Characteristics and source apportionment of PM2.5 in Jiaxing, China

Prediction of developmental toxic effects of fine particulate matter (PM2.5) water-soluble components via machine learning through observation of PM2.5 from diverse urban areas

The global health implications of fine particulate matter (PM2.5) underscore the imperative need for research into its toxicity and chemical composition. In this study, zebrafish embryos exposed to the water-soluble components of PM2.5 from two cities (Harbin and Hangzhou) with differences in air quality, underwent microscopic examination to identify primary target organs. The Harbin PM2.5 induced dose-dependent organ malformation in zebrafish, indicating a higher level of toxicity than that of the Hangzhou sample. Harbin PM2.5 led to severe deformities such as pericardial edema and a high mortality rate, while the Hangzhou sample exhibited hepatotoxicity, causing delayed yolk sac absorption. The experimental determination of PM2.5 constituents was followed by the application of four algorithms for predictive toxicological assessment. The random forest algorithm correctly predicted each of the effect classes and showed the best performance, suggesting that zebrafish malformation rates were strongly correlated with water-soluble components of PM2.5. Feature selection identified the water-soluble ions F- and Cl- and metallic elements Al, K, Mn, and Be as potential key components affecting zebrafish development. This study provides new insights into the developmental toxicity of PM2.5 and offers a new approach for predicting and exploring the health effects of PM2.5.

Adverse effects of exposure to fine particles and ultrafine particles in the environment on different organs of organisms

Particulate pollution is a global risk factor that seriously threatens human health. Fine particles (FPs) and ultrafine particles (UFPs) have small particle diameters and large specific surface areas, which can easily adsorb metals, microorganisms and other pollutants. FPs and UFPs can enter the human body in multiple ways and can be easily and quickly absorbed by the cells, tissues and organs. In the body, the particles can induce oxidative stress, inflammatory response and apoptosis, furthermore causing great adverse effects. Epidemiological studies mainly take the population as the research object to study the distribution of diseases and health conditions in a specific population and to focus on the identification of influencing factors. However, the mechanism by which a substance harms the health of organisms is mainly demonstrated through toxicological studies. Combining epidemiological studies with toxicological studies will provide a more systematic and comprehensive understanding of the impact of PM on the health of organisms. In this review, the sources, compositions, and morphologies of FPs and UFPs are briefly introduced in the first part. The effects and action mechanisms of exposure to FPs and UFPs on the heart, lungs, brain, liver, spleen, kidneys, pancreas, gastrointestinal tract, joints and reproductive system are systematically summarized. In addition, challenges are further pointed out at the end of the paper. This work provides useful theoretical guidance and a strong experimental foundation for investigating and preventing the adverse effects of FPs and UFPs on human health.

Combined exposure to PM2.5 and PM10 in reductions of physiological development among preterm birth: a retrospective study from 2014 to 2017 in China

Background

Preterm birth (PTB) has been linked with ambient particulate matter (PM) exposure. However, data are limited between physiological development of PTB and PM exposure.

Methods

Trimester and season-specific PM exposure including PM2.5 and PM10 was collected from Jiaxing between January 2014 and December 2017. Information about parents and 3,054 PTB (gestational age < 37 weeks) outcomes such as weight (g), head circumference (cm), chest circumference (cm), height (cm) and Apgar 5 score were obtained from birth records. We used generalized linear models to assess the relationship between PTB physiological developmental indices and PM2.5, PM10 and their combined exposures. A binary logistic regression model was performed to assess the association between exposures and low birth weight (LBW, < 2,500 g).

Results

Results showed that there were 75.5% of low birth weight (LBW) infants in PTB. Decreased PM2.5 and PM10 levels were found in Jiaxing from 2014 to 2017, with a higher PM10 level than PM2.5 each year. During the entire pregnancy, the highest median concentration of PM2.5 and PM10 was in winter (61.65 ± 0.24 vs. 91.65 ± 0.29 μg/m3) followed by autumn, spring and summer, with statistical differences in trimester-specific stages. After adjusting for several potential factors, we found a 10 μg/m3 increase in joint exposure of PM2.5 and PM10 during the entire pregnancy associated with reduced 0.02 week (95%CI: -0.05, -0.01) in gestational age, 7.9 g (95%CI: -13.71, -2.28) in birth weight, 0.8 cm in height (95%CI: -0.16, -0.02), 0.05 cm (95%CI: -0.08, - 0.01) in head circumference, and 0.3 (95%CI: -0.04, -0.02) in Apgar 5 score, except for the chest circumference. Trimester-specific exposure of PM2.5 and PM10 sometimes showed an opposite effect on Additionally, PM2.5 (OR = 1.37, 95%CI: 1.11, 1.68) was correlated with LBW.

Conclusion

Findings in this study suggest a combined impact of fine particulate matter exposure on neonatal development, which adds to the current understanding of PTB risk and health.

Overview of PM2.5 and health outcomes: Focusing on components, sources, and pollutant mixture co-exposure

PM_2.5 varies in source and composition over time and space as a complicated mixture. Consequently, the health effects caused by PM_2.5 varies significantly over time and generally exhibit significant regional variations. According to numerous studies, a notable relationship exists between PM_2.5 and the occurrence of many diseases, such as respiratory, cardiovascular, and nervous system diseases, as well as cancer. Therefore, a comprehensive understanding of the effect of PM_2.5 on human health is critical. The toxic effects of various PM_2.5 components, as well as the overall toxicity of PM_2.5 are discussed in this review to provide a foundation for precise PM_2.5 emission control. Furthermore, this review summarizes the synergistic effect of PM_2.5 and other pollutants, which can be used to draft effective policies.

Chemical composition characteristics and source analysis of PM2.5 in Jiaxing, China: insights into the effect of COVID-19 outbreak

Jiaxing is a medium-sized city in the Yangtze River Delta (YRD), which showed complex local and surrounding pollution sources. To study the COVID-19 impact on the ambient PM_2.5 in Jiaxing, we collected the PM_2.5 samples from 2 January to 25 April 2020 and analysed their chemical compositions (including carbon components, water-soluble ions (WSIs), and inorganic elements). The concentration of PM_2.5 was 83.13 ± 30.93 μg/m³ before COVID-19 pandemic and then remarkably decreased with COVID-19 outbreak due to the suspension of mobility and industrial activities. Meanwhile, the concentrations of main chemical species (carbon components, water-soluble ions and inorganic elements) of PM_2.5 all decreased from period A (2-20 January 2020) to period B (23 January to 10 February 2020). Moreover, Trajectory clustering analysis showed that close-range transport was one of the dominant factors throughout all the periods, except for period D (1-25 April 2020). In addition, the PSCF model indicated that the COVID-19 outbreak resulted in a significant decrease of WPSCF value. This study highlighted the differences in chemical compositions and sources of PM_2.5 since COVID-19 pandemic was reported and provided a better understanding of its outbreak on PM_2.5.

Chemical characterization, formation mechanisms and source apportionment of PM2.5 in north Zhejiang Province: The importance of secondary formation and vehicle emission

PM_2.5 affects air quality, therefore, chemical evolution, formation mechanism and source identification of PM_2.5 are essential to help figure out mitigation measures. PM_2.5 and its constituents were comprehensively characterized with highly time-resolved measurements from 2019 to 2020 in north Zhejiang Province (Shanxi, SX) for the first time, with an emphasis on the contribution of secondary formation and vehicle emission to PM_2.5. Secondary inorganic ions (sulfate: 3.86 μg/m³, nitrate: 7.82 μg/m³ and ammonium: 4.59 μg/m³, SNA) were found to be the major components (54%) in PM_2.5 (29.70 μg/m³). The highly consistence of nitrate, sulfate and secondary organic compounds (SOC) with Ox (NO₂ + O₃) or RH indicated the importance of photochemical oxidation and heterogeneous reaction in different scenarios. Higher atmospheric oxidative potential facilitated the SOC formation in spring. The PM_2.5 mass was apportioned to eight sources resolved by positive matrix factorization (PMF): secondary nitrate (9.63 μg/m³), secondary sulfate (5.14 μg/m³), vehicle emission (7.26 μg/m³), coal combustion (2.39 μg/m³), biomass burning (1.38 μg/m³), soil dust (0.86 μg/m³), industry emission (0.50 μg/m³), and ship emission (0.32 μg/m³). Secondary nitrate (35%) and sulfate (19%) formation and vehicle emission (26%) were the main factors contributing to the PM_2.5. Furthermore, the contribution of secondary nitrate formation increased with elevating PM_2.5 concentration. Regional transport was synthetically studied by chemical and backward trajectory analysis, reflecting that secondary nitrate contributed severely to the air quality at SX, while vehicle emission contribution enhanced when atmosphere was stagnant. This study first provides long-term comprehensive chemical characterization and source apportionments of PM_2.5 pollution in north Zhejiang, which may provide some guidance for the air pollution control.

Synergistic or Antagonistic Health Effects of Long- and Short-Term Exposure to Ambient NO2 and PM2.5: A Review

Studies on adverse health effects associated with air pollution mostly focus on individual pollutants. However, the air is a complex medium, and thus epidemiological studies face many challenges and limitations in the multipollutant approach. NO2 and PM2.5 have been selected as both originating from combustion processes and are considered to be the main pollutants associated with traffic; moreover, both elicit oxidative stress responses. An answer to the question of whether synergistic or antagonistic health effects of combined pollutants are demonstrated by pollutants monitored in ambient air is not explicit. Among the analyzed studies, only a few revealed statistical significance. Exposure to a single pollutant (PM2.5 or NO2) was mostly associated with a small increase in non-accidental mortality (HR:1.01-1.03). PM2.5 increase of <10 µg/m3 adjusted for NO2 as well as NO2 adjusted for PM2.5 resulted in a slightly lower health risk than a single pollutant. In the case of cardiovascular heart disease, mortality evoked by exposure to PM2.5 or NO2 adjusted for NO2 and PM2.5, respectively, revealed an antagonistic effect on health risk compared to the single pollutant. Both short- and long-term exposure to PM2.5 or NO2 adjusted for NO2 and PM2.5, respectively, revealed a synergistic effect appearing as higher mortality from respiratory diseases.

Health risk assessment of PM2.5 heavy metals in county units of northern China based on Monte Carlo simulation and APCS-MLR

The key areas of China's urbanization process have gradually shifted from urban areas to county-level units. Correspondingly, air pollution in county towns may be heavier than in urban areas, which has led to a lack of understanding of the pollution situation in such areas. In view of this, 236 PM_2.5 filter samples were collected in Pingyao, north of the Fen-Wei Plain, one of the most polluted areas in China. Monte Carlo simulation was used to solve the serious uncertainties of traditional HRA, and the coupling technology of absolute principal component score-multiple linear regression (APCS-MLR) and health risk assessment (HRA) is used to quantitatively analyze the health risks of pollution sources. The results showed that PM_2.5 concentration was highest in autumn, 3.73 times the 24 h guideline recommended by the World Health Organization (WHO). Children were more susceptible to heavy metals in the county-level unit, with high hazard quotient (HQ) values of Pb being the dominant factor leading to an increased non-carcinogenic risk. A significant carcinogenic risk was observed for all groups in autumn in Pingyao, with exposure to Ni in the outdoor environment being the main cause. Vehicle emissions and coal combustion were identified as two major sources of health threats. In short, China's county-level population, about one-tenth of the world's population, faces far more health risks than expected.

Metabolic profiling disturbance of PM2.5 revealed by Raman spectroscopy and mass spectrometry-based nontargeted metabolomics

Fine particulate matter (PM_2.5) is an important risk factor affecting human health. Therefore, a quick method for finding metabolic targets in situ in ambient fine particulate matter is crucial. In this study, the impact of PM_2.5 on human lung epithelial cells (A549) was investigated by Raman spectroscopy and mass spectrometry (MS)-based nontargeted metabolomics analysis. Raman detection indicated that exposure to PM_2.5 reduced the levels of phenylalanine, tyrosine, and nucleotides. Metabolomics results not only demonstrated a significant decrease of the aforementioned metabolites but also added some important metabolite information that could not be detected by Raman spectroscopy. Our study demonstrated that Raman spectroscopy was an in situ, real-time, and rapid detection method for detecting metabolites, especially suitable for the assignment of phenylalanine/tyrosine and nucleotides, which play important roles in cellular growth. Moreover, the metabolic profiling changes observed upon PM_2.5 treatment mainly involved phenylalanine, tyrosine metabolism, purine and pyrimidine metabolism, and energy metabolism, clearly demonstrating that PM_2.5 can inhibit the synthesis of protein and DNA/RNA and reduce cellular energy supplies, further influencing cellular proliferation and other activities.

Health risk assessment and source apportionment of PM2.5-bound toxic elements in the industrial city of Siheung, Korea

The emission sources and their health risks of fine particulate matter (PM_2.5) in Siheung, Republic of Korea, were investigated as a middle-sized industrial city. To identify the PM_2.5 sources with error estimation, a positive matrix factorization model was conducted using daily mean speciated data from November 16, 2019, to October 2, 2020 (95 samples, 22 chemical species). As a result, 10 sources were identified: secondary nitrate (24.3%), secondary sulfate (18.8%), traffic (18.8%), combustion for heating (12.6%), biomass burning (11.8%), coal combustion (3.6%), heavy oil industry (1.8%), smelting industry (4.0%), sea salts (2.7%), and soil (1.7%). Based on the source apportionment results, health risks by inhalation of PM_2.5 were assessed for each source using the concentration of toxic elements portioned. The estimated cumulative carcinogenic health risks from the coal combustion, heavy oil industry, and traffic sources exceeded the benchmark, 1E-06. Similarly, carcinogenic health risks from exposure to As and Cr exceeded 1E-05 and 1E-06, respectively, needing a risk reduction plan. The non-carcinogenic risk was smaller than the hazard index of one, implying low potential for adverse health effects. The probable locations of sources with relatively higher carcinogenic risks were tracked. In this study, health risk assessment was performed on the elements for which mass concentration and toxicity information were available; however, future research needs to reflect the toxicity of organic compounds, elemental carbon, and PM_2.5 itself.

Spatial characteristics of fine particulate matter in subway stations: Source apportionment and health risks

Air in subway stations is typically more polluted than ambient air, and particulate matter concentrations and compositions can vary greatly by location, even within a subway station. However, it is not known how the sources of particulate matter vary between different areas within subway stations, and source-specific health risks in subway stations are unclear. We analyzed the spatial characteristics of particulate matter by source and calculated source-specific health risks on subway platforms and concourses and in station offices by integrating source apportionment with health risk assessments. A total of 182 samples were collected in three areas in six subway stations in Nanjing, China. Enrichment factors and the positive matrix factorization receptor model were used to identify major sources. The carcinogenic and non-carcinogenic health risks to subway workers and passengers were evaluated to determine control priorities. Seven sources of particulate matter were identified in each area, with a total of four subway sources and six outdoor sources over all the areas. The source contributions to total element mass differed significantly from the source contributions to human health risks. Overall, subway sources contributed 48% of total element mass in the station office and 75% and 60% on the concourse and platform, respectively. Subway-derived sources accounted for 54%, 81%, and 71% of non-carcinogenic health risks on station platforms, concourses, and office areas, respectively. The corresponding values for carcinogenic risks were 51%, 86%, and 86%. Among the elements, cobalt had the largest contributions to carcinogenic and non-carcinogenic risks, followed by manganese for non-carcinogenic risks and hexavalent chromium for carcinogenic risks. Reducing emissions from subway sources could effectively protect the health of subway workers and passengers.

An Evaluation of Risk Ratios on Physical and Mental Health Correlations due to Increases in Ambient Nitrogen Oxide (NOx) Concentrations

Nitrogen oxides (NOx) are gaseous pollutants contributing to pollution in their primary form and are also involved in reactions forming ground-level ozone and fine particulate matter. Thus, NOx is of great interest for targeted pollution reduction because of this cascade effect. Primary emissions originate from fossil fuel combustion making NOx a common outdoor and indoor air pollutant. Numerous studies documenting the observed physical health impacts of NOx were reviewed and, where available, were summarized using risk ratios. More recently, the literature has shifted to focus on the mental health implications of NOx exposure, and a review of the current literature found five main categories of mental health-related conditions with respect to NOx exposure: common mental health disorders, sleep, anxiety, depression, and suicide. All the physical and mental health effects with available risk ratios were organized in order of increasing risk. Mental health concerns emerged as those most influenced by NOx exposure, with physical health impacts, such as asthma, only beginning to surface as the fourth highest risk. Mental health conditions occupied seven of the top ten highest risk health ailments. The results summarized in this narrative review show that there are clear positive correlations between NOx and negative physical and mental health manifestations, thus strengthening the argument in support of the reduction in ambient NOx levels.

High-normal blood pressure (prehypertension) is associated with PM2.5 exposure in young adults

We aimed to examine PM_2.5 exposure, blood pressure (SBP and DBP) measurement, and hypertension risk factors and to assess the association between PM_2.5 exposure and hypertension among young adults. The mean SBP was 117.78 mmHg, with 11.22% high-normal blood pressure (prehypertension) and 2.51% hypertension (≥ 140 mmHg). DBP was 75.48 mmHg with 26.37% prehypertension and 4.53% hypertension (≥ 90 mmHg). The median PM_2.5 in the past year was 31.79 μg/m³, with highest in winter (49.33 μg/m³), followed by spring (37.34 μg/m³), autumn (29.64 μg/m³), and summer (24.33 μg/m³). Blood pressure was positively correlated with age, height, weight, BMI, daily smoking, alcohol consumption, mental stress, and staying up in the past 1 year, and negatively with season-specific temperature. After adjustment for the covariates, each 10 μg/m³ increase in PM_2.5 was associated with SBP (day 1 = 1.07 mmHg, day 3 = 1.25 mmHg, day 5 = 1.01 mmHg) and DBP (day 1 = 1.06 mmHg, day 3 = 1.28 mmHg, day 5 = 1.29 mmHg, day 15 = 0.87 mmHg, day 30 = 0.56 mmHg). Exposure in winter and the past year was associated with 1.21 mmHg and 0.95 increase mmHg in SBP, respectively. Logistic models showed for every 1 μg/m³ increase of PM_2.5, SBP in day 1 and day 5 was increased by 6% and 4%, and DPB by 3% and 16%, respectively. SBP was increased by 8% in spring and 19% in winter, and DBP was increased by 7% in winter. Our data suggest a certain prevalence of pre- or hypertension among young population, which is associated with short-term fluctuation and season-specific exposure of PM_2.5.

Spatio-Temporal Characteristics of Air Quality Index (AQI) over Northwest China

In recent years, air pollution has become a serious threat, causing adverse health effects and millions of premature deaths in China. This study examines the spatial-temporal characteristics of ambient air quality in five provinces (Shaanxi (SN), Xinjiang (XJ), Gansu (GS), Ningxia (NX), and Qinghai (QH)) of northwest China (NWC) from January 2015 to December 2018. For this purpose, surface-level aerosol pollutants, including particulate matter (PMx, x = 2.5 and 10) and gaseous pollutants (sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and ozone (O3)) were obtained from China National Environmental Monitoring Center (CNEMC). The results showed that fine particulate matter (PM2.5), coarse particulate matter (PM10), SO2, NO2, and CO decreased by 28.2%, 32.7%, 41.9%, 6.2%, and 27.3%, respectively, while O3 increased by 3.96% in NWC during 2018 as compared with 2015. The particulate matter (PM2.5 and PM10) levels exceeded the Chinese Ambient Air Quality Standards (CAAQS) Grade II standards as well as the WHO recommended Air Quality Guidelines, while SO2 and NO2 complied with the CAAQS Grade II standards in NWC. In addition, the average air quality index (AQI), calculated from ground-based data, improved by 21.3%, the proportion of air quality Class I (0–50) improved by 114.1%, and the number of pollution days decreased by 61.8% in NWC. All the pollutants’ (except ozone) AQI and PM2.5/PM10 ratios showed the highest pollution levels in winter and lowest in summer. AQI was strongly positively correlated with PM2.5, PM10, SO2, NO2, and CO, while negatively correlated with O3. PM10 was the primary pollutant, followed by O3, PM2.5, NO2, CO, and SO2, with different spatial and temporal variations. The proportion of days with PM2.5, PM10, SO2, and CO as the primary pollutants decreased but increased for NO2 and O3. This study provides useful information and a valuable reference for future research on air quality in northwest China.

Health risks of inhaled selected toxic elements during the haze episodes in Shijiazhuang, China: Insight into critical risk sources

PM_2.5 in Shijiazhuang was collected from October 15, 2018 to January 31, 2019, and selected toxic elements were measured. Five typical haze episodes were chosen to analyze the health risks and critical risk sources. Toxic elements during the haze episodes accounted for 0.33% of PM_2.5 mass. Non-cancer risk of toxic elements for children was 1.8 times higher than that for adults during the haze episodes, while cancer risk for adults was 2.5 times higher than that for children; cancer and non-cancer risks were primarily attributable to As and Mn, respectively. Health risks of toxic elements increased during the growth and stable periods of haze episodes. Non-cancer and cancer risks of toxic elements during the haze stable periods were higher than other haze stages, and higher for children than for adults during the stable period. Mn was the largest contributor to non-cancer risk during different haze stages, while As was the largest contributor to cancer risk. Crustal dust, vehicle emissions, and industrial emissions were critical sources of cancer risk during the clean-air periods; while vehicle emissions, coal combustion, and crustal dust were key sources of cancer risk during the haze episodes. Cancer risks of crustal dust and vehicle emissions during the haze episodes were 2.0 and 1.7 times higher than those in the clean-air periods. Non-cancer risks from emission sources were not found during different periods. Cancer risks of biomass burning and coal combustion increased rapidly during the haze growth period, while that of coal combustion decreased sharply during the dissipation period. Vehicle emissions, crustal dust, and coal combustion were significant cancer risk sources during different haze stages, cancer risk of each source was the highest during the stable period. Southern Hebei, Northern and central Shaanxi were potential risk regions that affected the health of both adults and children in Shijiazhuang.

Impact of SARS-CoV-2 on Ambient Air Quality in Northwest China (NWC)

SARS-CoV-2 was discovered in Wuhan (Hubei) in late 2019 and covered the globe by March 2020. To prevent the spread of the SARS-CoV-2 outbreak, China imposed a countrywide lockdown that significantly improved the air quality. To investigate the collective effect of SARS-CoV-2 on air quality, we analyzed the ambient air quality in five provinces of northwest China (NWC): Shaanxi (SN), Xinjiang (XJ), Gansu (GS), Ningxia (NX) and Qinghai (QH), from January 2019 to December 2020. For this purpose, fine particulate matter (PM2.5), coarse particulate matter (PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and ozone (O3) were obtained from the China National Environmental Monitoring Center (CNEMC). In 2020, PM2.5, PM10, SO2, NO2, CO, and O3 improved by 2.72%, 5.31%, 7.93%, 8.40%, 8.47%, and 2.15%, respectively, as compared with 2019. The PM2.5 failed to comply in SN and XJ; PM10 failed to comply in SN, XJ, and NX with CAAQS Grade II standards (35 µg/m3, 70 µg/m3, annual mean). In a seasonal variation, all the pollutants experienced significant spatial and temporal distribution, e.g., highest in winter and lowest in summer, except O3. Moreover, the average air quality index (AQI) improved by 4.70%, with the highest improvement in SN followed by QH, GS, XJ, and NX. AQI improved in all seasons; significant improvement occurred in winter (December to February) and spring (March to May) when lockdowns, industrial closure etc. were at their peak. The proportion of air quality Class I improved by 32.14%, and the number of days with PM2.5, SO2, and NO2 as primary pollutants decreased while they increased for PM10, CO, and O3 in 2020. This study indicates a significant association between air quality improvement and the prevalence of SARS-CoV-2 in 2020.

Review of online source apportionment research based on observation for ambient particulate matter

Particulate matter source apportionment (SA) is the basis and premise for preventing and controlling haze pollution scientifically and effectively. Traditional offline SA methods lack the capability of handling the rapid changing pollution sources during heavy air pollution periods. With the development of multiple online observation techniques, online SA of particulate matter can now be realized with high temporal resolution, stable and reliable continuous observation data on particle compositions. Here, we start with a summary of online measuring instruments for monitoring particulate matters that contains both online mass concentration (online MC) measurement, and online mass spectrometric (online MS) techniques. The former technique collects ambient particulate matter onto filter membrane and measures the concentrations of chemical components in the particulate matter subsequently. The latter technique could be further divided into two categories: bulk measurement and single particle measurement. Aerosol Mass Spectrometers (AMS) could provide mass spectral information of chemical components of non-refractory aerosols, especially organic aerosols. While the emergence of single-particle aerosol mass spectrometer (SPAMS) technology can provide large number of high time resolution data for online source resolution. This is closely followed by an overview of the methods and results of SA. However, online instruments are still facing challenges, such as abnormal or missing measurements, that could impact the accuracy of online dataset. Machine leaning algorithm are suited for processing the large amount of online observation data, which could be further considered. In addition, the key research challenges and future directions are presented including the integration of online dataset from different online instruments, the ensemble-trained source apportionment approach, and the quantification of source-category-specific human health risk based on online instrumentation and SA methods.

Light absorption enhancement of particulate matters and their source apportionment over the Asian continental outflow site and South Yellow Sea

Light absorption enhancement of black carbon due to the aerosol mixing states is an important parameterization for climate modeling, while emission source contributions to the enhancement factor are unclear. An intensive campaign was conducted simultaneously at a China coastal site (Qingdao city) and maritime sites (South Yellow Sea, SYS) in August and Nov to Dec 2018. The absorption enhancement (E_MAC) of the black carbon was calculated using a two-step solvent dissolution protocol and found 1.96 ± 0.68, 1.64 ± 0.38, and 2.40 ± 0.76 for Qingdao summer (QS), Qingdao autumn (QA), and SYS, respectively. Positive matrix factorization (PMF) model identified six sources of PM_2.5 and E_MAC, which were secondary aerosol (with contribution 27.9% and 29.2%), coal combustion (24.9% and 20.2%), industrial emissions (15.2% and 25.4%), sea salt (6.9% and 9.6%), vehicle emissions (12.1% and 10.9%), and soil dust (13.0% and 4.7%), respectively. These sources increased the absorption of black carbon by a factor of 1.25 ± 0.11 (secondary aerosol), 1.21 ± 0.20 (industrial emissions), 1.17 ± 0.08 (coal combustion), 1.09 ± 0.07 (vehicle emissions), 1.08 ± 0.17 (sea salt), and 1.04 ± 0.10 (soil dust). Based on the correlation between PM and E_MAC source contributions, we estimated that secondary aerosols, industrial emissions, and coal combustion contributed to 74.8% of absorption enhancement at a regional scale in China. The source apportionment for E_MAC offers a new diagnosis for each source regarding aerosol forcing simulation which inputs from the individual emission sector.

Cytotoxic Effects of Water-Soluble Extracts of Coarse and Fine Atmospheric Particulate Matter on Mast Cell Lines

Fine particulate matter (PM_2.5) pollution causes serious health disorders, because PM_2.5 becomes deposited in the tracheobronchial and alveoli regions. In the extrathoracic region, there are more deposits of coarse particulate matter than fine particulates. As adverse health issues caused by coarse particulates have not been well investigated, this study examined the cytotoxicity of water-soluble extracts of both fine (0.05-3 µm, PM_0.05-3) and coarse (> 3 µm, PM_>3) particulates collected from April 2016 to March 2019 in Fukuoka, Japan. Also evaluated were concentrations of NH₄⁺ and SO₄^2-, multi-components of well-known secondary generation substances. The findings revealed that PM_>3 showed stronger cytotoxic effects on mast cell lines than PM_0.05-3. Cytotoxic effects were observed at concentrations of over 15 mM of (NH₄)₂SO₄ and over 30 mM of NH₄Cl. In contrast, Na₂SO₄ caused few cytotoxic effects up to a concentration of 50 mM. The causative substances for this cytotoxicity may not have been NH₄⁺ and SO₄^2- because their PM_>3 concentrations indicating the largest cytotoxic effects were 1 and 0.4 mM, respectively. The cytotoxicities of PM_>3 and PM_0.05-3 were the highest in the first half of FY2016. These cytotoxicities seem to be due to cross-border pollution, although this pollution has been declining in recent years. An increasing trend of cytotoxicity was observed in the second half of FY2018. This study showed that cytotoxicity and particulate concentrations are not always correlated. Thus, we should focus not only on the quantity of atmospheric particulate matter, but also on its quality.

Chemical characteristics and sources of ambient PM2.5 in a harbor area: Quantification of health risks to workers from source-specific selected toxic elements

Samples of ambient PM_2.5 were collected in the Qingdao harbor area between 21 March and May 25, 2016, and analyzed to investigate the compositions and sources of PM_2.5 and to assess source-specific selected toxic element health risks to workers via a combination of positive matrix factorization (PMF) and health risk (HR) assessment models. The mean concentration of PM_2.5 in harbor area was 48 μg m^-3 with organic matter (OM) dominating its mass. Zn and V concentrations were significantly higher than the other selected toxic elements. The hazard index (HI) and cancer risk (R_i) of all selected toxic elements were lower than the United States Environmental Protection Agency (USEPA) limits. There were no non-cancer and cancer risks for workers in harbor area. The contributions from industrial emissions (IE), ship emissions (SE), vehicle emissions (VE), and crustal dust and coal combustion (CDCC) to selected toxic elements were 39.0%, 12.8%, 24.0%, and 23.0%, respectively. The HI values of selected toxic elements from IE, CDCC, SE, and VE were 1.85 × 10^-1, 7.08 × 10^-2, 6.36 × 10^-2, and 3.37 × 10^-2, respectively; these are lower than the USEPA limits. The total cancer risk (R_t) value from selected toxic elements in CDCC was 2.04 × 10^-7, followed by IE (6.40 × 10^-8), SE (2.26 × 10^-8), and VE (2.18 × 10^-8). CDCC and IE were the likely sources of cancer risk in harbor area. The Bo Sea and coast were identified as the likely source areas for health risks from IE via potential source contribution function (PSCF) analysis based on the results of PMF-HR modelling. Although the source-specific health risks were below the recommended limit values, this work illustrates how toxic species in PM_2.5 health risks can be associated with sources such that control measures could be undertaken if the risks warranted it.

Temporal and Spatial Variation of PM2.5 in Xining, Northeast of the Qinghai–Xizang (Tibet) Plateau

PM2.5 was sampled from January 2017 to May 2018 at an urban, suburban, industrial, and rural sites in Xining. The annual mean of PM2.5 was highest at the urban site and lowest at the rural site, with an average of 51.5 ± 48.9 and 26.4 ± 17.8 μg·m−3, respectively. The average PM2.5 concentration of the industrial and suburban sites was 42.8 ± 27.4 and 37.2 ± 23.7 μg·m−3, respectively. All sites except for the rural had concentrations above the ambient air quality standards of China (GB3095-2012). The highest concentration of PM2.5 at all sites was observed in winter, followed by spring, autumn, and summer. The concentration of major constituents showed statistically significant seasonal and spatial variation. The highest concentrations of organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), and water-soluble inorganic ions (WSIIs) were found at the urban site in winter. The average concentration of F− was higher than that in many studies, especially at the industrial site where the annual average concentration of F− was 1.5 ± 1.7 μg·m−3. The range of sulfur oxidation ratio (SOR) was 0.1–0.18 and nitrogen oxidation ratio (NOR) was 0.02–0.1 in Xining. The higher SO42−/NO3− indicates that coal combustion has greater impact than vehicle emissions. The results of the potential source contribution function (PSCF) suggest that air mass from middle- and large-scale transport from the western areas of Xining have contributed to the higher level of PM2.5. On the basis of the positive matrix factorization (PMF) model, it was found that aerosols from salt lakes and dust were the main sources of PM2.5 in Xining, accounting for 26.3% of aerosol total mass. During the sandstorms, the concentration of PM2.5 increased sharply, and the concentrations of Na+, Ca2+ and Mg2+ were 1.13–2.70, 1.68–4.41, and 1.15–5.12 times higher, respectively, than annual average concentration, implying that aerosols were mainly from dust and the largest saltwater lake, Qinghai Lake, and many other salt lakes in the province of Qinghai. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was utilized to study the surface components of PM2.5 and F− was found to be increasingly distributed from the surface to inside the particles. We determined that the extremely high PM2.5 concentration appears to be due to an episode of heavy pollution resulting from the combination of sandstorms and the burning of fireworks.

Chemical characteristics and source apportionment of PM2.5 using PMF modelling coupled with 1-hr resolution online air pollutant dataset for Linfen, China

The chemical species in PM_2.5 and air pollutant concentration data with 1-hr resolution were monitored synchronously between 15 November 2018 and 20 January 2019 in Linfen, China, which were analysed for multiple temporal patterns, and PM_2.5 source apportionment using positive matrix factorisation (PMF) modelling coupled with online chemical species data was conducted to obtain the apportionment results of distinct temporal patterns. The mean concentration of PM_2.5 was 124 μg/m³ during the heating period, and NO₃^- and organic carbon (OC) were the dominant species. The concentrations and percentages of NO₃^-, SO₄^2-, and OC increased notably during the growth periods of haze events, thereby indicating secondary particle formation. Six factors were identified by the PMF model during the heating period, including vehicular emissions (VE: 26.5%), secondary nitrate (SN: 16.5%), coal combustion and industrial emissions (CC&IE: 25.7%), secondary sulfate and secondary organic carbon (SS&SOC: 24.4%), biomass burning (BB: 1.0%), and crustal dust (CD: 5.9%). The primary sources of PM_2.5 on clean days were CD (33.3%), VE (23.1%), and SS&SOC (20.6%), while they were CC&IE (32.9%) and SS&SOC (28.3%) during the haze events. The contributions of secondary sources and CC&IE increased rapidly during the growth periods of haze events, while that of CD increased during the dissipation period. Diurnal variations in the contribution of secondary sources were mainly related to the accumulation and transformation of corresponding gaseous precursors. In comparison, contributions of CC&IE and VE varied as a function of the domestic heating load and peak levels occurred during the morning and evening rush hours. High contributions of major sources (CC&IE and SS&SOC) during haze events originated mainly from the north and south, while high contribution of a major source (CD) on clean days was from the northwest.

Attributable Risk and Economic Cost of Cardiovascular Hospital Admissions Due to Ambient Particulate Matter in Wuhan, China

Although the adverse effects of ambient particulate matter (PM) on cardiovascular disease (CVD) have been previously documented, information about their economic consequence was insufficient. This study aimed to evaluate the attributable risk and economic cost of cardiovascular hospitalizations due to ambient PM. Data of CVD hospitalizations and PM concentrations from 1 January 2015 to 31 December 2017 were collected in Wuhan, China. A generalized additive model was applied to quantify the PM-attributable CVD hospitalizations, and total attributable hospitalization costs were calculated via multiplying the total attributable cases by the case-average hospitalization costs. A total of 45,714 CVD hospitalizations were included in this study. The results showed that a 10 µg/m3 increase in PM2.5 and PM10 concentrations at lag7 day, respectively, contributed to a 1.01% (95% confidence interval: 0.67-1.34) and 0.48% (0.26-0.70) increase in CVD hospitalizations. During the study period, 1487 and 983 CVD hospitalizations were attributable to PM2.5 and PM10, equaling an economic cost of 29.27 and 19.34 million RMB (1 RMB = 0.1424 USD), respectively, and significant differences in PM-attributable hospitalizations and economic burden were found between gender and age groups. Our study added evidence in heavily polluted megacities regarding the increased health risk and economic cost of CVD hospitalizations associated with ambient particulate pollution.

Health benefits on cardiocerebrovascular disease of reducing exposure to ambient fine particulate matter in Tianjin, China

With the development of the industrialization level in China, high concentrations of fine particulate matter (≤ 2.5 μg/m³ in aerodynamic diameter (PM_2.5)) could have a great impact on the health of the population. Our study is to quantify the health benefits on cardiocerebrovascular disease of reducing exposure to PM_2.5 in Tianjin, China. We obtained the data on cardiovascular disease (CVD), ischemic heart disease (IHD), and cerebrovascular disease (CD) mortalities to quantify the association between CVD, CD, and IHD mortalities and PM_2.5 and calculate health and economic benefits when the annual average concentration of PM_2.5 was reduced to National Ambient Air Quality Standard (NAAQS) and World Health Organization (WHO) guidelines by using our concentration response (C-R) functions. There were 435.22 (95% CI 253.86 to 616.57) all-cause, 130.22 (95% CI 66.34 to194.09) IHD, and 204.07 (95% CI 111.66 to 296.47) CD deaths attributed to PM_2.5 and the economic benefits obtained by preventing all-cause, IHD, and CD mortalities were equivalent to be 2.79%, 0.83%, and 1.31% of Baodi's GDP in Tianjin in 2017, respectively. PM_2.5 concentration was positive with all-cause, IHD, and CD mortalities in rural, suburban, and urban area of Tianjin, China. Meanwhile, the number of avoidable deaths and economic cost of reducing PM_2.5 concentrations to NAAQS and WHO guidelines was highest in the rural area.

Research Progress of HP Characteristics, Hazards, Control Technologies, and Measures in China after 2013

In recent years, hazy weather (hazy weather (HW) has frequently invaded peoples’ lives in China, resulting in the disturbance of social operation, so it is urgent to resolve the haze pollution (HP) problem. A comprehensive understanding of HP is essential to further effectively alleviate or even eliminate it. In this study, HP characteristics in China, after 2013, were presented. It was found that the situation of HP is getting better year by year while it has been a pattern of high levels in the north and low levels in the south. In most regions of China, the contribution of a secondary source for HP is relatively large, and that of traffic is greater in the regions with rapid economic development. Hazards of HP were then summarized. Not only does HP cause harm to human health, but it also has effects on human production and quality of life, furthermore, property and atmospheric environment cannot be ignored. Next, the source and non-source control technologies of HP were first reviewed to recognize the weakness of HP control in China. This review provides more systematic information about HP problems and the future development directions of HP research were proposed to further effectively control HP in China.