Characteristics, health risks, and premature mortality attributable to ambient air pollutants in four functional areas in Jining, China.

Air pollution is one of the leading causes for global deaths and understanding pollutant emission sources is key to successful mitigation policies. Air quality data in the urban, suburban, industrial, and rural areas (UA, SA, IA, and RA) of Jining, Shandong Province in China, were collected to compare the characteristics and associated health risks. The average concentrations of PM2.5, PM10, SO2, NO2, and CO show differences of -3.87, -16.67, -19.24, -15.74, and -8.37% between 2017 and 2018. On the contrary, O3 concentrations increased by 4.50%. The four functional areas exhibited the same seasonal variations and diurnal patterns in air pollutants, with the highest exposure excess risks (ERs) resulting from O3. More frequent ER days occurred within the 25-30°C, but much larger ERs are found within the 0-5°C temperature range, attributed to higher O3 pollution in summer and more severe PM pollution in winter. The premature deaths attributable to six air pollutants can be calculated in 2017 and 2018, respectively. Investigations on the potential source show that the ER of O3 (r of 0.86) had the tightest association with the total ER. The bivariate polar plots indicated that the highest health-based air quality index (HAQI) in IA influences the HAQI in UA and SA by pollution transport, and thus can be regarded as the major pollutant emission source in Jining. The above results indicate that urgent measures should be taken to reduce O3 pollution taking into account the characteristics of the prevalent ozone formation regime, especially in IA in Jining.

Green synthesis of silver nanoparticles through oil: Promoting full-thickness cutaneous wound healing in methicillin-resistant Staphylococcus aureus infections.

Due to the emergence of multi-drug resistant microorganisms, the development and discovery of alternative eco-friendly antimicrobial agents have become a top priority. In this study, a simple, novel, and valid green method was developed to synthesize Litsea cubeba essential oil-silver nanoparticles (Lceo-AgNPs) using Lceo as a reducing and capping agent. The maximum UV absorbance of Lceo-AgNPs appeared at 423 nm and the size was 5-15 nm through transmission electron microscopy result. The results of Fourier transform infrared and DLS showed that Lceo provided sufficient chemical bonds for Lceo-AgNPs to reinforce its stability and dispersion. The in vitro antibacterial effects of Lceo-AgNPs against microbial susceptible multidrug-resistant Escherichia coli (E. coli) and methicillin-resistant Staphylococcus aureus (MRSA) were determined. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Lceo-AgNPs against E. coli were 25 and 50 µg/ml. The MIC and MBC of Lceo-AgNPs against MRSA were 50 and 100 µg/ml, respectively. The results of scanning electron microscopy showed that the amount of bacteria obviously decreased and the bacteria cells were destroyed by Lceo-AgNPs. In vivo research disclosed significant wound healing and re-epithelialization effects in the Lceo-AgNPs group compared with the self-healing group and the healing activity was better than in the sulfadiazine silver group. In this experiment, Lceo-AgNPs has been shown to have effects on killing multidrug-resistant bacteria and promoting wound healing. This study suggested Lceo-AgNPs as an excellent new-type drug for wound treatment infected with multidrug-resistant bacteria, and now expects to proceed with clinical research.

Broussonetia papyrifera Polysaccharide Alleviated Acetaminophen-Induced Liver Injury by Regulating the Intestinal Flora.

Liver injury caused by an overdose of acetaminophen (APAP) is a major public health problem. This study aimed to evaluate the effects of Broussonetia papyrifera polysaccharide (BPP) on liver injury and intestinal flora induced by APAP. The results showed that BPP could protect against APAP-induced liver injury, alleviate liver apoptosis, improve antioxidant capacity and enhance the liver's detoxification ability to APAP. At the same time, BPP improved the intestinal flora disorder caused by APAP. More importantly, we found that the hepatoprotective effect of BPP disappeared after the depletion of gut microbiota in mice. Further, we reconstructed the intestinal flora structure of mice through fecal microbiota transplantation and found that the symptoms of APAP-induced liver injury were effectively alleviated. Overall, BPP was a potential hepatoprotective drug that could protect against APAP-induced liver injury and might be mediated by intestinal flora.

Spatial and temporal characteristics of air pollutants and their health effects in China during 2019-2020.

This work presents the temporal and spatial characteristics of the major air pollutants and their associated health risks in China from 2019 to 2020, by using the monitoring data from 367 cities. The annual average PM2.5, PM10, NO2, SO2, CO, and O3 concentrations decreased by 10.9%, 13.2%, 9.3%, 10.1%, 9.4%, and 5.5% from 2019 to 2020. National average PM2.5 concentration in 2020 met the standard of 35 µg/m3, and that of O3 decreased from 2019. COVID-19 lockdown affected NO2 level dramatically, yet influences on PM2.5 and O3 were less clear-cut. Positive correlations between PM2.5 and O3 were found, even in winter in all five key regions, e.g., Jing-Jin-Ji (JJJ), FenWei Plain (FWP), Yangtze River Delta (YRD), Pearl River Delta (PRD) and Chengdu-Chongqing Region (CCR), indicating importance of secondary production for both PM2.5 and O3. Large seasonal variability of PM2.5-SO2 correlation indicates a varying role of SO2 to PM2.5 pollution in different seasons; and generally weak correlations in winter between PM2.5 and NO2 or SO2 reveal the complexity of secondary formation processes to PM2.5 pollution in winter. Multilinear regression analysis between PM2.5 and SO2, NO2 and CO demonstrates that PM2.5 is more sensitive to the change of NO2 than SO2 in JJJ, FWP, PRD and CCR, suggesting a priority of NOx emission control for future PM2.5 reduction. Furthermore, the new World Health Organization Air Quality Guidelines (WHO AQG2021) were adopted to calculate the excess health risks (ER) as well as the health-risk based air quality index (HAQIWHO) of the pollutants. Such assessment points out the severity of air pollution associated health risks under strict standards: 40.0% of days had HAQIWHO>100, while only 14.4% days had AQI>100. PM2.5 ER was generally larger than O3 ER, but O3 ER in low PM2.5 region (PRD) and during summer became more serious. Notably, NO2 ER became even more important than PM2.5 due to its strict limit of WHO AQG2021. Overall, our results highlight the increasing importance of O3 in both air quality evaluation and health risk assessment, and the importance of coordinated mitigation of multiple pollutants (mainly PM2.5, O3 and NO2) in protecting the public health.

The Relative Contributions of Different Chemical Components to the Oxidative Potential of Ambient Fine Particles in Nanjing Area.

Ambient fine particles (PM2.5) have been shown to have adverse health effects by inducing oxidative stress. Here, dithiothreitol (DTT)-based oxidative potential (OP) was used to assess the capacity of oxidative stress caused by PM2.5. In this study, PM2.5 samples were collected in the Nanjing area in 2016, and physicochemical properties and DTT activity were investigated. The annual mean PM2.5 mass concentration was 73 µg m-3 and greatly varied among seasons (spring > winter > summer > autumn). Three fluorescent substances were identified by the excitation-emission matrix (EEM) spectrum. The annual mean mass-normalized DTT activity (DTTm; 0.02 nmol min-1 µg-1) was similar to that documented for cities of some developed countries. The annual mean volume-normalized DTT activity (DTTv) showed a relatively high value of 1.16 nmol min-1 m-3, and the seasonal mean DTTv was highest in winter, followed by spring, autumn, and summer, whose pattern is different from PM2.5 mass concentration. Correlation and multiple linear regression analysis suggested that transition metals may have a greater effect on OP in autumn and winter, humic-like substances and UV absorbing aromatic substances may have a strong effect on OP in spring and summer. Generally, this study enhances our understanding of seasonal variation in health effects associated with PM2.5.

Comparison of air pollutants and their health effects in two developed regions in China during the COVID-19 pandemic.

Air pollution attributed to substantial anthropogenic emissions and significant secondary formation processes have been reported frequently in China, especially in Beijing-Tianjin-Hebei (BTH) and Yangtze River Delta (YRD). In order to investigate the aerosol evolution processes before, in, and after the novel coronavirus (COVID-19) lockdown period of 2020, ambient monitoring data of six air pollutants were analyzed from Jan 1 to Apr 11 in both 2020 and 2019. Our results showed that the six ambient pollutants concentrations were much lower during the COVID-19 lockdown due to a great reduction of anthropogenic emissions. BTH suffered from air pollution more seriously in comparison of YRD, suggesting the differences in the industrial structures of these two regions. The significant difference between the normalized ratios of CO and NO2 during COVID-19 lockdown, along with the increasing PM2.5, indicated the oxidation of NO2 to form nitrate and the dominant contribution of secondary processes on PM2.5. In addition, the most health risk factor was PM2.5 and health-risked based air quality index (HAQI) values during the COVID-19 pandemic in YRD in 2020 were all lower than those in 2019. Our findings suggest that the reduction of anthropogenic emissions is essential to mitigate PM2.5 pollution, while O3 control may be more complicated.

Real-time non-refractory PM1 chemical composition, size distribution and source apportionment at a coastal industrial park in the Yangtze River Delta region, China.

This study present real-time measurements of the chemical composition and particle number size distributions (PNSD) of submicron particulate matter (PM1) in winter at a coastal industrial park in the Yangtze River Delta region of China. Positive matrix factorization (PMF) analysis identified three PNSD factors and three organic aerosol (OA) factors. Contributions and potential source regions of these factors were investigated for four typical periods during the PM1 formation and dissipation process. Results show that the relative contributions from aged 250 nm- factor, fresh 35 nm- and 80 nm- factors were strongly affected by local fresh emissions and regional new particle formation. The non-refractory PM1 measured by Aerodyne aerosol chemical speciation monitor is indicative of the chemical composition of aged 250 nm-factor, but not fresh 35 nm- and 80 nm-factors. The contributions of NO3- and SO42- to NR-PM1 were largely dictated by whether the air mass trajectory went over the sea or the continent. NO3- was abundant (up to 44% of NR-PM1) in cold and dry continental air masses, while SO42- formation (up to 39% of NR-PM1) was preferred in humid and warm marine air masses. Among the three OA source factors, more-oxidized oxygenated OA (MO-OOA) was the most abundant OA factor (44-66% of total OA) throughout the entire field campaign, while an enhanced contribution of 39% from hydrocarbon-like OA (HOA) was observed prior to heavy pollution period. On average, secondary components SO42-, NO3-, NH4+, MO-OOA and less-oxidized oxygenated OA (LO-OOA) contributed 90 ± 7% of NR-PM1, while primary components HOA and Cl- accounted for the remaining 10 ± 7%.

Changes of air quality and its associated health and economic burden in 31 provincial capital cities in China during COVID-19 pandemic.

With outbreak of the novel coronavirus disease (COVID-19), immediate prevention and control actions were imposed in China. Here, we conducted a timely investigation on the changes of air quality, associated health burden and economic loss during the COVID-19 pandemic (January 1 to May 2, 2020). We found an overall improvement of air quality by analyzing data from 31 provincial cities, due to varying degrees of NO2, PM2.5, PM10 and CO reductions outweighing the significant O3 increase. Such improvement corresponds to a total avoided premature mortality of 9410 (7273-11,144) in the 31 cities by comparing the health burdens between 2019 and 2020. NO2 reduction was the largest contributor (55%) to this health benefit, far exceeding PM2.5 (10.9%) and PM10 (23.9%). O3 instead was the only negative factor among six pollutants. The period with the largest daily avoided deaths was rather not the period with strict lockdown but that during February 25 to March 31, due to largest reduction of NO2 and smallest increase of O3. Southwest, Central and East China were regions with relatively high daily avoided deaths, while for some cities in Northeast China, the air pollution was even worse, therefore could cause more deaths than 2019. Correspondingly, the avoided health economic loss attributable to air quality improvement was 19.4 (15.0-23.0) billion. Its distribution was generally similar to results of health burden, except that due to regional differences in willingness to pay to reduce risks of premature deaths, East China became the region with largest daily avoided economic loss. Our results here quantitatively assess the effects of short-term control measures on changes of air quality as well as its associated health and economic burden, and such information is beneficial to future air pollution control.

Comparative Toxic Effects of Manufactured Nanoparticles and Atmospheric Particulate Matter in Human Lung Epithelial Cells.

Although nanoparticles (NPs) have been used as simplified atmospheric particulate matter (PM) models, little experimental evidence is available to support such simulations. In this study, we comparatively assessed the toxic effects of PM and typical NPs (four carbonaceous NPs with different morphologies, metal NPs of Fe, Al, and Ti, as well as SiO2 NPs) on human lung epithelial A549 cells. The EC50 value of PM evaluated by cell viability assay was 148.7 µg/mL, closest to that of SiO2 NPs, between the values of carbonaceous NPs and metal NPs. All particles caused varying degrees of reactive oxygen species (ROS) generation and adenosine triphosphate (ATP) suppression. TiO2 NPs showed similar performance with PM in inducing ROS production (p < 0.05). Small variations between two carbonaceous NPs (graphene oxides and graphenes) and PM were also observed at 50 µg/mL. Similarly, there was no significant difference in ATP inhibition between carbonaceous NPs and PM, while markedly different effects were caused by SiO2 NP and TiO2 NP exposure. Our results indicated that carbonaceous NPs could be served as potential surrogates for urban PM. The identification of PM model may help us further explore the specific roles and mechanisms of various components in PM.

Chemical characteristics, sources and evolution processes of fine particles in Lin'an, Yangtze River Delta, China.

In this study, daily PM2.5 mass and chemical composition were measure in Lin'an Reginal Background Station, Yangzte River Delta, from March 1, 2018, to February 28, 2019. Organic matter (OM) was found to be the most dominant component in four seasons. The proportions of nitrate in PM2.5 presented dramatically lowest in warm seasons but highest in winter, indicating that NO3- was maily driven by thermodynamics. Regional transportation in winter plays a strong impact on PM2.5 concentration, which showed the highest average mass of 60.1 µg m-3. Sulfate occupied a significant portion of PM2.5 in summer (19%), followed by spring (17%), fall (15%), and winter (12%), respectively, suggesting photochemical processes may play a dominant role in the sulfate formation. Secondary inorganic aerosol (SIA) was the dominant component (70%) in the highest polluted periods (PM2.5 > 75 µg m-3), whereas OM decreased into the lowest fraction (22%) of PM2.5. Nitrate was the most important component in SIA in the highest polluted periods with regarding winter. Source apportionment results shown that winter haze was likely strongly dominated by SIA, which was mainly affected by air masses from the North China Plain and Shang-Hangzhou direction. PM2.5 is known to play an important role in sunlight absorption and reversing to human health, continuous observation on PM2.5 species in a background site can help us to evaluate the control policy, and promote our insights to lifetime, formation pathways, health effects of PM2.5.

Chemical Characterization of Seasonal PM2.5 Samples and Their Cytotoxicity in Human Lung Epithelial Cells (A549).

In order to study the toxicity of fine particulate matter (PM2.5) sourced from different seasons on human health, we collected PM2.5 samples quarterly from March 2016 to February 2017 in Nanjing, China. The component analysis results showed that high proportions of water-soluble organic carbon (WSOC), SO42-, Ca2+ and Mg2+ were found in the summer samples, while high proportions of NO3-, NH4+ and heavy metals were observed in the spring and winter samples. Then human lung epithelial cells (A549) were exposed to the PM2.5 samples. The toxicological results indicated that reactive oxygen species (ROS) production in the spring and winter samples was higher than that in the summer and fall samples, which was related to the contribution of some heavy metals and inorganic ions (e.g., Pb and NO3-). However, the apoptosis rates of the cells showed the opposite seasonal changes as what the ROS did, which might be caused by the higher WSOC content in the summer. In addition, regression analysis also showed the importance of the PM2.5 components in ROS production and apoptosis. Particularly, Zn had the strongest correlation with ROS production (R = 0.863) and cell apoptosis (R = 0.675); thus, the specific toxicity of Zn in PM2.5 deserves further investigation. Our results could be beneficial for assessing the health risks and controlling the toxic components of PM2.5 in Nanjing.

Fast sulfate formation from oxidation of SO2 by NO2 and HONO observed in Beijing haze.

Severe events of wintertime particulate air pollution in Beijing (winter haze) are associated with high relative humidity (RH) and fast production of particulate sulfate from the oxidation of sulfur dioxide (SO2) emitted by coal combustion. There has been considerable debate regarding the mechanism for SO2 oxidation. Here we show evidence from field observations of a haze event that rapid oxidation of SO2 by nitrogen dioxide (NO2) and nitrous acid (HONO) takes place, the latter producing nitrous oxide (N2O). Sulfate shifts to larger particle sizes during the event, indicative of fog/cloud processing. Fog and cloud readily form under winter haze conditions, leading to high liquid water contents with high pH (>5.5) from elevated ammonia. Such conditions enable fast aqueous-phase oxidation of SO2 by NO2, producing HONO which can in turn oxidize SO2 to yield N2O.This mechanism could provide an explanation for sulfate formation under some winter haze conditions.

Light-absorbing and fluorescent properties of atmospheric brown carbon: A case study in Nanjing, China.

Brown carbon (BrC), a significant wavelength-dependent atmospheric absorber of solar radiation, plays a key role in photochemistry and long-lasting haze episodes. Herein, two types of BrC extracted from one-year PM2.5 samples (June 2017-May 2018 in Nanjing), i.e. methanol-extracted organic carbon (MSOC) and ultrapure water-extracted organic carbon (WSOC), were obtained to investigate distinct optical properties of atmospheric BrC. The extraction efficiency of BrC was as high as 91% in methanol solution, and the corresponding light absorption coefficient (Abs) of MSOC at 365 nm (Abs365-MSOC, 7.75 ± 3.95 Mm-1) was approximately 1.6 times that of WSOC (Abs365-WSOC, 4.84 ± 2.97 Mm-1), indicating that the water-insoluble compounds mostly affected the light absorption of BrC. The seasonal variations of Abs365-WSOC and Abs365-MSOC were followed the sequence of winter > spring > autumn > summer, due to the dominated emissions from fossil fuel combustion and biomass burning in the cooling seasons. Additionally, four fluorescent chromophores in WSOC and MSOC, containing three humic-like chromophores and one protein-like chromophore, exhibited the highest fluorescent intensities in winter but weakest in summer. The lower humification index (HIX) in MSOC reflects that humic-like chromophores were preferentially water-soluble, in coordination with high degree of photo-oxidation and aromaticity. Fluorescence index (FI) of BrC was also higher in winter because of the effects of photo-bleaching, whereas biological index (BIX) remained stable throughout a year. Considering the correlation between primary organic carbon (POC) and secondary organic carbon (SOC), aside from the contribution of primary emissions, secondary formation has become another major source to atmospheric BrC in Nanjing.

Validation of a sensitive high performance liquid chromatography tandem mass spectrometric method for measuring carbohydrates in aerosol samples.

Carbohydrates (such as levoglucosan) are a class of important water-soluble organic compounds in atmosphere. In this study, a high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) was applied to characterize carbohydrates in aerosol particles. Since carbohydrate was a kind of compound with low response in mass spectrometry, the conventional HPLC-MS/MS method was not sensitive enough to determine it. When acetate acid was added into mobile phase as buffer, the transition of [M+CH3COO]-→[M-H]- could be selected as the quantification ions. In the range from 1.0 µg L-1 to 20 µg mL-1, the coefficients of regression (r2) were more than 0.990, and relative standard deviations (RSD) for replicated injections were lower than 2%. The limit of detection (LOD) and quantification (LOQ) were lower than 2.5 ng L-1 and 10 ng L-1, respectively. The precision and accuracy were examined by spiked samples at three different concentration levels (10 µg L-1, 100 µg L-1, and 500 µg L-1) in five replicates. Recovery ratios ranged from 85% to 115% with RSD lower than 16%. Matrix effects of different carbohydrates ranged from 62% to 120%. The most sensitive HPLC-MS/MS method was developed and validated to analyze 40 aerosol samples successfully. The carbohydrates including three sugar alcohols (threitol, arabitol and sorbitol), one monosaccharide sugar (inositol), two disaccharides (sucrose, trehalose), one anhydrosugar (levoglucosan) and one 2-methyltetrols (2-Methylbutane-1,2,3,4-tretraol) were successfully quantified.

In vitro toxicity evaluation of heavy metals in urban air particulate matter on human lung epithelial cells.

Heavy metals are widely recognized as toxic components in urban air particulate matter (PM). However, the major toxic metals and their interactions are poorly understood. In this study, we attempted to explore the toxicity contribution and combined effects of PM-bounded metals in human lung epithelial cells (A549). Real-time cell analysis indicated that the critical toxic concentration (EC50) of PM detected in this study was 107.90 mg/L (r2 = 1.00, p < 0.01). The cell viability of A549 increased significantly (12.3%) after metal removal in PM, demonstrating an important contribution of metal components to PM toxicity. Among eleven elements examined (Zn, Cr, Mn, Fe, Ni, Cu, As, Se, Sr, Cd, and Pb), six heavy metals (Zn, Cr, Mn, Fe, Cu, and Pb) might account for PM toxicity in A549 cells, and their co-exposure led to a high mortality of A549 cells (36.5 ±â€¯7.3%). For combination treatments, cell mortality caused by single or multiple metal mixtures was usually alleviated by Fe addition, while it was often aggravated in the presence of Mn. The varying effects of other metals (Zn, Cu, Pb and Cr) on different metal mixtures might be explained by their interactions (e.g., similar or dissimilar membrane transporters and intracellular targets). Furthermore, the concentration addition model (CA), independent action model (IA), integrated addition model (IAM) and integrated addition and interaction model (IAI) were used to predict mixture toxicity, and the IAI model exhibited the least variation between observed and predicted toxic effects (r2 = 0.87, p < 0.01). Our results highlight the potential contribution from heavy metals and their interactions to PM toxicity, and promote the application of toxicity prediction models on metal components in PM.

Characterization of Fine Particulate Matter and Associated Health Burden in Nanjing.

Particulate matter (PM) air pollution has become a serious environmental problem in Nanjing and poses great health risks to local residents. In this study, characteristics of particulate matter with an aerodynamic diameter less than 2.5 µm (PM2.5) over Nanjing were analyzed using hourly and daily averaged PM2.5 concentrations and meteorological parameters collected from nine national monitoring sites during the period of March 2014 to February 2017. Then, the integrated exposure-response (IER) model was applied to assess premature mortality, years of life lost (YLL) attributable to PM2.5, and mortality benefits due to PM2.5 reductions. The concentrations of PM2.5 varied among hours, seasons and years, which can be explained by differences in emission sources, secondary formations and meteorological conditions. The decreased ratio of PM2.5 to CO suggested that secondary contributions decreased while the relative contributions of vehicle exhaust increased from increased CO data. According to the values of attributable fractions (AF), stroke was the major cause of death, followed by ischemic heart disease (IHD), lung cancer (LC) and chronic obstructive pulmonary disease (COPD). The estimated total deaths in Nanjing due to PM2.5 were 12,055 and 10,771, leading to 98,802 and 87,647 years of life lost in 2014 and 2015, respectively. The elderly and males had higher health risks than youngsters and females. When the PM2.5 concentrations meet the World Health Organization (WHO) Air Quality Guidelines (AQG) of 10 µg/m³, 84% of the premature deaths would be avoided, indicating that the Nanjing government needs to adopt more stringent measure to reduce PM pollution and enhance the health benefits.

Air pollution characteristics and health risks in Henan Province, China.

Events of severe air pollution occurred frequently in China recently, thus understanding of the air pollution characteristics and its health risks is very important. In this work, we analyzed a two-year dataset (March 2014 - February 2016) including daily concentrations of six criteria pollutants (PM2.5, PM10, CO, SO2, NO2, and O3) from 18 cities in Henan province. Results reveal the serious air pollution status in Henan province, especially the northern part, and Zhengzhou is the city with the worst air quality. Annual average PM2.5 concentrations exceed the second grade of Chinese Ambient Air Quality Standard (75µg/m3) at both 2014 and 2015. PM2.5 is typically the major pollutant, but ozone pollution can be significant during summer. Furthermore, as the commonly used air quality index (AQI) neglects the mutual health effects from multiple pollutants, we introduced the aggregate air quality index (AAQI) and health-risk based air quality index (HAQI) to evaluate the health risks. Results show that based on HAQI, the current AQI system likely significantly underestimate the health risks of air pollution, highlighting that the general public may need stricter health protection measures. The population-weighted two-year average HAQI data further demonstrates that all population in the studied cities in Henan province live with polluted air - 72% of the population is exposed to air that is unhealthy for sensitive people, while 28% of people is exposed to air that can be harmful to healthy people; and the health risks are much greater during winter than during other seasons. Future works should further improve the HAQI algorithm, and validate the links between the clinical/epidemiologic data and the HAQI values.