A universal plasma metabolites-derived signature predicts cardiovascular disease risk in MAFLD.

BACKGROUND: Metabolic associated fatty liver disease (MAFLD) is a novel concept proposed in 2020, which is more practical for identifying patients with fatty liver disease with high risk of disease progression. Fatty liver is a driver for extrahepatic complications, particularly cardiovascular diseases (CVD). Although the risk of CVD in MAFLD could be predicted by carotid ultrasound test, a very early stage prediction method before the formation of pathological damage is still lacking. METHODS: Stool microbiomes and plasma metabolites were compared across 196 well-characterized participants encompassing normal controls, simple MAFLD patients, MAFLD patients with carotid artery pathological changes, and MAFLD patients with diagnosed coronary artery disease (CAD). 16S rDNA sequencing data and untargeted metabolomic profiles were interrogatively analyzed using differential abundance analysis and random forest (RF) machine learning algorithm to identify discriminatory gut microbiomes and metabolomic. RESULTS: Characteristic microbial changes in MAFLD patients with CVD risk were represented by the increase of Clostridia and Firmicutes-to-Bacteroidetes ratios. Faecalibacterium was negatively correlated with mean-intima-media thickness (IMT), TC, and TG. Megamonas, Bacteroides, Parabacteroides, and Escherichia were positively correlated with the exacerbation of pathological indexes. MAFLD patients with CVD risk were characterized by the decrease of lithocholic acid taurine conjugate, and the increase of ethylvanillin propylene glycol acetal, both of which had close relationship with Ruminococcus and Gemmiger. Biotin l-sulfoxide had positive correlation with mean-IMT, TG, and weight. The general auxin pesticide beta-naphthoxyacetic acid and the food additive glucosyl steviol were both positively correlated with the increase of mean-IMT. The model combining the metabolite signatures with 9 clinical parameters accurately distinguished MAFLD with CVD risk in the proband and validation cohort. It was found that citral was the most important discriminative metabolite marker, which was validated by both in vitro and in vivo experiments. CONCLUSIONS: Simple MAFLD patients and MAFLD patients with CVD risk had divergent gut microbes and plasma metabolites. The predictive model based on metabolites and 9 clinical parameters could effectively discriminate MAFLD patients with CVD risk at a very early stage.

Influence of spatial resolution of PM2.5 concentrations and population on health impact assessment from 2010 to 2020 in China.

Ambient PM2.5 pollution is a leading environmental health risk factor worldwide. The spatial resolution of PM2.5 concentrations and population strongly impacts PM2.5-related health impact estimates. However, long-term variations and regional differences in this impact have rarely been explored, particularly in China. Here, by aggregating satellite-derived PM2.5 concentration and population datasets at 1-km resolution in China to coarser resolutions (10, 50, and 100 km), we evaluated decadal changes in the impact of resolution on health assessments at national and local scales. For the sensitivity of population-weighted mean (PWM) PM2.5 concentrations to resolution, we found that the national PWM PM2.5 concentration decreased with coarser resolutions; this pattern was widely observed and was more obvious in southern and central China and the Sichuan Basin. The results showed that the sensitivity of national PWM PM2.5 concentrations to resolution continuously weakened from 2010 to 2020, likely due to a reduction in the spatial heterogeneity of PM2.5 concentrations in regions with high sensitivity. This weakness caused a large underestimation of the long-term trend of national PWM PM2.5 using a 100-km resolution, which was 7% lower than the trend at 1 km. Regarding the sensitivity of PM2.5-attributable mortality to resolution, most of China exhibited a pattern in which attributable mortality decreased with coarser resolution. The sensitivity of the estimated PM2.5-attributable mortality to resolution also weakened over time on a national scale and in most parts of China. Nevertheless, the weakness for mortality sensitivity was not as apparent as for PWM PM2.5 sensitivity. This was likely because different drivers played distinct roles in the temporal variation of the mortality sensitivity: population aging enhanced the sensitivity, and variations in PM2.5 concentrations and population distribution both weakened the sensitivity. However, the national attributable mortality trend at a 100-km resolution was still underestimated by 1.75% relative to the 1-km resolution.

Causal effect of PM1 on morbidity of cause-specific respiratory diseases based on a negative control exposure.

BACKGROUND: Extensive studies have linked PM2.5 and PM10 with respiratory diseases (RD). However, few is known about causal association between PM1 and morbidity of RD. We aimed to assess the causal effects of PM1 on cause-specific RD. METHODS: Hospital admission data were obtained for RD during 2014 and 2019 in Beijing, China. Negative control exposure and extreme gradient boosting with SHapley Additive exPlanation was used to explore the causality and contribution between PM1 and RD. Stratified analysis by gender, age, and season was conducted. RESULTS: A total of 1,183,591 admissions for RD were recorded. Per interquartile range (28 µg/m3) uptick in concentration of PM1 corresponded to a 3.08% [95% confidence interval (CI): 1.66%-4.52%] increment in morbidity of total RD. And that was 4.47% (95% CI: 2.46%-6.52%) and 0.15% (95% CI: 1.44%-1.78%), for COPD and asthma, respectively. Significantly positive causal associations were observed for PM1 with total RD and COPD. Females and the elderly had higher effects on total RD, COPD, and asthma only in the warm months (Z = 3.03, P = 0.002; Z = 4.01, P < 0.001; Z = 3.92, P < 0.001; Z = 2.11, P = 0.035; Z = 2.44, P = 0.015). Contribution of PM1 ranked first, second and second for total RD, COPD, and asthma among air pollutants. CONCLUSION: PM1 was causally associated with increased morbidity of total RD and COPD, but not causally associated with asthma. Females and the elderly were more vulnerable to PM1-associated effects on RD.

Impact of fireworks burning on air quality during the Spring Festival in 2021-2022 in Linyi, a central city in the North China Plain.

The management of fireworks has been strengthened during the Spring Festival in 2022 compared with that in 2021 in Linyi, a central city in the North China Plain. Online measurements of the chemical components of PM2.5 were conducted during the Spring Festival in 2021-2022 to assess the influence of fireworks burning (FB) on air quality. Remarkable achievements have been made in improving air quality during FB period (FBP) in 2021-2022 attributing to the stringent regional emission reduction measures, fireworks control, and favorable meteorological conditions with the concentrations of PM2.5, water-soluble ions, and carbonaceous aerosols decreasing by 73.6%, 78.8%, and 73.5%, respectively. The PM2.5 concentrations increased by 96.3% during FBP compared with those during non-FB period (NFBP) in 2021, while the opposite phenomenon was observed in 2022 with PM2.5 concentrations decreasing by 56.2% because of the favorable meteorological condition during FBP in 2022. As indicators of FB, the Cl-, K+, and Mg2+ concentrations showed an increasing trend during FBP compared with that during NFBP, both in 2021 and 2022, but had little effect on other components. The contribution of FB to PM2.5 decreased from 68.4% in 2021 to 15.7% in 2022 based on the relative ratio method, indicating the various measures conducted by all districts and counties in Linyi helped achieve near zero fireworks emissions by 2022. Besides, the contribution of FB to PM2.5 showed a straight-line upward trend from 19:00 on New Year's Eve, reached its peak (76.1%) at 3:00 on Lunar New Year's Day, while the highest value was only 35.0% during FBP in 2022, indicating the implementation of fireworks ban measures in Linyi achieved a good effect on pollution peak cutting. This study has emphasized the necessity of FB restricting during special holidays.

Attenuation by Time-Restricted Feeding of High-Fat and High-Fructose Diet-Induced NASH in Mice Is Related to Per2 and Ferroptosis.

Nonalcoholic steatohepatitis (NASH) is a chronic and progressive disease whose treatment strategies are limited. Although time-restricted feeding (TRF) is beneficial for metabolic diseases without influencing caloric intake, the underlying mechanisms of TRF action in NASH and its efficacy have not yet been demonstrated. We herein showed that TRF effectively alleviated NASH, producing a reduction in liver enzymes and improvements in liver pathology. Regarding the mechanisms by which TRF mitigates NASH, we ascertained that TRF inhibited ferroptosis and the expression of the circadian gene Per2. By adopting a hepatocyte-specific Per2-knockout (Per2△hep) mice model, we clarified the critical role of Per2 in exacerbating NASH. According to the results of our RNA-Seq analysis, the knockout of Per2 ameliorated NASH by inhibiting the onset of ferroptosis; this was manifested by diminished lipid peroxidation levels, decreased mRNA and protein levels for ferroptosis-related genes, and alleviated morphologic changes in mitochondria. Furthermore, using a ferroptosis inhibitor, we showed that ferroptosis significantly aggravated NASH and noted that this was likely achieved by regulation of the expression of peroxisome proliferator activated receptor (PPAR)α. Finally, we discerned that TRF and hepatocyte-specific knockout of Per2 promoted the expression of PPARα. Our results revealed a potential for TRF to effectively alleviate high-fat and high-fructose diet-induced NASH via the inhibition of Per2 and depicted the participation of Per2 in the progression of NASH by promoting ferroptosis, which was ultimately related to the expression of PPARα.

Ozone pollution in the plate and logistics capital of China: Insight into the formation, source apportionment, and regional transport.

As the logistics and plate capital of China, the sources and regional transport of O3 in Linyi are different from those in other cities because of the significant differences in industrial structure and geographical location. Twenty-five ozone pollution episodes (OPEs, 52 days) were identified in 2021, with a daily maximum 8-h moving average O3 concentration (O3-MDA8) of 184.5 ± 22.5 µg/m3. Oxygenated volatile organic compounds (OVOCs) and aromatics were the dominant contributors to ozone formation potential (OFP), with contributions of approximately 23.5-52.7% and 20.0-40.8%, respectively, followed by alkenes, alkanes, and alkynes. Formaldehyde, an OVOC with high concentrations emitted from the plate industry and vehicles, contributed the most to OFP (22.7 ± 5.5%), although formaldehyde concentrations only accounted for 9.4 ± 2.7% of the total non-methane hydrocarbon (NMHC) concentrations. The source apportionment results indicated that the plate industry was the dominant O3 contributor (27.0%), followed by other sources (21.6%), vehicle-related sources (18.0%), solvent use (16.9%), liquefied petroleum gas (LPG)/natural gas (NG) (8.8%), and combustion sources (7.7%). Therefore, there is an urgent need to control the plating industry in Linyi to mitigate O3 pollution. The backward trajectory, potential source contribution function (PSCF), and concentration weighted trajectory (CWT) models were used to identify the air mass pathways and potential source areas of air pollutants during the OPEs. O3 pollution was predominantly affected by air masses that originated from eastern and local regions, while trajectories from the south contained the highest O3 concentrations (207.0 µg/m3). The potential source area was from east and south Linyi during the OPEs. Therefore, it is critical to implement regional joint prevention and control measures to lower O3 concentrations.

Gut Non-Bacterial Microbiota: Emerging Link to Irritable Bowel Syndrome.

As a common functional gastrointestinal disorder, irritable bowel syndrome (IBS) significantly affects personal health and imposes a substantial economic burden on society, but the current understanding of its occurrence and treatment is still inadequate. Emerging evidence suggests that IBS is associated with gut microbial dysbiosis, but most studies focus on the bacteria and neglect other communities of the microbiota, including fungi, viruses, archaea, and other parasitic microorganisms. This review summarizes the latest findings that link the nonbacterial microbiota with IBS. IBS patients show less fungal and viral diversity but some alterations in mycobiome, virome, and archaeome, such as an increased abundance of Candida albicans. Moreover, fungi and methanogens can aid in diagnosis. Fungi are related to distinct IBS symptoms and induce immune responses, intestinal barrier disruption, and visceral hypersensitivity via specific receptors, cells, and metabolites. Novel therapeutic methods for IBS include fungicides, inhibitors targeting fungal pathogenic pathways, probiotic fungi, prebiotics, and fecal microbiota transplantation. Additionally, viruses, methanogens, and parasitic microorganisms are also involved in the pathophysiology and treatment. Therefore, the gut nonbacterial microbiota is involved in the pathogenesis of IBS, which provides a novel perspective on the noninvasive diagnosis and precise treatment of this disease.

Mechanisms of ductular reaction in non-alcoholic steatohepatitis.

Non-alcoholic fatty liver disease (NAFLD) is a disease spectrum caused in part by insulin resistance and genetic predisposition. This disease is primarily characterized by excessive lipid accumulation in hepatocytes in the absence of alcohol abuse and other causes of liver damage. Histologically, NAFLD is divided into several periods: simple steatosis, non-alcoholic steatohepatitis (NASH), hepatic fibrosis, cirrhosis, and hepatocellular carcinoma. With the increasing prevalence of obesity and hyperlipidemia, NAFLD has become the main cause of chronic liver disease worldwide. As a result, the pathogenesis of this disease is drawing increasing attention. Ductular reaction (DR) is a reactive bile duct hyperplasia caused by liver injury that involves hepatocytes, cholangiocytes, and hepatic progenitor cells. Recently, DR is shown to play a pivotal role in simple steatosis progression to NASH or liver fibrosis, providing new research and treatment options. This study reviews several DR signaling pathways, including Notch, Hippo/YAP-TAZ, Wnt/ß-catenin, Hedgehog, HGF/c-Met, and TWEAK/Fn14, and their role in the occurrence and development of NASH.

Effectiveness of Tenofovir Alafenamide in Chronic Hepatitis B Patients with Normal Alanine Aminotransferase and Positive Hepatitis B Virus DNA.

BACKGROUND AND AIMS: With an increasing understanding of hepatitis B, the antiviral indications have been broadening gradually. To evaluate the effectiveness of tenofovir alafenamide (TAF) in chronic hepatitis B (CHB) patients with normal alanine aminotransferase (ALT) and detectable hepatitis B virus (HBV) DNA, those who are ineligible for broader antiviral criteria from the Chinese CHB prevention guide (2019). METHODS: A total of 117 patients were recruited and their data were collected from paper or electronic medical records. HBV DNA and liver function were measured at baseline and throughout the 24-week follow-up. The effectiveness endpoint was complete virological response. The safety endpoint was the first occurrence of any clinical adverse event during the treatment. RESULTS: Among the 117 patients, 45 had normal ALT as well as detectable HBV DNA and they were not recommended for antiviral therapy according to Chinese Guidelines (2019). After TAF antiviral therapy, the rates of patients who achieved HBV DNA <20 IU/mL at 4, 12 and 24 weeks were 77.1%, 96.7% and 96.8% respectively. Among them, the undetectable rates of HBV DNA in patients with low baseline viral load at 4, 12 and 24 weeks were 92.3%, 100% and 100%, while the rates of those with high baseline viral load were 68.2%, 94.1% and 94.4%. Compared with 71.4%, 94.4% and 94.7% in the high baseline group, the undetectable rates of HBV DNA at 4, 12 and 24 weeks in the low baseline liver stiffness group were 85.7%, 100% and 100%. There was no statistical significance among the above groups. CONCLUSIONS: CHB patients who had normal ALT and detectable HBV DNA and did not meet "CHB prevention guide (2019)", could achieve complete virological response in 24 weeks after antiviral treatment by TAF.

Air stagnation in China: Spatiotemporal variability and differing impact on PM2.5 and O3 during 2013-2018.

In recent years, winter PM2.5 and summer O3 pollution which often occurred with air stagnation condition has become a major concern in China. Thus, it is imperative to understand the air stagnation distribution in China and elucidate its impact on air pollution. In this study, three air stagnation indices were calculated according to atmospheric thermal and dynamics parameters using ERA5 data. Two improved indices were more suitable in China, and they displayed similar characteristics: most of the air stagnant days were found in winter, and seasonal distributions showed substantial regional heterogeneity. During stagnation events, flat west or northwest winds at 500 hPa and high pressure at surface dominated, with high relative humidity (RH) and temperature (T), weak winds in most regions. The pollutants concentrations on stagnant days were higher than those on non-stagnant days in most studied areas, with the largest difference of the 90th percentiles of maximum daily 8-h average (MDA8) O3 up to 62.2 µg m-3 in Pearl River Delta (PRD) and PM2.5 up to 95.8 µg m-3 in North China Plain (NCP). During the evolution of stagnation events, the MDA8 O3 concentrations showed a significant increase (6.0 µg m-3 day-1) in PRD and a slight rise in other regions; the PM2.5 concentrations and the frequency of extreme PM2.5 days increased, especially in NCP. Furthermore, O3 was simultaneously controlled by temperature and stagnation except for Xinjiang (XJ), with the average growth rate of 19.5 µg m-3 every 3 °C at 19 °C-31 °C. PM2.5 was dominated by RH and stagnation in northern China while mainly controlled by stagnation in southern China. Notably, the extremes of summer O3 (winter PM2.5) pollution was most associated with air stagnation and T at 25 °C-31 °C (air stagnation and RH >50%). The results are expected to provide important reference information for air pollution control in China.

Assessment of health benefit of PM2.5 reduction during COVID-19 lockdown in China and separating contributions from anthropogenic emissions and meteorology.

The national lockdown policies have drastically disrupted socioeconomic activities during the COVID-19 pandemic in China, which provides a unique opportunity to investigate the air quality response to such anthropogenic disruptions. And it is meaningful to evaluate the potential health impacts of air quality changes during the lockdown, especially for PM2.5 with adverse health effects. In this study, by using PM2.5 observations from 1388 monitoring stations nationwide in China, we examine the PM2.5 variations between the COVID-19 lockdown (February and March in 2020) and the same period in 2015-2019, and find that the national average of PM2.5 decreases by 18 µg/m3, and mean PM2.5 for most sites (about 75%) decrease by 30%-60%. The anthropogenic and meteorological contributions to these PM2.5 variations are also determined by using a stepwise multiple linear regression (MLR) model combined with the Kolmogorov-Zurbenko filter. Our results show that the change of anthropogenic emissions is a leading contributor to those widespread PM2.5 reductions, and meteorological conditions have the negative influence on PM2.5 reductions for some regions, such as Beijing-Tianjin-Hebei (BTH). Additionally, the avoided premature death due to PM2.5 reduction is estimated as a predicted number based on a log-linear concentration-response function. The total avoided premature death is 9952 in China, with dominant contribution (94%) from anthropogenic emission changes. For BTH, Yangtze River Delta, Pearl River Delta and Hubei regions, the reductions of PM2.5 are 24.1, 24.3, 13.5 and 29.5 µg/m3, with the avoided premature deaths of 1066, 1963, 454 and 583, respectively.

Characterization and source identification of submicron aerosol during serious haze pollution periods in Beijing.

Submicron aerosol is of extensive concern not only due to its significant impact on air quality but also because it is detrimental to human health. In this study, we investigated the characteristics, sources and chemical processes of submicron aerosol based on real-time online measurements of submicron aerosols (NR-PM1) during December 2015 at an urban site in Beijing. The average mass concentration of NR-PM1 was 92.5±84.9 µg/m3, the hourly maximum was 459.1 µg/m3 during the entire observation. The organic aerosol (OA) (55%) was the largest contributor to NR-PM1. The average mass concentration of PAHs was 0.217±0.247 µg/m3, exhibiting the highest concentration at night and the lowest levels in the daytime. The average mass concentration of organic nitrate was 2.52±2.36 µg/m3 and that of inorganic nitrate was 7.62±8.22 µg/m3, accounting for 36% and 64%, respectively, of the total nitrate mass. Positive matrix factorization (PMF) differentiated the OA into five chemical components including LV-OOA, SV-OOA, COA, HOA and CCOA, accounting for 22%, 16%, 13%, 25% and 24% respectively, of the total OA. The average NR-PM1 mass concentration on the heavy polluted days (HPD) was 182.8±70.2 µg/m3, which was approximately 9 times that on clean days (CD). The enhanced secondary formation of SNA was evident on HPD, especially the rapid increase of sulfate (23%) and nitrate (19%).

TAK1: A Molecular Link Between Liver Inflammation, Fibrosis, Steatosis, and Carcinogenesis.

Chronic insult and persistent injury can cause liver inflammation, fibrosis, and carcinogenesis; it can also be associated with metabolic disorders. Identification of critical molecules that link the process of inflammation and carcinogenesis will provide prospective therapeutic targets for liver diseases. Rapid advancements in gene engineering technology have allowed the elucidation of the underlying mechanism of transformation, from inflammation and metabolic disorders to carcinogenesis. Transforming growth factor-ß-activated kinase 1 (TAK1) is an upstream intracellular protein kinase of nuclear factor kappa-B (NF-κB) and c-Jun N-terminal kinases, which are activated by numerous cytokines, growth factors, and microbial products. In this study, we highlighted the functional roles of TAK1 and its interaction with transforming growth factor-ß, WNT, AMP-activated protein kinase, and NF-κB signaling pathways in liver inflammation, steatosis, fibrosis, and carcinogenesis based on previously published articles.

Gut non-bacterial microbiota contributing to alcohol-associated liver disease.

Intestinal microbiota, dominated by bacteria, plays an important role in the occurrence and the development of alcohol-associated liver disease (ALD), which is one of the most common liver diseases around the world. With sufficient studies focusing on the gut bacterial community, chronic alcohol consumption is now known as a key factor that alters the composition of gut bacterial community, increases intestinal permeability, causes intestinal dysfunction, induces bacterial translocation, and exacerbates the process of ALD via gut-liver axis. However, gut non-bacterial communities including fungi, viruses, and archaea, which may also participate in the disease, has received little attention relative to the gut bacterial community. This paper will systematically collect the latest literatures reporting non-bacterial communities in mammalian health and disease, and review their mechanisms in promoting the development of ALD including CLEC7A pathway, Candidalysin (a peptide toxin secreted by Candida albicans), metabolites, and other chemical substances secreted or regulated by gut commensal mycobiome, virome, and archaeome, hoping to bring novel insights on our current knowledge of ALD.

A comprehensive evaluation of aerosol extinction apportionment in Beijing using a high-resolution time-of-flight aerosol mass spectrometer.

An aerosol mass spectrometer (AMS) was used to measure the chemical composition of non-refractory submicron particles (NR-PM1) in Beijing from 2012 to 2013. The average concentration of NR-PM1 was 56 µg·m-3, with higher value of 106 µg·m-3 when Beijing was influenced by air masses from south in winter. Organics was the primary chemical component with a concentration of 26 µg·m-3, accounting for 46% of the total NR-PM1. The ratio of NO3-/SO42- was utilized to identify the relative contribution of stationary and traffic related resource to PM pollution. When NR-PM1 concentration was between 50 and 200 µg·m-3, NO3-/SO42-was larger than 1, indicating traffic resource contributed more than stationary resource during the aerosol growth. A new method was developed to calculate aerosol extinction coefficient (σ) as a function of aerosol optical depth (AOD) and the mixing layer height (MLH). σ derived from the new method showed a statistically significant correlation with that obtained from traditional method, which was calculated using visibility (y = 0.99x + 85 R2 = 0.69). Multiple linear regressions in dependence of chemical component were performed to evaluate light extinction apportionment. Under the overall condition, NR-PM1 contributed about 88% to the whole aerosol light extinction; organics, ammonium chloride, ammonium nitrate, ammonium sulfate, black carbon contributed 30%, 6%, 24%, 26% and 6% of the NR-PM1 light extinction, respectively. By further comparing the light extinction apportionment under the different dominated air masses, we concluded that the organics and ammonium sulfate contributed more in polluted days (36% and 23%) than that in clean days (21% and 21%). Mass ratio (MR) between NR-PM1 and black carbon (MR = massNR-PM1/massBC) was used to identify black carbon aging degree, and the result showed that aerosol mass extinction efficiency increased rapidly after MR reached about 7 in the process of black carbon aging.

Elucidating the quantitative characterization of atmospheric oxidation capacity in Beijing, China.

The atmospheric oxidizing capacity (AOC) is the essential driving force of tropospheric chemistry, but its quantitative representation remains limited. This study presents the detailed evaluation of AOC in the megacity of Beijing based on newly developed indexes that represent the estimated oxidative capacity from the prospective of oxidation products (AOIe) and the potential oxidative capacity considering the oxidation rates of major reactants by oxidants (AOIp). A comprehensive suite of data taken from summer and winter field campaigns were used to create these two indexes and in the calculation of AOC. The AOC showed a clear seasonal pattern, with stronger intensity in summer compared to winter. The gaseous-phase oxidation products (O3 and NO2) dominated AOIe (~80%) during summertime at both sites, while the contribution of particle-phase oxidation products (sulfate, nitrate, and secondary organic aerosol) to AOIe increased in winter (~30%). As for AOIp in summer, the dominant contributor was alkenes (31.0%, urban) and CO (38.5%, suburban), whereas CO and NO2 dominated AOIp at both urban (68.8%) and suburban (61.0%) sites during wintertime. As expected, the dominant oxidant contributor to AOIp during the daytime was OH, while O3 was the second most important oxidant at both sites. The diurnal variations of normalized AOIe and AOIp were examined, revealing that they share the same daytime peak but showed significant bias during the nighttime. To explore the possible deviation in sources between AOIe and AOIp, a constrained photochemical box model and a constrained multiphase chemical box model were used to evaluate AOC budgets and their source apportionment. Our results suggest that unmeasured OVOC (oxygenated volatile organic compound) species and missed heterogeneous oxidation processes in the calculation of AOIp contributed substantially to the underestimation of AOC by this index, which should be taken into consideration in future studies of AOC.

Acute effects of air pollution on lupus nephritis in patients with systemic lupus erythematosus: A multicenter panel study in China.

Air pollution may trigger systemic lupus erythematosus (SLE). However, few studies have investigated the associations between air pollution and complications of SLE, such as lupus nephritis (LN). In this study, multicenter longitudinal data from 13 hospitals in China, including 8552 SLE patients with 24,762 visits, were used. Based on the generalized estimating equation (GEE) model, we assessed the associations of LN occurrence with short-term exposures to different air pollutants including particulate matter with an aerodynamic diameter < 2.5 µm (PM2.5), sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and ozone (O3). We identified 2672 LN patients, and about half of them were from east China. Our results based on the entire data set showed that PM2.5 and NO2 were risk factors for LN within one month after exposure, with odds ratio of 1.16 (95% confidence interval (CI), 1.08-1.19) at lag 18 day and 1.19 (95% CI, 1.12-1.26) at lag 16 day relative to an interquartile range (IQR) increase in PM2.5 and NO2, respectively. This positive association between LN and NO2 was also observed for south, west, and east China. In addition, we found that the short term exposure to CO and O3 was not generally associated with LN. Finally, the negative associations of LN with SO2 were found for the entire region and east China. Our results implied that SLE patients may gain the health benefits of air quality improvement in China. Our work also provided evidence that short-term variations in air pollution may trigger LN, and further studies are needed to confirm these findings and the potential pathogenic mechanisms should be explored.

Insights into the chemistry of aerosol growth in Beijing: Implication of fine particle episode formation during wintertime.

Nucleation particle growth plays a major role in the occurrence of fine particles, yet the mechanism of new particle formation (NPF) remains ambiguous in the complex atmosphere of megacities and hinders the development of measures to mitigate PM2.5 pollution. In this study, the chemistry of ultrafine particles during the growth phase of nucleation events was investigated in urban Beijing from Nov. 15, 2018 to Jan. 15, 2019, using two scanning mobility particle spectrometers (SMPS) systems and an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). During this intense campaign, 11 NPF events were observed and the growth rate (GR) of nanoparticles ranged from 12.5 to 24.5 nm h-1. Four periodic cycles of PM2.5 episodes that included aerosol particle growth to particulate matter pollution were identified. Based on the QGR - QAMS theoretical frame that exploring the balance between the source rate of condensable vapors and the observed growth rate of nanoparticles, we clearly showed the physical and chemical evolution of nano-particle during the growth processes to ambient-atmosphere sizes (>100 nm). Generally, the modal diameter of aerosol particles grew by more than 100 nm (7 out of 11 NPF events) when the nitrate concentration and less-oxidized oxygenated organic aerosol (LO-OOA) were high; however, another class of aerosol particle growth was limited to 50-100 nm (3 out of 11 NPF events) when sulfate was high. Note that the remaining one NPF event could not be identified if it can grow up to 100 nm or not due to the unavailable of observation data during the late growth stage. By linking the aerosol growth with chemical compositions, sulfate and organics were found to be the main contributors during the initial stage of the aerosol growth, while cooking-related OA (COA) enhanced the transition stage, and nitrate and more-oxidized OOA (MO-OOA) dominated the subsequent growth of aerosol to ambient-atmosphere sizes. An important portion of aerosol growth in PM2.5 was controlled by semi-volatile organic vapors, which can partition into the externally condensed phase of the accumulation mode and coarse mode via the physical process of adsorption. Through quantifying the physical and chemical properties of aerosol particle growth, the detail processes of nucleation initiated PM2.5 pollution episodes were evaluated and provided observational evidence on the formation mechanism of winter haze pollution in the megacity of Beijing.

Exploring the inorganic and organic nitrate aerosol formation regimes at a suburban site on the North China Plain.

Nitrate-driven aerosol pollution frequently occurs during winter over the North China Plain (NCP). Extensive studies have focused on inorganic nitrate formation, but few have focused on organic nitrates in China, precluding a thorough understanding of the nitrogen cycle and nitrate aerosol formation. Here, the inorganic (NO3,inorg) and organic nitrate (NO3,org) formation regimes under aerosol liquid water (ALW) and aerosol acidity (pH) influences were investigated during winter over the NCP based on data derived from an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). The campaign-averaged concentration of the total nitrate was 5.3 µg m-3, with a 13% contribution from NO3,org, which exhibited a significantly decreased contribution with increasing haze episode evolution. The diurnal cycles of NO3,inorg and NO3,org were similar, with high concentrations during the nighttime at a high ALW level, revealing the important role of aqueous-phase processes. However, the correlations between the aerosol pH and NO3,inorg (R2 = 0.13, P < 0.01) and NO3,org (R2 = 0.63, P < 0.01) during polluted periods indicated a contrasting effect of aerosol pH on inorganic and organic nitrate formation. Our results provide a useful reference for smog chamber studies and promote a better understanding of organic nitrate formation via anthropogenic emissions.

Significant changes in autumn and winter aerosol composition and sources in Beijing from 2012 to 2018: Effects of clean air actions.

A seven-year long-term comprehensive measurement of non-refractory submicron particles (NR-PM1) in autumn and winter in Beijing from 2012 to 2018 was conducted to evaluate the effectiveness of the clean air actions implemented by the Chinese government in September 2013 on aerosols from different sources and chemical processes. Results showed that the NR-PM1 concentrations decreased by 44.1% in autumn and 73.2% in winter from 2012 to 2018. Sulfate showed a much larger reduction than nitrate and ammonium in both autumn (55%) and winter (86%) and that nitrate even slightly increased by 15.8% in autumn. As a result, aerosol pollution in winter gradually changed from sulfate-rich to nitrate-rich with a sudden change after 2016 and the dominant role of nitrate in autumn was also strengthened after 2016. Among primary organic aerosol (OA) types, biomass burning OA and coal combustion OA exhibited the largest decline in autumn and winter, with reductions of 87.5% and 77.3%, respectively, while hydrocarbon-like OA (HOA) exhibited the smallest decline in both autumn (24.4%) and winter (37.1%). These significant changes in aerosol compositions were highly consistent with the much faster reduction of SO2 (75-85%) than NOx (36-59%) and were mainly due to the clean air actions rather than the impact of meteorological conditions. What's more, the enhanced atmospheric oxidizing capacity, which was indicated by increased O3, altered the chemical processes of oxygenated OA (OOA), especially in autumn. Both of less-oxidized OOA (LO-OOA) and more-oxidized OOA showed elevated contributions in OA by 4% in autumn. The increased oxygen-to-carbon ratios of LO-OOA in autumn (from 0.42 to 0.58) and winter (from 0.44 to 0.52) indicated the enhanced atmospheric oxidizing capacity strengthened photochemical reactions and resulted in the increased oxidation degree of LO-OOA. This study demonstrates the effectiveness of the clean air actions for air quality improvement in Beijing.