Air Pollution Research Articles

A Novel Hybrid Prediction Model of Air Quality Index Based on Variational Modal Decomposition and CEEMDAN-SE-GRU

As the economy rapidly develops, the phenomenon of air pollution is occurring more frequently, impacting on human health and environmental ecosystems. The Air Quality Index (AQI) is an essential index for describing air pollution levels. Accurate AQI prediction provides reliable information for air pollution control and protect human health. Therefore, in this paper, the AQI data of Beijing-Tianjin-Hebei region from 20 May 2014 to 18 November 2023 are used. We propose two basic prediction models based on Complete Ensemble Empirical Modal Decomposition with Adaptive Noise (CEEMDAN) and Gated Recursive Unit (GRU) as well as an improved prediction framework combining Variational Modal Decomposition (VMD). The best mean coefficient of determination (R²) is 0.984, the mean absolute error (MAE) is 2.476, and the R² is more than 0.980 for the prediction of AQI in different regions. These results validate the reliability of this hybrid prediction model.

Multidimensional structural racism and estimated cancer risk from traffic-related air pollution.

Traffic-related air pollutants have been associated with a variety of adverse human health impacts, including cancers. In the United States, numerous studies have documented racial inequities in neighborhood exposures to traffic-related air pollution. Emerging evidence suggests that structural racism may influence neighborhood exposures to air pollutants. However, existing research has largely focused on residential racial segregation, one indicator of structural racism. This study developed a multidimensional measure of structural racism to examine the relationship between structural racism and estimated cancer risk from air pollutants in Georgia. Carcinogenic air toxics data were obtained from the US Environmental Protection Agency's 2019 Air Toxics Screening Assessment and sociodemographic data from the American Community Survey. Guided by stakeholder input, county-level data on residential segregation, education, employment, incarceration, economic status, political participation, and homeownership were used to create a multidimensional county-level structural racism index. Relative risks (RRs) were estimated for associations between structural racism and elevated (top 10% in Georgia) estimated cancer risk from air toxics. Multilevel analyses revealed a significant association between multidimensional structural racism and exposure to carcinogenic traffic-related air pollutants. Neighborhoods in the highest quartile of structural racism exhibited an elevated cancer risk from traffic-related air pollutants (RR,7.84; 95% CI,5.11-12.05) compared to neighborhoods with lower levels of structural racism. Multidimensional structural racism was associated with estimated cancer risk from traffic-related air pollution in Georgia. Findings can inform future studies and policy interventions that address racial inequalities in exposure to traffic-related air pollution.

Removal of antibiotics from aquaculture wastewater using a continuous flow/EC/PMS coupled system

The electricity activated peroxomonosulfate (ion) coupled system (EC/PMS) has important application value in water pollution treatment. However, the traditional batch system commonly used in this coupled system poses significant challenges in treating large volume and low concentration aquaculture wastewater, such as poor mass transfer, long treatment time, and increased risk of secondary pollution. Therefore, this study proposed to introduce the continuous flow operation mode into the EC/PMS system to form a continuous flow electrocatalytic peroxomonosulfate (ion) (CF/EC/PMS) coupling system, achieving 100 % removal of tetracycline (TC) with an initial concentration of 2 mg/L. Subsequently, through cathodic optimization, an 85 % removal efficiency was achieved for antibiotics with secondary pollution risks, such as norfloxacin and NOR. It is worth noting that the secondary pollutants (such as fluoride ions, F−) generated during the degradation process have also successfully achieved a removal efficiency of 70 %. In this system, singlet oxygen (1O2) was the main active species. This system has advantages such as a processing volume of at least 3L, a wide pH range (3–9), low oxidant dosage (PMS = 2 mM), and low energy consumption (EEO = 0.018 kWh/m3 log). The coupling system effectively removes the main pollutants, and the optimized cathode coupling system achieves safe removal of fluorinated drugs, reducing the risk of secondary pollution. In summary, this study has the characteristics of low cost and engineering applicability, providing a promising method for economically, efficiently, and environmentally friendly treatment of aquaculture wastewater.

Theoretically design of 2D penta-BN2/penta-Graphene wdW heterostructure for NO gas sensing implications: a first-principles study

As air pollution becomes more and more serious, the detection of harmful gas of NO has become an urgent need in daily life. In this paper, the electronic and gas-sensing properties of penta-BN2/penta-Graphene heterojunction (P-BN2/P-G) are studied by density functional theory and non-equilibrium Green's function method. The analysis results indicate that the P-BN2/P-G heterojunction has metallic properties. The electronic structures in combination with the adsorption behavior shows that the P-BN2/P-G heterojunction can chemically adsorb NO gas molecules, and there is obvious charge transfer, indicating that it has high gas sensitivity to NO gas. In addition, the sensing performance of the gas sensor constructed by NO adsorption on upper, middle and lower layers of the P-BN2/P-G heterojunction is deeply studied. Transport calculations show that when NO is adsorbed on the upper and middle layers of the P-BN2/P-G heterojunction-based gas sensor, the current of the device decreases significantly. When adsorbed on the lower layer, the current shows a trend of first decreasing and then increasing. Under a bias of 0.1 V, the gas sensitivity can reach up to 49% when NO is adsorbed in the middle layer, which is substantially higher than that of the P-BN2 monolayer device. It can be seen that the gas sensitivity is significantly improved after forming the heterojunction. In addition, the bias transport spectrum and scattering state can reveal the change in device current caused by the adsorption of NO gas molecules, thereby clarifying its microscopic mechanism. Finally, all the findings indicate that penta-based materials can be used as a very promising gas-sensitive material for detecting NO.

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.

Residential exposure to transportation noise and risk of incident atrial fibrillation: a pooled study of 11 prospective Nordic cohorts

Transportation noise has been linked with cardiometabolic outcomes, yet whether it is a risk factor for atrial fibrillation (AF) remains inconclusive. We aimed to assess whether transportation noise was associated with AF in a large, pooled Nordic cohort. We pooled data from 11 Nordic cohorts, totaling 161,115 participants. Based on address history from five years before baseline until end of follow-up, road, railway, and aircraft noise was estimated at a residential level. Incident AF was ascertained via linkage to nationwide patient registries. Cox proportional hazards models were utilized to estimate associations between running 5-year time-weighted mean transportation noise (Lden) and AF after adjusting for sociodemographics, lifestyle, and air pollution. We identified 18,939 incident AF cases over a median follow-up of 19.6 years. Road traffic noise was associated with AF, with a hazard ratio (HR) and 95% confidence interval (CI) of 1.02 (1.00-1.04) per 10-dB of 5-year mean time-weighted exposure, which changed to 1.03 (1.01-1.06) when implementing a 53-dB cut-off. In effect modification analyses, the association for road traffic noise and AF appeared strongest in women and overweight and obese participants. Compared to exposures ≤40dB, aircraft noise of 40.1-50 and>50dB were associated with HRs of 1.04 (0.93-1.16) and 1.12 (0.98-1.27), respectively. Railway noise was not associated with AF. We found a HR of 1.19 (1.02-1.40) among people exposed to noise from road (≥45dB), railway (>40dB), and aircraft (>40dB) combined. Road traffic noise, and possibly aircraft noise, may be associated with elevated risk of AF. NordForsk.

Sufficient sleep and physical activity can relieve the effects of long-term exposure to particulate matter on depressive symptoms among 0.31 million children and adolescents from 103 counties in China.

Although long-term exposures to air pollutants have been linked to mental disorders, existing studies remain limited and inconsistent. We investigated the relationship between exposure to particulate matter (PM) and depressive symptoms, as well as the potential role of sleep duration and physical activity. Using the surveillance data (2019 to 2022) of common diseases and risk factors among 312,390 students aged 10-25years, logistic regression, generalized liner model (GLM) and restricted cubic spline (RCS) were employed to investigate the relationship between long-term exposure to PM and depressive symptoms. Significant associations were found between PM1 (OR=1.21, 95% CI: 1.12-1.32), PM2.5 (OR=1.24, 95% CI: 1.19-1.38), and PM10 (OR=1.87, 95% CI: 1.69-2.07) and increased risks of depressive symptoms. Sleep duration and physical activity relieved these associations. The odds ratios (ORs) of PM1, PM2.5, and PM10 on depressive symptoms were lower in group with sufficient sleep (1.02 vs. 1.49, 1.20 vs. 1.80, 2.15 vs. 2.23), lower in group with high level MVPA (1.13 vs. 1.48, 1.14 vs. 1.58, 1.85 vs. 2.38), and lower in group with high level outdoor activity (1.19 vs. 1.55, 1.23 vs. 1.63, 1.83 vs. 2.72). Conclusions about causality remain speculative because of the cross-sectional design. Sufficient sleep duration and outdoor activity may mitigate the decline in mental health among adults in developing countries caused by long-term exposure to PM. This contribution enhanced our understanding of the mechanisms linking air pollution to mental health.

Vocs pollution and respiratory exposure in commercial and residential underground parking garages

The indoor air quality in Underground Parking Garages (UPGs) has deteriorated significantly, primarily due to the high concentrations of particulate matter and volatile organic compounds (VOCs) emitted by idling or low-speed motor vehicles. However, the compositional characteristics and respiratory exposure to VOCs in UPGs have not been quantitatively analyzed. To establish a method for investigating the respiratory exposure to VOCs among different populations in UPGs, a three-dimensional dynamic diffusion model of indoor pollutants was developed based on monitoring data from 116 components in various UPGs in a large city in northern China. The results indicated that air pollution in underground spaces poses significant health risks to workers and children. Furthermore, a comprehensive approach is essential for improving ventilation capacity and air quality in underground transportation spaces.

Clearing the Air: Acute Invasive Fungal Rhinosinusitis in Hematologic Cancer Patients.

Air quality has been shown to impact the rates of fungal infection of the airway, causing diseases such as acute invasive fungal rhinosinusitis (AIFRS), particularly in immunocompromised patients. We theorize that patients with hematologic malignancies in units with aging air handling units (AHUs) have a higher attack rate of AIFRS. Retrospective chart review identified patients with hematologic malignancy and AIFRS in two distinct and equal time periods between 2013 and 2022, representing the presence of aging AHUs and new AHUs, respectively. Cubic feet per minute (CFM) air flows, AIFRS attack rates, and clinical data were compared between the two groups and statistical analyses performed. The older AHUs produce air flow of 27,610 CFM and the newer AHUs produce air flow of 80,000 CFM. There were 18 patients with air supplied by older AHUs and 7 patients with air supplied by new AHUs who developed AIFRS. There was a significantly higher AIFRS attack rate for patients supplied by the older AHUs compared with patients supplied by newer AHUs (p = 0.033). The patients supplied by the older AHUs tended to be younger. The white blood cell counts, absolute neutrophil counts, and the mean time to diagnosis did not differ between the two groups. To our knowledge, this is the first study to examine AIFRS in immunocompromised patients' inpatient environment. Further research should explore whether higher CFM AHUs can decrease this disease among our most vulnerable patients. 3 Laryngoscope, 134:4466-4470, 2024.

Characteristics of PM2.5-bound water-soluble inorganic ions generated during cooking

Commercial cooking is an important source of PM2.5, which adversely affects air quality, posing threats to human health. However, few studies have examined the effects of commercial cooking on outdoor air quality. We aimed to analyze characteristics of outdoor PM2.5 and ions from commercial cooking during cooking and non-cooking times in a popular restaurant area at Nankai University. The acidity and alkalinity of atmospheric PM2.5 based on the equivalent values of anions and cations and the formed compounds based on the ion concentrations and correlations between them were determined. The results showed that the mean PM2.5 concentration at the snack street during cooking times was 120.39 ± 58.52 μg/m3, approximately 1.4 times higher than at the comparison point. The total concentration of water-soluble inorganic ions accounted for approximately half of the PM2.5 emissions at both sampling points. High concentrations of Na+, NO3−, and SO42− were found at both sampling points. We found that NH4NO3, CaSO4, and CaCl2 formed at the snack street, whereas Ca(NO3)2, NH4NO3, and (NH4)2SO4 formed at the comparison point. Based on our analysis of the acid-base balance slopes, the atmospheric PM2.5 was alkaline. These results elucidate the characteristics of PM2.5-bound water-soluble inorganic ions formed during cooking.

Air quality and health benefits of achieving carbon-neutrality in building sector over Beijing, China

To meet the goal of the Paris Agreement, China pledges to realize the “Dual Carbon” targets by 2060. As the capital of China, Beijing plays a leading role in becoming zero-emission or carbon neutral in the future. We project the pollutants emissions of building sector based on current strict clean air policies (PO scenario) and China's carbon neutrality target by 2060 (CN scenario) from 2019 to 2050. Results show that PM2.5 concentration will increase by 2.62 μg/m3 under PO scenario; under the CN scenario, ozone concentration will increase by 2.53 μg/m3 but PM2.5 concentration will reduce by 9.04 μg/m3. It is projected that China carbon neutrality goals could avoid 11.12% of PM2.5-related health burden; With strict clean air policies, health burdens of ozone (3.9%) and PM2.5 (4.1%) could be avoided, respectively. This study highlights the importance of achieving co-benefits of air quality and public health.

Air quality monitoring system based on low power wide area network technology at public transport stops

<span>Mass migration from rural areas to urban areas has caused problems of traffic congestion, high industrial concentration and inequity in the distribution of housing in the world's capitals, generating a significant threat to sustainable development and public health due to air pollution air. In the Peruvian context, the importance of real-time monitoring of air quality is highlighted according to the standards established by the government. Several studies propose real-time environmental monitoring systems using internet of thing (IoT) technologies, electrochemical and optical sensors to measure pollutants, highlighting the need for data analysis. The objective of the paper is to show the implementation of IoT devices called sensor nodes, with long range wide area network (LoRaWAN) transmission technology for continuous monitoring of polluting gas concentrations. In addition, they are integrated into a central node called gateway to perform real-time monitoring through a web application. As an initial result, IoT devices demonstrated their effectiveness for real-time monitoring. Despite being a prototype-level result, the next stage involves its deployment at public transport stops in Lima. Overcoming the limitations of the solution, this paper establishes the foundation for future research on pollution and public health.</span>

Comparing Airborne and Along-Sidewall Ground-Based Measurements to Retrieve Thermal and PM10 Concentration Profiles in Two Alpine Valleys

Abstract The paper aims at investigating the effectiveness of estimating vertical profiles of air temperature and PM10 concentrations in Alpine valleys through ground stations positioned at different altitudes on one valley sidewall (i.e., pseudovertical profiles). Two case studies in the Italian Alps are investigated: Chiese Valley in Trentino Province and Camonica Valley in the Lombardy region. Vertical profiles of temperature and PM10 concentrations were derived from airborne measurements at the center of the two valleys by means of low-cost sensors installed on a drone during summer 2019 and a tethered balloon during winter 2020. At the same time, five stations, equipped with the same kind of low-cost sensors, simultaneously monitored the same variables on one mountain slope. Comparisons between pseudoprofiles and airborne soundings revealed that ground stations well approximated temperature and PM10 soundings during the night and early morning, while temperatures along the slopes were higher than in the center of the valley during daytime, due to solar radiative heating, with larger differences in summer than in winter. On the contrary, some episodes with PM10 concentrations slightly higher in the valley center than on the slope were recorded, due to transport events and upslope winds. Nonetheless, the pseudoprofiles based on slope ground measurements faithfully reproduced the vertical gradients of both air temperature and PM10 if compared to those assessed from the soundings performed at the center of the two valleys. Results show that pseudovertical profiles can be a reliable and inexpensive method for continuous monitoring of vertical air temperature and PM10 distribution in mountain valleys. Significance Statement The purpose of this study is to understand whether ground-based measurements of air temperature and particulate matter on mountain slopes can be used as suitable surrogates of vertical atmospheric soundings with tethered balloons or drones in mountain environment. This is important because balloon and drone soundings are expensive and regulative constrained. The knowledge of the vertical distribution of air temperature is crucial to predict the distribution of air pollutants in valleys, namely, the particulate matter emitted by wood burning. Our results showed that ground-based measurements on mountain slopes made with low-cost sensors can satisfactorily reproduce vertical gradients of air temperature and distribution of particulate matter in a reliable and inexpensive way.

The source of volatile organic compounds pollution and its effect on ozone in high-altitude areas

Volatile organic compounds (VOCs) are crucial precursors in the formation of ozone (O3). The sources of pollution are complex and significantly impact O3 generation. Long-term exposure to high-concentration O3 environments causes serious damage to organisms. High-altitude areas experience continuous high temperatures and strong solar radiation, which can easily produce O3 through photochemical reactions, making these areas prone to frequent air pollution. This study utilizes the National Positioning Station of the Yinchuan Urban Ecosystem in Ningxia to conduct field synchronous observations, gathering data on VOCs, meteorological variables, and O3. By employing machine learning algorithms, we examined the seasonal distribution characteristics of VOCs, their pollution sources, and their impact on O3. The results show that the seasonal distribution of VOCs areas is low in spring and autumn and high in summer and winter. The components with higher volume fraction contribution are m-tolualdehyde in spring and summer, ethane in autumn, and acetylene in winter. The main emission sources of VOCs pollution are hydrocarbon volatile emission in spring and winter, solvent volatilization emission in summer, and industrial sources in autumn. VOCs have a negative effect on O3, with a greater impact in winter and spring, evidenced by standardized effect values of −0.26 and −0.24. The key components affecting O3 in VOCs vary by season. Aromatic hydrocarbons are the key components in spring and winter, with contribution rates of 22 % and 21.3 %. Alkenes are the key components in summer and autumn (24.5 % and 26.8 %). Among meteorological variables, temperature is the key factor affecting O3, while wind speed is the key factor affecting O3 only in winter. This study aims to clarify the sources of VOCs pollution in different seasons and their impact on O3, providing a theoretical basis and technical support for the prevention and control of VOCs and O3 pollution in high-altitude areas.

Continuous measurement of the dynamics of residential indoor and outdoor NO2 and the contributions to human exposure

In residential environment, NO2 is an important air pollutant. Yet, the dynamics of indoor NO2 and source contributions to human exposure are not well understood. Here, we conducted a continuous NO2 measurement in and out of eight households in Guangzhou, China. Paired high time-resolution NO2 data sets indoors (kitchen, living room) and outdoors (balcony) were obtained with NO2 monitors. We summarized the indoor and outdoor NO2 levels, identified temporal variation patterns, analyzed indoor-outdoor relationships, and quantified source contributions to indoor NO2 exposure. Indoor NO2 were overall higher than outdoor NO2, and in most cases, the highest NO2 levels were observed in the kitchen. NO2 in the kitchen was characterized by multiple spikes associated with use of gas stoves, while NO2 in the living room was also elevated but the peaks were generally smaller. The indoor-outdoor correlations were stronger in winter than in summer, and were stronger in nighttime than daytime. The sources contributing to indoor NO2 were separated with a conceptual model. Overall, the outdoor NO2 source contributed 73% – 76% of the NO2 in the kitchen, and 76% – 85% in the living room. The source pattern was quite different: outdoor NO2 sources were present indoors all the time; by contrast, indoor NO2 sources were present sporadically but with a very high contribution. This has important implication to the exposure assessment that indoor NO2 sources lead to short-term high exposure, and deserves attention regarding acute health effects.

EAP statement: Communicating air pollution risks to children and families: European Academy of Paediatrics Strategic Advisory Group on Ethics on behalf of the European Academy of Paediatrics, EAP, Brussels, Belgium.

EAP statement: Communicating air pollution risks to children and families: European Academy of Paediatrics Strategic Advisory Group on Ethics on behalf of the European Academy of Paediatrics, EAP, Brussels, Belgium.

PM2.5 Induces Developmental Neurotoxicity in Cortical Organoids

There is mounting evidence implicating the potential neurotoxic effects of PM2.5 during brain development, as it has been observed to traverse both the placental barrier and the fetal blood-brain barrier. However, the current utilization of 2D cell culture and animal models falls short in providing an accurate representation of human brain development. Consequently, the precise mechanisms underlying PM2.5-induced developmental neurotoxicity in humans remain obscure. To address this research gap, we constructed three-dimensional (3D) cortical organoids that faithfully recapitulate the initial stages of human cerebral cortex development. Our goal is to investigate the mechanisms of PM2.5-induced neurotoxicity using 3D brain organoids that express cortical layer proteins. Our findings demonstrate that exposure to PM2.5 concentrations of 5 μg/mL and 50 μg/mL induces neuronal apoptosis and disrupts normal neural differentiation, thereby suggesting a detrimental impact on neurodevelopment. Furthermore, transcriptomic analysis revealed PM2.5 exposure induced aberrations in mitochondrial complex I functionality, which is reminiscent of Parkinson's syndrome, potentially mediated by misguided axon guidance and compromised synaptic maintenance. This study is a pioneering assessment of the neurotoxicity of PM2.5 pollution on human brain tissues based on 3D cortical organoids, and the results are of great significance in guiding the formulation of the next air pollution prevention and control policies in China to achieve the sustainable improvement of air quality and to formulate pollution abatement strategies that can maximize the benefits to public health.

Assessing the impact of the National Clean Air Programme in Uttar Pradesh's non-attainment cities: a prophet model time series analysis

BackgroundUttar Pradesh, India’s largest state, faces critical pollution levels, necessitating urgent action. The National Clean Air Programme (NCAP) targets a 40% reduction in particulate pollution by 2026. This study assesses the NCAP’s impact on 15 non-attainment cities in Uttar Pradesh using the Prophet forecasting model. MethodsMonthly data from 2016 to 2023 on AQI and PM10 concentrations were sourced from the Uttar Pradesh Pollution Control Board. Significant changes in mean AQI and PM10 levels from 2017 to 2023 were evaluated using the Friedman Test. Prophet models forecasted PM10 concentrations for 2025-26, with relative percentage changes calculated and model evaluation metrics assessed. FindingsMost cities exhibited unhealthy air quality. Jhansi had the lowest AQI (72·73) in 2023, classified as 'moderate' by WHO standards. Gorakhpur consistently showed 'poor' AQI levels, peaking at 249·31 in 2019. Western Uttar Pradesh cities such as Ghaziabad, Noida, and Moradabad had significant pollution burdens. Predictions showed Bareilly with over a 70% reduction in PM10 levels, Raebareli 58%, Moradabad 55%, Ghaziabad 48%, Agra around 41%, and Varanasi 40%, meeting NCAP targets. However, Gorakhpur and Prayagraj predicted increases in PM10 levels by 50% and 32%, respectively. Moradabad’s model showed the best performance with an R2 of 0·81, MAE of 17·27 μg/m3, and MAPE of 0·10. InterpretationForecasting PM10 concentrations in Uttar Pradesh's non-attainment cities offers policymakers substantial evidence to enhance current efforts. While existing measures are in place, our findings suggest that intensified provisions may be necessary for cities predicted to fall short of meeting program targets. The Prophet model's forecasts can pinpoint these at-risk areas, allowing for targeted interventions and regional adjustments to strategies. This approach will help promote sustainable development customized to each city's specific needs. FundingNo funding was issued for this research.

Communicating air quality data: a co-creation approach

Communicating air quality data: a co-creation approach

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).