Workshop 1: Air Pollution and Human Health

Prof. Haidong KAN

Professor
School of Public Health, Fudan University, China

Topic:
Air pollution and daily mortality: from PAPA to MCC studies

Date: 6 July 2023
Time: 14:30 – 15:00

Abstract:
The speaker will give an overview on the health effects of air pollution on mortality during the past decades, and discuss the challenges and future research directions.  The Public Health and Air Pollution in Asia (PAPA) study and Multi-Country, Multi-City (MCC) study will be extensively discussed.

Prof. Guangbo QU

Professor
Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, China

Topic:
Identification of aryl hydrocarbon receptor agonists from real environmental samples based on effect-directed analysis

Date: 6 July 2023
Time: 15:00 – 15:20

Abstract:
Combining the advances of biological assay, fractionation with chromatography, and mass spectrum analysis, effect-directed has been widely applied for identifying key toxicants in environmental samples. In this study, samples from contaminated regions have been extracted with accelerated solvent extraction. Aryl hydrocarbon receptor (AhR) agonic potency in the extracts was measured with a cell-based genetic reporter assay that utilizes the luciferase reporter gene. The positive samples with high potency were then fractionated using an established fractionation method.
The key toxicants in active fractions have been identified using gas or liquid chromatography coupled with high-resolution mass spectrometry (Q Extractive). Trace Finder (v 5.0, Thermo Scientific, USA) was used for data acquisition and processing. We have identified the above thirty AhR agonists in the positive fractions. The major contributor to AhR activity in these sediment samples was petroleum product combustion and biomass combustion. Fractions were collected for unknown AhR agonist chemical identification. The contributions of potent AhR agonists to adverse outcomes have been discussed. More fractionation methods are required to seek the source of measured toxicity induced by the extracts from real environmental samples.

Prof. Maosheng YAO

Professor
College of Urban and Environmental Sciences, Peking University, China

Topic:
“Smoke Detector” Science for Aerosol Exposure Health Effects

Date: 6 July 2023
Time: 15:20 – 15:40

Abstract:
Aerosol exposure represents a significant health threat to human health. It is often difficult to detect and feel when it is harming the health. Traditional approach involves sampling, offline component and toxicity analysis studies, failing to provide a timely protection to the health. Toward this problem, in our laboratory we have discovered that living system on cell, animal and human levels would emit a distinctive profile of volatile organic components (VOC) upon specific aerosol pollutant exposure within a very short of time period. Together with machine learning, we were able to distinguish between different aerosol exposures. For example, SARS-CoV-2 exposure also resulted in different profile of VOCs, including elevated isopropanol and decreased acetone levels. Using PMs from various cities, we have shown that cells also emit different profiles of VOCs upon the exposure, thus implying different health effects. Further, using a rat together with an array of breath-borne biomarker sensors we were able to real-time monitor health effects of air pollution, including those hazy days. Development of “Smoke Detector” for aerosol exposure health effects would enable humans to be able to real-time “see and feel” the aerosol harm, and thus holds a great promise in revolutionizing the studies and the instrumentation for environmental aerosol and health.

Prof. Daqiang YIN

Professor
College of Environmental Science and Engineering, Tongji University, China

Topic:
Mixed metal components facilitate PM_2.5 to induce CCR5-mediated neuroinflammation in mouse olfactory bulb

Date: 6 July 2023
Time: 15:40 – 16:00

Abstract:
Particulate matters, especially PM_2.5, can invade the central nervous system (CNS) via the olfactory pathway to induce neurotoxicity. Olfactory bulb (OB) is the key component integrating immunoprotection and olfaction processing in the pathway and is necessarily involved in the relevant health outcomes. Here we show that microglial CCR5 is the target of environmentally relevant PM_2.5 in OB to trigger neuroinflammation and then neural injuries. Mechanistically, PM_2.5-induced CCR5 upregulation results in the M1-dominant paradigm of microglial activation, which subsequently activates TLR4-NF-κB neuroinflammation signaling and induces Alzheimer’s-like pathologies (e.g., Aβ deposition and disruption of the blood-brain barrier). Although the biosynthesis of Aβ is not affected by PM_2.5, the clearance process is significantly delayed, which can be the possible reason the Aβ deposition. Furthermore, we specifically highlight that manganese and lead on PM for2.5 are the main contributors to the CCR5 activation in synergy with aluminum. Our results uncover the causes of PM_2.5-induced neuroinflammation and identify the principal neurotoxic components, which can provide new insight into efficiently diminishing the adverse health effects of PM_2.5.

Prof. Gan ZHANG

Director of the State Kay Laboratory of Organic Geochemistry Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, China

Topic:
Unravelling the polyaromatic continuum in atmospheric particles

Date: 6 July 2023
Time: 16:15 – 16:45

Abstract:
Polyaromatic organic matters (POMs) exist in ambient aerosol as a continuum spanning from small polycyclic aromatic compounds (PACs) to black carbon (BC), and appears in from water soluble, organic-solvent soluble to insoluble fractions. Numerous studies revealed that POMs are key contributors to both the light absorption and toxicity of atmospheric fine particles. A single measurement of priority polycyclic aromatic hydrocarbons (EPA-PAHs) could not afford the quantification of PACs in different chemical fractions of air particle. We adapted the BPCA (benzene polycarboxylic acid) method to address this problem. POMs are oxidized and broken down to individual benzene rings substituted with 2-6 carboxylic groups, depending on the extent of vicinal carbon atoms (i.e., BPCAs), in nitric acid under high temperature and pressure. The BPCAs are then quantified and translated to the POM concentration. We further developed compound-specific isotope analysis/radiocarbon analysis (CSIA/CSRA) methods for tracking the sources of POMs in different chemical fractions. It was found that, in the SRM1649b reference standard, the EPA-PAHs account for only less than 1% of low-polarity PACs quantified by BPCA method, and the abundance of low- and high-polarity PACs was comparable. Source apportionment of POMs using CSRA of BPCAs showed varied contributions of fossil and contemporary sources among bulk aerosols and water-soluble, methanol-soluble fractions of ambient aerosols from a megacity of southern China. The BPCA-based method is shown to be a useful tool for unravelling the POM continuum in air particles.

Prof. Xiangdong LI

Director of Research Institute for
Sustainable Urban Development
Dean of Faculty of Construction and Environment
Chair Professor of Environmental Science and Technology
Ko Jan Ming Professor in Sustainable Urban Development,
The Hong Kong Polytechnic University, Hong Kong

Topic:
Unravelling the Black Box between Air Pollution and Public Health for Transformative Air Quality Management

Date: 6 July 2023
Time: 16:45 – 17:05

Abstract:
Dominated by fine particulate matter (PM_2.5), air pollution is the world’s greatest environmental health risk factor in both developed and developing economies. Each year, outdoor PM_2.5 pollution causes millions of premature deaths worldwide and costs the global economy US$225 billion in lost labour income. Many regulatory bodies, including the Hong Kong Environmental Protection Department, benchmark against the guideline values of the World Health Organization (WHO) (e.g., mass concentration of PM_2.5, µg m^-3) to protect public health. However, evidence is mounting on the unequal health effects at equal mass concentrations of PM_2.5. This is primarily because PM_2.5 is a cocktail of components from a mix of sources. Not all components and sources are equally important in toxicity contribution to the combined impact of what people breathe in different parts of the world. Controlling the sources of health-relevant but not necessarily mass-dominating fractions of PM_2.5 would be a more effective option than managing the entire PM_2.5 mass. Identifying the toxic components and their associated sources responsible for PM_2.5 health effects represents a major scientific challenge prior to the making of policy. Owing to 21st century advancements in toxicology and molecular epidemiology, it is hoped that this long-standing puzzle can be resolved by a high-throughput in vitro effect-directed analysis and in silico mixture-toxicity predictions along with optimal in vivo and epidemiological validations. We will introduce our study design and report the progresses so far in the first year.

Dr Linwei TIAN

Associate Professor
School of Public Health, The University of Hong Kong, Hong Kong

Topic:
Gaseous pollutants and health: one wind a day keeps the doctor away?

Date: 6 July 2023
Time: 17:05 – 17:25

Abstract:
The current air quality standards set upper bounds for air pollutant concentrations to protect public health. Can we envision some future air quality standards set also lower bounds to ensure minimal requirements of certain gaseous compounds in the air for public health benefits? It sounds a silly question, but research is warranted. Being a well-known toxicant at high level, exogenous carbon monoxide (CO) has been proved of its beneficial anti-inflammatory effects at low concentrations and therefore therapeutic applications in critical care medicine. Sulfur dioxide (SO₂) is probably another gasotransmitter in the body for its physiological functions such as maintaining normal vascular tone and blood pressure whereas the potential health effect of extremely low ambient SO₂ is uncertain. Ambient ozone (O₃) increases the risk of COPD exacerbation but it may decrease the risk of influenza. Daily time series data from Hong Kong and USA are analysed by a combination of three distinct methods for better triangulation of causal evidence on three pairs of relationships: CO effect on sepsis ('blood poisoning'), SO₂ effect on ischemic stroke, and O₃ effect on influenza. Preliminary findings are to be presented.

Prof. Kin Fai HO

Associate Professor
Earth System Science Programme,
The Chinese University of Hong Kong, Hong Kong

Head of Graduate Division
JC School of Public Health and Primary Care, Hong Kong

Topic:
Photochemical oxidation of gasoline vehicle exhaust – volatile organic compound emissions and secondary organic aerosol formation

Date: 6 July 2023
Time: 17:25 – 17:45

Abstract:
The emissions before and after atmospheric oxidation from gasoline vehicles were characterized under different driving conditions. The organic aerosol mass concentrations showed substantial increase (~ 7.6-10.8 times) after ageing process, implying that vehicular emissions were an important source of aged organic aerosol. The total quantified organic species mass concentrations in aged samples ranged from 77.7 to 480.5 ng m^-3 under different test conditions. The emission factors of VOCs were higher under idling condition compared to the other driving modes for all selected vehicles. High VOCs emissions could potentially lead to high aged organic compounds formation inside the Potential Aerosol Mass (PAM) reactor under idling condition. The vehicle with latest year of manufacture in Euro 5 standard could pose lower primary emissions of organic substances. High aged/fresh emission ratios (A/F) (> 20) of phthalic acid, 2,3-dihydroxy-4-oxopentanoic acid, selected dicarboxylic acids and motor emission (ME) markers were secondary produced through aging processes, suggesting possible formation products from the photooxidation reaction of VOC precursors, e.g. naphthalene and toluene. In most cases, the bioreactivity induced by the aged PM samples is significantly higher than the fresh samples, which suggested that the aged organic compounds from oxidation of gasoline exhaust can play an important role in PM-induced oxidative stress and inflammation in Hong Kong. The stepwise regression analysis suggested that n-alkane and alkenoic acid are major contributors to the increase in lactate dehydrogenase (LDH) levels in the fresh samples, polycyclic aromatic hydrocarbons (PAHs) and monocarboxylic acid are for the aged samples.

Dr Guojun HE

Associate Professor
Economics and Management & Strategy, University of Hong Kong, Hong Kong

Director
ESG Research Institute, University of Hong Kong, Hong Kong

Associate Director
Institute of China Economy, University of Hong Kong, Hong Kong

Topic:
Quasi-Experimental Methods for Air Pollution-Health Studies

Date: 6 July 2023
Time: 17:45 – 18:05

Abstract:
The paper reviews the applications of quasi-experimental methods in air pollution-health studies, which are drawn intensely from the economics literature. It starts by discussing various confounding factors that are commonly seen in associational studies, then gives examples of how quasi-experimental designs can address these issues. Several widely-used quasi-experimental inference methods are reviewed, with a particular focus on empirical findings from China. The paper concludes by discussing how quasi-experimental designs can help isolate the impact of PM toxicity on population health, which essentially requires researchers to hold PM concentrations constant and vary the degrees of toxicity.

Prof. Jianzhen YU

Chair Professor
Department of Chemistry Division of Environment and Sustainability
Director of Atmospheric Research Center
Hong Kong University of Science and Technology, Hong Kong

Topic:
Building mechanistic linkages between PM_2.5-induced oxidative potential and chemical composition

Date: 7 July 2023
Time: 09:00 – 09:20

Abstract:
Inhaled ambient fine particulate matter (PM_2.5) contains transition metals (TMs) that possess excellent catalytic properties and can contribute to the formation of multiple reactive oxidative species (ROS) in human lung lining fluid. These ROS include ·O₂, H₂O₂, and ·OH. Additionally, ambient organics, particularly humic-like substances (HULIS), can complex with TM ions as ligands, facilitating electron transfer in TM-induced ROS generation. This leads to an increase in the adverse oxidative potential (OP) to the human body. Several studies have measured the OP of ambient or lab-prepared samples using different assays and generated equations between OP and chemical concentration using multiple regression models. However, these equations could not explain the catalytic effects of TMs and organics in OP formation processes as they are purely empirical and no underlying chemical reaction mechanisms were proposed.
We assessed the OP of lab-prepared TM samples under different conditions using the ascorbic acid (AA) assay and the glutathione (GSH) assay. By analyzing the OP dependence on TM concentration, we proposed a TM-AA/TM-GSH complex as the major intermediate and a quasi-Michaelis-Menten mechanism to quantitatively explain the nonlinear dose-response in TM-induced AA/GSH depletion. Our proposed reaction mechanisms also provide a clear understanding of the ·OH formation in the AA assay. We also observed a synergistic effect between metals and ambient HULIS. Our work proposes a detailed chemical mechanism for TM-catalyzed OP formation, which quantitatively links TM concentration and OP. This provides valuable information and reference for OP calculation and modeling based on the chemical composition of ambient PM_2.5.

Prof. Hai GUO

Professor
Department of Civil and Environmental Engineering,
The Hong Kong Polytechnic University, Hong Kong

Topic:
Cytotoxicity of fine particulate matter in different locations in Hong Kong

Date: 7 July 2023
Time: 09:20 – 09:40

Abstract:
Fine particulate matter (PM_2.5) has been identified as a major air pollutant with irreversible impacts on humans. In this study, the chemical and toxicological characteristics of PM_2.5 in residential and rural background environments were investigated. Sampling was performed in an apartment, at a mountainous site (Tai Mo Shan, TMS) and a coastal background site (Hok Tsui, HT), respectively. PM_2.5 collected on quartz fiber filters were weighed and extracted, followed by organic compound analysis and in vitro cellular testing. Toxicity of PM_2.5 in the apartment and at the rural background environments was evaluated by tumour necrosis factor-alpha (TNF-a) and interleukin 6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), malondialdehyde (MDA), 8-hydroxy-2’-deoxyguanosine (8-OHdG) and lactic dehydrogenase (LDH). In the residential environment, IL-6, MCP-1, and MDA levels were comparable among general household activities, intensive cooking, and smoking. Concentrations of phthalates, methyl palmitate, Flexol 4GO, Flexol 3GO and 2-Pentadecanone, 6,10,14-trimethyl which were all plasticizers generated from residential background emissions, were found to have strong positive correlation (p < 0.05, r = 0.79 - 0.93) with the biomarker MDA, indicating that attention should be paid to health risks of accumulation effects of toxic background plasticizers. At the two rural background sites, DNA adduct 8-OHdG concentrations of PM_2.5 were found to be significantly higher than control levels (p < 0.0001). PM_2.5 collected on days influenced by the northeast continental airmass at HT and TMS showed higher levels of 8-OHdG than the eastern coastal air. The 8-OHdG levels in marine air were comparable to control group and about half the levels of air from the northeast continent and the eastern coast. No strong correlations were found between biomarkers and measured organic compounds at the rural background sites. C5 compounds in TMS samples presented a moderate positive correlation with 8-OHdG concentration (p < 0.05, r = 0.49). The findings indicate that the cytotoxicity of PM_2.5 in different microenvironments is unequal.

Dr Ling JIN

Assistant Professor
Department of Civil and Environmental Engineering and Department of Health Technology and Informatics,
The Hong Kong Polytechnic University, Hong Kong

Topic:
What are driving the evolving toxicity of particulate matter generated from residential biomass burning?

Date: 7 July 2023
Time: 09:40 – 10:00

Abstract:
Residential biomass burning releases substantial amounts of pollutants, such as polycyclic aromatic hydrocarbons (PAHs) and black carbon (BC), posing significant health risks in rural areas of China and other countries alike. Current stove improvements focusing on thermal efficiency do not necessarily lead to reduced health risks. A better understanding of toxicity-contributing pollutants and their formation mechanisms is urgently needed. We conducted laboratory combustion experiments using three biomass types under different temperatures. Particulate matter (PM) samples were collected for chemical and toxicity characterizations. Toxic potency per unit mass of PM increased from 400℃, peaked at 600℃, and then decreased at 800℃. PAH concentrations in PM also increased with temperature, peaking at 800℃, which means that PAHs alone could not explain the declining toxic potency of PM at high temperatures. Non-target screening revealed primary biomass pyrolysis products dominated the organic emissions from low-temperature combustion (400℃) and heterocyclic aromatic compounds were intensely emitted during medium-temperature combustion (600℃). As the temperature increased, the aromatic compounds aggregated and transformed into more stable PAHs. The decrease in heterocyclic aromatic compounds may be a key reason for reduced PM toxicity at high temperatures (800℃). Further research is necessary to identify toxic components underlying the evolving PM toxicity during combustion. The full outcomes of the study will inform effective strategies for reducing harmful emissions from residential biomass burning.

Dr Sonata YAU

Associate Professor
Department of Rehabilitation Sciences, The Hong Kong Polytechnic University

Adjunct Associate Professor
Division of Medical Science, University of Victoria (British Columbia), Canada

Topic:
Chronic exposure of PM_2.5 induces impairment in mood and working memory in association with aberrant adult-born neurons in the hippocampus

Date: 7 July 2023
Time: 10:00 – 10:20

Abstract:
Air pollution poses a significant threat to human health as 90% of the global population breathes polluted air, according to a report by the World Health Organization (WHO). This has resulted in the deaths of 7 million people worldwide per year due to exposure to pollutants such as Nox, SO₂, O₃, particulate matter (PM), and organic metals, with particulate matter being of particular concern. The small size of PM_2.5 particles allows them to penetrate the respiratory tract, leading to inflammation, oxidative stress, and harmful effects on the nervous system. The effects of PM_2.5 on respiratory and cardiovascular health are known, including breathing difficulties, chest tightness, coughing, and cardiovascular mortality and morbidity. However, less is known about the detrimental effects of air pollution on cognitive functioning and mental health. Our research focuses on the hippocampus as its continuous development of new neurons the dentate gyrus (DG) of the hippocampus, a key brain region that regulates mood regulation, and learning and memory. We exposed adult mice with either (A) artificial lung fluid as control group or (B) PM_2.5 exposure as treatment group with intratracheal instillation of PM_2.5 at the dosage of 2.5 µg/ul every other 3 days continuously for three weeks. Our pilot data showed that PM_2.5 treatment increased immobility time and decreased total time spent in the center of the open field, suggesting an increase in depression-like and anxiety-like behavior. PM_2.5 treatment also decreased exploration index to novel object in a working memory test, indicating memory impairment. Quantification of doublecortin (adult born immature neuron) and Ki 67 (proliferating cells) positive cells in the DG using immunostaining showed a decreasing trend in number of positive cells in the PM_2.5 treatment group when compared to the control group, indicating that exposure to PM_2.5 may result in a decrease in adult neurogenesis. The pilot data has suggested that decrease in adult neurogenesis could be linked to PM_2.5-induced mood and memory impairment.

Dr Daihai HE

Associate Professor
Department of Applied Mathematics, The Hong Kong Polytechnic University, Hong Kong

Topic:
Modelling COVID-19 vaccine breakthrough infections in highly vaccinated Israel

Date: 7 July 2023
Time: 10:20 – 10:40

Abstract:
In August 2021, a major wave of the SARS-CoV-2 Delta variant erupted in the highly vaccinated population of Israel. The transmission advantage of the Delta variant enabled it to replace the Alpha variant in approximately two months. The outbreak led to an unexpectedly large proportion of breakthrough infections (BTI)–a phenomenon that received worldwide attention. Most of the Israeli population, especially those aged 60+, received their second dose of the vaccination four months before the invasion of the Delta variant. Hence, either the vaccine induced immunity dropped significantly or the Delta variant possesses immunity escaping abilities, or both. In this work, we model data obtained from the Israeli Ministry of Health, to help understand the epidemiological factors involved in the outbreak. We propose a mathematical model that captures a multitude of factors, including age structure, the time varying vaccine efficacy, time varying transmission rate, BTIs, reduced susceptibility and infectivity of vaccinated individuals, protection duration of the vaccine induced immunity, and the vaccine distribution. We fitted our model to COVID-19 cases among the vaccinated and unvaccinated, for <60 and 60+ age groups, and quantified the transmission rate, the vaccine efficacy over time and the impact of the third dose booster vaccine. We estimated that approximately 4.03 million infective cases (95%CI 3.19, 4.86) were prevented by vaccination overall, and 1.22 million infective cases (95%CI 0.89, 1.62) averted by the booster.

Prof. Yu HUANG

Head of Department of Biomedical Sciences
Chair Professor of Biomedical Sciences and Vascular Biology
Jeanie Hu Professorship in Biomedical Sciences
City University of Hong Kong, China

Topic:
Pollutants and vascular and metabolic dysfunction

Date: 7 July 2023
Time: 11:00 – 11:20

Abstract:
Healthy vascular endothelium is the critical player in maintaining vascular homeostasis through releasing several vaso-protective substances called endothelium-derived relaxing factors (EDRFs) such as nitric oxide. By contrast, loss of EDRFs in diseased endothelial cells unmasks the vaso-harmful impact of endothelium-derived contracting factors (EDCFs) such as vaso-constrictive prostanopids. Such disrupted balance between EDRFs and EDCFs in endothelium is referred to endothelial dysfunction, an important initial pathological event that triggers pathogenesis of vascular diseases in hypertension and diabetes. Increased production of reactive oxygen species (ROS) or raised oxidative stress in the vascular wall is probably the key factor to inactivate nitric oxide within endothelial cells. Understanding and targeting the sources of ROS is effective to increase the bioavailability of endothelium-derived nitric oxide, thus improving endothelial function in cardio-metabolic diseases. Air pollutants increase oxidative stress in blood vessels and impair endothelial function, which may account for the pathogenic involvement of air pollutants in cardiovascular and metabolic diseases.

Dr Tong LIU

Assistant Professor
Lee Kuan New School of Public Policy, National University of Singapore Research, Singapore

Topic:
Feel the burn: Mental and behavioral responses to air pollution in China

Date: 7 July 2023
Time: 11:20 – 11:40

Abstract:
This paper examines the causal impacts of air pollution from agricultural straw burning on mental health measured by Center for Epidemiologic Studies Depression Scale (CES-D) in China in 2013 and 2015. Summer straw burning primarily elevates particulate matter (PM) concentrations in Chinese cities, which makes urban non-farmers more depressed. Conditional on individual fixed effects and weather conditions, if the number of straw fires detected by satellite increases by 10 points or 1 standard deviation (SD) in a prefecture, the mental health status of urban non-farmers will be worsened by 1.28 units (0.25 SD) or 0.17 units (0.03 SD). A 10 µg/m3 or 1-SD increase in PM10 will impair mental health by 0.27 units (0.05 SD) or 0.73 units (0.14 SD). A back-of-the-envelope calculation shows that the monetary mental health losses due to straw burning can be as large as 2.6 billion USD in urban China. In contrast, rural farmers feel happier when there are more straw fires, especially local fires, revealing the agricultural gains from straw burning for the farmers. In response to straw burning, Chinese citizens adopt avoidance behaviors, such as searching and purchasing anti-haze masks and air filters in autumn but not in summer. This study is among the first to document a causal impact of air pollution on mental health, highlighting the urgency of restraining straw burning in China and other agrarian regions worldwide. The evidence further helps explain the failure of the command-and-control regulations which ban straw burning but neglect the potential losses to the farmers, calling for incentive-based policies such as subsidizing straw recycling to improve the welfare of both rural and urban residents.