Oxidative stress and NFkappaB activation in the lungs of rats: a synergistic interaction between soot and iron particles

Synthetic vitreous fibers (SVFs): adverse outcome pathways (AOPs) and considerations for next generation new approach methods (NAMs)

Fiber dimension, durability/dissolution, and biopersistence are critical factors for the risk of fibrogenesis and carcinogenesis. In the modern era, to reduce, refine, and replace animals in toxicology research, the application of in vitro test methods is paramount for hazard evaluation and designing synthetic vitreous fibers (SVFs) for safe use. The objectives of this review are to: (1) summarize the international frameworks and acceptability criteria for implementation of new approach methods (NAMs), (2) evaluate the adverse outcome pathways (AOPs), key events (KEs), and key event relationships (KERs) for fiber-induced fibrogenesis and carcinogenesis in accordance with Organization for Economic Co-operation and Development (OECD) guidelines, (3) consider existing and emerging technologies for in silico and in vitro toxicity testing for the respiratory system and the ability to predict effects in vivo, (4) outline a recommended testing strategy for evaluating the hazard and safety of novel SVFs, and (5) reflect on methods needs for in vitro in vivo correlation (IVIVC) and predictive approaches for safety assessment of new SVFs. AOP frameworks following the conceptual model of the OECD were developed through an evaluation of available molecular and cellular initiating events, which lead to KEs and KERs in the development of fiber-induced fibrogenesis and carcinogenesis. AOP framework development included consideration of fiber physicochemical properties, respiratory deposition and clearance patterns, biosolubility, and biopersistence, as well as cellular, organ, and organism responses. Available data support that fiber AOPs begin with fiber physicochemical characteristics which influence fiber exposure and biosolubility and subsequent key initiating events are dependent on fiber biopersistence and reactivity. Key cellular events of pathogenic fibers include oxidative stress, chronic inflammation, and epithelial/fibroblast proliferation and differentiation, which ultimately lead to hyperplasia, metaplasia, and fibrosis/tumor formation. Available in vitro models (e.g. single-, multi-cellular, organ system) provide promising NAMs tools to evaluate these intermediate KEs. However, data on SVFs demonstrate that in vitro biosolubility is a reasonable predictor for downstream events of in vivo biopersistence and biological effects. In vitro SVF fiber dissolution rates >100 ng/cm2/hr (glass fibers in pH 7 and stone fibers in pH 4.5) and in vivo SVF fiber clearance half-life less than 40 or 50 days were not associated with fibrosis or tumors in animals. Long (fiber lengths >20 µm) biodurable and biopersistent fibers exceeding these fiber dissolution and clearance thresholds may pose a risk of fibrosis and cancer. In vitro fiber dissolution assays provide a promising avenue and potentially powerful tool to predict in vivo SVF fiber biopersistence, hazard, and health risk. NAMs for fibers (including SVFs) may involve a multi-factor in vitro approach leveraging in vitro dissolution data in complement with cellular- and tissue- based in vitro assays to predict health risk.

The Associations of Prenatal Exposure to Fine Particulate Matter and Its Chemical Components with Allergic Rhinitis in Children and the Modification Effect of Polyunsaturated Fatty Acids: A Birth Cohort Study

BACKGROUND

Polyunsaturated fatty acids (PUFAs) have been shown to protect against fine particulate matter < 2.5 μ m in aerodynamic diameter (PM 2.5 )-induced hazards. However, limited evidence is available for respiratory health, particularly in pregnant women and their offspring.

OBJECTIVES

We aimed to investigate the association of prenatal exposure to PM 2.5 and its chemical components with allergic rhinitis (AR) in children and explore effect modification by maternal erythrocyte PUFAs.

METHODS

This prospective birth cohort study involved 657 mother-child pairs from Guangzhou, China. Prenatal exposure to residential PM 2.5 mass and its components [black carbon (BC), organic matter (OM), sulfate (SO 4 2 - ), nitrate (NO 3 - ), and ammonium (NH 4 + )] were estimated by an established spatiotemporal model. Maternal erythrocyte PUFAs during pregnancy were measured using gas chromatography. The diagnosis of AR and report of AR symptoms in children were assessed up to 2 years of age. We used Cox regression with the quantile-based g-computation approach to assess the individual and joint effects of PM 2.5 components and examine the modification effects of maternal PUFA levels.

RESULTS

Approximately 5.33 % and 8.07% of children had AR and related symptoms, respectively. The average concentration of prenatal PM 2.5 was 35.50 ± 5.31   μ g / m 3 . PM 2.5 was positively associated with the risk of developing AR [hazard ratio ( HR ) = 1.85 ; 95% confidence interval (CI): 1.16, 2.96 per 5   μ g / m 3 ] and its symptoms (HR = 1.79 ; 95% CI: 1.22, 2.62 per 5   μ g / m 3 ) after adjustment for confounders. Similar associations were observed between individual PM 2.5 components and AR outcomes. Each quintile change in a mixture of components was associated with an adjusted HR of 3.73 (95% CI: 1.80, 7.73) and 2.69 (95% CI: 1.55, 4.67) for AR and AR symptoms, with BC accounting for the largest contribution. Higher levels of n-3 docosapentaenoic acid and lower levels of n-6 linoleic acid showed alleviating effects on AR symptoms risk associated with exposure to PM 2.5 and its components.

CONCLUSION

Prenatal exposure to PM 2.5 and its chemical components, particularly BC, was associated with AR/symptoms in early childhood. We highlight that PUFA biomarkers could modify the adverse effects of PM 2.5 on respiratory allergy. https://doi.org/10.1289/EHP13524.

Characterizing the neuroimmune environment of offspring in a novel model of maternal allergic asthma and particulate matter exposure

Inflammation during pregnancy is associated with an increased risk for neurodevelopmental disorders (NDD). Increased gestational inflammation can be a result of an immune condition/disease, exposure to infection, and/or environmental factors. Epidemiology studies suggest that cases of NDD are on the rise. Similarly, rates of asthma are increasing, and the presence of maternal asthma during pregnancy increases the likelihood of a child being later diagnosed with NDD such as autism spectrum disorders (ASD). Particulate matter (PM), via air pollution, is an environmental factor known to worsen the symptoms of asthma, but also, PM has been associated with increased risk of neuropsychiatric disorders. Despite the links between asthma and PM with neuropsychiatric disorders, there is a lack of laboratory models investigating combined prenatal exposure to asthma and PM on offspring neurodevelopment. Thus, we developed a novel mouse model that combines exposure to maternal allergic asthma (MAA) and ultrafine iron-soot (UIS), a common component of PM. In the current study, female BALB/c mice were sensitized for allergic asthma with ovalbumin (OVA) prior to pregnancy. Following mating and beginning on gestational day 2 (GD2), dams were exposed to either aerosolized OVA to induce allergic asthma or phosphate buffered saline (PBS) for 1 h. Following the 1-h exposure, pregnant females were then exposed to UIS with a size distribution of 55 to 169 nm at an average concentration of 176 ± 45 μg/m3) (SD), or clean air for 4 h, over 8 exposure sessions. Offspring brains were collected at postnatal days (P)15 and (P)35. Cortices and hippocampal regions were then isolated and assessed for changes in cytokines using a Luminex bead-based multiplex assay. Analyses identified changes in many cytokines across treatment groups at both timepoints in the cortex, including interleukin-1 beta (IL-1β), and IL-17, which remained elevated from P15 to P35 in all treatment conditions compared to controls. There was a suppressive effect of the combined MAA plus UIS on the anti-inflammatory cytokine IL-10. Potentially shifting the cytokine balance towards more neuroinflammation. In the hippocampus at P15, elevations in cytokines were also identified across the treatment groups, namely IL-7. The combination of MAA and UIS exposure (MAA-UIS) during pregnancy resulted in an increase in microglia density in the hippocampus of offspring, as identified by IBA-1 staining. Together, these data indicate that exposure to MAA, UIS, and MAA-UIS result in changes in the neuroimmune environment of offspring that persist into adulthood.

Characterizing the Neuroimmune Environment of Offspring in a Novel Model of Maternal Allergic Asthma and Particulate Matter Exposure

Autism spectrum disorders (ASD) are neurodevelopmental disorders characterized by the presence of decreased social interactions and an increase in stereotyped and repetitive behaviors. Epidemiology studies suggest that cases of ASD are on the rise. Similarly, rates of asthma are increasing, and the presence of maternal asthma during pregnancy increases the likelihood of a child being later diagnosed with ASD. Particulate matter (PM), via air pollution, is an environmental factor known to worsen the symptoms of asthma, but also, PM has been associated with increased risk of neuropsychiatric disorders including ASD. Despite the links between asthma and PM with neuropsychiatric disorders, there is a lack of laboratory models investigating combined prenatal exposure to asthma and PM on offspring neurodevelopment. Thus, we developed a novel mouse model that combines exposure to maternal allergic asthma (MAA) and ultrafine iron-soot (UIS), a common component of PM. In the current study, female BALB/c mice were primed for allergic asthma with ovalbumin (OVA) prior to pregnancy. Following mating and beginning on gestational day 2 (GD2), dams were exposed to either aerosolized OVA or phosphate buffered saline (PBS) for 1 hour. Following the 1-hour exposure, pregnant females were then exposed to UIS or clean air for 4 hours. Offspring brains were collected at postnatal days (P)15 and (P)35. Cortices and hippocampal regions were then isolated and assessed for changes in cytokines using a Luminex bead-based multiplex assay. Analyses identified changes in many cytokines across treatment groups at both timepoints in the cortex, including interleukin-1 beta (IL-1β), IL-2, IL-13, and IL-17, which remained elevated from P15 to P35 in all treatment conditions compared to controls. In the hippocampus at P15, elevations in cytokines were also identified across the treatment groups, namely interferon gamma (IFNγ) and IL-7. The combination of MAA and UIS exposure (MAA-UIS) during pregnancy resulted in an increase in microglia density in the hippocampus of offspring, as identified by IBA-1 staining. Together, these data indicate that exposure to MAA, UIS, and MAA-UIS result in changes in the neuroimmune environment of offspring that persist into adulthood.

Effects of Iron Addition on the Collision of Polycyclic Aromatic Hydrocarbon Clusters: A Molecular Dynamics Study

In this work, soot particle size distributions in iron-doped premixed ethylene flames are examined using scanning mobility particle sizer measurements. It is found that iron addition promotes the growth in soot particle size, and the enhanced particle coagulation is inferred to be an important reason. To support that, the influence of iron addition on the coagulation of polycyclic aromatic hydrocarbon (PAH) clusters, the analogue of incipient soot particles, is further investigated using molecular dynamics simulations. Based on the results of hundreds of binary head-on collision simulations, the collision between two coronene-Fe-coronene dimers is found to have a significantly higher coagulation efficiency than that between two coronene dimers. However, this enhancement effect weakens as the size of the PAH monomer increases. Although the coagulation efficiency can be increased by iron addition, the collision frequency is almost unaffected, as revealed from the binary off-central collision simulations. Moreover, the simulation results of coronene cluster growth via coagulation show that iron addition promotes coronene cluster growth, leading to larger cluster size, which may explain the larger soot particle size observed in iron-doped flames.

Inhalable Saharan dust induces oxidative stress, NLRP3 inflammasome activation, and inflammatory cytokine release

Desert dust is increasingly recognized as a major air pollutant affecting respiratory health. Since desert dust exposure cannot be regulated, the hazardousness of its components must be understood to enable health risk mitigation strategies. Saharan dust (SD) comprises about half of the global desert dust and contains quartz, a toxic mineral dust that is known to cause severe lung diseases via oxidative stress and activation of the NLRP3 inflammasome-interleukin-1β pathway. We aimed to assess the physicochemical and microbial characteristics of SD responsible for toxic effects. Also, we studied the oxidative and pro-inflammatory potential of SD in alveolar epithelial cells and the activation of the NLRP3 inflammasome in macrophage-like cells in comparison to quartz dusts and synthetic amorphous silica (SAS). Characterization revealed that SD contained Fe, Al, trace metals, sulfate, diatomaceous earth, and endotoxin and had the capacity to generate hydroxyl radicals. We exposed A549 lung epithelial cells and wild-type and NLRP3^-/- THP-1 macrophage-like cells to SD, three well-investigated quartz dusts, and SAS. SD induced oxidative stress in A549 cells after 24 h more potently than the quartz dusts. The quartz dusts and SAS upregulated interleukin 8 expression after 4 h and 24 h while SD only caused a transient upregulation. SD, the quartz dusts, and SAS induced interleukin-1β release from wild-type THP-1 cells>20-fold stronger than from NLRP3^-/- THP-1 cells. Interleukin-1β release was lower for SD, in which microbial components including endotoxin were heat-destructed. In conclusion, microbial components in SD are pivotal for its toxicity. In the epithelium, the effects of SD contrasted with crystalline and amorphous silica in terms of potency and persistence. In macrophages, the strong involvement of the NLRP3 inflammasome emphasizes the acute and chronic health risks associated with desert dust exposure.

Physicochemical and microbiological characteristics of urban aerosols in Krakow (Poland) and their potential health impact

Eight aerosol samples were collected in Krakow using a low-volume sampler in February and March 2019 during variable meteorological conditions and times of the day, to study their single particles' properties (size, morphology and chemical composition analyzed using a scanning electron microscope fitted with an energy-dispersive spectrometer) and microbiological characteristics. The content of particles of different chemical compositions larger than 2.5 μm was low. Considering the number of the particles, submicron particles strongly dominated with a high content of ultrafine particles (nanoparticles). Tar ball-type particles were relatively common in the studied samples, while soot was the dominant component. Soot was present as small agglomerates composed of few particles, but also as bigger agglomerates. Metal-containing particles of various chemical characteristics were abundant, with transition metals commonly occurring in these particles. The physicochemical characteristics of aerosols indicate that despite a relatively low mass concentration, their adverse health impact could be very strong because of the high content of nanoparticles, the abundance of soot and other fuel combustion-related particles, and the high incidence of transition metal-rich particles. Microbiological analysis was based on cultures on both solid and liquid agar. The MALDI-TOF method was used for species identification-for bacteria and fungi. Twelve different species of bacteria were isolated from the collected samples of aerosols. The most frequently isolated species was Gram-positive sporulating Bacillus licheniformis. The isolated mold fungi were of the genus Aspergillus.

Oxidative potential of atmospheric PM10 at five different sites of Ahmedabad, a big city in Western India

The current study presents the oxidative potential (OP) along with a wide range of chemical speciation of particulate matter with an aerodynamic diameter less than 10 μm (PM₁₀) at five sites representing different environments in Ahmedabad, a big city in western India. On an average, PM₁₀ concentrations were 116 ± 36, 228 ± 43, 133 ± 29, 101 ± 21, and 70 ± 20 μg m^-3; volume-normalized OP (OP_V) were 2.51 ± 0.71, 5.62 ± 0.68, 2.69 ± 0.76, 2.14 ± 0.41, and 1.55 ± 0.51 nmol DTT min^-1 m^-3; and mass-normalized OP (OP_M) were 22 ± 3, 25 ± 5, 21 ± 6, 21 ± 2, and 22 ± 3 pmol DTT min^-1 μg^-1 over Bapunagar (backward residential area), Narol (industrial), Paldi (bus transport hub), Income Tax (huge running traffic) and Science City (posh residential area), respectively. Overall, OP_V showed a significant linear correlation with PM₁₀, whereas OP_M showed near uniformity with increasing PM₁₀. Although the OP_M values were similar, the site-to-site variability in PM₁₀ concentration reflects the corresponding health risks associated with PM₁₀ exposure for the people living in these areas. Further, a noticeable temporal variation in OP_M at Narol and Paldi suggests that species with diverse OP_M contributed to PM₁₀ on different days. A strong linear relationship between the ratio of OP_V to the mass concentration of organic carbon (OP_OC) and the ratio of m/z 43 signal to total water-soluble organic aerosols (WSOA) signals (f43) suggests that the fossil-fuel combustion derived WSOA have higher OP. Furthermore, the relationships of OP with water-soluble trace metals and brown carbon are also investigated and discussed in this paper. Nitrogenous organic compounds particularly emitted from the traffic-related sources in Paldi and Income Tax have higher OP_OC than those emitted from other sources over Bapunagar, Narol, and Science City.

Inflammation response, oxidative stress and DNA damage caused by urban air pollution exposure increase in the lack of DNA repair XPC protein

Air pollution represents a considerable threat to health worldwide. The São Paulo Metropolitan area, in Brazil, has a unique composition of atmospheric pollutants with a population of nearly 20 million people and 9 million passenger cars. It is long known that exposure to particulate matter less than 2.5 µm (PM_2.5) can cause various health effects such as DNA damage. One of the most versatile defense mechanisms against the accumulation of DNA damage is the nucleotide excision repair (NER), which includes XPC protein. However, the mechanisms by which NER protects against adverse health effects related to air pollution are largely unknown. We hypothesized that reduction of XPC activity may contribute to inflammation response, oxidative stress and DNA damage after PM_2.5 exposure. To address these important questions, XPC knockout and wild type mice were exposed to PM_2.5 using the Harvard Ambient Particle concentrator. Results from one-single exposure have shown a significant increase in the levels of anti-ICAM, IL-1β, and TNF-α in the polluted group when compared to the filtered air group. Continued chronic PM_2.5 exposure increased levels of carbonylated proteins, especially in the lung of XPC mice, probably as a consequence of oxidative stress. As a response to DNA damage, XPC mice lungs exhibit increased γ-H2AX, followed by severe atypical hyperplasia. Emissions from vehicles are composed of hazardous substances, with polycyclic aromatic hydrocarbons (PAHs) and metals being most frequently cited as the major contributors to negative health impacts. This analysis showed that benzo[b]fluoranthene, 2-nitrofluorene and 9,10-anthraquinone were the most abundant PAHs and derivatives. Taken together, these findings demonstrate the participation of XPC protein, and NER pathway, in the protection of mice against the carcinogenic potential of air pollution. This implicates that DNA is damaged directly (forming adducts) or indirectly (Reactive Oxygen Species) by the various compounds detected in urban PM_2.5.

Association between the incidence of acute respiratory diseases in children and ambient concentrations of SO2, PM10 and chemical elements in fine particles

The aim of this study consists of investigating the effects of the SO₂, PM₁₀, inorganic chemical elements and black carbon (BC) present in fine particulates on the acute outcomes of respiratory diseases in children up to 12 years of age living in Brazilian urban area in the southern hemisphere during the winter (2013) and summer (2013-2014) months. SO₂ and PM₁₀ concentration data were obtained from six air quality monitoring stations spatially distributed in the area. PM_2.5 samples were collected at the same locations with a MiniVol sampler over a 24-h period on alternating days. The PM_2.5 components were analysed using the energy dispersive X-ray fluorescence and reflectance techniques. Hospital care and admission events due to acute respiratory diseases (n = 8,987) of the coded groups JJ00-JJ99 of the International Code of Diseases (ICD-10) were obtained from three hospitals (one public and two private hospitals). To quantify the association of acute respiratory disease events with pollutant concentrations, a generalized additive model (GAM) with a Poisson distribution was applied. The results showed a greater risk of acute respiratory events due to exposure to SO₂ with a relative risk of 1.28 (95% CI: 1.22-1.34) and to PM₁₀ with a risk of 1.14 (95% CI: 1.09-1.20) on the day of exposure (lag 0). The chemical constituents present in the fine particles with the highest risk for acute respiratory diseases were Si with a risk of 1.22 (95% CI: 1.15-1.29), S with a risk of 1.09 (95% CI: 1.06-1.12), Ti with a risk of 1.09 (95% CI: 1.01-1.17), BC with a risk of 1.07 (95% CI: 1.03-1.11), Se with a risk of 1.03 (95% CI: 0.96-1.10) and Ni with a risk of 1.03 (95% CI: 0.96-1.10).

The aryl hydrocarbon receptor as a target of environmental stressors - Implications for pollution mediated stress and inflammatory responses

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor regulating the expression of genes, for instance encoding the monooxygenases cytochrome P450 (CYP) 1A1 and CYP1A2, which are important enzymes in metabolism of xenobiotics. The AHR is activated upon binding of polycyclic aromatic hydrocarbons (PAHs), persistent organic pollutants (POPs), and related ubiquitous environmental chemicals, to mediate their biological and toxic effects. In addition, several endogenous and natural compounds can bind to AHR, thereby modulating a variety of physiological processes. In recent years, ambient particulate matter (PM) associated with traffic related air pollution (TRAP) has been found to contain significant amounts of PAHs. PM containing PAHs are of increasing concern as a class of agonists, which can activate the AHR. Several reports show that PM and AHR-mediated induction of CYP1A1 results in excessive generation of reactive oxygen species (ROS), causing oxidative stress. Furthermore, exposure to PM and PAHs induce inflammatory responses and may lead to chronic inflammatory diseases, including asthma, cardiovascular diseases, and increased cancer risk. In this review, we summarize findings showing the critical role that the AHR plays in mediating effects of environmental pollutants and stressors, which pose a risk of impacting the environment and human health.

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PAHs present on ambient air pollution particles are ligands of the cellular AHR.

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AHR-dependent induction of CYP1, AKR, NOX and COX-2 genes can be a source of ROS generation.

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AHR signaling and NRF2 signaling interact to regulate the expression of antioxidant genes.

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Air pollution and ROS can affect inflammation, which is partially triggered by AHR and associated immune responses.

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Skin, lung, and the cardiovascular system are major target sites for air pollution-induced inflammation.

Assessment of Interactions between Transition Metals and Atmospheric Organics: Ascorbic Acid Depletion and Hydroxyl Radical Formation in Organic-Metal Mixtures

Excessive oxidative stress has been recognized as an important cause of the adverse health effects associated with exposure to ambient particulate matter (PM). Transition metals (TMs) (e.g., iron (Fe) and copper (Cu)) are known catalysts in the formation of reactive oxygen species (ROS) in surrogate lung fluid containing antioxidants. Humic-like substances (HULIS), extracted from atmospheric aerosols, retain the compositional complexity of real-world samples. It contains mixtures of organics that chelate TMs and was used in this work to examine the roles of atmospheric organics in affecting ROS formation and antioxidant depletion by TMs. Two types of metal-binding organics known to be present in HULIS, oxygen-containing (i.e., carboxylic acids) and reduced-nitrogen-containing organics (i.e., imidazoles), were first investigated for their effects on the ascorbic acid depletion (denoted as OP_AA) and hydroxyl radical formation (denoted as OP_•OH) from both Fe(II) and Cu(II) in phosphate buffered saline (pH 7.40) containing ascorbic acid. Our results show that carboxylic acids enhance the OP_AA and OP_•OH by TMs while imidazoles suppress them. Similar experiments using three HULIS samples with distinctly different chemical compositions revealed complexity in metal-organics interactions. While ambient HULIS showed negligible impacts, two biomass burning source HULIS samples from rice straw and sugar cane leaf burning displayed unambiguous suppression or enhancement effects on OP_AA and OP_•OH by TMs. The effect was metal-specific and source HULIS-specific. The distinct behaviors of the three HULIS types can be explained by their different chemical compositions, for example, outstanding higher level of alkaloid compounds (e.g., imidazoles) in rice straw burning HULIS was consistent with the suppression effect exerted by this source of HULIS. In addition, we found OP_AA and OP_•OH are well-correlated while the proportion of OP_•OH/OP_AA by Cu is noticeably lower than that by Fe, indicating varying sensitivity of the metals to different OP end points. Our work highlights the importance and complexity of metal-organics interactions and the advantages of comeasurements of ROS generation and antioxidant depletion when assessing oxidative stress elicited by atmospheric PM.

Effect of metal-organic interactions on the oxidative potential of mixtures of atmospheric humic-like substances and copper/manganese as investigated by the dithiothreitol assay

Excessive generation of reactive oxygen species (ROS) and the corresponding oxidative stress has been recognized as one important cause for the adverse health effects associated with exposure to ambient particulate matter (PM). Transition metals and humic-like substances (HULIS) in PM have been separately demonstrated to contribute to the oxidative potential (OP) of PM, however, only few studies investigated the impact of their interactions on the measured OP and the effect is little understood. HULIS is an abundant fraction of water-soluble organic material in PM and serves to represent real-world PM organics. In this study, we applied a cell-free dithiothreitol (DTT) assay to quantify the OP, termed as OP_DTT, by two representative transition metals (i.e., copper (Cu) and manganese (Mn)), HULIS, and mixtures of HULIS and metals in concentration levels relevant to those in human lung fluid resulting from PM inhalation. The organic-metal mixture effect was found to be metal-specific and concentration-specific, covering the possibility spectrum from being synergistic, additive to antagonistic. HULIS was observed to suppress OP_DTT up to 10-20% by Cu at a concentration of 0.08 μM while had no discernable effect at 0.5 μM Cu. On the contrary, obvious enhancement of OP_DTT was recorded in the mixtures of HULIS and Mn (e.g. up to ~2 times at 2.5 μM of Mn) while no mixture effects could be discerned at 0.5 μM Mn. Our work demonstrates the need for considering the metal-organic interactions and the complexity when evaluating the total OP of their mixtures, such as ambient PM samples. Further work in metal-PM organics interactions should be conducted using methods capable of measuring specific oxidants, in addition to the ability to deplete the reducing agent (i.e., DTT), in order to acquire a deeper mechanistic insight into the interactions.

Influence of industrial contamination in municipal secondary effluent disinfection by UV/H2O2

Advanced oxidation processes, including UV/H₂O₂, are methods able to remove diverse classes of organic contaminants and disinfect water and wastewater. However, the variation in the matrix composition can influence the inactivation of microorganisms due to the presence of competing reactive material, which consumes the available oxidants. This problem can lead to the use of inadequate oxidant/radiation dose and disturb a correct treatment. The aim of this study was to assess the efficiency of UV/H₂O₂ to inactivate microbiological indicators in secondary effluents in the presence of high concentration of carbonate, nitrate, metals, and industrial organic contaminants. Metals had a positive influence on inactivation acting as catalysts. Zn, Fe, and all metals simultaneously presented toxic effects to the indicator organisms in the higher concentrations before the treatment. Even in metals presence, the negative effect of carbonate and the industrial organic contaminants on indicators inactivation was very important. Bacteria regrowth after 72 h was also affected by the same inhibiting substances, but the metals acted positively inhibiting it. The disinfection indicators had different sensibilities to the spiked substances. Escherichia coli inactivation was more affected than total coliforms by the presence of the industrial contamination, which can lead to different interpretation of inhibition degree depending of the used disinfection indicator.

Occupational exposure to inorganic particles during pregnancy and birth outcomes: a nationwide cohort study in Sweden

OBJECTIVES

The aim of this study was to investigate if occupational exposure to inorganic particles or welding fumes during pregnancy is associated with negative birth outcomes.

DESIGN

A prospective national cohort study.

SETTING

All single births from 1994 to 2012 in Sweden. Information on birth weight, preterm birth, small for gestational age, smoking habits, nationality, age, occupation, absence from work and education was obtained from nationwide registers. Exposure to inorganic particles (mg/m³) was assessed from a job exposure matrix.

PARTICIPANTS

This study included all single births by occupationally active mothers (995 843).

OUTCOME MEASURES

Associations between occupational exposures and negative birth outcomes in the form of low birth weight, preterm birth and small for gestational age.

RESULTS

Mothers who had high exposure to inorganic particles and had less than 50 days (median) of absence from work during pregnancy showed an increased risk of preterm birth (OR 1.18; 95% CI 1.07 to 1.30), low birth weight (OR 1.32; 95% CI 1.18 to 1.48) as well as small for gestational age (OR 1.20; 95% CI 1.04 to 1.39). The increased risks were driven by exposure to iron particles. No increased risks were found in association with exposure to stone and concrete particles. High exposure to welding fumes was associated with an increased risk of low birth weight (OR 1.22; 95% CI 1.02 to 1.45) and preterm birth (OR 1.24; 95% CI 1.07 to 1.42).

CONCLUSIONS

The results indicate that pregnant women should not be exposed to high levels of iron particles or welding fumes.

Properties of Zinc Oxide Nanoparticles and Their Activity Against Microbes

Zinc oxide is an essential ingredient of many enzymes, sun screens, and ointments for pain and itch relief. Its microcrystals are very efficient light absorbers in the UVA and UVB region of spectra due to wide bandgap. Impact of zinc oxide on biological functions depends on its morphology, particle size, exposure time, concentration, pH, and biocompatibility. They are more effective against microorganisms such as Bacillus subtilis, Bacillus megaterium, Staphylococcus aureus, Sarcina lutea, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumonia, Pseudomonas vulgaris, Candida albicans, and Aspergillus niger. Mechanism of action has been ascribed to the activation of zinc oxide nanoparticles by light, which penetrate the bacterial cell wall via diffusion. It has been confirmed from SEM and TEM images of the bacterial cells that zinc oxide nanoparticles disintegrate the cell membrane and accumulate in the cytoplasm where they interact with biomolecules causing cell apoptosis leading to cell death.

Reduction reactions and densification during in situ TEM heating of iron oxide nanochains

The reduction reactions and densification of nanochains assembled from γ-Fe₂O₃ nanoparticles were investigated using in situ transmission electron microscopy (TEM). Morphological changes and reduction of the metal oxide nanochains were observed during in situ TEM annealing through simultaneous imaging and quantitative analysis of the near-edge fine structures of Fe L_2,3 absorption edges acquired by spatially resolved electron energy loss spectroscopy. A change in the oxidation states during annealing of the iron oxide nanochains was observed with phase transformations due to continuous reduction from Fe₂O₃ over Fe₃O₄, FeO to metallic Fe. Phase transitions during the in situ heating experiments were accompanied with morphological changes in the nanochains, specifically rough-to-smooth surface transitions below 500 °C, neck formation between adjacent particles around 500 °C, and subsequent neck growth. At higher temperatures, coalescence of FeO particles was observed, representing densification.

Repeated Iron-Soot Exposure and Nose-to-brain Transport of Inhaled Ultrafine Particles

Particulate exposure has been implicated in the development of a number of neurological maladies such as multiple sclerosis, amyotrophic lateral sclerosis, Alzheimer's disease, and idiopathic Parkinson's disease. Only a few studies have focused on the olfactory pathway as a portal through which combustion-generated particles may enter the brain. The primary objective of this study was to define the deposition, uptake, and transport of inhaled ultrafine iron-soot particles in the nasal cavities of mice to determine whether combustion-generated nanoparticles reach the olfactory bulb via the olfactory epithelium and nerve fascicles. Adult female C57B6 mice were exposed to iron-soot combustion particles at a concentration of 200 μg/m³, which included 40 μg/m³ of iron oxide nanoparticles. Mice were exposed for 6 hr/day, 5 days/week for 5 consecutive weeks (25 total exposure days). Our findings visually demonstrate that inhaled ultrafine iron-soot reached the brain via the olfactory nerves and was associated with indicators of neural inflammation.

Association of indoor air pollution from coal combustion with influenza-like illness in housewives

An association of influenza-like illness (ILI) with outdoor air pollution has been reported. However, the effect of indoor air pollution on ILI was rarely investigated. We aimed to determine an association of indoor air pollution from coal combustion (IAPCC) and lifestyle with ILI risk in housewives, and the modification effect of phase II metabolic enzyme genes. We recruited 403 housewives for a cross-sectional study in Shanxi Province, China, including 135 with ILI frequency (≥1 time per year in the past ten years) as the case group and 268 with ILI frequency (<1 times per year) as the control group. Information on their energy usage characteristics and lifestyle was collected by questionnaires, as well as the single nucleotide polymorphisms (SNPs) of epoxide hydrolase 1 (rs1051740 and rs2234922), N-acetyltransferase 2 (rs1041983), and glutathione S-transferase (rs1695). We used exposure index to indicate the level of IAPCC among housewives. Our results revealed that the exposure index was positively correlated with ILI frequency. A significant dose-response trend between the exposure index and ILI risk was found with or without adjusting for confounders. Cooking frequency in kitchen with coal as primary fuel and ventilation frequency in the living room or bedroom with a coal-fueled stove for heating during the heating season were two important risk factors to affect ILI frequency. Only rs1051740 was found to be associated with exposure index, whereas it didn't have interaction effect with exposure index on ILI frequency. In conclusion, IAPCC and SNPs of rs1051740 were both associated with ILI frequency.

Particulate matter properties and health effects: consistency of epidemiological and toxicological studies

Identifying the ambient particulate matter (PM) fractions or constituents, critically involved in eliciting adverse health effects, is crucial to the implementation of more cost-efficient abatement strategies to improve air quality. This review focuses on the importance of different particle properties for PM-induced effects, and whether there is consistency in the results from epidemiological and experimental studies. An evident problem for such comparisons is that epidemiological and experimental data on the effects of specific components of ambient PM are limited. Despite this, some conclusions can be drawn. With respect to the importance of the PM size-fractions, experimental and epidemiological studies are somewhat conflicting, but there seems to be a certain consistency in that the coarse fraction (PM10-2.5) has an effect that should not be neglected. Better exposure characterization may improve the consistency between the results from experimental and epidemiological studies, in particular for ultrafine particles. Experimental data indicate that surface area is an important metric, but composition may play an even greater role in eliciting effects. The consistency between epidemiological and experimental findings for specific PM-components appears most convincing for metals, which seem to be important for the development of both pulmonary and cardiovascular disease. Metals may also be involved in PM-induced allergic sensitization, but the epidemiological evidence for this is scarce. Soluble organic compounds appear to be implicated in PM-induced allergy and cancer, but the data from epidemiological studies are insufficient for any conclusions. The present review suggests that there may be a need for improvements in research designs. In particular, there is a need for better exposure assessments in epidemiological investigations, whereas experimental data would benefit from an improved comparability of studies. Combined experimental and epidemiological investigations may also help answer some of the unresolved issues.

High dispersity of carbon nanotubes diminishes immunotoxicity in spleen

BACKGROUND

From the various physiochemical material properties, the chemical functionalization order of single-walled carbon nanotubes (swCNTs) has not been considered as a critical factor for modulating immunological responses and toxicological aspects in drug delivery applications. Although most nanomaterials, including carbon nanotubes, are specifically accumulated in spleen, few studies have focused on spleen immunotoxicity. For this reason, this study demonstrated that the dispersity of swCNTs significantly influenced immunotoxicity in vitro and in vivo.

MATERIALS AND METHODS

For cytotoxicity of swCNTs, MTT assay, reactive oxygen species production, superoxide dismutase activity, cellular uptake, and confocal microscopy were used in macrophages. In the in vivo study, female BALB/c mice were intravenously administered with 1 mg/kg/day of swCNTs for 2 weeks. The body weight, organ weight, hematological change, reverse-transcription polymerase chain reaction, and lymphocyte population were evaluated.

RESULTS

Different orders of chemical functionalization of swCNTs controlled immunotoxicity. In short, less-dispersed swCNTs caused cytotoxicity in macrophages and abnormalities in immune organs such as spleen, whereas highly dispersed swCNTs did not result in immunotoxicity.

CONCLUSION

This study clarified that increasing carboxyl groups on swCNTs significantly mitigated immunotoxicity in vitro and in vivo. Our findings clarified the effective immunotoxicological factors of swCNTs by increasing dispersity of swCNTs and provided useful guidelines for the effective use of nanomaterials.

Toxicology of ambient particulate matter

It is becoming increasingly clear that inhalation exposure to particulate matter (PM) can lead to or exacerbate various diseases, which are not limited to the lung but extend to the cardiovascular system and possibly other organs and tissues. Epidemiological studies have provided strong evidence for associations with chronic obstructive pulmonary disease (COPD), asthma, bronchitis and cardiovascular disease, while the evidence for a link with lung cancer is less strong. Novel research has provided first hints that exposure to PM might lead to diabetes and central nervous system (CNS) pathology. In the current review, an overview is presented of the toxicological basis for adverse health effects that have been linked to PM inhalation. Oxidative stress and inflammation are discussed as central processes driving adverse effects; in addition, profibrotic and allergic processes are implicated in PM-related diseases. Effects of PM on key cell types considered as regulators of inflammatory, fibrotic and allergic mechanisms are described.

The concentration of iron in real-world geogenic PM₁₀ is associated with increased inflammation and deficits in lung function in mice

Background

There are many communities around the world that are exposed to high levels of particulate matter <10 µm (PM₁₀) of geogenic (earth derived) origin. Mineral dusts in the occupational setting are associated with poor lung health, however very little is known about the impact of heterogeneous community derived particles. We have preliminary evidence to suggest that the concentration of iron (Fe) may be associated with the lung inflammatory response to geogenic PM₁₀. We aimed to determine which physico-chemical characteristics of community sampled geogenic PM₁₀ are associated with adverse lung responses.

Methods

We collected geogenic PM₁₀ from four towns in the arid regions of Western Australia. Adult female BALB/c mice were exposed to 100 µg of particles and assessed for inflammatory and lung function responses 6 hours, 24 hours and 7 days post-exposure. We assessed the physico-chemical characteristics of the particles and correlated these with lung outcomes in the mice using principal components analysis and multivariate linear regression.

Results

Geogenic particles induced an acute inflammatory response that peaked 6 hours post-exposure and a deficit in lung mechanics 7 days post-exposure. This deficit in lung mechanics was positively associated with the concentration of Fe and particle size variability and inversely associated with the concentration of Si.

Conclusions

The lung response to geogenic PM₁₀ is complex and highly dependent on the physico-chemical characteristics of the particles. In particular, the concentration of Fe in the particles may be a key indicator of the potential population health consequences for inhaling geogenic PM₁₀.

Nanoparticles, lung injury, and the role of oxidant stress

The emergence of engineered nanoscale materials has provided significant advancements in electronic, biomedical, and material science applications. Both engineered nanoparticles and nanoparticles derived from combustion or incidental processes exhibit a range of physical and chemical properties that induce inflammation and oxidative stress in biological systems. Oxidative stress reflects the imbalance between the generation of reactive oxygen species and the biochemical mechanisms to detoxify and repair the damage resulting from reactive intermediates. This review examines current research on incidental and engineered nanoparticles in terms of their health effects on lungs and the mechanisms by which oxidative stress via physicochemical characteristics influences toxicity or biocompatibility. Although oxidative stress has generally been thought of as an adverse biological outcome, this review also briefly discusses some of the potential emerging technologies to use nanoparticle-induced oxidative stress to treat disease in a site-specific fashion.

Pulmonary oxidative stress, inflammation and cancer: respirable particulate matter, fibrous dusts and ozone as major causes of lung carcinogenesis through reactive oxygen species mechanisms

Reactive oxygen or nitrogen species (ROS, RNS) and oxidative stress in the respiratory system increase the production of mediators of pulmonary inflammation and initiate or promote mechanisms of carcinogenesis. The lungs are exposed daily to oxidants generated either endogenously or exogenously (air pollutants, cigarette smoke, etc.). Cells in aerobic organisms are protected against oxidative damage by enzymatic and non-enzymatic antioxidant systems. Recent epidemiologic investigations have shown associations between increased incidence of respiratory diseases and lung cancer from exposure to low levels of various forms of respirable fibers and particulate matter (PM), at occupational or urban air polluting environments. Lung cancer increases substantially for tobacco smokers due to the synergistic effects in the generation of ROS, leading to oxidative stress and inflammation with high DNA damage potential. Physical and chemical characteristics of particles (size, transition metal content, speciation, stable free radicals, etc.) play an important role in oxidative stress. In turn, oxidative stress initiates the synthesis of mediators of pulmonary inflammation in lung epithelial cells and initiation of carcinogenic mechanisms. Inhalable quartz, metal powders, mineral asbestos fibers, ozone, soot from gasoline and diesel engines, tobacco smoke and PM from ambient air pollution (PM₁₀ and PM₂.₅) are involved in various oxidative stress mechanisms. Pulmonary cancer initiation and promotion has been linked to a series of biochemical pathways of oxidative stress, DNA oxidative damage, macrophage stimulation, telomere shortening, modulation of gene expression and activation of transcription factors with important role in carcinogenesis. In this review we are presenting the role of ROS and oxidative stress in the production of mediators of pulmonary inflammation and mechanisms of carcinogenesis.

Nanosized zinc oxide induces toxicity in human lung cells

Zinc oxide nanoparticles (ZnO-NPs) are increasingly used in sunscreens, biosensors, food additives, pigments, rubber manufacture, and electronic materials. With the wide application of ZnO-NPs, concern has been raised about its unintentional health and environmental impacts. This study investigates the toxic effects of ZnO-NPs in human lung cells. In order to assess toxicity, human lung epithelial cells (L-132) were exposed to dispersion of 50 nm ZnO-NPs at concentrations of 5, 25, 50, and 100  μ g/mL for 24 h. The toxicity was evaluated by observing changes in cell morphology, cell viability, oxidative stress parameters, DNA damage analysis, and gene expression. Exposure to 50 nm ZnO-NPs at concentrations between 5 and 100  μ g/mL decreased cell viability in a concentration-dependent manner. Morphological examination revealed cell shrinkage, nuclear condensation, and formation of apoptotic bodies. The oxidative stress parameters revealed significant depletion of GSH level and increase in ROS levels suggesting generation of oxidative stress. ZnO-NPs exposure caused DNA fragmentation demonstrating apoptotic type of cell death. ZnO-NPs increased the expression of metallothionein gene, which is considered as a biomarker in metal-induced toxicity. To summarize, ZnO-NPs cause toxicity in human lung cells possibly through oxidative stress-induced apoptosis.

Exposure to ambient ultrafine particles and urinary 8-hydroxyl-2-deoxyguanosine in children with and without eczema

Ambient fine and ultrafine particles (UFPs) in urban air are known to contribute to inflammatory and allergic disease. It has been suggested that oxidative stress is an underlying mechanism for the detrimental health effects. The objective of this study was to investigate the short-term effect of ambient UFPs and particulate polycyclic aromatic hydrocarbons (PAHs) on urinary 8-hydroxyl-2-deoxyguanosine (8-OHdG) concentrations in children with and without eczema. Spot urine samples were collected from 84 children twice weekly for 61 days and 8-OHdG content was measured. Significant associations were found between the ambient UFPs and particle bound PAHs and increase in urinary 8-OHdG levels. An inter-quartile range (IQR) increase in the UFP concentration in the 24-h (IQR, 32,300/m(3)) period preceding urine collection was significantly associated with a 5.7% (95% confidence interval [CI], 0.16-1.27%) increase in the urinary 8-OHdG level children with AD. In children without eczema, such short-term effect of previous day UFPs on urinary 8-OHdG was not observed. There were no significant positive associations between the mass fraction of PMs and urinary 8-OHdG. The results suggest that short-term exposure to ambient UFPs plays a critical role in PM induced oxidative stress in children with eczema.

Air quality impact and physicochemical aging of biomass burning aerosols during the 2007 San Diego wildfires

Intense wildfires burning >360000 acres in San Diego during October, 2007 provided a unique opportunity to study the impact of wildfires on local air quality and biomass burning aerosol (BBA) aging. The size-resolved mixing state of individual particles was measured in real-time with an aerosol time-of-flight mass spectrometer (ATOFMS) for 10 days after the fires commenced. Particle concentrations were high county-wide due to the wildfires; 84% of 120-400 nm particles by number were identified as BBA, with particles <400 nm contributing to mass concentrations dangerous to public health, up to 148 μg/m(3). Evidence of potassium salts heterogeneously reacting with inorganic acids was observed with continuous high temporal resolution for the first time. Ten distinct chemical types shown as BBA factors were identified through positive matrix factorization coupled to single particle analysis, including particles comprised of potassium chloride and organic nitrogen during the beginning of the wildfires, ammonium nitrate and amines after an increase of relative humidity, and sulfate dominated when the air mass back trajectories passed through the Los Angeles port region. Understanding BBA aging processes and quantifying the size-resolved mass and number concentrations are important in determining the overall impact of wildfires on air quality, health, and climate.

Stimulation of production of reactive oxygen and nitrogen species in endothelial cells by unmodified and Fenton-modified ultradisperse detonation diamond

In recent years, the development of nanotechnology opens up new prospects for biomedical applications of unmodified and chemically modified diamond nanoparticles (DNPs). The problem of biocompatibility of DNPs is thus of primary importance. The first step in the modification of DNPs is usually the introduction of -OH groups, which can bind other functional groups. One of the basic methods to introduce -OH groups onto DNPs is the Fenton reaction. The aim of this study was to compare the effect of unmodified DNPs and nanoparticles modified by the Fenton reaction on human endothelial cells. Ultradisperse diamond (UDD) was modified by the Fenton reaction introducing surface -OH groups. Immortalized human umbilical cord endothelial cells (HUVEC-ST) were incubated with 2-100 µg/mL nanopowders in the opti-MEM medium. For comparison, graphite powder (GRAF and GRAF+OH) was also employed. UDD and GRAF augmented generation of reactive oxygen species in the cells after 24 H incubation, estimated by oxidation of 2',7'-dichlorofluorescin diacetate (H2DCF-DA). Cellular production of nitric oxide, estimated with DAF-FM-DA (3-amino-4-aminomethyl 2',7'-dichlorofluorescein diacetate), was also affected by UDD and GRAF after 24 H. Fenton-modified OH, in contrast to unmodified diamond, decreased NO production. Detonation nanoparticles also affected the cellular content of glutathione and activities of main antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and glutathione S-transferase). This article was published online on 5 February 2013. Errors in the byline and affiliation line were subsequently identified. This notice is included in the online and print versions to indicate that both have been corrected 18 April 2013.

Comparative study of genotoxicity and tissue distribution of nano and micron sized iron oxide in rats after acute oral treatment

Though nanomaterials (NMs) are being utilized worldwide, increasing use of NMs have raised concerns over their safety to human health and environment. Iron oxide (Fe(2)O(3)) NMs have important applications. The aim of this study was to assess the genotoxicity of Fe(2)O(3)-30nm and Fe(2)O(3)-bulk in female Wistar rats. Fe(2)O(3)-30nm was characterized by using transmission electron microscopy, dynamic light scattering, laser Doppler velocimetry and surface area analysis. The rats were treated orally with the single doses of 500, 1000, 2000mg/kg bw of Fe(2)O(3)-30nm and Fe(2)O(3) -bulk. The genotoxicity was evaluated at 6, 24, 48 and 72h by the comet assay in leucocytes, 48 and 72h by micronucleus test (MNT) in peripheral blood cells, 18 and 24h by chromosomal aberration (CA) assay and 24 and 48h by MNT in bone marrow cells. The biodistribution of iron (Fe) was carried out at 6, 24, 48 and 72h after treatment in liver, spleen, kidney, heart, brain, bone marrow, urine and feces by using atomic absorption spectrophotometry. The % tail DNA, frequencies of micronuclei and CAs were statistically insignificant (p>0.05) at all doses. These results suggest that Fe(2)O(3)-30nm and Fe(2)O(3)-bulk was not genotoxic at the doses tested. Bioavailability of Fe was size and dose dependent in all the tissues from the groups exposed to Fe(2)O(3)-30nm. Fe(2)O(3) NMs were able to enter in the organs and the rats are biocompatible with much higher concentration of Fe. However, the accumulated Fe did not cause significant genotoxicity. This study provides additional knowledge about the toxicology of Fe(2)O(3) NMs.

Exposure and emissions monitoring during carbon nanofiber production--Part I: elemental carbon and iron-soot aerosols

Production of carbon nanofibers and nanotubes (CNFs/CNTs) and their composite products is increasing globally. High volume production may increase the exposure risks for workers who handle these materials. Though health effects data for CNFs/CNTs are limited, some studies raise serious health concerns. Given the uncertainty about their potential hazards, there is an immediate need for toxicity data and field studies to assess exposure to CNFs/CNTs. An extensive study was conducted at a facility that manufactures and processes CNFs. Filter, sorbent, cascade impactor, bulk, and microscopy samples, combined with direct-reading instruments, provided complementary information on air contaminants. Samples were analyzed for organic carbon (OC) and elemental carbon (EC), metals, and polycyclic aromatic hydrocarbons (PAHs), with EC as a measure of CNFs. Transmission electron microscopy with energy-dispersive X-ray spectroscopy also was applied. Fine/ultrafine iron-rich soot, PAHs, and carbon monoxide were production byproducts. Direct-reading instrument results were reported previously [Evans DE et al. (Aerosol monitoring during carbon nanofiber production: mobile direct-reading sampling. Ann Occup Hyg 2010;54:514-31.)] Results for time-integrated samples are reported as companion papers in this Issue. OC and EC, metals, and microscopy results are reported here, in Part I, while results for PAHs are reported in Part II [Birch ME. (Exposure and Emissions Monitoring during Carbon Nanofiber Production-Part II: Polycyclic Aromatic Hydrocarbons. Ann. Occup. Hyg 2011; 55: 1037-47.)]. Respirable EC area concentrations inside the facility were about 6-68 times higher than outdoors, while personal breathing zone samples were up to 170 times higher.

The innate and adaptive immune response induced by alveolar macrophages exposed to ambient particulate matter

Emerging epidemiological evidence suggests that exposure to particulate matter (PM) air pollution increases the risk of cardiovascular events but the exact mechanism by which PM has adverse effects is still unclear. Alveolar macrophages (AM) play a major role in clearing and processing inhaled PM. This comprehensive review of research findings on immunological interactions between AM and PM provides potential pathophysiological pathways that interconnect PM exposure with adverse cardiovascular effects. Coarse particles (10 μm or less, PM(10)) induce innate immune responses via endotoxin-toll-like receptor (TLR) 4 pathway while fine (2.5 μm or less, PM(2.5)) and ultrafine particles (0.1 μm or less, UFP) induce via reactive oxygen species generation by transition metals and/or polyaromatic hydrocarbons. The innate immune responses are characterized by activation of transcription factors [nuclear factor (NF)-κB and activator protein-1] and the downstream proinflammatory cytokine [interleukin (IL)-1β, IL-6, and tumor necrosis factor-α] production. In addition to the conventional opsonin-dependent phagocytosis by AM, PM can also be endocytosed by an opsonin-independent pathway via scavenger receptors. Activation of scavenger receptors negatively regulates the TLR4-NF-κB pathway. Internalized particles are subsequently subjected to adaptive immunity involving major histocompatibility complex class II (MHC II) expression, recruitment of costimulatory molecules, and the modulation of the T helper (Th) responses. AM show atypical antigen presenting cell maturation in which phagocytic activity decreases while both MHC II and costimulatory molecules remain unaltered. PM drives AM towards a Th1 profile but secondary responses in a Th1- or Th-2 up-regulated milieu drive the response in favor of a Th2 profile.

Age specific responses to acute inhalation of diffusion flame soot particles: cellular injury and the airway antioxidant response

Current studies of particulate matter (PM) are confounded by the fact that PM is a complex mixture of primary (crustal material, soot, metals) and secondary (nitrates, sulfates, and organics formed in the atmosphere) compounds with considerable variance in composition by sources and location. We have developed a laboratory-based PM that is replicable, does not contain dust or metals and that can be used to study specific health effects of PM composition in animal models. We exposed both neonatal (7 days of age) and adult rats to a single 6-h exposure of laboratory generated fine diffusion flame particles (DFP; 170 µg/m(3)), or filtered air. Pulmonary gene and protein expression as well as indicators of cytotoxicity were evaluated 24 h after exposure. Although DFP exposure did not alter airway epithelial cell composition in either neonates or adults, increased lactate dehydrogenase activity was found in the bronchoalveolar lavage fluid of neonates indicating an age-specific increase in susceptibility. In adults, 16 genes were differentially expressed as a result of DFP exposure whereas only 6 genes were altered in the airways of neonates. Glutamate cysteine ligase protein was increased in abundance in both DFP exposed neonates and adults indicating an initiation of antioxidant responses involving the synthesis of glutathione. DFP significantly decreased catalase gene expression in adult airways, although catalase protein expression was increased by DFP in both neonates and adults. We conclude that key airway antioxidant enzymes undergo changes in expression in response to a moderate PM exposure that does not cause frank epithelial injury and that neonates have a different response pattern than adults.

Nanomaterial cytotoxicity is composition, size, and cell type dependent

Background

Despite intensive research efforts, reports of cellular responses to nanomaterials are often inconsistent and even contradictory. Additionally, relationships between the responding cell type and nanomaterial properties are not well understood. Using three model cell lines representing different physiological compartments and nanomaterials of different compositions and sizes, we have systematically investigated the influence of nanomaterial properties on the degrees and pathways of cytotoxicity. In this study, we selected nanomaterials of different compositions (TiO₂ and SiO₂ nanoparticles, and multi-wall carbon nanotubes [MWCNTs]) with differing size (MWCNTs of different diameters < 8 nm, 20-30 nm, > 50 nm; but same length 0.5-2 μm) to analyze the effects of composition and size on toxicity to 3T3 fibroblasts, RAW 264.7 macrophages, and telomerase-immortalized (hT) bronchiolar epithelial cells.

Results

Following characterization of nanomaterial properties in PBS and serum containing solutions, cells were exposed to nanomaterials of differing compositions and sizes, with cytotoxicity monitored through reduction in mitochondrial activity. In addition to cytotoxicity, the cellular response to nanomaterials was characterized by quantifying generation of reactive oxygen species, lysosomal membrane destabilization and mitochondrial permeability. The effect of these responses on cellular fate - apoptosis or necrosis - was then analyzed. Nanomaterial toxicity was variable based on exposed cell type and dependent on nanomaterial composition and size. In addition, nanomaterial exposure led to cell type dependent intracellular responses resulting in unique breakdown of cellular functions for each nanomaterial: cell combination.

Conclusions

Nanomaterials induce cell specific responses resulting in variable toxicity and subsequent cell fate based on the type of exposed cell. Our results indicate that the composition and size of nanomaterials as well as the target cell type are critical determinants of intracellular responses, degree of cytotoxicity and potential mechanisms of toxicity.

Synergistic genotoxicity caused by low concentration of titanium dioxide nanoparticles and p,p'-DDT in human hepatocytes

The use of titanium dioxide nanoparticles (nano-TiO(2)) for the degradation of dichlorodiphenyltrichloroethane (p,p'-DDT) increases the risk of exposure to trace nano-TiO(2) and p,p'-DDT mixtures. The interaction of p,p'-DDT and nano-TiO(2) at low concentrations may alter toxic response relative to nano-TiO(2) or p,p'-DDT alone. In this work, the combined genotoxicity of trace nano-TiO(2) and p,p'-DDT on human embryo L-02 hepatocytes without photoactivation was studied. Nano-TiO(2) (0.1 g/L) was mixed with 0.01-1 mmol/L p,p'-DDT to determine adsorption isotherms. L-02 cells were exposed to different levels of p,p'-DDT (0, 0.001, 0.01, and 0.1 mumol/L) and nano-TiO(2) (0, 0.01, 0.1, and 1 microg/mL) respectively. The adsorption of p,p'-DDT by nano-TiO(2) was approximately 0.3 mmol/g. Cell viability, apoptosis, and DNA double strand breaks were similar among all test groups. Nano-TiO(2) alone (0.01-1 microg/mL) increased the levels of oxidative stress and oxidative DNA adducts (8-OHdG), but it did not induce DNA breaks or chromosome damage. Addition of trace nano-TiO(2) with trace p,p'-DDT synergistically enhanced genotoxicity via increasing oxidative stress, oxidative DNA adducts, DNA breaks, and chromosome damage in L-02 cells. Low concentrations of nano-TiO(2) and p,p'-DDT increased oxidativestress by reactive oxygen species (ROS) formation and lipid oxidation. Oxidative stress is a major pathway for DNA and chromosome damage. Dose-dependent synergistic genotoxicity induced by combined exposure of trace p,p'-DDT and nano-TiO(2) suggests a potential environmental risk of nano-TiO(2) assisted photocatalysis.

Effects of titanium dioxide nanoparticle exposure on neuroimmune responses in rat airways

Exposure to ambient nanoparticles (defined as particulate matter [PM] having one dimension <100 nm) is associated with increased risk of childhood and adult asthma. Nanomaterials feature a smaller aerodynamic diameter and a higher surface area per unit mass ratio compared to fine or coarse-sized particles, resulting in greater lung deposition efficiency and an increased potential for biological interaction. The neurotrophins nerve growth factor and brain-derived neurotrophic factor are key regulatory elements of neuronal development and responsiveness of airway sensory neurons. Changes in their expression are associated with bronchoconstriction, airway hyperresponsiveness, and airway inflammation. The neurogenic-mediated control of airway responses is a key pathophysiological mechanism of childhood asthma. However, the effects of nanoparticle exposure on neurotrophin-driven airway responses and their potential role as a predisposing factor for developing asthma have not been clearly elucidated. In this study, in vivo inhalation exposure to titanium dioxide nanoparticles (12 mg/m(3); 5.6 h/d for 3 d) produced upregulation of lung neurotrophins in weanling (2-wk-old) and newborn (2-d-old) rats but not in adult (12-wk-old) animals compared to controls. This effect was associated with increased airway responsiveness and upregulation of growth-related oncogene/keratine-derived chemokine (GRO/KC; CXCL1, rat equivalent of human interleukin [IL]-8) in bronchoalveolar lavage fluid. These data show for the first time that exposure to nanoparticulate upregulates the expression of lung neurotrophins in an age-dependent fashion and that this effect is associated with airway hyperresponsiveness and inflammation. These results suggest the presence of a critical window of vulnerability in earlier stages of lung development, which may lead to a higher risk of developing asthma.

Oxidative injury in the lungs of neonatal rats following short-term exposure to ultrafine iron and soot particles

Greater risk of adverse effects from particulate matter (PM) has been noted in susceptible subpopulations, such as children. However, the physicochemical components responsible for these biological effects are not understood. As critical constituents of PM, transition metals were postulated to be involved in a number of pathological processes of the respiratory system through free radical-medicated damage. The purpose of this study was to examine whether oxidative injury in the lungs of neonatal rats could be induced by repeated short-term exposure to iron (Fe) and soot particles. Sprague Dawley rats 10 d of age were exposed by inhalation to two different concentrations of ultrafine iron particles (30 or 100 microg/m(3)) in combination with soot particles adjusted to maintain a total particle concentration of 250 microg/m(3). Exposure at 10 d and again at 23 d of age was for 6 h/d for 3 d. Oxidative stress was observed at both Fe concentrations in the form of significant elevations in glutathione disulfide (GSSG) and GSSG/glutathione (GSH) ratio and a reduction in ferric/reducing antioxidant power in bronchoalveolar lavage. A significant decrease in cell viability associated with significant increases in lactate dehydrogenase (LDH) activity, interleukin-1-beta (IL-1beta), and ferritin expression was noted following exposure to particles containing the highest Fe concentration. Iron from these particles was shown to be bioavailable in an in vitro assay using the physiologically relevant chelator, citrate. Data indicate that combined Fe and soot particle exposure induces oxidative injury, cytotoxicity and pro-inflammatory responses in the lungs of neonatal rats.

Central neuroplasticity and decreased heart rate variability after particulate matter exposure in mice

BACKGROUND

Epidemiologic studies show that exposure to fine particulate matter [aerodynamic diameter < or = 2.5 microm (PM(2.5))] increases the total daily cardiovascular mortality. Impaired cardiac autonomic function, which manifests as reduced heart rate variability (HRV), may be one of the underlying causes. However, the cellular mechanism(s) by which PM(2.5) exposure induces decreased HRV is not known.

OBJECTIVES

We tested the hypothesis that exposure to PM(2.5) impairs HRV by decreasing the excitability of the cardiac vagal neurons in the nucleus ambiguus. We also determined the effect of iron on PM-exposure-induced decrease in HRV.

METHODS

We measured 24-hr HRV in time domains from electrocardiogram telemetry recordings obtained in conscious, freely moving mice after 3 days of exposure to PM(2.5) in the form of soot only or iron-soot. In parallel studies, we determined the intrinsic properties of identified cardiac vagal neurons, retrogradely labeled with a fluorescent dye applied to the sinoatrial node.

RESULTS

Soot-only exposure decreased short-term HRV (root mean square of successive difference). With the addition of iron, all HRV parameters were significantly reduced. In nonexposed mice, vagal blockade significantly reduced all HRV parameters, suggesting that HRV is, in part, under vagal regulation in mice. Iron-soot exposure had no significant effect on resting membrane potential but decreased spiking responses of the identified cardiac vagal neurons to depolarizations (p < 0.05). The decreased spiking response was accompanied with a higher minimal depolarizing current required to evoke spikes and a lower peak discharge frequency.

CONCLUSIONS

The data suggest that PM-induced neuroplasticity of cardiac vagal neurons may be one mechanism contributing to the cardiovascular consequences associated with PM(2.5) exposure seen in humans.

Impact of emissions from the Los Angeles port region on San Diego air quality during regional transport events

Oceangoing ships emit an estimated 1.2-1.6 million metric tons (Tg) of PM10 per year and represent a significant source of air pollution to coastal communities. As shown herein, ship and other emissions near the Los Angeles and Long Beach Port region strongly influence air pollution levels in the San Diego area. During time periods with regional transport, atmospheric aerosol measurements in La Jolla, California show an increase in 0.5-1 microm sized single particles with unique signatures including soot, metals (i.e., vanadium, iron, and nickel), sulfate, and nitrate. These particles are attributed to primary emissions from residual oil sourcessuch as ships and refineries, as well as traffic in the port region, and secondary processing during transport. During regional transport events, particulate matter concentrations were 2-4 times higher than typical average concentrations from local sources, indicating the health, environmental, and climate impacts from these emission sources must be taken into consideration in the San Diego region. Unless significant regulations are imposed on shipping-related activities, these emission sources will become even more important to California air quality as cars and truck emissions undergo further regulations and residual oil sources such as shipping continue to expand.

Synergistic effect of co-exposure to carbon black and Fe2O3 nanoparticles on oxidative stress in cultured lung epithelial cells

Background

There is a need to better understand synergism in the biological effects of particles composed of multiple substances. The objective of this study was to determine if the oxidative stress in cultured cells caused by co-exposure to carbon black and Fe₂O₃ nanoparticles was significantly greater than the additive effects of exposure to either type of particles alone; and to determine a possible cause for such synergistic effect if one was found. Cultured A549 human lung epithelial cells were exposed to (1) carbon black nanoparticles alone, (2) Fe₂O₃ nanoparticles alone, and (3) both types of particles simultaneously. Protein oxidation, lipid peroxidation, and cellular uptake of Fe in these cells were measured after 25 hours of exposure. The reduction of solubilized Fe³⁺ by the carbon black nanoparticles was measured separately in a cell-free assay, by incubating the carbon black and the Fe₂O₃ nanoparticles in 0.75 M sulfuric acid at 40°C and measuring the amount of reduced Fe³⁺ at different time points up to 24 hours.

Results

Cells exposed to carbon black particles alone did not show protein oxidation, nor did the cells exposed to Fe₂O₃ particles alone, relative to the control. However, cells co-exposed to both carbon black and Fe₂O₃ particles showed up to a two-fold increase in protein oxidation relative to the control. In addition, co-exposure induced significant lipid peroxidation, although exposure to either particle type alone did not. No significant difference in cellular iron uptake was found between single exposure and co-exposure, when the Fe₂O₃ dosing concentration was the same in each case. In the cell-free assay, significant reduction of Fe³⁺ ions by carbon black nanoparticle was found within 2 hour, and it progressed up to 24 hours. At 24 hours, the carbon black nanoparticles showed a reductive capacity of 0.009 g/g, defined as the mass ratio of reduced Fe³⁺ to carbon black.

Conclusion

Co-exposure to carbon black and Fe₂O₃ particles causes a synergistic oxidative effect that is significantly greater than the additive effects of exposures to either particle type alone. The intracellular redox reaction between carbon black and Fe³⁺ is likely responsible for the synergistic oxidative effect. Therefore elemental carbon particles and fibres should be considered as potential reducing agents rather than inert materials in toxicology studies. Acidified cell organelles such as the lysosomes probably play a critical role in the solubilization of Fe₂O₃. Further research is necessary to better understand the mechanisms.

Ovalbumin-Induced Airway Inflammation and Fibrosis in Mice Also Exposed to Ultrafine Particles

A murine model of allergen-induced airway inflammation was used to examine the effects of exposure to ultrafine particles (PM(2.5)) on airway inflammation and remodeling. Lung inflammation was measured by quantitative differential evaluation of lung lavage cells. Alterations in lung structure (airway remodeling and fibrosis) were evaluated by quantitative biochemical analysis of microdissected airways and by histological evaluation of stained lung sections. The same total number of cells was observed in lavage fluid from animals exposed for 4 wk to ovalbumin alone or to ovalbumin for 4 wk immediately before or after 6 exposures over a period of 2 wk to 235 ug/m(3) of PM(2.5). Mice exposed to ovalbumin for 6 wk with concurrent exposure to PM(2.5) during wk 5-6 had a significant decrease in the total number of cells recovered by lavage as compared with the group exposed to ovalbumin alone. There were no significant differences in the cell differential counts in the lavage fluid from mice exposed to ovalbumin alone as compared with values from mice exposed to ovalbumin and PM(2.5) under the protocols studied. Airway structural changes (remodeling) were examined by three different quantitative methods. None of the groups exposed to ovalbumin and PM had a significant increase in airway collagen content evaluated biochemically (i.e., total airway collagen) as compared to the matched groups of mice exposed to ovalbumin alone. Airway collagen content evaluated histologically by sirius red staining showed significant increases in all of the animals exposed to ovalbumin, with or without PM, and no apparent difference between the ovalbumin group and mice exposed to PM with ovalbumin. The findings were consistent with an additive, or less than additive, response of mice to exposure to PM and ovalbumin. Air or PM exposure alone for 2 wk did not result in observable goblet cells in the airways, while mice exposed to ovalbumin aerosol alone for 4 wk had about 20-25% goblet cells in their conducting airways. Sequential exposure to ovalbumin and PM (or vice versa) caused significant increases in goblet cells (to about 35% of total cells) in the conducting airways of the exposed mice. We conclude that when mice with allergen-induced airway inflammation induced by ovalbumin are also exposed to PM(2.5), the lung inflammatory response and airway remodeling may be modified, but that this altered response is dependent upon the sequence of exposure and the duration of exposure to ovalbumin aerosol. At the concentrations of PM tested, we did not see changes in airway fibrosis or airway reactivity for animals exposed to ovalbumin and PM(2.5) as compared with animals exposed only to ovalbumin aerosol. However, goblet-cell hyperplasia was significantly increased in mice exposed concurrently to ovalbumin and PM(2.5) as compared with mice exposed to ovalbumin alone.

A novel exposure system for the efficient and controlled deposition of aerosol particles onto cell cultures

Epidemiologic studies have shown correlations between morbidity and particles < or = 2.5 microm generated from pollution processes and manufactured nanoparticles. Thereby nanoparticles seem to play a specific role. The interaction of particles with the lung, the main pathway of undesired particle uptake, is poorly understood. In most studies investigating these interactions in vitro, particle deposition differs greatly from the in vivo situation, causing controversial results. We present a nanoparticle deposition chamber to expose lung cells mimicking closely the particle deposition conditions in the lung. In this new deposition chamber, particles are deposited very efficiently, reproducibly, and uniformly onto the cell culture, a key aspect if cell responses are quantified in respect to the deposited particle number. In situ analyses of the lung cells, e.g., the ciliary beat frequency, indicative of the defense capability of the cells, are complemented by off-line biochemical, physiological, and morphological cell analyses.

NF-kappaB inhibition is involved in tobacco smoke-induced apoptosis in the lungs of rats

Apoptosis is a vital mechanism for the regulation of cell turnover and plays a critical role in tissue homeostasis and development of many disease processes. Previous studies have demonstrated the apoptotic effect of tobacco smoke; however, the molecular mechanisms by which tobacco smoke triggers apoptosis remain unclear. In the present study we investigated the effects of tobacco smoke on the induction of apoptosis in the lungs of rats and modulation of nuclear factor-kappa B (NF-kappaB) in this process. Exposure of rats to 80 mg/m(3) tobacco smoke significantly induced apoptosis in the lungs. Tobacco smoke resulted in inhibition of NF-kappaB activity, noted by suppression of inhibitor of kappaB (IkappaB) kinase (IKK), accumulation of IkappaBalpha, decrease of NF-kappaB DNA binding activity, and downregulation of NF-kappaB-dependent anti-apoptotic proteins, including Bcl-2, Bcl-xl, and inhibitors of apoptosis. Initiator caspases for the death receptor pathway (caspase 8) and the mitochondrial pathway (caspase 9) as well as effector caspase 3 were activated following tobacco smoke exposure. Tobacco smoke exposure did not alter the levels of p53 and Bax proteins. These findings suggest the role of NF-kappaB pathway in tobacco smoke-induced apoptosis.