Published papers

In order to understand the actual status and mechanism of acid rain, it is important to know the pH of precipitation and its chemical constituents on a continuous and regular basis over a wide area. This study examines acid rain over a wide area using an observational network in the Tokyo metropolitan area of Japan, and analyzes the major chemical constituents of every precipitation sample. Precipitation was collected continuously for a period of 12 years from June 1990 to May 2002 at several sampling sites in the Tokyo metropolitan area, and its pH and chemical constituent concentrations were measured. The average pH ranged from 4.23 to 4.62, clearly indicating acidification of precipitation over the entire Tokyo metropolitan area. A time-trend model was applied to describe temporal variations of chemical constituent concentrations, including annual change rate, seasonal variation, and precipitation effects. Seasonal and annual trends for the past 12 years were examined with the model, using the least squares method. Nonsea salt (nss)-Ca2+ shows a maximum value in early spring, a seasonality probably caused by calcium-rich particles in airborne yellow dust from Asia. Slightly decreasing annual trends of nss-SO 42- may correspond to the recent decreasing trend of atmospheric SO2 gas concentrations in the Tokyo metropolitan area. The annual trends of NO3-, NH4+, and nss-Ca2+ show a large site-to-site difference. The increasing NO3-, NH4+, and nss-Ca2+ concentrations at inland suburban sites may be caused by increases in their local sources such as vehicle traffic and municipal waste incineration. The annual change rate of H+ is slightly negative or almost zero at every site, so the acidification of precipitation has not become worse since 1990 over the Tokyo metropolitan area. © 2004 Elsevier B.V. All rights reserved.

Molecular and carbon isotopic compositions of atmospheric polycyclic aromatic hydrocarbons (PAHs) were measured in sites at 1 m (S1), 10 m (S2) and approximately 200 m (S3) distant from roads in Tokyo. Japan. Total suspended particles (TSP) concentrations at S1 was approximately three times higher than S2 and S3, while the concentration of atmospheric PAHs was almost the same (76-166, μg g-1-TSP) at S1, S2 and S3. Compound-specific δ13C of atmospheric PAHs ranged from -23.3 to -24.5‰ at S1, from -24.1 to -25.6‰ at S2, and from -25.2 to -27.0‰ at S3. The concentration of some PAHs and the weighted averages of δ13C of some selected PAHs differed significantly among the three sites. The PAH concentration ratios indicating automotive contribution were S1 > S2 > S3, while the ratios indicating non-vehicle contribution were S3 > S2 > S1. These differences in molecular and isotopic signatures among the three sites are not caused by photolysis, instead they are possibly due to differences in the sources of PAHs. A quantitative approach to identify compound-specific sources is to use the concentration and δ13C of individual PAHs at each site. The estimated average δ13C values of individual PAHs derived from automobiles, which was calculated using a mass balance model, ranged from -19.5 to -23.6‰. Taking into account the results of this study and those of previous studies, -26 to -28‰ was adopted as the δ13C value of PAHs derived from non-vehicle sources. We estimated that the automotive contribution to the concentration of individual PAHs ranged from 33 to 88% at S1, from 11 to 74% at S2, and from 0 to 52% at S3. We conclude that compound-specific δ13C measurement is a powerful and useful tool to identify such compound-specific sources of atmospheric PAHs. © 2004 by The Geochemical Society of Japan.

This paper provides improved elemental analysis methods for the characterization of atmospheric particulate matter (PM) samples. With the aim of developing an approach for comprehensive trace element analysis of small mass of PM samples, we coupled an enhanced microwave-assisted acid digestion method with high-resolution magnetic sector inductively coupled plasma-mass spectrometry (SF-ICP-MS). We also propose a rapid and simple method using energy dispersive X-ray fluorescence spectrometry (EDXRF) that has secondary targets and three-dimensional polarization optics for screening elemental composition of PM. We obtained the concentrations of 44 elements ranged from 10-3 to 105μg/g by SF-ICP-MS, and 16 elements ranged from 101 to 105μg/g by EDXRF. The analytic results obtained by these two methods agreed well. Comprehensive analysis for a large set of elements was demonstrated by using the improved SF-ICP-MS method, while EDXRF coupled with fundamental parameter (FP) quantification method can analyze several selected elements as fast as 900s (15min) per sample with only minimal sample pretreatment. We provide two possible choices of analysis methods for elucidating elemental composition of PM according to the number of samples, target elements, sample amounts, time and cost for analysis required.

In view of the recent rapid economic growth and accompanying energy consumption in the East Asian region, particularly in China, there is much concern about the effects of emitted particulate pollutants on human health. We have thus investigated the impact of long-range transport of aerosols on urban air quality in the upwind areas of Japan by comparing the PM2.5 composition collected for multiple years in Fukuoka, a representative metropolis in the Kyushu area, and in Fukue Island, located 190km southwest of Fukuoka. Daily averaged PM2.5 concentrations in Fukuoka and Fukue were almost identical. PM2.5 concentrations at these sites were dominated by sulfate and particulate organics, and their fluctuation patterns were similar except for organics in the warm season. In contrast, those of nitrate and elemental carbon differed substantially between the sites. In addition, the ratios of Pb/Zn and Cd/Pb in Fukuoka were close to the reported values in Beijing. Non-sea-salt sulfate concentration in Fukuoka measured in this study and reported in the past measurements apparently coincided with the decadal SO2 emission change in China reported in a recent emission inventory. Therefore, we conclude that even in a city as large as Fukuoka, the PM2.5 concentration in the northern part of the Kyushu area is primarily dominated by the inflow of long-range transported aerosols throughout the year, except in the summer, rather than local air pollution emitted at each site.

Measurement of the phosphorus concentration in aerosols in Beijing, which was a representative East Asian mega-city, was carried out. The optimum procedure for analyzing phosphorus in aerosols was found in this study. Recovery of phosphorus in environmental samples through the improved method was almost 100%. The concentration of phosphorus in TSP was 145&Plusminus;47 ng/m3, with a seasonal variation showing high concentrations in winter and low concentrationsin summer. The concentrations of phosphorusin PM2.5 accounted for 35&Plusminus;6% of those inTSP, with no seasonal variations. The major source of phosphorus in aerosols in Beijing was soil dust, and additional sources of phosphorus in fine particles could be coal combustion and biomass burning.

The investigation of the surface area of atmospheric aerosols is important as it provides a metric for their adverse health effects; however, few previous studies have considered this parameter. This study investigated the BET specific surface areas of aerosols, as well as the particle size distributions and chemical compositions of the three commercially available atmospheric aerosol reference materials; namely SRM1649a, CRM#28 and CRM#8. SRM1649a and CRM#28 consist mainly of coarse particles, while CRM#8 consists mainly of fine (or ultrafine) particles. The specific surface areas of the reference materials were; SRM1649a: 2.0±0.2m2g-1, CRM#28: 2.0±0.2m2g-1 and CRM#8: 35.7±5.3m2g-1. CRM#8 had a higher value for the specific surface area. The specific surface area for CRM#8 was likely to be associated with the characteristics of diesel particulate matters. When the estimation of specific surface area of aerosol particles is based on the assumption that all particles are spherical and not aggregates/agglomerates, using particle number and mass distribution, the estimated value is likely to be significantly lower than the actual value, in particular, for fine or ultrafine particles. The actual specific surface area of atmospheric aerosols should be measured to avoid the underestimation of their adverse health effects. © 2013 Elsevier Ltd.

This study is a systematic field observation campaign that examines the chemical characteristics of aerosols in four different mega-cities in Asia, namely Beijing (China), Hanoi (Vietnam), Kolkata (India), and Tokyo (Japan). The unity of the analytical method and the synchronicity of the sampling periods are quite important, especially when developing a comparative risk assessment in different places. Sampling was thus carried out in each city continuously for a one-year period between 2008 and 2010, as this enabled consideration of the seasonal variations that are associated with the Asian monsoon system that governs the climate of this region. The study found that the sum of the concentrations of measured elements decreased in the order of BJ > KK > HA > TY, while the sum of the concentrations of measured ions decreased in the order of BJ > HA > KK > TY. The concentration level of chemical species in aerosols in Beijing was one order of magnitude higher than that in Tokyo. The risks associated with carcinogenic metals in the four cities have also been calculated. We conclude that the calculated carcinogenic risks to humans by chromium were higher than the risks caused by nickel in all four cities. Copyright © Taiwan Association for Aerosol Research.

To investigate the chemical characteristics of precipitation in the polluted urban atmosphere in Beijing and possible mechanisms influencing their variations, a total of 131 event-based precipitation samples were collected from March 2001 to August 2005. The concentrations of major ions in the samples were analyzed by using ion chromatography. Intermediate pH (6.1-7.3) was recorded in approximately two-thirds of the precipitation samples and acidic pH (4.2-5.6) in only 16% of the samples. However, the precipitation acidity was on the growth track and the process was likely being accelerated. SO4 2-, NO3-, NH4+, and Ca2+ were the most abundant ions in the precipitations, with their single volume-weighted mean (VWM) concentration all above 100 μeq l-1. The two major anions and two major cations accounted for more than 80% of total anionic and cationic mass, respectively. The VWM SO4 2- concentration decreased by 13% compared to that during 1995-1998, much less than the 58% reduction in the annual average SO2 concentration from 1998 to 2005 in Beijing. What seems more counterintuitive is that the VWM NO3- concentration nearly doubled over the period although the annual average NO2 concentration decreased by 5% from 1998 to 2005. These results imply that the conversion of gaseous precursors to acid compounds and/or the regional transport were reinforced over the decade. The average ratio of neutralizing potential to acidifying potential (i.e. NP/AP) was as high as 1.2 but experienced an evident decline trend. This was mainly ascribed to reduced input of NH4+ and Ca2+ and increased input of NO3-. Furthermore, the equivalent mass ratio of NO3- to non-sea-salt SO42- presented an increasing trend over the study period, suggesting that the contribution of NO3- to the precipitation acidity increased in recent years. However, the mean ratio was only 0.37 ± 0.11 in the study period, which is significantly lower than those reported in some metropolitan areas in developed countries. This shows that the precipitation acidity in Beijing was still dominantly from SO2 while the SO2 contribution was progressively substituted by NOx. © 2012 Author(s).

TSP and PM2.5 samples were collected at Xi'an, China during dust storms (DSs) and several types of pollution events, including haze, biomass burning, and firework displays. Aerosol mass concentrations were up to 2 times higher during the particulate matter (PM) events than on normal days (NDs), and all types of PM led to decreased visibility. Water-soluble ions (Na+, NH4+, K+, Mg2+, Ca2+, F-, Cl-, NO3-, and SO42-). were major aerosol components during the pollution episodes, but their concentrations were lower during DSs. NH4+, K+, F-, Cl-, NO3-, and SO42- were more abundant in PM2.5 than TSP but the opposite was true for Mg2+ and Ca2+. PM collected on hazy days was enriched with secondary species (NH4+, NO3-, and SO42) while PM from straw combustion showed high K+ and Cl-. Firework displays caused increases in K+ and also enrichments of NO3- relative to SO42-. During DSs, the concentrations of secondary aerosol components were low, but Ca2+ was abundant. Ion balance calculations indicate that PM from haze and straw combustion was acidic while the DSs samples were alkaline and the fireworks' PM was close to neutral. Ion ratios (SO42-/K+, NO3-/SO42-, and Cl-/K+) proved effective as indicators for different pollution episodes. © 2009 Elsevier Ltd. All rights reserved.

Aerosol samples were continuously collected at Rishiri Island, Japan and concentrations of trace metals and water-soluble ionic constituents in the aerosol samples were measured in this study. Trace metal concentrations were analyzed by using inductively coupled plasma mass spectrometry equipped with a laser ablation sample introduction (LA/ICP-MS), which is a rapid and simultaneous method for multi-element analysis. The average concentrations of trace metals and water-soluble ionic constituents in TSP at Rishiri Island from March 2001 to October 2003 were: Al: 251 ± 371 (n= 359), Ti: 27 ± 38 (n= 342), V: 1.3 ± 1.6 (n= 327), Cr: 2.0 ± 2.2 (n= 202), Mn: 8.6 ± 12.0 (n= 353), Fe: 356 ± 645 (n= 349), Co: 0.18 ± 0.25 (n= 250), Ni: 1.9 ± 3.4 (n= 232), Cu: 7.4 ± 10.2 (n= 123), Zn: 16 ± 20 (n= 242), As: 1.2 ± 2.1 (n= 312), Se: 0.49 ± 0.65 (n= 133), Cd: 0.19 ± 0.33 (n= 285), Sb: 0.46 ± 0.62 (n= 265), Pb: 16 ± 30 (n= 314), Na+: 1153 ± 1384 (n= 306), NH4 +: 247 ± 257 (n= 254), K+: 74 ± 63 (n= 284), Ca2+: 144 ± 174 (n= 294), Mg 2+: 150 ± 161 (n= 293), Cl-: 2703 ± 3151 (n= 180), NO3 -: 339 ± 415 (n= 332), SO4 2-: 1648 ± 1398 (n= 362) (unit: ng m-3). The obtained trace metal concentration levels in the aerosol were 1/10-1/70 of those obtained at Beijing, China and 1/2-1/40 of those obtained at Tokyo, Japan. The correlation between Al, Ti, Mn, and Fe, which were derived mainly from soil dust, was high at Rishiri Island. High-concentration events (when the measured value exceeds the average +3σ for the entire observation period) for each chemical constituent were observed several times per year, although the chemical concentration levels in TSP at Rishiri Island were almost constant throughout the year. The high-concentration phenomenon, which occurred in only 2% of the measurement days, raised the average concentration of the atmospheric chemical constituents at Rishiri Island by about 10%. The average value of the Pb/Zn ratio at Rishiri Island during the entire period was 1.8 ± 2.9, which is higher than 1. This suggests that the atmosphere at Rishiri Island has constantly been receiving contaminants from the Asian Continent. We conclude that the chemical constituents in the aerosol at Rishiri Island have been regularly transported from a wide area across the Asian Continent. © Springer 2006.

Measurements were performed in spring 2001 and 2002 to determine the characteristics of soil dust in the Chinese desert region of Dunhuang, one of the ground sites of the Asia-Pacific Regional Aerosol Characterization Experiment (ACE-Asia). The mean mass concentrations of total suspended particle matter during the spring of 2001 and 2002 were 317 μg m-3 and 307 μg m-3, respectively. Eleven dust storm events were observed with a mean aerosol concentration of 1095 μg m-3, while the non-dusty days with calm or weak wind speed had a background aerosol loading of 196 μg m-3 on average in the springtime. The main minerals detected in the aerosol samples by X-ray diffraction were illite, kaolinite, chlorite, quartz, feldspar, calcite and dolomite. Gypsum, halite and amphibole were also detected in a few samples. The mineralogical data also show that Asian dust is characterized by a kaolinite to chlorite (K/C) ratio lower than 1 whereas Saharan dust exhibits a K/C ratio larger than 2. Air mass back-trajectory analysis show that three families of pathways are associated with the aerosol particle transport to Dunhuang, but these have similar K/C ratios, which further demonstrates that the mineralogical characteristics of Asian dust are different from African dust.

Observation of the ambient aerosol surface area concentrations is important to understand the aerosol toxicity because an increased surface area may be able to act as an enhanced reaction interface for certain reactions between aerosol particles and biological cells, as well as an extended surface for adsorbing and carrying co-pollutants that are originally in gas phase. In this study, the concentration of aerosol surface area was measured from April 2015 to March 2016 in Fukuoka, Japan. We investigated the monthly and diurnal variations in the correlations between the aerosol surface area and black carbon (BC) and sulfate concentrations. Throughout the year, aerosol surface area concentration was strongly correlated with the concentrations of BC, which has a relatively large surface area since BC particles are usually submicron agglomerates consisting of much smaller (tens of nanometers) sized primary soot particles. The slopes of the regression between the aerosol surface area and BC concentrations was highest in August and September 2015. We presented evidence that this was caused by an increase in the proportion of airmasses that originated on the main islands of Japan. This may enhance the introduction of the BC to Fukuoka from the main islands of Japan which we hypothesize to be relatively fresh or "uncoated", thereby maintaining its larger surface area.

A cyclone is an effective tool to facilitate the collection of aerosol particles without using filters, and in cell exposure studies is able to collect a sufficient amount of aerosol particles to evaluate their adverse health effect. In this study, we examined two different methods to improve the aerosol particle collection efficiency of a cyclone. The individual and combined effects of reducing the surface roughness of the inner wall of the cyclone and of using a circular cone attachment were tested. The collection efficiency of particles of diameter 0.2 μm was improved by approximately 10% when using a cyclone with a smoothened inner wall (average roughness Ra=0.08 μm) compared with the original cyclone (Ra=5.1 μm). A circular cone attachment placed between the bottom section of the cyclone and the top section of a collection bottle, resulted in improved collection of smaller particles without the attachment. The 50% cutoffdiameter of the modified cyclone (combined use of smoothened inner wall and attachment) was 0.23 μm compared to 0.28 μm in the original model. The combined use of these two techniques resulted in improved collection efficiency of aerosol particles.

Numerous researchers have proposed that surface area is a more appropriate indicator than mass for evaluating pulmonary inflammatory responses caused by exposure to fine and ultrafine particles. In this study, measurements of surface area concentrations of aerosols were conducted in Yokohama, Japan, using the diffusion charging method. PM2.5 mass concentration and black carbon concentration in PM2.5 were also measured. The 24-hour continuous measurement campaigns were conducted 39 times from March to November, 2014. The surface area concentration was more closely correlated with the black carbon concentration than with the PM2.5 mass concentration. It is considered that the abundance of black carbon particles significantly affects the surface area concentration of PM2.5. The strength of the correlation between the surface area and black carbon concentrations varied considerably among the measurement campaigns. A relatively weaker afternoon correlation was observed compared with the other time zones (morning, evening, and night). We consider that these phenomena are due to the transportation/formation of the particles other than black carbon that affects surface area concentration and/or the variation of the surface condition of the black carbon particles.

The surface area of ambient aerosols can be considered as an index of toxicity because an increased surface area may be able to act as a catalyst for specific reactions between particles and cells, as well as a carrier for co-pollutants, such as gases and chemicals. The aerosol surface area concentration was measured together with black carbon (BC) and other chemical species such as organic compounds, sulfate, and nitrate in Fukuoka, Japan, and the effect of the chemical composition of aerosols on their surface area was investigated. Aerosol surface area concentration was highly correlated with BC concentration for the entire period. Day-of-week variation and diurnal variation also showed the strong correlation between aerosol surface area and BC. This implies that even though BC accounts for relatively small percentage (in this study, 3.5%) of PM2.5 mass, it should receive considerable attention when aerosol surface area is considered as an index of adverse health effects caused by exposure of the human body to aerosols. Sulfate aerosol does not usually affect aerosol surface area in Fukuoka, but it may occasionally have a significant effect when the airmass contains an excess amount of relatively smaller particles of sulfate derived from volcanic SO2.

© 2020. The Authors. Emission inventories of anthropogenic transition metals, which contribute to aerosol oxidative potential (OP), in Asia (Δx = 0.25°, monthly, 2000–2008) and Japan (Δx = 2 km, hourly, mainly 2012) were developed, based on bottom-up inventories of particulate matters and metal profiles in a speciation database for particulate matters. The new inventories are named Transition Metal Inventory (TMI)-Asia v1.0 and TMI-Japan v1.0, respectively. It includes 10 transition metals in PM2.5 and PM10, which contributed to OP based on reagent experiments, namely, Cu, Mn, Co, V, Ni, Pb, Fe, Zn, Cd, and Cr. The contributions of sectors in the transition metals emission in Japan were also investigated. Road brakes and iron-steel industry are primary sources, followed by other metal industry, navigation, incineration, power plants, and railway. In order to validate the emission inventory, eight elements such as Cu, Mn, V, Ni, Pb, Fe, Zn, and Cr in anthropogenic dust and those in mineral dust were simulated over East Asia and Japan with Δx = 30 km and Δx = 5 km domains, respectively, and compared against the nation-wide seasonal observations of PM2.5 elements in Japan and the long-term continuous observations of total suspended particles (TSPs) at Yonago, Japan in 2013. Most of the simulated elements generally agreed with the observations, while Cu and Pb were significantly overestimated. This is the first comprehensive study on the development and evaluation of emission inventory of OP active elements, but further improvement is needed.

Coronavirus disease (COVID-19) is currently a serious global issue. Epidemiological studies have identified air pollutants, including particulate matter (PM), as a risk factor for COVID-19 infection and severity of illness, in addition to numerous factors such as pre-existing conditions, aging and smoking. However, the mechanisms by which air pollution is involved in the manifestation and/or progression of COVID-19 is still unknown. In this study, we used a mouse model exposed to crude PM, collected by the cyclone method, to evaluate the pulmonary expression of angiotensin-converting enzyme 2 (ACE2) and transmembrane protease serine type 2 (TMPRSS2), the two molecules required for the entry of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) into host cells. Multiplex immunohistochemical analysis revealed that exposure to PM increased the expression of these two molecules at the same site. Furthermore, image cytometry analysis revealed increased expression of these proteins, particularly, in the alveolar type 2 cells and macrophages, which are potential targets for SARS-CoV-2. Our findings provide an experimental evidence that exposure to PM may adversely affect the manifestation and progression of COVID-19, mediated by the impact of SARS-CoV-2 on the site of entry. The study results suggest that examining these effects might help to advance our understanding of COVID-19 and aid the development of appropriate social interventions.

Air pollutants are important factors that contribute to the development and/or exacerbation of allergic inflammation accompanied by asthma, but experimental evidence still needs to be collected. Interleukin 33 (IL-33) is closely involved in the onset and progression of asthma. In this study, we examined the effects of particulate matter (PM) on IL-33 expression in macrophages. PM2.5 collected in Yokohama, Japan by the cyclone device significantly induced IL-33 expression in human THP-1 macrophages, and the induction was clearly suppressed by pretreatment with the aryl hydrocarbon receptor (AhR) antagonist CH-223191 or the Toll-like receptor 4 (TLR4) antagonist TAK-242. PM2.5-induced IL-33 expression was significantly attenuated in AhR-knockout or TLR4-mutated macrophages, suggesting an important role of polycyclic aromatic hydrocarbons (PAHs) and endotoxin in IL-33 stimulation. PM samples derived from tunnel dust slightly but significantly induced IL-33 expression, while road dust PM did not affect IL-33 expression. The PAH concentration in tunnel dust was higher than that in road dust. Tunnel dust or road dust PM contained less endotoxin than PM2.5 collected in Yokohama. These data suggest that the potency of IL-33 induction could depend on the concentration of PAHs as well as endotoxin in PMs. Caution regarding PAHs and endotoxin levels in air pollutants should be taken to pre-vent IL-33-induced allergic inflammation.

Evaluation of the health effects of particulate matter with aerodynamic dias. ≤ 2.5 μm (PM2.5) should reflect realistic condition in ambient atmosphere. However, using conventional filtration methods, only extracts from PM2.5 collected on the filter can be analyzed and not the particle itself. Cyclonic separation is a technique that enables the direct analysis of the effects of the crude “powder form” of PM2.5 on respiratory health. Airway epithelial cells and antigen-presenting cells were exposed to PM2.5 collected during the same period using a conventional filtration method or cyclonic separation. PM2.5 collected using cyclonic separation led to a higher secretion of interleukins 6 and 8 (IL-6, IL-8) from airway epithelial cells, and IL-6, IL-1β, tumor necrosis factor-α (TNF-α) secretion, cluster of differentiation 86 (CD86), and dendritic and epithelial cells 205 (DEC205) expression on antigen-presenting cells, compared with the effects of filter-collected PM2.5. Furthermore, PM2.5 collected using cyclonic separation increased inflammatory cytokine levels and induced lung inflammation in vivo. These results suggest that crude PM2.5 collected using cyclonic separation causes stronger biological responses than filter-collected PM2.5. Hence, PM2.5 collected using cyclonic separation can be utilized for a reliable evaluation of the health effects of ambient PM2.5.

During the COVID-19 pandemic, it has been important to both minimize the risk of infection and restore daily life. As a typical example, mass gathering events, such as sporting events, are gradually becoming more common, thanks to the measures taken to contain COVID-19. Some pilot studies have been launched at governments' initiative to investigate the risk of infection without measures such as face masks and physical distancing at mass gathering events, but the ethics of these studies should be carefully considered. On the other hand, it is still beneficial to implement infection control measures at mass gathering events and, in parallel, to estimate the risk of infection with measures in place, especially under a lack of vaccination progress or the spread of mutant strains possibly resistant to vaccines. To help improve compliance with measures taken by spectators and organizers and to ensure their effectiveness, we have conducted quantitative evaluations of the implementation of such measures by monitoring CO2 concentrations, assessing the proportion of people wearing face masks and analysing human flow at the event. This approach allows us to share our observations with stakeholders and participants, enabling us to protect the culture of mass gathering events, minimize the risk of infection and restore a sense of well-being in daily life.