Average O3 Concentrations Research Articles

The association between ozone exposure and blood pressure in a general Chinese middle-aged and older population: a large-scale repeated-measurement study

BackgroundThe relationship between ozone (O3) exposure and blood pressure (BP) remains inconclusive. Given the scarcity of Chinese epidemiological data, more research on this association is of paramount importance, particularly among middle-aged and older Chinese populations.MethodsThis study involved 10,875 participants (median age: 60.0 years) in Xiamen, China, from 2013 to 2019, with 34,939 repeated BP measurements. Air pollutant exposure data, including O3, particulate matter, nitrogen dioxide, sulfur dioxide, and carbon monoxide were derived from China High Air Pollutants and High-resolution Air Quality Reanalysis datasets using a k-nearest neighbor algorithm. The relationship between mixed air pollutant exposure and BP was evaluated using Bayesian kernel machine regression model. The effects of daily-specific O3 exposure on BP were assessed by distributed lag models integrated into a linear mixed-effects framework. The mediating role of total cholesterol (TC), serum total bilirubin (STB), triglyceride (TG), and low-density lipoprotein (LDL) were examined using multilevel mediation analysis with a fully adjusted model.ResultsMixed air pollutant exposure was positively correlated with BP, with O3 being a predominant contributor exhibiting an inverse effect. O3 exposure had immediate effects on pulse pressure (PP), while systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) showed delayed responses, with 3-, 14-, and 8-day lags, respectively. During the study period of up to 30 days, each 10 μg/m3 increase in maximum daily 8-h average O3 concentration was associated with reductions in SBP (β = − 1.176 mm Hg), DBP (− 0.237 mm Hg), PP (β = − 0.973 mm Hg), and MAP (β = − 0.544 mm Hg). Stronger correlations were observed in the older participants (aged ≥ 65 years), overweight/obese individuals, smokers and alcohol consumers, and those with hypertension or type 2 diabetes mellitus. STB and LDL mediated these effects, while TC and TG played mitigating roles.ConclusionsShort-term O3 exposure is negatively associated with BP in middle-aged and older Chinese individuals. The findings provide preliminary evidence for the impact of O3 exposure on BP regulation and underscore the urgent need to reassess public health policies in response to O3 pollution.

Characteristics, Transport Routes, and Potential Sources of PM2.5 and O3 Pollution in Suzhou

Based on the air quality and meteorological data in Suzhou from 2015 to 2022, the long-term variations in PM2.5 and O3, meteorological characteristics, and their correlations were analyzed in this study. The HYSPLIT model was used to explore the main transport pathways and potential source areas of PM2.5 and O3. The results showed that： ① The annual averaged concentrations of PM2.5 in Suzhou decreased steadily during the study period, and the annual average concentration from 2020 to 2022 reached the national second-level standard limit. However, the annual average concentrations of O3 all exceeded the national second-level standard limit. After 2017, the annual number of days that O3 exceeded the standard was always higher than that for PM2.5. The number of days of compound pollution continuously decreased from nine days in 2015 to zero days in 2020, and there was no compound pollution since then. ② The most severe pollution seasons for PM2.5 and O3 were winter and summer, respectively. PM2.5 pollution was more likely to occur in low-temperature and high-humidity weather, while O3 pollution was more frequent in high-temperature and low-humidity weather. Wind direction played an important role, with northwest winds amplifying PM2.5 pollution and southeast winds boosting O3. These two pollutants showed a strong correlation in summer with a coefficient reaching 0.73. ③ Cluster analysis revealed that trajectory two from Hebei Province in spring and trajectory four from Shaanxi Province in winter were prone to an increase in PM2.5 concentration. The short to medium distance trajectory 1 from Shandong Province in summer and trajectory two from Hebei Province in spring were prone to an increase in O3 concentration. ④ The analysis of potential source areas showed that transportation outside the province had a significant impact on PM2.5 and O3 pollution in Suzhou. The potential source areas of PM2.5 in spring and winter were mainly distributed in Anhui Province, Henan Province, and Hubei Province； the potential source areas in autumn were mainly distributed in Hubei Province and Jiangxi Province； and the potential source areas of O3 in spring and summer were mainly located in the Beijing-Tianjin-Hebei Region, Shandong Province, Henan Province, and Shanxi Province. Valuable management insights for the coordinated control of PM2.5 and O3 pollution in Suzhou were put forward based on this study.

Evaluating the effects of meteorology and emission changes on ozone in different regions over China based on machine learning

Systematically understanding the impact of meteorological conditions on regional ozone pollution helps to retrieve ozone dataset and evaluate emission changes on ozone variation. Here, more air-quality observation sites were collected, and Random Forest algorithm was applied to retrieve daily maximum 8 h average (MDA8) O3 concentrations at 1 km resolution in 2019-2020 in China. The region-season model and whole-retrieved model were established to compare the contributions of meteorological variables to ozone variations on spatiotemporal scale. The former model outperformed the latter for retrieval capability, but the predictive ability of the latter was slight stronger. This may be associated with the spatiotemporal heterogeneity of meteorological influence. Daily ozone variability in China was mainly influenced by meteorology, especially in North China Plain in autumn. The key factors were temperature, ultraviolet radiation and relative humidity over the whole country, but varied significantly in different regions and seasons. The effects of meteorology and emission sources on ozone were separated by weather normalization technique. Meteorological conditions were particularly favorable for increasing ozone concentrations in spring, but particularly unfavorable in winter. During the COVID-19 lockdown, the increases in ozone in spring and winter of 2020 were the contribution of the combination of meteorology and emissions; while the decreases in ozone in summer and autumn of 2020 were mainly due to the changes of emission sources, although meteorological conditions were unfavorable to ozone mitigation in heavily polluted areas. Our findings provide scientific basis for the prevention and control of ozone pollution for the regional scale in China.

A novel ensemble machine learning exposure model system for ground-level ozone at the national scale: A case of mainland China from 2013 to 2020

In epidemiological research, accurate estimation of historical ground-level ozone (O3) concentrations with enhanced spatiotemporal resolution is crucial for effective exposure assessment. The current state-of-the-art for estimating air pollutant concentrations is a two-stage ensemble method that integrates outputs from multiple machine learning algorithms. Despite its effectiveness, opportunities exist to refine this approach for more precise O3 estimation. In this study, we propose an enhanced ensemble method that incorporates four key strategies. First, we employ high-resolution spatiotemporal predictors derived from prior machine learning studies for refined secondary learning. Second, we use sophisticated algorithms, including categorical gradient boosting, deep neural network, random forest, stochastic variable Gaussian process, transformer, and a combination of convolutional neural network and long short-term memory neural network, as sublearners to enhance learning capabilities. Third, we spatiotemporally split the sample set and then train submodels separately on each subset to eliminate the unobserved spatiotemporal heterogeneity. Finally, we apply a complex machine learning algorithm, rather than the generalized additive model, for integrating sublearner predictions, enabling the capture of intricate nonlinear relationships beyond basic spatiotemporal linear weights. To validate these improvements, we estimated daily maximum 8-h moving average O3 concentrations ([O3]MDA8) across Chinese mainland from 2013 to 2020 at a 1 km spatial resolution. The proposed method demonstrated notable accuracy, achieving an out-of-station determination coefficient (R2) of 0.943 and a root-mean-square error (RMSE) of 10.197 μg/m3. This performance marks a nearly 15% improvement over the best existing Chinese O3 exposure model based on a single algorithm and also surpasses previous studies utilizing traditional ensemble methods for other air pollutants. Our enhanced ensemble approach significantly bolsters the reliability and robustness of future environmental epidemiological studies by further mitigating “misclassification” errors.

Association of long-term exposure to ozone with cardiovascular mortality and its metabolic mediators: evidence from a nationwide, population-based, prospective cohort study

Previous studies about chronic effects of ozone (O3) on cardiovascular mortality are scarce and inconclusive. We aimed to investigate the association between cardiovascular mortality and a broad range of long-term O3 exposure levels. This analysis included 3,206,871 participants aged 35-75 years enrolled in the ChinaHEART study. Participants were recruited from the 31 provinces of the Chinese mainland between January 2015 and December 2020. The five-year average O3 concentrations before baseline visits were calculated to represent long-term exposure. Over a median follow-up period of 4.7 (interquartile range: 3.7-6.2) years, 35,553 (1.1%) participants died from cardiovascular diseases (CVD). Following multivariable adjustment, nonlinear relationships were identified between O3 concentrations and CVD and ischemic heart disease (IHD) mortality, with inflection points at 85.44 and 88.15μg/m3, respectively. Above these points, a 10.0μg/m3 increase in the O3 level was associated with a 13.9% (hazard ratio [HR]: 1.139, 95% confidence interval [CI]: 1.096-1.184) and 25.0% (HR: 1.250, 95% CI: 1.151-1.357) greater risk of CVD and IHD mortality, respectively. Conversely, O3 exposure exhibited a linear relationship with ischemic stroke mortality. Moreover, the metabolic factors explained more than half of the association between O3 exposure and CVD mortality. Substantial influences of long-term O3 exposure on CVD mortality were identified, with notable mediation proportions attributed to metabolic factors. These findings could facilitate the air quality standard revisions and risk reduction strategy making in the future. This study was supported by the CAMS Innovation Fund for Medical Science (2021-1-I2M-011), the CAMS Innovation Fund for Medical Science (CIFMS, 2022-I2M-C&T-A-010), the National High Level Hospital Clinical Research Funding (2022-GSP-GG-4), the Ministry of Finance of China and National Health Commission of China, the 111 Project from the Ministry of Education of China (B16005).

Diurnal hourly near-surface ozone concentration derived from geostationary satellite in China

Near-surface O3 is a harmful atmospheric pollutant and a key component of urban photochemical pollution. The availability of satellite ozone concentration products is predominantly restricted to daytime, resulting in a lack of understanding of nighttime ozone pollution (e.g. nocturnal ozone enhancement events). This research leverages 5-km bright temperatures derived from Advanced Himawari Images (AHI) on the Himawari-8 satellite, in conjunction with auxiliary data, to estimate 24-h near-surface O3 concentrations in China at a resolution of 5 km for 2020. The model achieves an average 5-fold cross-validation R2 of 0.92. Comparative analysis with on-site observations reveals that the model has low relative errors between 8:00 and 21:00 LT. The estimated O3 maps depict a consistent 24-h variation pattern, characterized by high and most fluctuating concentrations during the daytime, reaching a peak around 16:00 LT, which is primarily due to the increased photochemical reactions and the O3 accumulation in the mid-afternoon. In the daytime of summer, high surface ozone concentrations are mainly contributed by June. The elevated levels of O3 are predominantly found in central China, particularly in the Beijing-Tianjin-Hebei region and Inner Mongolia. It can also be seen that although the highest average daytime surface O3 concentration occurs in summer, the highest nighttime concentration is observed in spring, which may be attributed to the frequent occurrence of horizontal transport and vertical mixing of O3. This study holds promise in providing comprehensive round-the-clock surface O3 data across China, thereby enhancing our understanding of diurnal ground-level O3 variations.

Prescribed burn related increases of population exposure to PM2.5 and O3 pollution in the southeastern US over 2013–2020

Ambient air quality across the southeastern US has improved substantially in recent decades. However, emissions from prescribed burns remain high, which may pose a substantial health threat. We employed a multistage modeling framework to estimate year-round, long-term effects of prescribed burns on air quality and premature deaths. The framework integrates a chemical transport model with a data-fusion approach to estimate 24-h average PM2.5 and maximum daily 8-h averaged O3 (MDA8-O3) concentrations attributable to prescribed burns for the period 2013–2020. The Global Exposure Mortality Model and a log-linear exposure–response function were used to estimate the premature deaths ascribed to long-term prescribed burn PM2.5 and MDA8-O3 exposure in ten southeastern states. Our results indicate that prescribed burns contributed on annual average 0.59 ± 0.20 µg/m3 of PM2.5 (∼10 % of ambient PM2.5) over the ten southeastern states during the study period. On average around 15 % of the state-level ambient PM2.5 concentrations were contributed by prescribed burns in Alabama (0.90 ± 0.15 µg/m3), Florida (0.65 ± 0.19 µg/m3), Georgia (0.91 ± 0.19 µg/m3), Mississippi (0.65 ± 0.10 µg/m3) and South Carolina (0.65 ± 0.09 µg/m3). In the extensive burning season (January–April), daily average contributions to ambient PM2.5 increased up to 22 % in those states. A large part of Alabama and Georgia experiences ≥3.5 µg/m3 prescribed burn PM2.5 over 30 days/year. Additionally, prescribed burns are responsible for an average increase of 0.32 ± 0.12 ppb of MDA8-O3 (0.8 % of ambient MDA8-O3) over the ten southeastern states. The combined effect of prescribed burn PM2.5 exposure, population growth, and increase of baseline mortality over time resulted in a total of 20,416 (95 % confidence interval (CI): 16,562–24,174) excess non-accidental premature deaths in the ten southeastern states, with 25 % of these deaths in Georgia. Prescribed burn MDA8-O3 was responsible for an additional 1,332 (95 % CI: 858–1,803) premature deaths in the ten southeastern states. These findings indicate significant impacts from prescribed burns, suggesting potential benefits of enhanced forest management strategies.

Research on ozone pollution control strategies for urban agglomerations based on ozone formation sensitivity and emission source contributions

Despite recent enhancements in China's anthropogenic emission controls, ozone (O3) concentrations have continuously increased owing to its nature as a secondary pollutant and the complexities of its production and consumption processes. This study quantified the contributions of urban and sectoral cross-emission sources to O3 levels and identified the anthropogenic emission sources requiring targeted control. Moreover, O3 sensitivity tests were conducted to determine optimal reduction ratios for nitrogen oxides (NOx) and volatile organic compounds (VOCs) emissions. The results were used to recommend effective measures for controlling O3 pollution in the Central Plains urban agglomeration (CPUA). The top 35 cities and sectoral cross-emission sources accounted for 80% of the O3 concentrations in the region, indicating the need for prioritized management of these sources. To achieve reductions in O3 concentrations across all cities, it was found that a 10% reduction in total NOx emissions would require a minimum of 18% reduction in VOCs emissions. Our results indicated that the appropriate coordination of reductions in VOCs and NOx emissions reduced the maximum daily 8-h average O3 (MDA8) concentrations in CPUA by 0.14%–4.78%. Enhancing control measures for prioritized emission sources reduced MDA8 concentrations by 0.78%–7.09%. Furthermore, adjusting the production and emission hours of the industrial sector resulted in a decrease in MDA8 concentrations by 1.10%–12.62%. Overall, our findings indicate that appropriately coordinated reduction of precursor emissions can reduce O3 levels. Further efforts to mitigate O3 pollution should include optimizing the timing of emissions from the industrial sector and other major sources of VOCs emissions.

Impact of methane and other precursor emission reductions on surface ozone in Europe: scenario analysis using the European Monitoring and Evaluation Programme (EMEP) Meteorological Synthesizing Centre – West (MSC-W) model

Abstract. The impacts of future methane (CH4) and other precursor emission changes are investigated for surface ozone (O3) in the United Nations Economic Commission for Europe (UNECE) region excluding North America and Israel (the EMEP region, for European Monitoring and Evaluation Programme) for the year 2050. The analysis includes a current legislation (CLE) and maximum feasible technical reduction (MFR) scenario, as well as a scenario that combines MFRs with an additional dietary shift that also meets the Paris Agreement objectives with respect to greenhouse gas emissions (LOW). For each scenario, background CH4 concentrations are calculated using a probabilistic Earth system model emulator and combined with other precursor emissions in a three-dimensional Eulerian chemistry-transport model. While focus is placed on peak season maximum daily 8 h average (MDA8) O3 concentrations, a range of other indicators for health and vegetation impacts are also discussed. Our analysis shows that roughly one-third of the total peak season MDA8 reduction achieved between the 2050 CLE and MFR scenarios is attributable to CH4 reductions, resulting predominantly from CH4 emission reductions outside of the EMEP region. The impact of other precursor emission reductions is split nearly evenly between the reductions inside and outside of the EMEP region. However, the relative importance of CH4 and other precursor emission reductions is shown to depend on the choice of O3 indicator, though indicators sensitive to peak O3 show generally consistent results. The analysis also highlights the synergistic impacts of CH4 mitigation as reducing solely CH4 achieves, beyond air quality improvement, nearly two-thirds of the total global warming reduction calculated for the LOW scenario compared to the CLE case.

Impact of Air Conditioning Type on Outdoor Ozone Intrusion into Homes in a Semi-Arid Climate

Outdoor ozone (O3) is elevated on hot, sunny days when residential air conditioning is used most. We evaluated the impact of direct evaporative coolers (ECs) and vapor-compression air conditioners (ACs) on indoor O3 concentrations in homes (N = 31) in Utah County, Utah, United States of America. Indoor and outdoor O3 concentrations were measured for 24 h at each home using nitrite-impregnated glass-fiber filters. AC homes (n = 16) provided a protective envelope from outdoor O3 pollution. Only one AC home had O3 levels above the limit of detection (LOD). Conversely, EC homes (n = 15) provided minimal protection from outdoor O3. Only one EC home had O3 levels below the LOD. The average indoor O3 concentration in EC homes was 23 ppb (95% CI 20, 25). The indoor-to-outdoor (I/O) ratio for O3 in EC homes was 0.65 (95% CI 0.58, 0.72), while the upper bound for the I/O ratio for AC homes was 0.13 (p < 0.001). Indoor exposure to O3 for residents in EC homes is approximately five times greater than for residents of AC homes. Although ECs offer energy and cost-saving advantages, public health awareness campaigns in O3-prone areas are needed, as well as research into O3 pollution controls for direct ECs such as activated carbon filtration.

Ground ozone rise during the 2022 shanghai lockdown caused by the unfavorable emission reduction ratio of nitrogen oxides and volatile organic compounds

Ground-level ozone (O3) pollution has shifted from a scientific issue to a key focus of governmental action in China. In recent years, the concentration of NO2 in Shanghai has shown a decreasing trend of 3.7% annually, but ozone concentrations have exhibited significant interannual variability, particularly with a noticeable increase in 2022. This study focuses on investigating the mechanisms behind the increase in ozone concentration during the COVID-19 pandemic control period in 2022 in Shanghai, utilizing a combination of ground observation data, observation-based models, and chemical transport models for analysis. The results indicate that during the lockdown period, the mean values of daily maximum 8-h average O3 concentrations (MDA8 O3) in Shanghai increased by 17 μg/m³, with emission-related factors contributing 65.3%, primarily due to a blanket reduction in VOCs and NOx emissions during the lockdown, with a reduction ratio close to 1:1. However, this reduction ratio and intensity are not sufficiently reasonable to alleviate ozone pollution. Meanwhile, adverse meteorological conditions further exacerbated this effect, contributing 34.7%, with temperature rise having the greatest impact. Results from the chemical transport model show that with the total reduction in NOx and VOCs emissions unchanged, the greater the reduction in VOC emissions and the better the reduction effect on ozone pollution, reducing MDA8 O3 by approximately 10 μg/m³, especially for the control of reactive compounds such as alkenes, aromatics, and OVOCs. However, if the reduction ratio of NOx is greater than that of VOCs, ozone concentrations may not decrease but instead increase. This indicates that ozone concentration is influenced not only by the intensity of emissions reduction but also by the ratio of emissions reduction between NOx and VOCs. Our study emphasizes the critical role of carefully designed strategies, focusing on controlling the ratio of VOCs to NOx and increasing the intensity of VOCs reduction, to effectively alleviate ozone pollution in urban areas.

ENVIRONMENTAL POLLUTION IN THE CITY OF BUCHAREST

The work covers air quality monitoring tools in Bucharest, major industrial facilities impacting pollution and the city's eight air quality monitoring stations. Data on pollutant emissions from Bucharest's thermal power plants (SO2, NOx and dust) are presented. Finally, the paper graphically presents the annual average concentrations of NO2, SO2, PM10 and O3 at the monitoring stations and examines pollution peaks and daily limit exceedances from 2017 to 2022.

A comprehensive evaluation of the atmospheric impacts and health risks of cooking fumes from different cuisines

Pollutants emitted by catering enterprises pose a significant threat to the environment and public health. In this study, based on a systematic analysis of volatile organic compound (VOC) emission characteristics of different cuisines, the contribution of cooking emissions from catering enterprises to the PM2.5 and O3 concentrations in the atmosphere was evaluated using generation potential calculations and WRF-CAMx simulations. The health exposure risks of VOCs in kitchen breathing areas and those of PM2.5 and O3 contributed by the catering enterprises were evaluated. The generation potential calculation results showed that the catering enterprises exhibit 2.21–5.00 gO3/gVOCs of ozone formation potential (OFP) and 0.07–0.21 gSOA/gVOCs of secondary organic aerosol production potential (SOAP). The WRF-CAMx simulation results indicated that cooking emissions from catering enterprises contribute 0.36–1.91 μg/m3 and 0.05–0.21 μg/m3 to PM2.5 and maximum daily 8-h average (MDA8) concentrations of O3. The health exposure risks of PM2.5 and O3 were higher in catering enterprises in southern cities than in northern cities and were higher in urban areas than in suburban areas. The average hazardous VOCs (HVOCs) concentrations ranged from 53 ± 16 to 357 ± 31 μg/m3 in kitchen breathing areas. Acrolein was the primary contributor to the hazard index (HI) of all VOC species, accounting for 50.9%–99.5%. The total incremental lifetime carcinogenic risk (ILCR) of all cuisines exceeded the acceptable thresholds of 1.00 × 10−6. These findings provide insights that can aid in the formation and implementation of pollutant mitigation strategies in the catering industry.

Impact of Lockdowns on Air Pollution: Case Studies of Two Periods in 2022 in Guangzhou, China

The photochemical mechanisms of ozone (O3) formation are complex, and simply reducing nitrogen oxide (NOx) emissions is insufficient to reduce O3 concentrations. The lockdown due to the Coronavirus Disease 2019 (COVID-19) pandemic provided a rare opportunity to explore the mechanisms of O3 formation and evaluate the performance of NOx emission control strategies through practical observations. This study integrates data from ground stations with observations from the TROPOMI sensor on the Sentinel-5P satellite to analyze air quality changes during the two one-month lockdown periods in Guangzhou, China, in March and November 2022. Our analysis particularly focuses on the impact of these lockdowns on O3 and NO2 concentrations, along with shifts in the sensitivity of ozone formation. Furthermore, we have assessed concentration changes of four major pollutants: PM2.5, PM10, SO2, and CO. The results show that the average O3 concentration in Guangzhou decreased during the March lockdown, while the average O3 concentration at three stations in the western part of Guangzhou increased during the November lockdown. The western part of Guangzhou is a VOCs (volatile organic compounds)-limited zone, and the NO2 emission reduction from the lockdown reduced the titration effect on O3, which led to the increase in O3 concentration. Overall, the impact of COVID-19 lockdowns on O3 concentrations depended on the local O3 producing sensitive system, and emissions of other major pollutants were reduced substantially, as reported in many other cities around the world.

Regional source contributions to summertime ozone in the Yangtze River Delta

Ozone (O3) pollution is increasing in the Yangtze River Delta (YRD), with significant influences from regional transport during pollution events. However, the specific contributions of different regions remain imprecisely quantified. This study estimated the regional contributions of eight regions to summer O3 in the YRD using the Community Multiscale Air Quality (CMAQ) model with a source-tagged photochemical mechanism. Non-background O3 is attributed to nitrogen oxides (NOX) and volatile organic compounds (VOCs) from different regions. Background O3 is the predominant contributor with average ratios of 75.0%, 65.3%, 64.8% and 63.0% for Shanghai, Nanjing, Hangzhou and the entire YRD, respectively. Locally formed O3 are 39.9, 42.0, 39.6, and 36.9 parts per billion (ppb) by volume in the above areas. North Zhejiang and south Jiangsu are the primary sources of heavy pollution episodes as the maximum daily 8-h average (MDA8) O3 concentrations in these regions increase the most. NOX is the predominant contributor to heavy pollution episodes with the maximum increment attributed to NOX (O3N) of 14.3 ppb, while VOCs only contribute to 2.1 ppb (O3V) in Jiangsu. Relative humidity is crucial in heavy pollution episodes while high temperature, low planetary boundary layer (PBL) height and the wind field are associated with regional transport. Diurnal variation underscores the importance of understanding O3 formation in the afternoon (12:00–16:00), which is essential for devising effective mitigation policies.

Global assessment of climatic responses to ozone–vegetation interactions

Abstract. The coupling between surface ozone (O3) and vegetation significantly influences the regional to global climate. O3 uptake by plant stomata inhibits the photosynthetic rate and stomatal conductance, impacting evapotranspiration through land surface ecosystems. Using a climate–vegetation–chemistry coupled model (the NASA GISS ModelE2 coupled with the Yale Interactive terrestrial Biosphere, or ModelE2-YIBs), we assess the global climatic responses to O3–vegetation interactions during the boreal summer of the present day (2005–2014). High O3 pollution reduces stomatal conductance, resulting in warmer and drier conditions worldwide. The most significant responses are found in the eastern US and eastern China, where the surface air temperature increases by +0.33 ± 0.87 and +0.56 ± 0.38 °C, respectively. These temperature increases are accompanied by decreased latent heat and increased sensible heat in both regions. The O3–vegetation interaction also affects atmospheric pollutants. The surface maximum daily 8 h average O3 concentrations increase by +1.46 ± 3.02 ppbv in eastern China and +1.15 ± 1.77 ppbv in the eastern US due to the O3-induced inhibition of stomatal uptake. With reduced atmospheric stability following a warmer climate, increased cloud cover but decreased relative humidity jointly reduce aerosol optical depth by −0.06 ± 0.01 (−14.67 ± 12.15 %) over eastern China. This study suggests that vegetation feedback should be considered for a more accurate assessment of climatic perturbations caused by tropospheric O3.

Impacts of different vehicle emissions on ozone levels in Beijing: Insights into source contributions and formation processes

Beijing, with the highest number of motor vehicles in China, significantly contributes to O3 pollution through substantial NOx and VOC emissions in the on-road transportation sector. Understanding the unique impact of emissions from different vehicle types on O3 levels is crucial for developing targeted strategies for O3 pollution. This study applied the Community Multiscale Air Quality Modeling System (CMAQ) to comprehensively investigate the impacts of emissions from different vehicle types on O3 levels in various regions of Beijing and to provide valuable insights into source contributions and formation processes. The results revealed that various vehicle types exhibited different spatial-temporal emission patterns, with medium-heavy duty trucks (HDT) and mini-light passenger vehicles (LDPV) identified as the primary contributors to NOx (36.1 %) and VOC (57.6 %) emissions. Using the Integrated Source Apportionment Method (ISAM) coupled in CMAQ, we found the total vehicle emissions contributed to over 20 % of daily maximum 8–h average O3 (MDA8 O3) concentration, ranked as the second largest contributor after regional transport. Contributions to O3 formation from LDPV and medium-large passenger vehicles (MDPV) were 2.6–4.0 and 4.2–6.8 ppb and mainly concentrated in urban areas, while the contributions from mini-light duty trucks (LDT) and HDT were 3.5–4.8 and 3.7–6.2 ppb and mainly concentrated in suburban areas. Through scenario analysis that removed emissions from specific types of vehicles, we found removing LDPV emissions led to decreases in daytime O3 concentration by 0.3–3.8 ppb. In contrast, removing MDPV emissions led to notable O3 increases by 4.0–11.8 ppb at rush hours. Removing LDT and HDT emissions resulted in 0.6–8.0 ppb increases in nocturnal O3 concentrations while 0.8–2.0 ppb decreases during the afternoon. This research highlights the necessity of tailoring control strategies for different vehicle types to effectively reduce O3 levels in Beijing and provides useful information for decision-makers to formulate effective measures of vehicle management in the future.

Long-term exposure to low-level ozone and the risk of hypertension: A prospective cohort study conducted in a low-pollution region of southwestern China

BackgroundThe current evidence regarding the association between long-term exposure to ozone (O3) and hypertension incidence is limited and inconclusive, particularly at low O3 concentrations. Therefore, our research aims to investigate the potential link between long-term O3 exposure and hypertension in a region with low pollution levels. MethodsFrom 2010 to 2012, we conducted a cohort prospective study by recruiting nearly 10,000 attendees through multistage cluster random sampling in Guizhou Province, China. These individuals were followed up from 2016 to 2020, and 5563 cases were finally included in the analysis. We employed a high-resolution model with both temporal and spatial accuracy to estimate the maximum daily 8-h average O3 and utilized annual average O3 concentrations for three exposure periods (2009_10, 2007_10, 2005_10) as the exposure indicator. Time-dependent covariates Cox regression model was exerted to estimate the hazard ratios (HRs) of hypertension incidence. Generalized linear model was employed to assess the association between O3 and systolic, diastolic, pulse, and mean arterial pressure. The dose-response curve was explored using a restricted cubic spline function. Results1213 hypertension incidents occurred during 39,001.80 person-years, with an incidence density of 31.10/1000 Person Years (PYs). The average O3 concentrations during the three exposure periods were 66.76 μg/m3, 67.85 μg/m3, and 67.21 μg/m3, respectively. Per 1 μg/m3 increase in O3 exposure was associated with 11 % increase in the incidence of hypertension in the single-pollution model, and the association was more pronounced in Han, urban, and higher altitude areas. SBP, PP, and MAP were increased by 0.619 (95 % CI, 0.361–0.877) mm Hg, 0.477 (95 % CI, 0.275–0.679) mm Hg, 0.301 (95 % CI, 0.127–0.475) mm Hg, respectively. Furthermore, we observed a nonlinear exposure-response relationship between O3 and hypertension incidence. ConclusionsLong-term exposure to low-level O3 exposure is associated with an increased risk of hypertension.

Seasonal patterns of influenza incidence and the influence of meteorological and air pollution factors in Thailand during 2009–2019

Influenza, an acute respiratory illness, remains a significant public health challenge, contributing substantially to morbidity and mortality worldwide. Its seasonal prevalence exhibits diversity across regions with distinct climates. This study aimed to explore the seasonal patterns of influenza and their correlation with meteorological and air pollution factors across six regions of Thailand. We conducted an analysis of monthly average temperature, relative humidity, precipitation, PM10, NO2, O3 concentrations, and influenza incidence data from 2009 to 2019 using wavelet analysis. Our findings reveal inconsistent biannual influenza prevalence patterns throughout the study period. The biannual pattern emerged during 2010–2012 across all regions but disappeared during 2013–2016. However, post-2016, the biannual cycles resurfaced, with peaks occurring during the rainy and winter seasons in most regions, except for the southern region. Wavelet coherence reveals that relative humidity can be the main influencing factor for influenza incidence over a one-year period in the northern, northeastern, central, Bangkok-metropolitan, and eastern regions, not in the southern region during 2010–2012 and 2016–2018. Similarly, precipitation can drive the influenza incidence at the same period for the northeastern, central, Bangkok-metropolitan, and eastern regions. PM10 concentration can influence influenza incidence over a half-year period in the northeastern, central, Bangkok-metropolitan, and eastern regions of Thailand during certain years. These results enhance our understanding of the temporal dynamics of influenza seasonality influenced by weather conditions and air pollution over the past 11 years. Such knowledge is invaluable for resource allocation in clinical settings and informing public health strategies, particularly in navigating Thailand's climatic complexities.

Prenatal ozone exposure and variations of the gut microbiome: Evidence from a Chinese mother-infant cohort

BackgroundThe gut microbiome is central to human health, but the potential impact of ozone (O3) exposure on its establishment in early life has not been thoroughly examined. Therefore, this study aimed to investigate the relationship between prenatal O3 exposure and the variations of the human gut microbiome during the first two years of life. DesignA cohort study design was used. Pregnant women in the third trimester were recruited from an obstetric clinic, and long-term follow-ups were conducted after delivery. The gut microbiome was analyzed using the 16 S rRNA V3-V4 gene regions. Functional pathway analyses of gut microbial communities in neonates were performed using Tax4fun. The average concentrations of ambient O3 and other air pollutants from pregnancy to delivery were calculated using the China High Air Pollutants (CHAP) dataset, based on the permanent residential addresses of participants. Multiple linear regression and mixed linear models were utilized to investigate the associations between prenatal O3 exposure and gut microbiome features. ResultsPrenatal O3 exposure did not significantly affect the gut microbial alpha diversity of mothers and neonates. However, it was found to be positively associated with the gut microbial alpha diversity in 24-month-old infants. Prenatal O3 exposure explained 13.1 % of the variation in neonatal gut microbial composition. After controlling for potential covariates, prenatal O3 exposure was associated with neonatal-specific gut microbial taxa and functional pathways. Furthermore, the mixed linear models showed that prenatal O3 exposure was negatively associated with variations of Streptococcus (p-value = 0.001, q-value = 0.005), Enterococcus (p-value = 0.001, q-value = 0.005), Escherichia-Shigella (p-value = 0.010, q-value = 0.025), and Bifidobacterium (p-value = 0.003, q-value = 0.010). ConclusionsThis study is the first to examine the effects of prenatal O3 exposure on gut microbial homeostasis and variations. It demonstrates that prenatal O3 exposure is associated with variations in certain aspects of the gut microbiome. These findings provide novel insights into the dynamics and establishment of the human microbiome during the first two years of life.