Acute effect of multiple ozone metrics on mortality by season in 34 Chinese counties in 2013-2015

Increased ground-level O3 during the COVID-19 pandemic in China aggravates human health risks but has little effect on winter wheat yield

In January 2020, the novel coronavirus (COVID-19) outbreak emerged in China, prompting the enforcement of stringent lockdown measures nationwide to contain its spread. Multiple studies have demonstrated that these measures successfully reduced the levels of air pollutants except for ozone (O3). However, the potential risks of nationwide O3 changes during this period remain uncertain. To address this gap, we evaluated the ecological and health effects of O3 using hourly O3 data from 1 January to 17 June in both 2020 and 2019. Our results indicated that all health and ecological indicators, except SUM06 (sum of all hourly O3 over 60 ppb), during the COVID-19 pandemic in 2020 increased most obviously in Stages 2 and 3 with the strictest control measures, compared to the same period in 2019. The national premature deaths due to short-term O3 exposure during Stages 2-3 in 2020 totaled 146,558 (95% CI: 79,386-213,730) for all non-accidental causes and 82,408 (95% CI: 30,522-134,295) for cardiovascular diseases, increasing by 18.78% and 18.76% in 2019, respectively. The most significant increase in health risks occurred in Hubei, followed by Jiangxi, Zhejiang, Hunan, and Shaanxi. In addition, the estimated national winter wheat production losses (WWPL) attributable to O3 amounted to 50.6 and 51.1 million metric tons for 2019 and 2020, respectively. Among the major winter wheat-producing provinces, Anhui and Jiangsu experienced a larger increase in WWPL, while Shandong and Hebei suffered a greater decrease in 2020 compared to 2019, resulting in little overall change in WWPL between the two years. These findings provided direct evidence of the harmful effects of O3 during the COVID-19 pandemic and serve as a valuable reference for future air pollution control.

Long-term exposure to ambient ozone and cardiovascular diseases: Evidence from two national cohort studies in China

INTRODUCTION

The health effects of ambient ozone have been investigated in many previous studies. However, the effects of long-term exposure to ambient ozone on the incidence of cardiovascular disease (CVD) remain inconclusive.

OBJECTIVES

To estimate the associations of long-term exposure to maximum daily 8-hours average ozone (MDA8 O3) with the incidence of total CVD, heart disease, hypertension, and stroke.

METHODS

This was a prospective cohort study, and the data was obtained from the China Health and Retirement Longitudinal Survey (CHARLS) implemented during 2011-2018 and the China Family Panel Studies (CFPS) implemented during 2010-2018. We applied a Cox proportional hazards regression model to evaluate the associations of MDA8 O3 with total CVD, heart disease, hypertension, and stroke risks, and the corresponding population-attributable fractions (PAF) attributable to MDA8 O3 were also calculated. All analyses were conducted by R software.

RESULTS

The mean MDA8 O3 concertation of all included participants in the CHARLS and CFPS were 51.03 part per billion (ppb) and 51.15 ppb, respectively. In the CHARLS including 18,177 participants, each 10 ppb increment in MDA8 O3 concentration was associated with a 31% increase [hazard ratio (HR) = 1.31, 95% confidence interval (CI): 1.22-1.42] in the risk of incident heart disease, and the corresponding population-attributable fractions (PAF) was 13.79% [10.12%-17.32%]. In the CFPS including 30,226 participants, each 10 ppb increment in MDA8 O3 concentration was associated with an increase in the risk of incident total CVD (1.07 [1.02-1.13]), and hypertension (1.10 [1.03-1.18]). The PAFs of total CVD, and hypertension attributable to MDA8 O3 were 3.53% [0.82%-6.16%], and 5.11% [1.73%-8.38%], respectively. Stratified analyses showed greater associations in males, urban areas, and Southern China.

CONCLUSIONS

Long-term exposure to MDA8 O3 may increase the incidence of CVD. Therefore, the policies that control O3 and related precursors are persistently needed.

Adverse short-term effects of ozone on cardiovascular mortalities modified by season and temperature: a time-series study

Introduction

Ambient ozone pollution becomes critical in China. Conclusions on the short-term effects of ozone on cardiovascular mortality have been controversial and limited on cause-specific cardiovascular mortalities and their interactions with season and temperature. This research aimed to investigate the short-term effects of ozone and the modifications of season and temperature on cardiovascular mortality.

Methods

Cardiovascular death records, air pollutants, and meteorological factors in Shenzhen from 2013 to 2019 were analyzed. Daily 1-h maximum of ozone and daily maximum 8-h moving average of ozone were studied. Generalized additive models (GAMs) were applied to evaluate their associations with cardiovascular mortalities in sex and age groups. Effect modifications were assessed by stratifying season and temperature.

Results

Distributed lag impacts of ozone on total cardiovascular deaths and cumulative effects on mortality due to ischemic heart disease (IHD) were most significant. Population under 65 years old was most susceptible. Majority of significant effects were found in warm season, at high temperature, and at extreme heat. Ozone-associated risks in total deaths caused by hypertensive diseases reduced in warm season, while risks in IHD in males increased at high temperature. Extreme heat enhanced ozone effects on deaths caused by CVDs and IHD in the population under 65 years old.

Discussion

The revealed cardiovascular impacts of ozone below current national standard of air quality suggested improved standards and interventions in China. Higher temperature, particularly extreme heat, rather than warm season, could significantly enhance the adverse effects of ozone on cardiovascular mortality in population under 65 years old.

Impact of ground-level ozone exposure on sleep quality and electroencephalogram patterns at different time scales

Ozone exposure is associated with various adverse health outcomes, but its impact on sleep quality is uncertain. Here we assessed the causal effect of long-term (yearly and monthly) exposure to ozone on nocturnal workday sleep time in a national representative sample from the China Family Panel Study, using a difference-in-differences approach. We further followed ninety healthy Chinese young adults four times in four seasons from September 2020 to June 2021, measured their daily sleep architecture using accelerometers, ascertained daily ozone exposure, recorded 5-min eye-closed resting-state electroencephalogram (EEG) signals at the last day of each one-week-long measurement session, and explored the effect of ozone exposure on objectively-measured sleep architecture. In the national sample, we found that every 1 interquartile range (IQR) μg/m³ increase in yearly and monthly ozone exposure was causally associated with 7.31 (p = 0.0039) and 4.19 (p = 0.040) minutes decline in nocturnal workday sleep time; the dose-response curve represented a quasi-linear pattern with no safety threshold, and plateaued at higher concentrations. In the small-scale study with objectively-measured sleep architecture, we found that every 1 IQR μg/m³ increase in the weekly ozone exposure was associated with 5.33 min decrease in night-time total sleep time (p = 0.031), 1.63 percentage points decrease in sleep efficiency (p < 0.001), 1.99 min increase in sleep latency (p = 0.0070), and 5.34 min increase in wake after sleep onset time (p = 0.0016) in a quasi-linear pattern. Notably, we found the accumulating trend of ozone exposure on sleep quality during both the short-term and long-term periods. We also found that short-term ozone exposure was associated with altered EEG patterns, mediated by sleep quality. This study indicates that long-term and short-term ozone exposures have negative and accumulating impacts on sleep quality and might impair brain functioning. More hidden health burdens of ozone are worth exploring.

Comparison of the association between different ozone indicators and daily respiratory hospitalization in Guangzhou, China

Background

Epidemiological studies have widely proven the impact of ozone (O₃) on respiratory mortality, while only a few studies compared the association between different O₃ indicators and health.

Methods

This study explores the relationship between daily respiratory hospitalization and multiple ozone indicators in Guangzhou, China, from 2014 to 2018. It uses a time-stratified case-crossover design. Sensitivities of different age and gender groups were analyzed for the whole year, the warm and the cold periods. We compared the results from the single-day lag model and the moving average lag model.

Results

The results showed that the maximum daily 8 h average ozone concentration (MDA8 O₃) had a significant effect on the daily respiratory hospitalization. This effect was stronger than for the maximum daily 1 h average ozone concentration (MDA1 O₃). The results further showed that O₃ was positively associated with daily respiratory hospitalization in the warm season, while there was a significantly negative association in the cold season. Specifically, in the warm season, O₃ has the most significant effect at lag 4 day, with the odds ratio (OR) equal to 1.0096 [95% confidence intervals (CI): 1.0032, 1.0161]. Moreover, at the lag 5 day, the effect of O₃ on the 15-60 age group was less than that on people older than 60 years, with the OR value of 1.0135 (95% CI: 1.0041, 1.0231) for the 60+ age group; women were more sensitive than men to O₃ exposure, with an OR value equal to 1.0094 (95% CI: 0.9992, 1.0196) for the female group.

Conclusion

These results show that different O₃ indicators measure different impacts on respiratory hospitalization admission. Their comparative analysis provided a more comprehensive insight into exploring associations between O₃ exposure and respiratory health.

Associations between Different Ozone Indicators and Cardiovascular Hospital Admission: A Time-Stratified Case-Crossover Analysis in Guangzhou, China

Epidemiological studies reported that ozone (O₃) is associated with cardiovascular diseases. However, only few of these studies examined the impact of multiple O₃ indicators on cardiovascular hospital admissions. This study aimed to explore and compare the impacts of different O₃ indicators on cardiovascular hospital admissions in Guangzhou, China. Based upon the data on daily cardiovascular hospital admissions, air pollution, and meteorological factors in Guangzhou from 2014 to 2018, a time-stratified case-crossover design model was used to analyze the associations between different O₃ indicators and cardiovascular hospital admissions. Moreover, the sensitivities of different age and gender groups were analyzed for the whole year and different seasons (i.e., warm and cold). During the warm season, for the single-pollutant model, the odds ratio (OR) value of cardiovascular hospital admissions was 1.0067 (95% confidence interval (CI): 1.0037, 1.0098) for every IQR increase in MDA8 O₃ at a lag of five days. The effect of O₃ on people over 60 year was stronger than that on the 15-60 years age group. Females were more sensitive than males to O₃ exposure. These results provided valuable references for further scientific research and environmental improvement in Guangzhou. Given that short-term O₃ exposure poses a threat to human health, the government should therefore pay attention to prevention and control policies to reduce and eliminate O₃ pollution and protect human health.

Risk of illness-related school absenteeism for elementary students with exposure to PM2.5 and O3

Air pollution addresses short-term health effects on morbidity, especially for children. Assessing the impacts of air pollution on elementary students is critical for developing preparedness response strategies for this sensitive group. In the 2016-17 academic year, up to 687,748 groups of illness-related absence records and the information on whether the absentee had gone to a hospital or not were collected from 2564 elementary schools across Jiangsu Province China. We explored the associations between air pollution and illness-related records using a time-stratified case-crossover analysis with distributed lag non-linear design. An increase of 10 μg/m³ in the current-day concentration of PM_2.5 and O₃ was positively associated with illness-related absenteeism overall. The excess risk of absenteeism was 4.52 % (95%CI 4.37-4.67 %) for PM_2.5 and 0.25 % (95%CI 0.01-0.36 %) for O₃. The risk associated with O₃ was boosted for the frequent absentees who tended to have basic diseases or were more vulnerable to infectious diseases. Students in 43.1 % illness-related absenteeism, mainly due to highly infectious diseases, only received home nursing without going to a hospital. The increase in the number of illness cases associated with PM_2.5 and O₃ estimated based on the illness-related absence data was 41.5 % and 18.6 % higher than that evaluated based on hospital visit records. Such underestimations persisted in sensitivity analyses and persisted in subgroups classified by gender or grade. Together, the performance of illness-related absence records far outweighed that of hospital visit data regarding the thorough evaluation of air pollution-related illness cases for elementary students. Improvement in air quality and home health care education are warranted as well for the health benefits of children.

Modification effects of ambient temperature on ozone-mortality relationships in Chengdu, China

A multitude of epidemiological studies have demonstrated that both ambient temperatures and air pollution are closely related to health outcomes. However, whether temperature has modification effects on the association between ozone and health outcomes is still debated. In this study, three parallel time-series Poisson generalized additive models (GAMs) were used to examine the effects of modifying ambient temperatures on the association between ozone and mortality (including non-accidental, respiratory, and cardiovascular mortality) in Chengdu, China, from 2014 to 2016. The results confirmed that the ambient high temperatures strongly amplified the adverse effects of ozone on human mortality; specifically, the ozone effects were most pronounced at > 28 °C. Without temperature stratification conditions, a 10-μg/m³ increase in the maximum 8-h average ozone (O_3-8hmax) level at lag01 was associated with increases of 0.40% (95% confidence interval [CI] 0.15%, 0.65%), 0.61% (95% CI 0.27%, 0.95%), and 0.69% (95% CI 0.34%, 1.04%) in non-accidental, respiratory, and cardiovascular mortality, respectively. On days during which the temperature exceeded 28 °C, a 10-μg/m³ increase in O_3-8hmax led to increases of 2.22% (95% CI 1.21%, 3.23%), 2.67% (95% CI 0.57%, 4.76%), and 4.13% (95% CI 2.34%, 5.92%) in non-accidental, respiratory, and cardiovascular mortality, respectively. Our findings validated that high temperature could further aggravate the health risks of O_3-8hmax; thus, mitigating ozone exposure will be brought into the limelight especially under the context of changing climate.

Effect of ambient O3 on mortality due to circulatory and respiratory diseases in a high latitude city of northeast China

In recent years, O₃ pollution had been worsening in China and became a major challenge for human health. To evaluate the O₃ effects on circulatory and respiratory mortality in Harbin, a high latitude city of northeast China, we applied a time-series study from 2014 to 2016. After collecting data and adjusting for the effects of confounders, we built the generalized additive model to assess the associations between O₃ and mortality at different lag days. The results showed that an interquartile-range (IQR) increase in O₃ concentration corresponded to excess risk (ER) of 2.00% (95%CI: - 0.25-4.30%) for circulatory mortality at lag 0 and 8.02% (95%CI: 4.18-12.01%) for respiratory mortality at lag 2 days in the single-pollutant model. Stratified analysis showed that O₃ had a greater effect on females than on males. The effect of O₃ exposure on circulatory mortality was stronger during the warm period, while the opposite trend was founded for respiratory mortality. The sensitivity analysis showed that the effects of O₃ were relatively independent and the major results were robust.

Spatiotemporal variation of ozone pollution and health effects in China

With the rapid urbanization and industrialization in China, ozone pollution has become increasingly serious and poses a greater threat to human health. In this study, the spatiotemporal distribution of ozone pollution in China's cities and urban agglomerations from 2015 to 2019 was analyzed. The health effects and health economic costs of ozone pollution in China were estimated by applying the environmental Benefits Mapping and Analysis Program-Community Edition (BenMAP-CE) model. The results are as follows: (1) ozone pollution was more serious in Chinese urban agglomerations from 2015 to 2019; (2) the hot spots of ozone concentration mainly distributed in the North China Plain, expanding from north to south; the cold spots decreased year by year and were located in the northeast, northwest, and southwest of China, shifting from northwest to southwest; (3) the seasonal average of ozone concentration in China was the highest in summer, followed by spring and autumn, and the lowest in winter; (4) the number of all-cause premature deaths of ozone pollution in China increased slowly from 2015 to 2019, and the average of urban agglomerations was significantly higher than cities, with similar spatial distribution characteristics as ozone concentration; (5) the health economic costs of ozone pollution from 2015 to 2019 slowly expanded to surrounding cities with Beijing, Shanghai, Xi'an, and Chongqing as the centers of high values, while the low value areas decreased year by year and were mainly concentrated in southwest and northeast China. The health economic costs of ozone pollution at urban agglomerations scale were higher in the eastern coastal regions and lower in the northwest inland regions. Thus, this study presents policy recommendations to provide decision-making reference for realizing the inter-regional prevention and control of ozone pollution.

Efficient monolithic MnOx catalyst prepared by heat treatment for ozone decomposition

The effects of calcined temperature on the properties and ozone decomposition activity of manganese oxide catalysts were investigated under high-humidity, low ozone conditions. An outstanding manganese-based catalyst (MnO_x (260 ℃)) was prepared, which could decompose above 90% (RH = 0%) and 70% (RH = 90%) ozone after 6 h using. Specific characterization showed MnO_x (260 ℃) had excellent properties. XRD results showed MnO_x (260 ℃) was mainly Mn₃O₄ and partially MnO₂. TEM indicated MnO_x (260 ℃) exposed highly active crystal family plan MnO₂ (110), and the lattice fringes of MnO₂ (110) and Mn₃O₄ (103) overlapped. In situ DRIFT showed hydroxyl groups adsorbed on MnO_x (260 ℃) were removed, which is beneficial to inhibiting the inactivation caused by surface water accumulation. O₂-TPD results proven MnO_x (260 ℃) had good oxygen migration ability. XPS results manifested that MnO_x (260 ℃) had the most adsorbed oxygen. In short, when the calcination temperature is appropriate, MnO_x (260 ℃) has coexisted multiple phases, exposed high active crystal family plan and removed surface hydroxyl, which is conducive to the exposure of oxygen vacancies and the inhibition of deactivation.

Quantifying ecological and health risks of ground-level O3 across China during the implementation of the "Three-year Action Plan for Cleaner Air"

After China implemented the Air Pollution Prevention and Control Action Plan (APPCAP), PM_2.5 concentrations decreased but were still higher than national standards in major areas and ozone (O₃) concentration increased unintentionally. To further decrease PM_2.5 concentrations and reduce days with severe air pollution, the government promulgated the "Three-year (2018-2020) Action Plan for Cleaner Air" (the Three-year Action Plan) in 2018. During the three-year Action Plan, a few studies reported a continuous decline in PM_2.5, but it is unclear whether O₃ and its effects also increase with the decrease of PM_2.5 like during APPCAP. In this study, for the first time, we systematically assessed changes in ground-level O₃ concentrations and related ecological and health risks during the period of the Three-year Action Plan using nationwide O₃ measurements. The national MDA8, Exceedance, and SOMO35 indicators were reduced by 3.8%, 28.5%, and 12.6%, respectively, ecological risk indicators of M12, M7, SUM06, AOT40, and W126 were reduced by 5.4%, 5.6%, 19.5%, 15.4%, and 18.6%, respectively, from 2018 to 2020. Spatially, the greatest reduction in all the indicators except MDA8 occurred in Pearl River Delta, followed by Fen Wei Plains, while Beijing-Tianjin-Hebei, Chengdu-Chongqing, and Yangtze River Delta presented relatively small reductions. Between 2018 and 2020, the production losses caused by O₃ for wheat and rice decreased by 21.4% and 17.6%, respectively. Long-term exposure to O₃ across China over 2020 was estimated to cause about 160,795 (95% CI: 81,515-312,983) for all-cause mortality, 107,128 (95% CI: 36,703-173,823) for cardiovascular mortality, and 34,444 (95% CI: 0-72,609) for respiratory mortality, indicating decreases of 9.93%, 9.86%, and 9.78%, respectively, compared to the year 2018. Taken together, our results provided the first direct evidence for China's efforts to control O₃ pollution in recent years.

Association of ambient ozone with pneumonia hospital admissions in Hong Kong and Taipei: A tale of two Southeast Asian cities

Ozone (O₃) is a reactive oxidant exerting both inflammatory and oxidative damages to the respiratory system. With the ground-level O₃ progressively increasing in the past decade, the reevaluation of the pneumonia hospitalization risk from exposure to O₃ is of public health interest. We conducted an ecological time-series study to examine the city-specific association between short-term O₃ exposure and pneumonia hospitalizations in Hong Kong and Taipei, respectively. We linked the daily pneumonia hospitalization count to air pollution concentrations and weather conditions according to the date of admission during 2010-2017. We applied a generalized additive distributed lag model to examine the association while adjusting for time-varying covariates. Stratified analysis by age group and the potential harvesting effect of O₃ were evaluated. We observed the harvesting effects of O₃ on pneumonia hospitalizations in children in both cities and adults in Taipei. The short-term effect of O₃ lasted for around one week. An interquartile range (IQR) increment of daytime 8-hour mean concentration of O₃ distributed over 0-6 lag days in Hong Kong (42.4 μg/m³) was associated with a 7.04% (95% CI: 5.35-8.76%) increase in hospital admissions for elderly pneumonia, while the corresponding cumulative excess risk per IQR increment of O₃ in Taipei (38.7 μg/m³) was 3.41% (95% CI: 1.63-5.22%). Different O₃ metrics, varying degrees of freedom for filtering the temporal trend, and three-pollutant models supported the robustness of the associations. We concluded that short-term O₃ exposure was associated with pneumonia hospitalizations in the elderly population. Understanding the pneumonia hospitalization risk of O₃ will help to inform public health policies in the planning of ozone control strategies and intervention measures to prevent ozone-related pneumonia in vulnerable elderly populations.

Prospects for ozone pollution control in China: An epidemiological perspective

Severe surface ozone pollution has become widespread in China. To protect public health, Chinese scientific communities and government agencies have striven to mitigate ozone pollution. However, makers of pollution mitigation policies rarely consider epidemiological research, and communication between epidemiological researchers and the government is poor. Therefore, this article reviews the current mitigation policies and the National Ambient Air Quality Standard (NAAQS) for ozone from an epidemiological perspective and proposes recommendations for researchers and policy makers on the basis of epidemiological evidence. We review current nationwide ozone control measures for mitigating ozone pollution from four dimensions: the integration of ozone and particulate matter control, ozone precursors control, ozone control in different seasons, and regional cooperation on the prevention of ozone pollution. In addition, we present environmental and epidemiological evidence and propose recommendations and discuss relevant ozone metrics and the criteria values of the NAAQS. We finally conclude that the disease burden attributable to ozone exposure in China may be underestimated and that the epidemiological research regarding the health effects of integrating ozone and particulate matter control is insufficient. Furthermore, atmospheric volatile organic compounds are severely detrimental to health, and related control policies are urgently required in China. We recommend a greater focus on winter ozone pollution and conclude that the health benefits of regional cooperation on ozone control and prevention are salient. We argue that daily average ozone concentration may be a more biologically relevant ozone metric than those currently used by the NAAQS, and accumulating epidemiological evidence supports revision of the standards. This review provides new insight for ozone mitigation policies and related epidemiological studies in China.

Travelling to polluted cities: a systematic review on the harm of air pollution on international travellers' health

RATIONALE FOR REVIEW

In 2019, approximately, 1.4 billion people travelled internationally. Many individuals travel to megacities where air pollution concentrations can vary significantly. Short-term exposure to air pollutants can cause morbidity and mortality related to cardiovascular and respiratory disease, with the literature clearly reporting a strong association between short-term exposure to particulate matter ≤2.5 μm and ozone with adverse health outcomes in resident populations. However, limited research has been conducted on the health impacts of short-term exposure to air pollution in individuals who travel internationally. The objective of this systematic review was to review the evidence for the respiratory and cardiovascular health impacts from exposure to air pollution during international travel to polluted cities in adults aged ≥18 years old.

KEY FINDINGS

We searched PubMed, Scopus and EMBASE for studies related to air pollution and the health impacts on international travellers. Of the initially identified 115 articles that fit the search criteria, 6 articles were selected for the final review. All six studies found indications of adverse health impacts of air pollution exposure on international travellers, with most of the changes being reversible upon return to their home country/city. However, none of these studies contained large populations nor investigated vulnerable populations, such as children, elderly or those with pre-existing conditions.

CONCLUSIONS

More research is warranted to clearly understand the impacts of air pollution related changes on travellers' health, especially on vulnerable groups who may be at higher risk of adverse impacts during travel to polluted cities.

Coordinated control of PM2.5 and O3 is urgently needed in China after implementation of the "Air pollution prevention and control action plan"

To improve air quality, China formulated the Air Pollution Prevention and Control Action Plan (APPCAP) in 2013. In the present study, the changes in the concentration of air pollutants after the implementation of APPCAP were investigated based on nationwide monitoring data. From the results, it is evident that the annual mean concentrations of PM_2.5, PM₁₀, SO₂, and CO show a significant downward trend over 2015-2018, with decreasing rates of 3.4, 4.1, 3.8, and 70 μg m^-3/year, respectively. However, no significant change was found in NO₂ while maximum daily 8 h average O₃ concentration (MDA8 O₃) was increased by 3.4 μg m^-3/year during the four years. Spatially, the highest decrease in PM_2.5 was found in Beijing-Tianjin-Hebei (BTH), followed by central China and northeast China, while the Pearl River Delta (PRD), Yungui Plateau, and northwest China showed less decreases. MDA8 O₃ had a higher increase in BTH, central China, Yangtze River Delta (YRD), and PRD. With the decrease in PM_2.5 in recent years, cumulative population exposure to PM_2.5 gradually decreased, whereas there was still more than 65% of the population exposing to annual PM_2.5 higher than the standard of 35 μg m^-3 in 2018. In contrast, the health effects of O₃ gradually increased with 13.1%, 14.3%, 20.4%, and 21.7% of the population exposed to unhealthy O₃ levels in summer from 2015 to 2018. O₃ pollution is causing severe health risks with estimated nationwide mortality of 70,024 (95% CI: 55,510-84,501), 79,159 (95% CI: 62,750-95,525), 105,150 (95% CI: 83,378-126,852), and 104,404 (95% CI: 82,784-125,956) in the four years, respectively. This clearly shows that the target of air pollution control in China shifts and coordinated control of PM_2.5 and O₃ is urgently needed after the successful implementation of APPCAP.

Macroporous MnO2-based aerogel crosslinked with cellulose nanofibers for efficient ozone removal under humid condition

Atmospheric ozone pollution receives worldwide concerns, and it is a big challenge to search for the practical ozone-decomposition catalyst with good moisture resistance. Herein, a light-weight and high-porosity MnO₂-based hybrid aerogel was synthesized with cellulose nanofibers using a facile ice-template approach, followed by freeze-drying. In the three-dimensional framework, the cellulose nanofibers serve as the skeletons to disperse MnO₂ particles, improving the exposure of active sites on MnO₂. XPS, ¹H NMR and ATR-FTIR demonstrate that MnO₂ particles are effectively combined with cellulose nanofibers through hydrogen bonds, which originate from the abundant surface hydroxyl groups of both components. These consumed surface hydroxyl groups of MnO₂ not only reduce the water adsorption but also avoid the generation of surface-adsorbed H₂O via the reaction with ozone, thus alleviating the catalyst deactivation. In addition, the interconnected macroporous structure enables the rapid diffusion of ozone molecules and facilitates the passage of water molecules, which is conducive to the adsorption and decomposition of ozone on the active sites, i.e. surface oxygen vacancies. Thus, the high and stable ozone conversion was achieved for 150 ppb O₃ under the relative humidity of 50% and the space velocity of 600 L·g^-1·h^-1 within 10 days at room temperature.

Yields and Variability of Ozone Reaction Products from Human Skin

The skin of 20 human participants was exposed to ∼110 ppb O₃ and volatile products of the resulting chemistry were quantified in real time. Yields (ppb product emitted/ppb ozone consumed) for 40 products were quantified. Major products of the primary reaction of ozone-squalene included 6-methyl 5-hepten-2-one (6-MHO) and geranyl acetone (GA) with average yields of 0.22 and 0.16, respectively. Other major products included decanal, methacrolein (or methyl vinyl ketone), nonanal, and butanal. Yields varied widely among participants; summed yields ranged from 0.33 to 0.93. The dynamic increase in emission rates during ozone exposure also varied among participants, possibly indicative of differences in the thickness of the skin lipid layer. Factor analysis indicates that much of the variability among participants is due to factors associated with the relative abundance of (1) "fresh" skin lipid constituents (such as squalene and fatty acids), (2) oxidized skin lipids, and (3) exogenous compounds. This last factor appears to be associated with the presence of oleic and linoleic acids and could be accounted for by uptake of cooking oils or personal care products to skin lipids.

Temporal trends in associations between ozone and circulatory mortality in age and sex in Canada during 1984-2012

BACKGROUND

Considerable research has been conducted on the association between ground-level ozone (ozone) and various causes of mortality, but the relationships by age and sex (biological) have been inconsistent, and temporal trends remain unexplored.

OBJECTIVES

The study goals are to investigate the adverse health effects of short-term exposure to ozone on circulatory mortality by age and sex, and to examine trends in annual health effects.

METHODS

Daily ozone, temperature, and circulatory mortality counts (ICD I00-I99) were collected for 24 urban cities for 29 years (1984-2012). Associations between ozone and circulatory mortality were estimated using generalized additive Poisson models for season (warm vs. cold), age [base (≥1) vs. seniors (>65)], and sex, accounting for confounders (calendar-time, temperature, day of the week). City-specific estimates were pooled to represent national associations through Bayesian hierarchical models.

RESULTS

While the cold season returned insignificant estimates, the warm season showed statistically significant associations: a 10 ppb increase in ozone was associated with 0.7% increase in circulatory mortality with a 95% posterior interval of 0.2%, 1.1%. One-day lagged ozone in the warm season showed little age differences [0.7% (0.23%, 1.12%) vs. 0.8% (0.22%, 1.27%)], but visible sex differences: females were at a higher circulatory mortality risk than males [1.1% (0.31%, 1.71%) vs. 0.3% (-0.46%, 0.98%)]. Annual estimates suggest overall up-down temporal changes; a slightly increasing trend until 2002-2004, and a generally decreasing trend thereafter.

CONCLUSION

This study found noticeable sex-related differences in circulatory mortality attributable to short-term exposure to ozone. Further research is warranted to understand whether sex alone, or unknown interactions with other factors derived the differences, and to clarify the specific biological mechanisms underlying differences in risk estimates between females and males.

Breathing-rate adjusted population exposure to ozone and its oxidation products in 333 cities in China

While PM_2.5 (particles with aerodynamic diameter less than 2.5 µm) concentrations in China are beginning to decline because of pollution abatement measures, ozone (O₃) concentrations continue to rise. In this study, we have used a Monte Carlo approach to estimate breathing-rate adjusted (BRA) population exposure to ozone and its oxidation products based on hourly O₃ measurements collected in 2017 from monitoring stations in 333 Chinese cities. The median measured outdoor O₃ concentration in these cities was 31 ppb, while the median calculated indoor concentrations of ozone and ozone-derived oxidation products were 7.5 ppb and 21 ppb, respectively. The median BRA O₃ exposure concentration was 12 ppb, ranging from 2.2 ppb to 18 ppb among the cities. Eastern and central cities had higher exposure concentrations, while northeastern and western cities had lower. On average, the residents of these cities spent 88% of their time indoors. Consequently, even with breathing rate adjustments, indoor O₃ exposure averaged 50% of the total O₃ exposure nationwide. The median BRA exposure concentration for ozone-derived products was 18 ppb, ranging from 4.5 ppb to 32 ppb among the cities. On average, BRA exposure concentrations were 1.6 times larger for oxidation products than for ozone, while seasonal variations of exposure concentrations were smaller for oxidation products than for ozone. As many of the products of indoor ozone chemistry are toxic, the health consequences of exposure to such products should be further investigated.

Modification Effects of Temperature on the Ozone-Mortality Relationship: A Nationwide Multicounty Study in China

Both ozone exposure and extreme temperatures are found to be significantly associated with mortality; however, inconsistent results have been obtained on the modification effects of temperature on the ozone-mortality association. In the present study, we conducted a nationwide time-series analysis in 128 counties from 2013-2018 to examine whether temperature modifies the association between short-term ozone exposure with nonaccidental and cause-specific mortality in China. First, we analyzed the effects of ozone exposure on mortality at different temperature levels. Then, we calculated the pooled effects through a meta-analysis across China. We found that high-temperature conditions (>75th percentile in each county) significantly enhanced the effects of ozone on nonaccidental, cardiovascular, and respiratory mortality, with increases of 0.44% (95% confidence interval (CI): 0.36 and 0.51%), 0.42% (95% CI: 0.32 and 0.51%) and 0.50% (95% CI: 0.31 and 0.68%), respectively, for a 10 μg/m³ increase in ozone at high temperatures. Stronger effects on nonaccidental and cardiovascular mortality were observed at high temperatures among elderly individuals aged 65 years and older compared with the younger people. Our findings provide evidence that health damage because of ozone may be influenced by the impacts of increasing temperatures, which point to the importance of mitigating ozone exposure in China under the context of climate change to further reduce the public health burden.

Estimation of health and economic benefits based on ozone exposure level with high spatial-temporal resolution by fusing satellite and station observations

In recent years, ozone pollution has become more and more serious in China. Several epidemiological studies have demonstrated the correlation between short-term ozone exposure and several health risks including all-cause mortality, cardiovascular mortality, and respiratory mortality. In this study, the daily ozone exposure levels with 10 km × 10 km resolution were estimated based on satellite data derived from Ozone Monitoring Instrument (OMI) and the monitoring data. The health impacts for potential decrease in the daily ozone concentration and the corresponding economic benefits in 2016 were estimated by applying the environmental Benefits Mapping and Analysis Program-Community Edition (BenMAP-CE) model. By reducing the daily maximum 8-h average concentration of ozone to 100 μg/m³, the estimated avoided all-cause mortalities were 120 × 10³ (95% confidence interval (CI): 67 × 10³, 160 × 10³) cases and the correspondingly economic benefits ranged from 36 to 64 billion CNY using amended human capital (AHC) and willingness to pay (WTP) method in 2016. If the daily maximum 8-h average concentration of ozone were rolled back to 70 μg/m³, the estimated avoided all-cause mortalities were 160 × 10³ (95% CI: 98 × 10³, 230 × 10³) cases and economic benefits ranged from 54 to 95 billion CNY based on AHC and WTP methods.

Effects of ambient ozone concentrations with different averaging times on asthma exacerbations: A meta-analysis

BACKGROUND

Mounting evidence suggests that short-term exposure to ozone increases the risk of asthma exacerbations. However, ozone exposures have been assessed using ambient ozone concentrations averaged over different time periods in different studies.

OBJECTIVE

To evaluate the risks for asthma exacerbations related to ambient ozone measured as 1-hour or 8-hour daily maximum and 24-hour average concentrations.

METHODS

Based on a literature search in PubMed, EMBASE and Web of Science, we identified all time-series studies as of December 4th, 2018 and included 47 eligible studies in our analyses. Asthma exacerbation is defined as the risk for emergency room visits or hospital admissions. Pooled relative risks (RRs) and 95% confidence intervals (95%CIs) for a 10 μg/m3 increase in daily ozone concentration were estimated using random effect models. Subgroup analyses and sensitivity analyses were also performed to examine the risks for different seasons, regions and age groups and for the robustness of our main findings.

RESULTS

Significant and similar associations were found for O3-1 h max (RR,1.012; 95%CI, 1.005-1.019) and O3-8 h max (RR, 1.011; 95%CI, 1.007-1.014), while marginal effect was identified for O3-24 h average (RR, 1.005; 95%CI, 0.996-1.014). No significant publication bias but high heterogeneities were observed. During the warm season, ozone was significantly associated with asthma exacerbation. O3-1 h max had the highest RR of 1.014 (95%CI, 1.005-1.024), followed by O3-8 h max (RR, 1.012; 95%CI, 1.009-1.016), while marginal association was identified for O3-24 h avg (RR, 1.008; 95%CI, 0.998-1.017). During the cold season, null associations were identified for all the three averaging times. Variations were also observed in region and age.

CONCLUSION

Ozone exposure measured as 1-hour or 8-hour daily max were more consistently associated with asthma exacerbations than 24-hour average exposure during the warm season.

Ozone Pollution: A Major Health Hazard Worldwide

Oxides of nitrogen (NO_x) and volatile organic compounds (VOCs) released into the atmosphere can react in the presence of solar irradiation, leading to ozone formation in the troposphere. Historically, before clean air regulations were implemented to control NO_x and VOCs, ozone concentrations were high enough to exert acute effects such as eye and nose irritation, respiratory disease emergencies, and lung function impairment. At or above current regulatory standards, day-to-day variations in ozone concentrations have been positively associated with asthma incidence and daily non-accidental mortality rate. Emerging evidence has shown that both short-term and long-term exposures to ozone, at concentrations below the current regulatory standards, were associated with increased mortality due to respiratory and cardiovascular diseases. The pathophysiology to support the epidemiologic associations between mortality and morbidity and ozone centers at the chemical and toxicological property of ozone as a strong oxidant, being able to induce oxidative damages to cells and the lining fluids of the airways, and immune-inflammatory responses within and beyond the lung. These new findings add substantially to the existing challenges in controlling ozone pollution. For example, in the United States in 2016, 90% of non-compliance to the national ambient air quality standards was due to ozone whereas only 10% was due to particulate matter and other regulated pollutants. Climate change, through creating atmospheric conditions favoring ozone formation, has been and will continue to increase ozone concentrations in many parts of world. Worldwide, ozone is responsible for several hundreds of thousands of premature deaths and tens of millions of asthma-related emergency room visits annually. To combat ozone pollution globally, more aggressive reductions in fossil fuel consumption are needed to cut NO_x and VOCs as well as greenhouse gas emissions. Meanwhile, preventive and therapeutic strategies are needed to alleviate the detrimental effects of ozone especially in more susceptible individuals. Interventional trials in humans are needed to evaluate the efficacy of antioxidants and ozone-scavenging compounds that have shown promising results in animal studies.

Economic losses due to ozone impacts on human health, forest productivity and crop yield across China

China's economic growth has significantly increased emissions of tropospheric ozone (O₃) precursors, resulting in increased regional O₃ pollution. We analyzed data from >1400 monitoring stations and estimated the exposure of population and vegetation (crops and forests) to O₃ pollution across China in 2015. Based on WHO metrics for human health protection, the current O₃ level leads to +0.9% premature mortality (59,844 additional cases a year) with 96% of populated areas showing O₃-induced premature death. For vegetation, O₃ reduces annual forest tree biomass growth by 11-13% and yield of rice and wheat by 8% and 6%, respectively, relative to conditions below the respective AOT40 critical levels (CL). These CLs are exceeded over 98%, 75% and 83% of the areas of forests, rice and wheat, respectively. Using O₃ exposure-response functions, we evaluated the costs of O₃-induced losses in rice (7.5 billion US$), wheat (11.1 billion US$) and forest production (52.2 billion US$) and SOMO35-based morbidity for respiratory diseases (690.9 billion US$) and non-accidental mortality (7.5 billion US$), i.e. a total O₃-related cost representing 7% of the China Gross Domestic Product in 2015.

Estimating the acute effects of ambient ozone pollution on the premature rupture of membranes in Xinxiang, China

While increasing evidence suggests that ozone (O₃) exposure is associated with adverse birth outcomes, only one study has focused on its impact on the premature rupture of membranes (PROM). Therefore, we thus examined the effect of O₃ on PROM in Xinxiang, China, using an over-dispersed Poisson generalized additive model. Several confounding factors, including meteorological factors, temporal trends, the day of the week, and public holidays, were considered in the model. We identified a total of 3255 instances of PROM from January 1, 2015 to December 31, 2017, and there was a significant association between the daily maximum 8-h mean concentrations (O_3-8h) and PROM. Each 10 μg/m³ increase in the 3-day average concentration (lag02) of O_3-8h corresponded to an increment in PROM of 5.42% (95% CI: 1.45-9.39%). Although the results of the stratified analyses were insignificant, a few trending results were observed: stronger associations between O₃ and PROM would occur in women with advanced age (≥35) or during the warm season than those in younger women (<35) or during the cool season. Our study indicates that O₃ exposure is an important risk factor of PROM and should be considered in its prevention and control in the study area.

Health benefit of air quality improvement in Guangzhou, China: Results from a long time-series analysis (2006-2016)

Numerous epidemiologic studies on adverse health effects of air pollution have been well documented; however, assessment on health benefits of air quality improvement from air pollution control measures has been limited in developing countries. We assessed the mortality benefits associated with air pollution improvement over 11 years in Guangzhou, China (2006-2016). A time series analysis with Generalized additive Poisson models was used to estimate mortality effects of ozone (O₃) and nitrogen dioxide (NO₂), adjusting for time trend, day of week, public holiday, temperature and relative humidity. We further estimated the changes in mortality burden of O₃ and NO₂, including attributable fraction (AF, in %) and attributable mortality (AM, in number of death) during study period. We lastly estimated mortality effects during the 2010 Asian Games (November 12 to December 18, 2010) compared to a baseline period consisting of 4-week before and 4-week after the game. During the study period, average annual concentrations of NO₂ decreased from 42.3 μg/m³ in 2006 to 33.8 μg/m³ in 2016; while O₃ levels remained stable over time. We observed significant increases in mortality of O₃ and NO₂, with approximately linear exposure-response relationships. In specific, each increase of 10 μg/m³ in O₃ and NO₂ at 2 prior days was associated with increases of 0.60% (95% confidence interval (CI): 0.47, 0.74) and 1.89% (95%CI: 1.49, 2.29) in total mortality, respectively. We further estimated that AF on total mortality attributed to NO₂ decreased from 1.38% (95%CI: 1.09, 1.68) in 2006-2010 to 0.43% (95%CI: 0.34, 0.52) in 2011-2016, corresponding to AM on total mortality of 2496 deaths (95%CI: 1964, 3033) to 1073 deaths (95%CI: 846, 1301). During the 2010 Asian Games, we observed decrease in total mortality of 9.3% (95%CI: -15.0, -3.2) in comparison with that observed in the baseline period. Similar mortality benefits in cardiovascular diseases were also observed. Our results showed reduced mortality burden from air pollution improvement in Guangzhou in recent years, which provide strong rationale for continuing to reduce air pollution through comprehensive and rigorous air quality management in the area.

Ozone pollution in Chinese cities: Assessment of seasonal variation, health effects and economic burden

The ground-level ozone (O₃) concentration in the urban regions of China has become an increasingly noticeable environmental problem in recent years. Many epidemiological studies have reported the association between O₃ pollution and mortality, only a few studies have focused on the O₃-related mortality and corresponding economic effects at the Chinese city and province level. This study reports the seasonal variation of ground-level O₃ in 338 cities of China during the year 2016 and evaluates its effect on premature mortality and economic loss. It further illustrates the differences in cause-specific mortality outcomes of the log-linear and linear model, two of the prominently used methods for estimating health effects. In 2016, the annual average daily maximum 8-h O₃ concentration in China ranged between 74 and 201 μg/m³ (138 ± 24.7 μg/m³). 30% of the total population was exposed to >160 μg/m³ O₃ concentration (Chinese national ambient air quality standard) and about 67.2% urban population lived in exposure above the WHO recommended O₃ concentrations (100 μg/m³). The estimated national O₃-attributable mortality was 74.2 × 10³ (95% CI: 16.7×10³-127×10³) in the log-linear model, whereas, the total O₃-related mortality using the linear model was 69.6 × 10³ (95% CI: 16.2 × 10³-115 × 10³). The exposure to O₃ caused a nationwide economic loss of about 7.6 billion US$ (range: 1.7-12.9) in 2016. This study uniquely provides most comprehensive coverage of the Chinese cities for O₃ associated mortality utilizing ground level measurement data for 2016 and presents a measurable assessment to the policymakers of China for streamlining their efforts on air quality improvement and O₃ containment.