Ambient PM2.5 and Health: Does PM2.5 Oxidative Potential Play a Role?

New health index derived from oxidative potential and cell toxicity of fine particulate matter to assess its potential health effect

Toxicological data and exposure levels of fine particulate matters (PM2.5) are necessary to better understand their health effects. Simultaneous measurements of PM2.5 oxidative potential (OP) and cell toxicity in urban areas (Beijing, China and Gwangju, Korea) reveal their dependence on chemical composition. Notably, acids (Polar), benzocarboxylic acids, and Pb were the chemical components that affected both OP and cell toxicity. OP varied more significantly among different locations and seasons (winter and summer) than cell toxicity. Using the measured OP, cell toxicity, and PM2.5 concentration, a health index was developed to better assess the potential health effects of PM2.5. The health index was related to the sources of PM2.5 derived from the measured chemical components. The contributions of secondary organic aerosols and dust to the proposed health index were more significant than their contributions to PM2.5 mass. The developed regression equation was used to predict the health effect of PM2.5 without further toxicity measurements. This new index could be a valuable health metric that provides information beyond just the PM2.5 concentration level.

Alveolar Type II Cell Damage and Nrf2-SOD1 Pathway Downregulation Are Involved in PM2.5-Induced Lung Injury in Rats

The general toxicity of fine particulate matter (PM_2.5) has been intensively studied, but its pulmonary toxicities are still not fully understood. To investigate the changes of lung tissue after PM_2.5 exposure and identify the potential mechanisms of pulmonary toxicity, PM_2.5 samples were firstly collected and analyzed. Next, different doses of PM_2.5 samples (5 mg/kg, 10 mg/kg, 20 mg/kg) were intratracheally instilled into rats to simulate lung inhalation of polluted air. After instillation for eight weeks, morphological alterations of the lung were examined, and the levels of oxidative stress were detected. The data indicated that the major contributors to PM_2.5 mass were organic carbon, elemental carbon, sulfate, nitrate, and ammonium. Different concentrations of PM_2.5 could trigger oxidative stress through increasing reactive oxygen species (ROS) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels, and decreasing expression of antioxidant-related proteins (nuclear factor erythroid 2-related factor 2 (Nrf2), superoxide dismutase 1 (SOD1) and catalase). Histochemical staining and transmission electron microscopy displayed pulmonary inflammation, collagen deposition, mitochondrial swelling, and a decreasing number of multilamellar bodies in alveolar type II cells after PM_2.5 exposure, which was related to PM_2.5-induced oxidative stress. These results provide a basis for a better understanding of pulmonary impairment in response to PM_2.5.

Associations of Short-Term Exposure to Fine Particulate Matter with Neural Damage Biomarkers: A Panel Study of Healthy Retired Adults

Exposure to fine particulate matter (PM_2.5) is associated with various adverse health effects, such as respiratory and cardiovascular diseases. This study aimed to evaluate the association of PM_2.5 with neural damage biomarkers. A total of 34 healthy retirees were recruited from Xinxiang Medical University from December 2018 to April 2019. Concentrations of PM_2.5 constituents including 24 metals and nonmetallic elements and 6 ions, and 5 biomarkers of neural damage including brain-derived neurotrophic factor (BDNF), neurofilament light chain (NfL), neuron-specific enolase (NSE), protein gene product 9.5 (PGP9.5), and S100 calcium-binding protein B (S100B) in serum were measured. A linear mixed-effect model was employed to estimate the association of PM_2.5 and its constituents with neural damage biomarkers. Modification effects of glutathione S-transferase theta 1 gene (GSTT1) polymorphism, sex, education, and physical activity on PM_2.5 exposure with neural damage were explored. PM_2.5 and its key constituents were significantly associated with neural damage biomarkers. A 10 μg/m³ increase in PM_2.5 concentration was associated with 2.09% (95% CI, 39.3-76.5%), 100% (95% CI, 1.73-198%), and 122% (95% CI, 20.7-222%) increments in BDNF, NfL, and PGP9.5, respectively. Several constituents such as Cu, Zn, Ni, Mn, Sn, V, Rb, Pb, Al, Be, Cs, Co, Th, U, Cl^-, and F^- were significantly associated with NfL. The estimated association of PM_2.5 with NSE in GSTT1-sufficient volunteers was significantly higher than that in GSTT1-null volunteers. Therefore, short-term PM_2.5 exposure was associated with neural damage, and GSTT1 expression levels modified the PM_2.5-induced adverse neural effects.

Hydroxyl Radical Production by Air Pollutants in Epithelial Lining Fluid Governed by Interconversion and Scavenging of Reactive Oxygen Species

Air pollution is a major risk factor for human health. Chemical reactions in the epithelial lining fluid (ELF) of the human respiratory tract result in the formation of reactive oxygen species (ROS), which can lead to oxidative stress and adverse health effects. We use kinetic modeling to quantify the effects of fine particulate matter (PM2.5), ozone (O₃), and nitrogen dioxide (NO₂) on ROS formation, interconversion, and reactivity, and discuss different chemical metrics for oxidative stress, such as cumulative production of ROS and hydrogen peroxide (H₂O₂) to hydroxyl radical (OH) conversion. All three air pollutants produce ROS that accumulate in the ELF as H₂O₂, which serves as reservoir for radical species. At low PM2.5 concentrations (<10 μg m^-3), we find that less than 4% of all produced H₂O₂ is converted into highly reactive OH, while the rest is intercepted by antioxidants and enzymes that serve as ROS buffering agents. At elevated PM2.5 concentrations (>10 μg m^-3), however, Fenton chemistry overwhelms the ROS buffering effect and leads to a tipping point in H₂O₂ fate, causing a strong nonlinear increase in OH production. This shift in ROS chemistry and the enhanced OH production provide a tentative mechanistic explanation for how the inhalation of PM2.5 induces oxidative stress and adverse health effects.

Association between particulate matter air pollution and risk of depression and suicide: a systematic review and meta-analysis

An increasing number of studies examined the potential effects of ambient particulate matter (PM: PM2.5 and PM10-PMs with diameters not greater than 2.5 and 10 μm, respectively) pollution on the risk of depression and suicide; however, the results have been inconclusive. This study aimed to determine the overall relationship between PM exposure and depression/suicide based on current evidence. We conducted a systematic review and meta-analysis of current available studies. Thirty articles (20 for depression and 10 for suicide) with data from 1,447,313 participants were included in the meta-analysis. For a 10 μg/m3 increase in short-term exposure to PM2.5, we found a 2% (p < 0.001) increased the risk of depression and a 2% (p = 0.001) increased risk of suicide. A 10 μg/m3 increase in long-term exposure to PM2.5 was associated with a more apparent increase of 18% (p = 0.005) in depression risk. In addition, a 10 μg/m3 increase in short-term exposure to PM10 was associated with a 2% (p = 0.003) increase in depression risk and a 1% (p = 0.002) increase in suicide risk. Subgroup analyses showed that associations between PM and depression were more apparent in people over 65 years and from developed regions. Besides, the study design and study quality might also have an impact on their associations. The meta-analysis found that an increase in ambient PM concentration was strongly associated with an increased risk of depression and suicide, and the associations for depression appeared stronger for smaller particles (PM2.5) and at a long-term time pattern.

The association between PM2.5 exposure and daily outpatient visits for allergic rhinitis: evidence from a seriously air-polluted environment

Limited evidence was seen as the association between fine particulate matter (PM_2.5) and physician visits for allergic rhinitis (AR), especially in countries with extreme air pollution exposure. This paper addressed the issues about the association between PM_2.5 and daily outpatient visits for AR among individuals residing in Beijing, China. Data on daily outpatient visits for AR obtained from Beijing Medical Claim Data for Employees and daily PM_2.5 concentrations available from US embassy reports were linked by date from January 1, 2010, to June 30, 2012. A time-series analysis was conducted with a generalized additive Poisson model to assess the association between PM_2.5 and AR, adjusting for daily average temperature, relative humidity, day of the week, calendar time, and public holiday. Totally, 229,685 outpatient visits for AR were included in the analysis. The daily mean (SD) concentration of PM_2.5 was 99.5 (75.3) μg/m³ during the study period. We found that a 10-μg/m³ increase in PM_2.5 content was associated with a 0.47% (95% CI: 0.39% to 0.55%) increase in the number of outpatient visits on the same day. Furthermore, results from subgroup analyses suggested that the association was consistently significant among the groups of different ages (< 65 years and ≥ 65 years) and gender. However, this study failed to find a statistically significant association in the autumn season but found significant positive associations during the spring and summer seasons (P for interaction < 0.001). This study indicated a possible association between PM_2.5 and AR outpatients, which may benefit further researches in studying PM_2.5 and its influence on diseases in a real and seriously air-polluted context.

Oxidative Potential Versus Biological Effects: A Review on the Relevance of Cell-Free/Abiotic Assays as Predictors of Toxicity from Airborne Particulate Matter

Background and Objectives: The oxidative potential (OP) of particulate matter (PM) in cell-free/abiotic systems have been suggested as a possible measure of their biological reactivity and a relevant exposure metric for ambient air PM in epidemiological studies. The present review examined whether the OP of particles correlate with their biological effects, to determine the relevance of these cell-free assays as predictors of particle toxicity. Methods: PubMed, Google Scholar and Web of Science databases were searched to identify relevant studies published up to May 2019. The main inclusion criteria used for the selection of studies were that they should contain (1) multiple PM types or samples, (2) assessment of oxidative potential in cell-free systems and (3) assessment of biological effects in cells, animals or humans. Results: In total, 50 independent studies were identified assessing both OP and biological effects of ambient air PM or combustion particles such as diesel exhaust and wood smoke particles: 32 in vitro or in vivo studies exploring effects in cells or animals, and 18 clinical or epidemiological studies exploring effects in humans. Of these, 29 studies assessed the association between OP and biological effects by statistical analysis: 10 studies reported that at least one OP measure was statistically significantly associated with all endpoints examined, 12 studies reported that at least one OP measure was significantly associated with at least one effect outcome, while seven studies reported no significant correlation/association between any OP measures and any biological effects. The overall assessment revealed considerable variability in reported association between individual OP assays and specific outcomes, but evidence of positive association between intracellular ROS, oxidative damage and antioxidant response in vitro, and between OP assessed by the dithiothreitol (DDT) assay and asthma/wheeze in humans. There was little support for consistent association between OP and any other outcome assessed, either due to repeated lack of statistical association, variability in reported findings or limited numbers of available studies. Conclusions: Current assays for OP in cell-free/abiotic systems appear to have limited value in predicting PM toxicity. Clarifying the underlying causes may be important for further advancement in the field.

Association between particulate matter air pollution and risk of depression and suicide: systematic review and meta-analysis

BACKGROUND

Some recent studies examined the effect of ambient particulate matter (PM) pollution on depression and suicide. However, the results have been inconclusive.AimsTo determine the overall relationship between PM exposure and depression/suicide in the general population.

METHOD

We conducted a systematic review and meta-analysis of case-crossover and cohort studies to assess the association between PM2.5 (particles with an aerodynamic diameter of 2.5 µm or less) or PM10 (particles with an aerodynamic diameter between 2.5 and 10 µm) exposure and depression/suicide.

RESULTS

A total of 14 articles (7 for depression and 7 for suicide) with data from 684 859 participants were included in the meta-analysis. With a 10 µg/m3 increase in PM2.5 we found a 19% (odds ratio [95% CI] 1.19 [1.07, 1.33]) increased risk of depression and a marginally increased risk of suicide (odds ratio [95% CI] 1.05 [0.99, 1.11]) in the general population. We did not observe any significant associations between increasing exposure to PM10 and depression/suicide. Sensitivity and subgroup analyses were used to determine the robustness of results. The strongest estimated effect of depression associated with PM2.5 appeared in a long-term lag pattern (odds ratio [95% CI] 1.25 [1.07, 1.45], P &lt; 0.01) and cumulative lag pattern (odds ratio [95% CI] 1.26 [1.07, 1.48], P &lt; 0.01).

CONCLUSIONS

The meta-analysis suggested that an increase in ambient PM2.5 concentration was strongly associated with increased depression risk in the general population, and the association appeared stronger at long-term lag and cumulative lag patterns, suggesting a potential cumulative exposure effect over time.Declaration of interestNone.

Size-resolved particle oxidative potential in the office, laboratory, and home: Evidence for the importance of water-soluble transition metals

Particulate matter (PM) oxidative potential (OP) is an emerging health metric, but studies examining the OP of indoor PM are rare. This paper focuses on the relationships between respiratory exposure to OP and PM water-soluble composition in indoor environments. Size-resolved PM samples were collected between November 2015 and June 2016 from an office, home (including bedroom, living room, and storeroom), and laboratory using a MOUDI sampler. Particles from each source were segregated into eleven size bins, and the water-soluble metal content and dithiothreitol (DTT) loss rate were measured in each PM extract. The water-soluble OP (OP_ws) of indoor PM was highest in the office and lowest in the home, varying by factors of up to 1.2; these variations were attributed to differences in occupation density, occupant activity, and ventilation. In addition, the particulate Cu, Mn, and Fe concentrations were closely correlated with OP_ws in indoor particles; the transition metals may have acted as catalysts during oxidation processes, inducing ·OH formation through the concomitant consumption of DTT. The OP_ws particle size distributions featured single modes with peaks between 0.18 and 3.2 μm across all indoor sites, reflecting the dominant contribution of PM_3.2 to total PM levels and the enhanced oxidative activity of the PM_3.2 compared to PM_>3.2. Lung-deposition model calculations indicated that PM_3.2 dominated the pulmonary deposition of the OP_ws (>75%) due to both the high levels of metals content and the high deposition efficiency in the alveolar region. Therefore, because OP_ws has been directly linked to various health effects, special attention should be given to PM_3.2.

Attributable risk of hospital admissions for overall and specific mental disorders due to particulate matter pollution: A time-series study in Chengdu, China

The associations of particulate matter (PM) pollution with the morbidity of overall and subtypes of mental disorders (MDs), as well as the corresponding morbidity burden, remain understudied, especially in developing countries. This study aimed to evaluate the short-term effects of PM_2.5 (diameters ≤ 2.5 µm), PM₁₀ (diameters ≤ 10 µm) and PM_C (diameters between 2.5 and 10 µm) on hospital admissions (HAs) for MDs in Chengdu, China, during 2015-2016, and calculate corresponding attributable risks. A generalized additive model (GAM) with controlling for time trend, meteorological conditions, holidays and day of the week was used to estimate the associations. Stratified analyses were also performed by age, gender and season. We further estimated the burden of HAs for MDs attributable to PM exposure. During the study period, a total of 10,947 HAs for MDs were collected. PM_2.5, PM₁₀ and PM_C were significantly associated with elevated risks of MDs hospitalizations. Each 10 μg/m³ increase in PM_2.5, PM₁₀ and PM_C at lag06 corresponded to an increase of 2.89% (95% CI: 0.75-5.08%), 1.91% (95% CI: 0.57-3.28%) and 3.95% (95% CI: 0.84-7.15%) in daily HAs for MDs, respectively. The risk estimates of PM on MDs hospitalizations were generally robust after adjustment for gaseous pollutants in two-pollutant models. We found stronger associations between PM pollution and MDs in males and in cool seasons than in females and in warm seasons. For specific subtypes of MDs, significant associations of PM pollution with dementia,schizophrenia and depression were observed. Using WHO's air quality guidelines as the reference concentrations, 9.53% (95% CI: 2.67-15.58%), 9.17% (95% CI: 2.91-14.70%) and 6.10% (95% CI: 1.40-10.32%) of HAs for MDs could be attributable to PM_2.5, PM₁₀ and PM_C, respectively. Our results suggested that PM exposure might be an important trigger of hospitalizations for MDs in Chengdu, China, and account for substantial morbidity burden.

Ambient concentrations of particulate matter and hospitalization for depression in 26 Chinese cities: A case-crossover study

OBJECTIVE

Air pollution with high ambient concentrations of particulate matter (PM) has been frequently reported in China. However, no Chinese study has looked into the short-term effect of PM on hospitalization for depression. We used a time-stratified case-crossover design to identify possible links between ambient PM levels and hospital admissions for depression in 26 Chinese cities.

METHODS

Electronic hospitalization summary reports (January 1, 2014-December 31, 2015) were used to identify hospital admissions related to depression. Conditional logistic regression was applied to determine the association between PM levels and hospitalizations for depression, with stratification by sex, age, and comorbidities.

RESULTS

Both PM_2.5 and PM₁₀ levels were positively associated with the number of hospital admissions for depression. The strongest effect was observed on the day of exposure (lag day 0) for PM₁₀, with an interquartile range increase in PM₁₀ associated with a 3.55% (95% confidence interval: 1.69-5.45) increase in admissions for depression. For PM_2.5, the risks of hospitalization peaked on lag day 0 (2.92; 1.37-4.50) and lag day 5 (3.65; 2.09-5.24). The elderly (>65) were more sensitive to PM_2.5 exposure (9.23; 5.09-13.53) and PM₁₀ exposure (6.35; 3.31-9.49) on lag day 0, and patients with cardiovascular disease were likely to be hospitalized for depression following exposure to high levels of PM₁₀ (4.47; 2.13-6.85).

CONCLUSIONS

Short-term elevations in PM may increase the risk of hospitalization for depression, particularly in the elderly and in patients with cardiovascular disease.

Reducing mortality risk by targeting specific air pollution sources: Suva, Fiji

Health implications of air pollution vary dependent upon pollutant sources. This work determines the value, in terms of reduced mortality, of reducing ambient particulate matter (PM_2.5: effective aerodynamic diameter 2.5μm or less) concentration due to different emission sources. Suva, a Pacific Island city with substantial input from combustion sources, is used as a case-study. Elemental concentration was determined, by ion beam analysis, for PM_2.5 samples from Suva, spanning one year. Sources of PM_2.5 have been quantified by positive matrix factorisation. A review of recent literature has been carried out to delineate the mortality risk associated with these sources. Risk factors have then been applied for Suva, to calculate the possible mortality reduction that may be achieved through reduction in pollutant levels. Higher risk ratios for black carbon and sulphur resulted in mortality predictions for PM_2.5 from fossil fuel combustion, road vehicle emissions and waste burning that surpass predictions for these sources based on health risk of PM_2.5 mass alone. Predicted mortality for Suva from fossil fuel smoke exceeds the national toll from road accidents in Fiji. The greatest benefit for Suva, in terms of reduced mortality, is likely to be accomplished by reducing emissions from fossil fuel combustion (diesel), vehicles and waste burning.

Fine particulate air pollution and hospital visits for asthma in Beijing, China

Data on fine particulate matter (PM_2.5) in China were first announced in 2013. The primary objective of this study was to evaluate the acute effects of PM_2.5 on asthma morbidity in Beijing, China. A total of 978,658 asthma hospital visits consisting of 928,607 outpatient visits, 40,063 emergency room visits and 9988 hospital admissions from January 1, 2010, to June 30, 2012, were identified from the Beijing Medical Claim Data for Employees. A generalized additive Poisson model was applied to explore the association between PM_2.5 and health service use. The mean daily PM_2.5 concentration was 99.5 μg/m³ with a range from 7.2 μg/m³ to 492.8 μg/m³. Ambient PM_2.5 concentration was significantly associated with increased use of asthma-related health services. Every 10 μg/m³ increase in PM_2.5 concentration on the same day was significantly associated with a 0.67% (95% CI, 0.53%-0.81%), 0.65% (95% CI, 0.51%-0.80%), and 0.49% (95% CI, 0.35%-0.64%) increase in total hospital visits, outpatient visits and emergency room visits, respectively. The exposure-response association between PM_2.5 concentration and hospital visits for asthma exacerbations was approximately linear. In conclusion, this study found that short-term elevations in PM_2.5 concentration may increase the risk of asthma exacerbations. Our findings contribute to the limited scientific literature concerning the acute effects of PM_2.5 on asthma morbidity outcomes in developing countries.

Associations between Ambient Fine Particulate Oxidative Potential and Cardiorespiratory Emergency Department Visits

BACKGROUND

Oxidative potential (OP) has been proposed as a measure of toxicity of ambient particulate matter (PM).

OBJECTIVES

Our goal was to address an important research gap by using daily OP measurements to conduct population-level analysis of the health effects of measured ambient OP.

METHODS

A semi-automated dithiothreitol (DTT) analytical system was used to measure daily average OP (OP^DTT) in water-soluble fine PM at a central monitor site in Atlanta, Georgia, over eight sampling periods (a total of 196 d) during June 2012-April 2013. Data on emergency department (ED) visits for selected cardiorespiratory outcomes were obtained for the five-county Atlanta metropolitan area. Poisson log-linear regression models controlling for temporal confounders were used to conduct time-series analyses of the relationship between daily counts of ED visits and either the 3-d moving average (lag 0-2) of OP^DTT or same-day OP^DTT. Bipollutant regression models were run to estimate the health associations of OP^DTT while controlling for other pollutants.

RESULTS

OP^DTT was measured for 196 d (mean=0.32 nmol/min/m³, interquartile range=0.21). Lag 0-2 OP^DTT was associated with ED visits for respiratory disease (RR=1.03, 95% confidence interval (CI): 1.00, 1.05 per interquartile range increase in OP^DTT), asthma (RR=1.12, 95% CI: 1.03, 1.22), and ischemic heart disease (RR=1.19, 95% CI: 1.03, 1.38). Same-day OP^DTT was not associated with ED visits for any outcome. Lag 0-2 OP^DTT remained a significant predictor of asthma and ischemic heart disease in most bipollutant models.

CONCLUSIONS

Lag 0-2 OP^DTT was associated with ED visits for multiple cardiorespiratory outcomes, providing support for the utility of OP^DTT as a measure of fine particle toxicity. https://doi.org/10.1289/EHP1545.

Long-term exposure to PM2.5 lowers influenza virus resistance via down-regulating pulmonary macrophage Kdm6a and mediates histones modification in IL-6 and IFN-β promoter regions

Atmospheric particulates, especially PM2.5, not only damage the respiratory system, but also play important roles in pulmonary immunity. China is influenced by atmospheric diffusion conditions, industrial manufacturers, and heating and discharging. PM2.5 levels in the air rise substantially in the winter, which is also a period of flu high-incidence. Although an epidemiological link exists between PM2.5 and flu, we do not understand how long-term PM2.5 inhalation affects pulmonary immunity and the influenza virus response. Our study has prepared an in vivo PM2.5 mouse pharyngeal wall drop-in model and has found that PM2.5 exposure leads to mouse inflammatory injuries and furthers influenza A infection. Our results suggest that short-term exposure to PM2.5 significantly enhances the survival rate of influenza A-contaminated mice, while long-term PM2.5 inhalation lowers the capacity of pulmonary macrophages to secrete IL-6 and IFN-β. A disorder in the pulmonary innate defense system results in increased death rates following influenza infection. On a macromolecular level, this mechamism involves Kdm6a down-regulation after long-term exposure to PM 2.5 and a resultant increase in H3K4 and H3K9 methylation in IL-6 and IFN-β promoter regions. In summary, PM2.5 causes injuries of lung tissue cells and downregulates immune defense mechanisms in the lung.