Short-Term Exposure to Ambient Air Pollution and Asthma Mortality

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.

The Impact of Air Pollutants and Meteorological Factors on Chronic Obstructive Pulmonary Disease Exacerbations: A Nationwide Study

RATIONALE Chronic obstructive lung disease (COPD) is a chronic progressive disease. Although smoking is the most important risk factor, 30% of COPD patients are never smokers, and environmental agents are also influential. The effects of air pollutants and meteorological factors on COPD exacerbations have not been studied extensively. OBJECTIVE We aimed to investigate the air pollutants and meteorological factors that impact the incidence of COPD exacerbations. METHODS We obtained clinical data of COPD exacerbation cases from The National Health Insurance Service (NHIS) and merged it with 24-hour average values of air pollutants and meteorological factors from national databases. Patients who reside in eight metropolitan cities, where observatory stations are densely located, were selected for analysis. RESULTS In 1,404,505 COPD patients between 2013 and 2018, 15,282 COPD exacerbations leading to hospitalization or emergency room visits were identified. Among the various air pollutants and meteorological factors, particulate matter (PM)2.5, PM10, NO2, SO2, CO, O3, average temperature and diurnal temperature range (DTR) were associated with COPD exacerbations. GAM model analysis with cubic splines showed an inverted U-shaped relationship with PM2.5, PM10, CO, NO2, SO2, O3, DTR and humidity, while it displayed a U-shaped pattern with the average temperature. Distinct patterns were found from 2015-2016 to 2017-2018. CONCLUSIONS PM2.5, PM10, CO, NO2, O3, SO2, average temperature, humidity, and DTR affected the incidence of COPD exacerbations in various patterns, up to 10 lag days.

Diesel exposure increases susceptibility of primary human nasal epithelial cells to rhinovirus infection

Nasal epithelial cells (NECs) are among the first cells to be exposed to air pollutants and respiratory viruses. Although it is known that air pollution exposure and rhinovirus infections increase the risk for asthma development independently, it is unclear how these risk factors interact on a cellular level. Therefore, we aimed to investigate how exposure to diesel particulate matter (DPM) modifies the response of primary NECs to rhinovirus (RV) infection in vitro. Exposure of re-differentiated, primary NECs (49 healthy children [0-7 years], 12 adults) to DPM modified the mRNA expression of viral cell-surface receptors, pattern recognition receptors, and pro-inflammatory response (also protein levels). After exposure to DPM, we additionally infected the NECs with RV-1b and RV-16. Viral loads (assessed by titration assays) were significantly higher in DPM-exposed compared with non-exposed NECs. Exposure to DPM prior to RV infection resulted in a significant upregulation of pro-inflammatory cytokines (mRNA and protein level) and β-defensins mRNA, and significant downregulation of pattern recognition receptors mRNA and CXCL10 (mRNA and protein levels). There was no difference between all outcomes of NECs from children and adults. We can conclude that exposure to DPM prior to RV infection increases viral loads by downregulation of viral defense receptors and upregulation of pro-inflammatory cytokines. Our findings indicate a strong interaction between air pollution and the antiviral response to RV infection in NECs. We provide mechanistic evidence that exposure to air pollution increases susceptibility to RV infection.

Oxidant-induced epithelial alarmin pathway mediates lung inflammation and functional decline following ultrafine carbon and ozone inhalation co-exposure

Environmental inhalation exposures are inherently mixed (gases and particles), yet regulations are still based on single toxicant exposures. While the impacts of individual components of environmental pollution have received substantial attention, the impact of inhalation co-exposures is poorly understood. Here, we mechanistically investigated pulmonary inflammation and lung function decline after inhalation co-exposure and individual exposures to ozone (O₃) and ultrafine carbon black (CB). Environmentally/occupationally relevant lung deposition levels in mice were achieved after inhalation of stable aerosols with similar aerodynamic and mass median distributions. X-ray photoemission spectroscopy detected increased surface oxygen contents on particles in co-exposure aerosols. Compared with individual exposures, co-exposure aerosols produced greater acellular and cellular oxidants detected by electron paramagnetic resonance (EPR) spectroscopy, and in vivo immune-spin trapping (IST), as well as synergistically increased lavage neutrophils, lavage proteins and inflammation related gene/protein expression. Co-exposure induced a significantly greater respiratory function decline compared to individual exposure. A synthetic catalase-superoxide dismutase mimetic (EUK-134) significantly blunted lung inflammation and respiratory function decline confirming the role of oxidant imbalance. We identified a significant induction of epithelial alarmin (thymic stromal lymphopoietin-TSLP)-dependent interleukin-13 pathway after co-exposure, associated with increased mucin and interferon gene expression. We provided evidence of interactive outcomes after air pollution constituent co-exposure and identified a key mechanistic pathway that can potentially explain epidemiological observation of lung function decline after an acute peak of air pollution. Developing and studying the co-exposure scenario in a standardized and controlled fashion will enable a better mechanistic understanding of how environmental exposures result in adverse outcomes.

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Interaction with O₃ mediates free radical production on the surface of carbon black (CB) particles.

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Oxidants mediate co-exposure (CB + O₃)-induced lung function decline.

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EUK-134 (a synthetic superoxide-catalase mimetic) abrogates CB + O₃-induced lung inflammation.

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CB + O₃ co-exposure induces greater lung inflammation than individual exposures.

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Epithelial alarmin (TSLP) contributes significantly to the CB + O₃ toxicity.

Short-Term Exposure to Ambient Air Pollution and Mortality From Myocardial Infarction

BACKGROUND

Short-term exposure to ambient air pollution has been linked to occurrence of myocardial infarction (MI); however, only a limited number of studies investigated its association with death from MI, and the results remain inconsistent.

OBJECTIVES

This study sought to investigate the association of short-term exposure to air pollution across a wide range of concentrations with MI mortality.

METHODS

A time-stratified case-crossover study was conducted to investigate 151,608 MI death cases in Hubei province (China) from 2013 to 2018. Based on each case's home address, exposure to particulate matter with an aerodynamic diameter ≤2.5 μm (PM_2.5), particulate matter with an aerodynamic diameter ≤10 μm (PM₁₀), sulfur dioxide, nitrogen dioxide (NO₂), carbon monoxide, and ozone on each of the case and control days was assessed as the inverse distance-weighted average concentration at neighboring air quality monitoring stations. Conditional logistic regression models were implemented to quantify exposure-response associations.

RESULTS

Exposure to PM_2.5, PM₁₀, and NO₂ (mean exposure on the same day of death and 1 day prior) was significantly associated with increased odds of MI mortality. The odds associated with PM_2.5 and PM₁₀ exposures increased steeply before a breakpoint (PM_2.5, 33.3 μg/m³; PM₁₀, 57.3 μg/m³) and flattened out at higher exposure levels, while the association for NO₂ exposure was almost linear. Each 10-μg/m³ increase in exposure to PM_2.5 (<33.3 μg/m³), PM₁₀ (<57.3 μg/m³), and NO₂ was significantly associated with a 4.14% (95% confidence interval [CI]: 1.25% to 7.12%), 2.67% (95% CI: 0.80% to 4.57%), and 1.46% (95% CI: 0.76% to 2.17%) increase in odds of MI mortality, respectively. The association between NO₂ exposure and MI mortality was significantly stronger in older adults.

CONCLUSIONS

Short-term exposure to PM_2.5, PM₁₀, and NO₂ was associated with increased risk of MI mortality.

Allergic and non-allergic asthma phenotypes and exposure to air pollution

OBJECTIVE

Although harmful effects of air pollution on airway diseases are well-established, its effect on allergy still remains unclear. The aim of this study was to examine changes on asthma clinic and oxidant homeostasis due to air pollution between allergic asthma (AA) and non-allergic asthma (NA) phenotypes.

METHODS

This prospective, case-control study included patients with well-controlled asthma under regular treatment (n = 57) and healthy individuals (n = 51). Of asthma patients, 22 had AA and 35 had NA phenotypes. Respiratory symptoms, pulmonary function tests, serum total antioxidant status (TAS) and total oxidant status (TOS), and thiol/disulfide levels were compared between the most (V₁) and least (V₂) air-polluted times.

RESULTS

High air pollution exposure resulted to an increase in the frequency of respiratory symptoms and serum inflammation markers in both asthmatic and healthy individuals. Frequency of dyspnea and cough in AA and rhinitis in NA decreased from V₁ to V₂. Hospitalization due to asthma exacerbation, systemic corticosteroid use, and eosinophil counts were more frequent in NA group than AA in V1. An increase of blood eosinophil counts was observed in AA group at the same visit. Mean TAS and TOS levels were higher in asthma group than control group, and the decline in TAS and TOS levels from V₁ to V₂ was seen only in NA. All thiols decreased and SH/total SH ratios significantly increased from V₁ to V₂ in all groups.

CONCLUSION

This study demonstrates that air pollution affects both asthma patients and healthy individuals. Through oxidant-antioxidant and thiol pathways, however, it adversely affects respiratory system of asthma patients, at a greater extent, than healthy individuals.

Air Pollution and the Airways: Lessons from a Century of Human Urbanization

Since the industrial revolution, air pollution has become a major problem causing several health problems involving the airways as well as the cardiovascular, reproductive, or neurological system. According to the WHO, about 3.6 million deaths every year are related to inhalation of polluted air, specifically due to pulmonary diseases. Polluted air first encounters the airways, which are a major human defense mechanism to reduce the risk of this aggressor. Air pollution consists of a mixture of potentially harmful compounds such as particulate matter, ozone, carbon monoxide, volatile organic compounds, and heavy metals, each having its own effects on the human body. In the last decades, a lot of research investigating the underlying risks and effects of air pollution and/or its specific compounds on the airways, has been performed, involving both in vivo and in vitro experiments. The goal of this review is to give an overview of the recent data on the effects of air pollution on healthy and diseased airways or models of airway disease, such as asthma or chronic obstructive pulmonary disease. Therefore, we focused on studies involving pollution and airway symptoms and/or damage both in mice and humans.

Acute effects of particulate matter with different sizes on respiratory mortality in Shenzhen, China

There are relatively few studies that focus on the health effects of exposure to size-specific particles on respiratory mortality in China. We aimed to examine the association between different particle sizes and mortality from cause-specific respiratory diseases. We used a time series model with a quasi-Poisson link to investigate the relationship between different particle sizes and mortality from respiratory diseases, chronic obstructive pulmonary diseases (COPD), pneumonia, and asthma in Shenzhen during 2014-2017. A total of 3716 mortalities due to respiratory diseases were collected. Both PM₁ and PM_2.5 were associated with mortality of overall respiratory diseases, COPD, and pneumonia. An interquartile range (IQR) increase in PM₁ at lag03 was associated with a 12.21% (95% CI: 2.59%, 22.75%) increase in respiratory mortality, and each IQR increase in PM_2.5 at lag03 corresponded to a 12.09% (95% CI: 2.52%, 22.56%) increase in respiratory mortality. PM_1-2.5 was not associated with mortality from all-cause or cause-specific respiratory diseases. This study suggests that both PM₁ and PM_2.5 may increase the risk of mortality due to respiratory diseases in Shenzhen, China.

Ambient PM2.5 exposure and hospital cost and length of hospital stay for respiratory diseases in 11 cities in Shanxi Province, China

BACKGROUND

Few studies have examined the effects of ambient particulate matter with an aerodynamic diameter less than or equal to 2.5 μm (PM2.5) on hospital cost and length of hospital stay for respiratory diseases in China.

METHODS

We estimated ambient air pollution exposure for respiratory cases through inverse distance-weighted averages of air monitoring stations based on their residential address and averaged at the city level. We used generalised additive models to quantify city-specific associations in 11 cities in Shanxi and a meta-analysis to estimate the overall effects. We further estimated respiratory burden attributable to PM2.5 using the standards of WHO (25 µg/m3) and China (75 µg/m3) as reference.

RESULTS

Each 10 µg/m3 increase in lag03 PM2.5 corresponded to 0.53% (95% CI: 0.33% to 0.73%) increase in respiratory hospitalisation, an increment of 3.75 thousand RMB (95% CI: 1.84 to 5.670) in hospital cost and 4.13 days (95% CI: 2.51 to 5.75) in length of hospital stay. About 9.7 thousand respiratory hospitalisations, 132 million RMB in hospital cost and 145 thousand days of hospital stay could be attributable to PM2.5 exposures using WHO's guideline as reference. We estimated that 193 RMB (95% CI: 95 to 292) in hospital cost and 0.21 days (95% CI: 0.13 to 0.30) in hospital stay could be potentially avoidable for an average respiratory case.

CONCLUSION

Significant respiratory burden could be attributable to PM2.5 exposures in Shanxi Province, China. The results need to be factored into impact assessment of air pollution policies to provide a more complete indication of the burden addressed by the policies.

Long-term exposure to moderate fine particulate matter concentrations and cause-specific mortality in an ageing society

BACKGROUND

Long-term exposure to particulate matter <2.5 μm in size (PM2.5) is considered a risk factor for premature death. However, only a few studies have been conducted in areas with moderate PM2.5 concentrations. Moreover, an ageing society may be more susceptible to environmental exposure and future burden of mortality due to PM2.5.

METHODS

This study estimates hazard ratios (HRs) for all-cause and cause-specific mortality from long-term exposure to moderate PM2.5 concentrations in the elderly populations of seven cities in South Korea. We also projected nationwide elderly mortality caused by long-term exposure to PM2.5, accounting for population ageing until 2045. Mortality in 1 720 230 elderly adults aged ≥65 years in 2008 was monitored across 2009-16 and linked to modelled PM2.5 concentrations.

RESULTS

A total of 421 100 deaths occurred in 2009-16, and the mean of annual PM2.5 concentration ranged between 21.1 and 31.9 μg/m3 in most regions. The overall HR for a 10 μg/m3 increase in a 36-month PM2.5 moving average was 1.024 (95% confidence intervals: 1.009, 1.039). We estimated that 11 833 all-cause nationwide elderly deaths were attributable to PM2.5 exposure. Annual death tolls may increase to 17 948 by 2045. However, if PM2.5 is reduced to 5 μg/m3 by 2045, the tolls may show a lower increase to 3646.

CONCLUSIONS

Long-term exposure to moderately high levels of PM2.5 was associated with increased mortality risk among the elderly. Thus, PM2.5 reduction in response to the projected ageing-associated mortality in South Korea is critical.

Exacerbation-Prone Asthma: A Biological Phenotype or a Social Construct

Asthma is a complex syndrome with multiple phenotypes and endotypes. Asthma exacerbations are not only the clearest indictor of the morbidity of asthma and of the risk for mortality due to asthma, but also comprise a significant amount of the cost to care for poorly controlled asthma. There continues to be significant disparity in the prevalence, mortality, and morbidity due to asthma. Patients with asthma who suffer recurrent exacerbations are considered to have exacerbation-prone asthma (EPA). Efforts to characterize patients with frequent exacerbations show that the etiology is likely multifactorial. Research to determine the intrinsic risk factors for EPA include studies of both genetic and inflammatory biomarkers. External factors contributing to exacerbations have been extensively reviewed and include viral infection, environmental exposures, air pollution, and psychosocial and economic barriers to optimizing health. It is likely that EPA occurs when patients who have an increased underlying intrinsic/biological risk are placed in a given exposome (environments with a variety of exposures and triggers including allergens, pollution, stress, barriers, and occupational exposures). It is the social construct combined with underlying biology that frequently drives an EPA phenotype.

Sex and Gender Differences in Lung Disease

Sex differences in the anatomy and physiology of the respiratory system have been widely reported. These intrinsic sex differences have also been shown to modulate the pathophysiology, incidence, morbidity, and mortality of several lung diseases across the life span. In this chapter, we describe the epidemiology of sex differences in respiratory diseases including neonatal lung disease (respiratory distress syndrome, bronchopulmonary dysplasia) and pediatric and adult disease (including asthma, cystic fibrosis, idiopathic pulmonary fibrosis, chronic obstructive pulmonary disease, lung cancer, lymphangioleiomyomatosis, obstructive sleep apnea, pulmonary arterial hypertension, and respiratory viral infections such as respiratory syncytial virus, influenza, and SARS-CoV-2). We also discuss the current state of research on the mechanisms underlying the observed sex differences in lung disease susceptibility and severity and the importance of considering both sex and gender variables in research studies' design and analysis.

All-Cause Mortality Risk and Attributable Deaths Associated with Long-Term Exposure to Ambient PM2.5 in Chinese Adults

Several recent studies in China have associated raised mortality risks with chronic exposure to ambient PM_2.5. However, cohort evidence covering general populations and more homogeneous regions is extensively scarce. We conceived a nationwide perspective cohort study from 2010 through 2018, by enrolling 30 946 adult men and women aged 16-110 years from 25 provincial regions in mainland China. Cox proportional hazards models with time-varying exposures were adopted to quantify longitudinal association of PM_2.5 exposure with all-cause mortality. A total of 1762 death events occurred during a median follow-up of 8.1 years. Participants were exposed to a broad range of annual mean PM_2.5 concentrations (2.4-112 μg/m³), with an average estimate of 47.5 μg/m³. A 10-μg/m³ increase in annual average of PM_2.5 exposure was associated with an hazard ratio of 1.055 (95% confidence interval: 1.022-1.088, p < 0.001) for all-cause mortality. We estimated totally 2.68 million deaths attributable to ambient PM_2.5 in 2015, yielding a remarkable reduction of 36.7 thousand compared to the estimate in 2010 (2.72 million deaths). This study added nationally representative evidence regarding concentration-response function for long-term PM_2.5-mortality association in Chinese adults, which may significantly contribute to national and global assessments of PM_2.5-attributable death burden.

Impact of a pollution breach at a coke oven factory on asthma control in nearby vulnerable adults

BACKGROUND

Previous studies have related sulfur dioxide (SO₂) exposure to asthma exacerbations. We utilized the University of Pittsburgh Asthma Institute registry to study associations of asthma exacerbations between 2 geographically distinct populations of adults with asthma.

OBJECTIVE

Our objective was to examine whether asthma symptoms worsened following a significant fire event that destroyed pollution control equipment at the largest coke works in the United States.

METHODS

Two groups of patients with asthma, namely, those residing within 10 miles of the coke works fire (the proximal group [n = 39]) and those residing beyond that range (the control group [n = 44]), were geocoded by residential address. Concentrations of ambient air SO₂ were generated by using local University of Pittsburgh Asthma Institute registry air monitoring data. Factory emissions were also evaluated. Data from a patient historical acute exposure survey and in-person follow-up data were evaluated. Inferential statistics were used to compare the groups.

RESULTS

In the immediate postfire period (6-8 weeks), the level of emissions of SO₂ from the factory emissions increased to 25 times more than the typical level. Following the pollution control breach, the proximal cohort self-reported an increase in medication use (risk ratio = 1.76; 95% CI = 1.1-2.8; P < .01) and more exacerbations. In a small subset of the follow-up cohort of those who completed the acute exposure survey only, asthma control metrics improved.

CONCLUSIONS

Real-world exposure to a marked increase in ambient levels of SO₂ from a pollution control breach was associated with worsened asthma control in patients proximal to the event, with the worsened control improving following repair of the controls. Improved spatial resolution of air pollutant measurements would enable better examination of exposures and subsequent health impacts.

Early-life exposure to submicron particulate air pollution in relation to asthma development in Chinese preschool children

BACKGROUND

Emerging research suggested an association of early-life particulate air pollution exposure with development of asthma in childhood. However, the potentially differential effects of submicron particulate matter (PM; PM with aerodynamic diameter ≤1 μm [PM₁]) remain largely unknown.

OBJECTIVE

This study primarily aimed to investigate associations of childhood asthma and wheezing with in utero and first-year exposures to size-specific particles.

METHODS

We conducted a large cross-sectional survey among 5788 preschool children aged 3 to 5 years in central China. In utero and first-year exposures to ambient PM₁, PM with aerodynamic diameter less than or equal to 2.5 μm, and PM with aerodynamic diameter less than or equal to 10 μm at 1 × 1-km resolution were assessed using machine learning-based spatiotemporal models. A time-to-event analysis was performed to examine associations between residential PM exposures and childhood onset of asthma and wheezing.

RESULTS

Early-life size-specific PM exposures, particularly during pregnancy, were significantly associated with increased risk of asthma, whereas no evident PM-wheezing associations were observed. Each 10-μg/m³ increase in in utero and first-year PM₁ exposure was accordingly associated with an asthma's hazard ratio in childhood of 1.618 (95% CI, 1.159-2.258; P = .005) and 1.543 (0.822-2.896; P = .177). Subgroup analyses suggest that short breast-feeding duration may aggravate PM-associated risk of childhood asthma. Each 10-μg/m³ increase in in utero exposure to PM₁, for instance, was associated with a hazard ratio of 2.260 (1.393-3.666) among children with 0 to 5 months' breast-feeding and 1.156 (0.721-1.853) among those longer breast-fed.

CONCLUSIONS

Our study added comparative evidence for increased risk of childhood asthma in relation to early-life PM exposures, highlighting stronger associations with ambient PM₁ than with PM with aerodynamic diameter less than or equal to 2.5 μm and PM with aerodynamic diameter less than or equal to 10 μm.

Pollutant-sex specific differences in respiratory hospitalization and mortality risk attributable to short-term exposure to ambient air pollution

BACKGROUND

Many studies have reported associations of individual pollutants with respiratory hospitalization and mortality based on different populations, which makes it difficult to directly compare adverse health effects among multiple air pollutants.

OBJECTIVES

The study goal is to compare acute respiratory-related hospitalization and mortality associated with short-term exposure to three ambient air pollutants and analyze differences in health risks by season, age and sex.

METHODS

Hourly measurements of air pollutants (ozone, NO₂, PM_2.5) and temperature were collected from ground-monitors for 24 cities along with daily hospitalization (1996-2012) and mortality (1984-2012) data. National associations between air pollutant and health outcome were estimated for season (warm, cold vs. year-round), age (base ≥ 1, seniors > 65), and sex (females ≥ 1 and males ≥ 1) using Bayesian hierarchical models.

RESULTS

Overall, the three air pollutants were significantly associated with acute respiratory health outcomes at different lag-days. For respiratory hospitalization, the increased risks in percent changes with 95% posterior intervals for a 10-unit increase in each pollutant were: ozone (lag1, 0.7% (0.4, 0.9)), NO₂ (lag0, 0.7% (0.1, 1.4)), and PM_2.5 (lag1, 1.3% (0.7, 1.9)). For respiratory mortality: ozone (lag2, 1.2% (0.4, 1.9)), NO₂ (lag1, 2.1% (0.6, 3.5)), and PM_2.5 (lag1, 0.6% (-1.0, 2.2)). While some differences in risk were observed by season and age group, sex-specific differences were more pronounced. Compared with males, females had a higher respiratory mortality risk (1.8% (0.6, 2.9) vs 0.5% (-0.3, 1.3)) from ozone, a higher respiratory hospitalization risk (0.9% (0.0, 1.8) vs 0.6% (-0.3, 1.4)) but lower mortality risk (1.4% (-1.0, 3.7) vs 2.2% (0.4, 4.0)) from NO₂, and a lower hospitalization risk (0.7% (-0.2, 1.7) vs 1.8% (1.0, 2.6)) from PM_2.5.

CONCLUSION

This study reports significant health effects of short-term exposure to three ambient air pollutants on respiratory hospitalization (ozone≈NO₂ < PM_2.5 per-10 unit; ozone>NO₂ ≈ PM_2.5 per-IQR) and mortality (ozone≈NO₂ > PM_2.5) in Canada. Pollutant-sex-specific differences were found, but inconclusive due to limited biological and physiological explanations. Further studies are warranted to understand the pollutant-sex specific differences.

Associations between PM1 exposure and daily emergency department visits in 19 hospitals, Beijing

Although the adverse health effects caused by PM_2.5 (particulate matter (PM) with an aerodynamic diameter <2.5 μm) and PM₁₀ (PM with an aerodynamic diameter <10 μm) have been examined in numeric studies, far less scientific evidence is available for PM with an aerodynamic diameter <1 μm (PM₁). We performed a time series analysis to elucidate the associations between PM₁ exposure and emergency department visits (EDVs) in 19 hospitals within Beijing. During the study period from January 2016 to December 2017, the average PM₁ (mean ± standard deviation) was determined to be 39 ± 39 μg/m³, which was approximately 36% lower than that of 61 ± 56 μg/m³ for PM_2.5. Results based on meta-analysis suggest that non-accidental and respiratory EDVs increased by 0.47% (95% confidence interval, CI: 0.35, 0.59%) and 0.59% (95%CI: 0.38, 0.8%) per 10 μg/m³ uptick in PM₁ exposure. By comparison, the magnitude downgraded to 0.27% (95%CI: 0.15, 0.39%) in non-accidental and 0.32% (95%CI: 0.18, 0.47%) in respiratory EDVs for PM_2.5 exposure, indicating that PMs of a smaller size may be a higher risk factor for EDVs. No significant differences in PM-associated EDV effects were noted between males and females, while stratified analysis by age and season illustrated that stronger effects were found for a warm season and young population. Our analysis reinforces the notion that PM₁ exhibited a higher risk for EDVs, suggesting more efforts may be required to mitigate PM₁ pollution.

Environmental air pollution: respiratory effects

Environmental air pollution is a major risk factor for morbidity and mortality worldwide. Environmental air pollution has a direct impact on human health, being responsible for an increase in the incidence of and number of deaths due to cardiopulmonary, neoplastic, and metabolic diseases; it also contributes to global warming and the consequent climate change associated with extreme events and environmental imbalances. In this review, we present articles that show the impact that exposure to different sources and types of air pollutants has on the respiratory system; we present the acute effects-such as increases in symptoms and in the number of emergency room visits, hospitalizations, and deaths-and the chronic effects-such as increases in the incidence of asthma, COPD, and lung cancer, as well as a rapid decline in lung function. The effects of air pollution in more susceptible populations and the effects associated with physical exercise in polluted environments are also presented and discussed. Finally, we present the major studies on the subject conducted in Brazil. Health care and disease prevention services should be aware of this important risk factor in order to counsel more susceptible individuals about protective measures that can facilitate their treatment, as well as promoting the adoption of environmental measures that contribute to the reduction of such emissions.

The Impact of Air Pollution on Outpatient Visits of Children with Asthma in Xi'an, China

INTRODUCTION

The number of children with asthma has increased significantly in China. In recent years, there has been a steady increase in outpatient visits of children with asthma, attributed to poor air quality and environmental pollution reported regionally and at our institution. This study aimed to assess the association between air pollution and the number of outpatient visits of children with asthma in Xi'an, the largest city in northwest China.

METHODS

We searched the database of the largest children's hospital in Xi'an for related information from 2014 to 2018 and then acquired data on air pollution, including the daily average concentrations of fine particles (PM_2.5), inhalable particles (PM₁₀), nitrogen dioxide (NO₂), and sulfur dioxide (SO₂) of that same time period. Time-series generalized additive models were used to analyze the relationships.

RESULTS

Our results revealed that air pollution was very serious in Xi'an, with elevated average concentrations of PM_2.5, PM₁₀, and NO₂ from 2015 to 2018. The relative risk of outpatient visits due to asthma associated with PM_2.5, PM₁₀, and SO₂ pollution rose significantly and reached 1.11 (1.02-1.21), 1.25 (1.01-1.55), and 1.71 (1.31-2.25), respectively, when there was a 10 ug·m^-3 increase in concentration, during a lag of 21 d.

CONCLUSIONS

A high concentration of particulate matter (PM_2.5 and PM₁₀) was the prominent feature of air pollution in Xi'an. Exposure to air pollutant (PM_2.5, PM₁₀, SO₂) was positively associated with an increased risk of children's outpatient visits for asthma in Xi'an.

Asthma and air pollution: recent insights in pathogenesis and clinical implications

PURPOSE OF REVIEW

Air pollution has adverse effects on the onset and morbidity of respiratory diseases, including asthma. In this review, we discuss recent insights into the effects of air pollution on the incidence and exacerbation of asthma. We focus on epidemiological studies that describe the association between air pollution exposure and development, mortality, persistence and exacerbations of asthma among different age groups. Moreover, we also provide an update on translational studies describing the mechanisms behind this association.

RECENT FINDINGS

Mechanisms linking air pollutants such as particulate matter, nitrogen dioxide (NO2) and ozone to the development and exacerbation of asthma include the induction of both eosinophilic and neutrophilic inflammation driven by stimulation of airway epithelium and increase of pro-inflammatory cytokine production, oxidative stress and DNA methylation changes. Although exposure during foetal development is often reported as a crucial timeframe, exposure to air pollution is detrimental in people of all ages, thus influencing asthma onset as well as increase in asthma prevalence, mortality, persistence and exacerbation.

SUMMARY

In conclusion, this review highlights the importance of reducing air pollution levels to avert the progressive increase in asthma incidence and morbidity.

Analysis of Single Nucleotide Variants (SNVs) Induced by Exposure to PM10 in Lung Epithelial Cells Using Whole Genome Sequencing

There are many epidemiological studies asserting that fine dust causes lung cancer, but the biological mechanism is not clear. This study was conducted to investigate the effect of PM₁₀ (particulate matter less than 10 μm) on single nucleotide variants through whole genome sequencing in lung epithelial cancer cell lines (HCC-827, NCI-H358) that have been exposed to PM₁₀. The two cell lines were exposed to PM₁₀ for 15 days. We performed experimental and next generation sequencing analyses on experimental group that had been exposed to PM₁₀ as well as an unexposed control group. After exposure to PM₁₀, 3005 single nucleotide variants were newly identified in the NCI-H358 group, and 4402 mutations were identified in the HCC-827 group. We analyzed these single nucleotide variants with the Mutalisk program. We observed kataegis in chromosome 1 in NCI-H358 and chromosome 7 in HCC-827. In mutational signatures analysis, the COSMIC mutational signature 5 was highest in both HCC-827 and NCI-H358 groups, and each cosine similarity was 0.964 in HCC-827 and 0.979 in the NCI-H358 group. The etiology of COSMIC mutational signature 5 is unknown at present. Well-designed studies are needed to determine whether environmental factors, such as PM₁₀, cause COSMIC mutational signature 5.

External Environmental Pollution as a Risk Factor for Asthma

Air pollution is a worrisome risk factor for global morbidity and mortality and plays a special role in many respiratory conditions. It contributes to around 8 million deaths/year, with outdoor exposure being responsible for more than 4.2 million deaths throughout the world, while more than 3.8 million die from situations related to indoor pollution. Pollutant agents induce several respiratory symptoms. In addition, there is a clear interference in numerous asthma outcomes, such as incidence, prevalence, hospital admission, visits to emergency departments, mortality, and asthma attacks, among others. The particulate matter group of pollutants includes coarse particles/PM₁₀, fine particles/PM_2.5, and ultrafine particles/PM_0.1. The gaseous components include ground-level ozone, nitrogen dioxide, sulfur dioxide, and carbon monoxide. The timing, load, and route of allergen exposure are other items affecting allergic disease phenotypes. The complex interaction between pollutant exposures and human host factors has an implication in the development and rise of asthma as a public health problem. However, there are hiatuses in the understanding of the pathways in this disease. The routes through which pollutants induce asthma are multiple, and include the epigenetic changes that occur in the respiratory tract microbiome, oxidative stress, and immune dysregulation. In addition, the expansion of the modern Westernized lifestyle, which is characterized by intense urbanization and more time spent indoors, resulted in greater exposure to polluted air. Another point to consider is the different role of the environment according to age groups. Children growing up in economically disadvantaged neighborhoods suffer more important negative health impacts. This narrative review highlights the principal polluting agents, their sources of emission, epidemiological findings, and mechanistic evidence that links environmental exposures to asthma.

Associations of short-term exposure to air pollution and emergency department visits for pediatric asthma in Shanghai, China

There is limited evidence regarding the relationship between air pollution and pediatric asthma in developing countries. This study aimed to investigate the association between short-term exposure to ambient air pollutants and pediatric asthma emergency department (ED) visits in Shanghai, China. We collected data on six criteria air pollutants (PM_2.5, PM₁₀, NO₂, SO₂, CO, and O₃) and daily ED visits for pediatric asthma patients from 66 hospitals in Shanghai from 2016 to 2018. The generalized additive model combined with polynomial distributed lag model was applied to explore the associations. We fitted two-pollutant models and stratified the analyses by sex, age, and season. In total, we identified 108,817 emergency department visits for pediatric asthma. A 10 μg/m³ increase in the concentrations of PM_2.5, NO₂, SO₂, and O₃ was significantly associated with increased risks of pediatric asthma ED visits, with relative risk of pediatric asthma of 1.011 [95% confidence interval (CI): 1.002, 1.021], 1.030 (95%CI: 1.017, 1.043), 1.106 (95%CI: 1.041, 1.174), and 1.009 (95%CI: 1.001, 1.017), respectively. The associations of NO₂ remained robust in the two-pollutant models. There were stronger associations for older children (6-18 years) and in warm seasons. The concentration-response curves for pediatric asthma and PM_2.5, NO₂, SO₂, and O₃ were steeper at lower and moderate concentrations but became flatter at higher concentrations. This analysis provided evidence that short-term exposure to air pollutants (PM_2.5, NO₂, SO₂, and O₃) could increase the risk of asthma exacerbations among children, and health benefits would be gained from improved air quality.

Evaluation of associations between asthma exacerbations and distance to roadways using geocoded electronic health records data

Background

Asthma exacerbations in children often require medications, urgent care, and hospitalization. Multiple environmental triggers have been associated with asthma exacerbations, including particulate matter 2.5 (PM2.5) and ozone, which are primarily generated by motor vehicle exhaust. There is mixed evidence as to whether proximity to highways increases risk of asthma exacerbations.

Methods

To evaluate the impact of highway proximity, we assessed the association between asthma exacerbations and the distance of child’s primary residence to two types of roadways in Durham County, North Carolina, accounting for other patient-level factors. We abstracted data from the Duke University Health System electronic health record (EHR), identifying 6208 children with asthma between 2014 and 2019. We geocoded each child’s distance to roadways (both 35 MPH+ and 55 MPH+). We classified asthma exacerbation severity into four tiers and fitted a recurrent event survival model to account for multiple exacerbations.

Results

There was a no observed effect of residential distance from 55+ MPH highway (Hazard Ratio: 0.98 (95% confidence interval: 0.94, 1.01)) and distance to 35+ MPH roadway (Hazard Ratio: 0.98 (95% confidence interval: 0.83, 1.15)) and any asthma exacerbation. Even those children living closest to highways (less 0.25 miles) had no increased risk of exacerbation. These results were consistent across different demographic strata.

Conclusions

While the results were non-significant, the characteristics of the study sample – namely farther distance to roadways and generally good ambient environmental pollution may contribute to the lack of effect. Compared to previous studies, which often relied on self-reported measures, we were able to obtain a more objective assessment of outcomes. Overall, this work highlights the opportunity to use EHR data to study environmental impacts on disease.

Supplementary Information

Supplementary information accompanies this paper at 10.1186/s12889-020-09731-0.

Genome-Wide Analysis Reveals Mucociliary Remodeling of the Nasal Airway Epithelium Induced by Urban PM2.5

Air pollution particulate matter <2.5 μm (PM_2.5) exposure is associated with poor respiratory outcomes. Mechanisms underlying PM_2.5-induced lung pathobiology are poorly understood but likely involve cellular and molecular changes to the airway epithelium. We extracted and chemically characterized the organic and water-soluble components of air pollution PM_2.5 samples, then determined the whole transcriptome response of human nasal mucociliary airway epithelial cultures to a dose series of PM_2.5 extracts. We found that PM_2.5 organic extract (OE), but not water-soluble extract, elicited a potent, dose-dependent transcriptomic response from the mucociliary epithelium. Exposure to a moderate OE dose modified the expression of 424 genes, including activation of aryl hydrocarbon receptor signaling and an IL-1 inflammatory program. We generated an OE-response gene network defined by eight functional enrichment groups, which exhibited high connectivity through CYP1A1, IL1A, and IL1B. This OE exposure also robustly activated a mucus secretory expression program (>100 genes), which included transcriptional drivers of mucus metaplasia (SPDEF and FOXA3). Exposure to a higher OE dose modified the expression of 1,240 genes and further exacerbated expression responses observed at the moderate dose, including the mucus secretory program. Moreover, the higher OE dose significantly increased the MUC5AC/MUC5B gel-forming mucin expression ratio and strongly downregulated ciliated cell expression programs, including key ciliating cell transcription factors (e.g., FOXJ1 and MCIDAS). Chronic OE stimulation induced mucus metaplasia-like remodeling characterized by increases in MUC5AC⁺ secretory cells and MUC5AC mucus secretions. This epithelial remodeling may underlie poor respiratory outcomes associated with high PM_2.5 exposure.

Immunopathological features of air pollution and its impact on inflammatory airway diseases (IAD)

Air pollution causes significant morbidity and mortality in patients with inflammatory airway diseases (IAD) such as allergic rhinitis (AR), chronic rhinosinusitis (CRS), asthma, and chronic obstructive pulmonary disease (COPD). Oxidative stress in patients with IAD can induce eosinophilic inflammation in the airways, augment atopic allergic sensitization, and increase susceptibility to infection. We reviewed emerging data depicting the involvement of oxidative stress in IAD patients. We evaluated biomarkers, outcome measures and immunopathological alterations across the airway mucosal barrier following exposure, particularly when accentuated by an infectious insult.

Embryonic gene expression altered by maternal exposure to air pollution in rats

Exposure to air pollution is known to increase the risks for cardiovascular, pulmonary and metabolic diseases. Growing evidences also indicated that air pollution exposure during pregnancy could negatively impact on early embryonic development and children's health. We performed RNA sequencing to identify deregulated mRNAs in air pollution-exposed rat embryos. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were used to analyse the potential cellular functions of deregulated mRNAs. Our analysis indicated that a total of 1678 mRNAs were differentially expressed on gestation day 9 upon in utero exposure to fine particulate matter of > 200 μg/m3, among which 1098 mRNAs were downregulated and 580 mRNAs were upregulated. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses revealed gap junction, cell adhesion, axon guidance and the neurotrophin signalling pathway as key biological processes perturbed by air pollution exposure. Furthermore, reconstruction of the mRNA regulatory network highlighted the central roles of Tbx4, Bmp4, Sox10, Wnt9b, Bmp7 and Foxc2. These data suggested that embryonic mRNA deregulation may underlie the formation of air pollution-associated congenital defects.

Sperm quality and ambient air pollution exposure: A retrospective, cohort study in a Southern province of China

BACKGROUND

Abnormal semen quality is one of the common causes of infertility. The relationship between exposure to air pollutants and semen quality is unclear.

OBJECTIVES

To evaluate the impact of ambient air pollutant exposures on semen quality.

METHODS

We analyzed 3797 semen samples from Guangdong Human Sperm Bank between May 28, 2018 and March 31, 2019. The inverse distance weighted interpolation method was used to estimate the personal exposures to CO, SO₂, NO₂, O₃, PM₁₀ and PM_2.5 during the entire period (0-90 lag days) and key periods (0-9, 10-14, 70-90 lag days) of sperm development. Linear mixed models were used to evaluate the exposure-response relationships between air pollutants and semen quality, including sperm concentration, sperm count and sperm motility, after adjusting for other covariates. The regression coefficients and 95% confidence intervals (CIs) associated with each interquartile range (IQR) increase in pollutant concentrations were estimated for each semen quality parameter.

RESULTS

Overall, we observed a significant association of decreased sperm count with the exposure to PM₁₀ (-0.2466; -0.4443, -0.0489) and PM_2.5 (-0.2910; -0.5401, -0.0419). Among the sperm quality parameters assessed, sperm count was observed more frequently to be negatively associated with ambient air pollutants (CO, NO₂, O₃, PM₁₀ and PM_2.5), especially for the period during 10-14 lag days. In addition, motility decline was significantly associated with O₃ in the late stage of sperm development. Sensitivity analyses for subgroup population yielded similar results. No significant association was found between all pollutants and sperm concentration (all P > 0.05).

CONCLUSIONS

Our results indicate that ambient air pollutants exposures during sperm development may have an adverse effect on semen quality, especially for sperm count and motility. The findings emphasize the potential to improve semen quality by reducing ambient air pollutant exposures, and the importance of taking into account the critical period of sperm development when protective measures are implemented.

Impact of Air Pollution on Asthma Outcomes

Asthma is a chronic respiratory disease characterized by variable airflow obstruction, bronchial hyperresponsiveness, and airway inflammation. Evidence suggests that air pollution has a negative impact on asthma outcomes in both adult and pediatric populations. The aim of this review is to summarize the current knowledge on the effect of various outdoor and indoor pollutants on asthma outcomes, their burden on its management, as well as to highlight the measures that could result in improved asthma outcomes. Traffic-related air pollution, nitrogen dioxide and second-hand smoking (SHS) exposures represent significant risk factors for asthma development in children. Nevertheless, a causal relation between air pollution and development of adult asthma is not clearly established. Exposure to outdoor pollutants can induce asthma symptoms, exacerbations and decreases in lung function. Active tobacco smoking is associated with poorer asthma control, while exposure to SHS increases the risk of asthma exacerbations, respiratory symptoms and healthcare utilization. Other indoor pollutants such as heating sources and molds can also negatively impact the course of asthma. Global measures, that aim to reduce exposure to air pollutants, are highly needed in order to improve the outcomes and management of adult and pediatric asthma in addition to the existing guidelines.

Screen time and sleep disorder in preschool children: identifying the safe threshold in a digital world

OBJECTIVES

Sleep disorder is a common problem in children that can jeopardize their health and well-being. With the popularity of electronic devices such as portable tablets and smartphones in the 21st century, children are spending much more time on screen, but the impact of such change on children's sleep disorder has been less investigated so far. This study aims to examine the dose-response association between time spent on different electronic devices and children's sleep disorder.

STUDY DESIGN

The design of this study is a cross-sectional study.

METHODS

We randomly selected 2278 children aged 3-6 years from 15 kindergartens in Tongling, China. The potentially non-linear association between screen-viewing time (i.e. television [TV], computer, iPad, Phone) and the risk of sleep disorder was examined using a logistic generalized additive model.

RESULTS

We observed a J-shaped association between TV viewing time and the risk of sleep disorder, with a threshold of 1 h/day. For each 1 h/day increment in TV viewing time over the threshold, the risk of sleep disorder increased by 12.35% (95% confidence interval: 1.87-23.92%). This association seemed to be greater for girls than boys and for TV viewing at weekend than on weekdays, but the difference was not statistically significant (P-value>0.05). We did not find adequate evidence of an adverse effect of more time spent on computer, iPad and Phone.

CONCLUSIONS

This study suggests a positive but non-linear relationship between time spent on watching TV and sleep disorder in Chinese preschool children. Setting the TV viewing time limit less than 1 h/day may help reduce the risk of developing sleep disorder. Further investigation is also needed to examine and compare the effects of heavy use of other electronic devices on sleep disorder.

Long-term effect of personal PM2.5 exposure on lung function: A panel study in China

Exposure to fine particulate matter (PM_2.5) have been associated with adverse respiratory outcomes, but long-term effect of personal exposure on lung function remains largely unknown. We conducted a panel study of 158 adult residents with 394 measurements of personal PM_2.5 concentration and lung function within six years to investigate the long-term association. Linear mixed models were used to identify the associations between lung function changes in relation to different levels of persistent personal PM_2.5 exposure in three or six years. We further attempted to validate resident areas (city) and smoking status as potential predictors of the long-term PM_2.5 exposure levels (persistently high/ persistently low) by generating ROC curves. Compared with subjects who had persistently low exposure level, those with persistently high levels of personal PM_2.5 exposure had an additional 3.63 % decline in FEV₁/FVC in three years (-3.63 [-7.25, -0.02]), while 7.15 % decline in six years (-7.15 [-14.27, -0.03]). BMI can modify the association. The AUCs were 0.68 (95 %CI: 0.54, 0.82), 0.75 (0.64, 0.86), and 0.82 (0.71, 0.93) for models including smoking status, resident areas, and smoking status combining resident areas respectively. These findings provide new evidence for the long-term effect of personal PM_2.5 exposure on lung function decline.

Ex vivo innate responses to particulate matter from livestock farms in asthma patients and healthy individuals

BACKGROUND

Asthma patients suffer from periodic acute worsening of symptoms (i.e. loss of asthma control or exacerbations), triggered by a variety of exogenous stimuli. With the growing awareness that air pollutants impact respiratory diseases, we investigated whether particulate matter (PM) derived from various livestock farms (BioPM) differentially affected innate and oxidative stress responses in asthma and health.

METHODS

Peripheral blood mononuclear cells (PBMCs), collected from patients sequentially before and during loss of asthma control and from healthy individuals, were exposed to BioPM collected from chicken, goat and pig farms (1 and 5 μg/ml), with or without pre-treatment with antioxidants. Cytokine release and oxidative stress were assessed.

RESULTS

PBMCs produced IFNγ, IL-1β, IL-10 and TNFα upon stimulation with BioPM, with that from pig farms inducing the highest cytokine levels. Overall, cytokine production was irrespective of the presence or state of disease. However, PBMCs from stable asthma patients upon exposure to the three BioPM showed more extreme TNFα responses than those from healthy subjects. Furthermore, PBMCs obtained during loss of asthma control that were exposed to BioPM from pig farms showed enhanced IFNγ release as well as decreased oxidative stress levels upon pre-treatment with N-acetylcysteine (NAC) compared to stable disease. NAC, but not superoxide dismutase and catalase, also counteracted BioPM-induced cytokine release, indicating the importance of intracellular reactive oxygen species in the production of cytokines.

CONCLUSIONS

BioPM triggered enhanced pro-inflammatory responses by PBMCs from both healthy subjects and asthma patients, with those from patients during loss of asthma control showing increased susceptibility to BioPM from pig farms in particular.

Particle depletion of diesel exhaust restores allergen-induced lung-protective surfactant protein D in human lungs

RATIONALE

Exposure to air pollution is linked with increased asthma morbidity and mortality. To understand pathological processes linking air pollution and allergen exposures to asthma pathophysiology, we investigated the effect of coexposure to diesel exhaust (DE) and aeroallergen on immune regulatory proteins in human airways.

METHODS

Fourteen allergen-sensitised participants completed this randomised, double-blinded, cross-over, controlled exposure study. Each participant underwent four exposures (allergen-alone exposure, DE and allergen coexposure, particle-depleted DE (PDDE) and allergen coexposure, and sham exposure) on different order-randomised dates, each separated by a 4-week washout. Serum and bronchoalveolar lavage (BAL) were assayed for pattern recognition molecules, cytokines, chemokines and inflammatory mediators.

RESULTS

In human airways, allergen-alone exposure led to accumulation of surfactant protein D (SPD; p=0.02). Coexposure to allergen and DE did not elicit the same increase of SPD as did allergen alone; diesel particulate reduction restored allergen-induced SPD accumulation. Soluble receptor for advanced glycation end products was higher with particle reduction than without it. In the systemic circulation, there was a transient increase in SPD and club cell protein 16 (CC16) 4 hours after allergen alone. CC16 was augmented by PDDE, but not DE. % eosinophils in BAL (p<0.005), eotaxin-3 (p<0.0001), interleukin 5 (IL-5; p<0.0001) and thymus and activation regulated chemokine (p=0.0001) were each increased in BAL by allergen. IL-5, SPD and % eosinophils in BAL were correlated with decreased FEV₁.

CONCLUSION

Short-term coexposure to aeroallergen and DE alters immune regulatory proteins in lungs; surfactant levels are dependent on particle depletion.

TRIAL REGISTRATION NUMBER

NCT02017431.

Short-term effect of PM1 on hospital admission for ischemic stroke: A multi-city case-crossover study in China

This study aims to examine the association between short-term exposures to PM₁, PM_2.5 and PM₁₀ (particulate matter with aerodynamic diameters ≤1 μm, ≤2.5 μm and ≤10 μm, respectively) and hospital admission for ischemic stroke in China. Daily counts of hospital admission for ischemic stroke were collected in 5 hospitals in China during November 2013 to October 2015. Daily concentrations of PM₁, PM_2.5 and PM₁₀ were collected in 5 cities where the hospitals were located. A time-stratified case-crossover design was used to examine the hospital-specific PM-ischemic stroke association after controlling for potential confounders. Then the effect estimates were pooled using a random-effect meta-analysis. A total of 68,122 hospital admissions for ischemic stroke were identified from 5 hospitals during the study period. The pooled results showed that exposures to PM₁, PM_2.5 and PM₁₀ were significantly associated with increased hospital admission for ischemic stroke on the current day and previous 1 day. The RRs (relative risk associated with per 10 μg/m³ increase in each pollutant) and 95%CIs (confidence intervals) for the cumulative effects of PM₁, PM_2.5 and PM₁₀ on ischemic stroke during lag 0-1 days were 1.014 (1.005, 1.0023), 1.007 (1.000, 1.014) and 1.005 (1.001, 1.009), respectively. In total, 3.5%, 3.6% and 4.1% of hospital admissions for ischemic stroke could be attributable to PM₁, PM_2.5 and PM₁₀, respectively. Exposures to ambient PM₁, PM_2.5 and PM₁₀ pollution showed acute adverse effects on hospital admission for ischemic stroke. The health effects of PM₁ should be considered by policy-makers.

Age- and season-specific effects of ambient particles (PM1, PM2.5, and PM10) on daily emergency department visits among two Chinese metropolitan populations

BACKGROUND

Ambient PM_2.5 has been identified as the top leading cause of risk-attributable deaths worldwide, particularly in China. Evidence suggested that PM₁ contributed the most majority of PM_2.5 concentrations in Chinese cities. However, epidemiologic knowledge to date is of wide lack regarding PM₁-associated health effects.

METHODS

We collected daily records of all-cause emergency department visits (EDVs) and ground measurements of ambient air pollutants and meteorological factors in Guangzhou and Shenzhen, China, 2015-2016. Case-crossover design and conditional logistic regression models were used to comparatively assess the short-term effects of ambient PM₁, PM_2.5, and PM₁₀ on EDVs. Stratified analyses by gender, age and season were performed to identify vulnerable groups and periods.

RESULTS

PM₁, PM_2.5 and PM₁₀ were all significantly associated with increased EDVs in both cities. Population risks for EDVs increased by 2.2% [95% confidence interval, 1.8 to 2.6] in Guangzhou and 1.7% [1.0 to 2.4] in Shenzhen, for a 10 μg/m³ rise in PM₁ at lag 0-1 days and lag 0-4 days, respectively. Relatively lower risks were found to be associated with PM_2.5 and PM₁₀. PM-EDVs associations exhibited no gender differences, but varied across age groups. Compared with adults and the elderly, children under 14 years-of-age suffered higher PM-induced risks. Results from both cities suggested greatly significant effect modification by season, with consistently stronger PM-EDVs associations during cold months.

CONCLUSIONS

Our study added comparative evidence for increased EDVs risks associated with short-term exposures to ambient PM₁, PM_2.5 and PM₁₀. Besides, PM-associated effects were significantly stronger among children and during cold months.

Ambient air pollution and markers of fetal growth: A retrospective population-based cohort study of 2.57 million term singleton births in China

BACKGROUNDS

Evidence is scarce on the relation between maternal exposure to ambient air pollution during pregnancy and fetal growth in developing countries. Moreover, the current evidence is inconsistent. We aimed to investigate the association of trimester-specific exposure to air pollution with risk of being born small for gestational age (SGA) and birth weight-markers of fetal growth-among Chinese term births.

METHODS

This retrospective population-based cohort study consisted of 2,567,457 singleton term live-births from January 1, 2014 to December 31, 2017 across 123 Chinese districts and counties. Personal exposure to ambient air pollutants including carbon monoxide (CO), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), ozone (O₃), particulate matter with aerodynamic diameter < 2.5 μm (PM_2.5), and PM₁₀ was assigned using the inverse distance weighting spatial interpolation algorithm. Generalized estimating equations (GEE) logistic regression models were performed to estimate the associations between trimester-specific exposure to air pollution and risk of SGA or low birth weight (LBW), and GEE linear regression to examine the associations between the exposure and term birth weight, adjusting for maternal demographics, maternal cigarette smoking status during pregnancy, mode of delivery, gravidity, gestational age, year and month of conception, neonate's sex, and meteorological factors. Stratified and sensitivity analyses were also performed.

RESULTS

When mother exposed to ambient air pollutants over the entire pregnancy, per IQR increment (0.122 mg/m³) in ambient CO concentrations was associated with higher risk of SGA (odds ratio (OR) = 1.04, 95% confidence interval (CI): 1.02, 1.05) and reduced birth weight among term births (-5.95 g, 95% CI: -8.01, -3.89). This association was also pronounced in the second and third trimesters. Term birth weight was negatively associated with per IQR increase of O₃ (-3.52 g, 95% CI: -6.23, -0.81), PM_2.5 (-5.93 g, 95% CI: -8.36, -3.49) and PM₁₀ (-7.78 g, 95% CI: -10.41, -5.16) during the entire pregnancy, respectively. No significant association was detected between maternal exposure to air pollutants and term LBW. Effect estimates of heterogeneity suggested that maternal age and infant sex modified the impact of air pollution on birth weight.

CONCLUSIONS

The findings suggest that maternal exposure to air pollution during pregnancy is adversely affecting fetal growth. Further studies are warranted to integrate these findings and take clinical or public health interventions in pregnancy.

Short-term effects of ambient PM1 and PM2.5 air pollution on hospital admission for respiratory diseases: Case-crossover evidence from Shenzhen, China

BACKGROUND

Ambient PM₁ (particulate matter with aerodynamic diameter ≤1 μm) is an important contribution of PM_2.5 mass. However, little is known worldwide regarding the PM₁-associated health effects due to a wide lack of ground-based PM₁ measurements from air monitoring stations.

METHODS

We collected daily records of hospital admission for respiratory diseases and station-based measurements of air pollution and weather conditions in Shenzhen, China, 2015-2016. Time-stratified case-crossover design and conditional logistic regression models were adopted to estimate hospitalization risks associated with short-term exposures to PM₁ and PM_2.5.

RESULTS

PM₁ and PM_2.5 showed significant adverse effects on respiratory disease hospitalizations, while no evident associations with PM_1-2.5 were identified. Admission risks for total respiratory diseases were 1.09 (95% confidence interval: 1.04 to 1.14) and 1.06 (1.02 to 1.10), corresponding to per 10 μg/m³ rise in exposure to PM₁ and PM_2.5 at lag 0-2 days, respectively. Both PM₁ and PM_2.5 were strongly associated with increased admission for pneumonia and chronic obstructive pulmonary diseases, but exhibited no effects on asthma and upper respiratory tract infection. Largely comparable risk estimates were observed between male and female patients. Groups aged 0-14 years and 45-74 years were significantly affected by PM₁- and PM_2.5-associated risks. PM-hospitalization associations exhibited a clear seasonal pattern, with significantly larger risks in cold season than those in warm season among some subgroups.

CONCLUSIONS

Our study suggested that PM₁ rather than PM_1-2.5 contributed to PM_2.5-induced risks of hospitalization for respiratory diseases and effects of PM₁ and PM_2.5 mainly occurred in cold season.

Differentially expressed circular RNAs in air pollution-exposed rat embryos

Circular RNAs (circRNAs) are an important class of non-coding RNAs partly by acting as microRNA sponges. Growing evidence indicates that air pollution exposure during pregnancy could lead to congenital defects in the offspring. In this study, using circRNAs sequencing, we profiled differentially expressed circRNAs in rat embryos exposed to a high concentration (> 200 μg/m³) of fine particulate matter (PM_2.5) in utero. Compared with the control embryos whose mothers were reared in clean air, 25 and 55 circRNAs were found to be downregulated and upregulated, respectively, in the air pollution-exposed group. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses of circRNA-coexpressed genes indicated that segmentation, brain development, and system development together with lysine degradation, Rap1 signaling pathway, and adrenergic signaling were deregulated by in utero air pollution exposure. We also identified the central role of three circRNAs, namely circ_015003, circ_030724, and circ_127215 in the circRNA-microRNA interaction network. These data suggested that circRNA deregulation might play a crucial role in the development of air pollution-associated congenital malformations.

Acute Respiratory Barrier Disruption by Ozone Exposure in Mice

Ozone exposure causes irritation, airway hyperreactivity (AHR), inflammation of the airways, and destruction of alveoli (emphysema), the gas exchange area of the lung in human and mice. This review focuses on the acute disruption of the respiratory epithelial barrier in mice. A single high dose ozone exposure (1 ppm for 1 h) causes first a break of the bronchiolar epithelium within 2 h with leak of serum proteins in the broncho-alveolar space, disruption of epithelial tight junctions and cell death, which is followed at 6 h by ROS activation, AHR, myeloid cell recruitment, and remodeling. High ROS levels activate a novel PGAM5 phosphatase dependent cell-death pathway, called oxeiptosis. Bronchiolar cell wall damage and inflammation upon a single ozone exposure are reversible. However, chronic ozone exposure leads to progressive and irreversible loss of alveolar epithelial cells and alveoli with reduced gas exchange space known as emphysema. It is further associated with chronic inflammation and fibrosis of the lung, resembling other environmental pollutants and cigarette smoke in pathogenesis of asthma, and chronic obstructive pulmonary disease (COPD). Here, we review recent data on the mechanisms of ozone induced injury on the different cell types and pathways with a focus on the role of the IL-1 family cytokines and the related IL-33. The relation of chronic ozone exposure induced lung disease with asthma and COPD and the fact that ozone exacerbates asthma and COPD is emphasized.

Transcriptional Effects of Ozone and Impact on Airway Inflammation

Epidemiological and challenge studies in healthy subjects and in individuals with asthma highlight the health impact of environmental ozone even at levels considered safe. Acute ozone exposure in man results in sputum neutrophilia in 30% of subjects particularly young children, females, and those with ongoing cardiopulmonary disease. This may be associated with systemic inflammation although not in all cases. Chronic exposure amplifies these effects and can result in the formation of asthma-like symptoms and immunopathology. Asthmatic patients who respond to ozone (responders) induce a greater number of genes in bronchoalveolar (BAL) macrophages than healthy responders with up-regulation of inflammatory and immune pathways under the control of cytokines and chemokines and the enhanced expression of remodeling and repair programmes including those associated with protease imbalances and cell-cell adhesion. These pathways are under the control of several key transcription regulatory factors including nuclear factor (NF)-κB, anti-oxidant factors such as nuclear factor (erythroid-derived 2)-like 2 NRF2, the p38 mitogen activated protein kinase (MAPK), and priming of the immune system by up-regulating toll-like receptor (TLR) expression. Murine and cellular models of acute and chronic ozone exposure recapitulate the inflammatory effects seen in humans and enable the elucidation of key transcriptional pathways. These studies emphasize the importance of distinct transcriptional networks in driving the detrimental effects of ozone. Studies indicate the critical role of mediators including IL-1, IL-17, and IL-33 in driving ozone effects on airway inflammation, remodeling and hyperresponsiveness. Transcription analysis and proof of mechanisms studies will enable the development of drugs to ameliorate the effects of ozone exposure in susceptible individuals.