How far can air pollution affect tourism in China? Evidence from panel unconditional quantile regressions.

Previous studies provide empirical evidence for the connection between air pollution and tourism. However, many of them take the nexus as a linear one. It remains unexplored whether any thresholds are required for the nexus to materialize. This study systematically investigates whether PM2.5 concentrations-an essential indicator of air pollution-affect tourism in China at various tourism development levels. We analyze 284 Chinese cities from 2008 to 2018 using the Unconditional Quantile Regression method. Our statistical results reveal that air pollution positively influences tourism (regarding tourist visits and tourism revenue) in areas with low tourism development levels. However, a complex correlation between air pollution and tourism emerges when tourism development has reached a certain level. The correlation is initially negative, then positive, and finally disappears. But, the overall correlation remains negative. The effects of the interaction between air pollution and tourism resources on tourism are inverted U-shaped, implying that tourism resources can mitigate the negative effects of air pollution on tourism only when tourism development has reached a certain level. Based on the above findings, the associated policy implications are discussed.

Assessing local and transboundary fine particulate matter pollution and sectoral contributions in Southeast Asia during haze months of 2015-2019.

While previous studies have investigated haze events over Southeast Asia (SEA), local and transboundary contributions of various emission sources to haze months over the entire SEA have yet to be assessed comprehensively and systematically. We utilized the Particle Source Apportionment Technique (PSAT) to quantify the spatial local, transboundary, and sectoral contributions to PM2.5 over SEA during the haze months of 2015-2019. Results show that local emission contributions accounted for 56.1 % ~ 94.2 % of PM2.5 in Indonesia, Philippines, Vietnam, and Thailand. Transboundary contributions (23.1 % ~ 57.6 %) from Indonesia notably influenced maritime SEA. Vietnam (15.6 % ~ 39.1 %) and super-regional (17.0 % ~ 34.3 %) contributions outside the SEA exerted remarkable impacts on mainland SEA. Among different sectors, fire emissions contributed the most to PM2.5 over maritime SEA (23.0 % ~ 68.6 %) during the studied haze months, whereas residential and other emissions were the main contributors to mainland SEA (27.2 % ~ 36.7 %). Regarding the source species, primary PM2.5 accounted for the majority of PM2.5. VOC and SO2 composed most of the secondary PM2.5 due to massive VOC emissions in the region and the priority reaction of NH3 with sulfuric acid (H2SO4) to form ammonium sulfate. Besides, the intensified haze months in Oct 2015 and Sep 2019 were characterized by more intensive fire emissions in the region and the climatic variability-induced meteorological effects that provided favorable condition for transboundary air pollution (56.9 % and 44.9 %, respectively, for maritime SEA, as well as 46.0 % and 37.7 %, respectively, for mainland SEA in the two studied haze months). The haze months can be attributed to the notable drought conditions amidst global climatic phenomena such as El Niño and positive Indian Ocean Dipole (IOD) in Oct 2015 and Sep 2019, respectively.

Association between ambient air pollutants and upper respiratory tract infection and pneumonia disease burden in Thailand from 2000 to 2022: a high frequency ecological analysis.

BACKGROUND: A pertinent risk factor of upper respiratory tract infections (URTIs) and pneumonia is the exposure to major ambient air pollutants, with short term exposures to different air pollutants being shown to exacerbate several respiratory conditions. METHODS: Here, using disease surveillance data comprising of reported disease case counts at the province level, high frequency ambient air pollutant and climate data in Thailand, we delineated the association between ambient air pollution and URTI/Pneumonia burden in Thailand from 2000 - 2022. We developed mixed-data sampling methods and estimation strategies to account for the high frequency nature of ambient air pollutant concentration data. This was used to evaluate the effects past concentrations of fine particulate matter (PM2.5), sulphur dioxide (SO2), and carbon monoxide (CO) and the number of disease case count, after controlling for the confounding meteorological and disease factors. RESULTS: Across provinces, we found that past increases in CO, SO2, and PM2.5 concentration were associated to changes in URTI and pneumonia case counts, but the direction of their association mixed. The contributive burden of past ambient air pollutants on contemporaneous disease burden was also found to be larger than meteorological factors, and comparable to that of disease related factors. CONCLUSIONS: By developing a novel statistical methodology, we prevented subjective variable selection and discretization bias to detect associations, and provided a robust estimate on the effect of ambient air pollutants on URTI and pneumonia burden over a large spatial scale.

Assessing the Spatiotemporal Characteristics, Factor Importance, and Health Impacts of Air Pollution in Seoul by Integrating Machine Learning into Land-Use Regression Modeling at High Spatiotemporal Resolutions.

Previous studies have characterized spatial patterns of air pollution with land-use regression (LUR) models. However, the spatiotemporal characteristics of air pollution, the contribution of various factors to them, and the resultant health impacts have yet to be evaluated comprehensively. This study integrates machine learning (random forest) into LUR modeling (LURF) with intensive evaluations to develop high spatiotemporal resolution prediction models to estimate daily and diurnal PM2.5 and NO2 in Seoul, South Korea, at the spatial resolution of 500 m for a year (2019) and to then evaluate the contribution of driving factors and quantify the resultant premature mortality. Our results show that incorporating the random forest algorithm into our LUR model improves the model performance. Meteorological conditions have a great influence on daily models, while land-use factors play important roles in diurnal models. Our health assessment using dynamic population data estimates that PM2.5 and NO2 pollution, when combined, causes a total of 11,183 (95% CI: 5837-16,354) premature mortalities in Seoul in 2019, of which 64.9% are due to PM2.5, while the remaining are attributable to NO2. The air pollution-attributable health impacts in Seoul are largely caused by cardiovascular diseases including stroke. This study pinpoints the significant spatiotemporal variations and health impact of PM2.5 and NO2 in Seoul, providing essential data for epidemiological research and air quality management.

Long-term trends of atmospheric hot-and-polluted episodes (HPE) and the public health implications in the Pearl River Delta region of China.

Air pollution and extreme heat have been responsible for more than a million deaths in China every year, especially in densely urbanized regions. While previous studies intensively evaluated air pollution episodes and extreme heat events, a limited number of studies comprehensively assessed atmospheric hot-and-polluted-episodes (HPE) - an episode with simultaneously high levels of air pollution and temperature - which have potential adverse synergic impacts on human health. This study focused on the Pearl River Delta (PRD) region of China due to its high temperature in summer and poor air quality throughout a year. We employed geostatistical downscaling to model meteorology at a spatial resolution of 1 km, and applied a machine learning algorithm (XGBoost) to estimate a high-resolution (1 km) daily concentration of particulate matter with an aerodynamic diameter ≤2.5 µm (PM2.5) and ozone (O3) for June to October over 20 years (2000-2019). Our results indicate an increasing trend (∼50%) in the frequency of HPE occurrence in the first decade (2000-2010). Conversely, the annual frequency of HPE occurrence reduced (16.7%), but its intensity increased during the second decade (2010-2019). The northern cities in the PRD region had higher levels of PM2.5 and O3 than their southern counterparts. During HPEs, regional daily PM2.5 exceeded the World Health Organization (WHO) and Chinese guideline levels by 75% and 25%, respectively, while the O3 exceeded the WHO O3 standard by up to 69%. Overall, 567,063 (95% confidence interval (CI): 510,357-623,770) and 52,231 (95%CI: 26,116-78,346) excessive deaths were respectively attributable to exposure to PM2.5 and O3 in the PRD region. Our findings imply the necessity and urgency to formulate co-benefit policies to mitigate the region's air pollution and heat problems.

A new approach for health-oriented ozone control strategy: Adjoint-based optimization of NOx emission reductions using metaheuristic algorithms.

While levels of particulate matters in the Pearl River Delta Region (PRD) show a significant reduction, ozone (O3) has an opposite increasing trend, becoming the critical air quality target in this decade. Emission control strategies are typically formulated sector by sector, spatial variability in emissions reductions and health impacts of air pollutants may not be taken into account, affecting the overall effectiveness of control strategies. This study proposes an adjoint-based optimization framework to facilitate health-oriented O3 control over PRD. The location-specific adjoint sensitivity coefficients, which reflect the spatiotemporal influences from emissions of nitrogen dioxide (NOx) on O3 health impacts, are combined with metaheuristic algorithms to minimize the O3-related premature mortalities over receptor regions. Using the proposed optimization methodology, the regional O3 health benefits under current emission reduction policy can be increased by 16-27%. The results show that relatively larger NOx emissions reductions occurred at highly developed and populated areas. Particularly, significant reductions in NOx emissions are observed at Shenzhen and urban Guangzhou. Furthermore, implementing regional NOx emissions abatement has advantages to achieve an overall O3 health benefits for all cities. The interregional influences of NOx emissions abatement between cities indicate a promising strategy of health-oriented O3 control in PRD.

Mapping ozone source-receptor relationship and apportioning the health impact in the Pearl River Delta region using adjoint sensitivity analysis.

While fine particulate matters are decreasing in the Pearl River Delta (PRD) region, the regional ozone (O3) shows an increasing trend that affects human health, leading to an urgent need for scientific understanding of source-receptor relationship between O3 and its precursor emissions given the changing background composition. We advanced and applied an adjoint air quality model to map contributions of individual O3 precursor emission sources [nitrogen oxides (NOx) and volatile organic compound (VOC)] at each location to annual regional O3 concentrations and to identify the possible dominant influential pathways of emission sources to O3 at different spatiotemporal scales. Additionally, we introduced the novel adjoint sensitivity approach to assess the relationship between precursor emissions and O3-induced premature mortality. Adjoint results show that Shenzhen was a major source contributor to regional O3 throughout all seasons, of which 49.4% (3.8%) were from its NOx (VOC) emissions. Local emissions (within PRD) contributed to 83% of the regional O3 whereas only ~54% of the estimated ~4000 regional O3-induced premature mortalities. The discrepancy between these two contributions was because O3-induced mortalities are dependent on not only O3 concentration, but incident rate and population density. We also found that a city with low O3-induced mortalities could have significant emission contributions to health impact in the region since the transport pathways could be through transport of local O3 or through transport of O3 precursors that form regional O3 thereafter. It is therefore necessary to formulate emission control policies from both air quality and public health perspectives, and it is also critical to have better understanding of influential pathways of emission sources to O3.

Real-Time Monitoring of the Effects of Personal Temperature Exposure on the Blood Oxygen Saturation Level in Elderly People with and without Chronic Obstructive Pulmonary Disease: A Panel Study in Hong Kong.

Few studies have investigated the short-term effect of personal temperature exposure on blood oxygen saturation (SpO2). We conducted this longitudinal panel study with real-time monitoring of SpO2 and environmental exposure for 3 continuous days for 20 patients with chronic obstructive pulmonary disease (COPD) and 20 healthy volunteers in Hong Kong, to explore the time course (from minutes to hours) of change in SpO2 in response to temperature in elderly people. We employed a generalized additive mixed model to evaluate the acute effects of personal temperature exposure on changes in SpO2 and risk of oxygen desaturation while adjusting for seasonality, environmental co-exposures, and personal characteristics. We observed a concurrent decline in SpO2 by 0.27% (95% confidence interval [CI]: 0.22-0.32%) and an increase in the risk of oxygen desaturation by an OR of 1.14 (95% CI, 1.10-1.18) associated with a 1 °C increase in personal temperature, and the association lasted over several hours. Results showed that the decline in SpO2 in elderly people was associated with an increase in personal temperature exposure within minutes to hours, particularly in women and male patients with COPD. Temperature-induced oxygen desaturation may play a pivotal role in COPD exacerbation.

Source contributions of surface ozone in China using an adjoint sensitivity analysis.

Air pollution has become an adverse environmental problem in China, resulting in serious public health impacts. This study advanced and applied the CMAQ adjoint model to quantitatively assess the source-receptor relationships between surface ozone (O3) changes over different receptor regions and precursor emissions across all locations in China. Five receptor regions were defined based on the administrative division, including northern China (NC), southern China (SC), Pearl River Delta region (PRD), Yangtz River Delta region (YRD), and Beijing-Tianjin-Hebei region (BTH). Our results identified the different influential pathways of atmospheric processes and emissions to O3 pollution. We found that the atmospheric processes such as horizontal and vertical advection could offset the O3 removal through chemical reactions in VOC-limited areas inside the receptor regions. In addition, O3 pollution can be induced by transport of O3 directly or its precursors. Our results of relative source contributions to O3 show that transboundary O3 pollution was significant in SC, NC and YRD, while the O3 pollution in PRD and BTH were more contributed by local sources. Anhui, Hubei and Jiangsu provinces were the three largest source areas of NOx and VOC emissions to O3 in SC (>52%) and YRD (>69%). NOx and VOC emissions from Tianjin and Beijing were the largest contributors to O3 in NC (>34%) and BTH (>51%). PRD was the dominant source areas of NOx (>89%) and VOC emissions (~98%) to its own regional O3.

Estimation of personal exposure to fine particles (PM2.5) of ambient origin for healthy adults in Hong Kong.

Personal exposure and ambient fine particles (PM2.5) measurements for 13 adult subjects (ages 19-57) were conducted in Hong Kong between April 2014 and June 2015. Six to 21 personal samples (mean = 19) per subject were obtained throughout the study period. Samples were analyzed for mass by gravimetric analysis, and 19 elements (from Na to Pb) were analyzed using X-Ray Fluorescence. Higher subject-specific correlations between personal and ambient sulfur (rs = 0.92; p < 0.001) were found as compared to PM2.5 mass (rs = 0.79; p < 0.001) and other elements (0.06 < rs < 0.86). Personal vs. ambient sulfur regression yielded an average exposure factor (Fpex) of 0.73 ±â€¯0.02, supporting the use of sulfur as a surrogate to estimate personal exposure to PM2.5 of ambient origin (Ea). Ea accounted for 41-82% and 57-73% of total personal PM2.5 exposures (P) by season and by subject, respectively. The importance of both Ea and non-ambient exposures (Ena, 11.2 ±â€¯5.6 µg/m3; 32.5 ±â€¯10.9%) are noted. Mixed-effects models were applied to estimate the relationships between ambient PM2.5 concentrations and their corresponding exposure variables (Ea, P). Higher correlations for Ea (0.90; p < 0.001) than for P (0.58; p < 0.01) were found. A calibration coefficient < 1 suggests an attenuation of 22% (ranging 16-28%) of the true effect estimates when using average ambient concentrations at central monitoring stations as surrogates for Ea. Stationary ambient data can be used to assess population exposure only if PM exposure is dominated by Ea.

Determinants of personal exposure to fine particulate matter (PM2.5) in adult subjects in Hong Kong.

Personal monitoring for fine particulate matter (PM2.5) was conducted for adults (48 subjects, 18-63years of age) in Hong Kong during the summer and winter of 2014-2015. All filters were analyzed for PM2.5 mass and constituents (including carbonaceous aerosols, water-soluble ions, and elements). We found that season (p=0.02) and occupation (p<0.001) were significant factors affecting the strength of the personal-ambient PM2.5 associations. We applied mixed-effects models to investigate the determinants of personal exposure to PM2.5 mass and constituents, along with within- and between-individual variance components. Ambient PM2.5 was the dominant predictor of (R2=0.12-0.59, p<0.01) and the largest contributor (>37.3%) to personal exposures for PM2.5 mass and most components. For all subjects, a one-unit (2.72µg/m3) increase in ambient PM2.5 was associated with a 0.75µg/m3 (95% CI: 0.59-0.94µg/m3) increase in personal PM2.5 exposure. The adjusted mixed-effects models included information extracted from individual's activity diaries as covariates. The results showed that season, occupation, time indoors at home, in transit, and cleaning were significant determinants for PM2.5 components in personal exposure (R2ß=0.06-0.63, p<0.05), contributing to 3.0-70.4% of the variability. For one-hour extra time spent at home, in transit, and cleaning an average increase of 1.7-3.6% (ammonium, sulfate, nitrate, sulfur), 2.7-12.3% (elemental carbon, ammonium, titanium, iron), and 8.7-19.4% (ammonium, magnesium ions, vanadium) in components of personal PM2.5 were observed, respectively. In this research, the within-individual variance component dominated the total variability for all investigated exposure data except PM2.5 and EC. Results from this study indicate that performing long-term personal monitoring is needed for examining the associations of mass and constituents of personal PM2.5 with health outcomes in epidemiological studies by describing the impacts of individual-specific data on personal exposures.

Air quality and climate impacts of alternative bus technologies in Greater London.

The environmental impact of diesel-fueled buses can potentially be reduced by the adoption of alternative propulsion technologies such as lean-burn compressed natural gas (LB-CNG) or hybrid electric buses (HEB), and emissions control strategies such as a continuously regenerating trap (CRT), exhaust gas recirculation (EGR), or selective catalytic reduction with trap (SCRT). This study assessed the environmental costs and benefits of these bus technologies in Greater London relative to the existing fleet and characterized emissions changes due to alternative technologies. We found a >30% increase in CO2 equivalent (CO2e) emissions for CNG buses, a <5% change for exhaust treatment scenarios, and a 13% (90% confidence interval 3.8-20.9%) reduction for HEB relative to baseline CO2e emissions. A multiscale regional chemistry-transport model quantified the impact of alternative bus technologies on air quality, which was then related to premature mortality risk. We found the largest decrease in population exposure (about 83%) to particulate matter (PM2.5) occurred with LB-CNG buses. Monetized environmental and investment costs relative to the baseline gave estimated net present cost of LB-CNG or HEB conversion to be $187 million ($73 million to $301 million) or $36 million ($-25 million to $102 million), respectively, while EGR or SCRT estimated net present costs were $19 million ($7 million to $32 million) or $15 million ($8 million to $23 million), respectively.

Public health impacts of combustion emissions in the United Kingdom.

Combustion emissions are a major contributor to degradation of air quality and pose a risk to human health. We evaluate and apply a multiscale air quality modeling system to assess the impact of combustion emissions on UK air quality. Epidemiological evidence is used to quantitatively relate PM(2.5) exposure to risk of early death. We find that UK combustion emissions cause ∼13,000 premature deaths in the UK per year, while an additional ∼6000 deaths in the UK are caused by non-UK European Union (EU) combustion emissions. The leading domestic contributor is transport, which causes ∼7500 early deaths per year, while power generation and industrial emissions result in ∼2500 and ∼830 early deaths per year, respectively. We estimate the uncertainty in premature mortality calculations at -80% to +50%, where results have been corrected by a low modeling bias of 28%. The total monetized life loss in the UK is estimated at £6-62bn/year or 0.4-3.5% of gross domestic product. In Greater London, where PM concentrations are highest and are currently in exceedance of EU standards, we estimate that non-UK EU emissions account for 30% of the ∼3200 air quality-related deaths per year. In the context of the European Commission having launched infringement proceedings against the UK Government over exceedances of EU PM air quality standards in London, these results indicate that further policy measures should be coordinated at an EU-level because of the strength of the transboundary component of PM pollution.

Public health, climate, and economic impacts of desulfurizing jet fuel.

In jurisdictions including the US and the EU ground transportation and marine fuels have recently been required to contain lower concentrations of sulfur, which has resulted in reduced atmospheric SO(x) emissions. In contrast, the maximum sulfur content of aviation fuel has remained unchanged at 3000 ppm (although sulfur levels average 600 ppm in practice). We assess the costs and benefits of a potential ultra-low sulfur (15 ppm) jet fuel standard ("ULSJ"). We estimate that global implementation of ULSJ will cost US$1-4bn per year and prevent 900-4000 air quality-related premature mortalities per year. Radiative forcing associated with reduction in atmospheric sulfate, nitrate, and ammonium loading is estimated at +3.4 mW/m(2) (equivalent to about 1/10th of the warming due to CO(2) emissions from aviation) and ULSJ increases life cycle CO(2) emissions by approximately 2%. The public health benefits are dominated by the reduction in cruise SO(x) emissions, so a key uncertainty is the atmospheric modeling of vertical transport of pollution from cruise altitudes to the ground. Comparisons of modeled and measured vertical profiles of CO, PAN, O(3), and (7)Be indicate that this uncertainty is low relative to uncertainties regarding the value of statistical life and the toxicity of fine particulate matter.