The oxidative potential and biological effects induced by PM10 obtained in Mexico City and at a receptor site during the MILAGRO Campaign

Hemolytic Properties of Fine Particulate Matter (PM2.5) in In Vitro Systems

Epidemiological studies have suggested that inhalation exposure to particulate matter (PM) air pollution, especially fine particles (i.e., PM2.5 (PM with an aerodynamic diameter of 2.5 microns or less)), is causally associated with cardiovascular health risks. To explore the toxicological mechanisms behind the observed adverse health effects, the hemolytic activity of PM2.5 samples collected during different pollution levels in Beijing was evaluated. The results demonstrated that the hemolysis of PM2.5 ranged from 1.98% to 7.75% and demonstrated a clear dose-response relationship. The exposure toxicity index (TI) is proposed to represent the toxicity potential of PM2.5, which is calculated by the hemolysis percentage of erythrocytes (red blood cells, RBC) multiplied by the mass concentration of PM2.5. In a pollution episode, as the mass concentration increases, TI first increases and then decreases, that is, TI (low pollution levels) < TI (heavy pollution levels) < TI (medium pollution levels). In order to verify the feasibility of the hemolysis method for PM toxicity detection, the hemolytic properties of PM2.5 were compared with the plasmid scission assay (PSA). The hemolysis results had a significant positive correlation with the DNA damage percentages, indicating that the hemolysis assay is feasible for the detection of PM2.5 toxicity, thus providing more corroborating information regarding the risk to human cardiovascular health.

Moss (Hypnum amabile) as biomonitor of genotoxic damage and as bioaccumulator of atmospheric pollutants at five different sites of Mexico City and metropolitan area

Mexico City has been classified as one megacity, its altitude, thermal inversions, and high seasonal radiation are factors that prevent dispersion of pollutants, which effects are detrimental to health. Therefore, it is important to have an organism that allows evaluate the damage caused by such exposure, as is the case of mosses that obtain nutrients from the atmosphere; this property makes them excellent biomonitors to evaluate genotoxic damage caused by exposure to pollutants, in addition to its large accumulation capacity. For these reasons and to relate the effects of atmospheric pollution with a biological response, we propose to use the moss Hypnum amabile as a bioaccumulator of atmospheric pollutants and biomonitor of the genotoxic effect that the air pollution can induce it through the comet assay. Mosses were placed in five localities of Mexico City and the metropolitan area on the first days of each month of the dry (cold and warm) and rainy seasons, with a 30-day exposure, after which they were changed for a new sample (for 8 months). Each month, the moss exposed was collected and nuclei were isolated to perform comet assay. To demonstrate heavy metal bioaccumulation capacity, samples were observed in a transmission electron microscope and qualitative microanalysis by scanning electron microscopy was carried out parallel. The chemical analysis detected 14 heavy metals by mass spectrometry method with inductively coupled plasma source. Additionally, 22 polycyclic aromatic hydrocarbons were also determined by gas chromatography-mass spectrometry. Analysis of variance and Kruskal-Wallis test were performed to compare DNA damage of each station against control, which was maintained in the laboratory in a chamber with filtered air. This is the first study on the genotoxicity of mosses exposed to the atmosphere of Mexico City and metropolitan area that in addition to proving their accumulation capacity shows their ability to respond to atmospheric pollutants.

Introductory lecture: air quality in megacities

Urbanization is an ongoing global phenomenon as more and more people are moving from rural to urban areas for better employment opportunities and a higher standard of living, leading to the growth of megacities, broadly defined as urban agglomeration with more than 10 million inhabitants. Intense activities in megacities induce high levels of air pollutants in the atmosphere that harm human health, cause regional haze and acid deposition, damage crops, influence air quality in regions far from the megacity sources, and contribute to climate change. Since the Great London Smog and the first recognized episode of Los Angeles photochemical smog seventy years ago, substantial progress has been made in improving the scientific understanding of air pollution and in developing emissions reduction technologies. However, much remains to be understood about the complex processes of atmospheric oxidation mechanisms; the formation and evolution of secondary particles, especially those containing organic species; and the influence of emerging emissions sources and changing climate on air quality and health. While air quality has substantially improved in megacities in developed regions and some in the developing regions, many still suffer from severe air pollution. Strong regional and international collaboration in data collection and assessment will be beneficial in strengthening the capacity. This article provides an overview of the sources of emissions in megacities, atmospheric physicochemical processes, air quality trends and management in a few megacities, and the impacts on health and climate. The challenges and opportunities facing megacities due to lockdown during the COVID-19 pandemic is also discussed.

Effect of PM characterization on PM oxidative potential by acellular assays: a review

The health risks brought by particles cannot be present via a sole parameter. Instead, the particulate matter oxidative potential (PM OP), which expresses combined redox properties of particles, is used as an integrated metric to assess associated hazards and particle-induced health effects. OP definition provides the capacity of PM toward target oxidation. The latest technologies of a cellular OP measurement has been growing in relevant studies. In this review, OP measurement techniques are focused on discussing along with PM characterization because of many related studies via OP measurements investigating relationship with human health. Many OP measurement methods, such as dithiothreitol (DTT), ascorbic acid (AA), glutathione (GSH) assay and other a cellular assays, are used to study the association between PM toxicity and PM characterization that make different responses, including PM components, size and sources. Briefly, AA and DTT assays are sensitive to metals (such as copper, manganese and iron etc.) and organics (quinones, VOCs and PAH). Measured OP have significant association with certain PM-related end points, for example, lung cancer, COPD and asthma. Literature has found that exposure to measured OP has higher risk ratios than sole PM mass, which may be containing the PM health-relevant fraction. PM characterization effect on health via OP measurement display a promising method.

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.

Experience from Integrated Air Quality Management in the Mexico City Metropolitan Area and Singapore

More than half of the world’s population now lives in cities as a result of unprecedented urbanization during the second half of the 20th century. The urban population is projected to increase to 68% by 2050, with most of the increase occurring in Asia and Africa. Population growth and increased energy consumption in urban areas lead to high levels of atmospheric pollutants that harm human health, cause regional haze, damage crops, contribute to climate change, and ultimately threaten the society’s sustainability. This article reviews the air quality and compares the policies implemented in the Mexico City Metropolitan Area (MCMA) and Singapore and offers insights into the complexity of managing air pollution to protect public health and the environment. While the differences in the governance, economics, and culture of the two cities greatly influence the decision-making process, both have made much progress in reducing concentrations of harmful pollutants by implementing comprehensive integrated air quality management programs. The experience and the lessons learned from the MCMA and Singapore can be valuable for other urban centers, especially in the fast-growing Asia-Pacific region confronting similar air pollution problems.

Chemical composition of PM10 and its effect on in vitro hemolysis of human red blood cells (RBCs): a comparison study during dust storm and inversion

PURPOSE

This study aimed to investigate chemical composition of PM₁₀ (particulate matter with aerodynamic diameter ≤ 10 μm) during dust storm and inversion in Tehran and hemolysis effects.

METHODS

PM₁₀ was sampled in Tehran, Iran, during dust storm and inversion conditions. Water soluble ions (F¯, Cl¯, NO₂¯, NO₃¯, SO₄¯², Na⁺, K⁺, NH₄ ⁺, Ca⁺², Mg⁺²) and elements (Al, Ba, Cd, Co, Cr, Cu, Fe, Li, Mn, Mo, Ni, Pb, Se, Sn, Sr, V, Zn, Pt, Rh, Pd, As and Si) were analyzed by ion chromatograph (IC) and inductively coupled plasma optical emission spectrometer (ICP-OES), respectively. Hemolysis was examined as in vitro at PM₁₀ concentrations of 50-300 μg/ml.

RESULTS

Daily average of PM₁₀ concentrations in dusty and inversion days were 348.40 and 220.54 μg/m³, respectively. Most prevalence ionic components were NO₃¯, Cl¯, SO₄¯² and Ca⁺² during dust storm and SO₄¯², NO₃¯, Cl¯ and NH₄ ⁺ during inversion. Si, Fe and Al had the maximum values in both conditions. Particles associated with both conditions induced hemolytic responses. PM₁₀ from dusty day showed a higher hemolysis percent (10.24 ± 4.67%) than inversion (9.08 ± 5.47%), but this difference was not significant (p = 0.32). Hemolytic effects were significantly intensified by increased PM concentrations (p < 0.001) in a dose-response manner.

CONCLUSIONS

As the results, chemical composition of sampled particles from inversion days and dust storm was different from each other. Hemolytic effects of particles during dust storm were more than inversion days. However, this difference was not statistically significant.

Investigation and Comparison of In Vitro Genotoxic Potency of PM10 Collected in Rural and Urban Sites at Tehran in Different Metrological Conditions and Different Seasons

The particulate matter has become a serious health problem in some large cities in the world. These particles are a complex mixture of chemical compounds which change based on location and time and, consequently, can cause different health-related effects. The exact mechanism of the effect of these particles is not yet known for certain. However, it seems that numerous mechanisms through the production of ROS and, eventually, DNA destruction, which are related to a wide range of diseases, are among the causes of particles' health-related effects. The present study is aimed to evaluate and compare the genotoxicity potential of particles collected in Tehran, Iran, in urban and rural regions during spring and autumn as well as dusty and inversion conditions. These effects were examined using the comet assay on human pulmonary epithelial cells (A549). Results showed that all the particles had the potential for genotoxicity at the concentration used in this study (75,150 and 300 μg/ml). Moreover, DNA destruction changed with season, site, and even dusty and inversion atmospheric conditions. These changes mostly belonged to urban particles. In general, urban particles in autumn and, specifically, on days with inversion had higher genotoxicity (p < 0.01). Difference was observed between dusty and regular days so that regular days were more potent (p < 0.05). A strong correlation was observed between the effects of most PAH compounds and other metals such as Cr, Co, Cd, Mn, As, and also SO₄, which were mostly the result of combustion in vehicle engines in urban regions. No difference was observed for rural particles at different conditions and seasons.

Indicators of environmental contamination by heavy metals in leaves of Taraxacum officinale in two zones of the metropolitan area of Mexico City

The present study was designed to detect the effect of heavy metals in two zones of the Metropolitan Area of Mexico City (MAMC), the Centro de Ciencias de la Atmósfera (CCA), and the Altzomoni station in the Iztaccíhuatl-Popocatépetl National Park. Taraxacum officinale was selected as the indicator organism of responses to atmospheric contamination by heavy metals. Determinations of heavy metals were performed, and total mRNA was extracted to quantify the expression of microRNA398 (miR398), superoxide dismutase 2 (CSD2), and the amounts of free radicals using the bromide of 3-(4,5-dimethylthiazole-2-ilo)-2,5-diphenyltetrazole (MTT) salts reduction assay. Results from the Altzomoni station showed high concentrations of five heavy metals, especially Aluminum, while three heavy metals were identified in the CCA-UNAM zone, most importantly, Vanadium, both in the dry season; miR398 expression presented subtle changes but was greater in the leaves from the stations with higher concentrations of heavy metals. Observations included a significant expression of CSD2, mainly in the dry season in both study zones, where levels were significant with respect to controls (p < 0.05). Reduced MTT was also higher in the dry season than in the rainy season (p < 0.05). In conclusion, the increase in heavy metals on the leaves of Taraxacum officinale induces increased expression of the CSD2 gene and reduced MTT; thus, they can be used as indicators for biomonitoring heavy metal concentrations.

Recent advances in particulate matter and nanoparticle toxicology: a review of the in vivo and in vitro studies

Epidemiological and clinical studies have linked exposure to particulate matter (PM) to adverse health effects, which may be registered as increased mortality and morbidity from various cardiopulmonary diseases. Despite the evidence relating PM to health effects, the physiological, cellular, and molecular mechanisms causing such effects are still not fully characterized. Two main approaches are used to elucidate the mechanisms of toxicity. One is the use of in vivo experimental models, where various effects of PM on respiratory, cardiovascular, and nervous systems can be evaluated. To more closely examine the molecular and cellular mechanisms behind the different physiological effects, the use of various in vitro models has proven to be valuable. In the present review, we discuss the current advances on the toxicology of particulate matter and nanoparticles based on these techniques.

Prooxidant and proinflammatory potency of air pollution particulate matter (PM₂.₅₋₀.₃) produced in rural, urban, or industrial surroundings in human bronchial epithelial cells (BEAS-2B)

Compelling evidence indicates that exposure to air pollution particulate matter (PM) affects human health. However, how PM composition interacts with PM-size to cause adverse health effects needs elucidation. In this study, we were also interested in the physicochemical characteristics and toxicological end points of PM₂.₅₋₀.₃ samples produced in rural, urban, or industrial surroundings, thereby expecting to differentiate their respective in vitro adverse health effects in human bronchial epithelial cells (BEAS-2B). Physicochemical characteristics of the three PM₂.₅₋₀.₃ samples, notably their inorganic and organic components, were closely related to their respective emission sources. Referring also to the dose/response relationships of the three PM₂.₅₋₀.₃ samples, the most toxicologically relevant exposure times (i.e., 24, 48, and 72 h) and doses (i.e., 3.75 μg PM/cm² and 15 μg PM/cm²) to use to study the underlying mechanisms of action involved in PM-induced lung toxicity were chosen. Organic chemicals adsorbed on the three PM₂.₅₋₀.₃ samples (i.e., polycyclic aromatic hydrocarbons) were able to induce the gene expression of xenobiotic-metabolizing enzymes (i.e., Cytochrome P4501A1 and 1B1, and, to a lesser extent, NADPH-quinone oxidoreductase-1). Moreover, intracellular reactive oxygen species within BEAS-2B cells exposed to the three PM₂.₅₋₀.₃ samples induced oxidative damage (i.e., 8-hydroxy-2'-deoxyguanosine formation, malondialdehyde production and/or glutathione status alteration). There were also statistically significant increases of the gene expression and/or protein secretion of inflammatory mediators (i.e., notably IL-6 and IL-8) in BEAS-2B cells after their exposure to the three PM₂.₅₋₀.₃ samples. Taken together, the present findings indicated that oxidative damage and inflammatory response preceeded cytotoxicity in air pollution PM₂.₅₋₀.₃-exposed BEAS-2B cells and supported the idea that PM-size, composition, and origin could interact in a complex manner to determine the in vitro responsiveness to PM.

Relationship between physicochemical characterization and toxicity of fine particulate matter (PM2.5) collected in Dakar city (Senegal)

The massive increase in emissions of air pollutants due to economic and industrial growth in developing countries has made air quality a crucial health problem in this continent. Hence, it is somewhat critical to have a better knowledge on the air pollution in Sub-Saharan Africa countries. Three air pollution PM2.5 samples were also collected in two urban sites (i.e., Fann and Faidherbe) in Dakar (Senegal) and in a rural site near Dakar (i.e., Ngaparu). The two urban sites mainly differ in the type of used vehicles: in Fann, most of the traffic is made of buses, which are absent, in Faidherbe. The physicochemical characteristics of the three PM2.5 samples revealed their high heterogeneities and complexities, related to the multiple natural and anthropogenic emission sources. Results from 5-bromodeoxyuridine incorporation into DNA, mitochondrial dehydrogenase activity, and extracellular lactate dehydrogenase activity in PM2.5-exposed BEAS-2B cells suggested the exposure conditions (i.e., 3 and 12 μg PM/cm² during 24, 48, and 72 h) to further consider. The organic fractions (i.e., mainly PAHs) of the PM(2.5) samples were able to induce a time and/or concentration-dependent gene expression of CYP1A1 and CYP1B1, and, to a lesser extent, NQO1. There was a time and/or dose-dependent increase of both the gene expression and/or protein secretion of inflammatory mediators (i.e., TNF-α, IL-1β, IL-6, and/or IL-8) in PM(2.5)-exposed BEAS-2B cells. In agreement with the physicochemical characterization, urban PM(2.5) samples caused greater biological responses in BEAS-2B cells than the rural one. Variable concentrations of transition metals (i.e., Fe, Al, Pb, Mn, Zn) and organic compounds (i.e., PAHs) founded in the three PM2.5 samples might be firmly involved in a time- and/or dose-dependent toxicity, relying on inflammatory processes.