findings of amyloid and tau protein accumulation have been detected in the brain after exposure in animal studies. However, these observations were based on high levels of PM exposure, which were far from the WHO guidelines and those present in our environment. In addition, white matter involvement by air pollution has been less reported. Thus, this experiment was designed to simulate the true human world and to discuss the possible white matter pathology caused by air pollution. Results 6 month-old female 3xTg-AD mice were divided into exposure and control groups and housed in the Taipei Air Pollutant Exposure System (TAPES) for 5 months. The mice were subjected to the Morris water maze test after exposure and were then sacrificed with brain dissection for further analyses. The mean mass concentration of PM2.5 during the exposure period was 13.85 μg/m3. After exposure, there was no difference in spatial learning function between the two groups, but there was significant decay of memory in the exposure group. Significantly decreased total brain volume and more neuronal death in the cerebral and entorhinal cortex and demyelination of the corpus callosum were noted by histopathological staining after exposure. However, there was no difference in the accumulation of amyloid or tau on immunohistochemistry staining. For the protein analysis, amyloid was detected at significantly higher levels in the cerebral cortex, with lower expression of myelin basic protein in the white matter. A diffuse tensor image study also revealed insults in multiple white matter tracts, including the optic tract. Conclusions In conclusion, this pilot study showed that even chronic exposure to low PM2.5 concentrations still caused brain damage, such as gross brain atrophy, cortical neuron damage, and multiple white matter tract damage. Typical amyloid cascade pathology did not appear prominently in the vulnerable brain region after exposure. These findings imply that multiple pathogenic pathways induce brain injury by air pollution, and the optic nerve may be another direct invasion route in addition to olfactory nerve.

There are limited source apportionment studies conducted to assess vertical distributions of fine particulate matter (PM2.5) and its contributing sources in urban regions. Additionally, none of these vertical studies used inorganic and organic tracers simultaneously. The present study aimed to explore the vertical variation of source-specific contributions to PM2.5 by modeling with both inorganic and organic markers in vertically stratified samples in the Taipei metropolis (Taiwan). One hundred and five samples were collected from three floor-levels at one building and analyzed for trace elements and nonpolar organic compounds (NPOCs). Seven source factors, i.e., industrial emission, biomass burning, PAH related, oil combustion, soil dust, traffic related, and environmental tobacco smoke (ETS)/lubricant, were retrieved by positive matrix factorization (PMF). The major contributors, including industrial emission (29%), biomass burning (23%), and oil combustion (22%), could be involved with regional transported aerosols and showed non-significant variation in the vertical distribution. In contrast, both traffic related and ETS/lubricant factors could be the contributors to the statistically significant difference of PM2.5 concentrations between floor-levels.

A quartz crystal microbalance (QCM) with a high sensitivity of 0.1 ng was applied to monitor the oscillation frequency variation (Δf) of standard single species, two-component systems with typical ambient aerosol compositions, and ambient aerosol filter samples as a function of relative humidity (RH) and determine their deliquescence RH (DRH) and phase transition. Δf is associated with the adsorption or desorption process of water molecules for solid samples and physical properties of the sample film during solid-to-aqueous phase transition (deliquescence). During the pre-deliquescence stage, the water adsorption process led to the increased mass with decreasing Δf, especially for the hydrates such as MgCl2 and Ca(NO3)2, which have more than 20% and 40% increased mass, respectively. The water adsorption process might cause a mass deviation of ambient particulate matter measurement using similar instrument principles. During the deliquescence stage, the observed rapid increasing Δf with RH was caused by a significant change in the physical properties (such as density and viscosity) of the sample film. The determined DRH for a given single-component system is consistent with the results estimated from the thermodynamic models. For a complex system, the QCM can determine the DRH1st well as the eutonic point and track the possible variation of the physical properties of inorganic or with organic acid mixture systems. During the post-deliquescence stage, the gradual increasing trend of Δf with RH for Ca(NO3)2 and an external mixture of NaCl-Ca(NO3)2 was mainly contributed by a stronger RH dependent of physical properties for Ca(NO3)2(aq). Overall, this study provides the possible physical properties variation of common aerosol composition as a function of RH, which was consistent with the results calculated from the thermodynamic models. The stronger water adsorption for MgCl2 and Ca(NO3)2 with solid-like viscosity at RH < DRH might lead to different chemical reactivities in the atmospheric chemistry in addition to the radiative forcing of aerosols caused by the hysteresis.

Since the 24-hr PM

Reliable long-horizon PM

Column-averaged dry-air mole fractions of carbon dioxide (XCO2) and methane (XCH4) measured by a solar viewing portable Fourier transform spectrometer (FTS, EM27/SUN) have been characterized and validated by comparison using in situ profile measurements made during the transfer flights of two aircraft campaigns: Korea-United States Air Quality Study (KORUS-AQ) and Effect of Megacities on the Transport and Transformation of Pollutants at Regional and Global Scales (EMeRGe). The aircraft flew over two Total Carbon Column Observing Network (TCCON) sites: Rikubetsu, Japan (43.46∘ N, 143.77∘ E), for the KORUS-AQ campaign and Burgos, Philippines (18.53∘ N, 120.65∘ E), for the EMeRGe campaign. The EM27/SUN was deployed at the corresponding TCCON sites during the overflights. The mole fraction profiles obtained by the aircraft over Rikubetsu differed between the ascending and the descending flights above approximately 8 km for both CO2 and CH4. Because the spatial pattern of tropopause heights based on potential vorticity values from the ERA5 reanalysis shows that the tropopause height over the Rikubetsu site was consistent with the descending profile, we used only the descending profile to compare with the EM27/SUN data. Both the XCO2 and XCH4 derived from the descending profiles over Burgos were lower than those from the ascending profiles. Output from the Weather Research and Forecasting Model indicates that higher CO2 for the ascending profile originated in central Luzon, an industrialized and densely populated region about 400 km south of the Burgos TCCON site. Air masses observed with the EM27/SUN overlap better with those from the descending aircraft profiles than those from the ascending aircraft profiles with respect to their properties such as origin and atmospheric residence times. Consequently, the descending aircraft profiles were used for the comparison with the EM27/SUN data. The EM27/SUN XCO2 and XCH4 data were derived by using the GGG2014 software without applying air-mass-independent correction factors (AICFs). The comparison of the EM27/SUN observations with the aircraft data revealed that, on average, the EM27/SUN XCO2 data were biased low by 1.22 % and the EM27/SUN XCH4 data were biased low by 1.71 %. The resulting AICFs of 0.9878 for XCO2 and 0.9829 for XCH4 were obtained for the EM27/SUN. Applying AICFs being utilized for the TCCON data (0.9898 for XCO2 and 0.9765 for XCH4) to the EM27/SUN data induces an underestimate for XCO2 and an overestimate for XCH4.

Fine particulate matter (PM

The Indochina biomass burning (BB) season in springtime has a substantial environmental impact on the surrounding areas in Asia. In this study, we evaluated the environmental impact of a major long-range BB transport event on 19 March 2018 (a flight of the HALO research aircraft, flight F0319) preceded by a minor event on 17 March 2018 (flight F0317). Aircraft data obtained during the campaign in Asia of the Effect of Megacities on the transport and transformation of pollutants on the Regional to Global scales (EMeRGe) were available between 12 March and 7 April 2018. In the F0319, results of 1-min mean carbon monoxide (CO), ozone (O3), acetone (ACE), acetonitrile (ACN), organic aerosol (OA) and black carbon aerosol (BC) concentrations were up to 312.0 ppb, 79.0 ppb, 3.0 ppb, 0.6 ppb, 6.4 µg m−3, 2.5 µg m−3 respectively, during the flight, which passed through the BB plume transport layer (BPTL) between the elevation of 2000–4000 m over the East China Sea (ECS). During F0319, CO, O3, ACE, ACN, OA and BC maximum of the 1 minute average concentrations were higher in the BPTL by 109.0 ppb, 8.0 ppb, 1.0 ppb, 0.3 ppb, 3.0 µg m−3 and 1.3 µg m−3 compared to flight F0317, respectively. Sulfate aerosol, rather than OA, showed the highest concentration at low altitudes ( The transport of BB aerosols from Indochina and its impacts on the downstream area was evaluated using a WRF-Chem model. Over the ECS, the simulated BB contribution demonstrated an increasing trend from the lowest values on 17 March 2018 to the highest values on 18 and 19 March 2018 for CO, fine particulate matter (PM2.5), OA, BC, hydroxyl radicals (OH), nitrogen oxides (NOx), total reactive nitrogen (NOy), and O3; by contrast, the variation of J(O1D) decreased as the BB plume’s contribution increased over the ECS. In the low boundary layer (y, NOx, PM2.5, BC, OH, O3, and CO) over South China (SC), Taiwan, and the ECS. BB aerosols were identified as a potential source of cloud condensation nuclei, and the simulation results indicated that the transported BB plume had an effect on cloud water formation over SC and the ECS on 19 March 2018. The combination of BB aerosol enhancement with cloud water resulted in a reduction of incoming shortwave radiation at the surface in SC and the ECS which potentially has significant regional climate implications.

Sulfate is among the major components of atmospheric aerosols or fine particulate matters. Aerosols loaded with sulfate result in low air quality, damage to ecosystems, and influences on climate change. Sulfate aerosols could originate from that directly emitted to the atmosphere and that produced by atmospheric physicochemical processes. The latter is generated from sulfur dioxide (SO2) via oxidation either in the gas phase reactions or in the aqueous phase. Several mechanisms of SO2 oxidation have been proposed, but the differentiation of the various mechanisms and identification of the sources remain challenging. To meet this need, a new method to estimate the contribution of the gas-phase reaction between hydroxyl radical (OH) and SO2 to the sulfate aerosol is proposed and investigated. Briefly, we consider the OH-reaction rates of the respective trace gases that compete for OH radicals with SO2 in the troposphere, and estimate the fraction of SO2-OH reaction in the total OH reactivity. Then the relationship between sulfate concentration and the SO2-OH reaction is analyzed statistically to investigate the sources of sulfate in aerosols. We test this method using the data from ground-based observations and aircraft measurements made during the Effect of Megacities on the transport and transformation of pollutants on the Regional to Global scales in Asia (EMeRGe-Asia) over the western Taiwan and West Pacific regions. Our results show that the estimated SO2-OH reactivity fraction is well-correlated with sulfate concentration. The sulfate production from SO2-OH reaction accounts for approximately 30 % of the total sulfate in aerosols collected at the surface and near-surface (altitude 2-OH reaction regionally and globally.

Particulate lead (Pb) is a primary air pollutant that affects society because of its health impacts. This study investigates the source sectors of Pb associated with ambient fine particulate matter (PM2.5) over central-western Taiwan (CWT) with new constraints on the Pb-isotopic composition. We demonstrate that the contribution of coal-fired facilities is overwhelming, which is estimated to reach 35 ± 16% in the summertime and is enhanced to 57 ± 24% during the winter monsoon seasons. Moreover, fossil-fuel vehicles remain a major source of atmospheric Pb, which accounts for 12 ± 5%, despite the current absence of a leaded gasoline supply. Significant seasonal and geographical variations in the Pb-isotopic composition are revealed, which suggest that the impact of East Asian (EA) pollution outflows is important in north CWT and drastically declines toward the south. We estimate the average contribution of EA outflows as accounting for 35 ± 15% (3.6 ± 1.5 ng/m3) of the atmospheric Pb loading in CWT during the winter monsoon seasons.

Particulate lead (Pb) is a primary air pollutant that affects society because of its health impacts. This study investigates the source sectors of Pb associated with ambient fine particulate matter (PM

The hourly measurement of inorganic soluble ions in PM10 aerosols was conducted with new in situ air composition measuring equipment (ACME) from March 15 to April 15, 2016, on Kinmen Island. The purposes of this study are to understand the influences of fog on secondary aerosol formation and to determine the impacts of air pollutants on haze formation under different relative humidity conditions. The hourly measurements showed that the mass fraction of sulfate in PM10 increased with increases in the liquid water content of fog and decreases in the gaseous concentrations of SO2. The value of the SO42−/PM10 ratio is also affected by the concentration of SO2 before the fog occurs and the level of the fog. This finding indicates that a humid environment is important for enhancing the heterogeneous reaction of sulfate formation. The nitrate concentrations were related to the ratio of NH4+ to SO42− during fog episodes. The formation of particulate NO3− was associated with ammonium formation under ammonium-rich conditions (NH4+/SO42− > 1.5). The gas-phase nitrate was usually observed under ammonium-poor conditions. During periods of high particle pollution, the air mass was from near the ground surface in the mainland coastal areas and transported more pollution to Kinmen. The concentrations of NO2− were higher during periods of high particle pollution, which means that the secondary aerosol formation in the nearby areas also strongly affected the air quality degradation. The short-term and rapid change in the north-south wind system not only brings water vapor from the south but also delivers accumulated pollutants via the transport of northern pollution at low wind speeds.

This study investigated isotopic signatures of carbon (C), lead (Pb) and strontium (Sr) in PM2.5 samples collected from two paired sites (urban vs. rural/background) in northern Taiwan during the summer of 2015 and the spring of 2016, respectively. Significant seasonality was revealed in the isotopic signatures of C and Pb, whereas no seasonal difference was observed in 87Sr/86Sr ratio. The values of δ13C, 206Pb/207Pb, and 208Pb/207Pb were more diverse and exhibited local features in summer. However, during the episodes of continental pollution outbreaks in springtime, the δ13C and Pb isotope ratios of PM2.5 shifted and converged consistently toward the documented characteristics of particulate matters in northern China. Moreover, the results showed that the differences in the Pb and Sr isotopic characteristics between the paired urban and rural sites were statistically insignificant, whereas marginally lower δ13C values were observed at the urban site. It was inferred accordingly that a substantial amount of gaseous hydrocarbons emitted in local urban areas could have been converted to secondary organic aerosols with lower δ13C. On the contrary, the consistency in the spatial and temporal variations of mass concentration and isotope ratios of Pb at the two sites suggested that East-Asian continental pollution outbreak was the major source of Pb-containing particles in the northern Taiwan during springtime. It is noteworthy that there was neither seasonal nor spatial differences in the 87Sr/86Sr ratio observed in this study, which suggested that the Sr-containing particles collected in this study could be originating from a common mixture of sources, including not only natural dust but also the anthropogenic emissions, coal-combustion for instance. This investigation upon the C-Pb-Sr isotopic features evidenced the substantial impacts of the continental pollution outbreaks on the aerosol composition and air quality in the downwind areas of the East-Asian winter monsoons.

Receptor models have been widely used for identifying and quantifying source-specific contributions from mixtures of air pollutants. Nonetheless, our knowledge is still limited on how various components of air pollution are vertically distributed and the sources of such pollutants. In this study, we collected 135 samples of PM2.5 (particles with aerodynamic diameter less than or equal to 2.5 µm) from building balconies at three altitudes in the metropolis of Taipei (Taiwan) and analyzed the samples for elements and polycyclic aromatic hydrocarbons that could be used to identify the sources of those pollutants. We used positive matrix factorization (PMF) to identify seven likely sources, including combustion, sulfur-rich aerosol, fresh traffic, industry/Cr-rich, oil combustion/vehicle, dust, and traffic. Although PM2.5 mass differed significantly between low-level and mid-level sites, the largest contributor to PM2.5 mass (sulfur-rich aerosol, 35.2%) showed nonsignificant variation in the vertical distribution. In contrast, oil combustion/vehicle, which exhibited significant difference between mid-level sites and the other two altitudes, might be a determinant in the vertical variation of PM2.5. We also observed negative trends with sampling height for combustion and traffic emissions.

This study investigated the influence of holiday characteristics and numbers of vacation days on the “holiday effect” of three crucial Chinese holidays in Taipei. Surface measurements of NOx, CO, NMHC, O3, SO2, and PM10 from 13 air quality-monitoring stations of the Taiwan Environmental Protection Administration (TEPA) in the Taipei metropolitan area during holiday and non-holiday periods of 1994–2012 were used. All six pollutants were proven to exhibit holiday effects between Chinese New Year (CNY) and non-Chinese New Year (NCNY) periods. However, almost all pollutants exhibited holiday effects for the two other holidays; the exceptions were O3 between Tomb Sweeping Day (TSD) and non-Tomb Sweeping Day (NTSD) periods and CO and PM10 between Mid-Autumn Day (MAD) and non-Mid-Autumn Day (NMAD) periods. Air pollutants, including NOx, CO, NMHC, SO2, and PM10, that exhibited holiday effects had consistently lower concentrations in holiday periods than in non-holiday periods, whereas O3 concentrations were higher in holiday periods than in non-holiday periods. A widespread holiday effect with consistent signs indicates a high degree of urbanization in the study area. Compared with CNY–NCNY and MAD–NMAD periods, the TSD–NTSD period had a considerably lower difference of the titration effect, lower NOx resulting in less ozone destruction, in evening traffic hours and an inconsistent holiday effect in the daytime and nighttime, leading to the lack of O3 holiday effect. Because the MAD period had more nighttime activities than the other two holiday periods did, the MAD–NMAD period lacked CO and PM10 holiday effects. The prevalently higher ratios of CO, NMHC, SO2, and PM10 relative to NOx as a proxy of mobile sources and a lower PM2.5/PM10 ratio in the MAD period than in the CNY and TSD periods indicate different pollution sources oriented from holiday activities. The air pollutants exhibited a weakening trend are all associated with a greater improvement in air quality during the non-holiday periods than the holiday periods, which implies successful air pollution control policies. Holiday effects of NOx, NMHC (p

Although numerous epidemiological studies revealed an association between ambient fine particulate matter (PM2.5) exposure and Alzheimer’s disease (AD), the PM2.5-induced neuron toxicity and associated mechanisms were not fully elucidated. The present study assessed brain toxicity in 6-month-old female triple-transgenic AD (3xTg-AD) mice following subchronic exposure to PM2.5 via an inhalation system. The treated mice were whole-bodily and continuously exposed to real-world PM2.5 for 3 months, while the control mice inhaled filtered air. Changes in cognitive and motor functions were evaluated using the Morris Water Maze and rotarod tests. Magnetic resonance imaging analysis was used to record gross brain volume alterations, and tissue staining with hematoxylin and eosin, Nissl, and immunohistochemistry methods were used to monitor pathological changes in microstructures after PM2.5 exposure. The levels of AD-related hallmarks and the oxidative stress biomarker malondialdehyde (MDA) were assessed using Western blot analysis and liquid chromatography-mass spectrometry, respectively. Our results showed that subchronic exposure to environmental levels of PM2.5 induced obvious neuronal loss in the cortex of exposed mice, but without significant impairment of cognitive and motor function. Increased levels of phosphorylated-tau and MDA were also observed in olfactory bulb or hippocampus after PM2.5 exposure, but no amyloid pathology was detected, as reported in previous studies. These results revealed that a relatively lower level of PM2.5 subchronic exposure from the environmental atmosphere still induced certain neurodegenerative changes in the brains of AD mice, especially in the olfactory bulb, entorhinal cortex and hippocampus, which is consistent with the nasal entry and spreading route for PM exposure. Systemic factors may also contribute to the neuronal toxicity. The effects of PM2.5 after a more prolonged exposure period are needed to establish a more comprehensive picture of the PM2.5-mediated development of AD.

This study aimed to find the characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in fine particulate matter from different stationary emission sources (coal-fired boiler, CFB; municipal waste incinerator, MWI; electric arc furnace, EAF) in Taiwan and the relationship between PM2.5 and PM2.5-bound PCDD/Fs with Taiwanese mortality risk. PM2.5 was quantified using gravimetry and corresponding chemical analyses were done for PM2.5-bound chemicals. Mortality risks of PM2.5 exposure and PCDD/Fs exposure were calculated using Poisson regression. The highest concentration of PM2.5 (0.53 ± 0.39 mg/Nm3) and PCDD/Fs (0.206 ± 0.107 ng I-TEQ/Nm3) was found in CFB and EAF, respectively. Higher proportions of PCDDs over PCDFs were observed in the flue gases of CFB and MWI whereas it was reversed in EAF. For ambient air, PCDD/F congeners around the stationary sources were dominated by PCDFs in vapor phase. Positive matrix factorization (PMF) analysis found that the sources of atmosphere PCDD/Fs were 14.6% from EAF (r = 0.81), 52.6% from CFB (r = 0.74), 18.0% from traffic (r = 0.85) and 14.8% from MWI (r = 0.76). For the dioxin congener distribution, PCDDs were dominant in flue gases of CFB and MWI, PCDFs were dominant in EAF. It may be attributed to the different formation mechanisms among wastes incineration, steel-making, and coal-burning processes.

This study aimed to find the characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in fine particulate matter from different stationary emission sources (coal-fired boiler, CFB; municipal waste incinerator, MWI; electric arc furnace, EAF) in Taiwan and the relationship between PM2.5 and PM2.5-bound PCDD/Fs with Taiwanese mortality risk. PM2.5 was quantified using gravimetry and corresponding chemical analyses were done for PM2.5-bound chemicals. Mortality risks of PM2.5 exposure and PCDD/Fs exposure were calculated using Poisson regression. The highest concentration of PM2.5 (0.53 ± 0.39 mg/Nm3) and PCDD/Fs (0.206 ± 0.107 ng I-TEQ/Nm3) was found in CFB and EAF, respectively. Higher proportions of PCDDs over PCDFs were observed in the flue gases of CFB and MWI whereas it was reversed in EAF. For ambient air, PCDD/F congeners around the stationary sources were dominated by PCDFs in vapor phase. Positive matrix factorization (PMF) analysis found that the sources of atmosphere PCDD/Fs were 14.6% from EAF (r = 0.81), 52.6% from CFB (r = 0.74), 18.0% from traffic (r = 0.85) and 14.8% from MWI (r = 0.76). For the dioxin congener distribution, PCDDs were dominant in flue gases of CFB and MWI, PCDFs were dominant in EAF. It may be attributed to the different formation mechanisms among wastes incineration, steel-making, and coal-burning processes.